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Sample records for samoan lavas evidence

  1. The unusual Samoan hotspot: A "hotspot highway" juxtaposed with a trench

    Science.gov (United States)

    Jackson, M. G.; Konter, J. G.; Koppers, A. A.

    2011-12-01

    Oceanic hotspots are fed by (relatively) stationary, upwelling mantle plumes that melt beneath mobile tectonic plates. This mechanism results in the generation of a linear chain of volcanoes exhibiting a clear age progression: the islands and seamounts should be increasingly older with increasing distance from the inferred location of the mantle plume. Located in the southwest Pacific, the Cook-Austral volcanic islands and seamounts were long thought to lack a clear age progression, and it has been argued that the Cook-Austral volcanic chain is an example of a hotspot not fed by a mantle plume. However, work by Chauvel et al (1997) showed that the Cook-Austral volcanoes have been generated by three distinct, co-linear mantle plumes spaced by ~1000 km, resulting in 3 overlapping hotspot tracks. Critically, the volcanoes generated by each hotspot exhibit a clear age progression that emerges from its respective plume. Using plate motion models, the reconstructed tracks of the three Cook-Austral hotspots backtrack through the region of the Pacific plate now occupied by the Samoan hotspot between 10 and 40 Ma (Konter et al., 2008). Owing to the unusual number of hotspots (Samoa is the fourth) that have been hosted in the region, we refer to this corridor of the Pacific plate as the "hotspot highway." The Samoan hotspot is burning through and thus crosscutting the trails of the older Cook-Austral hotspots. Consistent with this hypothesis, Jackson et al. (2010) reported volcanic features from the Cook-Austral hotspots in the Samoan region, including three seamounts and one atoll with geochemical affinities to the Cook-Austral hotspot. The Pacific lithosphere was likely "preconditioned" (metasomatized) by the three Cook-Australs hotspots before the arrival of the Samoan plume into the region, yet geochemical signatures associated with the Cook-Austral hotspot pedigrees are not evident in Samoan shield lavas. However, Samoan rejuvenated lavas exhibit a clear EMI (enriched

  2. Remote sensing evidence of lava-ground ice interactions associated with the Lost Jim Lava Flow, Seward Peninsula, Alaska

    Science.gov (United States)

    Marcucci, Emma C.; Hamilton, Christopher W.; Herrick, Robert R.

    2017-12-01

    Thermokarst terrains develop when ice-bearing permafrost melts and causes the overlying surface to subside or collapse. This process occurs widely throughout Arctic regions due to environmental and climatological factors, but can also be induced by localized melting of ground ice by active lava flows. The Lost Jim Lava Flow (LJLF) on the Seward Peninsula of Alaska provides evidence of former lava-ground ice interactions. Associated geomorphic features, on the scale of meters to tens of meters, were identified using satellite orthoimages and stereo-derived digital terrain models. The flow exhibits positive- and mixed-relief features, including tumuli ( N = 26) and shatter rings ( N = 4), as well as negative-relief features, such as lava tube skylights ( N = 100) and irregularly shaped topographic depressions ( N = 1188) that are interpreted to include lava-rise pits and lava-induced thermokarst terrain. Along the margins of the flow, there are also clusters of small peripheral pits that may be the products of meltwater or steam escape. On Mars, we observed morphologically similar pits near lava flow margins in northeastern Elysium Planitia, which suggests a common formation mechanism. Investigating the LJLF may therefore help to elucidate processes of lava-ground ice interaction on both Earth and Mars.

  3. Emplacement history and inflation evidence of a long basaltic lava flow located in Southern Payenia Volcanic Province, Argentina

    Science.gov (United States)

    Bernardi, Mauro I.; Bertotto, Gustavo W.; Jalowitzki, Tiago L. R.; Orihashi, Yuji; Ponce, Alexis D.

    2015-02-01

    The El Corcovo lava flow, from the Huanul shield volcano in the southern Mendoza province (central-western Argentina) traveled a distance of 70 km and covered a minimum area of ~ 415 km2. The flow emplacement was controlled both by extrinsic (e.g., topography) and intrinsic (e.g., lava supply rate, lava physicochemical characteristics) factors. The distal portion of the lava flow reached the Colorado River Valley, in La Pampa Province, where it spread and then was confined by earlier river channels. Cross-sections through the flow surveyed at several localities show two vesicular layers surrounding a dense central section, where vesicles are absent or clustered in sheet-shaped and cylindrical-shaped structures. Lavas of the El Corcovo flow are alkaline basalts with low values of viscosity. The morphological and structural characteristics of the flow and the presence of landforms associated with lava accumulation are the evidence of inflation. This process involved the formation of a tabular sheet flow up to 4 m of thick with a large areal extent in the proximal sectors, while at terminal sectors frontal lobes reached inflation values up to 10 m. The numerous swelling structures present at these portions of the flow suggest the movement of lava in lava tubes. We propose that this aspect and the low viscosity of the lava allowed the flow travel to a great distance on a gentle slope relief.

  4. Sexuality in Samoan art forms.

    Science.gov (United States)

    Moyle, R M

    1975-05-01

    This article explores the manifestations of sexuality in Samona as they are revealed through songs, poetry, dance, gestures, verbal expressions, stories, and games. For each of these art forms, texts, and translations of original material are presented, as an aid to discerning the uses and functions of sexuality as they are applied by Samoans for Samoans; to this end, formulalized joking of various types is seen as the medium through which the humorous element of sexuality is expressed. Elsewhere, sexuality functions to achieve and sustain individual attention. The explicitly sexuality functions to achieve and sustain individual attention. The explicitly sexual references in duneral and marriage songs, on the other hand, constitute affirmations of social values, incorporated in long-established rites. In what is tantamount to artistic license, performance of song, poetry, and dance containing sexual elements or references that would be prohibited in other contexts is constituted as acceptable behavior. In marked contrast to nineteenth-century writings, and the opinions of the popular press, sexuality in Samoa is far from free in its modes of expression, but rather adheres to traditional formalized patterns which determine its occasions, participants, and verbal and kinetic limits. Although not indispensable as a means of personal expression, it generally provides additional opportunities for the creative and aggressive individual to demonstarate his artistic talents and therby contribute to his own social elevation. As an element of verbalized group sentiment, it is a positive assertion of Samoan values, astatement of social solidarity.

  5. Evidence for geomagnetic excursions recorded in Brunhes and Matuyama Chron lavas from the trans-Mexican volcanic belt

    Science.gov (United States)

    Michalk, Daniel M.; BöHnel, Harald N.; Nowaczyk, Norbert R.; AguíRre-Diaz, Gerardo J.; López-MartíNez, Margarita; Ownby, Steven; Negendank, JöRg F. W.

    2013-06-01

    This study presents paleomagnetic data from 59 independent lava flows from the trans-Mexican volcanic belt (TMVB) with ages from 6.4 Ma to recent, 52 being younger than 1 Ma, and 11 new 40Ar/39Ar age determinations. Most remanence carriers are Ti-poor titanomagnetite of pseudosingle-domain magnetic structure, nine lavas contain small amounts of titanomaghemite, and four lavas additional (titano-) hematite. Paleosecular variation of lava flows younger than 1.7 Ma is consistent with latitude-dependent Model G and also in agreement with other Pleistocene paleomagnetic data from the TMVB. The directional record of Brunhes and Matuyama Chrons lavas was correlated to the geomagnetic polarity timescale and there is evidence for at least four geomagnetic excursions. One lava flow dated at 592 ± 20 ka has a fully reversed paleodirection and most likely erupted during the Big Lost excursion. Another fully reversed flow, dated at 671 ± 12 ka, gives new volcanic evidence for the Delta/Stage 17 excursion. This excursion is supported by a reversed intermediate direction of another flow from a different volcanic field but of very close age of 673 ± 10 ka. From the Matuyama age lavas, one flow with normal polarity magnetization, dated at 949 ± 37 ka, could either be related to the Kamikatsura or the Santa Rosa excursion and a normal polarity flow, dated at 1628 ± 56 ka, could have been emplaced during the Gilsa excursion. The results presented here confirm in one case but disagree in four cases with results presented in two previous studies of the same lava flows and interpreted as geomagnetic excursions.

  6. Asthenospheric outflow from the shrinking Philippine Sea Plate: Evidence from Hf-Nd isotopes of southern Mariana lavas

    Science.gov (United States)

    Ribeiro, Julia M.; Stern, Robert J.; Martinez, Fernando; Woodhead, Jon; Chen, Min; Ohara, Yasuhiko

    2017-11-01

    At subduction zones, sinking of the downgoing lithosphere is thought to enable a return flow of asthenospheric mantle around the slab edges, so that the asthenosphere from underneath the slab invades the ambient mantle flowing underneath the volcanic arc and the backarc basin. For instance at the northern end of the Lau Basin, trench retreat and slab rollback enable toroidal return flow of Samoan mantle beneath a transform margin to provide a supply of fresh, undepleted Indian mantle that feeds the backarc spreading center. Questions, however, arise about the sense of mantle flow when plate kinematics predict that the trench is advancing, as seen in the Mariana convergent margin. Does the mantle flow in or does it escape outward through slab tears or gaps? Here, we address the origin and sense of asthenospheric mantle flow supplying the southern Mariana convergent margin, a region of strong extension occurring above the subducting Pacific plate. Does the asthenosphere flow northward, from underneath the Pacific plate and Caroline hotspot through a slab tear or gap, or does it flow outward from the Mariana Trough, which possesses a characteristic Indian Ocean isotopic signature? To address these questions, we integrate geodetic data along with new Hf-Nd isotopic data for fresh basaltic lavas from three tectonic provinces in the southernmost Marianas: the Fina Nagu volcanic complex, the Malaguana-Gadao backarc spreading ridge and the SE Mariana forearc rift. Our results indicate that Indian mantle flows outward and likely escapes through slab tears or gaps to accommodate shrinking of the Philippine Sea plate. We thus predict that asthenospheric flow around the Pacific slab at the southern Mariana Trench is opposite to that predicted by most subduction-driven mantle flow models.

  7. Evidence for Amazonian highly viscous lavas in the southern highlands on Mars

    Czech Academy of Sciences Publication Activity Database

    Brož, Petr; Hauber, E.; Platz, T.; Balme, M.

    2015-01-01

    Roč. 415, 1 April (2015), s. 200-212 ISSN 0012-821X Institutional support: RVO:67985530 Keywords : Mars surface * volcanology * lava dome Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 4.326, year: 2015

  8. Exclusives, equatives and prosodic phrases in Samoan

    Directory of Open Access Journals (Sweden)

    Sasha Calhoun

    2017-02-01

    Full Text Available This paper investigates the functions of prosodic phrasing in the Austronesian VSO language Samoan. Two types of sentences are investigated, exclusives (involving the particle 'na’o' ‘only’ and equatives. Two complementary methodologies were used, a production study and an acceptability judgment study, to examine the prosodic realisation and relative naturalness of different word orderings of the two sentence types. The particle 'na’o' has an unusual distribution: preceding the initial constituent, be it the verb or a fronted noun phrase; or following the verb, but only modifying the absolutive (object. It was found that post-verbal absolutives modified by 'na’o' are usually not preceded by a phrase boundary, unlike unmodified absolutives which are consistently preceded by a high phrase tone (H- (cf. Yu 2009. Equatives in Samoan involve clauses which are the juxtaposition of two noun phrases, one the rheme (focus and the other the theme (topic. It was found that rhemes are usually followed by a phrase break, while for themes this is optional. Rheme-theme order was strongly preferred to theme-rheme order. These findings are argued to show a close relationship between information structure, constituent ordering and prosodic phrasing in Samoan. The preferred order of constituents in Samoan is rheme-theme, with a high phrase tone marking the end of the rheme. The absolutive argument is strongly preferred to be at the start of the theme. This article is part of theSpecial Collection: Prosody and constituent structure

  9. 182W evidence from flood basalt lavas for the long-term survival of primordial mantle

    Science.gov (United States)

    Rizo Garza, H. L.; Walker, R. J.; Carlson, R.; Horan, M. F.; Mukhopadhyay, S.; Francis, D.; Jackson, M. G.

    2016-12-01

    How much of the chemical heterogeneity present in mantle today dates to processes that occurred during Earth's planetary formation stage remains an unanswered question. Geochemical observations obtained from short-lived radiogenic isotope systems, however, provide important insights. Tungsten isotope data for flood basalt lavas from two large igneous provinces, the North Atlantic Igneous Province ( 60 Ma) and the Ontong Java Plateau ( 120 Ma), show well resolved 182W excesses, compared with terrestrial standards that are presumed to be representative of the present bulk mantle. These W isotope results, thus, indicate that one or more mantle domains formed very early in Earth history and have been preserved well into the Phanerozoic eon. The flood basalts from Baffin Bay contain among the highest 3He/4He ratios ever measured, as well as Pb and 143Nd isotopic compositions, and D/H ratios consistent with a chemically primitive, un-degassed mantle source. Ontong Java is the Earth's largest known volcanic province and shares chemical and isotopic similarities with the Baffin Bay lavas, indicative of a similarly primitive mantle source. The 182W-enriched nature of the mantle sources of rocks from both locations indicates that their primitive characteristics were likely isolated in a deep mantle reservoir within the first 50 Ma of Solar System history. The correlation between large low seismic shear velocity provinces (LLSVPs) and the distribution of reconstructed eruption sites of these large igneous provinces makes the LLSVPs possible candidate domains for the required primitive and un-degassed reservoirs.

  10. Evidence for a heterogeneous astenosphere from intra-transform and seamount lavas

    Science.gov (United States)

    Saal, A.; Nagle, A.; Myers, C.; Hauri, E.; Pickle, R.; Forsyth, D.; Niu, Y.

    2008-12-01

    The asthenosphere is a mechanically weak region in the shallow mantle (between 100 to 300 km) underneath the lithosphere. Its unique physical properties (location, depth, viscosity, seismic velocity, anisotropy, attenuation, electrical conductivity) have been attributed to either mineral properties at relevant temperatures and pressures or to the presence of melt and/or water. To understand the processes controlling the physical properties of the asthenosphere we rely on geochemical studies of primitive basalts from the Mid-Ocean Ridges (MORB). In this regard, establishing the composition (especially volatile content) of the mantle source of MORB is a fundamental step in our understanding of this mechanically weak region of the upper mantle. However, first it is important to determine to what extent the geochemical variations in axial MORB do represent a homogeneous mantle composition and variations in the physical conditions of magma generation and transport (i.e., depth and extent of melting and melt migration); or alternatively, they are inherited from mixing processes during the aggregation of melts originated from an heterogeneous mantle beneath the mid-ocean ridge. The composition of melts within a ridge segment can be obscured by along-axis transport of magma within the crust in dikes or long-lived magma chambers. To address these issues, seamount and intra-transform lavas provide a better opportunity to deconstruct the source heterogeneity beneath mid-ocean ridges than axial lavas. Although they share a common mantle source with axial MORB, they represent smaller melt volumes tapped locally from areas lacking steady-state magma chambers and along-axis transport. Therefore, lavas from intra-transform faults and seamounts represent pre-aggregated melts experiencing relatively less mixing and differentiation, and their compositions provide insight into the heterogeneity of the asthenosphere Basalts from Quebrada/Discovery/Gofar (QDG) fracture zone system and

  11. New field evidence for silicic ignimbrites and proximal lavas and their distribution in the Parana Basin, Brazil

    Science.gov (United States)

    Tramontano, S.; Harmon, L. J.; Gravley, D. M.; Gualda, G. A. R.

    2014-12-01

    Silicic ignimbrites and lavas are sometimes very difficult to distinguish from one another in the field. Their accurate identification provides the basis for a better understanding of the origin of these deposits, including processes related to magma extraction, fragmentation and eruption style. We are studying the silicic volcanics in the Paraná Rift Basin in southern Brazil (the ~130 to 135 Ma Palmas member of the Serra Geral Formation), the counterpart to the Etendeka silicic volcanics in Africa. We present new field evidence for the identification of tabular-shaped ignimbrite-like packages, which contrast with dome-shaped proximal viscous lavas and domes. The tabular-shaped packages are highly welded and devitrified, but primary feldspar and pyroxene crystals can still be identified in outcrops. Flow/cooling unit boundaries can be seen at outcrop scale as well as at the kilometer scale where successive flat-topped terraces have been cut into the volcanic landscape. These packages bear conspicuous swarms of vesicle-poor black lens-shaped features set in a light colored matrix. The lenses range in their aspect ratio (2D height vs. length) and can be > 2 m long. Horizontal jointing is superimposed on the black lens-bearing outcrops and their spacing appears to coincide with the aspect ratio of the lenses, i.e. thinner lenses have a narrower joint spacing. Locally wider lenses grade down into completely stretched and/or flattened lenses that resemble conventional flow banding. We interpret these tabular packages as ignimbrites and the vesicle-poor black lenses as juvenile magma blobs (distinct from typical pumice or fiamme). A notably different flow-banded, irregularly deformed, and sometimes obsidian-bearing lithology appears in a number of locations. It supports topography characterized by rolling hills that contrasts markedly with the tilted plateaus supported by ignimbrites. The difference in morphology between ignimbrites and lavas is most readily observed in

  12. Evidence from lava flows for complex polarity transitions: The new composite Steens Mountain reversal record

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    Jarboe, Nicholas A.; Coe, Robert S.; Glen, Jonathan M. G.

    2011-01-01

    Geomagnetic polarity transitions may be significantly more complex than are currently depicted in many sedimentary and lava-flow records. By splicing together paleomagnetic results from earlier studies at Steens Mountain with those from three newly studied sections of Oregon Plateau flood basalts at Catlow Peak and Poker Jim Ridge 70–90 km to the southeast and west, respectively, we provide support for this interpretation with the most detailed account of a magnetic field reversal yet observed in volcanic rocks. Forty-five new distinguishable transitional (T) directions together with 30 earlier ones reveal a much more complex and detailed record of the 16.7 Ma reversed (R)-to-normal (N) polarity transition that marks the end of Chron C5Cr. Compared to the earlier R-T-N-T-N reversal record, the new record can be described as R-T-N-T-N-T-R-T-N. The composite record confirms earlier features, adds new west and up directions and an entire large N-T-R-T segment to the path, and fills in directions on the path between earlier directional jumps. Persistent virtual geomagnetic pole (VGP) clusters and separate VGPs have a preference for previously described longitudinal bands from transition study compilations, which suggests the presence of features at the core–mantle boundary that influence the flow of core fluid and distribution of magnetic flux. Overall the record is consistent with the generalization that VGP paths vary greatly from reversal to reversal and depend on the location of the observer. Rates of secular variation confirm that the flows comprising these sections were erupted rapidly, with maximum rates estimated to be 85–120 m ka−1 at Catlow and 130–195 m ka−1 at Poker Jim South. Paleomagnetic poles from other studies are combined with 32 non-transitional poles found here to give a clockwise rotation of the Oregon Plateau of 11.4°± 5.6° with respect to the younger Columbia River Basalt Group flows to the north and 14.5°± 4.6° with respect

  13. Translating questions for use with Samoan adults: lessons learned.

    Science.gov (United States)

    Siaki, Leilani A

    2011-04-01

    The purpose of this article was to present the process of translating questions about perceived risk for diabetes into Samoan and describe important cultural adaptations to the modified Brislin's translation model for cross-cultural research. With the assistance of a culture broker and several Samoan translators, 14 questions were translated into the Samoan language. Cultural adaptations included using a group approach, working with a matai, and following protocols such as fa'alavelave. Questions were back-translated and then pilot tested. Results from the pilot testing supported the use of these cultural modifications in the translation model.

  14. Estimating Language Skills in Samoan- and Tongan-Speaking Children Growing up in New Zealand

    Science.gov (United States)

    Reese, Elaine; Ballard, Elaine; Taumoepeau, Mele; Taumoefolau, Melenaite; Morton, Susan B.; Grant, Cameron; Atatoa-Carr, Polly; McNaughton, Stuart; Schmidt, Johanna; Mohal, Jatender; Perese, Lana

    2015-01-01

    The MacArthur-Bates Communicative Development Inventory (short form) was adapted for Samoan and Tongan speakers in New Zealand. The adaptation process drew upon language samples from Samoan and Tongan parent-child dyads with 20- and 26-month-old children and adult informants. The resulting 100-word language inventories in Samoan and Tongan, plus a…

  15. The phonological skills of Samoan speaking 4-year-olds.

    Science.gov (United States)

    Ballard, Elaine; Farao, Sharon

    2008-01-01

    To date there has been little research on the typical developmental patterns for children speaking Samoan. The research outlined in this paper serves to fill this gap by reporting on the phonological development of Samoan speaking children growing up in the English dominant language environment of Auckland New Zealand. In this study 20 children aged between 4;0 and 4;11 were assessed using a picture naming task that probed their knowledge of the Samoan phonemic inventory. The findings presented here give an indication of what children in their fifth year have as speech sounds in their phonetic inventory and the types of errors that they may still produce. These results demonstrate the similarities and differences that Samoan phonological development shares with other languages. In particular the differences that seem "atypical" when compared with studies on English are discussed. It is tentatively concluded that these differences may well be typical for Samoan speech acquisition given language specific factors and the bilingual context in which these children are growing up.

  16. The future of Western Samoan migration to New Zealand.

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    Va'a, L F

    1992-01-01

    "The history of Samoan migration to New Zealand, a demographic profile of the migrants, and the future of such migration are discussed. Migration became a serious phenomenon after independence in 1962, with primarily young, unskilled workers moving to take up jobs in the agricultural and service sectors. Remaining essentially unchanged since 1962, New Zealand's immigration policy gives preferential treatment to Western Samoans and recognizes their valuable labor contribution. The future of migration to New Zealand is discussed in the context of the costs and benefits to Western Samoa.... The author argues that emigration has been beneficial rather than deleterious to Western Samoa's development...." Data are from official sources. excerpt

  17. Acculturation and Dating Violence Victimization among Filipino and Samoan Youths

    Science.gov (United States)

    Chung-Do, Jane J.; Goebert, Deborah A.

    2009-01-01

    Dating violence victimization is an important public health issue. Recent studies on minority youths have found higher risks of dating violence victimization compared to White youths. This study examined the influence of acculturation components on youths' experiences of dating violence by utilizing data from a survey of 193 Samoan and Filipino…

  18. Evidence for fullerenes in solid bitumen from pillow lavas of Proterozoic age from Mítov (Bohemian Massif, Czech Republic)

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    Jehlička, Jan; Svatoš, Aleš; Frank, Ota; Uhlík, Filip

    2003-04-01

    Andesitic pillow lavas containing biogenic, solid bitumen (SB) are a constituent of a Neoproterozoic volcanosedimentary sequence (Teplá-Barrandian unit, Bohemian Massif) in the Mítov area of the Czech Republic. A black shale formation that is crosscut by these andesitic basalts is 565 Ma old. Carbon disulfide extracts of two powdered samples of SB contain 0.2 and 0.3 ppm of C 60, respectively, as determined by high-pressure liquid chromatography. The peak assignment based on retention time is fully supported by high-resolution electron ionization mass spectrometry (EI-MS). No C 70 was detected, nor was C 60 found in two other SB samples from this locality. Other investigated carbonaceous samples from Bohemia (coals and anthracites of Upper Paleozoic age and anthraxolite, graphitoids, and graphite of Upper Proterozoic age) did not contain fullerenes at concentrations above the detection limit of 0.01 ppm. The absence of C 60 in these samples was confirmed by EI-MS. The proposed mechanism of fullerene formation involves a primary algal phase, generation of a hydrocarbonaceous mixture in the course of thermal evolution of the sedimentary series, and their high-temperature transformation related to the extrusion of basalt. An important feature for fullerene conservation was the enclosure of fullerenes in SB with a structure similar to glasslike carbon, where the fullerene was protected against oxidation.

  19. Volcanic Glasses as Habitat for Microfossils: Evidence from the Early Paleoproterozoic Pillow Lavas of Karelia and their Modern Analogues in the Mid-Atlantic Ridge

    Science.gov (United States)

    Adtafieva, M. M.; Rozanov, A. Yu; Sharkov, E. V.; Chistyakov, A. V.; Bogina, M. M.; Hoover, R. B.

    2009-01-01

    Microbial complexes were identified in the volcanic glasses from the ancient (2.4-Ga-old basaltic pillow-lavas of Karelia) and modern (pillow lavas of Mid-Atlantic ridge) volcanic rocks. It was shown that that their microbial colonization is likely to occur by the same mechanism. Thus, well preserved pillow lavas, which occupy a spacious fields in the Archean and Early Paleoproterozoic greenstone belts, are promising object for search of the earliest traces of life on Earth.

  20. Inverse steptoes in Las Bombas volcano, as an evidence of explosive volcanism in a solidified lava flow field. Southern Mendoza-Argentina

    Science.gov (United States)

    Risso, Corina; Prezzi, Claudia; Orgeira, María Julia; Nullo, Francisco; Margonari, Liliana; Németh, Karoly

    2015-11-01

    Here we describe the unusual genesis of steptoes in Las Bombas volcano- Llancanelo Volcanic Field (LVF) (Pliocene - Quaternary), Mendoza, Argentina. Typically, a steptoe forms when a lava flow envelops a hill, creating a well-defined stratigraphic relationship between the older hill and the younger lava flow. In the Llancanelo Volcanic Field, we find steptoes formed with an apparent normal stratigraphic relationship but an inverse age-relationship. Eroded remnants of scoria cones occur in ;circular depressions; in the lava field. To express the inverse age-relationship between flow fields and depression-filled cones here we define this landforms as inverse steptoes. Magnetometric analysis supports this inverse age relationship, indicating reverse dipolar magnetic anomalies in the lava field and normal dipolar magnetization in the scoria cones (e.g. La Bombas). Negative Bouguer anomalies calculated for Las Bombas further support the interpretation that the scoria cones formed by secondary fracturing on already solidified basaltic lava flows. Advanced erosion and mass movements in the inner edge of the depressions created a perfectly excavated circular depression enhancing the ;crater-like; architecture of the preserved landforms. Given the unusual genesis of the steptoes in LVF, we prefer the term inverse steptoe for these landforms. The term steptoe is a geomorphological name that has genetic implications, indicating an older hill and a younger lava flow. Here the relationship is reversed.

  1. Gas exsolution and bubbles nucleation from the 1669 lava flow of Mount Etna (Italy): evidences from phase-contrast synchrotron X-ray microtomography

    Science.gov (United States)

    Lanzafame, Gabriele; Ferlito, Carmelo; Mancini, Lucia

    2017-04-01

    Bubbles are usually present in lavas, often showing an increase in their size and number from bottom to the top of vertical profile of the flows. Their presence is commonly interpreted as the final phase of the degassing processes starting and massively occurring at depth, before the eruption. In this work we present the results of a detailed study of size, shape and volumetric distribution of bubbles in lavas from the 1669 eruption of Mount Etna (Italy), one of the most voluminous and destructive historic events of this volcano. The lava field produced during this event extends up to 18 km from the craters, and the massive presence of bubbles in lavas sampled many kilometres away from the emission point is in contrast with the models predicting their almost total exsolution from the magma before the eruption, at depth of several kilometres beneath the volcano edifice. Sampling of the 1669 lava field has been performed along the longitudinal profile of the field at increasing distance from the vent. Collected rocks have been analysed by X-ray fluorescence and phase-contrast synchrotron X-ray computed microtomography in order to extract three-dimensional (3D) qualitative and quantitative information on the bubbles network. The use of synchrotron light permitted to investigate small portions of the samples at high spatial and contrast resolution and allowed us to obtain the 3D morphology and distribution of the micro-bubbles present in the lava, avoiding the limitations of the traditional two-dimensional analysis on thin sections. Results indicate that bubbles in lavas are present in various abundance, constituting up to 18% of the rocks volume, and are randomly distributed, with no regards for the distance from the vent. Their casual abundance, morphological characteristics and spatial distribution indicate large nucleation from syn- to post-eruptive stage, during the lava flowing and probably after it halted its run. These observations are in contrast with the

  2. Ice-Confined Basaltic Lava Flows: Review and Discussion

    Science.gov (United States)

    Skilling, I.; Edwards, B. R.

    2012-12-01

    Basaltic lavas that are interpreted as having been emplaced in subglacial or ice-confined subaerial settings are known from several localities in Iceland, British Columbia and Antarctica. At least four different types of observations have been used to date to identify emplacement of basaltic lavas in an ice-rich environment: i) gross flow morphology, ii) surface structures, iii) evidence for ice-confined water during emplacement, and iv) lava fracture patterns. Five types of ice-confined lava are identified: sheets, lobes, mounds, linear ridges and sinuous ridges. While the appearance of lavas is controlled by the same factors as in the submarine environment, such as the geometry and configuration of vents and lava tubes, flow rheology and rates, and underlying topography, the presence of ice can lead to distinct features that are specific to the ice-confined setting. Other types have very similar or identical equivalents in submarine environment, albeit with some oversteepening/ice contact surfaces. Ice-confined lavas can form as (1) subaerial or subaqueous lavas emplaced against ice open to the air, (2) subaqueous lavas emplaced into pre-existing sub-ice drainage networks, and (3) subaqueous lavas emplaced into ponded water beneath ice. Their surface structures reflect the relationship between rates of lava flow emplacement at the site of ice-water-lava contact, ice melting and water drainage. Variations in local lava flow rates could be due to lava cooling, constriction, inflation, tube development, ice melting, ice collapse, lava collapse, changes in eruption rate etc. Episodes of higher lava flow rate would favour direct ice contact and plastic compression against the ice, generating oversteepened and/or overthickened chilled margins, cavities in the lava formed by melting of enveloped ice blocks (cryolith cavities) and structures such as flattened pillows and lava clasts embedded into the glassy margins. Melting back of the confining ice generates space to

  3. Hawaii Volcanism: Lava Forms

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Over the last several million years the Hawaiian Islands have been built of successive lava flows. They are the most recent additions in a long line of volcanoes...

  4. Samoan Philosophy of Nursing: a basis for culturally proficient care and policy.

    Science.gov (United States)

    Enoka, I S; Petrini, M A; Turale, S

    2014-09-01

    To explore nurses' perspectives about the Samoan Philosophy of Nursing, and determine its feasibility for nursing care of Samoans internationally. This philosophy is the conceptual cultural framework for nursing law, practice, education and research in Samoa, and was developed by Samoan nurses who recognized the need for guidance to deliver quality, culturally competent and proficient health care. A mixed method study, employing a questionnaire and ethnographic methods. The Samoan Philosophy of Nursing Questionnaire sought demographic data and aspects about the philosophy from 95 registered nurse clinicians, administrators and educators throughout Samoa during 2012. Descriptive statistics were used for data analysis. Additionally, 19 focus groups (5-6 participants each) and 19 in-depth interviews were held to further explore these aspects, as well as participant observations. Descriptive statistics were used to analyse quantitative data, and Spradley's ethnographic method was adopted for analysing the qualitative data. Of 95 questionnaires analysed, 70% of participants reported using the philosophy all the time, and 30% most of the time. They placed a high satisfaction rate, value and importance on this philosophy. From the ethnography, six major themes emerged: valuable framework of learning; conceptual framework for holistic assessment; benchmark for regulating and monitoring practice improving interaction and culturally proficient practice; potential use for Samoans overseas; and maintaining quality health and the dignity of people. This first-time study evaluated the Samoan Philosophy of Nursing and adds to nursing knowledge. Findings confirmed its usefulness as a culturally based conceptual framework to facilitate, regulate and monitor education, research and practice for sustainable health outcomes in Samoa, and for Samoans living abroad. It is important that Samoans living abroad receive culturally proficient care, but this requires the support of

  5. Palaeosecular variation recorded by 9 ka to 2.5-Ma-old lavas from Martinique Island: new evidence for the La Palma aborted reversal ˜617 ka ago

    Science.gov (United States)

    Tanty, Cyrielle; Carlut, Julie; Valet, Jean-Pierre; Germa, Aurélie

    2015-02-01

    Fifteen sites of lava flows from Martinique Island (FWI) have been selected to document the geomagnetic field in the Caribbean area over the past 2.5 Ma and further constrain the time-averaged field during this period. Identical characteristic directions were isolated using both AF and thermal stepwise demagnetization techniques in all flows. Nine mean-site directions have a normal polarity, while three others are reversed. The mean geomagnetic pole position obtained after reducing all directions to the same polarity is indistinguishable from the present north geographic pole. The dispersion is at least 8° larger than the values derived from the time-averaged field models and remains unexplained otherwise than resulting from the relatively small number of directions. The other three flows are characterized by large deviations from the expected north-south direction. One lava flow dated at 1.69 Ma (±0.02 Ma) is likely associated with a transitional field during the Gilsà subchron. The lava flow dated at 770 ka (±11 ka) coincides with the age of the Brunhes-Matuyama geomagnetic reversal and is also coeval with another intermediate flow of the same age found at Guadeloupe Island. The 617 ka (±52 ka) old unit is characterized by reversed directions that are evidently not related to the last reversal, but with other reversed polarity and transitional lava flows of the same age recorded, respectively at Mexico and La Palma island. We infer that the presence of reversed directions with the same age at distinct localities confirms that a short episode of reversed polarity has occurred during this period.

  6. Volcanic facies analysis of a subaqueous basalt lava-flow complex at Hruškovec, NW Croatia — Evidence of advanced rifting in the Tethyan domain

    Science.gov (United States)

    Palinkaš, Ladislav A.; Bermanec, Vladimir; Borojević Šoštarić, Sibila; Kolar-Jurkovšek, Tea; Palinkaš, Sabina Strmić; Molnar, Ferenc; Kniewald, Goran

    2008-12-01

    The Hru\\vskovec quarry of basaltoid rocks is situated on the northwestern slopes of Mt. Kalnik, within the Zagorje-Mid-Transdanubian zone, a part of the North-western Dinarides. The basaltoids are inter-bedded with radiolarites of the Middle and Upper Triassic age (Langobardian, Carnian-Norian). Spilites, altered diabases and meta-basalts form part of Triassic volcanic-sedimentary sequence, made of sandstones, shales, micritic limestone, altered vitric tuffs and radiolarian cherts, incorporated tectonically into the Jurassic-Cretaceous mélange. The architecture of the 2 km long and 100 m high pile of the extrusive basaltoid rocks is interpreted as a subaqueous basaltic lava flow. The presented research deals with a variety of volcanic facies of the subaqueous basaltic lava flow, which consists of several facial units: 1. Coherent pillow lavas, with massive core; the bending rims around the massive core, 30-50 cm thick, are dissected by polygonal columnar joints radiating from the pillow centres; 2. Closely packed pillows; densely packed and contorted pillows due to emplacement accommodation, clearly younging upward; 3. Pillow fragment breccia; clast supported, matrix poor, monomict breccia, formed proximal to the axis of the extrusion; 4. Isolated pillow breccia; matrix supported, clast poor breccia, made of lava pipes and tubes, within a matrix of fine-grained sideromelan granules and shards; 5. Pyjama-style pillows; spherical, decimetre to meter size pillow lava balls, grown and chilled in isostatic state (i.e. in a state of diminished density contrast) within water-soaked sediments, named after peculiar alternating basaltic shelves inside the sphere, which are encrusted with white secondary minerals; 6. Peperite and peperitic hyaloclastites; blocky and globular peperites developed at the contact of soft, wet sediment and hot intruding magma. Discovery of peperite and peperitic hyaloclastites within the Triassic radiolarian cherts, shales, and micritic

  7. The remittances of migrant Tongan and Samoan nurses from Australia

    Directory of Open Access Journals (Sweden)

    Brown Richard PC

    2004-04-01

    Full Text Available Abstract Background Migration and remittances are of considerable importance in the small Pacific island states. There has been a significant migration of skilled health workers in recent decades to metropolitan fringe states, including Australia and New Zealand. This paper reports the findings of a re-analysis of survey of Samoan and Tongan migrants in Australia where the sample is split between nurse households and others. Methods The study analyzes the survey data with a view to comparing the remittance behaviour and determinants of remittances for nurses and other migrant households, using both descriptive, cross-tabulations and appropriate econometric methods. Results It is found that a significantly higher proportion of nurse households sent remittances home, and, on average remitted more. Remittances of nurse households did not decline significantly over time contrary to what has generally been predicted. This was in contrast to other migrant households in the sample, for whom remittances showed a sharp decline after 15 years absence. Remittances contribute much more to the income of migrant sending countries, than the cost of the additional human capital in nurse training. Conclusions Given the shortage of nurses in Australia and New Zealand, and therefore the high demand for immigrant nurses, investment by Pacific island governments and families in nurse training constitutes a rational use of economic resources. Policies encouraging investment in home countries may be more effective than policies directly discouraging brain drain in contributing to national development.

  8. Biomineralization and biosignatures of coralloid-type speleothems from lava tubes of Galapagos Islands: evidences on the fossil record of prokaryotes

    Science.gov (United States)

    Miller, Ana Z.; Garcia-Sanchez, Angela M.; Pereira, Manuel F. C.; Gazquez, Fernando; Calaforra, José M.; Forti, Paolo; Toulkeridis, Theofilos; Martínez-Frías, Jesús; Saiz-Jimenez, Cesareo

    2016-04-01

    Lava tubes have traditionally been considered of little interest from a mineralogical point of view. Recently, this type of volcanic caves has received particular attention because lava tubes have been described on Mars. Speleothems, or secondary mineral deposits in lava tubes are mainly composed of siliceous minerals. Coralloid-type speleothems are found either on basaltic cave walls or on the surface of other speleothems. Several authors attribute a microbially mediated origin to their formation. This type of speleothems was recorded within Royal Palm Cave of Santa Cruz Island in Galapagos Archipelago (Ecuador), a lava tube 600 m long, 5 to 15 m height and 2 to 10 m width. The Galapagos Islands are an archipelago of 19 volcanic islands located some 1500 km west of Ecuador, in the Pacific Ocean. These islands host one of the most biodiverse settings on Earth, studied by Charles Darwin. Beige and greyish small coralloids were collected in Royal Palm Cave and analysed by field emission scanning electron microscopy with energy dispersive X-ray spectroscopy (FESEM-EDS), X-ray micro-computed tomography (micro-CT) and mineralogical analyses for morphological, 3D microstructural and compositional characterization, as well as for assessing microbe-mineral interactions and biogenicity. In addition, 16S rRNA gene analyses were performed to identify microbial communities associated with the coralloid-type speleothems. The coralloids showed internal compositional zonation along the growth direction of the speleothems, according to micro-CT data. Internal layering was clearly discernable by the differences in opacity of the distinct mineralogical phases to X-rays, being dominated by alteration products of siliceous composition, whereas more opaque phases, usually Ca-rich minerals, were dominant in the outermost part of the speleothems. X-ray diffraction and infrared spectroscopy reinforced that the first stage of deposition is mainly composed of opal A and clay minerals

  9. Beliefs and attitudes of Samoan women toward early detection of breast cancer and mammography utilization.

    Science.gov (United States)

    Ishida, D N; Toomata-Mayer, T F; Braginsky, N S

    2001-01-01

    Among Pacific Islanders in Hawaii, the breast has been the foremost cancer site. Among Samoans, it is a leading cancer site along with sites for respiratory cancers. A recent study reported that cancer has been diagnosed at relatively advanced stages in younger Samoans. An exploratory, qualitative design was used with a semi-structured, open ended, talk story interview with Samoan women aged 40 years and older who spoke English and who had no personal history of breast cancer. The coding of interviews was validated with a faculty member unrelated to the study. Interviews were stopped at 15 participants once thematic patterns were saturated. Content analysis was performed. Triangulation to validate results was performed with research assistants and one participant. Participants ranged from 40-73 years of age, had lived in the U.S. 3-40 years, and most were married, born in Samoa or American Samoa, and had health insurance. Their education ranged from ninth grade to some college. Their health promotion activities included eating right, exercising, immunizing their children, and visiting their physician for an annual examination. Most had had positive or neutral experiences with western health care. Most reported that they would use Samoan medicine if available. Priorities reported were health, family, and education. Women considered the care and health of their families their responsibility. All had negative perceptions of cancer. Most had had mammograms. Reported major barriers to mammography were fear, not a priority, and pain. Reported major motivators were physician recommendation, prevention, and fear. Over half of the women reported concern over their breasts being touched either by themselves or by others. The study participants had strong beliefs that cancer meant death and, therefore, no cure. Samoan women emphasized the health and education of their families and their role in family health care. Therefore, health care providers should promote health and

  10. Increasing Pap Smear Utilization Among Samoan Women: Results from a Community Based Participatory Randomized Trial

    Science.gov (United States)

    Mishra, Shiraz I.; Luce, Pat H.; Baquet, Claudia R.

    2013-01-01

    Background We tested the effectiveness of a theory-guided, culturally tailored cervical cancer education program designed to increase Pap smear use among Samoan women residing in the U.S. Territory of American Samoa. Methods We used a two-group, pretest-posttest design. The sample comprised 398 Samoan women age 20 and older who we recruited from Samoan churches. Women in the intervention group received a culturally tailored cervical cancer education program in three weekly sessions. The primary outcome was self-reported receipt of a Pap smear. Results Overall, there was a significant intervention effect, with intervention compared with control group women twice (adjusted odds ratio = 2.0, 95% confidence interval = 1.3–3.2, pPap smear use at the posttest. Conclusions The findings support the efficacy of the multifaceted, theory-guided, culturally tailored community-based participatory cervical cancer education program for Samoan women in effecting positive changes in Pap smear use and cervical cancer related knowledge and attitudes. PMID:19711495

  11. Barriers to Increasing Native Hawaiian, Samoan, and Filipino Nursing Students: Perceptions of Students and Their Families.

    Science.gov (United States)

    Harrigan, Rosanne C.; Gollin, Lisa X.; Casken, John

    2003-01-01

    A survey of parents, high school students, and community members (n=92) and focus groups with 34 current and potential nursing students indicate that Asian Pacific Islanders are composed of distinct groups that have diverse concerns. Results suggest ways to increase the recruitment and retention of native Hawaiian, Filipino, and Samoan nursing…

  12. Lava cooling modelled with GPUSPH

    Science.gov (United States)

    Ganci, Gaetana; Zago, Vito; Bilotta, Giuseppe; Cappello, Annalisa; Herault, Alexis; Del Negro, Ciro

    2017-04-01

    Lava flows are highly complex flows exhibiting non-Newtonian rheology with temperature dependent viscosity and phase transition. The details of the rheology and its dependency on the physical and chemical properties of the lava need to be further addressed. GPUSPH is a fully three-dimensional model for the simulation of the thermal and rheological evolution of lava flows that relies on the Smoothed Particle Hydrodynamics (SPH) numerical method. Thanks to the Lagrangian, meshless nature of SPH, the model incorporates a more complete physical description of the emplacement process and rheology of lava that considers the free surface, the irregular boundaries represented by the topography, the solidification fronts and the non-Newtonian rheology. We present here the validation of the GPUSPH thermal model, including phase transition (particularly solidification). Validation is done against a number of different problems of growing complexity: the classical Stefan problem, for which analytical solutions are possible, the cooling of a lava lake (compared against semi-analytical solutions) and the cooling of a lava flow comparing the results against a FEM model. We also model the crust formation and thickening, studying the evolution of solidification over time in relation to emplacement characteristics such as total flow thickness and the thermal parameter of liquid and solid lava (emissivity and conductivity). Finally we compare GPUSPH results with a real case study on Etna volcano during the 12th August 2011 lava fountain for which we collected thermal camera data.

  13. No molecular epidemiological evidence supporting household transmission of zoonotic Giardia duodenalis and Cryptosporidium spp. from pet dogs and cats in the province of Álava, Northern Spain.

    Science.gov (United States)

    de Lucio, Aida; Bailo, Begoña; Aguilera, María; Cardona, Guillermo A; Fernández-Crespo, Juan C; Carmena, David

    2017-06-01

    The role of pet dogs and cats as suitable source of human infections by the diarrheagenic protozoan parasites Giardia duodenalis and Cryptosporidium spp. has been a topic of intense debate for long time and still remains a largely unsolved problem. In this cross-sectional molecular epidemiological survey we attempted to investigate whether zoonotic (or zooanthroponotic) disease transmission was occurring among humans and domestic dogs and cats sharing the same spatial and temporal setting in both rural and urban areas of the province of Álava, Northern Spain. A total of 268 (including 179 human, 55 canine, and 34 feline) individual faecal specimens were obtained from 63 family households during February-March and November-December 2014. Detection of G. duodenalis cysts and Cryptosporidium spp. oocysts was achieved by direct fluorescence microscopy (DFAT) and PCR-based methods targeting the small subunit (SSU) ribosomal RNA gene of the parasites. Giardia-positive isolates were subsequently sub-genotyped at the glutamate dehydrogenase (GDH) and β-giardin (BG) genes. Overall, G. duodenalis infections were identified in 3.4% (6/179) of humans, 29% (16/55) of dogs, and 5.9% (2/34) of cats, respectively. Cryptosporidium spp. infections were detected in 1.1% (2/179) of humans, 5.5% (3/55) of dogs, and 8.8% (3/34) of cats, respectively. Simultaneous infections in human and canine/feline hosts by G. duodenalis or Cryptosporidium spp. were only demonstrated in a single household in which a cat and its owner tested positive for Cryptosporidium by DFAT, but this result could not be confirmed by SSU-PCR. Infections were homogeneously distributed among the studied human or animal populations irrespectively of their sex, age group, or geographical region of origin. Inadequate washing of raw vegetables and fruits was the only risk factor significantly associated to a higher likelihood of having human giardiosis/cryptosporidiosis. Molecular characterization of G. duodenalis

  14. Viewing Time Measures of Sexual Orientation in Samoan Cisgender Men Who Engage in Sexual Interactions with Fa?afafine

    OpenAIRE

    Petterson, Lanna J.; Barnaby J. Dixson; Little, Anthony C; Vasey, Paul L

    2015-01-01

    Androphilia refers to attraction to adult males, whereas gynephilia refers to attraction to adult females. The current study employed self-report and viewing time (response time latency) measures of sexual attraction to determine the sexual orientation of Samoan cisgender men (i.e., males whose gender presentation and identity is concordant with their biological sex) who engage in sexual interactions with transgender male androphiles (known locally as fa'afafine) compared to: (1) Samoan cisge...

  15. Petrogenesis of arc lavas from the Rucu Pichincha and Pan de Azucar volcanoes (Ecuadorian arc): Major, trace element, and boron isotope evidences from olivine-hosted melt inclusions

    Science.gov (United States)

    Le Voyer, Marion; Rose-Koga, Estelle F.; Laubier, Muriel; Schiano, Pierre

    2008-12-01

    Primary melt inclusions in olivine phenocrysts (Fo74-89) of basic lavas from Pichincha and Pan de Azucar volcanoes (in the front and rear arcs of the Ecuadorian Andes, respectively) were analyzed by electron microprobe for major elements and by ion microprobe for trace element and boron isotope compositions. Although melt inclusions in the most magnesium-rich olivines contain relatively primitive magmas, their compositions are not directly linked to those of the whole rocks through a differentiation scheme. They are characterized by nepheline-normative compositions with low SiO2 contents (39.8-47.9 wt%) and unusually high CaO contents (up to 15.4 wt%), which cannot be derived from melting of a simple peridotitic mantle. We explain their formation by the presence of amphibole-bearing olivine-clinopyroxenites in the source of these melts. The trace elements patterns of the melt inclusions show the typical trace element features of arc magmas, such as enrichment in LILE and LREE, and negative anomalies in Nb and Ti. Across-arc variations of mobile versus less mobile incompatible element ratios indicate a decreasing input of a mobile phase from the slab to the mantle wedge with the distance to the trench, along with a decrease in the degree of melting. Boron isotope compositions are highly variable within each volcano (δ11B from -9.5 ± 1.3‰ to +3.5 ± 1.4‰ for the Pichincha melt inclusions and from -17.9 ± 0.8‰ to -1.9 ± 1.4‰ for the Pan de Azucar melt inclusions) and suggest trapping of isotopically heterogeneous melts. Modeling of both dehydration and fusion of the slab indicates that the Pichincha melt inclusions were formed by melting a source enriched by the addition of 1% of a heterogeneous aqueous fluid derived from the dehydration of both the sediments and the altered oceanic crust (after 74 and 76% of B loss, respectively). The phase that metasomatizes the source of the Pan de Azucar melt inclusions can be either an input of 0.1% of a heterogeneous

  16. Conceptual distance and word learning: patterns of acquisition in Samoan-English bilingual children.

    Science.gov (United States)

    Hemsley, Gayle; Holm, Alison; Dodd, Barbara

    2013-09-01

    This study investigated cross-linguistic influence in acquisition of a second lexicon, evaluating Samoan-English sequentially bilingual children (initial mean age 4 ; 9) during their first 18 months of school. Receptive and Expressive Vocabulary tasks evaluated acquisition of four word types: cognates, matched nouns, phrasal nouns and holonyms. Each word type had varying phonological and conceptual difference between Samoan (L1) and English (L2). Results highlighted conceptual distance between L1 and L2 as a key factor in L2 lexical acquisition. The children acquired L2 lexical items earlier if their conceptual representation was similar to that of L1. Words with greater conceptual distance between L1 and L2 emerged more slowly. This suggests that L1 knowledge influences L2 lexical consolidation for sequential bilinguals. Words that require a conceptual shift from L1 take longer to consolidate and strengthen within the L2 lexicon.

  17. Epigenetics, and human biology and health responses to modernization in the Samoan archipelago.

    Science.gov (United States)

    McGarvey, Stephen T

    2012-12-01

    Epigenetic mechanisms offer explanations for how environmental exposures at critical life periods may affect human biological and disease phenotypes. Incorporation of epigenetic approaches into research on health consequences of societal transitions may increase understanding of the complex biobehavioral factors influencing changing populations. Description of present and planned genetic epidemiology research, including epigenetic studies, among Samoans experiencing economic modernization and globalization offer examples for progress in knowledge of population health transitions.

  18. Samoan Smokers Talk about Smoking and Quitting: A Focus Group Study.

    Science.gov (United States)

    Tanielu, Helen; McCool, Judith; Umali, Elaine; Whittaker, Robyn

    2017-06-29

    Samoa, like other Pacific Island countries, faces a persistent challenge to reduce smoking use with relatively limited resources. As a signatory to the WHO FCTC, Samoa is obligated to introduce measures to reduce tobacco use and is currently trialling a text message smoking cessation programme (mCessation) to achieve this outcome. Cigarettes remain relatively cheap and are widely available, but little is known about how smoking is initiated or why and how people quit smoking in the Samoa. Six focus groups with smokers and ex-smokers were conducted in Apia, Samoa. Groups were homogenous according to age, gender and smoking status. Focus groups were conducted in Samoan and transcribed and translated to English for analysis. Smoking is initiated most commonly in late teens and early twenties and most frequently in (non-family) social contexts. Smoking reflects a widely held (mis)perceptions of tangible benefits, including aiding feelings of strength and energy, relief from indigestion and as a means to accelerate the effects of alcohol. Smoking was deeply connected to social life in Samoa among friends and for some, with family members. Drivers to quit originate out of concern regarding health effects, concern for family and the costs of purchasing tobacco. Smoking is well entrenched in Samoan society; efforts to reduce smoking need to be based on implicit understanding of Samoan cultural norms and priorities around family, social networks and culture. Efforts to support quitting are important, alongside other well validated measures to reverse the trajectory of smoking related disease. This study offers an insight into smoking as a behaviour and as cultural practice perceived by smokers and non-smokers in Samoa. A thorough understanding of smoking behaviours and cessation patterns is critical in efforts to reduce smoking especially in resource-limited settings. The results from this study was used to inform the development of a Samoan mHealth smoking cessation

  19. The Disruption of Tephra Fall Deposits by Basaltic Lava Flows

    Science.gov (United States)

    Brown, R. J.; Thordarson, T.; Self, S.; Blake, S.

    2010-12-01

    Complex physical and stratigraphic relationships between lava and proximal tephra fall deposits around vents of the Roza Member in the Columbia River Basalt Province, (CRBP), USA, illustrate how basaltic lavas can disrupt, dissect (spatially and temporally) and alter tephra fall deposits. Thin pahoehoe lobes and sheet lobes occur intercalated with tephra deposits and provide evidence for synchronous effusive and explosive activity. Tephra that accumulated on the tops of inflating pahoehoe flows became disrupted by tumuli, which dissected the overlying sheet into a series of mounds. During inflation of subjacent tumuli tephra percolated down into the clefts and rubble at the top of the lava, and in some cases came into contact with lava hot enough to thermally alter it. Lava breakouts from the tumuli intruded up through the overlying tephra deposit and fed pahoehoe flows that spread across the surface of the aggrading tephra fall deposit. Non-welded scoria fall deposits were compacted and welded to a depth of ~50 cm underneath thick sheet lobes. These processes, deduced from the field relationships, have resulted in considerable stratigraphic complexity in proximal regions. We also demonstrate that, when the advance of lava and the fallout of tephra are synchronous, the contacts of some tephra sheets can be diachronous across their extent. The net effect is to reduce the usefulness of pyroclastic deposits in reconstructing eruption dynamics.

  20. Evaluation of some Samoan and Peruvian medicinal plants by prostaglandin biosynthesis and rat ear oedema assays.

    Science.gov (United States)

    Dunstan, C A; Noreen, Y; Serrano, G; Cox, P A; Perera, P; Bohlin, L

    1997-06-01

    In our ongoing program to find new anti-inflammatory compounds, 58 extracts from 46 different medicinal plant species, used in treatment of inflammatory disorders-38 plants from the traditional medicine of Western Samoa and eight originating from the indigenous medicine of the Shipibo-Conibo tribe of Peruvian Amazonia-ere evaluated. The ability of all extracts to inhibit cyclooxygenase-1 catalysed prostaglandin biosynthesis in vitro was examined. Of the plant species tested 14 showed moderate to strong inhibition; including 11 Samoan and three Peruvian species. Further, 12 Samoan and all eight Peruvian species were investigated on their inhibitory activity of ethyl phenylpropiolate induced rat ear oedema in vivo. Significant activity was shown by 10 of the Samoan and by all eight Peruvian species. An additional evaluation of the most active species was provided through a compilation of existing literature documenting traditional medicinal uses, pharmacological activity and chemical constituents. Several known cyclooxygenase-1 inhibitors were reported to which the observed pharmacological activity can be attributed at least partly. The combination of chemical and pharmacological literature data and our experimental data may help to explain the anti-inflammatory use of these species in indigenous medicine.

  1. Newberry Volcano's youngest lava flows

    Science.gov (United States)

    Robinson, Joel E.; Donnelly-Nolan, Julie M.; Jensen, Robert A.

    2015-01-01

    Most of Newberry Volcano's youngest lava flows are found within the Newberry National Volcanic Monument in central Oregon. Established November 5, 1990, the monument is managed by the U.S. Forest Service as part of the Deschutes National Forest. Since 2011, a series of aerial surveys over the monument collected elevation data using lidar (light detection and ranging) technology, which uses lasers to directly measure the ground surface. These data record previously unseen detail in the volcano’s numerous lava flows and vents. On average, a laser return was collected from the ground’s surface every 2.17 feet (ft) with ±1.3 inches vertical precision.

  2. LAVA Pressure Transducer Trade Study

    Science.gov (United States)

    Oltman, Samuel B.

    2016-01-01

    The Regolith and Environment Science and Oxygen and Lunar Volatile Extraction (RESOLVE) payload will transport the (LAVA) subsystem to hydrogen-rich locations on the moon supporting NASA's in-situ resource utilization (ISRU) programs. There, the LAVA subsystem will analyze volatiles that evolve from heated regolith samples in order to quantify how much water is present. To do this, the system needs resilient pressure transducers (PTs) to calculate the moles in the gas samples. The PT trade study includes a comparison of newly-procured models to a baseline unit with prior flight history in order to determine the PT model with the best survivability in flight-forward conditions.

  3. Incorporation of seawater into mid-ocean ridge lava flows during emplacement

    Science.gov (United States)

    Soule, S.A.; Fornari, D.J.; Perfit, M.R.; Ridley, W.I.; Reed, M.H.; Cann, J.R.

    2006-01-01

    Evidence for the interaction between seawater and lava during emplacement on the deep seafloor can be observed in solidified flows at a variety of scales including rapid quenching of their outer crusts and the formation of lava pillars through the body of the flow. Recently, an additional interaction, incorporation of heated seawater (vapor) into the body of a flow, has been proposed. Large voids and vesicles beneath the surface crusts of mid-ocean ridge crest lobate and sheet lava flows and lava drips found within those cavities have been cited as evidence for this interaction. The voids resulting from this interaction contribute to the high porosity of the shallow ocean crust and play an important role in crustal permeability and hydrothermal circulation at mid-ocean ridges, and thus it is important to understand their origin. We analyze lava samples from the fast-spreading East Pacific Rise and intermediate-spreading Galapagos Spreading Center to characterize this process, identify the source of the vapor, and investigate the implications this would have on submarine lava flow dynamics. We find that lava samples that have interacted with a vapor have a zone of increased vesicularity on the underside of the lava crust and a coating of precipitate minerals (i.e., crystal fringe) that are distinct in form and composition from those crystallized from the melt. We use thermochemical modeling to simulate the reaction between the lava and a vapor and find that only with seawater can we reproduce the phase assemblage we observe within the crystal fringes present in the samples. Model results suggest that large-scale contamination of the lava by mass exchange with the vapor is unlikely, but we observe local enrichment of the lava in Cl resulting from the incorporation of a brine phase separated from the seawater. We suggest that high eruption rates are necessary for seawater incorporation to occur, but the mechanism by which seawater enters the flow has yet to be

  4. The origin of tubular lava stalactites and other related forms

    Directory of Open Access Journals (Sweden)

    Kevin Allred

    1998-01-01

    Full Text Available Tubular lava stalactites are often found in lava tubes. Field observations, sample analysis, and comparative studies indicate that these are segregations extruded during cooling from partially crystallized lava al about 1,070 - 1,000 °C. Retrograde boiling (gas pressure within the lava provides a mechanism to expel the interstitial liquid. In addition to tubular lava stalactites, a variety of other lava features can also result, such as lava helictites, lava coralloids, barnacle-like stretched lava, runners, runner channels, and some lava blisters and squeeze-ups.

  5. (Invariability in the Samoan syntax/prosody interface and consequences for syntactic parsing

    Directory of Open Access Journals (Sweden)

    Kristine M. Yu

    2017-10-01

    Full Text Available While it has long been clear that prosody should be part of the grammar influencing the action of the syntactic parser, how to bring prosody into computational models of syntactic parsing has remained unclear. The challenge is that prosodic information in the speech signal is the result of the interaction of a multitude of conditioning factors. From this output, how can we factor out the contribution of syntax to conditioning prosodic events? And if we are able to do that factorization and define a production model from the syntactic grammar to a prosodified utterance, how can we then define a comprehension model based on that production model? In this case study of the Samoan morphosyntax-prosody interface, we show how to factor out the influence of syntax on prosody in empirical work and confirm there is invariable morphosyntactic conditioning of high edge tones. Then, we show how this invariability can be precisely characterized and used by a parsing model that factors the various influences of morphosyntax on tonal events. We expect that models of these kinds can be extended to more comprehensive perspectives on Samoan and to languages where the syntax/prosody coupling is more complex.

  6. Distinct degassing processes during lava fountains revealed by OP-FTIR measurements: Mt. Etna's 2001 lava fountain sequence

    Science.gov (United States)

    La Spina, Alessandro; Burton, Mike; Allard, Patrick; Alparone, Salvatore; Murè, Filippo

    2010-05-01

    During the two months preceding the 2001 July-August flank eruption of Mt. Etna, 17 discrete lava fountaining events were observed at the southeast crater (SEC, 3250 m a.s.l.). Each episode was preceded by lava effusion and mild strombolian activity from a fracture on the NE flank of the SEC. We used an open-path Fourier transform infrared spectrometer (OP-FTIR) to measure every about 5 seconds an IR absorption spectrum of the gas powering the lava fountains, lava being the source of radiation. Spectral-fitting procedures allowed retrieval of the relative amounts of H2O, CO2, SO2, HCl and HF present in the volcanic gas phase, allowing us to track variations in the gas composition both during each fountain event and over the entire sequence. We present the chemical composition of gases emitted from the SEC during 9 of the 17 lava fountaining events. Three distinct phases in each fountain were observed in terms of seismic tremor, volcanic activity and gas composition. We observed the following: (i) The highest CO2/SO2 ratio observed during each paroxysm coincided with the peak in fountaining intensity and seismic tremor amplitude; (ii) The longer the pause between lava fountains the higher the observed peak CO2/SO2 ratio and tremor amplitude; and (iii) the SO2/HCl ratio noticeably decreased during phases of enhanced fine ash emission. We interpret the variations in gas composition and volcanic activity as due to the combined effects of two distinct processes: periodic emptying of a bubble foam layer accumulating at ~2 km depth and syn-eruptive degassing during magma fragmentation. The clear correlation between the repose time between lava fountains and their intensity and CO2/SO2 peak ratio evidences a main control of the fountain series by bubble foam accumulation and emptying. The surprising decrease in SO2/HCl during the peaks in eruptive activity is attributed to enhanced HCl outgassing during more extensive magma fragmentation and entrainment of atmospheric air

  7. What factors control superficial lava dome explosivity?

    Science.gov (United States)

    Boudon, Georges; Balcone-Boissard, Hélène; Villemant, Benoît; Morgan, Daniel J

    2015-09-30

    Dome-forming eruption is a frequent eruptive style and a major hazard on numerous volcanoes worldwide. Lava domes are built by slow extrusion of degassed, viscous magma and may be destroyed by gravitational collapse or explosion. The triggering of lava dome explosions is poorly understood: here we propose a new model of superficial lava-dome explosivity based upon a textural and geochemical study (vesicularity, microcrystallinity, cristobalite distribution, residual water contents, crystal transit times) of clasts produced by key eruptions. Superficial explosion of a growing lava dome may be promoted through porosity reduction caused by both vesicle flattening due to gas escape and syn-eruptive cristobalite precipitation. Both processes generate an impermeable and rigid carapace allowing overpressurisation of the inner parts of the lava dome by the rapid input of vesiculated magma batches. The relative thickness of the cristobalite-rich carapace is an inverse function of the external lava dome surface area. Explosive activity is thus more likely to occur at the onset of lava dome extrusion, in agreement with observations, as the likelihood of superficial lava dome explosions depends inversely on lava dome volume. This new result is of interest for the whole volcanological community and for risk management.

  8. Emplacing a Cooling-Limited Rhyolite Lava Flow: Similarities with Basaltic Lava Flows

    Directory of Open Access Journals (Sweden)

    Nathan Magnall

    2017-06-01

    Full Text Available Accurate forecasts of lava flow length rely on estimates of eruption and magma properties and, potentially more challengingly, on an understanding of the relative influence of characteristics such as the apparent viscosity, the yield strength of the flow core, or the strength of the lava's surface crust. For basaltic lavas, the relatively high frequency of eruptions has resulted in numerous opportunities to test emplacement models on such low silica lava flows. However, the flow of high silica lava is much less well understood due to the paucity of contemporary events and, if observations of flow length change are used to constrain straightforward models of lava advance, remaining uncertainties can limit the insight gained. Here, for the first time, we incorporate morphological observations from during and after flow field evolution to improve model constraints and reduce uncertainties. After demonstrating the approach on a basaltic lava flow (Mt. Etna 2001, we apply it to the 2011–2012 Cordón Caulle rhyolite lava flow, where unprecedented observations and syn-emplacement satellite imagery of an advancing silica-rich lava flow have indicated an important influence from the lava flow's crust on flow emplacement. Our results show that an initial phase of viscosity-controlled advance at Cordón Caulle was followed by later crustal control, accompanied by formation of flow surface folds and large-scale crustal fractures. Where the lava was unconstrained by topography, the cooled crust ultimately halted advance of the main flow and led to the formation of breakouts from the flow front and margins, influencing the footprint of the lava, its advance rate, and the duration of flow advance. Highly similar behavior occurred in the 2001 Etna basaltic lava flow. In our comparison of these two cases, we find close similarities between the processes controlling the advance of a crystal-poor rhyolite and a basaltic lava flow, suggesting common controlling

  9. Dietary Patterns Are Associated with Metabolic Outcomes among Adult Samoans in a Cross-Sectional Study.

    Science.gov (United States)

    Wang, Dongqing; Hawley, Nicola L; Thompson, Avery A; Lameko, Viali; Reupena, Muagatutia Sefuiva; McGarvey, Stephen T; Baylin, Ana

    2017-04-01

    Background: The Samoan population has been undergoing a nutrition transition toward more imported and processed foods and a more sedentary lifestyle. Objectives: We aimed to identify dietary patterns in Samoa and to evaluate their associations with metabolic outcomes. Methods: The sample of this cross-sectional study includes 2774 Samoan adults recruited in 2010 (1104 with metabolic syndrome compared with 1670 without). Principal component analysis on food items from a 104-item food-frequency questionnaire was used to identify dietary patterns. Adjusted least squares means of each component of metabolic syndrome were estimated by quintiles of factor scores for each dietary pattern. Metabolic syndrome status was regressed on quintiles of scores by using log-binomial models to obtain prevalence ratios. Results: We identified a modern pattern, a mixed-traditional pattern, and a mixed-modern pattern. The modern pattern included a high intake of imported and processed foods, including pizza, cheeseburgers, margarine, sugary drinks, desserts, snacks, egg products, noodles, nuts, breads, and cakes and a low intake of traditional agricultural products and fish. The mixed-traditional pattern had a high intake of neotraditional foods, including fruits, vegetables, soup, poultry, and fish, and imported and processed foods, including dairy products, breads, and cakes. The mixed-modern pattern was loaded with imported and processed foods, including pizza, cheeseburgers, red meat, egg products, noodles, and grains, but also with neotraditional foods, such as seafood and coconut. It also included a low intake of fish, tea, coffee, soup, and traditional agricultural staples. Higher adherence to the mixed-modern pattern was associated with lower abdominal circumference ( P -trend pattern was inversely associated with prevalence of metabolic syndrome (the highest quintile: prevalence ratio = 0.79; 95% CI: 0.69, 0.91; P -trend = 0.006). Conclusion: Mixed dietary patterns containing

  10. Bullying, Physical Aggression, Gender-Atypicality, and Sexual Orientation in Samoan Males.

    Science.gov (United States)

    Semenyna, Scott W; Vasey, Paul L

    2017-07-01

    Bullying is characterized by the repeated attempts of a group or individual to gain social advantage by the use of relational, verbal, or physical aggression against a target, especially when there is a perceived or actual power imbalance (Espelage & Swearer, 2003). One consistent finding is that gay (i.e., androphilic) males report higher rates of victimization due to bullying in adolescence than their heterosexual (i.e., gynephilic) counterparts. Western data indicate that gender-atypical behavior, regardless of sexual orientation, is a key predictor of victimization due to bullying. Androphilic males generally display childhood gender-atypicality, including reduced levels of physical aggression, which may cause bullies to perceive them as "easy" targets. In order to test the associations between sexual orientation, childhood gender-atypicality, and recalled victimization due to bullying, a sample of Samoan gynephilic men (n = 100) were compared to a group of Samoan transgender androphilic males (n = 103), known as fa'afafine. Although the fa'afafine reported far more childhood gender-atypicality, the two groups did not differ significantly on measures of physical aggression or their reported rates of victimization due to bullying. Additionally, greater physical aggression, not gender-atypicality, was the only significant predictor of being bullied in both men and fa'afafine. These results suggest that there is nothing inherent in sexual orientation or childhood gender-atypicality that would potentiate victimization from bullying. Instead, the cultural context in which a bully functions influences the extent to which these are "acceptable" reasons to target certain individuals.

  11. Tephra on Lava Flows Promotes Vegetation Development: Case Studies From Recent Holocene Lava Flows

    Science.gov (United States)

    Deligne, N. I.; Cashman, K. V.

    2011-12-01

    Volcanic eruptions re-surface landscapes rapidly with lava flows, pyroclastic deposits, or a combination of both. Whereas explosive deposits are generally fine grained and share many characteristics with fertile soil, lava does not - it is massive, fractured, and sterile rock. As such, barren lava presents a formidable challenge for plant colonization. However, most lava-forming eruptions have an explosive component, albeit often in the early stages of activity prior to lava emplacement when the magma still has a considerable gas fraction. Tephra from the explosive stage of an eruption blankets local and downwind areas, and tephra thickness decreases exponentially with distance from the vent. We examine several sites of Holocene volcanism in the United States, Mexico, and Italy and find that in the absence of tephra or external sources of soil, vegetation establishment and growth on lava flows is exceptionally slow. Conversely, lava flows with late stage syn-eruptive explosive activity or lava flows in areas with subsequent repeat volcanism have considerable vegetation development. Although thick tephra blankets hinder plant establishment, it appears that tephra deposits on lava flows provide a growth medium and enhances water retention, promoting plant colonization and vegetation development. Our results caution against the common practice of mapping lava flows based on vegetation, and provide new insights on key factors in plant establishment and growth on lava flows.

  12. A Sinuous Tumulus over an Active Lava Tube at Klauea Volcano: Evolution, Analogs, and Hazard Forecasts

    Science.gov (United States)

    Orr, Tim R.; Bleacher, Jacob E.; Patrick, Matthew R.; Wooten, Kelly M.

    2015-01-01

    Inflation of narrow tube-fed basaltic lava flows (tens of meters across), such as those confined by topography, can be focused predominantly along the roof of a lava tube. This can lead to the development of an unusually long tumulus, its shape matching the sinuosity of the underlying lava tube. Such a situation occurred during Klauea Volcanos (Hawaii, USA) ongoing East Rift Zone eruption on a lava tube active from July through November 2010. Short-lived breakouts from the tube buried the flanks of the sinuous, ridge-like tumulus, while the tumulus crest, its surface composed of lava formed very early in the flows emplacement history, remained poised above the surrounding younger flows. At least several of these breakouts resulted in irrecoverable uplift of the tube roof. Confined sections of the prehistoric Carrizozo and McCartys flows (New Mexico, USA) display similar sinuous, ridge-like features with comparable surface age relationships. We contend that these distinct features formed in a fashion equivalent to that of the sinuous tumulus that formed at Kilauea in 2010. Moreover, these sinuous tumuli may be analogs for some sinuous ridges evident in orbital images of the Tharsis volcanic province on Mars. The short-lived breakouts from the sinuous tumulus at Kilauea were caused by surges in discharge through the lava tube, in response to cycles of deflation and inflation (DI events) at Kilauea's summit. The correlation between DI events and subsequent breakouts aided in lava flow forecasting. Breakouts from the sinuous tumulus advanced repeatedly toward the sparsely populated Kalapana Gardens subdivision, destroying two homes and threatening others. Hazard assessments, including flow occurrence and advance forecasts, were relayed regularly to the Hawai?i County Civil Defense to aid their lava flow hazard mitigation efforts while this lava tube was active.

  13. Lava flow texture LiDAR signatures

    Science.gov (United States)

    Whelley, P.; Garry, W. B.; Scheidt, S. P.; Irwin, R. P., III; Fox, J.; Bleacher, J. E.; Hamilton, C. W.

    2014-12-01

    High-resolution point clouds and digital elevation models (DEMs) are used to investigate lava textures on the Big Island of Hawaii. An experienced geologist can distinguish fresh or degraded lava textures (e.g., blocky, a'a and pahoehoe) visually in the field. Lava texture depends significantly on eruption conditions, and it is therefore instructive, if accurately determined. In places where field investigations are prohibitive (e.g., Mercury, Venus, the Moon, Mars, Io and remote regions on Earth) lava texture must be assessed from remote sensing data. A reliable method for differentiating lava textures in remote sensing data remains elusive. We present preliminary results comparing properties of lava textures observed in airborne and terrestrial Light Detection and Ranging (LiDAR) data. Airborne data, in this study, were collected in 2011 by Airborne 1 Corporation and have a ~1m point spacing. The authors collected the terrestrial data during a May 2014 field season. The terrestrial scans have a heterogeneous point density. Points close to the scanner are 1 mm apart while 200 m in the distance points are 10 cm apart. Both platforms offer advantages and disadvantages beyond the differences in scale. Terrestrial scans are a quantitative representation of what a geologist sees "on the ground". Airborne scans are a point of view routinely imaged by other remote sensing tools, and can therefore be quickly compared to complimentary data sets (e.g., spectral scans or image data). Preliminary results indicate that LiDAR-derived surface roughness, from both platforms, is useful for differentiating lava textures, but at different spatial scales. As all lava types are quite rough, it is not simply roughness that is the most advantageous parameter; rather patterns in surface roughness can be used to differentiate lava surfaces of varied textures. This work will lead to faster and more reliable volcanic mapping efforts for planetary exploration as well as terrestrial

  14. Perceived social and media influences on tobacco use among Samoan youth.

    Science.gov (United States)

    McCool, Judith; Freeman, Becky; Tanielu, Helen

    2014-10-23

    Tobacco use among young Pacific populations continues to undermine efforts to reduce the escalating rates of non-communicable disease in the region. Reducing tobacco use to less than 5 percent by 2025 is now a World Health Organisation (WHO) mandated target for the Pacific region. Yet, little is known about the drivers to uptake of tobacco use among young people in the Pacific. Family and peers are expected to be important in this process, but similarly, tobacco marketing may also play an important role. The tobacco industry has been highly adaptive to the changing media environment across the Pacific Islands. The aim of this study was to develop an understanding of the social cultural and media drivers to tobacco uptake and use among young Samoans to contribute to the design of effective tobacco control intervention. We examined high school students (aged 16 and 17 years) perceptions of tobacco use in their community, access and use of media channels and the extent to which they are cognizant of both pro and anti-tobacco imagery across a range of media. Data was collected through in-depth semi-structured interviews. A thematic analysis of the interview data identified common and divergent beliefs, attitudes and behaviours surrounding tobacco use and the influence of the media. Family is critically important for representing normative tobacco use in Samoa. The use of media, in particular digital media, was found to be conditioned by parental views on the use of media in the home. Media access remains highly regulated within more traditional households. Loyalty to traditional cultural practices (Fa'a Samoa) underpinned views on the limited influence of media on social norms around tobacco use. Parents were thought to have the greatest influence on youth smoking. Tobacco use was viewed as a personal, or family issue, and not a problem that was amendable to change at a societal level. In order to develop effective and culturally relevant tobacco control policies, the

  15. Suggestive linkage detected for blood pressure related traits on 2q and 22q in the population on the Samoan islands

    Directory of Open Access Journals (Sweden)

    Sun Guangyun

    2009-10-01

    Full Text Available Abstract Background High blood pressure or hypertension is a major risk factor involved in the development of cardiovascular diseases. We conducted genome-wide variance component linkage analyses to search for loci influencing five blood pressure related traits including the quantitative traits systolic blood pressure (SBP, diastolic blood pressure (DBP and pulse pressure (PP, the dichotomous trait hypertension (HT and the bivariate quantitative trait SBP-DBP in families residing in American Samoa and Samoa, as well as in the combined sample from the two polities. We adjusted the traits for a number of environmental covariates such as smoking, alcohol consumption, physical activity and material life style. Results We found suggestive univariate linkage for SBP on chromosome 2q35-q37 (LOD 2.4 and for PP on chromosome 22q13 (LOD 2.2, two chromosomal regions that recently have been associated with SBP and PP, respectively. Conclusion We have detected additional evidence for a recently reported locus associated with SBP on chromosome 2q and a susceptibility locus for PP on chromosome 22q. However, differences observed between the results from our three partly overlapping genetically homogenous study samples from the Samoan islands suggest that additional studies should be performed in order to verify these results.

  16. GEOLOGICAL INVESTIGATION OF PALAEOTSUNAMIS IN THE SAMOAN ISLANDS: INTERIM REPORT AND RESEARCH DIRECTIONS

    Directory of Open Access Journals (Sweden)

    Tim Davies

    2013-01-01

    Full Text Available The September 29, 2009 Samoa Tsunami provided the opportunity to sample the sediments deposited in the Samoan Islands landscape by the tsunami. Analysing the characteristics of the sediment deposits using an established suite of diagnostic criteria, and assessing how they differ from cyclone deposits enables the identification and dating of similar events in the geologic record. This helps to better understand the long-term frequency and likely magnitude of these events. Here we report on a pilot palaeotsunami field-sampling investigation carried out in 2010 at selected sites on Upolu and Savaii Islands in the Independent State of Samoa, and on Ta’u Island in American Samoa. We present empirical stratigraphic data for the investigated sites, and we demonstrate the existence of high energy marine inundation deposits at some of these sites which were laid down by past tsunamis and/or cyclones. We review and discuss the analytical outcomes, as well as summarise the overarching directions of this research. We propose that there is a need for this study to continue and for such studies to be carried out in other islands in the Pacific. By doing this, we can build on the sparse palaeotsunami database in the region, thereby helping to improve our understanding of the long-term frequency, impact distribution, and likely magnitude of these events. Further, we can start assessing their likely sources and the long-term risk these hazards pose to coastal cities and communities in the Pacific.

  17. Three-dimensional laboratory modeling of the Tonga trench and Samoan plume interaction

    Science.gov (United States)

    Druken, K. A.; Kincaid, C. R.; Pockalny, R. A.; Griffiths, R. W.; Hart, S. R.

    2009-12-01

    Plume processes occurring near ridge centers (e.g. Iceland) or mid-plate (e.g. Hawaii) have been well studied; however, the behavior of a plume near a subducting plate is still poorly understood and may in fact differ from the typical expected plume surfacing patterns. We investigate how three-dimensional subduction-driven flow relates to the deformation and dispersal of nearby upwelling plume material and the associated geochemical spatial patterns, with site-specific comparisons to the Tonga trench and Samoan plume system. Eighteen plume-trench laboratory experiments were conducted with varied combinations of subduction motions (down-dip, trench rollback, slab steepening and back-arc extension) and plume parameters (position and temperature.) A phenolic plate and glucose syrup, with a temperature dependent viscosity, are used to model the slab and upper mantle, respectively. Hydraulic pistons control longitudinal, translational and steepening motions of the slab as a simplified kinematic approach to mimic dynamic experiments. Results show that the subduction-induced flow dominates the upwelling strength of the plume, causing a significant portion of the plume head to subduct before reaching the melt zone. The remaining material is entrained around the slab edge into the mantle wedge by the trench rollback-induced flow. The proportion of subducted verses entrained material is predominantly dependent on plume location (relative to the trench) and thermal strength, with additional effects from back-arc extension and plate steepening.

  18. Possible lava tube system in a hummocky lava flow at Daund ...

    Indian Academy of Sciences (India)

    http://www.ias.ac.in/article/fulltext/jess/113/04/0819-0829. Keywords. Pahoehoe; lava tube; inflation; emplacement; Deccan Volcanic Province. Abstract. A hummocky flow characterised by the presence of toes, lobes, tumuli and possible lava tube system is exposed near Daund, western Deccan Volcanic Province, India.

  19. Possible lava tube system in a hummocky lava flow at Daund ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    The roof of the lava tube has collapsed but original lava tube walls and fragments of the tube roof are seen at ... red bole. At places, the bole is green in colour. The ..... tube roof (figure 3c). Alternatively, these fragments may also represent tumulus crust, roofed over the tube. The petrography of the tube wall layers also pro-.

  20. Nornahraun lava morphology and mode of emplacement

    Science.gov (United States)

    Pedersen, Gro B. M.; Höskuldsson, Armann; Riishuus, Morten S.; Jónsdóttir, Ingibjörg; Gudmundsson, Magnús T.; Sigmundsson, Freysteinn; Óskarsson, Birgir V.; Drouin, Vincent; Gallagher, Catherine; Askew, Rob; Moreland, William M.; Dürig, Tobias; Dumont, Stephanie; Þórdarson, Þór

    2015-04-01

    The ongoing Nornahraun eruption is the largest effusive eruption in Iceland since the Laki eruption in 1783-84, with an estimated lava volume of ~1.15 km3 covering an area of ~83.4 km2 (as of 5 JAN 2015). The eruption provides an unprecedented opportunity to study i) lava morphologies and their emplacement styles, ii) the transition from from open to closed lava pathways and iii) lava pond formation. Tracking of the lava advancement and morphology has been performed by GPS and GoPro cameras installed in 4×4 vehicles as well as video footage. Complimentary observations have been provided from aircraft platforms and by satellite data. Of particular importance for lava morphology observations are 1-12 m/pixel airborne SAR images (x-band). The Nornahraun flow field comprises a continuum of morphologies from pāhoehoe to 'a'ā, which have varied tem-porally and spatially. At the onset of the eruption 31 AUG, lava flows advanced rapidly (400-800 m/hr) from the 1.5 km long fissure as large slabby pāhoehoe [1-3] sheet lobes, 100-500 m wide and 0.3-1 m thick at the flow fronts. By 1 SEPT, the flows began channeling towards the NE constrained by the older Holuhraun I lava field and the to-pography of flood plain itself. A central open channel developed, feeding a 1-2 km wide active 'a'ā frontal lobe that advanced 1-2 km/day. In addition to its own caterpillar motion, the frontal lobe advanced in a series of 30-50 m long breakouts, predominantly slabby and rubbly pāhoehoe [4,5]. These breakouts had initial velocities of 10-30 m/hr and reached their full length within tens of minutes and subsequently inflated over hours. With the continuous advancement of the 'a'ā flow front, the breakouts were incorporated into the 'a'ā flow fronts and seldom preserved. At the margins of the frontal lava lobe, the breakouts were more sporadic, but predominantly rubbly pāhoehoe and slabby pāhoehoe, as at the flow front. The lava flow advanced ENE into Jökulsá á Fjöllum on 7 SEPT

  1. The Payun-Matru lava field: a source of analogues for Martian long lava flows

    Science.gov (United States)

    Giacomini, L.; Pasquarè, G.; Massironi, M.; Frigeri, A.; Bistacchi, A.; Frederico, C.

    2007-08-01

    The Payun Matru Volcanic complex is a Quaternary fissural structure belonging to the back-arc extensional area of the Andes in the Mendoza Province (Argentina). The eastern portion of the volcanic structure is covered by a basaltic field of pahoehoe lava flows advanced over more than 180 km from the fissural feeding vents that are aligned with a E-W fault system (Carbonilla fault). Thanks to their widespread extension, these flows represent some of the largest lava flows in the world and the Pampas Onduladas flow can be considered the longest sub-aerial individual lava flow on the Earth surface [1,2]. These gigantic flows propagated over the nearly flat surface of the Pampean foreland, moving on a 0.3 degree slope. The very low viscosity of the olivine basalt lavas, coupled with the inflation process and an extensive system of lava tubes are the most probable explanation for their considerable length. The inflation process likely develop under a steady flow rate sustained for a long time [3]. A thin viscoelastic crust, built up at an early stage, is later inflated by the underlying fluid core, which remains hot and fluid thanks to the thermal-shield effect of the crust. The crust is progressively thickened by accretion from below and spreading is due to the continuous creation of new inflated lobes, which develop at the front of the flow. Certain morphological features are considered to be "fingerprints" of inflation [4, 5, 6]; these include tumuli, lava rises, lava lobes and ridges. All these morphologies are present in the more widespread Payun Matru lava flows that, where they form extensive sheetflows, can reach a maximum thickness of more than 20 meters. After the emplacement of the major flows, a second eruptive cycle involved the Payun Matru volcanic structure. During this stage thick and channelized flows of andesitic and dacitic lavas, accompanied the formation of two trachitic and trachiandesitic strato-volcanoes (Payun Matru and Payun Liso) culminated

  2. Geology of selected lava tubes in the Bend Area, Oregon

    Science.gov (United States)

    Greely, R.

    1971-01-01

    Longitudinal profiles representing 5872.5 m of mapped lava tubes and a photogeologic map relating lava tubes to surface geology, regional structure and topography are presented. Three sets of lava tubes were examined: (1) Arnold Lava Tube System (7km long) composed of collapsed and uncollapsed tube segments and lava ponds, (2) Horse Lava Tube System (11 km long) composed of parallel and anastomosing lava tube segments, and (3) miscellaneous lava tubes. Results of this study tend to confirm the layered lava hypothesis of Ollier and Brown (1965) for lava tube formation; however, there are probably several modes of formation for lava tubes in general. Arnold System is a single series of tubes apparently formed in a single basalt flow on a relatively steep gradient. The advancing flow in which the tubes formed was apparently temporarily halted, resulting in the formation of lava ponds which were inflated and later drained by the lava tube system. Horse System probably formed in multiple, interconnected flows. Pre-flow gradient appears to have been less than for Arnold System, and resulted in meandrous, multiple tube networks.

  3. Early Earth: Lava Floods and Life Opportunity

    Science.gov (United States)

    Astafieva, M. M.

    2017-05-01

    At the earliest stages of the Earth development, in Archean, a large part of the Earth was molten due to active volcanism and intense meteorite bombardment that ended about 4.0 GA. Stopping or weakening of the cosmic bombardment has allowed the planet to cool and form a solid crust. It is from this time geologically documented history of the Earth begins. Accordingly, the earliest Earth rocks are igneous, metamorphic and sedimentary rocks were formed later (the oldest metasedimentary rocks - 3.7-3.85 GA). Therefore, the question of microorganism colonization of lava at the earliest stages of life evolution on the Earth is of paramount importance. A few model objects were chosen for investigation of microbial colonization of getting cold lava floods. Among them Early Protherozoic pillow-lavas of Karelia (2.41 and 2.2 GA) and South Africa (2.22 GA). Modern volcanic glasses of pillow lavas of Mid-Atlantic ridge were used as comparative material.

  4. Magnetic links among lava flows, tuffs and the underground plumbing system in a monogenetic volcano, derived from magnetics and paleomagnetic studies

    Science.gov (United States)

    Urrutia-Fucugauchi, Jaime; Trigo-Huesca, Alfonso; Pérez-Cruz, Ligia

    2012-12-01

    A combined study using magnetics and paleomagnetism of the Toluquilla monogenetic volcano and associated lavas and tuffs from Valsequillo basin in Central Mexico provides evidence on a 'magnetic' link between the lavas, ash tuffs and the underground volcanic conduit system. Paleomagnetic analyses show that the lava and ash tuff carry reverse polarity magnetizations, which correlate with the inversely polarized dipolar magnetic anomaly over the volcano. The magnetizations in the lava and tuff show similar southward declinations and upward inclinations, supporting petrological inferences that the tuff was emplaced while still hot and indicating a temporal correlation for lava and tuff emplacement. Modeling of the dipolar anomaly gives a reverse polarity source magnetization associated with a vertical prismatic body with southward declination and upward inclination, which correlates with the reverse polarity magnetizations in the lava and tuff. The study documents a direct correlation of the paleomagnetic records with the underground magmatic conduit system of the monogenetic volcano. Time scale for cooling of the volcanic plumbing system involves a longer period than the one for the tuff and lava, suggesting that magnetization for the source of dipolar anomaly may represent a long time average as compared to the spot readings in the lava and tuff. The reverse polarity magnetizations in lava and tuff and in the underground source body for the magnetic anomaly are interpreted in terms of eruptive activity of Toluquilla volcano at about 1.3 Ma during the Matuyama reverse polarity C1r.2r chron.

  5. Origin of phenocrysts and compositional diversity in pre-Mazama rhyodacite lavas, Crater Lake, Oregon

    Science.gov (United States)

    Nakada, S.; Bacon, C.R.; Gartner, A.E.

    1994-01-01

    Phenocrysts in porphyritic volcanic rocks may originate in a variety of ways in addition to nucleation and growth in the matrix in which they are found. Porphyritic rhyodacite lavas that underlie the eastern half of Mount Mazama, the High Cascade andesite/dacite volcano that contains Crater Lake caldera, contain evidence that bears on the general problem of phenocryst origin. Phenocrysts in these lavas apparently formed by crystallization near the margins of a magma chamber and were admixed into convecting magma before eruption. About 20 km3 of pre-Mazama rhyodacite magma erupted during a relatively short period between ~400 and 500 ka; exposed pre-Mazama dacites are older and less voluminous. The rhyodacites formed as many as 40 lava domes and flows that can be assigned to three eruptive groups on the basis of composition and phenocryst content. -from Authors

  6. A sinuous tumulus over an active lava tube at Kīlauea Volcano: Evolution, analogs, and hazard forecasts

    Science.gov (United States)

    Orr, Tim R.; Bleacher, Jacob E.; Patrick, Matthew R.; Wooten, Kelly M.

    2015-01-01

    Inflation of narrow tube-fed basaltic lava flows (tens of meters across), such as those confined by topography, can be focused predominantly along the roof of a lava tube. This can lead to the development of an unusually long tumulus, its shape matching the sinuosity of the underlying lava tube. Such a situation occurred during Kīlauea Volcano's (Hawai'i, USA) ongoing East Rift Zone eruption on a lava tube active from July through November 2010. Short-lived breakouts from the tube buried the flanks of the sinuous, ridge-like tumulus, while the tumulus crest, its surface composed of lava formed very early in the flow's emplacement history, remained poised above the surrounding younger flows. At least several of these breakouts resulted in irrecoverable uplift of the tube roof. Confined sections of the prehistoric Carrizozo and McCartys flows (New Mexico, USA) display similar sinuous, ridge-like features with comparable surface age relationships. We contend that these distinct features formed in a fashion equivalent to that of the sinuous tumulus that formed at Kīlauea in 2010. Moreover, these sinuous tumuli may be analogs for some sinuous ridges evident in orbital images of the Tharsis volcanic province on Mars. The short-lived breakouts from the sinuous tumulus at Kīlauea were caused by surges in discharge through the lava tube, in response to cycles of deflation and inflation (DI events) at Kīlauea's summit. The correlation between DI events and subsequent breakouts aided in lava flow forecasting. Breakouts from the sinuous tumulus advanced repeatedly toward the sparsely populated Kalapana Gardens subdivision, destroying two homes and threatening others. Hazard assessments, including flow occurrence and advance forecasts, were relayed regularly to the Hawai'i County Civil Defense to aid their lava flow hazard mitigation efforts while this lava tube was active.

  7. A sinuous tumulus over an active lava tube at Kīlauea Volcano: evolution, analogs, and hazard forecasts

    Science.gov (United States)

    Orr, Tim R.; Bleacher, Jacob E.; Patrick, Matthew R.; Wooten, Kelly M.

    2015-01-01

    Inflation of narrow tube-fed basaltic lava flows (tens of meters across), such as those confined by topography, can be focused predominantly along the roof of a lava tube. This can lead to the development of an unusually long tumulus, its shape matching the sinuosity of the underlying lava tube. Such a situation occurred during Kīlauea Volcano's (Hawai'i, USA) ongoing East Rift Zone eruption on a lava tube active from July through November 2010. Short-lived breakouts from the tube buried the flanks of the sinuous, ridge-like tumulus, while the tumulus crest, its surface composed of lava formed very early in the flow's emplacement history, remained poised above the surrounding younger flows. At least several of these breakouts resulted in irrecoverable uplift of the tube roof. Confined sections of the prehistoric Carrizozo and McCartys flows (New Mexico, USA) display similar sinuous, ridge-like features with comparable surface age relationships. We contend that these distinct features formed in a fashion equivalent to that of the sinuous tumulus that formed at Kīlauea in 2010. Moreover, these sinuous tumuli may be analogs for some sinuous ridges evident in orbital images of the Tharsis volcanic province on Mars. The short-lived breakouts from the sinuous tumulus at Kīlauea were caused by surges in discharge through the lava tube, in response to cycles of deflation and inflation (DI events) at Kīlauea's summit. The correlation between DI events and subsequent breakouts aided in lava flow forecasting. Breakouts from the sinuous tumulus advanced repeatedly toward the sparsely populated Kalapana Gardens subdivision, destroying two homes and threatening others. Hazard assessments, including flow occurrence and advance forecasts, were relayed regularly to the Hawai'i County Civil Defense to aid their lava flow hazard mitigation efforts while this lava tube was active.

  8. Ridge-like lava tube systems in southeast Tharsis, Mars

    Science.gov (United States)

    Zhao, Jiannan; Huang, Jun; Kraft, Michael D.; Xiao, Long; Jiang, Yun

    2017-10-01

    Lava tubes are widely distributed in volcanic fields on a planetary surface and they are important means of lava transportation. We have identified 38 sinuous ridges with a lava-tube origin in southeast Tharsis. The lengths vary between 14 and 740 km, and most of them occur in areas with slopes tubes, including branches, axial cracks, collapsed pits, breakout lobes, and tube-fed lava deltas. Age determination results showed that most of the lava tubes formed in Late Hesperian and were active until the Hesperian-Amazonian boundary. We proposed that these lava tubes formed at relatively low local flow rate, low lava viscosity, and sustained magma supply during a long period. Besides, lava flow inflation is also important in the formation of the ridge-like lava tubes and some associated features. These lava tubes provide efficient lateral pathways for magma transportation over the relatively low topographic slopes in southeast Tharsis, and they are important for the formation of long lava flows in this region. The findings of this study provide an alternative formation mechanism for sinuous ridges on the martian surface.

  9. Rapid fluvial incision of a late Holocene lava flow: Insights from LiDAR, alluvial stratigraphy, and numerical modeling

    Science.gov (United States)

    Sweeney, Kristin; Roering, Joshua J.

    2016-01-01

    Volcanic eruptions fundamentally alter landscapes, paving over channels, decimating biota, and emplacing fresh, unweathered material. The fluvial incision of blocky lava flows is a geomorphic puzzle. First, high surface permeability and lack of sediment should preclude geomorphically effective surface runoff and dissection. Furthermore, past work has demonstrated the importance of extreme floods in driving incision via column toppling and plucking in columnar basalt, but it is unclear how incision occurs in systems where surface blocks are readily mobile. We examine rapid fluvial incision of the Collier lava flow, an andesitic Holocene lava flow in the High Cascades of Oregon. Since lava flow emplacement ∼1600 yr ago, White Branch Creek has incised bedrock gorges up to 8 m deep into the coherent core of the lava flow and deposited >0.2 km3 of sediment on the lava flow surface. Field observation points to a bimodal discharge regime in the channel, with evidence for both annual snowmelt runoff and outburst floods from Collier glacier, as well as historical evidence of vigorous glacial meltwater. To determine the range of discharge events capable of incision in White Branch Creek, we used a mechanistic model of fluvial abrasion. We show that the observed incision implies that moderate flows are capable of both initiating channel formation and sustaining incision. Our results have implications for the evolution of volcanic systems worldwide, where glaciation and/or mass wasting may accelerate fluvial processes by providing large amounts of sediment to otherwise porous, sediment-starved landscapes.

  10. Modeling steam pressure under martian lava flows

    Science.gov (United States)

    Dundas, Colin M.; Keszthelyi, Laszlo P.

    2013-01-01

    Rootless cones on Mars are a valuable indicator of past interactions between lava and water. However, the details of the lava–water interactions are not fully understood, limiting the ability to use these features to infer new information about past water on Mars. We have developed a model for the pressurization of a dry layer of porous regolith by melting and boiling ground ice in the shallow subsurface. This model builds on previous models of lava cooling and melting of subsurface ice. We find that for reasonable regolith properties and ice depths of decimeters, explosive pressures can be reached. However, the energy stored within such lags is insufficient to excavate thick flows unless they draw steam from a broader region than the local eruption site. These results indicate that lag pressurization can drive rootless cone formation under favorable circumstances, but in other instances molten fuel–coolant interactions are probably required. We use the model results to consider a range of scenarios for rootless cone formation in Athabasca Valles. Pressure buildup by melting and boiling ice under a desiccated lag is possible in some locations, consistent with the expected distribution of ice implanted from atmospheric water vapor. However, it is uncertain whether such ice has existed in the vicinity of Athabasca Valles in recent history. Plausible alternative sources include surface snow or an aqueous flood shortly before the emplacement of the lava flow.

  11. Additional Observations of Actively Forming Lava Tubes and Associated Structures, Hawaii

    Science.gov (United States)

    Greeley, Ronald

    1972-01-01

    Extensive changes occurred after the initial observations (Greeley, 1971) of lava tube and channel formation associated with the eruption of Mauna Ulu. Individual vents, which apparently acted somewhat independently, merged by collapse of intervening sections to form an elongate trench. Lava erupted from the summit vent flowed down the trench to the lower end and drained through lava tubes into Alae lava lake. Alae lava lake is in turn drained occasionally by other lava tubes and lava tube networks.

  12. Gusev Rocks Solidified from Lava (3-D)

    Science.gov (United States)

    2006-01-01

    In recent weeks, as NASA's Mars Exploration Rover Spirit has driven through the basin south of 'Husband Hill,' it has been traversing mainly sand and dune deposits. This week, though, Spirit has been maneuvering along the edge of an arc-shaped feature called 'Lorre Ridge' and has encountered some spectacular examples of basaltic rocks with striking textures. This panoramic camera (Pancam) image shows a group of boulders informally named 'FuYi.' These basaltic rocks were formed by volcanic processes and may be a primary constituent of Lorre Ridge and other interesting landforms in the basin. Spirit first encountered basalts at its landing site two years ago, on a vast plain covered with solidified lava that appeared to have flowed across Gusev Crater. Later, basaltic rocks became rare as Spirit climbed Husband Hill. The basaltic rocks that Spirit is now seeing are interesting because they exhibit many small holes or vesicles, similar to some kinds of volcanic rocks on Earth. Vesicular rocks form when gas bubbles are trapped in lava flows and the rock solidifies around the bubbles. When the gas escapes, it leaves holes in the rock. The quantity of gas bubbles in rocks on Husband Hill varies considerably; some rocks have none and some, such as several here at FuYi, are downright frothy. The change in textures and the location of the basalts may be signs that Spirit is driving along the edge of a lava flow. This lava may be the same as the basalt blanketing the plains of Spirit's landing site, or it may be different. The large size and frothy nature of the boulders around Lorre Ridge might indicate that eruptions once took place at the edge of the lava flow, where the lava interacted with the rocks of the basin floor. Scientists hope to learn more as Spirit continues to investigate these rocks. As Earth approaches the Chinese New Year (The Year of the Dog), the Athena science team decided to use nicknames representing Chinese culture and geography to identify rocks and

  13. Gusev Rocks Solidified from Lava (False Color)

    Science.gov (United States)

    2006-01-01

    In recent weeks, as NASA's Mars Exploration Rover Spirit has driven through the basin south of 'Husband Hill,' it has been traversing mainly sand and dune deposits. This week, though, Spirit has been maneuvering along the edge of an arc-shaped feature called 'Lorre Ridge' and has encountered some spectacular examples of basaltic rocks with striking textures. This panoramic camera (Pancam) image shows a group of boulders informally named 'FuYi.' These basaltic rocks were formed by volcanic processes and may be a primary constituent of Lorre Ridge and other interesting landforms in the basin. Spirit first encountered basalts at its landing site two years ago, on a vast plain covered with solidified lava that appeared to have flowed across Gusev Crater. Later, basaltic rocks became rare as Spirit climbed Husband Hill. The basaltic rocks that Spirit is now seeing are interesting because they exhibit many small holes or vesicles, similar to some kinds of volcanic rocks on Earth. Vesicular rocks form when gas bubbles are trapped in lava flows and the rock solidifies around the bubbles. When the gas escapes, it leaves holes in the rock. The quantity of gas bubbles in rocks on Husband Hill varies considerably; some rocks have none and some, such as several here at FuYi, are downright frothy. The change in textures and the location of the basalts may be signs that Spirit is driving along the edge of a lava flow. This lava may be the same as the basalt blanketing the plains of Spirit's landing site, or it may be different. The large size and frothy nature of the boulders around Lorre Ridge might indicate that eruptions once took place at the edge of the lava flow, where the lava interacted with the rocks of the basin floor. Scientists hope to learn more as Spirit continues to investigate these rocks. As Earth approaches the Chinese New Year (The Year of the Dog), the Athena science team decided to use nicknames representing Chinese culture and geography to identify rocks and

  14. Identifying hazards associated with lava deltas

    Science.gov (United States)

    Poland, Michael P.; Orr, Tim R.

    2014-01-01

    Lava deltas, formed where lava enters the ocean and builds a shelf of new land extending from the coastline, represent a significant local hazard, especially on populated ocean island volcanoes. Such structures are unstable and prone to collapse—events that are often accompanied by small explosions that can deposit boulders and cobbles hundreds of meters inland. Explosions that coincide with collapses of the East Lae ‘Apuki lava delta at Kīlauea Volcano, Hawai‘i, during 2005–2007 followed an evolutionary progression mirroring that of the delta itself. A collapse that occurred when the lava–ocean entry was active was associated with a blast of lithic blocks and dispersal of spatter and fine, glassy tephra. Shortly after delta growth ceased, a collapse exposed hot rock to cold ocean water, resulting in an explosion composed entirely of lithic blocks and lapilli. Further collapse of the delta after several months of inactivity, by which time it had cooled significantly, resulted in no recognizable explosion deposit. Seaward displacement and subsidence of the coastline immediately inland of the delta was measured by both satellite and ground-based sensors and occurred at rates of several centimeters per month even after the lava–ocean entry had ceased. The anomalous deformation ended only after complete collapse of the delta. Monitoring of ground deformation may therefore provide an indication of the potential for delta collapse, while the hazard associated with collapse can be inferred from the level of activity, or the time since the last activity, on the delta.

  15. Geologic field-trip guide to Medicine Lake Volcano, northern California, including Lava Beds National Monument

    Science.gov (United States)

    Donnelly-Nolan, Julie M.; Grove, Timothy L.

    2017-08-17

    Medicine Lake volcano is among the very best places in the United States to see and walk on a variety of well-exposed young lava flows that range in composition from basalt to rhyolite. This field-trip guide to the volcano and to Lava Beds National Monument, which occupies part of the north flank, directs visitors to a wide range of lava flow compositions and volcanic phenomena, many of them well exposed and Holocene in age. The writing of the guide was prompted by a field trip to the California Cascades Arc organized in conjunction with the International Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI) quadrennial meeting in Portland, Oregon, in August of 2017. This report is one of a group of three guides describing the three major volcanic centers of the southern Cascades Volcanic Arc. The guides describing the Mount Shasta and Lassen Volcanic Center parts of the trip share an introduction, written as an overview to the IAVCEI field trip. However, this guide to Medicine Lake volcano has descriptions of many more stops than are included in the 2017 field trip. The 23 stops described here feature a range of compositions and volcanic phenomena. Many other stops are possible and some have been previously described, but these 23 have been selected to highlight the variety of volcanic phenomena at this rear-arc center, the range of compositions, and for the practical reason that they are readily accessible. Open ground cracks, various vent features, tuffs, lava-tube caves, evidence for glaciation, and lava flows that contain inclusions and show visible evidence of compositional zonation are described and visited along the route.

  16. Blowing off steam: Tuffisite formation as a regulator for lava dome eruptions

    Directory of Open Access Journals (Sweden)

    Jackie Evan Kendrick

    2016-04-01

    Full Text Available Tuffisites are veins of variably sintered, pyroclastic particles that form in conduits and lava domes as a result of localized fragmentation events during gas-and-ash explosions. Those observed in-situ on the active 2012 lava dome of Volcán de Colima range from voids with intra-clasts showing little movement and interpreted to be failure-nuclei, to sub-parallel lenses of sintered granular aggregate interpreted as fragmentation horizons, through to infilled fractures with evidence of viscous remobilization. All tuffisites show evidence of sintering. Further examination of the complex fracture-and-channel patterns reveals viscous backfill by surrounding magma, suggesting that lava fragmentation was followed by stress relaxation and continued viscous deformation as the tuffisites formed. The natural tuffisites are more permeable than the host andesite, and have a wide range of porosity and permeability compared to a narrower window for the host rock, and gauging from their significant distribution across the dome, we posit that the tuffisite veins may act as important outgassing pathways. To investigate tuffisite formation we crushed and sieved andesite from the lava dome and sintered it at magmatic temperatures for different times. We then assessed the healing and sealing ability by measuring porosity and permeability, showing that sintering reduces both over time. During sintering the porosity-permeability reduction occurs due to the formation of viscous necks between adjacent grains, a process described by the neck-formation model of Frenkel (1945. This process leads the granular starting material to a porosity-permeability regime anticipated for effusive lavas, and which describes the natural host lava as well as the most impervious of natural tuffisites. This suggests that tuffisite formation at Volcán de Colima constructed a permeable network that enabled gas to bleed passively from the magma. We postulate that this progressively reduced

  17. A flexible open-source toolkit for lava flow simulations

    Science.gov (United States)

    Mossoux, Sophie; Feltz, Adelin; Poppe, Sam; Canters, Frank; Kervyn, Matthieu

    2014-05-01

    Lava flow hazard modeling is a useful tool for scientists and stakeholders confronted with imminent or long term hazard from basaltic volcanoes. It can improve their understanding of the spatial distribution of volcanic hazard, influence their land use decisions and improve the city evacuation during a volcanic crisis. Although a range of empirical, stochastic and physically-based lava flow models exists, these models are rarely available or require a large amount of physical constraints. We present a GIS toolkit which models lava flow propagation from one or multiple eruptive vents, defined interactively on a Digital Elevation Model (DEM). It combines existing probabilistic (VORIS) and deterministic (FLOWGO) models in order to improve the simulation of lava flow spatial spread and terminal length. Not only is this toolkit open-source, running in Python, which allows users to adapt the code to their needs, but it also allows users to combine the models included in different ways. The lava flow paths are determined based on the probabilistic steepest slope (VORIS model - Felpeto et al., 2001) which can be constrained in order to favour concentrated or dispersed flow fields. Moreover, the toolkit allows including a corrective factor in order for the lava to overcome small topographical obstacles or pits. The lava flow terminal length can be constrained using a fixed length value, a Gaussian probability density function or can be calculated based on the thermo-rheological properties of the open-channel lava flow (FLOWGO model - Harris and Rowland, 2001). These slope-constrained properties allow estimating the velocity of the flow and its heat losses. The lava flow stops when its velocity is zero or the lava temperature reaches the solidus. Recent lava flows of Karthala volcano (Comoros islands) are here used to demonstrate the quality of lava flow simulations with the toolkit, using a quantitative assessment of the match of the simulation with the real lava flows. The

  18. Field Detection of Chemical Assimilation in A Basaltic Lava Flow

    Science.gov (United States)

    Young, K. E.; Bleacher, J. E.; Needham, D. H.; Evans, C. A.; Whelley, P. L.; Scheidt, S. P.; Williams, D. A.; Rogers, A. D.; Glotch, T.

    2017-01-01

    Lava channels are features seen throughout the inner Solar System, including on Earth, the Moon, and Mars. Flow emplacement is therefore a crucial process in the shaping of planetary surfaces. Many studies, including some completed by members of this team at the December 1974 lava flow, have investigated the dynamics of lava flow emplacement, both on Earth and on the Moon and how pre-flow terrain can impact final channel morphology, but far fewer have focused on how the compositional characteristics of the substrate over which a flow was em-placed influenced its final flow morphology. Within the length of one flow, it is common for flows to change in morphology, a quality linked to rheology (a function of multiple factors including viscosi-ty, temperature, composition, etc.). The relationship between rheology and temperature has been well-studied but less is known about the relationship between an older flow's chemistry and how the interaction between this flow and the new flow might affect lava rheology and therefore emplacement dynamics. Lava erosion. Through visual observations of active terrestrial flows, mechanical erosion by flowing lava has been well-documented. Lava erosion by which flow composition is altered as the active lava melts and assimilates the pre-flow terrain over which it moves is also hypothesized to affect channel formation. However, there is only one previous field study that geochemically documents the process in recent basaltic flow systems.

  19. Documenting Chemical Assimilation in a Basaltic Lava Flow

    Science.gov (United States)

    Young, K. E.; Bleacher, J. E.; Needham, D. H.; Evans, C.; Whelley, P. L.; Scheidt, S.; Williams, D.; Rogers, A. D.; Glotch, T.

    2017-01-01

    Lava channels are features seen throughout the inner Solar System, including on Earth, the Moon, and Mars. Flow emplacement is therefore a crucial process in the shaping of planetary surfaces. Many studies have investigated the dynamics of lava flow emplacement, both on Earth and on the Moon [1,2,3] but none have focused on how the compositional and structural characteristics of the substrate over which a flow was emplaced influenced its final flow morphology. Within the length of one flow, it is common for flows to change in morphology, a quality linked to lava rheology (a function of multiple factors including viscosity, temperature, composition, etc.). The relationship between rheology and temperature has been well-studied [4,5,6] but less is understood about the relationship between a pre-flow terrain's chemistry and how the interaction between this flow and the new flow might affect lava rheology and therefore emplacement dynamics. Lava erosion. Through visual observations of active terrestrial flows, lava erosion has been well-documented [i.e. 7,8,9,10]. Lava erosion is the process by which flow composition is altered as the active lava melts and assimilates the pre-flow terrain over which it moves. Though this process has been observed, there is only one instance of where it was been geochemically documented.

  20. Olympus Mons, Mars: Constraints on Lava Flow Silica Composition

    Science.gov (United States)

    Kirshner, M.; Jurdy, D. M.

    2016-12-01

    Olympus Mons, Mars, the largest known volcano in our solar system, contains numerous enigmatic lava flow features. Lava tubes have received attention as their final morphologies may offer habitable zones for both native life and human exploration. Such tubes were formed through mechanisms involving several volatile species with significant silica content. Olympus Mons, a shield volcano, might be expected to have flows with silica content similar to that of terrestrial basaltic flows. However, past investigations have estimated a slightly more andesitic composition. Data pertaining to lava tubes such as flow width and slope are collected from the Mars Reconnaissance Orbiter's Context Camera, Mars Odyssey's THEMIS instrument, and Mars Express' HRSC instrument. Compiling this data in GIS software allows for extensive mapping and analysis of Olympus Mons' seemingly inactive flow features. A rheological analysis performed on 62 mapped lava tubes utilizes geometric parameters inferred from mapping. Lava was modeled as a Bingham fluid on an inclined plane, allowing for the derivation of lava yield stress. Percent silica content was calculated for each of the 62 mapped flows using a relationship derived from observations of terrestrial lava yield strengths and corresponding silica composition. Results indicate that lava tube flows across Olympus Mons were on average basaltic in nature, occasionally reaching into the andesitic classification: percent silica content is 51% on average and ranges between roughly 40% and 57%.

  1. Lava inundation zone maps for Mauna Loa, Island of Hawaiʻi, Hawaii

    Science.gov (United States)

    Trusdell, Frank A.; Zoeller, Michael H.

    2017-10-12

    Lava flows from Mauna Loa volcano, on the Island of Hawaiʻi, constitute a significant hazard to people and property. This report addresses those lava flow hazards, mapping 18 potential lava inundation zones on the island.

  2. The Longevity of Lava Dome Eruptions

    CERN Document Server

    Wolpert, Robert L; Calder, Eliza S

    2015-01-01

    Understanding the duration of past, on-going and future volcanic eruptions is an important scientific goal and a key societal need. We present a new methodology for forecasting the duration of on-going and future lava dome eruptions based on a database (DomeHaz) recently compiled by the authors. The database includes duration and composition for 177 such eruptions, with "eruption" defined as the period encompassing individual episodes of dome growth along with associated quiescent periods during which extrusion pauses but unrest continues. In a key finding we show that probability distributions for dome eruption durations are both heavy-tailed and composition-dependent. We construct Objective Bayes statistical models featuring heavy-tailed Generalized Pareto distributions with composition-specific parameters to make forecasts about the durations of new and on-going eruptions that depend on both eruption duration-to-date and composition. Our Bayesian predictive distributions reflect both uncertainty about mode...

  3. Moonshot Laboratories' Lava Relief Google Mapping Project

    Science.gov (United States)

    Brennan, B.; Tomita, M.

    2016-12-01

    The Moonshot Laboratories were conceived at the University Laboratory School (ULS) on Oahu, Hawaii as way to develop creative problem solvers able to resourcefully apply 21st century technologies to respond to the problems and needs of their communities. One example of this was involved students from ULS using modern mapping and imaging technologies to assist peers who had been displaced from their own school in Pahoe on the Big Island of Hawaii. During 2015, lava flows from the eruption of Kilauea Volcano were slowly encroaching into the district of Puna in 2015. The lava flow was cutting the main town of Pahoa in half, leaving no safe routes of passage into or out of the town. One elementary school in the path of the flow was closed entirely and a new one was erected north of the flow for students living on that side. Pahoa High School students and teachers living to the north were been forced to leave their school and transfer to Kea'au High School. These students were separated from friends, family and the community they grew up in and were being thrust into a foreign environment that until then had been their local rival. Using Google Mapping technologies, Moonshot Laboratories students created a dynamic map to introduce the incoming Pahoa students to their new school in Kea'au. Elements included a stylized My Maps basemap, YouTube video descriptions of the building, videos recorded by Google Glass showing first person experiences, and immersive images of classrooms were created using 360 cameras. During the first day of orientation at Kea'au for the 200 Pahoa students, each of them were given a tablet to view the map as they toured and got to know their new campus. The methods and technologies, and more importantly innovative thinking, used to create this map have enormous potential for how to educate all students about the world around us, and the issues facing it. http://www.moonshotincubator.com/

  4. Detection of Intact Lava Tubes at Marius Hills on the Moon by SELENE (Kaguya) Lunar Radar Sounder

    Science.gov (United States)

    Kaku, T.; Haruyama, J.; Miyake, W.; Kumamoto, A.; Ishiyama, K.; Nishibori, T.; Yamamoto, K.; Crites, Sarah T.; Michikami, T.; Yokota, Y.; Sood, R.; Melosh, H. J.; Chappaz, L.; Howell, K. C.

    2017-10-01

    Intact lunar lava tubes offer a pristine environment to conduct scientific examination of the Moon's composition and potentially serve as secure shelters for humans and instruments. We investigated the SELENE Lunar Radar Sounder (LRS) data at locations close to the Marius Hills Hole (MHH), a skylight potentially leading to an intact lava tube, and found a distinctive echo pattern exhibiting a precipitous decrease in echo power, subsequently followed by a large second echo peak that may be evidence for the existence of a lava tube. The search area was further expanded to 13.00-15.00°N, 301.85-304.01°E around the MHH, and similar LRS echo patterns were observed at several locations. Most of the locations are in regions of underground mass deficit suggested by GRAIL gravity data analysis. Some of the observed echo patterns are along rille A, where the MHH was discovered, or on the southwest underground extension of the rille.

  5. Inverse Dipolar Magnetic Anomaly Over the Volcanic Cone Linked to Reverse Polarity Magnetizations in Lavas and Tuffs - Implications for the Conduit System

    Science.gov (United States)

    Fucugauchi, J. U.; Perez-Cruz, L. L.; Trigo-Huesca, A.

    2012-12-01

    A combined magnetics and paleomagnetic study of Toluquilla monogenetic volcano and associated lavas and tuffs from Valsequillo basin in Central Mexico provides evidence on a magnetic link between lavas, ash tuffs and the underground volcanic conduit system. Paleomagnetic analyses show that lavas and ash tuffs carry reverse polarity magnetizations, which correlate with the inversely polarized dipolar magnetic anomaly over the volcano. The magnetizations in the lava and tuff show similar southward declinations and upward inclinations, supporting petrological inferences that the tuff was emplaced while still hot and indicating a temporal correlation for lava and tuff emplacement. Conduit geometry is one of the important controlling factors in eruptive dynamics of basaltic volcanoes. However volcanic conduits are often not, or only partly, exposed. Modeling of the dipolar anomaly gives a reverse polarity source magnetization associated with a vertical prismatic body with southward declination and upward inclination, which correlates with the reverse polarity magnetizations in the lava and tuff. The study documents a direct correlation of the paleomagnetic records with the underground magmatic conduit system of the monogenetic volcano. Time scale for cooling of the volcanic plumbing system involves a longer period than the one for the tuff and lava, suggesting that magnetization for the source of dipolar anomaly may represent a long time average as compared to the spot readings in the lava and tuff. The reverse polarity magnetizations in lava and tuff and in the underground source body for the magnetic anomaly are interpreted in terms of eruptive activity of Toluquilla volcano at about 1.3 Ma during the Matuyama reverse polarity C1r.2r chron.

  6. Red Hot: Determining the Physical Properties of Lava Lake Skin

    Science.gov (United States)

    Ford, C.; Lev, E.

    2015-12-01

    Lava lakes are the surface expression of conduits that bring magma to the mouth of a volcano from deep within the earth. Time-lapse footage from a thermal imaging camera at Halema'uma'u lake at Kilauea volcano, Hawaii was used to investigate the cooling rate of the lava lake's surface. The data was then combined with an analytical model of lava flow cooling to constrain the porosity of the lava lake skin. The data was processed to account for the influence that the camera's position relative to the lake had on the image geometry and the recorded temperature values. We examined lake cooling in two separate scenarios: First, we calculated the cooling rate of the skin immediately after large gas bubbles burst at the lake's surface. Second, the temperature of the skin was measured as a function of distance from molten spreading centers (cracks) on the surface, and then converted to cooling as a function of the skin's age using the local lake surface velocity. The resulting cooling time-series were compared against cooling curves produced by a model that simulates lava flow cooling based on a myriad of physical factors. We performed quantitative data analysis to determine the approximate porosity of the lava lake skin. Preliminary comparisons reveal that the calculated cooling rates most closely correspond to the cooling curves that were produced with a lava porosity value of at least 80%.

  7. Improvement of a 2D numerical model of lava flows

    Science.gov (United States)

    Ishimine, Y.

    2013-12-01

    I propose an improved procedure that reduces an improper dependence of lava flow directions on the orientation of Digital Elevation Model (DEM) in two-dimensional simulations based on Ishihara et al. (in Lava Flows and Domes, Fink, JH eds., 1990). The numerical model for lava flow simulations proposed by Ishihara et al. (1990) is based on two-dimensional shallow water model combined with a constitutive equation for a Bingham fluid. It is simple but useful because it properly reproduces distributions of actual lava flows. Thus, it has been regarded as one of pioneer work of numerical simulations of lava flows and it is still now widely used in practical hazard prediction map for civil defense officials in Japan. However, the model include an improper dependence of lava flow directions on the orientation of DEM because the model separately assigns the condition for the lava flow to stop due to yield stress for each of two orthogonal axes of rectangular calculating grid based on DEM. This procedure brings a diamond-shaped distribution as shown in Fig. 1 when calculating a lava flow supplied from a point source on a virtual flat plane although the distribution should be circle-shaped. To improve the drawback, I proposed a modified procedure that uses the absolute value of yield stress derived from both components of two orthogonal directions of the slope steepness to assign the condition for lava flows to stop. This brings a better result as shown in Fig. 2. Fig. 1. (a) Contour plots calculated with the original model of Ishihara et al. (1990). (b) Contour plots calculated with a proposed model.

  8. Elevated Kin-Directed Altruism Emerges in Childhood and Is Linked to Feminine Gender Expression in Samoan Fa'afafine: A Retrospective Study.

    Science.gov (United States)

    VanderLaan, Doug P; Petterson, Lanna J; Vasey, Paul L

    2017-01-01

    Androphilia refers to sexual attraction toward adult males, whereas gynephilia refers to sexual attraction toward adult females. The kin selection hypothesis posits that androphilic males help kin increase their reproductive output via kin-directed altruism, thus offsetting their own lowered reproduction and contributing to the fitness of genes underpinning male androphilia. Support for this hypothesis has been garnered in several Samoan studies showing that feminine androphilic males (known locally as fa'afafine) report elevated willingness to invest in nieces and nephews in adulthood. Also, recalled childhood kin attachment and concern for kin's well-being are elevated among Canadian androphilic males (i.e., gay men) and positively associated with childhood feminine gender expression. This study examined whether these childhood patterns were cross-culturally consistent and associated with adulthood kin-directed altruism in a Samoan sample. Samoan gynephilic men, androphilic women, and fa'afafine (N = 470) completed measures of recalled childhood kin attachment and concern for the well-being of kin, recalled childhood gender expression, and willingness in adulthood to invest in nieces and nephews. Fa'afafine recalled elevated anxiety due to separation from kin relative to men and elevated concern for kin's well-being relative to both men and women. Within groups, these characteristics were most robustly associated with childhood feminine gender expression and willingness in adulthood to invest in nieces and nephews among fa'afafine. These findings are consistent with the kin selection hypothesis and the adaptive feminine phenotype model, which proposes that a disposition toward elevated kin-directed altruism among androphilic males is associated with feminine gender expression.

  9. Rift-plume interaction reveals multiple generations of recycled oceanic crust in Azores lavas

    Science.gov (United States)

    Béguelin, Paul; Bizimis, Michael; Beier, Christoph; Turner, Simon

    2017-12-01

    We present 176Hf/177Hf isotope ratios on 41 previously well-characterized subaerial and submarine samples from the Azores islands of São Miguel, Terceira, Graciosa, Faial, Pico and the João de Castro seamount (on the Terceira Rift). In εNd-εHf isotope space all Azores lavas fall below the mantle array reference line and do not overlap the proximal Atlantic MORB. Lavas from São Miguel and João de Castro form two distinct and well defined arrays extending below the mantle array, which has not been previously documented in other oceanic magmatic provinces. The Nd-Hf isotope compositions of João de Castro overlap those of HIMU type lavas, yet they lack the characteristically radiogenic Pb isotope ratios of HIMU. The combined Nd-Hf-Pb-Sr isotope systematics of both São Miguel and João de Castro endmembers can be explained by recycling of a single package of heterogeneous oceanic crust ranging from D-MORB to E-MORB in composition, with an age between 2.5 and 3.0 Ga, with no requirement for parent-daughter ratio modification during subduction. In contrast the Nd-Hf-Pb isotope systematics of lavas from São Jorge, Terceira, Graciosa, Pico and Faial are consistent with the presence of younger (<700 Ma) recycled crust that underwent low-temperature alteration and dehydration during subduction. There is no evidence in the erupted lavas for direct mixing between these two generations of recycled material within the plume. These data suggest that old recycling age and absence of sediments along with recycled oceanic crust are both required to develop isotopic compositions below the mantle array in εNd-εHf space. Our modeling shows that the compositional variability of erupted MORB is large enough that, given enough time, they can generate a wide range of isotope compositions such as observed in OIB. Lastly, lava compositions along the Terceira rift can be explained by a westward asthenospheric flux along a tilted lithosphere/asthenosphere boundary, where fertile

  10. The Feagaiga and Faife'au 'Kids' (FKs): An Examination of the Experiences of Parsonage Children of the Samoan Congregational Denomination in New Zealand.

    Science.gov (United States)

    Muaiava, Sadat Petelo

    2017-03-01

    This article examines the experiences of faife'au 'kids' (clergy children) of the Samoan Congregational Christian Church denomination in New Zealand. The paper investigates the effects the indigenous concept of feagaiga (covenant) has on faife'au kids (FKs) parsonage experiences. Additionally, the Eurocentric concept of 'tagata'ese' (stranger) is also investigated. As part of a master's research study, Talanoa sessions were conducted with eight FKs of the Congregational denomination in New Zealand. Participants were mainly from the Wellington and Auckland regions.

  11. Eruption mechanisms and short duration of large rhyolitic lava flows of Yellowstone

    Science.gov (United States)

    Loewen, Matthew W.; Bindeman, Ilya N.; Melnik, Oleg E.

    2017-01-01

    Large-volume effusive rhyolite lava flows are a common but poorly understood occurrence from silicic volcanic centers. We integrate characterization of lava flow topographic morphology and petrographic textures and zoning of crystals with physical models of viscous fluid flow in order to interpret the eruption durations and discharge rates for the most recent effusive volcanic eruptions from Yellowstone. These large-volume (10-70 km3) crystal-poor rhyolite lavas erupted within the Yellowstone caldera as 100-200 m thick flows and have a cumulative erupted volume of 650 km3 that is similar to less frequent caldera-forming events, but occur as individual eruptions spread over ∼100 ka. Most of this work is focused on the axisymmetric 124 ka, ∼50 km3 Summit Lake flow. We examined crystallinity, major and trace element concentrations, oxygen and hydrogen isotopic values, and quartz morphology and zoning in samples from the center to margin of this flow. Water contents down to 0.1 wt.% and δD values of - 110 ‰ are low and require closed-system degassing until near-surface lithostatic pressure, while major elements are consistent with water-undersaturated pre-eruptive storage and crystallization at ∼4-8 km depth. We found some evidence for subtle km-scale zoning within the lavas but describe significant microscopic scale compositional diversity including sharp boundaries between high-Ti cores and ∼200 μm thick rims on quartz phenocrysts. Embayed quartz external morphology and rim growth may be the result of undercooling during coalescence of magma bodies during shallow transport between dikes and sills. Modeling the emplacement of the lava flow as a simple viscous fluid suggests that emplacement of rhyolite lava at ∼800 °C occurred over ∼2 to 5 yrs with high discharge rates >100 m3/s. Such high magma discharge rates are accommodated through ∼6 km-long fissures that allow for slower magma ascent velocities of 10 yr flow durations and significant cooling

  12. The origin of Venusian channels: Modelling of thermal erosion by lava

    Science.gov (United States)

    Bussey, D. B. J.; Sorensen, S-A.; Guest, J. E.

    1993-01-01

    Magellan imagery has revealed that channels, apparently volcanic in origin, are abundant on the surface of Venus. There has been much debate about the origin of these channels. Are they the result of erosional (either thermal or mechanical) or constructional processes? A common characteristic of the simple sinuous channels is that they show evidence of erosion near their source and then become purely constructional, forming levees and in some cases roofing over completely. One method of showing that thermal erosion is capable of producing the type of channels seen is to use computer modeling incorporating the physical conditions on Venus and the physical characteristics of the different types of lava that may have been erupted. It is possible to calculate, relatively easily, two channel parameters. The first is the erosion rate, which combined with eruption duration, gives depth. The second is for how long after leaving the source the erupted lava will continue to be capable of thermal erosion before constructional processes dominate. Making assumptions about the rheology of the lava (e.g., assume it behaves as a Bingham plastic) along with the slope angle yields a flow velocity and therefore a distance over which thermal erosion will take place. Due to the resolution (both vertical and horizontal) of the Magellan altimetric data, the distance from the source that the channel is erosional can be much more accurately measured than the depth of the channel. This will remain the case until stereo imagery becomes available for large areas of the planet.

  13. Debris Flows Associated With Lava Extrusion at Three Stratocones; Cleveland, Pavlof (Alaska) and Stromboli (Italy)

    Science.gov (United States)

    van Manen, S.; Dehn, J.

    2008-12-01

    Debris flows that occur contemporaneously with lava flow extrusion have been observed visually, with handheld thermal infrared cameras and in Advanced Very High Resolution Radiometer (AVHRR) satellite data at Stromboli, Cleveland and Pavlof. At Pavlof these debris flows can also be identified in the seismic record. These basaltic equivalents of block and ash flows are low energy, low velocity, low temperature (200- 300° C) with varying grain sizes. Deposits of these flows show little or no sorting. They originate from the 'A'a× flow front but form a cohesive flow with minor elutriation of ash. Further downslope they precede and underly lava flows, partly guiding the path of later flows. At Pavlof and Cleveland they lie on top of layers of snow and ice. At Pavlof this has resulted in these flows feeding lahars, at Cleveland they form an insulating layer between the snow and the active lava flow. Field evidence has shown that the snow layer can even be present years after the emplacement of the lava flow on top of the debris flow. This suggests that this layering is an integral part of the structure of the volcanic cone, providing preferred failure planes and resulting in instability. In the future this could result in either failure of large parts of the volcanic edifice of these volcanoes or large scale phreato-magmatic explosions. The handheld thermal imagery of these debris flows obtained on Stromboli will provide a clearer insight into their thermal regime, and when combined with satellite and seismic data, a hazard assessment of these flows can be made.

  14. The Anatomy of the Blue Dragon: Changes in Lava Flow Morphology and Physical Properties Observed in an Open Channel Lava Flow as a Planetary Analogue

    Science.gov (United States)

    Sehlke, A.; Kobs Nawotniak, S. E.; Hughes, S. S.; Sears, D. W.; Downs, M. T.; Whittington, A. G.; Lim, D. S. S.; Heldmann, J. L.

    2017-10-01

    We present the relationship of lava flow morphology and the physical properties of the rocks based on terrestrial field work, and how this can be applied to infer physical properties of lunar lava flows.

  15. Plateaus and Sinuous Ridges as the Fingerprints of Lava Flow Inflation in the Eastern Tharsis Plains of Mars

    Science.gov (United States)

    Bleacher, Jacob E.; Orr, Tim R.; de Wet, Andrew P.; Zimbelman, James R.; Hamilton, Christopher W.; Garry, W. Brent; Crumpler, Larry S.; Williams, David A.

    2017-01-01

    The Tharsis Montes rift aprons are composed of outpourings of lava from chaotic terrains to the northeast and southwest flank of each volcano. Sinuous and branching channel networks that are present on the rift aprons suggest the possibility of fluvial processes in their development, or erosion by rapidly emplaced lavas, but the style of lava flow emplacement throughout rift apron development is not clearly understood. To better characterize the style of lava emplacement and role of fluvial processes in rift apron development, we conducted morphological mapping of the Pavonis Mons southwest rift apron and the eastern Tharsis plains using images from the High Resolution Imaging Science Experiment (HiRISE), Mars Orbiter Camera (MOC), Context Camera (CTX), Thermal Emission Imaging System (THEMIS), and High Resolution Stereo Camera (HRSC) along with the Mars Orbiter Laser Altimeter (MOLA) Precision Experiment Data Records (PEDRs) and gridded data. Our approach was to: (1) search for depositional fans at the slope break between the rift apron and adjacent low slope plains; (2) determine if there is evidence that previously formed deposits might have been buried by plains units; (3) characterize the Tharsis plains morphologies east of Pavonis Mons; and (4) assess their relationship to the rift apron units. We have not identified topographically significant depositional fans, nor did we observe evidence to suggest that plains units have buried older rift apron units. Flow features associated with the rift apron are observed to continue across the slope break onto the plains. In this area, the plains are composed of a variety of small fissures and low shield vents around which broad channel-fed and tube-fed flows have been identified. We also find broad, flat-topped plateaus and sinuous ridges mixed among the channels, tubes and vents. Flat-topped plateaus and sinuous ridges are morphologies that are analogous to those observed on the coastal plain of Hawai'i, where lava

  16. Plateaus and sinuous ridges as the fingerprints of lava flow inflation in the Eastern Tharsis Plains of Mars

    Science.gov (United States)

    Bleacher, Jacob E.; Orr, Tim; de Wet, Andrew P.; Zimbelman, James R.; Hamilton, Christopher W.; Garry, W. Brent; Crumpler, Larry S.; Williams, David A.

    2017-01-01

    The Tharsis Montes rift aprons are composed of outpourings of lava from chaotic terrains to the northeast and southwest flank of each volcano. Sinuous and branching channel networks that are present on the rift aprons suggest the possibility of fluvial processes in their development, or erosion by rapidly emplaced lavas, but the style of lava flow emplacement throughout rift apron development is not clearly understood. To better characterize the style of lava emplacement and role of fluvial processes in rift apron development, we conducted morphological mapping of the Pavonis Mons southwest rift apron and the eastern Tharsis plains using images from the High Resolution Imaging Science Experiment (HiRISE), Mars Orbiter Camera (MOC), Context Camera (CTX), Thermal Emission Imaging System (THEMIS), and High Resolution Stereo Camera (HRSC) along with the Mars Orbiter Laser Altimeter (MOLA) Precision Experiment Data Records (PEDRs) and gridded data. Our approach was to: (1) search for depositional fans at the slope break between the rift apron and adjacent low slope plains; (2) determine if there is evidence that previously formed deposits might have been buried by plains units; (3) characterize the Tharsis plains morphologies east of Pavonis Mons; and (4) assess their relationship to the rift apron units. We have not identified topographically significant depositional fans, nor did we observe evidence to suggest that plains units have buried older rift apron units. Flow features associated with the rift apron are observed to continue across the slope break onto the plains. In this area, the plains are composed of a variety of small fissures and low shield vents around which broad channel-fed and tube-fed flows have been identified. We also find broad, flat-topped plateaus and sinuous ridges mixed among the channels, tubes and vents. Flat-topped plateaus and sinuous ridges are morphologies that are analogous to those observed on the coastal plain of Hawai‘i, where lava

  17. Rheology of lava flows on Mercury: An analog experimental study

    Science.gov (United States)

    Sehlke, A.; Whittington, A. G.

    2015-11-01

    We experimentally determined the rheological evolution of three basaltic analog compositions appropriate to Mercury's surface, during cooling, and crystallization. Investigated compositions are an enstatite basalt, and two magnesian basalts representing the compositional end-members of the northern volcanic plains with 0.19 wt % (NVP) and 6.26 wt % Na2O (NVP-Na). The viscosity-strain rate dependence of lava was quantified using concentric cylinder viscometry. We measured the viscosities of the crystal-free liquids from 1600°C down to the first detection of crystals. Liquidus temperatures of the three compositions studied are around 1360°C, and all three compositions are more viscous than Hawaiian basalt at the same temperature. The onset of pseudoplastic behavior was observed at crystal fractions ~0.05 to 0.10, which is consistent with previous studies on mafic lavas. We show that all lavas develop detectable yield strengths at crystal fractions around 0.20, beyond which the two-phase suspensions are better described as Herschel-Bulkley fluids. By analogy with the viscosity-strain rate conditions at which the pahoehoe to `a`a transition occurs in Kilauea basalt, this transition is predicted to occur at ~1260 ± 10°C for the enstatite basalt, at ~1285 ± 20°C for the NVP, and at ~1240 ± 40°C for the NVP-Na lavas. Our results indicate that Mercury lavas are broadly similar to terrestrial ones, which suggests that the extensive smooth lava plains of Mercury could be due to large effusion rates (flood basalts) and not to unusually fluid lavas.

  18. The Influence of Topographic Obstacles on Basaltic Lava Flow Morphologies

    Science.gov (United States)

    von Meerscheidt, H. C.; Brand, B. D.; deWet, A. P.; Bleacher, J. E.; Hamilton, C. W.; Samuels, R.

    2014-12-01

    Smooth pāhoehoe and jagged ´áā represent two end-members of a textural spectrum that reflects the emplacement characteristics of basaltic lava flows. However, many additional textures (e.g., rubbly and slabby pāhoehoe) reflect a range of different process due to lava flow dynamics or interaction with topography. Unfortunately the influence of topography on the distribution of textures in basaltic lava flows is not well-understood. The 18 ± 1.0 ka Twin Craters lava flow in the Zuni-Bandera field (New Mexico, USA) provides an excellent site to study the morphological changes of a lava flow that encountered topographic obstacles. The flow field is 0.2-3.8 km wide with a prominent central tube system that intersects and wraps around a 1000 m long ridge, oriented perpendicular to flow. Upstream of the ridge, the flow has low-relief inflation features extending out and around the ridge. This area includes mildly to heavily disrupted pāhoehoe with interdispersed agglutinated masses, irregularly shaped rubble and lava balls. Breakouts of ´áā and collapse features are also common. These observations suggest crustal disruption due to flow-thickening upstream from the ridge and the movement of lava out and around the obstacle. While the ridge influenced the path of the tube, which wraps around the southern end of the ridge, the series of collapse features and breakouts of ´áā along the tube system are more likely a result of changes in flux throughout the tube system because these features are found both upstream and downstream of the obstacle. This work demonstrates that topography can significantly influence the formation history and surface disruption of a flow field, and in some cases the influence of topography can be separated from the influences of changes in flux along a tube system.

  19. High-resolution Digital Mapping of Historical Lava Flows as a Test-bed for Lava Flow Models

    Science.gov (United States)

    Pyle, D. M.; Parks, M.; Nomikou, P.; Mather, T. A.; Simou, E.; Kalnins, L. M.; Paulatto, M.; Watts, A. B.

    2013-12-01

    Quantitative analysis of high-resolution lava flow morphology can improve our understanding of past effusive eruptions by providing insight into eruptive processes and the rheological properties of erupted magmas. We report the results of an ongoing investigation into the young dacite lava flows of the Kameni islands, Santorini volcano, Greece, which were emplaced during both subaerial and shallow submarine eruptions over the past 3000 years. Historical eruptions of the Kameni islands since 1866 have been very carefully documented in contemporaneous scientific reports. Eruptions since 1573 appear to be time-predictable, with a close relationship between eruption length, the size of extruded lava domes, and the time elapsed since the previous eruption. A new NERC - Airborne Survey and Research Facility LiDAR survey of the Kameni islands was completed in May 2012, using a Leica ALS50 Airborne Laser Scanner mounted on a Dornier 228 aircraft. The topographic surface was mapped at an average point density of 2.1 points per square metre, and covers the entire extent of the youngest subaerial lava flow fields on Santorini. A 2-m DEM derived from the 2012 LiDAR dataset was merged with a 5-m resolution bathymetric grid, based on multibeam surveys carried out by the Hellenic Centre for Marine Research, during cruises in 2001 and 2006, using a SEABEAM 2120 hull-mounted swath system. The resultant grid provides the first high resolution map of both subaerial and submarine historic lava flows emplaced in the centre of the Santorini caldera, and includes several previously unidentified submarine flows and cones. Attribute maps were used to delineate and identify discrete lava flows both onshore and offshore; and morphometric profiles were used to compute accurate volumetric estimates for each of the historic flows, and to determine bulk rheological properties of the lavas, assuming a Bingham rheology. This ongoing work will improve our analysis of the relationship between

  20. Chasing lava: a geologist's adventures at the Hawaiian Volcano Observatory

    Science.gov (United States)

    Duffield, Wendell A.

    2003-01-01

    A lively account of the three years (1969-1972) spent by geologist Wendell Duffield working at the Hawaiian Volcano Observatory at Kilauea, one of the world's more active volcanoes. Abundantly illustrated in b&w and color, with line drawings and maps, as well. Volcanologists and general readers alike will enjoy author Wendell Duffield's report from Kilauea--home of Pele, the goddess of fire and volcanoes. Duffield's narrative encompasses everything from the scientific (his discovery that the movements of cooled lava on a lava lake mimic the movements of the earth's crust, providing an accessible model for understanding plate tectonics) to the humorous (his dog's discovery of a snake on the supposedly snake-free island) to the life-threatening (a colleague's plunge into molten lava). This charming account of living and working at Kilauea, one of the world's most active volcanoes, is sure to be a delight.

  1. Biofilter performance of pine nuggets and lava rock as media.

    Science.gov (United States)

    Akdeniz, Neslihan; Janni, Kevin A; Salnikov, Ilya A

    2011-04-01

    Wood chips and bark mulch are commonly used biofilter media because they are generally locally available and inexpensive. Nevertheless, these organic materials degrade and require replacement every 2-5 years. In this study, airflow characteristics and gas reduction efficiencies of two alternative biofilter media (pine nuggets and lava rock) with high porosity and potentially longer service lives were evaluated at three empty bed contact times (1, 3, and 5s) and two moisture levels (82% and 90% relative humidity). The lava rock had a lower pressure drop across the media and maintained higher media depth. Gas reduction efficiencies were highest for lava rock at 5s empty bed contact time and 90% humidity. The reduction efficiencies at these conditions were 56%, 88%, 87%, 25%, and 0.7% for ammonia, hydrogen sulfide, total reduced sulfur, methane and nitrous oxide, respectively. Odor reduction up to 48% was observed but was not consistent. Copyright © 2011 Elsevier Ltd. All rights reserved.

  2. Deformation at Lava Lake Volcanoes: Lessons from Karthala

    Science.gov (United States)

    Biggs, J.; Rust, A.; Owens, C.

    2014-12-01

    To remain hot, permanent lava lakes require a continuous connection to a magma reservoir. Depending on the state of the conduit, changes in magma pressure could result in changes in the lake level (hydraulic head) or be accommodated elastically leading to surface deformation. Observing deformation is therefore key to understanding the plumbing system associated with lava lakes. However, the majority of the world's lava lakes lie in difficult socio-economic or remote locations meaning that there are few ground-based observations, and it is often necessary to rely on satellite imagery. Karthala volcano experienced a sequence of eruptions in April 2005, Nov 2005, May 2006 and Jan 2007. The first 3 took place at the Choungou Chahale crater, which typically contains either a water or lava lake; the last formed a new pit crater to the north. Satellite thermal imagery (Hirn et al, 2008) does not show an anomaly during the first eruption, which had a phreatomagmatic component, but large thermal anomalies, associated with an ephemeral lava lake were detected during the Nov 2005 and May 2006 eruptions. The final eruption produced a smaller anomaly attributed to a minor lava flow. Here we present InSAR observations from 2004-2010. We find no significant deformation associated with the first three eruptions, but the January 2007 eruption was associated with ~25 cm of deformation near the volcano's summit, characteristic of a dyke intrusion aligned with the northern rift zone. We also observe an unusual pattern deformation along the coast which may be attributed to rapid settling of soft sediment or recent volcanic deposits triggered by seismic activity. We propose that the first eruption cleared the reservoir-summit connection and interacted with the water in Choungou Chahale. The following eruptions formed a lava lake, but without causing deformation. By the final eruption, the conduit had become blocked and magma intruded along the rift zone causing deformation but no

  3. The Active Lava Flows of Kilauea Volcano, Hawaii

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 8; Issue 6. The Active Lava Flows of Kilauea Volcano, Hawaii. Hetu Sheth. General Article Volume 8 Issue 6 June 2003 pp 24-33. Fulltext. Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/reso/008/06/0024-0033. Keywords.

  4. A moving boundary solution for solidification of lava lake and ...

    Indian Academy of Sciences (India)

    uniform rate from both the contact surfaces. The studies carried out using the above approaches highlighted the importance of the non- uniform cooling of an intrusion/lava lake. Worster et al (1993) suggested a reduction in the solidifi- cation time of ...

  5. The Active Lava Flows of Kilauea Volcano, Hawaii

    Indian Academy of Sciences (India)

    known as 'inflation'. Old inflated lava lobes can be recognized through their characteristic internal structure, which consists of an upper and a lower crust separated by a thicker core zone, and the arrangement of vesicles (holes left by escaping gases). Vesicles are seen arranged both as vertical cylinders, which form as.

  6. A moving boundary solution for solidification of lava lake and ...

    Indian Academy of Sciences (India)

    During the solidification of a lava lake heat is released convectively from the top surface as well as conductively into the country rock from the base, leading to non-uniform solidification. The upper solidified layer grows at a faster rate than the lower solidified layer. Similarly, solidification of magma intrusion within the crust is ...

  7. Thermophysical properties of the Lipari lavas (Southern Tyrrhenian Sea

    Directory of Open Access Journals (Sweden)

    D. Russo

    1997-06-01

    Full Text Available Results of thermophysical investigations into the lavas of the island of Lipari (Southern Tyrrhenian Sea are presented. Samples selected for laboratory measurements belong to four main magmatic cycles, which produced basaltic-andesitic, andesitic and rhyolitic lavas. The wet-bulk density and the thermal conductivity measured on 69 specimens range from 1900 to 2760 kg m-3 and from 1.02 to 2.88 W m-1 K-1, respectively. Porosity is never negligible and its influence on density is maximum in rhyolites of the third cycle. The thermal conductivity is also influenced by the amount of glass. Rhyolitic obsidians show values lower than other rhyolites, although the latter rocks have a larger average porosity. The radioactive heat production determined on 36 specimens varies with the rock type, depending on the amount of U, Th and K. In basic lavas of the first cycle its value is 0.95°± 0.30 mW m-3, while in rhyolites of the fourth cycle it attains 6.68°±0.61 mW m-3. A comparison between results of g-ray spectrometry and X-ray fluorescence points out that the assumption of equilibrium in the decay series of the isotopic elements seems fulfilled. The information obtained is useful not only for the interpretation of geophysical surveys but also for the understanding of the geochemical characteristics of lavas.

  8. The petrogenesis of high-calcium boninite lavas dredged from the northern Tonga ridge

    Energy Technology Data Exchange (ETDEWEB)

    Falloon, T.J.; Crawford, A.J. (Dept. of Geology, Univ. of Tasmania, Sandy Bay (Australia))

    1991-03-01

    In 1984 the research vessel 'Natsushima' dredged a fresh suite of MgO- and SiO{sub 2}-rich lavas from the northern termination of the northern Tonga ridge. These lavas are high-Ca boninites and are characterized by the presence of magnesian olivine (up to Fo{sub 94}), orthopyroxene, clinopyroxene, Cr-rich spinel and calcic plagioclase (>An{sub 90}) phenocrysts. Boninite lavas from one dredge site, station 21, range in MgO contents from 3-15 wt% and their major element chemistry appears to be consistent with production of this suite via crystal fractionation. However, large variations in incompatible trace element ratios plus petrographic and mineral chemical evidence demonstrate that magma mixing has been an important process. The isotopic (Sr, Nd) composition of the Tongan high-Ca boninites suggest that their mantle sources are part of a regional OIB mantle domain upwelling beneath the Fiji-Lau Tonga subduction zone system. The OIB mantle source to the Tongan boninites was of refractory lherzolite composition, depleted in 'basaltic' components by prior generation of Lau Basin back arc crust. The mantle sources of the Tongan high-Ca boninites have been enriched in incompatible elements by one or more metasomatic phases, suggested to be a hydrous fluid from the subducting lithospheric slab, a carbonatite melt and a small-degree silicate partial melt both derived from OIB mantle sources. There is no evidence for the involvement of sediment in the source of the Tonga boninites. The presence of the high-Ca boninite lavas at the northern end of the Tonga ridge can be explained by the presence of a northeast-directed spreading ridge in the northern part of the Lau Basin which is propagating into the north Tonga arc. Upwelling asthenospheric mantle beneath the spreading ridge may cause partial melting of refractory peridotite located in the mantle wedge above the subducting Pacific plate at shallow depths (<25 km). (orig.).

  9. Emplacement of a silicic lava dome through a crater glacier: Mount St Helens, 2004-06

    Science.gov (United States)

    Walder, J.S.; LaHusen, R.G.; Vallance, J.W.; Schilling, S.P.

    2007-01-01

    The process of lava-dome emplacement through a glacier was observed for the first time after Mount St Helens reawakened in September 2004. The glacier that had grown in the crater since the cataclysmic 1980 eruption was split in two by the new lava dome. The two parts of the glacier were successively squeezed against the crater wall. Photography, photogrammetry and geodetic measurements document glacier deformation of an extreme variety, with strain rates of extraordinary magnitude as compared to normal alpine glaciers. Unlike normal temperate glaciers, the crater glacier shows no evidence of either speed-up at the beginning of the ablation season or diurnal speed fluctuations during the ablation season. Thus there is evidently no slip of the glacier over its bed. The most reasonable explanation for this anomaly is that meltwater penetrating the glacier is captured by a thick layer of coarse rubble at the bed and then enters the volcano's groundwater system rather than flowing through a drainage network along the bed.

  10. Oral History (in Samoan)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Interviews with elder fishermen in American Samoa regarding changes in marine resource use and condition over time, local and traditional fishing and resource...

  11. Pyroxene thermometry of rhyolite lavas of the Bruneau-Jarbidge eruptive center, Central Snake River Plain

    Science.gov (United States)

    Cathey, Henrietta E.; Nash, Barbara P.

    2009-11-01

    The Bruneau-Jarbidge eruptive center of the central Snake River Plain in southern Idaho, USA produced multiple rhyolite lava flows with volumes of consanguinity of such reservoirs to those that supplied the polymodal Cougar Point Tuff. Pyroxene thermometry results obtained using QUILF equilibria yield pre-eruptive magma temperatures of 905 to 980 °C, and individual modes consistently record higher Ca content and higher temperatures than pyroxenes with equivalent Fe-Mg ratios in the preceding Cougar Point Tuff. As is the case with the Cougar Point Tuff, evidence for up-temperature zonation within single crystals that would be consistent with recycling of sub- or near-solidus material from antecedent magma reservoirs by rapid reheating is extremely rare. Also, the absence of intra-crystal zonation, particularly at crystal rims, is not easily reconciled with cannibalization of caldera fill that subsided into pre-eruptive reservoirs. The textural, compositional and thermometric results rather are consistent with minor re-equilibration to higher temperatures of the unerupted crystalline residue from the explosive phase of volcanism, or perhaps with newly generated magmas from source materials very similar to those for the Cougar Point Tuff. Collectively, the data suggest that most of the pyroxene compositional diversity that is represented by the tuffs and lavas was produced early in the history of the eruptive center and that compositions across this range were preserved or duplicated through much of its lifetime. Mineral compositions and thermometry of the multiple lavas suggest that unerupted magmas residual to the explosive phase of volcanism may have been stored at sustained, high temperatures subsequent to the explosive phase of volcanism. If so, such persistent high temperatures and large eruptive magma volumes likewise require an abundant and persistent supply of basalt magmas to the lower and/or mid-crust, consistent with the tectonic setting of a continental

  12. Comparison of bacterial communities from lava cave microbial mats to overlying surface soils from Lava Beds National Monument, USA.

    Science.gov (United States)

    Lavoie, Kathleen H; Winter, Ara S; Read, Kaitlyn J H; Hughes, Evan M; Spilde, Michael N; Northup, Diana E

    2017-01-01

    Subsurface habitats harbor novel diversity that has received little attention until recently. Accessible subsurface habitats include lava caves around the world that often support extensive microbial mats on ceilings and walls in a range of colors. Little is known about lava cave microbial diversity and how these subsurface mats differ from microbial communities in overlying surface soils. To investigate these differences, we analyzed bacterial 16S rDNA from 454 pyrosequencing from three colors of microbial mats (tan, white, and yellow) from seven lava caves in Lava Beds National Monument, CA, USA, and compared them with surface soil overlying each cave. The same phyla were represented in both surface soils and cave microbial mats, but the overlap in shared OTUs (operational taxonomic unit) was only 11.2%. Number of entrances per cave and temperature contributed to observed differences in diversity. In terms of species richness, diversity by mat color differed, but not significantly. Actinobacteria dominated in all cave samples, with 39% from caves and 21% from surface soils. Proteobacteria made up 30% of phyla from caves and 36% from surface soil. Other major phyla in caves were Nitrospirae (7%) followed by minor phyla (7%), compared to surface soils with Bacteroidetes (8%) and minor phyla (8%). Many of the most abundant sequences could not be identified to genus, indicating a high degree of novelty. Surface soil samples had more OTUs and greater diversity indices than cave samples. Although surface soil microbes immigrate into underlying caves, the environment selects for microbes able to live in the cave habitats, resulting in very different cave microbial communities. This study is the first comprehensive comparison of bacterial communities in lava caves with the overlying soil community.

  13. Cerberus Fossae and Elysium Planitia Lavas, Mars: Source Vents, Flow Rates, Edifice Styles and Water Interactions

    Science.gov (United States)

    Sakimoto, S. E. H.; Gregg, T. K. P.

    2004-01-01

    The Cerberus Fossae and Elysium Planitia regions have been suggested as some of the youngest martian surfaces since the Viking mission, although there was doubt whether the origins were predominantly volcanic or fluvial. The Mars Global Surveyor and Mars Odyssey Missions have shown that the region is certainly young in terms of the topographic preservation and the youthful crater counts (e.g. in the tens to a few hundred million yrs.). Numerous authors have shown that fluvial and volcanic features share common flow paths and vent systems, and that there is evidence for some interaction between the lava flows and underlying volatiles as well as the use by lavas and water of the same vent system. Given the youthful age and possible water-volcanism interaction environment, we'd like constraints on water and volcanic flux rates and interactions. Here, we model ranges of volcanic flow rates where we can well-constrain them, and consider the modest flow rate results results in context with local eruption styles, and track vent locations, edifice volumes, and flow sources and data.

  14. Numerical simulation of lava flow using a GPU SPH model

    Directory of Open Access Journals (Sweden)

    Eugenio Rustico

    2011-12-01

    Full Text Available A smoothed particle hydrodynamics (SPH method for lava-flow modeling was implemented on a graphical processing unit (GPU using the compute unified device architecture (CUDA developed by NVIDIA. This resulted in speed-ups of up to two orders of magnitude. The three-dimensional model can simulate lava flow on a real topography with free-surface, non-Newtonian fluids, and with phase change. The entire SPH code has three main components, neighbor list construction, force computation, and integration of the equation of motion, and it is computed on the GPU, fully exploiting the computational power. The simulation speed achieved is one to two orders of magnitude faster than the equivalent central processing unit (CPU code. This GPU implementation of SPH allows high resolution SPH modeling in hours and days, rather than in weeks and months, on inexpensive and readily available hardware.

  15. Pāhoehoe, `a`ā, and block lava: an illustrated history of the nomenclature

    Science.gov (United States)

    Harris, Andrew J. L.; Rowland, Scott K.; Villeneuve, Nicolas; Thordarson, Thor

    2017-01-01

    Lava flows occur worldwide, and throughout history, various cultures (and geologists) have described flows based on their surface textures. As a result, surface morphology-based nomenclature schemes have been proposed in most languages to aid in the classification and distinction of lava surface types. One of the first to be published was likely the nine-class, Italian-language description-based classification proposed by Mario Gemmellaro in 1858. By far, the most commonly used terms to describe lava surfaces today are not descriptive but, instead, are merely words, specifically the Hawaiian words `a`ā (rough brecciated basalt lava) and pāhoehoe (smooth glassy basalt lava), plus block lava (thick brecciated lavas that are typically more silicic than basalt). `A`ā and pāhoehoe were introduced into the Western geological vocabulary by American geologists working in Hawai`i during the 1800s. They and other nineteenth century geologists proposed formal lava-type classification schemes for scientific use, and most of them used the Hawaiian words. In 1933, Ruy Finch added the third lava type, block lava, to the classification scheme, with the tripartite system being formalized in 1953 by Gordon Macdonald. More recently, particularly since the 1980s and based largely on studies of lava flow interiors, a number of sub-types and transitional forms of all three major lava types have been defined. This paper reviews the early history of the development of the pāhoehoe, `a`ā, and block lava-naming system and presents a new descriptive classification so as to break out the three parental lava types into their many morphological sub-types.

  16. Wisata Bencana : Sebuah Studi Kasus Lava Tour Gunung Merapi

    Directory of Open Access Journals (Sweden)

    Zein Mufarrih Muktaf

    2017-09-01

    ABSTRACK The emergence of ecotourism trends as part of nature tourism to be an offer for tourists who want to feel the sensation of different tourist. In addition to the emergence of ecotourism, also appeared many other sort of tourism, such as dark tourism and disaster tourism. Dark tourism and disaster tourism is interesting enough to be discussion. The quention of this research is how the phenomenon of disaster tourism on Lava Tour in Mount Merapi? The purpose of this research is to know the practice of disaster tour “Lava Tour” Mount Merapi. The object of research is community-based tourism in Lava Tour area located in Disaster Prone Area (Kawasan Rawan Bencana III. Research method using case study approach. The conclusion of this research is, first, disaster tour is educational tour which destruction, death and back a life as tourist attraction. Secondly, that disaster tour presents a trip or tour because tourists can direct to see the disaster site. Third, the role of communication between the community-based tourism to the tourists are very important, such as telling the chronology of events to the tourists. It is better if the source of information teller is a direct victim or a direct eye witness, because it is more authentic and convincing. Fourth, disaster tourism prefers the interaction between witnesses and tourists. Fifth, disaster tours can be part of disaster literacy, as witnesses or victims explain a lot about disaster. Keywod : disaster tourism; tour; Mount Merapi; Tourism Communication; disaster literacy

  17. Cosmogenic He in terrestrial rocks: The summit lavas of Maui.

    Science.gov (United States)

    Craig, H; Poreda, R J

    1986-04-01

    We have identified terrestrial cosmic rayproduced (3)He in three lava flows on the crest of Haleakala Volcano on Maui, 3 km above sea level, and approximately 0.5 million years old. Although these lavas, like all oceanic basalts, contain primordial (3)He from the mantle, the "cosmogenic" component ((3)He(C)) can be identified unambiguously because it is extractable only by high-temperature vacuum fusion. In contrast, a large fraction of the mantle helium resides in fluid inclusions and can be extracted by vacuum crushing, leaving a residual component with (3)He/(4)He ratios as high as 75x those in the atmosphere, which can be liberated by melting the crushed grains. Cosmogenic (3)He is present in both olivines and clinopyroxenes at 0.8-1.2 x 10(-12) ml(STP)/g and constitutes 75% +/- 5% of the total (3)He present. The observed (3)He(C) levels require a cosmic ray exposure age of only some 64,000 years, much less than the actual age of the lavas, if there is no erosion. Using a model that includes effects of uplift or submergence as well as erosion, we calculate an apparent "erosion rate" of the order of 8.5 m/10(6) years for the western rim of the summit crater, as an example of the application of measurements of cosmogenic rare gases to terrestrial geological problems.

  18. Extended SO2 outgassing from the 2014-2015 Holuhraun lava flow field, Iceland

    Science.gov (United States)

    Simmons, Isla C.; Pfeffer, Melissa A.; Calder, Eliza S.; Galle, Bo; Arellano, Santiago; Coppola, Diego; Barsotti, Sara

    2017-11-01

    The 2014-2015 Holuhraun eruption was the largest fissure eruption in Iceland in the last 200 years. This flood basalt eruption produced 1.6 km3 of lava, forming a lava flow field covering an area of 84 km2. Over the 6-month course of the eruption, 11 Mt of SO2 were released from the eruptive vents as well as from the cooling lava flow field. This work examines the post-eruption SO2 flux emitted by the Holuhraun lava flow field, providing the first study of the extent and relative importance of the outgassing of a lava flow field after emplacement. We use data from a scanning differential optical absorption spectroscopy (DOAS) instrument installed at the eruption site to monitor the flux of SO2. In this study, we propose a new method to estimate the SO2 emissions from the lava flow field, based on the characteristic shape of the scanned column density distribution of a homogenous source close to the ground. Post-eruption outgassing of the lava flow field continued for at least 3 months after the end of the eruption, with SO2 flux between < 1 and 9 kg/s. The lava flow field post-eruption emissions were not a significant contributor to the total SO2 released during the eruption; however, the lava flow field was still an important polluter and caused high concentrations of SO2 at ground level after lava effusion ceased.

  19. Disruption of tephra fall deposits caused by lava flows during basaltic eruptions

    Science.gov (United States)

    Brown, R. J.; Thordarson, T.; Self, S.; Blake, S.

    2015-10-01

    Observations in the USA, Iceland and Tenerife, Canary Islands reveal how processes occurring during basaltic eruptions can result in complex physical and stratigraphic relationships between lava and proximal tephra fall deposits around vents. Observations illustrate how basaltic lavas can disrupt, dissect (spatially and temporally) and alter sheet-form fall deposits. Complexity arises through synchronous and alternating effusive and explosive activity that results in intercalated lavas and tephra deposits. Tephra deposits can become disrupted into mounds and ridges by lateral and vertical displacement caused by movement (including inflation) of underlying pāhoehoe lavas and clastogenic lavas. Mounds of tephra can be rafted away over distances of 100 s to 1,000 s m from proximal pyroclastic constructs on top of lava flows. Draping of irregular topography by fall deposits and subsequent partial burial of topographic depressions by later lavas can result in apparent complexity of tephra layers. These processes, deduced from field relationships, have resulted in considerable stratigraphic complexity in the studied proximal regions where fallout was synchronous or alternated with inflation of subjacent lava sheets. These mechanisms may lead to diachronous contact relationships between fall deposits and lava flows. Such complexities may remain cryptic due to textural and geochemical quasi-homogeneity within sequences of interbedded basaltic fall deposits and lavas. The net effect of these processes may be to reduce the usefulness of data collected from proximal fall deposits for reconstructing basaltic eruption dynamics.

  20. Asymmetric deformation structure of lava spine in Unzen Volcano, Japan

    Science.gov (United States)

    Miwa, T.; Okumura, S.; Matsushima, T.; Shimizu, H.

    2013-12-01

    Lava spine is commonly generated by effusive eruption of crystal-rich, dacitic-andesitic magmas. Especially, deformation rock on surface of lava spine has been related with processes of magma ascent, outgassing, and generation of volcanic earthquake (e.g., Cashman et al. 2008). To reveal the relationships and generation process of the spine, it is needed to understand a spatial distribution of the deformation rock. Here we show the spatial distribution of the deformation rock of lava spine in the Unzen volcano, Japan, to discuss the generation process of the spine. The lava spine in Unzen volcano is elongated in the E-W direction, showing a crest like shape with 150 long, 40 m wide and 50 m high. The lava spine is divided into following four parts: 1) Massive dacite part: Dense dacite with 30 m of maximum thickness, showing slickenside on the southern face; 2) Sheared dacite part: Flow band developed dacite with 1.0 m of maximum thickness; 3) Tuffisite part: Network of red colored vein develops in dacite with 0.5 m of maximum thickness; 4) Breccia part: Dacitic breccia with 10 m of maximum thickness. The Breccia part dominates in the northern part of the spine, and flops over Massive dacite part accross the Sheared dacite and Tuffisite parts. The slickenside on southern face of massive dacite demonstrates contact of solids. The slickenside breaks both of phenocryst and groundmass, demonstrating that the slickenside is formed after significant crystallization at the shallow conduit or on the ground surface. The lineation of the slickenside shows E-W direction with almost horizontal rake angle, which is consistent with the movement of the spine to an east before emplacement. Development of sub-vertical striation due to extrusion was observed on northern face of the spine (Hayashi, 1994). Therefore, we suggest that the spine just at extrusion consisted of Massive dacite, Sheared dacite, Tuffisite, Breccia, and Striation parts in the northern half of the spine. Such a

  1. Controls on lava-snow interactions from propogation styles during the 2012-13 Tolbachik eruption

    Science.gov (United States)

    Edwards, Benjamin; Belousov, Alexander; Belousov, Marina

    2014-05-01

    Knowledge of how volcanism interacts with hydrosphere/cryosphere is critical for understanding the functioning and evolution of the Earth, establishing volcanism-climate linkages, and estimations of related hazards. Until now, no special studies have been focused on interactions between snowpack and advancing incandescent lava during volcanic eruptions, even though snow is the most widely distributed form of solid H2O on the planet. It was thought a priori that snow might melt rapidly in front of active lava flows producing vigorous floods. Here we present results of unique field observations made in the snowpack in front of advancing basaltic lava flows during the 2012-13 eruption at Tolbachik volcano, Kamchatka, Russia. Our observations in the first time demonstrate that in reality heat transfer through lava/snow boundary occurs relatively slowly, so that melting of the majority of the snow pack occurs over the span of several hours-days after emplacement of the lava flows, producing only local and sporadic meltwater floods. Two fundamentally different styles of lava propagation result in two strikingly different responses of snowpack: i) 'a'a lava advancing in a rolling caterpillar-track motion propagates on top of snowpack; the melt water accumulates in (saturates) the layer of snow buried underneath the lava flow and does not interact notably with the lava material, and ii) pahoehoe lava advancing as inflating lobes propagates beneath/inside snowpack, locally generating slowly growing 'snow-domes'; the melt water precipitates down into incandescent lava producing chilling and local thermal shock/quench fragmentation (minor hyaloclastite production). Our observations show that lava-snow interactions can vary significantly depending on styles of flow front advance. Lava flows emplaced over areas covered with snow bear features that can be distinguished in old stratigraphic sequences and used for paleoclimatic reconstructions on Earth, Mars and other planets.

  2. Using Lava Tube Skylight Thermal Emission Spectra to Determine Lava Composition on Io: Quantitative Constraints for Observations by Future Missions to the Jovian System.

    Science.gov (United States)

    Davies, A. G.

    2008-12-01

    Deriving the composition of Io's dominant lavas (mafic or ultramafic?) is a major objective of the next missions to the jovian system. The best opportunities for making this determination are from observations of thermal emission from skylights, holes in the roof of a lava tube through which incandescent lava radiates, and Io thermal outbursts, where lava fountaining is taking place [1]. Allowing for lava cooling across the skylight, the expected thermal emission spectra from skylights of different sizes have been calculated for laminar and turbulent tube flow and for mafic and ultramafic composition lavas. The difference between the resulting mafic and ultramafic lava spectra has been quantified, as has the instrument sensitivity needed to acquire the necessary data to determine lava eruption temperature, both from Europa orbit and during an Io flyby. A skylight is an excellent target to observe lava that has cooled very little since eruption (temperatures close to lava eruption temperature. Skylights are therefore easily discernible against a cool background, and are detectable from great distances at night or with Io in eclipse with imagers covering the range 0.4 to 5.0 μm. To distinguish between ultramafic and mafic lavas, multispectral (or hyperspectral) observations with precise exposure timing and knowledge of filter response are needed in the range 0.4 to 0.8 μm, with (minimally) an additional model-constraining measurement at ~4-5 μm. As with many lava tube systems on Earth, skylights should be common on Io (for example, at Prometheus, Culann and Amirani). The possible superheating of lava prior to eruption complicates the analysis [4], but is likely to be significant only for deep- seated, often explosive, eruptions. Effusive activity at the aforementioned three locations is likely fed from shallow reservoirs [5], minimising superheating effects. This work was carried out at the Jet Propulsion Laboratory-California Institute of Technology, under

  3. A meta-analysis of aneurysm formation in laser assisted vascular anastomosis (LAVA)

    Science.gov (United States)

    Chen, Chen; Peng, Fei; Xu, Dahai; Cheng, Qinghua

    2009-08-01

    Laser assisted vascular anastomosis (LAVA) is looked as a particularly promising non-suture method in future. However, aneurysm formation is one of the main reasons delay the clinical application of LAVA. Some scientists investigated the incidence of aneurysms in animal model. To systematically analyze the literature on reported incidence of aneurysm formation in LAVA therapy, we performed a meta-analysis comparing LAVA with conventional suture anastomosis (CSA) in animal model. Data were systematically retrieved and selected from PUBMED. In total, 23 studies were retrieved. 18 studies were excluded, and 5 studies involving 647 animals were included. Analysis suggested no statistically significant difference between LAVA and CSA (OR 1.24, 95%CI 0.66-2.32, P=0.51). Result of meta analysis shows that the technology of LAVA is very close to clinical application.

  4. Gusev Rocks Solidified from Lava (Approximate True Color)

    Science.gov (United States)

    2006-01-01

    In recent weeks, as NASA's Mars Exploration Rover Spirit has driven through the basin south of 'Husband Hill,' it has been traversing mainly sand and dune deposits. This week, though, Spirit has been maneuvering along the edge of an arc-shaped feature called 'Lorre Ridge' and has encountered some spectacular examples of basaltic rocks with striking textures. This panoramic camera (Pancam) image shows a group of boulders informally named 'FuYi.' These basaltic rocks were formed by volcanic processes and may be a primary constituent of Lorre Ridge and other interesting landforms in the basin. Spirit first encountered basalts at its landing site two years ago, on a vast plain covered with solidified lava that appeared to have flowed across Gusev Crater. Later, basaltic rocks became rare as Spirit climbed Husband Hill. The basaltic rocks that Spirit is now seeing are interesting because they exhibit many small holes or vesicles, similar to some kinds of volcanic rocks on Earth. Vesicular rocks form when gas bubbles are trapped in lava flows and the rock solidifies around the bubbles. When the gas escapes, it leaves holes in the rock. The quantity of gas bubbles in rocks on Husband Hill varies considerably; some rocks have none and some, such as several here at FuYi, are downright frothy. The change in textures and the location of the basalts may be signs that Spirit is driving along the edge of a lava flow. This lava may be the same as the basalt blanketing the plains of Spirit's landing site, or it may be different. The large size and frothy nature of the boulders around Lorre Ridge might indicate that eruptions once took place at the edge of the lava flow, where the lava interacted with the rocks of the basin floor. Scientists hope to learn more as Spirit continues to investigate these rocks. As Earth approaches the Chinese New Year (The Year of the Dog), the Athena science team decided to use nicknames representing Chinese culture and geography to identify rocks and

  5. Holuhraun 2014-2015 Eruption Site on Iceland: A Flood Lava Analogue for Mars

    Science.gov (United States)

    Voigt, J.; Hamilton, C. W.; Scheidt, S. P.; Bonnefoy, L. E.; Jónsdóttir, I.; Höskuldsson, A.; Thordarson, T.

    2017-09-01

    The Holuhraun eruption 2014-2015 is the largest flood lava flow in Iceland since the Laki eruption in 1783-1784. We here present the first facies map of the whole Holuhraun lava flow, which we linked to the chronological emplacement history. Furthermore the facies we identify at Holuhraun are common on the Martian surface, especially at Marte Vallis and Rahway Valles. It therefore provides unique insights into the emplacement of flood lavas on Earth and other planetary bodies.

  6. 120 years of Italian and Vesuvius history in the lava medals collection of the Osservatorio Vesuviano

    OpenAIRE

    De Lucia, M.; Russo, M.

    2011-01-01

    Lava medals constitute a unique example that links Vesuvian eruptions to history, politics and science. Medals coined in the Vesuvius lava date back to the period in which the state of the volcano was characterized by an open conduit, so that warm lava was still used. This state of activity lasted from 1631 to 1944, a period of time during which effusive or effusive-explosive eruptions frequently occurred, followed by very short periods of rest. The medals were realized thro...

  7. Estimating eruption temperature from thermal emission spectra of lava fountain activity in the Erta'Ale (Ethiopia) volcano lava lake: Implications for observing Io's volcanoes

    Science.gov (United States)

    Davies, Ashley G.; Keszthelyi, Laszlo P.; McEwen, Alfred S.

    2011-01-01

    We have analysed high-spatial-resolution and high-temporal-resolution temperature measurements of the active lava lake at Erta'Ale volcano, Ethiopia, to derive requirements for measuring eruption temperatures at Io's volcanoes. Lava lakes are particularly attractive targets because they are persistent in activity and large, often with ongoing lava fountain activity that exposes lava at near-eruption temperature. Using infrared thermography, we find that extracting useful temperature estimates from remote-sensing data requires (a) high spatial resolution to isolate lava fountains from adjacent cooler lava and (b) rapid acquisition of multi-color data. Because existing spacecraft data of Io's volcanoes do not meet these criteria, it is particularly important to design future instruments so that they will be able to collect such data. Near-simultaneous data at more than two relatively short wavelengths (shorter than 1 μm) are needed to constrain eruption temperatures. Resolving parts of the lava lake or fountains that are near the eruption temperature is also essential, and we provide a rough estimate of the required image scale.

  8. LAVA Simulations for the AIAA Sonic Boom Prediction Workshop

    Science.gov (United States)

    Housman, Jeffrey A.; Sozer, Emre; Moini-Yekta , Shayan; Kiris, Cetin C.

    2014-01-01

    Computational simulations using the Launch Ascent and Vehicle Aerodynamics (LAVA) framework are presented for the First AIAA Sonic Boom Prediction Workshop test cases. The framework is utilized with both structured overset and unstructured meshing approaches. The three workshop test cases include an axisymmetric body, a Delta Wing-Body model, and a complete low-boom supersonic transport concept. Solution sensitivity to mesh type and sizing, and several numerical convective flux discretization choices are presented and discussed. Favorable comparison between the computational simulations and experimental data of nearand mid-field pressure signatures were obtained.

  9. NVP melt/magma viscosity: insight on Mercury lava flows

    Science.gov (United States)

    Rossi, Stefano; Morgavi, Daniele; Namur, Olivier; Vetere, Francesco; Perugini, Diego; Mancinelli, Paolo; Pauselli, Cristina

    2016-04-01

    After more than four years of orbiting Mercury, NASA's MESSENGER spacecraft came to an end in late April 2015. MESSENGER has provided many new and surprising results. This session will again highlight the latest results on Mercury based on MESSENGER observations or updated modelling. The session will further address instrument calibration and science performance both retrospective on MESSENGER and on the ESA/JAXA BepiColombo mission. Papers covering additional themes related to Mercury are also welcomed. Please be aware that this session will be held as a PICO session. This will allow an intensive exchange of expertise and experience between the individual instruments and mission. NVP melt/magma viscosity: insight on Mercury lava flows S. Rossi1, D. Morgavi1, O. Namur2, D. Perugini1, F.Vetere1, P. Mancinelli1 and C. Pauselli1 1 Dipartimento di Fisica e Geologia, Università di Perugia, piazza Università 1, 06123 Perugia, Italy 2 Uni Hannover Institut für Mineralogie, Leibniz Universität Hannover, Callinstraβe 3, 30167 Hannover, Germany In this contribution we report new measurements of viscosity of synthetic komatitic melts, used the behaviour of silicate melts erupted at the surface of Mercury. Composition of Mercurian surface magmas was calculated using the most recent maps produced from MESSENGER XRS data (Weider et al., 2015). We focused on the northern hemisphere (Northern Volcanic Province, NVP, the largest lava flow on Mercury and possibly in the Solar System) for which the spatial resolution of MESSENGER measurements is high and individual maps of Mg/Si, Ca/Si, Al/Si and S/Si were combined. The experimental starting material contains high Na2O content (≈7 wt.%) that strongly influences viscosity. High temperature viscosity measurements were carried out at 1 atm using a concentric cylinder apparatus equipped with an Anton Paar RheolabQC viscometer head at the Department of Physics and Geology (PVRG_lab) at the University of Perugia (Perugia, Italy

  10. Basalt models for the Mars penetrator mission: Geology of the Amboy Lava Field, California

    Science.gov (United States)

    Greeley, R.; Bunch, T. E.

    1976-01-01

    Amboy lava field (San Bernardino County, California) is a Holocene basalt flow selected as a test site for potential Mars Penetrators. A discussion is presented of (1) the general relations of basalt flow features and textures to styles of eruptions on earth, (2) the types of basalt flows likely to be encountered on Mars and the rationale for selection of the Amboy lava field as a test site, (3) the general geology of the Amboy lava field, and (4) detailed descriptions of the target sites at Amboy lava field.

  11. Role of heat advection in a channeled lava flow with power law, temperature-dependent rheology

    Science.gov (United States)

    Filippucci, Marilena; Tallarico, Andrea; Dragoni, Michele

    2013-06-01

    The cooling of a lava flow, both in the transient and the steady state, is investigated considering that lava rheology is pseudoplastic and dependent on temperature. Lava exits from the vent with constant velocity and flows down a slope under the effect of gravity force inside a channel of rectangular cross section. We consider that cooling of lava is caused by thermal radiation into the atmosphere and thermal conduction at the channel walls and at the ground. The heat equation is solved numerically in a 3-D computational domain, and the solution is tested to evaluate the numerical errors. We study the steady state and the initial transient period of lava cooling. Results indicate that the advective heat transport significantly modifies the cooling rate of lava, slowing down the cooling process. Since the lava velocity depends on temperature, the cooling rate depends on the effusion temperature. Velocity profiles are modified during cooling showing two marginal static zones where the crust can form and remain stable. The fraction of crust coverage is calculated under the assumption that the solid lava is a plastic body with temperature-dependent yield strength. We numerically confirm that heat advection cannot be neglected in the mechanism of formation of lava tubes.

  12. The Catania 1669 lava eruptive crisis: simulation of a new possible eruption

    OpenAIRE

    Crisci, G. M.; Di Gregorio, S.; RONGO R.; Scarpelli, M.; Spataro, W.; Calvari, S.

    2001-01-01

    SCIARA (Smart Cellular Interactive Automata for modeling the Rheology of Aetnean lava flows, to be read as “shea’rah”), our first two-dimensional Cellular Automata model for the simulation of lava flows, was tested and validated with success on several lava events like the 1986/87 Etnean eruption and the last phase of the 1991/93 Etnean one. Real and simulated events are satisfying within limits to forecast the surface covered by the lava flow. Moreover, improved versions have ...

  13. Observations of actively forming lava tubes and associated structures, Hawaii, part 2

    Science.gov (United States)

    Greeley, R.

    1971-01-01

    A ground examination is made of lave tubes and channels. The surface morphology and the changes noted through lava flow activity are cited, and compared to earlier aerial observations. The lava activity was believed to be caused by a small lava lake exposed by the collapse of a crust covering it. Drainage of the lake was caused by a fissure erruption. New tubes or extensions of existing ones were noted from the flow. Molten lava was not seen in any tubes examined on the ground, but some of the flows were not sufficiently cooled to allow subsurface examination and survey of the tubes.

  14. Lineage specific evolution of the VNTR composite retrotransposon central domain and its role in retrotransposition of gibbon LAVA elements.

    Science.gov (United States)

    Lupan, Iulia; Bulzu, Paul; Popescu, Octavian; Damert, Annette

    2015-05-16

    VNTR (Variable Number of Tandem Repeats) composite retrotransposons - SVA (SINE-R-VNTR-Alu), LAVA (LINE-1-Alu-VNTR-Alu), PVA (PTGR2-VNTR-Alu) and FVA (FRAM-VNTR-Alu) - are specific to hominoid primates. Their assembly, the evolution of their 5' and 3' domains, and the functional significance of the shared 5' Alu-like region are well understood. The central VNTR domain, by contrast, has long been assumed to represent a more or less random collection of 30-50 bp GC-rich repeats. It is only recently that it attracted attention in the context of regulation of SVA expression. Here we provide evidence that the organization of the VNTR is non-random, with conserved repeat unit (RU) arrays at both the 5' and 3' ends of the VNTRs of human, chimpanzee and orangutan SVA and gibbon LAVA. The younger SVA subfamilies harbour highly organized internal RU arrays. The composition of these arrays is specific to the human/chimpanzee and orangutan lineages, respectively. Tracing the development of the VNTR through evolution we show for the first time how tandem repeats evolve within the constraints set by a functional, non-autonomous non-LTR retrotransposon in two different families - LAVA and SVA - in different hominoid lineages. Our analysis revealed that a microhomology-driven mechanism mediates expansion/contraction of the VNTR domain at the DNA level. Elements of all four VNTR composite families have been shown to be mobilized by the autonomous LINE1 retrotransposon in trans. In case of SVA, key determinants of mobilization are found in the 5' hexameric repeat/Alu-like region. We now demonstrate that in LAVA, by contrast, the VNTR domain determines mobilization efficiency in the context of domain swaps between active and inactive elements. The central domain of VNTR composites evolves in a lineage-specific manner which gives rise to distinct structures in gibbon LAVA, orangutan SVA, and human/chimpanzee SVA. The differences observed between the families and lineages are likely to

  15. Remagnetization of lava flows spanning the last geomagnetic reversal

    Science.gov (United States)

    Vella, Jérôme; Carlut, Julie; Valet, Jean-Pierre; Goff, Maxime Le; Soler, Vicente; Lopes, Fernando

    2017-08-01

    Large directional changes of remanent magnetization within lava flows that cooled during geomagnetic reversals have been reported in several studies. A geomagnetic scenario implies extremely rapid geomagnetic changes of several degrees per day, thus difficult to reconcile with the rate of the earth's core liquid motions. So far, no complete rock magnetic model provides a clear explanation. We revisited lava flows sandwiched between an underlying reverse and an overlying normal polarity flow marking the last reversal in three distinct volcanic sequences of the La Palma Island (Canary archipelago, Spain) that are characterized by a gradual evolution of the direction of their remanent magnetization from bottom to top. Cleaning efficiency of thermal demagnetization was not improved by very rapid heating and cooling rates as well as by continuous demagnetization using a Triaxe magnetometer. We did not observe partial self-reversals and minor changes in magnetic grain sizes are not related to the within-flow directional changes. Microscopic observations indicate poor exsolution, which suggests post-cooling thermochemical remagnetization processes. This scenario is strongly reinforced by laboratory experiments that show large resistance to thermal demagnetization when thermoremanence was acquired over a long time period. We speculate that in the present situation exsolution was reactivated during in field reheating and yielded formation of new magnetite, yet magnetic domain state rearrangements could also play a role. Initial reheating when the overlying flow took place, albeit moderate (less than 200-300 °C), was enough to produce overlying components with significantly higher unblocking temperatures.

  16. Mapping gullies, dunes, lava fields, and landslides via surface roughness

    Science.gov (United States)

    Korzeniowska, Karolina; Pfeifer, Norbert; Landtwing, Stephan

    2018-01-01

    Gully erosion is a widespread and significant process involved in soil and land degradation. Mapping gullies helps to quantify past, and anticipate future, soil losses. Digital terrain models offer promising data for automatically detecting and mapping gullies especially in vegetated areas, although methods vary widely measures of local terrain roughness are the most varied and debated among these methods. Rarely do studies test the performance of roughness metrics for mapping gullies, limiting their applicability to small training areas. To this end, we systematically explored how local terrain roughness derived from high-resolution Light Detection And Ranging (LiDAR) data can aid in the unsupervised detection of gullies over a large area. We also tested expanding this method for other landforms diagnostic of similarly abrupt land-surface changes, including lava fields, dunes, and landslides, as well as investigating the influence of different roughness thresholds, resolutions of kernels, and input data resolution, and comparing our method with previously published roughness algorithms. Our results show that total curvature is a suitable metric for recognising analysed gullies and lava fields from LiDAR data, with comparable success to that of more sophisticated roughness metrics. Tested dunes or landslides remain difficult to distinguish from the surrounding landscape, partly because they are not easily defined in terms of their topographic signature.

  17. Crystallization of tholeiitic basalt in Alae Lava Lake, Hawaii

    Science.gov (United States)

    Peck, D.L.; Wright, T.L.; Moore, J.G.

    1966-01-01

    The eruption of Kilauea Volcano August 21-23, 1963, left 600,000 cubic meters of basaltic lava in a lava lake as much as 15 meters deep in Alae pit crater. Field studies of the lake began August 27 and include repeated core drilling, measurements of temperature in the crust and melt, and precise level surveys of the lake surface. The last interstitial melt in the lake solidified late in September 1964; by mid August 1965 the maximum temperature was 690??C at a depth of 11.5 meters. Pumice air-quenched from about 1140??C contains only 5 percent crystals - clinopyroxene, cuhedral olivine (Fo 80), and a trace of plagioclase, (An 70). Drill cores taken from the zone of crystallization in the lake show that olivine continued crystallizing to about 1070??C; below that it reacts with the melt, becoming corroded and mantled by pyroxene and plagioclase. Below 1070??C, pyroxene and plagioclase crystallized at a constant ratio. Ilmenite first appeared at about 1070??C and was joined by magnetite at about 1050??C; both increased rapidly in abundance to 1000??C. Apatite first appeared as minute needles in interstitial glass at 1000??C. Both the abundance and index of refraction of glass quenched from melt decreased nearly linearly with falling temperature. At 1070??C the quenched lava contains about 65 percent dark-brown glass with an index of 1.61; at 980??C it contains about 8 percent colorless glass with an index of 1.49. Below 980??C, the percentage of glass remained constant. Progressive crystallization forced exsolution of gases from the melt fraction; these formed vesicles and angular pores, causing expansion of the crystallizing lava and lifting the surface of the central part of the lake an average of 19.5 cm. The solidified basalt underwent pneumatolitic alteration, including deposition of cristobalite at 800??C, reddish alteration of olivine at 700??C, tarnishing of ilmenite at 550??C, deposition of anhydrite at 250??C, and deposition of native sulfur at 100??C

  18. DOWNFLOW code and LIDAR technology for lava flow analysis and hazard assessment at Mount Etna

    Directory of Open Access Journals (Sweden)

    Alessandro Fornaciai

    2011-12-01

    Full Text Available The use of a lava-flow simulation (DOWNFLOW probabilistic code and airborne light detection and ranging (LIDAR technology are combined to analyze the emplacement of compound lava flow fields at Mount Etna (Sicily, Italy. The goal was to assess the hazard posed by lava flows. The LIDAR-derived time series acquired during the 2006 Mount Etna eruption records the changing topography of an active lava-flow field. These short-time-interval, high-resolution topographic surveys provide a detailed quantitative picture of the topographic changes. The results highlight how the flow field evolves as a number of narrow (5-15 m wide disjointed flow units that are fed simultaneously by uneven lava pulses that advance within formed channels. These flow units have widely ranging advance velocities (3-90 m/h. Overflows, bifurcations and braiding are also clearly displayed. In such a complex scenario, the suitability of deterministic codes for lava-flow simulation can be hampered by the fundamental difficulty of measuring the flow parameters (e.g. the lava discharge rate, or the lava viscosity of a single flow unit. However, the DOWNFLOW probabilistic code approaches this point statistically and needs no direct knowledge of flow parameters. DOWNFLOW intrinsically accounts for complexities and perturbations of lava flows by randomly varying the pre-eruption topography. This DOWNFLOW code is systematically applied here over Mount Etna, to derive a lava-flow hazard map based on: (i the topography of the volcano; (ii the probability density function for vent opening; and (iii a law for the expected lava-flow length for all of the computational vents considered. Changes in the hazard due to the recent morphological evolution of Mount Etna have also been addressed.

  19. Phantom Archean crust in Mangaia hotspot lavas and the meaning of heterogeneous mantle

    Science.gov (United States)

    Herzberg, C.; Cabral, R. A.; Jackson, M. G.; Vidito, C.; Day, J. M. D.; Hauri, E. H.

    2014-06-01

    Lavas from Mangaia in the Cook-Austral island chain, Polynesia, define an HIMU (or high μ, where μ=U238/Pb204) global isotopic end-member among ocean island basalts (OIB) with the highest 206,207,208Pb/204Pb. This geochemical signature is interpreted to reflect a recycled oceanic crust component in the mantle source. Mass independently fractionated (MIF) sulfur isotopes indicate that Mangaia lavas sampled recycled Archean material that was once at the Earth's surface, likely hydrothermally-modified oceanic crust. Recent models have proposed that crust that is subducted and then returned to the surface in a mantle plume is expected to transform to pyroxenite/eclogite during transit through the mantle. Here we examine this hypothesis for Mangaia using high-precision electron microprobe analysis on olivine phenocrysts. Contrary to expectations of a crustal component and, hence pyroxenite, results show a mixed peridotite and pyroxenite source, with peridotite dominating. If the isotopic compositions were inherited from subduction of recycled oceanic crust, our work shows that this source has phantom-like properties in that it can have its lithological identity destroyed while its isotope ratios are preserved. This may occur by partial melting of the pyroxenite and injection of its silicic melts into the surrounding mantle peridotite, yielding a refertilized peridotite. Evidence from one sample reveals that not all pyroxenite in the melting region was destroyed. Identification of source lithology using olivine phenocryst chemistry can be further compromised by magma chamber fractional crystallization, recharge, and mixing. We conclude that the commonly used terms mantle “heterogeneities” and “streaks” are ambiguous, and distinction should be made of its lithological and isotopic properties.

  20. Silica-poor, mafic alkaline lavas from ocean islands and continents ...

    Indian Academy of Sciences (India)

    Comparison of the bulk-rock major-element chemistry of silica-poor, mafic alkaline lavas with experimentally determined high-pressure melts indicates that melting of anhydrous mantle lherzolite or garnet pyroxenite is not able to explain many of the major element systematics of the lavas. However, high-pressure partial ...

  1. Utilization of lava stones as water treatment media for the culture of ...

    African Journals Online (AJOL)

    The performance of lava stones as water treatment media in the culture of African catfish (Clarias gariepinus) was investigated. Catfish fingerlings of mean weight 4.7g were stocked in replicates at 32 kg/m3 and reared for 35 days in a recirculating aquaculture system (RAS) facilities with lava stones as biofilter media.

  2. Mineral chemistry of lava flows from Linga area of the Eastern ...

    Indian Academy of Sciences (India)

    Several basaltic lava flows have been identified in the study area in and around Linga, in the Eastern Deccan Volcanic Province (EDVP) on the basis of distinctly developed structural zones defined by primary volcanic structures such as columnar joints and vesicles. These basaltic lava flows are spatially distributed in four ...

  3. 76 FR 4721 - Minor Boundary Revision of Lava Beds National Monument

    Science.gov (United States)

    2011-01-26

    ... National Park Service Minor Boundary Revision of Lava Beds National Monument AGENCY: National Park Service....S.C. 460l- 9(c)(1), the boundary of the Petroglyph Point unit of Lava Beds National Monument in... to the protection of the ] significant historic and natural resources of the national monument. Dated...

  4. Distribution and size of lava shields on the Al Haruj al Aswad and the Al Haruj al Abyad Volcanic Systems, Central Libya

    Science.gov (United States)

    Elshaafi, Abdelsalam; Gudmundsson, Agust

    2017-05-01

    The Al Haruj Volcanic Province (AHVP) consists of two distinct volcanic systems. In the north is the system of Al Haruj al Aswad, covering an area of 34,200 km2, while in the south the system of Al Haruj al Abyad, covering an area of 7,850 km2. The systems have produced some 432 monogenetic volcanoes, primarily scoria (cinder) cones, lava shields, and maars. The density distribution of the volcanoes in each system, plotted as eruption points or sites, has a roughly elliptical surface expression, suggesting similar plan-view geometry of the magma sources, here suggested as deep-seated reservoirs. More specifically, the Al Haruj al Aswad magma reservoir has major and minor axes of 210 km and 119 km, respectively, and an area of 19,176 km2, the corresponding figures for the Haruj al Abyad reservoir being 108 km and 74 km, for the axes, and 6209 km2 for the area. We measured 55 lava shields on the AHVP. They are mostly restricted to the northern and southern parts of AHVP and date from late Miocene to (at least) the end of Pleistocene, while some may have been active into Holocene. In fact, although primarily monogenetic, some of the lava shields show evidence of (possibly Holocene) fissure eruptions in the summit parts. The early lava shields tend to be located at the edges of volcanic systems and with greater volumes than later (more central) shields. The average lava shield basal diameter is 4.5 km and height 63 m. There is strong linear correlation between lava shield volume and basal area, the coefficient of determination (R2) being about 0.75. When 22 Holocene Icelandic lava shields are added to the dataset, for comparison, the correlation between volume and basal area becomes R2 = 0.95. Numerical models suggest that the local stress fields favoured rupture and dyke injection at the margins of the source reservoirs during late Miocene - early Pliocene, in agreement with the distribution of the early, large-volume shields.

  5. Paleomagnetism of Holocene lava flows from the Reykjanes Peninsula and the Tungnaá lava sequence (Iceland): implications for flow correlation and ages

    Science.gov (United States)

    Pinton, Annamaria; Giordano, Guido; Speranza, Fabio; Þórðarson, Þorvaldur

    2018-01-01

    The impact of Holocene eruptive events from hot spots like Iceland may have had significant global implications; thus, dating and knowledge of past eruptions chronology is important. However, at high-latitude volcanic islands, the paucity of soils severely limits 14C dating, while the poor K content of basalts strongly restricts the use of K/Ar and Ar/Ar methods. Even tephrochronology, based on 14C age determinations, refers to layers that rarely lie directly above lava flows to be dated. We report on the paleomagnetic dating of 25 sites from the Reykjanes Peninsula and the Tungnaá lava sequence of Iceland. The gathered paleomagnetic directions were compared with the available reference paleosecular variation curves of the Earth magnetic field to obtain the possible emplacement age intervals. To test the method's validity, we sampled the precisely dated Laki (1783-1784 AD) and Eldgjà (934-938 AD) lavas. The age windows obtained for these events encompass the true flow ages. For sites from the Reykjanes peninsula and the Tugnaá lava sequence, we derived multiple possible eruption events and ages. In the Reykjanes peninsula, we propose an older emplacement age (immediately following the 870 AD Iceland Settlement age) for Ogmundarhraun and Kapelluhraun lava fields. For pre-historical (older than the settlement age) Tugnaá eruptions, the method has a dating precision of 300-400 years which allows an increase of the detail in the chronostratigraphy and distribution of lavas in the Tugnaá sequence.

  6. LiDAR-derived surface roughness signatures of basaltic lava types at the Muliwai a Pele Lava Channel, Mauna Ulu, Hawai`i

    Science.gov (United States)

    Whelley, Patrick L.; Garry, W. Brent; Hamilton, Christopher W.; Bleacher, Jacob E.

    2017-11-01

    We used light detection and ranging (LiDAR) data to calculate roughness patterns (homogeneity, mean-roughness, and entropy) for five lava types at two different resolutions (1.5 and 0.1 m/pixel). We found that end-member types (´áā and pāhoehoe) are separable (with 95% confidence) at both scales, indicating that roughness patterns are well suited for analyzing types of lava. Intermediate lavas were also explored, and we found that slabby-pāhoehoe is separable from the other end-members using 1.5 m/pixel data, but not in the 0.1 m/pixel analysis. This suggests that the conversion from pāhoehoe to slabby-pāhoehoe is a meter-scale process, and the finer roughness characteristics of pāhoehoe, such as ropes and toes, are not significantly affected. Furthermore, we introduce the ratio ENT/HOM (derived from lava roughness) as a proxy for assessing local lava flow rate from topographic data. High entropy and low homogeneity regions correlate with high flow rate while low entropy and high homogeneity regions correlate with low flow rate. We suggest that this relationship is not directional, rather it is apparent through roughness differences of the associated lava type emplaced at the high and low rates, respectively.

  7. The genesis of a lava cave in the Deccan Volcanic Province (Maharashtra, India

    Directory of Open Access Journals (Sweden)

    Nikhil R. Pawar

    2016-01-01

    Full Text Available Lava tubes and channels forming lava distributaries have been recognized from different parts of western Deccan Volcanic Province (DVP. Openings of smaller dimension have been documented from the pāhoehoe flows around Pune, in the western DVP. A small lava cave is exposed in Ghoradeshwar hill, near Pune. Detailed field studies of the physical characteristics, structure and morphology of the flows hosting the lava tube has been carried out. This is the first detailed documentation of a lava cave from the DVP. The lava cave occurs in a compound pāhoehoe flow of Karla Formation, characterized by the presence of lobes, toes and small scale features like squeeze-ups. Field observations and measurements reveal that the dimensions of the cave are small, with low roof and a maximum width of 108 cm. The cave morphology along the 20 m passage varies from circular to semi-circular, with a twilight zone to the north. The gentle micro-topography at Ghoradeshwar controlled the advancement of pāhoehoe lobes and toes within the sheet lobe. The pre-flow gradients towards the north led to the progression of flow from the east, where the cave opening is presently seen. Dimensions and related morphology of the lava cave suggest that it can be best described as a small sub-crustal cave formed by draining of an inflated of pāhoehoe lava lobe. At Ghoradeshwar, besides the natural lava cave, Buddhist caves carved in pāhoehoe lava flows are also observed, indicating that early man took advantage of the existing openings in pāhoehoe flows and sculpted the caves to suit their requirements.

  8. Radar scatterometry of sand dunes and lava flows

    Science.gov (United States)

    Blom, R.; Elachi, C.; Sheehan, A.

    1982-01-01

    Four frequency like polarized scatterometer data over a sand dune field and a volcanic field were analyzed to understand the scattering characteristics of these two terrain types as a function of frequency and incidence angle. For the frequency range studied (400 MHz to 13.3 GHz) unvegetated sand dunes are specular reflectors that return an echo to the radar antenna particularly when the geometry is such that the dune slope is nearly perpendicular to the antenna. Vegetation on the dunes can cause significant backscatter. Lava flows are strong diffuse scatterers which have backscatter values similar to coniferous forest at certain frequencies. Different observation frequencies are required for different situations. The scatterometer data correlate well with radar images.

  9. Verification and Validation Studies for the LAVA CFD Solver

    Science.gov (United States)

    Moini-Yekta, Shayan; Barad, Michael F; Sozer, Emre; Brehm, Christoph; Housman, Jeffrey A.; Kiris, Cetin C.

    2013-01-01

    The verification and validation of the Launch Ascent and Vehicle Aerodynamics (LAVA) computational fluid dynamics (CFD) solver is presented. A modern strategy for verification and validation is described incorporating verification tests, validation benchmarks, continuous integration and version control methods for automated testing in a collaborative development environment. The purpose of the approach is to integrate the verification and validation process into the development of the solver and improve productivity. This paper uses the Method of Manufactured Solutions (MMS) for the verification of 2D Euler equations, 3D Navier-Stokes equations as well as turbulence models. A method for systematic refinement of unstructured grids is also presented. Verification using inviscid vortex propagation and flow over a flat plate is highlighted. Simulation results using laminar and turbulent flow past a NACA 0012 airfoil and ONERA M6 wing are validated against experimental and numerical data.

  10. Cave dwelling Onychophora from a Lava Tube in the Galapagos

    Directory of Open Access Journals (Sweden)

    Luis Espinasa

    2015-01-01

    Full Text Available A new population of velvet worms (Onychophora inhabiting a lava tube cave in the island of Santa Cruz, Galapagos, is reported here. The population size is large, suggesting that they may be troglophilic. Its members are darkly pigmented, with no obvious troglomorphic features. Their 16S rRNA sequence showed no differences when compared to an unidentified species of surface velvet worm from the same island, thus supporting cave and surface populations belong to the same species. Based on the 16S rRNA data, the Galapagos velvet worms derived from an Ecuadorian/Colombian clade, as would be expected of ease of dispersal from the nearest mainland to the Galapagos Islands.

  11. Radiogenic isotopes of arc lavas constrain uplift of the Andes

    Science.gov (United States)

    Scott, Erin; Allen, Mark B.; Macpherson, Colin; McCaffrey, Ken; Davidson, Jon; Saville, Christopher

    2017-04-01

    Orogenic plateaux are an ultimate expression of continental tectonics, but the timings and mechanisms of their formation are far from understood. The elevation history of the Andes is of particular importance for climatic reconstructions, as they pose the only barrier to atmospheric circulation in the Southern Hemisphere. Many varied techniques have been utilized over the last two decades to constrain Andean Plateau (AP) surface uplift. Two conflicting schools of thought are prominent: (1) recent, rapid rise since 10-6 Ma (Late Miocene), and (2) slow, continued uplift from 40 Ma. We propose a new, independent, approach to constrain AP surface uplift through time. By comparing isotopic compositions of Andean Quaternary arc lavas to present day crustal thickness and topography, we show that Sr and Nd isotopes are effective discriminants for the modern extent of the AP. As previously described, these isotopic systems are sensitive to crustal contamination, which in turn relates to crustal thickness, and, via isostasy, to regional surface elevation. We apply this relationship to a new compilation of published, age corrected, isotopic compositions of arc lavas, to constrain the surface uplift history of the Andes from the Jurassic to present day. Our results are consistent with significant AP surface uplift beginning in the Mid to Late Paleogene. We show that by 23 Ma, the AP was established at close to its modern elevations between at least 16-28 deg. S, thereby predating models for Late Miocene surface uplift. Between 23-10 Ma, surface uplift propagated south of 28 deg. S by a further 400 km. Our model has implications for understanding magma plumbing systems in regions of thick, wide crust, especially other orogenic plateaux.

  12. Wax Modeling and Image Analysis for Classroom-Scale Lava Flow Simulations.

    Science.gov (United States)

    Rader, E. L.; Clarke, A. B.; Vanderkluysen, L.

    2016-12-01

    The use of polyethylene glycol wax (PEG 600) as an analog for lava allows for a visual representation of the complex physical process occurring in natural lava flows, including cooling, breakouts, and crust and lobe formation. We used a series of cameras positioned around a tank filled with chilled water as a lab bench to observe and quantify lava flow morphology and motion. A peristaltic pump connected to a vent at the base of the tank delivered dyed wax simulating effusive eruptions similar to those of Kilauea in Hawai`i. By varying the eruptive conditions such as wax temperature and eruption rate, students can observe how the crust forms on wax flows, how different textures result, and how a flow field evolves with time. Recorded footage of the same `eruption' can then be quantitatively analyzed using free software like ImageJ and Tracker to quantify time-series of spreading rate, change in height, and appearance of different surface morphologies. Additional dye colors can be added periodically to further illustrate how lava is transported from the vent to the periphery of a flow field (e.g., through a tube system). Data collected from this activity can be compared to active lava flow footage from Hawai`i and with numerical models of lava flow propagation, followed by discussions of the application of these data and concepts to predicting the behavior of lava in hazard management situations and interpreting paleomagnetic, petrologic, and mapping of older eruptions.

  13. Growth rates of lava domes with respect to viscosity of magmas

    Directory of Open Access Journals (Sweden)

    I. Yokoyama

    2005-06-01

    Full Text Available In the discussion of lava dome formation, viscosity of magma plays an important role. Measurements of viscosity of magmas in field and laboratory are briefly summarized. The types of lava dome emplacements are classified into two, squeeze- and spine-type, by kinetic processes. The squeeze-type is the formation of a dome as a result of squeezes of magma through conduits and the latter is solidified magma forced to ascend by underlying fluid magma. An important parameter in the formation of such lava domes is their growth rates. Lava domes of squeeze-type are governed by the Hagen-Poiseuille Law which involves their viscosoties and other eruption parameters. At present, the real viscosity of magmas at the site of lava dome is still inaccessible. In order to avoid uncertainty in viscosity of magmas, a conception of «macroscopic viscosity» is proposed, which involves effects of chemical components, mainly SiO2 and volatile material, crystals and temperature, and their changes with time. Lava dome formations during the 20th century are briefly examined and their growth rates are estimated. The relationship between the growth rates and the SiO2 content of the magma is statistically studied, and the macroscopic viscosity is empirically expressed as a function of SiO2 content. The linearity between the two parameters is reasonably interpreted. This means that formation processes of lava domes are dominantly controlled by macroscopic viscosity of magma.

  14. Carbonatitic lavas in Catanda (Kwanza Sul, Angola): Mineralogical and geochemical constraints on the parental melt

    Science.gov (United States)

    Campeny, Marc; Kamenetsky, Vadim S.; Melgarejo, Joan C.; Mangas, José; Manuel, José; Alfonso, Pura; Kamenetsky, Maya B.; Bambi, Aurora C. J. M.; Gonçalves, Antonio O.

    2015-09-01

    A set of small volcanic edifices with tuff ring and maar morphologies occur in the Catanda area, which is the only locality with extrusive carbonatites reported in Angola. Four outcrops of carbonatite lavas have been identified in this region and considering the mineralogical, textural and compositional features, we classify them as: silicocarbonatites (1), calciocarbonatites (2) and secondary calciocarbonatites produced by the alteration of primary natrocarbonatites (3). Even with their differences, we interpret these lava types as having been a single carbonatite suite related to the same parental magma. We have also estimated the composition of the parental magma from a study of melt inclusions hosted in magnetite microphenocrysts from all of these lavas. Melt inclusions revealed the presence of 13 different alkali-rich phases (e.g., nyerereite, shortite, halite and sylvite) that argues for an alkaline composition of the Catanda parental melts. Mineralogical, textural, compositional and isotopic features of some Catanda lavas are also similar to those described in altered natrocarbonatite localities worldwide such as Tinderet or Kerimasi, leading to our conclusion that the formation of some Catanda calciocarbonatite lavas was related to the occurrence of natrocarbonatite volcanism in this area. On the other hand, silicocarbonatite lavas, which are enriched in periclase, present very different mineralogical, compositional and isotopic features in comparison to the rest of Catanda lavas. We conclude that its formation was probably related to the decarbonation of primary dolomite bearing carbonatites.

  15. Imaging the lithospheric structure of the High Lava Plains, Oregon with ambient noise tomography

    Science.gov (United States)

    Hanson-Hedgecock, S.; Wagner, L. S.; Fouch, M. J.

    2010-12-01

    We use ambient noise tomography (ANT) to image the 3-D structure of the crust and uppermost mantle beneath the High Lava Plains, Oregon using data from ~300 broadband stations of the High Lava Plains seismic experiment and the EarthScope/USArray Transportable Array (TA). The High Lava Plains consists of WNW progressive silicic volcanism, beginning ~14.5 Ma near the Owyhee Plateau and continuing to ~1.5 Ma in outpourings near the Newberry caldera. Superimposed basaltic volcanism has occurred along the hotspot since ~10.5 Ma. The Snake River Plain’s volcanism has been associated with a Yellowstone hot spot due to its alignment with North American plate motion, but the High Lava Plains volcanism does not have a comparably straightforward explanation. Recent results from a surface wave tomographic study of the Yellowstone/Snake River Plains (YSRP) reveal a discrete low velocity anomaly in the upper mantle that shallows to the northeast, consistent with plate motion over a stationary heat source. The same study shows a discontinuous low velocity anomaly beneath the High Lava Plains, indicating a less continuous east to west heat source along the HLP volcanic track. To better resolve the shallow velocity structure beneath the High Lava Plains, ANT is used to determine phase velocity maps at periods of formation of the High Lava Plains, Oregon.

  16. A review of mass and energy flow through a lava flow system: insights provided from a non-equilibrium perspective

    Science.gov (United States)

    Tarquini, Simone

    2017-08-01

    A simple formula relates lava discharge rate to the heat radiated per unit time from the surface of active lava flows (the "thermal proxy"). Although widely used, the physical basis of this proxy is still debated. In the present contribution, lava flows are approached as open, dissipative systems that, under favorable conditions, can attain a non-equilibrium stationary state. In this system framework, the onset, growth, and demise of lava flow units can be explained as a self-organization phenomenon characterized by a given temporal frequency defined by the average life span of active lava flow units. Here, I review empirical, physical, and experimental models designed to understand and link the flow of mass and energy through a lava flow system, as well as measurements and observations that support a "real-world" view. I set up two systems: active lava flow system (or ALFS) for flowing, fluid lava and a lava deposit system for solidified, cooling lava. The review highlights surprising similarities between lava flows and electric currents, which typically work under stationary conditions. An electric current propagates almost instantaneously through an existing circuit, following the Kirchhoff law (a least dissipation principle). Flowing lavas, in contrast, build up a slow-motion "lava circuit" over days, weeks, or months by following a gravity-driven path down the steepest slopes. Attainment of a steady-state condition is hampered (and the classic thermal proxy does not hold) if the supply stops before completion of the "lava circuit." Although gravity determines initial flow path and extension, the least dissipation principle means that subsequent evolution of mature portions of the active lava flow system is controlled by increasingly insulated conditions.

  17. Mapping lava flow textures using three-dimensional measures of surface roughness

    Science.gov (United States)

    Mallonee, H. C.; Kobs-Nawotniak, S. E.; McGregor, M.; Hughes, S. S.; Neish, C.; Downs, M.; Delparte, D.; Lim, D. S. S.; Heldmann, J. L.

    2016-12-01

    Lava flow emplacement conditions are reflected in the surface textures of a lava flow; unravelling these conditions is crucial to understanding the eruptive history and characteristics of basaltic volcanoes. Mapping lava flow textures using visual imagery alone is an inherently subjective process, as these images generally lack the resolution needed to make these determinations. Our team has begun mapping lava flow textures using visual spectrum imagery, which is an inherently subjective process involving the challenge of identifying transitional textures such as rubbly and slabby pāhoehoe, as these textures are similar in appearance and defined qualitatively. This is particularly problematic for interpreting planetary lava flow textures, where we have more limited data. We present a tool to objectively classify lava flow textures based on quantitative measures of roughness, including the 2D Hurst exponent, RMS height, and 2D:3D surface area ratio. We collected aerial images at Craters of the Moon National Monument (COTM) using Unmanned Aerial Vehicles (UAVs) in 2015 and 2016 as part of the FINESSE (Field Investigations to Enable Solar System Science and Exploration) and BASALT (Biologic Analog Science Associated with Lava Terrains) research projects. The aerial images were stitched together to create Digital Terrain Models (DTMs) with resolutions on the order of centimeters. The DTMs were evaluated by the classification tool described above, with output compared against field assessment of the texture. Further, the DTMs were downsampled and reevaluated to assess the efficacy of the classification tool at data resolutions similar to current datasets from other planetary bodies. This tool allows objective classification of lava flow texture, which enables more accurate interpretations of flow characteristics. This work also gives context for interpretations of flows with comparatively low data resolutions, such as those on the Moon and Mars. Textural maps based on

  18. Dating Young Lava Flows with Cosmogenic 36Cl: AN Example from the Late Pleistocene - Early Holocene ERCİYES Monogenetic Lava Domes in Central Turkey

    Science.gov (United States)

    Akif Sarıkaya, M.; Çiner, Attila; Şen, Erdal; Ersoy, Orkun; Zreda, Marek

    2017-04-01

    Precise dating of young lava flows is generally problematic because of the limiting factors of the applied technique. In-situ produced cosmogenic nuclides can be used to date very young lava flows if they show simple exposure histories and proper geochemistries. The Erciyes stratovolcano in the central Turkey has several dacite-rhyodacite monogenic parasitic lava domes that show clear exposure histories. Four young volcanic domes on the flanks of Erciyes Volcano have fresh-looking surfaces that are datable by cosmogenic surface exposure dating. We collected 36 cosmogenic samples from four lava flows namely Karagüllü, Perikartını, Dikkartın and Çarık, and obtained 36Cl exposure ages, all around Early Holocene, except for Çarık Lava flow which gave much older ages. Karagüllü, Perikartını and Dikkartın eruptions yielded average exposure ages at around 7.2±0.9 ka (n=11), 7.7±0.4 ka (n=6) and 8.8±0.6 ka (n=9), respectively. Two different eruption histories were determined from the Çarık Lava flow. They were centred at around 98.4±3.6 ka (n=7) and 36.1±1.1 ka (n=3). We also tested our results by an independent dating method. The Perikartını eruption generated a pyroclastic flow that buried trees that were converted to charcoal. Two charcoal samples found in this flow were dated using the 14C method, and yielded an average age of 9735±155 years BP (calibrated using Calib 7.1). Our results show that the cosmogenic 36Cl ages from Perikartını flow (7.7±0.4 ka) are younger than the radiocarbon ages (9.7±0.2 ka). This discrepancy might be related either to the high Cl content (963 ppm) of the lava flow or high nucleogenic production of 36Cl due to the above average U (5.1 ppm) and Th (15.6 ppm) concentrations. The high Cl content of the samples may result erroneously (>20%) underestimated the low-energy neutron capture (epithermal and thermal) production rates. On the other hand, the calculated nucleogenic 36Cl makes up almost one-third of the

  19. Lava field evolution and emplacement dynamics of the 2014-2015 basaltic fissure eruption at Holuhraun, Iceland

    Science.gov (United States)

    Pedersen, G. B. M.; Höskuldsson, A.; Dürig, T.; Thordarson, T.; Jónsdóttir, I.; Riishuus, M. S.; Óskarsson, B. V.; Dumont, S.; Magnusson, E.; Gudmundsson, M. T.; Sigmundsson, F.; Drouin, V. J. P. B.; Gallagher, C.; Askew, R.; Gudnason, J.; Moreland, W. M.; Nikkola, P.; Reynolds, H. I.; Schmith, J.

    2017-06-01

    The 6-month long eruption at Holuhraun (August 2014-February 2015) in the Bárðarbunga-Veiðivötn volcanic system was the largest effusive eruption in Iceland since the 1783-1784 CE Laki eruption. The lava flow field covered 84 km2 and has an estimated bulk (i.e., including vesicles) volume of 1.44 km3. The eruption had an average discharge rate of 90 m3/s making it the longest effusive eruption in modern times to sustain such high average flux. The first phase of the eruption (August 31, 2014 to mid-October 2014) had a discharge rate of 350 to 100 m3/s and was typified by lava transport via open channels and the formation of four lava flows, no. 1-4, which were emplaced side by side. The eruption began on a 1.8 km long fissure, feeding partly incandescent sheets of slabby pāhoehoe up to 500 m wide. By the following day the lava transport got confined to open channels and the dominant lava morphology changed to rubbly pāhoehoe and 'a'ā. The latter became the dominating morphology of lava flows no. 1-8. The second phase of the eruption (Mid-October to end November) had a discharge of 100-50 m3/s. During this time the lava transport system changed, via the formation of a system, which formed as lava ponded in the open lava channels creating sufficient lavastatic pressure in the fluid lava to lift the roof of the lava channels. This allowed new lava into the previously active lava channel lifting the channel roof via inflation. The final (third) phase, lasting from December to end-February 2015 had a mean discharge rate of 50 m3/s. In this phase the lava transport was mainly confined to lava tubes within lava flows no. 1-2, which fed breakouts that resurfaced > 19 km2 of the flow field. The primary lava morphology from this phase was spiny pāhoehoe, which superimposed on the 'a'ā lava flows no. 1-3 and extended the entire length of the flow field (i.e. 17 km). This made the 2014-2015 Holuhraun a paired flow field, where both lava morphologies had similar length

  20. Map showing lava inundation zones for Mauna Loa, Hawai'i

    Science.gov (United States)

    Trusdell, F.A.; Graves, P.; Tincher, C.R.

    2002-01-01

    The Island of Hawai‘i is composed of five coalesced basaltic volcanoes. Lava flows constitute the greatest volcanic hazard from these volcanoes. This report is concerned with lava flow hazards on Mauna Loa, the largest of the island shield volcanoes. Hilo lies 58 km from the summit of Mauna Loa, the Kona coast 33 km, and the southernmost point of the island 61 km.Hawaiian volcanoes erupt two morphologically distinct types of lava, aa and pahoehoe. The surfaces of pahoehoe flows are rather smooth and undulating. Pahoehoe flows are commonly fed by lava tubes, which are well insulated, lava-filled conduits contained within the flows. The surfaces of aa flows are extremely rough and composed of lava fragments. Aa flows usually form lava channels rather than lava tubes.In Hawai‘i, lava flows are known to reach distances of 50 km or more. The flows usually advance slowly enough that people can escape from their paths. Anything overwhelmed by a flow will be damaged or destroyed by burial, crushing, or ignition. Mauna Loa makes up 51 percent of the surface area of the Island of Hawai‘i. Geologic mapping shows that lava flows have covered more than 40 percent of the surface every 1,000 years. Since written descriptions of its activity began in A.D. 1832, Mauna Loa has erupted 33 times. Some eruptions begin with only brief seismic unrest, whereas others start several months to a year following increased seismic activity. Once underway, the eruptions can produce lava flows that reach the sea in less than 24 hours, severing roads and utilities. For example, the 1950 flows from the southwest rift zone reached the ocean in approximately three hours. The two longest flows of Mauna Loa are pahoehoe flows from the 50-kilometer-long 1859 and the 48-kilometer-long 1880-81 eruptions.Mauna Loa will undoubtedly erupt again. When it does, the first critical question that must be answered is: Which areas are threatened with inundation? Once the threatened areas are established, we

  1. L-Band Polarimetric SAR Signatures of Lava Flows in the Northern Volcanic Zone, Iceland

    DEFF Research Database (Denmark)

    Dierking, Wolfgang; Haack, Henning

    1998-01-01

    of polarimetric L-band radar signatures observed over different lava flows located in the Northern Volcanic Zone in Iceland. Intensity images with a high spatial resolution are well suited for geological interpretation, both in the discrimination of lava flows from the surrounding terrain and in the recognition......Studies of radar scattering signatures typical for lava surfaces are needed in order to interprete SAR images of volcanic terrain on the Earth and on other planets, and to establish a physical basis for the choice of optimal radar configurations for geological mapping. The authors focus on a study...

  2. RIS4E at Kilauea's December 1974 Flow: Lava Flow Texture LiDAR Signatures

    Science.gov (United States)

    Whelley, P.; Garry, W. B.; Scheidt, S. P.; Bleacher, J. E.; Hamilton, C.

    2015-12-01

    High-resolution point clouds and digital terrain models (DTMs) are used to investigate lava textures on the Big Island of Hawaii. Lava texture (e.g., ´áā and pāhoehoe) depends significantly on eruption conditions, and it is therefore instructive, if accurately determined. In places where field investigations are prohibitive (e.g., on other planets and remote regions of Earth) lava texture must be assessed from remote sensing data. A reliable method for doing so remains elusive. The December 1974 flow from Kilauea, in the Kau desert, presents an excellent field site to develop techniques for identifying lava texture. The eruption is young and the textures are well preserved. We present results comparing properties of lava textures observed in Terrestrial Laser Scanning (TLS) data. The authors collected the TLS data during May 2014 and June 2015 field seasons. Scans are a quantitative representation of what a geologist, or robotic system, sees "on the ground" and provides "ground truth" for airborne or orbital remote sensing analysis by enabling key parameters of lava morphology to be quantified. While individual scans have a heterogeneous point density, multiple scans are merged such that sub-cm lava textures can be quantified. Results indicate that TLS-derived surface roughness (i.e., de-trended RMS roughness) is useful for differentiating lava textures and assists volcanologic interpretations. As many lava types are quite rough, it is not simply roughness that is the most advantageous parameter for differentiating lava textures; rather co-occurrence patterns in surface roughness are used. Gradually forming textures (e.g., pāhoehoe) are elevated in statistics that measure smoothness (e.g., homogeneity) while lava with disrupted crusts (e.g., slabby and platy flow) have more random distributions of roughness (i.e., high entropy). A similar technique will be used to analyze high-resolution DTMs of martian lava flows using High Resolution Imaging Science

  3. Dynamics of a fluid flow on Mars: lava or mud?

    Science.gov (United States)

    Wilson, L.; Mouginis-Mark, P. J.

    2013-12-01

    We have identified an enigmatic flow in S.W. Cerberus Fossae, Mars. The flow originates from an almost circular pit within a remnant of a yardang at 0.58 degrees N, 155.28 degrees E, within the lower unit of the Medusae Fossae Formation. The flow is ~42 km long and 0.5 to 2.0 km wide. The surface textures of the resulting deposit show that the material flowed in such a way that the various deformation patterns on its surface were generally preserved as it moved, only being distorted or disrupted when the flow encountered major topographic obstacles or was forced to make rapid changes of direction. This observation of a stiff, generally undeformed surface layer overlying a relatively mobile base suggests that, while it was moving, the fluid material flowed in a laminar, and possibly non-Newtonian, fashion. The least-complicated non-Newtonian fluids are Bingham plastics. On this basis we use measurements of flow width, length, thickness and substrate slope obtained from images, a DEM constructed from stereo pairs of Context Camera (CTX) images, and Mars Orbiter Laser Altimeter (MOLA) altimetry points to deduce the rheological properties of the fluid, treating it as both a Newtonian and a Bingham material for comparison. The Newtonian option requires the fluid to have a viscosity close to 100 Pa s and to have flowed everywhere in a turbulent fashion. The Bingham option requires laminar flow, a plastic viscosity close to 1 Pa s, and a yield strength of ~185 Pa. We compare these parameters values with those of various environmental fluids on Earth in an attempt to narrow the range of possible materials forming the martian flow. A mafic to ultramafic lava would fit the Newtonian option but the required turbulence does not seem consistent with the surface textures. The Bingham option satisfies the morphological constraint of laminar motion if the material is a mud flow consisting of ~40% water and ~60% silt-sized silicate solids. Elsewhere on Mars, deposits with similar

  4. Observations on lava, snowpack and their interactions during the 2012-13 Tolbachik eruption, Klyuchevskoy Group, Kamchatka, Russia

    Science.gov (United States)

    Edwards, Benjamin R.; Belousov, Alexander; Belousova, Marina; Melnikov, Dmitry

    2015-12-01

    Observations made during January and April 2013 show that interactions between lava flows and snowpack during the 2012-13 Tolbachik fissure eruption in Kamchatka, Russia, were controlled by different styles of emplacement and flow velocities. `A`a lava flows and sheet lava flows generally moved on top of the snowpack with few immediate signs of interaction besides localized steaming. However, lavas melted through underlying snowpack 1-4 m thick within 12 to 24 h, and melt water flowed episodically from the beneath flows. Pahoehoe lava lobes had lower velocities and locally moved beneath/within the snowpack; even there the snow melting was limited. Snowpack responses were physical, including compressional buckling and doming, and thermal, including partial and complete melting. Maximum lava temperatures were up to 1355 K (1082 °C; type K thermal probes), and maximum measured meltwater temperatures were 335 K (62.7 °C). Theoretical estimates for rates of rapid (e.g., radiative) and slower (conductive) snowmelt are consistent with field observations showing that lava advance was fast enough for `a`a and sheet flows to move on top of the snowpack. At least two styles of physical interactions between lava flows and snowpack observed at Tolbachik have not been previously reported: migration of lava flows beneath the snowpack, and localized phreatomagmatic explosions caused by snowpack failure beneath lava. The distinctive morphologies of sub-snowpack lava flows have a high preservation potential and can be used to document snowpack emplacement during eruptions.

  5. Effect of the radiation in the thermoluminescent properties of lava

    CERN Document Server

    Correcher, V; García, J

    2003-01-01

    Blue thermoluminescence (Tl) emission from different lavas of many places (Costa Rica, Canary Islands, Hawaii Islands, Iceland and Italy) corresponding to different eruptions has been studied to know its potential use in the field of dating and retrospective dosimetry. Due to the light emission is linked to the point defects of the crystalline lattice structure, X-ray diffraction analyses were performed to determine the components of this poly mineral material that mostly are cristobalite, plagioclase and phyllosilicates. Exposures to different doses (in a range of 1-25 Gy) were given to each sample to determine the evolution of the Tl signal with the irradiation under laboratory conditions. In all cases, a linear response could be observed and no saturation has been detected in this range of doses. Both natural (NTL) and induced (ITL) Tl signal exhibit a complex glow curve structure associated to a continuous trap distribution over 100 C that could be attributed to the formation-annihilation [Al0 sub 4 /alka...

  6. Dielectric properties of lava flows west of Ascraeus Mons, Mars

    Science.gov (United States)

    Carter, L.M.; Campbell, B.A.; Holt, J.W.; Phillips, R.J.; Putzig, N.E.; Mattei, S.; Seu, R.; Okubo, C.H.; Egan, A.F.

    2009-01-01

    The SHARAD instrument on the Mars Reconnaissance Orbiter detects subsurface interfaces beneath lava flow fields northwest of Ascraeus Mons. The interfaces occur in two locations; a northern flow that originates south of Alba Patera, and a southern flow that originates at the rift zone between Ascraeus and Pavonis Montes. The northern flow has permittivity values, estimated from the time delay of echoes from the basal interface, between 6.2 and 17.3, with an average of 12.2. The southern flow has permittivity values of 7.0 to 14.0, with an average of 9.8. The average permittivity values for the northern and southern flows imply densities of 3.7 and 3.4 g cm-3, respectively. Loss tangent values for both flows range from 0.01 to 0.03. The measured bulk permittivity and loss tangent values are consistent with those of terrestrial and lunar basalts, and represent the first measurement of these properties for dense rock on Mars. Copyright 2009 by the American Geophysical Union.

  7. 40Ar-39Ar age of a lava flow from the Bhimashankar Formation ...

    Indian Academy of Sciences (India)

    39Ar age of a lava flow from the Bhimashankar Formation, Giravali Ghat, Deccan Traps. Kanchan Pande S K Pattanayak K V Subbarao P Navaneethakrishnan T R Venkatesan. Volume 113 Issue 4 December 2004 pp 755-758 ...

  8. Lava lake level as a gauge of magma reservoir pressure and eruptive hazard

    Science.gov (United States)

    Patrick, Matthew R.; Anderson, Kyle R.; Poland, Michael P.; Orr, Tim R.; Swanson, Donald A.

    2015-01-01

    Forecasting volcanic activity relies fundamentally on tracking magma pressure through the use of proxies, such as ground surface deformation and earthquake rates. Lava lakes at open-vent basaltic volcanoes provide a window into the uppermost magma system for gauging reservoir pressure changes more directly. At Kīlauea Volcano (Hawaiʻi, USA) the surface height of the summit lava lake in Halemaʻumaʻu Crater fluctuates with surface deformation over short (hours to days) and long (weeks to months) time scales. This correlation implies that the lake behaves as a simple piezometer of the subsurface magma reservoir. Changes in lava level and summit deformation scale with (and shortly precede) changes in eruption rate from Kīlauea's East Rift Zone, indicating that summit lava level can be used for short-term forecasting of rift zone activity and associated hazards at Kīlauea.

  9. Real-time satellite monitoring of Nornahraun lava flow NE Iceland

    Science.gov (United States)

    Jónsdóttir, Ingibjörg; Þórðarson, Þorvaldur; Höskuldsson, Ármann; Davis, Ashley; Schneider, David; Wright, Robert; Kestay, Laszlo; Hamilton, Christopher; Harris, Andrew; Coppola, Diego; Tumi Guðmundsson, Magnús; Durig, Tobias; Pedersen, Gro; Drouin, Vincent; Höskuldsson, Friðrik; Símonarson, Hreggviður; Örn Arnarson, Gunnar; Örn Einarsson, Magnús; Riishuus, Morten

    2015-04-01

    An effusive eruption started in Holuhraun, NE Iceland, on 31 August 2014, producing the Nornahraun lava flow field which had, by the beginning of 2015, covered over 83 km2. Throughout this event, various satellite images have been analyzed to monitor the development, active areas and map the lava extent in close collaboration with the field group, which involved regular exchange of direct observations and satellite based data for ground truthing and suggesting possible sites for lava sampling. From the beginning, satellite images in low geometric but high temporal resolution (NOAA AVHRR, MODIS) were used to monitor main regions of activity and position new vents to within 1km accuracy. As they became available, multispectral images in higher resolution (LANDSAT 8, LANDSAT 7, ASTER, EO-1 ALI) were used to map the lava channels, study lava structures and classify regions of varying activity. Hyper spectral sensors (EO-1 HYPERION), though with limited area coverage, have given a good indication of vent and lava temperature and effusion rates. All available radar imagery (SENTINEL-1, RADARSAT, COSMO SKYMED, TERRASAR X) have been used for studying lava extent, landscape and roughness. The Icelandic Coast Guard has, on a number of occasions, provided high resolution radar and thermal images from reconnaissance flights. These data sources compliment each other well and have improved analysis of events. Whilst classical TIR channels were utilized to map the temperature history of the lava, SWIR and NIR channels caught regions of highest temperature, allowing an estimate of the most active lava channels and even indicating potential changes in channel structure. Combining thermal images and radar images took this prediction a step further, improving interpretation of both image types and studying the difference between open and closed lava channels. Efforts are underway of comparing different methods of estimating magma discharge and improving the process for use in real

  10. The Chaitén rhyolite lava dome: Eruption sequence, lava dome volumes, rapid effusion rates and source of the rhyolite magma

    Science.gov (United States)

    Pallister, John S.; Diefenbach, Angela K.; Burton, William C.; Munoz, Jorge; Griswold, Julia P.; Lara, Luis E.; Lowenstern, Jacob B.; Valenzuela, Carolina E.

    2013-01-01

    We use geologic field mapping and sampling, photogrammetric analysis of oblique aerial photographs, and digital elevation models to document the 2008-2009 eruptive sequence at Chaitén Volcano and to estimate volumes and effusion rates for the lava dome. We also present geochemical and petrologic data that contribute to understanding the source of the rhyolite and its unusually rapid effusion rates. The eruption consisted of five major phases: 1. An explosive phase (1-11 May 2008); 2. A transitional phase (11-31 May 2008) in which low-altitude tephra columns and simultaneous lava extrusion took place; 3. An exogenous lava flow phase (June-September 2008); 4. A spine extrusion and endogenous growth phase (October 2008-February 2009); and 5. A mainly endogenous growth phase that began after the collapse of a prominent Peléean spine on 19 February 2009 and continued until the end of the eruption (late 2009 or possibly earliest 2010). The 2008-2009 rhyolite lava dome has a total volume of approximately 0.8 km3. The effusion rate averaged 66 m3s-1 during the first two weeks and averaged 45 m3s-1 for the first four months of the eruption, during which 0.5 km3 of rhyolite lava was erupted. These are among the highest rates measured world-wide for historical eruptions of silicic lava. Chaitén’s 2008-2009 lava is phenocryst-poor obsidian and microcrystalline rhyolite with 75.3±0.3% SiO2. The lava was erupted at relatively high temperature and is remarkably similar in composition and petrography to Chaitén’s pre-historic rhyolite. The rhyolite’s normative composition plots close to that of low pressure (100-200 MPa) minimum melts in the granite system, consistent with estimates of approximately 5 to 10 km source depths based on phase equilibria and geodetic studies. Calcic plagioclase, magnesian orthopyroxene and aluminous amphibole among the sparse phenocrysts suggest derivation of the rhyolite by melt extraction from a more mafic magmatic mush. High temperature

  11. Preliminary results from an integrated, multi-parameter, experiment at the Santiaguito lava dome complex, Guatemala

    Science.gov (United States)

    De Angelis, S.; Rietbrock, A.; Lavallée, Y.; Lamb, O. D.; Lamur, A.; Kendrick, J. E.; Hornby, A. J.; von Aulock, F. W.; Chigna, G.

    2016-12-01

    Understanding the complex processes that drive volcanic unrest is crucial to effective risk mitigation. Characterization of these processes, and the mechanisms of volcanic eruptions, is only possible when high-resolution geophysical and geological observations are available over comparatively long periods of time. In November 2014, the Liverpool Earth Observatory, UK, in collaboration with the Instituto Nacional de Sismologia, Meteorologia e Hidrologia (INSIVUMEH), Guatemala, established a multi-parameter geophysical network at Santiaguito, one of the most active volcanoes in Guatemala. Activity at Santiaguito throughout the past decade, until the summer of 2015, was characterized by nearly continuous lava dome extrusion accompanied by frequent and regular small-to-moderate gas or gas-and-ash explosions. Over the past two years our network collected a wealth of seismic, acoustic and deformation data, complemented by campaign visual and thermal infrared measurements, and rock and ash samples. Here we present preliminary results from the analysis of this unique dataset. Using acoustic and thermal data collected during 2014-2015 we were able to assess volume fractions of ash and gas in the eruptive plumes. The small proportion of ash inferred in the plumes confirms estimates from previous, independent, studies, and suggests that these events did not involve significant magma fragmentation in the conduit. The results also agree with the suggestion that sacrificial fragmentation along fault zones in the conduit region, due to shear-induced thermal vesiculation, may be at the origin of such events. Finally, starting in the summer of 2015, our experiment captured the transition to a new phase of activity characterized by vigorous vulcanian-style explosions producing large, ash-rich, plumes and frequent hazardous pyroclastic flows, as well as the formation a large summit crater. We present evidence of this transition in the geophysical and geological data, and discuss its

  12. Memories of Earth Formation in the Modern Mantle: W Isotopic Composition of Flood Basalt Lavas

    Science.gov (United States)

    Rizo Garza, H. L.; Walker, R. J.; Carlson, R.; Horan, M. F.; Mukhopadhyay, S.; Francis, D.; Jackson, M. G.

    2015-12-01

    Four and a half billion years of geologic activity has overprinted much of the direct evidence for processes involved in Earth's formation and its initial chemical differentiation. Xenon isotopic ratios [1] and 3He/22Ne ratios [2] suggest that heterogeneities formed during Earth's accretion have been preserved to the present time. New opportunities to learn about early Earth history have opened up with the development of analytical techniques that allow high precision analysis of short-lived isotopic systems. The Hf-W system (t½ = 8.9 Ma) is particularly valuable for studying events that occurred during the first ~50 Ma of Solar System history. Here we report new data for ~ 60 Ma Baffin Bay and ~ 120 Ma Ontong Java Plateau lava samples. Both are large igneous provinces that may have sampled a primitive, less degassed deep mantle reservoir that has remained isolated since shortly after Earth formation [3,4]. Three samples analyzed have 182W/184W ratios that are 10 to 48 ppm higher than our terrestrial standard. These excesses in 182W are the highest ever measured in terrestrial rocks, and may reflect 182W ingrowth in an early-formed high Hf/W mantle domain that was produced by magma ocean differentiation [5]. Long and short-lived Sm-Nd systematics in these samples, however, are inconsistent with this hypothesis. The 182W excessses could rather reflect the derivation of these lavas from a mantle reservoir that was isolated from late accretionary additions [6]. The chondritic initial Os isotopic compositions and highly siderophile element abundances of these samples, however, are inconsistent with this interpretation. Tungsten concentrations for the Baffin Bay and Ontong Java Plateau samples range from 23 ppb to 62 ppb, and are negatively correlated with their 182W/184W ratios. We propose that the source reservoirs for these flood basalts likely formed through Hf/W fractionation caused by core-forming events occuring over a protacted time interval during Earth

  13. Elemental and Topographic Mapping of Lava Flowstructures in Mare Serenitatis on the Moon

    Science.gov (United States)

    Wöhler, C.; Grumpe, A.; Rommel, D.; Bhatt, M.; Mall, U.

    2017-07-01

    The detection of lunar lava flows based on local morphology highly depends on the available images. The thickness of lava flows, however, has been studied by many researchers and lunar lava flows are shown to be as thick as 200 m. Lunar lava flows are supposed to be concentrated on the northwestern lunar nearside. In this study we present elemental abundance maps, a petrological map and a digital terrain model (DTM) of a lava flow structure in northern Mare Serenitatis at (18.0° E, 32.4° N) and two possible volcanic vents at (11.2° E, 24.6° N) and (13.5° E, 37.5° N), respectively. Our abundance maps of the refractory elements Ca, Mg and our petrological map were obtained based on hyperspectral image data of the Moon Mineralogy Mapper (M3) instrument. Our DTM was constructed using GLD100 data in combination with a shape from shading based method to M3 and Lunar Reconnaissance Orbiter (LRO) Narrow Angle Camera (NAC) image data. The obtained NAC-based DEM has a very high effective resolution of about 1-2 m which comes close to the resolution of the utilized NAC images without requiring intricate processing of NAC stereo image pairs. As revealed by our elemental maps and DEM, the examined lava flow structure occurs on a boundary between basalts consisting of low-Ca/high-Mg pyroxene and high-Ca/low-Mg pyroxene, respectively. The total thickness of the lava flow is about 100 m, which is a relatively large value, but according to our DEM the lava flow may also be composed of two or more layers.

  14. Dacitic glassy lava flow from Trlično at Rogatec, Eastern Slovenia

    Directory of Open Access Journals (Sweden)

    Polona Kralj

    2002-06-01

    Full Text Available Glassy lava from Trlično is dacitic in composition and developed by incomplete mixing of two magmas of similar composition but different degree of groundmass crystallinity.By laminar lava flow banded texture developed consisting of bands with different magma types. Abundance of major and trace elements is within the variation range for dacites. Comparison with the Smrekovec andesites in Northern Slovenia indicates that the rocks do not originate from the same volcanic complex, displaced by tectonic activity.

  15. Retrospective validation of a lava-flow hazard map for Mount Etna volcano

    Directory of Open Access Journals (Sweden)

    Ciro Del Negro

    2011-12-01

    Full Text Available This report presents a retrospective methodology to validate a long-term hazard map related to lava-flow invasion at Mount Etna, the most active volcano in Europe. A lava-flow hazard map provides the probability that a specific point will be affected by potential destructive volcanic processes over the time period considered. We constructed this lava-flow hazard map for Mount Etna volcano through the identification of the emission regions with the highest probabilities of eruptive vents and through characterization of the event types for the numerical simulations and the computation of the eruptive probabilities. Numerical simulations of lava-flow paths were carried out using the MAGFLOW cellular automata model. To validate the methodology developed, a hazard map was built by considering only the eruptions that occurred at Mount Etna before 1981. On the basis of the probability of coverage by lava flows, the map was divided into ten classes, and two fitting scores were calculated to measure the overlap between the hazard classes and the actual shapes of the lava flows that occurred after 1981.

  16. Comparison of Bacterial Diversity in Azorean and Hawai’ian Lava Cave Microbial Mats

    Science.gov (United States)

    MARSHALL HATHAWAY, JENNIFER J.; GARCIA, MATTHEW G.; BALASCH, MONICA MOYA; SPILDE, MICHAEL N.; STONE, FRED D.; DAPKEVICIUS, MARIA DE LURDES N. E.; AMORIM, ISABEL R.; GABRIEL, ROSALINA; BORGES, PAULO A. V.; NORTHUP, DIANA E.

    2015-01-01

    Worldwide, lava caves host colorful microbial mats. However, little is known about the diversity of these microorganisms, or what role they may play in the subsurface ecosystem. White and yellow microbial mats were collected from four lava caves each on the Azorean island of Terceira and the Big Island of Hawai’i, to compare the bacterial diversity found in lava caves from two widely separated archipelagos in two different oceans at different latitudes. Scanning electron microscopy of mat samples showed striking similarities between Terceira and Hawai’ian microbial morphologies. 16S rRNA gene clone libraries were constructed to determine the diversity within these lava caves. Fifteen bacterial phyla were found across the samples, with more Actinobacteria clones in Hawai’ian communities and greater numbers of Acidobacteria clones in Terceira communities. Bacterial diversity in the subsurface was correlated with a set of factors. Geographical location was the major contributor to differences in community composition (at the OTU level), together with differences in the amounts of organic carbon, nitrogen and copper available in the lava rock that forms the cave. These results reveal, for the first time, the similarity among the extensive bacterial diversity found in lava caves in two geographically separate locations and contribute to the current debate on the nature of microbial biogeography. PMID:26924866

  17. Monitoring the cooling of the 1959 Kīlauea Iki lava lake using surface magnetic measurements

    Science.gov (United States)

    Gailler, Lydie; Kauahikaua, Jim

    2017-06-01

    Lava lakes can be considered as proxies for small magma chambers, offering a unique opportunity to investigate magma evolution and solidification. Repeated magnetic ground surveys over more than 50 years each show a large vertical magnetic intensity anomaly associated with Kīlauea Iki Crater, partly filled with a lava lake during the 1959 eruption of Kīlauea Volcano (Island of Hawai'i). The magnetic field values recorded across the Kīlauea Iki crater floor and the cooling lava lake below result from three simple effects: the static remnant magnetization of the rocks forming the steep crater walls, the solidifying lava lake crust, and the hot, but shrinking, paramagnetic non-magnetic lens (>540 °C). We calculate 2D magnetic models to reconstruct the temporal evolution of the geometry of this non-magnetic body, its depth below the surface, and its thickness. Our results are in good agreement with the theoretical increase in thickness of the solidifying crust with time. Using the 2D magnetic models and the theoretical curve for crustal growth over a lava lake, we estimate that the former lava lake will be totally cooled below the Curie temperature in about 20 years. This study shows the potential of magnetic methods for detecting and monitoring magmatic intrusions at various scales.

  18. Monitoring the cooling of the 1959 Kīlauea Iki lava lake using surface magnetic measurements

    Science.gov (United States)

    Gailler, Lydie; Kauahikaua, James P.

    2017-01-01

    Lava lakes can be considered as proxies for small magma chambers, offering a unique opportunity to investigate magma evolution and solidification. Repeated magnetic ground surveys over more than 50 years each show a large vertical magnetic intensity anomaly associated with Kīlauea Iki Crater, partly filled with a lava lake during the 1959 eruption of Kīlauea Volcano (Island of Hawai’i). The magnetic field values recorded across the Kīlauea Iki crater floor and the cooling lava lake below result from three simple effects: the static remnant magnetization of the rocks forming the steep crater walls, the solidifying lava lake crust, and the hot, but shrinking, paramagnetic non-magnetic lens (>540 °C). We calculate 2D magnetic models to reconstruct the temporal evolution of the geometry of this non-magnetic body, its depth below the surface, and its thickness. Our results are in good agreement with the theoretical increase in thickness of the solidifying crust with time. Using the 2D magnetic models and the theoretical curve for crustal growth over a lava lake, we estimate that the former lava lake will be totally cooled below the Curie temperature in about 20 years. This study shows the potential of magnetic methods for detecting and monitoring magmatic intrusions at various scales.

  19. Tracking the hidden growth of a lava flow field: the 2014-15 eruption of Fogo volcano (Cape Verde)

    Science.gov (United States)

    Silva, Sonia; Calvari, Sonia; Hernandez, Pedro; Perez, Nemesio; Ganci, Gaetana; Alfama, Vera; Barrancos, José; Cabral, Jeremias; Cardoso, Nadir; Dionis, Samara; Fernandes, Paulo; Melian, Gladys; Pereira, José; Semedo, Hélio; Padilla, German; Rodriguez, Fatima

    2017-04-01

    Fogo volcano erupted in 2014-15 producing an extensive lava flow field in the summit caldera that destroyed two villages, Portela and Bangaeira. The eruption started with powerful explosive activity, lava fountaining, and a substantial ash column accompanying the opening of an eruptive fissure. Lava flows spreading from the base of the eruptive fissure produced three arterial lava flows, spreading S (Flow 1), N-NW (Flow 2) and W (Flow 3). By a week after the start of the eruption, a master lava tube had already developed within the eruptive fissure and along Flow 2. When Flow 2 front stopped against the N caldera cliff, the whole flow field behind it inflated, and eventually its partial drainage produced a short tube that fed Flow 3, but no lava tube formed within Flow 1. Here we analyze the emplacement processes on the basis of observations carried out directly on the lava flow field and through satellite image, in order to unravel the key factors leading to the development of lava tubes. These tubes were responsible for the rapid expansion of lava for the 7.9 km length of the flow field, as well as the destruction of the Portela and Bangaeira villages. Comparing time-averaged effusion rates (TADR) obtained from satellite and Supply Rate (SR) derived from SO2 flux data, we estimate the amount and timing of the lava flow field endogenous growth, with the aim of developing a tool that could be used for risk mitigation at this and other volcanoes.

  20. Basalt: Biologic Analog Science Associated with Lava Terrains

    Science.gov (United States)

    Lim, D. S. S.; Abercromby, A.; Kobs-Nawotniak, S. E.; Kobayashi, L.; Hughes, S. S.; Chappell, S.; Bramall, N. E.; Deans, M. C.; Heldmann, J. L.; Downs, M.; Cockell, C. S.; Stevens, A. H.; Caldwell, B.; Hoffman, J.; Vadhavk, N.; Marquez, J.; Miller, M.; Squyres, S. W.; Lees, D. S.; Fong, T.; Cohen, T.; Smith, T.; Lee, G.; Frank, J.; Colaprete, A.

    2015-12-01

    This presentation will provide an overview of the BASALT (Biologic Analog Science Associated with Lava Terrains) program. BASALT research addresses Science, Science Operations, and Technology. Specifically, BASALT is focused on the investigation of terrestrial volcanic terrains and their habitability as analog environments for early and present-day Mars. Our scientific fieldwork is conducted under simulated Mars mission constraints to evaluate strategically selected concepts of operations (ConOps) and capabilities with respect to their anticipated value for the joint human and robotic exploration of Mars. a) Science: The BASALT science program is focused on understanding habitability conditions of early and present-day Mars in two relevant Mars-analog locations (the Southwest Rift Zone (SWRZ) and the East Rift Zone (ERZ) flows on the Big Island of Hawai'i and the eastern Snake River Plain (ESRP) in Idaho) to characterize and compare the physical and geochemical conditions of life in these environments and to learn how to seek, identify, and characterize life and life-related chemistry in basaltic environments representing these two epochs of martian history. b) Science Operations: The BASALT team will conduct real (non-simulated) biological and geological science at two high-fidelity Mars analogs, all within simulated Mars mission conditions (including communication latencies and bandwidth constraints) that are based on current architectural assumptions for Mars exploration missions. We will identify which human-robotic ConOps and supporting capabilities enable science return and discovery. c) Technology: BASALT will incorporate and evaluate technologies in to our field operations that are directly relevant to conducting the scientific investigations regarding life and life-related chemistry in Mars-analogous terrestrial environments. BASALT technologies include the use of mobile science platforms, extravehicular informatics, display technologies, communication

  1. Morphologic and thermophysical characteristics of lava flows southwest of Arsia Mons, Mars

    Science.gov (United States)

    Crown, David A.; Ramsey, Michael S.

    2017-08-01

    The morphologic and thermophysical characteristics of part of the extensive lava flow fields southwest of Arsia Mons (22.5-27.5°S, 120-130°W) have been examined using a combination of orbital VNIR and TIR datasets. THEMIS images provide context for the regional geology and record diurnal temperature variability that is diverse and unusual for flow surfaces in such close proximity. CTX images were used to distinguish dominant flow types and assess local age relationships between individual lava flows. CTX and HiRISE images provide detailed information on flow surface textures and document aeolian effects as they reveal fine-grained deposits in many low-lying areas of the flow surfaces as well as small patches of transverse aeolian ridges. Although this region is generally dust-covered and has a lower overall thermal inertia, the THEMIS data indicate subtle spectral variations within the population of lava flows studied. These variations could be due to compositional differences among the flows or related to mixing of flow and aeolian materials. Specific results regarding flow morphology include: a) Two main lava flow types (bright, rugged and dark, smooth as observed in CTX images) dominate the southwest Arsia Mons/NE Daedalia Planum region; b) the bright, rugged flows have knobby, ridged, and/or platy surface textures, commonly have medial channel/levee systems, and may have broad distal lobes; c) the dark, smooth flows extend from distributary systems that consist of combinations of lava channels, lava tubes, and/or sinuous ridges and plateaus; and d) steep-sided, terraced margins, digitate breakout lobes, and smooth-surfaced plateaus along lava channel/tube systems are interpreted as signatures of flow inflation within the dark, smooth flow type. These flows exhibit smoother upper surfaces, are thinner, and have more numerous, smaller lobes, which, along with their the channel-/tube-fed nature, indicate a lower viscosity lava than for the bright, rugged flows

  2. Transition of basaltic lava from pahoehoe to aa, Kilauea Volcano, Hawaii: Field observations and key factors

    Science.gov (United States)

    Peterson, Donald W.; Tilling, Robert I.

    1980-01-01

    Nearly all Hawaiian basaltic lava erupts as pahoehoe, and some changes to aa during flowage and cooling; factors governing the transition involve certain critical relations between viscosity and rate of shear strain. If the lava slows, cools, and stops in direct response to concomitant increase in viscosity before these critical relations are reached, it remains pahoehoe. But, if flow mechanics (flow rate, flow dimensions, slope, momentum, etc.) impel the lava to continue to move and deform even after it has become highly viscous, the critical relations may be reached and the lava changes to aa.Typical modes of transition from pahoehoe to aa include: (1) spontaneous formation of relatively stiff clots in parts of the flowing lava where shear rate is highest; these clots grow into discrete, rough, sticky masses to which the remaining fluid lava incrementally adheres; (2) fragmentation and immersion of solid or semi-solid surface crusts of pahoehoe by roiling movements of the flow, forming cores of discrete, tacky masses; (3) sudden renewed movement of lava stored and cooled within surface reservoirs to form clots. The masses, fragments, and clots in these transition modes are characterized by spinose, granulated surfaces; as flow movement continues, the masses and fragments aggregate, fracture, and grind together, completing the transition to aa.Observations show that the critical relation between viscosity and rate of shear strain is inverse: if viscosity is low, a high rate of shear is required to begin the transition to aa; conversely, if viscosity is high, a much lower rate of shear will induce the transition. These relations can be demonstrated qualitatively with simple graphs, which can be used to examine the flow history of any selected finite lava element by tracing the path represented by its changing viscosity and shear rate. A broad, diffuse “transition threshold zone” in these graphs portrays the inverse critical relation between viscosity and shear

  3. Zoned high-pressure assemblages in pillow lavas of the Zermatt-Saas ophiolite zone, Switzerland

    Science.gov (United States)

    Barnicoat, A. C.

    1988-03-01

    Pillow lavas of the Zermatt-Saas ophiolite zone of the western Swiss Alps in places consist of zoned high-pressure parageneses. These assemblages, which developed subsequent to the metamorphic peak, are of lawsonite eclogite in the cores of pillows and dolomite-bearing blueschist or glaucophane eclogite in the rims. The matrix between the pillows comprises dolomite-glaucophane-rich material. An analysis of reactions in the system Na 2OCaOFeOMgOAl 2O 3SiO 2H 2OCO 2 (NCFMAS-H 2OCO 2) indicates that one possible model is that these assemblages formed cofacially due to systematic intra-pillow variations in the chemical potentials of H 2O and CO 2. Pillow rims equilibrated at higher values of μCO 2 and lower values of μH 2O than pillow cores. Textural evidence suggests that infiltration has controlled the distribution of CO 2 generated by the breakdown of dolomite-bearing assemblages during the return of the rocks to the surface. Variation in H 2O content was caused by ocean-floor hydrothermal alteration. In these rocks, therefore, blueschist assemblages have been stabilised by higher values of μCO 2 and eclogites by higher values of μH 2O . If fluids were present (as suggested by various lines of evidence) then blueschist pillow rims equilibrated at higher {CO2}/{( CO2+ H2O) } than eclogitic pillow cores.

  4. Benchmarking computational fluid dynamics models of lava flow simulation for hazard assessment, forecasting, and risk management

    Science.gov (United States)

    Dietterich, Hannah; Lev, Einat; Chen, Jiangzhi; Richardson, Jacob A.; Cashman, Katharine V.

    2017-01-01

    Numerical simulations of lava flow emplacement are valuable for assessing lava flow hazards, forecasting active flows, designing flow mitigation measures, interpreting past eruptions, and understanding the controls on lava flow behavior. Existing lava flow models vary in simplifying assumptions, physics, dimensionality, and the degree to which they have been validated against analytical solutions, experiments, and natural observations. In order to assess existing models and guide the development of new codes, we conduct a benchmarking study of computational fluid dynamics (CFD) models for lava flow emplacement, including VolcFlow, OpenFOAM, FLOW-3D, COMSOL, and MOLASSES. We model viscous, cooling, and solidifying flows over horizontal planes, sloping surfaces, and into topographic obstacles. We compare model results to physical observations made during well-controlled analogue and molten basalt experiments, and to analytical theory when available. Overall, the models accurately simulate viscous flow with some variability in flow thickness where flows intersect obstacles. OpenFOAM, COMSOL, and FLOW-3D can each reproduce experimental measurements of cooling viscous flows, and OpenFOAM and FLOW-3D simulations with temperature-dependent rheology match results from molten basalt experiments. We assess the goodness-of-fit of the simulation results and the computational cost. Our results guide the selection of numerical simulation codes for different applications, including inferring emplacement conditions of past lava flows, modeling the temporal evolution of ongoing flows during eruption, and probabilistic assessment of lava flow hazard prior to eruption. Finally, we outline potential experiments and desired key observational data from future flows that would extend existing benchmarking data sets.

  5. Limited role for thermal erosion by turbulent lava in proximal Athabasca Valles, Mars

    Science.gov (United States)

    Cataldo, Vincenzo; Williams, David A.; Dundas, Colin M.; Kestay, Laszlo P.

    2015-01-01

    The Athabasca Valles flood lava is among the most recent (Mars and was probably emplaced turbulently. The Williams et al. (2005) model of thermal erosion by lava has been applied to what we term “proximal Athabasca,” the 75 km long upstream portion of Athabasca Valles. For emplacement volumes of 5000 and 7500 km3and average flow thicknesses of 20 and 30 m, the duration of the eruption varies between ~11 and ~37 days. The erosion of the lava flow substrate is investigated for three eruption temperatures (1270°C, 1260°C, and 1250°C), and volatile contents equivalent to 0–65 vol % bubbles. The largest erosion depths of ~3.8–7.5 m are at the lava source, for 20 m thick and bubble-free flows that erupted at their liquidus temperature (1270°C). A substrate containing 25 vol % ice leads to maximum erosion. A lava temperature 20°C below liquidus reduces erosion depths by a factor of ~2.2. If flow viscosity increases with increasing bubble content in the lava, the presence of 30–50 vol % bubbles leads to erosion depths lower than those relative to bubble-free lava by a factor of ~2.4. The presence of 25 vol % ice in the substrate increases erosion depths by a factor of 1.3. Nevertheless, modeled erosion depths, consistent with the emplacement volume and flow duration constraints, are far less than the depth of the channel (~35–100 m). We conclude that thermal erosion does not appear to have had a major role in excavating Athabasca Valles.

  6. Volcanic risk: mitigation of lava flow invasion hazard through optimized barrier configuration

    Science.gov (United States)

    Scifoni, S.; Coltelli, M.; Marsella, M.; Napoleoni, Q.; Del Negro, C.; Proietti, C.; Vicari, A.

    2009-04-01

    In order to mitigate the destructive effects of lava flows along volcanic slopes, the building of artificial barriers is a fundamental action for controlling and slowing down the lava flow advance, as experienced during a few recent eruptions of Etna. The simulated lava path can be used to define an optimize project to locate the work but for a timely action it is also necessary to quickly construct a barrier. Therefore this work investigates different type of engineering work that can be adopted to build up a lava containing barrier for improving the efficiency of the structure. From the analysis of historical cases it is clear that barriers were generally constructed by building up earth, lava blocks and incoherent, low density material. This solution implies complex operational constraints and logistical problems that justify the effort of looking for alternative design. Moreover for optimizing the barrier construction an alternative project of gabion-made barrier was here proposed. In this way the volume of mobilized material is lower than that for a earth barrier, thus reducing the time needed for build up the structure. A second crucial aspect to be considered is the geometry of the barrier which, is one of the few parameters that can be modulated, the others being linked to the morphological and topographical characteristics of the ground. Once the walls have been realized, it may be necessary to be able to expand the structure vertically. The use of gabion has many advantages over loose riprap (earthen walls) owing to their modularity and capability to be stacked in various shapes. Furthermore, the elements which are not inundated by lava can be removed and rapidly used for other barriers. The combination between numerical simulations and gabions will allow a quicker mitigation of risk on lava flows and this is an important aspect for a civil protection intervention in emergency cases.

  7. Shallowly driven fluctuations in lava lake outgassing (gas pistoning), Kīlauea Volcano

    Science.gov (United States)

    Patrick, Matthew R.; Orr, Tim; Sutton, A. J.; Lev, Einat; Thelen, Wes; Fee, David

    2016-01-01

    Lava lakes provide ideal venues for directly observing and understanding the nature of outgassing in basaltic magmatic systems. Kīlauea Volcano's summit lava lake has persisted for several years, during which seismic and infrasonic tremor amplitudes have exhibited episodic behavior associated with a rise and fall of the lava surface (;gas pistoning;). Since 2010, the outgassing regime of the lake has been tied to the presence or absence of gas pistoning. During normal behavior (no gas pistoning), the lake is in a ;spattering; regime, consisting of higher tremor amplitudes and gas emissions. In comparison, gas piston events are associated with an abrupt rise in lava level (up to 20 m), during which the lake enters a ;non-spattering; regime with greatly decreased tremor and gas emissions. We study this episodic behavior using long-term multidisciplinary monitoring of the lake, including seismicity, infrasound, gas emission and geochemistry, and time-lapse camera observations. The non-spattering regime (i.e. rise phase of a gas piston cycle) reflects gas bubbles accumulating near the top of the lake, perhaps as a shallow foam, while spattering regimes represent more efficient decoupling of gas from the lake. We speculate that the gas pistoning might be controlled by time-varying porosity and/or permeability in the upper portions of the lava lake, which may modulate foam formation and collapse. Competing models for gas pistoning, such as deeply sourced gas slugs, or dynamic pressure balances, are not consistent with our observations. Unlike other lava lakes which have cyclic behavior that is thought to be controlled by deeply sourced processes, external to the lake itself, we show an example of lava lake fluctuations driven by cycles of activity at shallow depth and close to the lake's surface. These observations highlight the complex and unsteady nature of outgassing from basaltic magmatic systems.

  8. Extensive soft sediment deformation and peperite formation at the base of a rhyolite lava: Owyhee Mountains, SW Idaho, USA

    OpenAIRE

    Mclean, Charlotte E.; Brown, David J.; Rawcliffe, Heather J.

    2016-01-01

    In the Northern Owyhee Mountains (SW Idaho), a >200 m thick flow of the Miocene Jump Creek Rhyolite was erupted on to a sequence of tuffs, lapilli-tuffs, breccias and lacustrine siltstones of the Sucker Creek Formation. The rhyolite lava flowed over steep palaeotopography, resulting in the forceful emplacement of lava into poorly consolidated sediments. The lava invaded this sequence, liquefying and mobilizing the sediment, propagating sediment sub-vertically in large metre-scale fluidal diap...

  9. Shatter Complex Formation in the Twin Craters Lava Flow, Zuni-Bandera Field, New Mexico

    Science.gov (United States)

    von Meerscheidt, H. C.; Bleacher, J. E.; Brand, B. D.; deWet, A.; Samuels, R.; Hamilton, C.; Garry, W. B.; Bandfield, J. L.

    2013-12-01

    Lava channels, tubes and sheets are transport structures that deliver flowing lava to a flow front. The type of structure can vary within a flow field and evolve throughout an eruption. The 18.0 × 1.0 ka Twin Craters lava flow in the Zuni-Bandera lava field provides a unique opportunity to study morphological changes of a lava flow partly attributable to interaction with a topographic obstacle. Facies mapping and airborne image analysis were performed on an area of the Twin Craters flow that includes a network of channels, lava tubes, shatter features, and disrupted pahoehoe flows surrounding a 45 m tall limestone bluff. The bluff is 1000 m long (oriented perpendicular to flow.) The general flow characteristics upstream from the bluff include smooth, lobate pahoehoe flows and a >2.5 km long lava tube (see Samuels et al., this meeting.) Emplacement characteristics change abruptly where the flow encountered the bluff, to include many localized areas of disrupted pahoehoe and several pahoehoe-floored depressions. Each depression is fully or partly surrounded by a raised rim of blocky material up to 4 m higher than the surrounding terrain. The rim is composed of 0.05 - 4 m diameter blocks, some of which form a breccia that is welded by lava, and some of which exhibit original flow textures. The rim-depression features are interpreted as shatter rings based on morphological similarity to those described by Orr (2011.Bul Volcanol.73.335-346) in Hawai';i. Orr suggests that shatter rings develop when fluctuations in the lava supply rate over-pressurize the tube, causing the tube roof to repeatedly uplift and subside. A rim of shattered blocks and breccias remains surrounding the sunken tube roof after the final lava withdraws from the system. One of these depressions in the Twin Craters flow is 240 m wide and includes six mounds of shattered material equal in height to the surrounding undisturbed terrain. Several mounds have depressed centers floored with rubbly pahoehoe

  10. Neogene Patagonian plateau lavas: Continental magmas associated with ridge collision at the Chile Triple Junction

    Science.gov (United States)

    Gorring, Matthew L.; Kay, Suzanne M.; Zeitler, Peter K.; Ramos, Victor A.; Rubiolo, Daniel; Fernandez, Marisa I.; Panza, Jose L.

    1997-02-01

    Extensive Neogene Patagonian plateau lavas (46.5° to 49.5°S) southeast of the modern Chile Triple Junction can be related to opening of asthenospheric "slab windows" associated with collisions of Chile Rise segments with the Chile Trench at ≈ 12 Ma and 6 Ma. Support comes from 26 new total-fusion, whole rock 40Ar/39Ar ages and geochemical data from back arc plateau lavas. In most localities, plateau lava sequences consist of voluminous, tholeiitic main-plateau flows overlain by less voluminous, 2 to 5 million year younger, alkalic postplateau flows. Northeast of where the ridge collided at ≈12 Ma, most lavas are syncollisional or postcollisional in age, with eruptions of both sequences migrating northeastward at 50 to 70 km/Ma. Plateau lavas have ages from 12 to 7 Ma in the western back arc and from 5 to 2 Ma farther to the northeast. Trace element and isotopic data indicate main-plateau lavas formed as larger percentage melts of a garnet-bearing, oceanic island basalt (OIB) -like mantle than postplateau lavas. The highest percentage melts erupted in the western and central plateaus. In a migrating slab window model, main-plateau lavas can be explained as melts that formed as upwelling, subslab asthenosphere which flowed around the trailing edge of the descending Nazca Plate and then interacted with subduction-altered asthenospheric wedge and continental lithosphere. Alkaline, postplateau lavas can be explained as melts generated by weaker upwelling of subslab asthenosphere through the open slab window. Thermal problems of high-pressure melt generation of anhydrous mantle can be explained by volatiles (H2O and CO2) introduced by the subduction process into slab window source region(s). An OIB-like, rather than a mid-ocean ridge basalt (MORB) -like source region, and the lack of magmatism northeast of where ridge collision occurred at ≈13 to 14 Ma can be explained by entrainment of "weak" plume(s) or regional variations in an ambient, OIB-like asthenosphere.

  11. Stratigraphical framework of basaltic lavas in Torres Syncline main valley, southern Parana-Etendeka Volcanic Province

    Science.gov (United States)

    Rossetti, Lucas M.; Lima, Evandro F.; Waichel, Breno L.; Scherer, Claiton M.; Barreto, Carla J.

    2014-12-01

    The Paraná-Etendeka Volcanic Province records the volcanism of the Early Cretaceous that precedes the fragmentation of the South-Gondwana supercontinent. Traditionally, investigations of these rocks prioritized the acquisition of geochemical and isotopic data, considering the volcanic stack as a monotonous succession of tabular flows. Torres Syncline is a tectonic structure located in southern Brazil and where the Parana-Etendeka basalts are well preserved. This work provides a detailed analysis of lithofacies and facies architecture, integrated to petrographic and geochemical data. We identified seven distinct lithofacies grouped into four facies associations related to different flow morphologies. The basaltic lava flows in the area can be divided into two contrasting units: Unit I - pahoehoe flow fields; and Unit II - simple rubbly flows. The first unit is build up by innumerous pahoehoe lava flows that cover the sandstones of Botucatu Formation. These flows occur as sheet pahoehoe, compound pahoehoe, and ponded lavas morphologies. Compound lavas are olivine-phyric basalts with intergranular pyroxenes. In ponded lavas and cores of sheet flows coarse plagioclase-phyric basalts are common. The first pahoehoe lavas are more primitive with higher contents of MgO. The emplacement of compound pahoehoe flows is related to low volume eruptions, while sheet lavas were emplaced during sustained eruptions. In contrast, Unit II is formed by thick simple rubbly lavas, characterized by a massive core and a brecciated/rubbly top. Petrographically these flows are characterized by plagioclase-phyric to aphyric basalts with high density of plagioclase crystals in the matrix. Chemically they are more differentiated lavas, and the emplacement is related to sustained high effusion rate eruptions. Both units are low TiO2 and have geochemical characteristics of Gramado magma type. The Torres Syncline main valley has a similar evolution when compared to other Large Igneous Provinces

  12. Lava flow modelling in long and short-term hazard assessment

    Science.gov (United States)

    Martí, Joan; Becerril, Laura; Bartolini, Stefania

    2017-04-01

    Lava flows constitute the commonest volcano hazard resulting from a non-explosive eruption, especially in basaltic systems. These flows come in many shapes and sizes and have a wide range of surface morphology (pahoehoe, aa, blocky, etc.) whose differences are mainly controlled by variations in magma viscosity and supply rates at the time of the eruption. The principal constraint on lava emplacement is topography and so flows will tend to invade the lowest-lying areas. Modelling such complex non-Newtonian flows is not an easy task, as many of the parameters required to precisely define flow behaviour are not known. This is one of the reasons, in addition to the required high computing cost, for which deterministic models are not preferred when conducting long and short term hazard assessment. On the contrary, probabilistic models, despite being much less precise, offer a rapid approach to lava flow invasion and fulfil the main needs required in lava flow hazard analysis, with a much less computational demand and, consequently, offering a much wider applicability. In this contribution we analyse the main problems that exist in lava flow modelling, compare between deterministic and probabilistic models, and show the application of probabilistic models in long and short-term hazard assessment. This contribution is part of the EC ECHO SI2.695524:VeTOOLS and EPOS-IP AMD-676564-42 Grants

  13. A three-dimensional dynamical model for channeled lava flow with nonlinear rheology

    Science.gov (United States)

    Filippucci, Marilena; Tallarico, Andrea; Dragoni, Michele

    2010-05-01

    Recent laboratory studies on the rheology of lava samples from different volcanic areas have highlighted that the apparent viscosity depends on a power of the strain rate. Several authors agree in attributing this dependence to the crystal content of the sample and to temperature. Starting from these results, in this paper we studied the effect of a power law rheology on a gravity-driven lava flow. The equation of motion is nonlinear in the diffusion term, and an analytical solution does not seem to be possible. The finite-volume method has been applied to solve numerically the equation governing the fully developed laminar flow of a power law non-Newtonian fluid in an inclined rectangular channel. The convergence, the stability, and the order of approximation were tested for the Newtonian rheology case, comparing the numerical solution with the available analytical solution. Results indicate that the assumption on the rheology, whether linear or nonlinear, strongly affects the velocity and/or the thickness of the lava channel both for channels with fixed geometry and for channels with constant flow rate. Results on channels with fixed geometry are confirmed by some simulations for real lava channels. Finally, the study of the Reynolds number indicates that gravity-driven lava channel flows are always in laminar regime, except for strongly nonlinear pseudoplastic fluids with low fluid consistency and at high slopes.

  14. Geochemical characteristics of West Molokai shield- and postshield-stage lavas: Constraints on Hawaiian plume models

    Science.gov (United States)

    Xu, Guangping; Frey, Frederick A.; Clague, David A.; Abouchami, Wafa; Blichert-Toft, Janne; Cousens, Brian; Weisler, Marshall

    2007-08-01

    There are systematic geochemical differences between the Hawaiian shields forming the subparallel spatial trends, known as Loa and Kea. These spatial and temporal geochemical changes provide insight into the spatial distribution of geochemical heterogeneities within the source of Hawaiian lavas, and the processes that create the Hawaiian plume. Lavas forming the ˜1.9 Ma West Molokai volcano are important for evaluating alternative models proposed for the spatial distribution of geochemical heterogeneities because (1) the geochemical distinction between Loa and Kea trends may end at the Molokai Fracture Zone and (2) West Molokai is a Loa-trend volcano that has exposures of shield and postshield lavas. This geochemical study (major and trace element abundances and isotopic ratios of Sr, Nd, Hf, and Pb) shows that the West Molokai shield includes lavas with Loa- and Kea-like geochemical characteristics; a mixed Loa-Kea source is required. In contrast, West Molokai postshield lavas are exclusively Kea-like. This change in source geochemistry can be explained by the observed change in strike of the Pacific plate near Molokai Island so that as West Molokai volcano moved away from a mixed Loa-Kea source it sampled only the Kea side of a bilaterally zoned plume.

  15. Characterization of Sheet Fracture Patterns in Polygonal-Jointed Lavas at Kokostick Butte, OR, and Mazama Ridge, WA: Investigation and Interpretation of Their Formation and Significance

    Science.gov (United States)

    Lodge, R. W.; Lescinsky, D. T.

    2006-12-01

    Polygonal joints in lava flows ("columns") are commonly equant leading to a model of formation associated with cooling in an isotropic stress field. This model, however, does not explain rectangular columns, sheet-like fractures, fractures with crosscutting relationships, and fractures with orientations other than perpendicular to the cooling surface. These fracture patterns are often observed at glaciated volcanoes. The presence of preferential fracture orientations suggests an applied stress component likely due to environmental conditions such as the presence of glaciers or flow dynamics such as down-slope settling or flow margin inflation. During this study we investigated the formation and significance of these non-equant fracture patterns to propose a model for their formation. These `abnormal' fracture patterns have not been discussed in the literature and may be important to better understanding the cooling conditions of such lava flows. To test these possibilities we studied Kokostick Butte dacite flow, OR (near South Sister), and Mazama Ridge andesite flow at Mount Rainier, WA. Both of these flows have well developed sheet-like fractures and display evidence of ice-contact during eruption and emplacement. Sheet fractures are long and continuous fractures that have perpendicular connecting fractures forming rectangular columns. The sheet-like fractures are largely parallel to each other on the exposure surface and the connecting fractures vary locally from primary fractures (associated with cooling toward flow interior) to secondary fractures (associated with cooling by water infiltration). Detailed measurements of fracture orientations and spacing were collected at Kokostick Butte and Mazama Ridge to examine the relationship between the sheet fractures and flow geometry. Preliminary results support this relationship and suggest these patterns likely form due to shear associated with small amounts of flow advance by the rapidly cooling lava. Laboratory

  16. Eruptive history of the Karoo lava flows and their impact on early Jurassic environmental change

    Science.gov (United States)

    Moulin, M.; Fluteau, F.; Courtillot, V.; Marsh, J.; Delpech, G.; Quidelleur, X.; Gérard, M.

    2017-02-01

    This paper reports new paleomagnetic and geochronologic data from a 1500 m thick composite section belonging to the Drakensberg group, the thickest remnant of the Karoo lavas in Northern Lesotho. Flow-by-flow analysis of paleomagnetic directions reveals 21 magnetic directional groups, corresponding to single eruptive events, and 16 individual lava flows. The new age determinations of lava flows range from 180.1 ± 1.4 to 182.8 ± 2.6 Ma. These data, combined with previous results, allow us to propose that the main part of the Drakensberg group and the Karoo intrusive complex dated around 181-183 Ma may have been erupted over a period as short as 250 kyr and may have coincided with the two main phases of extinction in the Early Toarcian. This scenario agrees well with the discontinuous rhythm of environmental and biotic perturbations in the Late Pliensbachian-Toarcian interval.

  17. Paleomagnetism of Eocene Talerua Member Lavas on Hareøen Island, West Greenland

    DEFF Research Database (Denmark)

    Abrahamsen, N.; Schmidt, Anne G.; Riisager, P.

    2005-01-01

    in the West Greenland flood volcanic province. Rock magnetic experiments and microprobe analysis show that the dominant magnetic mineral in all studied lavas is titanomagnetite that has experienced variable amounts of high temperature deuteric oxidation as well as low temperature hydro-thermal oxidation....... Based on detailed demagnetisation experiments, well-defined paleomagnetic site-mean directions were isolated from all 19 lavas. The composite profile contains two magnetic polarity zones suggesting a maximum duration of Talerua Member volcanism of ~1.4 Myr. After grouping flows indicating the same......The results of a palaeomagnetic sampling carried out along two vertical profiles (altogether 19 lavaflows, 126 samples) covering the entire stratigraphy of the Talerua Member lavas (~39 Myr old) that outcrop on the island Hareøen are presented and represent some of the youngest volcanism...

  18. Comparison of SAM and OBIA as Tools for Lava Morphology Classification - A Case Study in Krafla, NE Iceland

    Science.gov (United States)

    Aufaristama, Muhammad; Hölbling, Daniel; Höskuldsson, Ármann; Jónsdóttir, Ingibjörg

    2017-04-01

    The Krafla volcanic system is part of the Icelandic North Volcanic Zone (NVZ). During Holocene, two eruptive events occurred in Krafla, 1724-1729 and 1975-1984. The last eruptive episode (1975-1984), known as the "Krafla Fires", resulted in nine volcanic eruption episodes. The total area covered by the lavas from this eruptive episode is 36 km2 and the volume is about 0.25-0.3 km3. Lava morphology is related to the characteristics of the surface morphology of a lava flow after solidification. The typical morphology of lava can be used as primary basis for the classification of lava flows when rheological properties cannot be directly observed during emplacement, and also for better understanding the behavior of lava flow models. Although mapping of lava flows in the field is relatively accurate such traditional methods are time consuming, especially when the lava covers large areas such as it is the case in Krafla. Semi-automatic mapping methods that make use of satellite remote sensing data allow for an efficient and fast mapping of lava morphology. In this study, two semi-automatic methods for lava morphology classification are presented and compared using Landsat 8 (30 m spatial resolution) and SPOT-5 (10 m spatial resolution) satellite images. For assessing the classification accuracy, the results from semi-automatic mapping were compared to the respective results from visual interpretation. On the one hand, the Spectral Angle Mapper (SAM) classification method was used. With this method an image is classified according to the spectral similarity between the image reflectance spectrums and the reference reflectance spectra. SAM successfully produced detailed lava surface morphology maps. However, the pixel-based approach partly leads to a salt-and-pepper effect. On the other hand, we applied the Random Forest (RF) classification method within an object-based image analysis (OBIA) framework. This statistical classifier uses a randomly selected subset of training

  19. Lava Flow Interactions with Topographic Obstacles: Morphologic Analysis, Analogue Modeling, and Molten Basalt Experiments

    Science.gov (United States)

    Dietterich, H. R.; Cashman, K. V.; Rust, A.; Lev, E.; Dietrich, J. T.

    2014-12-01

    Underlying topography controls lava flow emplacement by influencing flow paths, lengths, and advance rates. The morphology of the pre-eruptive surface provides input into lava flow models and the design of artificial diversion barriers, although the dynamics of interactions between topographic obstacles and lava flows are not well known. We investigate these factors by combining morphologic analysis of Hawaiian lava flows with scaling derived from analogue and molten basalt experiments. A comparison of pre- and post-eruptive topographic data shows that flows thicken on the upslope side of topographic barriers, a feature that has been employed to calculate flow velocities from simple energy conversion. Observations also document effects of flow branching and confinement on flow advance rate, with confined flows in Hawai'i traveling further and faster than those that branch. To explain these observations we perform laboratory experiments using Newtonian and Bingham analogue fluids, as well as molten basalt. Conditions of flow splitting and subsequent advance are defined using experiments with both V-shaped and cylindrical obstacles that divide an unconfined flow. Oblique linear obstacles are used to explore flow confinement and diversion. We find that the degree of thickening, which determines the height of an obstacle capable of holding back the flow, is controlled by both initial flow velocity and obstacle geometry. Key is the ability of the flow to pass around the obstacle, such that larger and wider obstacles cause greater thickening than smaller and narrower obstacles. Flow advance rate is largely unaffected by branching in the Newtonian analogue experiments, but decreases after splitting in the molten basalt experiments because of surface cooling. Interestingly, flows into oblique obstacles are diverted but travel faster. Together these data provide the basis for a theoretical description of the interaction dynamics of viscous (and cooling) lava flows with

  20. LAVA (Los Alamos Vulnerability and Risk Assessment Methodology): A conceptual framework for automated risk analysis

    Energy Technology Data Exchange (ETDEWEB)

    Smith, S.T.; Lim, J.J.; Phillips, J.R.; Tisinger, R.M.; Brown, D.C.; FitzGerald, P.D.

    1986-01-01

    At Los Alamos National Laboratory, we have developed an original methodology for performing risk analyses on subject systems characterized by a general set of asset categories, a general spectrum of threats, a definable system-specific set of safeguards protecting the assets from the threats, and a general set of outcomes resulting from threats exploiting weaknesses in the safeguards system. The Los Alamos Vulnerability and Risk Assessment Methodology (LAVA) models complex systems having large amounts of ''soft'' information about both the system itself and occurrences related to the system. Its structure lends itself well to automation on a portable computer, making it possible to analyze numerous similar but geographically separated installations consistently and in as much depth as the subject system warrants. LAVA is based on hierarchical systems theory, event trees, fuzzy sets, natural-language processing, decision theory, and utility theory. LAVA's framework is a hierarchical set of fuzzy event trees that relate the results of several embedded (or sub-) analyses: a vulnerability assessment providing information about the presence and efficacy of system safeguards, a threat analysis providing information about static (background) and dynamic (changing) threat components coupled with an analysis of asset ''attractiveness'' to the dynamic threat, and a consequence analysis providing information about the outcome spectrum's severity measures and impact values. By using LAVA, we have modeled our widely used computer security application as well as LAVA/CS systems for physical protection, transborder data flow, contract awards, and property management. It is presently being applied for modeling risk management in embedded systems, survivability systems, and weapons systems security. LAVA is especially effective in modeling subject systems that include a large human component.

  1. Open-path FTIR spectroscopy of magma degassing processes during eight lava fountains on Mount Etna

    Science.gov (United States)

    La Spina, Alessandro; Burton, Mike; Allard, Patrick; Alparone, Salvatore; Murè, Filippo

    2016-04-01

    In June-July 2001 a series of 16 discrete lava fountain paroxysms occurred at the Southeast summit crater (SEC) of Mount Etna, preceding a 28-day long violent flank eruption. Each paroxysm was preceded by lava effusion, growing seismic tremor and a crescendo of Strombolian explosive activity culminating into powerful lava fountaining up to 500m in height. During 8 of these 16 events we could measure the chemical composition of the magmatic gas phase (H2O, CO2, SO2, HCl, HF and CO), using open-path Fourier transform infrared (OP-FTIR) spectrometry at ˜1-2km distance from SEC and absorption spectra of the radiation emitted by hot lava fragments. We show that each fountaining episode was characterized by increasingly CO2-rich gas release, with CO2/SO2and CO2/HCl ratios peaking in coincidence with maxima in seismic tremor and fountain height, whilst the SO2/HCl ratio showed a weak inverse relationship with respect to eruption intensity. Moreover, peak values in both CO2/SO2ratio and seismic tremor amplitude for each paroxysm were found to increase linearly in proportion with the repose interval (2-6 days) between lava fountains. These observations, together with a model of volatile degassing at Etna, support the following driving process. Prior to and during the June-July 2001 lava fountain sequence, the shallow (˜2km) magma reservoir feeding SEC received an increasing influx of deeply derived carbon dioxide, likely promoted by the deep ascent of volatile-rich primitive basalt that produced the subsequent flank eruption. This CO2-rich gas supply led to gas accumulation and overpressure in SEC reservoir, generating a bubble foam layer whose periodical collapse powered the successive fountaining events. The anti-correlation between SO2/HCl and eruption intensity is best explained by enhanced syn-eruptive degassing of chlorine from finer particles produced during more intense magma fragmentation.

  2. Channelled flow of lava with temperature dependent pseudoplastic rheology: condition for tube formation

    Science.gov (United States)

    Filippucci, Marilena; Tallarico, Andrea; Dragoni, Michele

    2010-05-01

    Conditions for crust and tube formation are studied assuming for lava a pseudoplastic rheology dependent on temperature (Sonder, pers. Comm.). The pseudoplasticity is the rheological model which, from recent laboratory studies, better describes the behaviour of basaltic lava (e.g. Sonder et al., 2006). The pseudoplastic rheology belongs to the power law rheology and the constitutive equation for a power law fluid is the following: σij = 2kdot en-1dot eij (1) where k is the fluid consistency, n is the power law exponent and e depends on the second invariant of the deformation rate tensor. For a pseudoplastic fluid we have that n

  3. Kīlauea summit eruption—Lava returns to Halemaʻumaʻu

    Science.gov (United States)

    Babb, Janet L.; Wessells, Stephen M.; Neal, Christina A.

    2017-10-06

    In March 2008, a new volcanic vent opened within Halemaʻumaʻu, a crater at the summit of Kīlauea Volcano in Hawaiʻi Volcanoes National Park on the Island of Hawaiʻi. This new vent is one of two ongoing eruptions on the volcano. The other is on Kīlauea’s East Rift Zone, where vents have been erupting nearly nonstop since 1983. The duration of these simultaneous summit and rift zone eruptions on Kīlauea is unmatched in at least 200 years.Since 2008, Kīlauea’s summit eruption has consisted of continuous degassing, occasional explosive events, and an active, circulating lava lake. Because of ongoing volcanic hazards associated with the summit vent, including the emission of high levels of sulfur dioxide gas and fragments of hot lava and rock explosively hurled onto the crater rim, the area around Halemaʻumaʻu remains closed to the public as of 2017.Through historical photos of past Halemaʻumaʻu eruptions and stunning 4K imagery of the current eruption, this 24-minute program tells the story of Kīlauea Volcano’s summit lava lake—now one of the two largest lava lakes in the world. It begins with a Hawaiian chant that expresses traditional observations of a bubbling lava lake and reflects the connections between science and culture that continue on Kīlauea today.The video briefly recounts the eruptive history of Halemaʻumaʻu and describes the formation and continued growth of the current summit vent and lava lake. It features USGS Hawaiian Volcano Observatory scientists sharing their insights on the summit eruption—how they monitor the lava lake, how and why the lake level rises and falls, why explosive events occur, the connection between Kīlauea’s ongoing summit and East Rift Zone eruptions, and the impacts of the summit eruption on the Island of Hawaiʻi and beyond. The video is also available at the following U.S. Geological Survey Multimedia Gallery link (video hosted on YouTube): Kīlauea summit eruption—Lava returns to Halemaʻumaʻu

  4. Studies of Young Hawai'ian Lava Tubes: Implications for Planetary Habitability and Human Exploration

    Science.gov (United States)

    McAdam, Amy; Bleacher, Jacob; Young, Kelsey; Johnson, Sarah Stewart; Needham, Debra; Schmerr, Nicholas; Shiro, Brian; Garry, Brent; Whelley, Patrick; Knudson, Christine; hide

    2017-01-01

    Habitability: Subsurface environments may preserve records of habitability or biosignatures, with more stable environmental conditions compared to surface (e.g., smaller variations in temperature and humidity) and reduced exposure to radiation; Lava tubes are expected on Mars, and candidates are observed from orbit; Few detailed studies of microbial populations in terrestrial lava caves; Also contain a variety of secondary minerals; Microbial activity may play a role in mineral formation or be preserved in these minerals; Minerals can provide insight into fluids (e.g., pH, temperature).

  5. Examining rhyolite lava flow dynamics through photo-based 3-D reconstructions of the 2011-2012 lava flow field at Cordón Caulle, Chile.

    Science.gov (United States)

    James, M. R.; Farquharson, J.; Tuffen, H.

    2014-12-01

    The 2011-2012 eruption at Cordón-Caulle, Chile, afforded the opportunity to observe and measure active rhyolitic lava for the first time. In 2012 and 2013, ~2500 photos were acquired on foot, parallel to flow fronts on the north and north-east of the flow field. Image suites were then processed into 3-D point clouds using Structure-from-Motion Multi-view Stereo (SfM-MVS) freeware. Interpolating these clouds into digital elevation models for dates in 2012-13 enabled analysis of the changing flow field dimensions [1], from which velocity, depth and rheological parameters, e.g.viscosity, could be estimated [see Fig. 1]. Viscosities ranged from 7.5 x109 to 1.1 x1011Pa s, allowing for uncertainties in slope, surface displacement and velocity. Temperatures were modeled using a 1D finite difference method; in concert with viscosities of flow units these values compared well with published non-Arrhenian viscosity models. Derived thermodynamic and force ratios confirmed flow characteristics inferred from the image analyses. SfM-MVS represents an effective method of quantifying and displaying variation in the flow field, indicating several parallels between rhyolite emplacement and that of low-silica lavas. Initially channelised lava spread laterally and stagnated due to topography and the influence of the surface crust. Continued effusion resulted in iterative emplacement of breakout lobes, promoting lateral extension of the flow field. Insulation of the flow core by the viscous crust allowed this process to continue after effusion had ceased, creating features comparable to low-silica lavas, despite high viscosity and low effusion rates. This suggests that compound flow emplacement may be described by universal, cross-compositional models encompassing rheological differences of many orders of magnitude. Tuffen et al. 2013, Nat. Comms., 4, 2709, doi:10.1038/ncomms3709

  6. Oxygen isotope homogeneity and trace element variations in glass within 250-79 ka Central Plateau Member rhyolite lavas from the Yellowstone Volcanic System

    Science.gov (United States)

    Loewen, M.; Bindeman, I. N.; Befus, K. S.

    2014-12-01

    The 250-79 ka Central Plateau Member CPM) rhyolites are represented mostly by large volume lava flows with less than 10% crystals and are the youngest eruptive products inside of the 620 ka Yellowstone Caldera, formed after eruption of Lava Creek Tuff (LCT). These flows are low-δ18O requiring tens of percent of shallowly remelted hydrothermally-altered material and provide evidence into how large silicic magma systems evolve before and after major caldera-forming cycles. We have developed a technique to directly analyze small micro-domains of rhyolite glass for precise (better than 0.1 ‰) δ18O determination coupled with D/H, [H2O], trace elements, and Pb isotopes. We present evidence for striking δ18O homogeneity (4.48 ± 0.12 ‰, 2 standard deviations of all analyses) both across small (1 km3) and large (up to 70 km3) flows and between flows erupted over almost 200 ka. D/H analyses in the glasses are highly degassed and are not affected by secondary hydration (H2O = 0.05 to 0.28 wt. %, δD = -99 to -171 ‰). Trace element analyses show broad temporal compositional evolution consistent with increasing feldspar fractionation over time: the oldest Scaup Lake flow contains 8 ppm Sr, 330 ppm Rb, and 270 ppm Ba to the youngest Pitchstone Plateau flow contains 0.7-1.9 ppm Sr, 180-250 ppm Rb, 18-25 ppm Ba. We also show small but recognizable trace element heterogeneity within lava flows unrelated to long-term geochemical trends. Homogeneity of oxygen in melt from individual lava flows across the LCT caldera is consistent with convective homogenization of a large magma body generated by remelting of post and pre LCT hydrothermally-altered and likely highly variable, low- δ18O rocks. In combination with trace element data we show that the CPM rhyolites have also undergone a broad, caldera-wide differentiation trend with no evidence for significant recharge. We are reconciling diverse geochemical data streams to develop a comprehensive petrologic model for the

  7. Nerillidae (Annelida) from the Corona lava tube, Lanzarote, with description of Meganerilla cesari, n. sp

    DEFF Research Database (Denmark)

    Worsaae, Katrine; Martínez, A; Núñez, J

    2009-01-01

    reported. Updated diagnoses are presented for Mesonerilla armoricana, reported here for the first time from the Canary Islands, and Leptonerilla diatomeophaga, the only nerillid previously known from the Corona lava tube. The Corona lava tube holds a large variety of benthic habitats, which may explain...

  8. The maximum size of inflated flood lavas: implications for the origin and evolution of Athabasca Valles, Mars

    Science.gov (United States)

    Sori, M. M.; Hamilton, C. W.

    2017-09-01

    We constrain the maximum size that an inflating, cooling-limited basalt flow can obtain using numerical models. We find that the Athabasca Valles flood lava on Mars is too large to represent a single, pāhoehoe-like inflated flow. Our work can be used to characterize putative lava flows throughout the solar system's terrestrial bodies.

  9. The control of lava flow during the 1991 1992 eruption of Mt. Etna

    Science.gov (United States)

    Barberi, F.; Carapezza, M. L.; Valenza, M.; Villari, L.

    1993-05-01

    All the actions carried out in 1992 to protect the village of Zafferana Etnea from being invaded by lava are described. An earthen barrier 234 m long and 21 m high was firstly built in January 1992 by accumulating with mechanical escavators 370,000 m 3 of earth, scoriae and stones. This embankment contained the lava for about one month and was overflowed by April 9, 1992. Three additional smaller earthen barriers (lenght: 90-160 m; height: 6-12 m) were built in April to gain time while the lava front was descending towards Zafferana from the overflowed first embankment. The major effort of the 1992 operation consisted of several attempts at stopping the lava front advance by diverting the flow out from the natural and extensively tunnelled channel through a skylight near the vent. The main intervention point was located in Valle del Bove at an elevation of 2000 m, at 8 km from Zafferana, in a zone almost unaccessible from land: helicopters were hence extensively used during the whole operation. Initial interventions called for attempts at plugging a tunnel by dumping into it linked concrete blocks, hedgehogs and blasted portions of the solid levee. Each intervention caused the partial obstruction of the tunnelled channel, which determined major increases of lava overflow in Valle del Bove and the consequent halt of the most advanced fronts. However, benefits were of brief duration, at the most two weeks of respite, before new lava fronts approached again and again the outskirts of Zafferana. The final successful intervention was carried out on May 27-29. An artificial channel was dug departing from the natural one. The solid separation levee was thinned to 3 m and blasted by 7000 kg of explosives. After the explosion, {2}/{3} of the lava flowed spontaneously in the artificial channel and then the total diversion was obtained, the tunnel being plugged by dumping into the natural flow 230 m 3 of lava boulders. As a consequence of the intervention the active natural

  10. Crustal thickness and composition beneath the High Lava Plains of Eastern Oregon from teleseismic receiver functions

    Science.gov (United States)

    Eagar, K. C.; Fouch, M. J.; James, D. E.; Carlson, R. W.

    2009-12-01

    The nature of the crust beneath the High Lava Plains of eastern Oregon is fundamental for understanding the origins of widespread Cenozoic volcanism in the region. Eruptions of flood basalts in the southern Cascadian back arc peaked ~17-15 Ma, and were followed by distributed bimodal volcanism along two perpendicular migrating tracks; the Snake River Plain and the High Lava Plains. The orientations of eruptive centers have led to several competing hypotheses about their cause, including a deep mantle plume, slab retreat and asthenospheric inflow, lithospheric delamination, and lithospheric extension. The goal of this project is to constrain the nature, geometry, and depth of the Moho across the High Lava Plains, which will shed light on questions regarding crustal influence on melt generation and differentiation and the degree of magmatic underplating. In this study, we analyze teleseismic receiver functions from 118 stations of the High Lava Plains temporary broadband array, 34 nearby EarthScope/USArray stations, and 5 other regional broadband stations to determine bulk crustal features of thickness (H) and Vp/Vs ratio (κ). Applying the H-κ stacking method, we search for the best-fitting solution of timing predictions for direct and multiple P-to-S conversions from the Moho interface. Converting Vp/Vs to Poisson ratio, which is dependent primarily upon rock composition, allows for comparison with other direct geological observations. Preliminary results show that the crust of the High Lava Plains is relatively thin (~31 km) with a very sharp gradient to thicker crust (~42 km) at the western edge of the Owyhee Plateau in southwestern Idaho. This gradient is co-located with the western margin of Precambrian North America and is in the vicinity of the Jordan Craters volcanic center. The sharp topography of the Moho might have been a factor in melt migration beneath this area. West of the High Lava Plains, the crust thickens to ~40 km into the Cascade volcanic arc

  11. Bulk rock composition and geochemistry of olivine-hosted melt inclusions in the Grey Porri Tuff and selected lavas of the Monte dei Porri volcano, Salina, Aeolian Islands, southern Italy

    Science.gov (United States)

    Doherty, Angela; Bodnar, Robert; Vivo, Benedetto; Bohrson, Wendy; Belkin, Harvey; Messina, Antonia; Tracy, Robert

    2012-06-01

    The Aeolian Islands are an arcuate chain of submarine seamounts and volcanic islands, lying just north of Sicily in southern Italy. The second largest of the islands, Salina, exhibits a wide range of compositional variation in its erupted products, from basaltic lavas to rhyolitic pumice. The Monte dei Porri eruptions occurred between 60 ka and 30 ka, following a period of approximately 60,000 years of repose. The bulk rock composition of the Monte dei Porri products range from basaltic-andesite scoria to andesitic pumice in the Grey Porri Tuff (GPT), with the Monte dei Porri lavas having basaltic-andesite compositions. The typical mineral assemblage of the GPT is calcic plagioclase, clinopyroxene (augite), olivine (Fo72-84) and orthopyroxene (enstatite) ± amphibole and Ti-Fe oxides. The lava units show a similar mineral assemblage, but contain lower Fo olivines (Fo57-78). The lava units also contain numerous glomerocrysts, including an unusual variety that contains quartz, K-feldspar and mica. Melt inclusions (MI) are ubiquitous in all mineral phases from all units of the Monte dei Porri eruptions; however, only data from olivine-hosted MI in the GPT are reported here. Compositions of MI in the GPT are typically basaltic (average SiO2 of 49.8 wt %) in the pumices and basaltic-andesite (average SiO2 of 55.6 wt %) in the scoriae and show a bimodal distribution in most compositional discrimination plots. The compositions of most of the MI in the scoriae overlap with bulk rock compositions of the lavas. Petrological and geochemical evidence suggest that mixing of one or more magmas and/or crustal assimilation played a role in the evolution of the Monte dei Porri magmatic system, especially the GPT. Analyses of the more evolved mineral phases are required to better constrain the evolution of the magma.

  12. Bulk rock composition and geochemistry of olivine-hosted melt inclusions in the Grey Porri Tuff and selected lavas of the Monte dei Porri volcano, Salina, Aeolian Islands, southern Italy

    Science.gov (United States)

    Doherty, Angela L.; Bodnar, Robert J.; De Vivo, Benedetto; Bohrson, Wendy A.; Belkin, Harvey E.; Messina, Antonia; Tracy, Robert J.

    2012-01-01

    The Aeolian Islands are an arcuate chain of submarine seamounts and volcanic islands, lying just north of Sicily in southern Italy. The second largest of the islands, Salina, exhibits a wide range of compositional variation in its erupted products, from basaltic lavas to rhyolitic pumice. The Monte dei Porri eruptions occurred between 60 ka and 30 ka, following a period of approximately 60,000 years of repose. The bulk rock composition of the Monte dei Porri products range from basaltic-andesite scoria to andesitic pumice in the Grey Porri Tuff (GPT), with the Monte dei Porri lavas having basaltic-andesite compositions. The typical mineral assemblage of the GPT is calcic plagioclase, clinopyroxene (augite), olivine (Fo72−84) and orthopyroxene (enstatite) ± amphibole and Ti-Fe oxides. The lava units show a similar mineral assemblage, but contain lower Fo olivines (Fo57−78). The lava units also contain numerous glomerocrysts, including an unusual variety that contains quartz, K-feldspar and mica. Melt inclusions (MI) are ubiquitous in all mineral phases from all units of the Monte dei Porri eruptions; however, only data from olivine-hosted MI in the GPT are reported here. Compositions of MI in the GPT are typically basaltic (average SiO2 of 49.8 wt %) in the pumices and basaltic-andesite (average SiO2 of 55.6 wt %) in the scoriae and show a bimodal distribution in most compositional discrimination plots. The compositions of most of the MI in the scoriae overlap with bulk rock compositions of the lavas. Petrological and geochemical evidence suggest that mixing of one or more magmas and/or crustal assimilation played a role in the evolution of the Monte dei Porri magmatic system, especially the GPT. Analyses of the more evolved mineral phases are required to better constrain the evolution of the magma.

  13. A combined study of gas geochemistry, petrology, and lava effusion at Bagana, a unique persistently active lava cone in Papua New Guinea

    Science.gov (United States)

    McCormick, B. T.; Salem, L. C.; Edmonds, M.; D'Aleo, R. N. M.; Aiuppa, A.; Arellano, S. R.; Wallius, J.; Galle, B.; Barry, P. H.; Ballentine, C. J.; Mulina, K.; Sindang, M.; Itikarai, I.; Wadge, G.; Lopez, T. M.; Fischer, T. P.

    2016-12-01

    Bagana volcano (Bougainville Island, Papua New Guinea) has exhibited nearly continuous extrusion of andesitic lava for over a century, but has largely been studied by satellite remote sensing. Satellite UV spectroscopy has revealed Bagana to be among the largest volcanic sources of sulfur dioxide worldwide. Satellite radar measurements of lava extrusion rate suggest that the entire edifice could have been built in only a few centuries. Bagana is dominantly constructed from lava flows, but also exhibits violent PDC-forming explosive eruptions, which threaten local populations.We present new multi-parameter data from fieldwork on Bagana in September 2016. UV spectrometers were deployed to ground-truth satellite observations of SO2 emissions, and track sub-daily variations in gas output. In situ measurements and sampling of emissions provide the first gas composition data for this volcano. Aerial imagery filmed by UAV was obtained to generate a high resolution DEM of the edifice for use in calibrating ongoing satellite radar studies of deformation and extrusion rate. Lava and tephra samples were gathered, with the aim of comparing melt composition and volatile content between eruptions of different style. The combination of gas geochemistry, geophysical monitoring from space, and petrology will be used to build a model framework to understand the pulsatory nature of Bagana's lava extrusion, and transitions to explosive activity.A campaign to a continuously active but poorly-studied volcano affords many opportunities for education and outreach. The campaign participants included early career scientists from five countries, who planned and carried out the fieldwork and exchanged expertise in a range of techniques. All work was undertaken in close collaboration with Rabaul Volcano Observatory, and was informed by their strategic monitoring goals, a valuable experience for the field team of synergising research activities with more operational concerns. Footage obtained

  14. Modelling long-term (300ka) upland catchment response to multiple lava damming events

    NARCIS (Netherlands)

    van Gorp, W.; Temme, A. J. A. M.; Veldkamp, A.; Schoorl, J. M.

    2015-01-01

    Landscapes respond in complex ways to external drivers such as base level change due to damming events. In this study, landscape evolution modelling was used to understand and analyse long-term catchment response to lava damming events. PalaeoDEM reconstruction of a small Turkish catchment (45km(2))

  15. A brief comparison of lava flows from the Deccan Volcanic Province ...

    Indian Academy of Sciences (India)

    However, even a cursory review of published literature reveals that the Columbia River Basalt Group (CRBG) and Hawaiian volcanoes provide most of the data relevant to this topic. It is interesting to note, however, that the CRBG lava flows and their palaeotopographic control is atypical of other CFB provinces in the world.

  16. Silica-poor, mafic alkaline lavas from ocean islands and continents ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    Strongly silica-poor (ne-normative), mafic alkaline lavas generally represented by olivine nephelin- ites, nephelinites, melilitites, and olivine melilitites have erupted at various locations during Earth's history. On the basis of bulk-rock Mg#, high concentrations of Na2O, TiO2, and K2O, and trace element geochemistry, it has ...

  17. A rock- and paleomagnetic study of a Holocene lava flow in Central Mexico

    NARCIS (Netherlands)

    Vlag, P.; Alva-Valdivia, L.; Boer, C.B. de; Gonzalez, S.; Urrutia-Fucugauchi, J.

    1999-01-01

    Magnetic measurements of the Tres Cruces lava flow (ca. 8500 years BP, Central Mexico) show the presence of two remanence carriers, a Ti-rich titanomagnetite with a Curie temperature between 350 and 400 °C and a Ti-poor magnetite with a Curie temperature close to 580°C. Magnetic changes after

  18. Anchialine fauna of the Corona lava tunnel (Lanzarote,Canary Islands): diversity, endemism and distribution

    DEFF Research Database (Denmark)

    Martínez, Alexandro; Palmero, A M; Brito, M C

    2009-01-01

    A checklist of 77 taxa recorded from the anchialine sections of the Corona lava tube is provided, including information on habitats, faunal distribution within the cave, and main references. Of the nine major groups recorded, Crustacea shows the highest diversity with 31 species and the highest d...

  19. Mapping the distribution of vesicular textures on silicic lavas using the Thermal Infrared Multispectral Scanner

    Science.gov (United States)

    Ondrusek, Jaime; Christensen, Philip R.; Fink, Jonathan H.

    1993-01-01

    To investigate the effect of vesicularity on TIMS (Thermal Infrared Multispectral Scanner) imagery independent of chemical variations, we studied a large rhyolitic flow of uniform composition but textural heterogeneity. The imagery was recalibrated so that the digital number values for a lake in the scene matched a calculated ideal spectrum for water. TIMS spectra for the lava show useful differences in coarsely and finely vesicular pumice data, particularly in TIMS bands 3 and 4. Images generated by ratioing these bands accurately map out those areas known from field studies to be coarsely vesicular pumice. These texture-related emissivity variations are probably due to the larger vesicles being relatively deeper and separated by smaller septa leaving less smooth glass available to give the characteristic emission of the lava. In studies of inaccessible lava flows (as on Mars) areas of coarsely vesicular pumice must be identified and avoided before chemical variations can be interpreted. Remotely determined distributions of vesicular and glassy textures can also be related to the volatile contents and potential hazards associated with the emplacement of silicic lava flows on Earth.

  20. Recycled oceanic crust observed in plagioclase within the source of Mauna Loa Lavas

    NARCIS (Netherlands)

    Sobolev, A.V.; Hofmann, A.W.; Nikogosian, I.; Delgado, J.

    2000-01-01

    The hypothesis that mantle plumes contain recycled oceanic crust is now widely accepted. Some specific source components of the Hawaiian plume have been inferred to represent recycled oceanic basalts, pelagic sediments or oceanic gabbros. Bulk lava compositions, however, retain the specific trace-

  1. Recycled oceanic crust observed in "ghost" plagioclase within the source of Mauna Loa lavas.

    NARCIS (Netherlands)

    Sobolev, A.V.; Hofmann, A.W.; Nikogosian, I.

    2000-01-01

    The hypothesis that mantle plumes contain recycled oceanic crust is now widely accepted. Some specific source components of the Hawaiian plume have been inferred to represent recycled oceanic basalts, pelagic sediments or oceanic gabbros. Bulk lava compositions, however, retain the specific trace-

  2. Ascent and emplacement dynamics of obsidian lavas inferred from microlite textures

    Science.gov (United States)

    Befus, Kenneth S.; Manga, Michael; Gardner, James E.; Williams, Matthew

    2015-10-01

    To assess the eruption and emplacement of volumetrically diverse rhyolite lavas, we measured microlite number densities and orientations from samples collected from nine lavas in Yellowstone Caldera and two from Mono Craters, USA. Microlite populations are composed of Fe-Ti oxides ± alkali feldspar ± clinopyroxene. Number densities range from 108.11 ± 0.03 to 109.45 ± 0.15 cm-3 and do not correlate with distance from the vent across individual flows and are remarkably similar between large- and small-volume lavas. Together, those observations suggest that number densities are unmodified during emplacement and that ascent rates in the conduit are similar between small domes and large lava flows. Microtextures produced by continuous decompression experiments best replicate natural textures at decompression rates of 1-2 MPa hr-1. Acicular microlites have a preferred orientation in all natural samples. Because the standard deviation of microlite orientation does not become better aligned with distance travelled, we conclude that microlites exit the conduit aligned and that strain during subaerial flow was insufficient to further align microlites. The orientations of microlite trend and plunge in near-vent samples indicate that pure shear was the dominant style of deformation in the conduit. We speculate that collapsing permeable foam(s) provides a mechanism to concurrently allow microlite formation and alignment in response to the combination of degassing and flattening by pure shear.

  3. Long-term monitoring of SO2 quiescent degassing from Nyiragongo's lava lake

    Science.gov (United States)

    Arellano, S.; Yalire, M.; Galle, B.; Bobrowski, N.; Dingwell, A.; Johansson, M.; Norman, P.

    2017-10-01

    The activity of open-vent volcanoes with an active lava-lake, such as Nyiragongo, is characterized by persistent degassing, thus continuous monitoring of the rate, volume and fate of their gas emissions is of great importance to understand their geophysical state and their potential impact. We report results of SO2 emission measurements from Nyiragongo conducted between 2004 and 2012 with a network of ground-based scanning-DOAS (Differential Optical Absorption Spectroscopy) remote sensors. The mean SO2 emission rate is found to be 13 ± 9 kg s-1, similar to that observed in 1959. Daily emission rate has a distribution close to log-normal and presents large inter-day variability, reflecting the dynamics of percolation of magma batches of heterogeneous size distribution and changes in the effective permeability of the lava lake. The degassed S content is found to be between 1000 and 2000 ppm from these measurements and the reported magma flow rates sustaining the lava lake. The inter-annual trend and plume height statistics indicate stability of a quiescently degassing lava lake during the period of study.

  4. Piiriäärne lava valmistub taas esietenduseks / Margus Haav

    Index Scriptorium Estoniae

    Haav, Margus, 1969-

    2008-01-01

    Lõuna-Eestis Lilli külas algaval Nava lava festivalil tuuakse publiku ette Nava talu peremehe Jaak Kõdari näidend "Jukra", lavastaja Silvia Soro. Üht kandvat rolli mängib näitleja Lembit Eelmäe

  5. Monitoring the Growth of a Lava Flow Field Using Eruptive Tremor

    Science.gov (United States)

    Eibl, Eva P. S.; Bean, Christopher J.; Jonsdottir, Ingibjörg; Höskuldsson, Armann; Thordarson, Thorvaldur; Coppola, Diego; Witt, Tanja; Walter, Thomas R.

    2017-04-01

    Monitoring the change in eruptive style during an eruption, forecasting the height of a plume or distribution of ash or forecasting which areas a lava flow will inundate are important challenges during an eruption. These forecasts are often based on parameters such as effusion rate - which is commonly derived from Spectroradiometer data but also linked to seismic tremor amplitude or energy. Using a seismic array we analyse and locate eruptive tremor during the Bardarbunga eruption at Holuhraun 2014/15. We observed that two to three seismic tremor sources were active at the same time and that these sources have different underlying physical sources related to (i) shallow processes in the vents, (ii) intrusions at shallow depth and (iii) growing edges of a lava flow field. The clear correlation of tremor sources with the edges of a growing lava flow field is surprising, but does suggest that tremor can be used to monitor the growth of a lava flow field in near real-time.

  6. Anisotropy of Magnetic Susceptibility Studies in Lava Flows of the Eastern Anatolia Region, Turkey

    Science.gov (United States)

    Ucar, Hakan; Cengiz Cinku, Mualla

    2017-04-01

    Eastern Anatolia comprises one of the high plateaus of the Alpine-Himalaya mountain belt with an average elevation of 2 km above the sea level. Available geochronologic data indicate that the volcanism started in the south of the region around the north of Lake Van and continued towards the norths in a age interval of 15.0 Ma to 0.4 Ma. The products are exposed as stratovolcanoes like Agri, Tendurek, Suphan and Girekol with the eruption of andesitic to rhyolitic lavas, ignimbrites and basaltic lava flows. In this study, anisotropy of magnetic susceptibility measurements were carried out on different lava flows (Tendurek, Girekol and Suphan) to determine the flow direction of lavas. It has been shown that the direction of maximum susceptibility is associated with magma flow direction in the vertical direction, while a horizontal flow direction is predicted for the volcano structure of Suphan. Anisotropy of magnetic measurements show a trend of lineation towards the center of the projection and shallow-dipping foliations which are largely scattered.

  7. Lillikate suvi on Nava Lava päralt / Airi Hallik

    Index Scriptorium Estoniae

    Hallik, Airi, 1975-

    2008-01-01

    Lõuna-Eestis Lilli külas asuva Nava talu Nava Lava suvistest üritustest. Olulisim ettevõtmine oli talu peremehe Jaak Kõdari talu ajaloost kirjutatud näitemängu "Jukra" lavale toomine. Tänavu oli talu aidas avatud ka Lembit Sootsi maalinäitus

  8. Comparative fracture strength analysis of Lava and Digident CAD/CAM zirconia ceramic crowns

    Science.gov (United States)

    Kwon, Taek-Ka; Pak, Hyun-Soon; Han, Jung-Suk; Lee, Jai-Bong; Kim, Sung-Hun

    2013-01-01

    PURPOSE All-ceramic crowns are subject to fracture during function. To minimize this common clinical complication, zirconium oxide has been used as the framework for all-ceramic crowns. The aim of this study was to compare the fracture strengths of two computer-aided design/computer-aided manufacturing (CAD/CAM) zirconia crown systems: Lava and Digident. MATERIALS AND METHODS Twenty Lava CAD/CAM zirconia crowns and twenty Digident CAD/CAM zirconia crowns were fabricated. A metal die was also duplicated from the original prepared tooth for fracture testing. A universal testing machine was used to determine the fracture strength of the crowns. RESULTS The mean fracture strengths were as follows: 54.9 ± 15.6 N for the Lava CAD/CAM zirconia crowns and 87.0 ± 16.0 N for the Digident CAD/CAM zirconia crowns. The difference between the mean fracture strengths of the Lava and Digident crowns was statistically significant (Pveneering porcelain and the core whereas the Digident CAD/CAM zirconia crowns showed fracture only of the veneering porcelain. CONCLUSION The fracture strengths of CAD/CAM zirconia crowns differ depending on the compatibility of the core material and the veneering porcelain. PMID:23755332

  9. "Pit Craters", lava tubes, and open vertical volcanic conduits in Hawaii: a problem in terminology

    Directory of Open Access Journals (Sweden)

    William R. Halliday

    1998-01-01

    Full Text Available Almost from the 1849 publication of the term pit crater, volcanologists have disagreed about the parameters differentiating these features from other vertical volcanic structures. Kaluaiki is a jameo giving entry to Thurston Lava Tube in Hawaii Volcanoes National Park. Long-standing misidentification of it as a pit crater is an example of misunderstandings arising from the lack of a clear definition of pit crater. In general, pit craters are unrelated to lava tube caves genetically, but two special cases are discussed. One probably is genetically related to a rift tube deep below the surface; the other is a complex of a small pit crater with a partial rim of accreted plates plus an ordinary-seeming lava tube cave. The term pit crater should be redefined in such a way that it excludes collapses or subsidences related to ordinary superficial lava tubes and open vertical volcanic conduits. Otherwise, a non-definition like that currently listed for agglomerate may be appropriate.

  10. Paleomagnetism and geochronology of the Pliocene-Pleistocene lavas in Iceland

    NARCIS (Netherlands)

    McDougall, Ian; Wensink, H.

    Potassium-argon dates are reported on five basalt samples from the Pliocene-Pleistocene sequence of lavas in the Jökuldalur area, northeastern Iceland. These dates confirm the correlations previously made with the geological time scale by means of paleomagnetic stratigraphy. The R1 and N2 polarity

  11. Communicating Science to Officials and People at Risk During a Slow-Motion Lava Flow Crisis

    Science.gov (United States)

    Neal, C. A.; Babb, J.; Brantley, S.; Kauahikaua, J. P.

    2015-12-01

    From June 2014 through March 2015, Kīlauea Volcano's Púu ´Ō´ō vent on the East Rift Zone produced a tube-fed pāhoehoe lava flow -the "June 27th flow" - that extended 20 km downslope. Within 2 months of onset, flow trajectory towards populated areas in the Puna District caused much concern. The USGS Hawaiian Volcano Observatory (HVO) issued a news release of increased hazard on August 22 and began participating in public meetings organized by Hawai`i County Mayor and Civil Defense two days later. On September 4, HVO upgraded the volcano alert level to WARNING based on an increased potential for lava to reach homes and infrastructure. Ultimately, direct impacts were modest: lava destroyed one unoccupied home and one utility pole, crossed a rural roadway, and partially inundated a waste transfer station, a cemetery, and agricultural land. Anticipation that lava could reach Pāhoa Village and cross the only major access highway, however, caused significant disruption. HVO scientists employed numerous methods to communicate science and hazard information to officials and the at-risk public: daily (or more frequent) written updates of the lava activity, flow front locations and advance rates; frequent updates of web-hosted maps and images; use of the 'lines of steepest descent' method to indicate likely lava flow paths; consistent participation in well-attended community meetings; bi-weekly briefings to County, State, and Federal officials; correspondence with the public via email and recorded phone messages; participation in press conferences and congressional briefings; and weekly newspaper articles (Volcano Watch). Communication lessons both learned and reinforced include: (1) direct, frequent interaction between scientists and officials and at-risk public builds critical trust and understanding; (2) images, maps, and presentations must be tailored to audience needs; (3) many people are unfamiliar with maps (oblique aerial photographs were more effective); (4

  12. The role of unsteady effusion rates on inflation in long-lived lava flow fields

    Science.gov (United States)

    Rader, E.; Vanderkluysen, L.; Clarke, A.

    2017-11-01

    The emission of volcanic gases and particles can have global and lasting environmental effects, but their timing, tempo, and duration can be problematic to quantify for ancient eruptions where real-time measurements are absent. Lava flows, for example, may be long-lasting, and their impact is controlled by the rate, tempo, and vigor of effusion. These factors are currently difficult to derive from the geologic record but can have large implications for the atmospheric impact of an eruption. We conducted a set of analogue experiments on lava flow inflation aiming at connecting lava morphologies preserved in the rock record to eruption tempo and dynamics through pulsating effusion rates. Inflation, a process where molten material is injected beneath the crust of an active lava flow and lifts it upwards, is a common phenomenon in basaltic volcanic systems. This mechanism requires three components: a) a coherent, insulating crust; b) a wide-spread molten core; and c) pressure built up beneath the crust from a sustained supply of molten material. Inflation can result in a lava flow growing tens of meters thick, even in flow fields that expand hundreds of square kilometers. It has been documented that rapid effusion rates tend to create channels and tubes, isolating the active part of the flow from the stagnant part, while slow effusion rates may cause crust to form quickly and seize up, forcing lava to overtop the crust. However, the conditions that allow for inflation of large flow fields have not previously been evaluated in terms of effusion rate. By using PEG 600 wax and a programmable pump, we observe how, by pulsating effusion rate, inflation occurs even in very low viscosity basaltic eruptions. We show that observations from inflating Hawaiian lava flows correlate well with experimental data and indicate that instantaneous effusion rates may have been 3 times higher than average effusion rates during the emplacement of the 23 January 1988 flow at Kīlauea (Hawai

  13. Tachylyte in Cenozoic basaltic lavas from the Czech Republic and Iceland: contrasting compositional trends

    Science.gov (United States)

    Ulrych, Jaromír; Krmíček, Lukáš; Teschner, Claudia; Řanda, Zdeněk; Skála, Roman; Jonášová, Šárka; Fediuk, Ferry; Adamovič, Jiří; Pokorný, Richard

    2017-10-01

    Tachylytes from rift-related volcanic rocks were recognized as: (i) irregular veinlets in host alkaline lava flows of the Kozákov volcano, Czech Republic, (ii) (sub)angular xenoliths in alkaline lava of the feeding channel of the Bukovec volcano, Czech Republic, and (iii) paleosurface of a tholeiitic lava flow from Hafrafell, Iceland. The tachylyte from Kozákov is phonotephrite to tephriphonolite in composition while that from Bukovec corresponds to trachyandesite to tephriphonolite. Both glass and host rock from Hafrafell are of tholeiitic basalt composition. The tachylyte from Kozákov, compared with the host rock, revealed a substantial enrichment in major elements such as Si, Al and alkalis along with Rb, Sr, Ba, Nb, Zr, REE, Th and U. The tachylyte from Bukovec displays contrasting trends in the incompatible element contents. The similarity in composition of the Hafrafell tachylyte paleosurface layer and parental tholeiitic basalt is characteristic for lavas. The host/parent rocks and tachylytes have similar initial Sr-Nd characteristics testifying for their co-magmatic sources. The initial ɛNd values of host/parent rocks and tachylytes from the Bohemian Massif (+3.4 to +3.9) and those from Iceland (+6.3) are interpreted as primary magma values. Only the tachylyte from Bukovec shows a different ɛNd value of -2.1, corresponding to a xenolith of primarily sedimentary/metamorphic origin. The tachylyte from Kozákov is a product of an additional late magmatic portion of fluids penetrating through an irregular fissure system of basaltic lava. The Bukovec tachylyte is represented by xenoliths originated during the interaction of ascending basaltic melt with granitoids or orthogneisses, whereas the Hafrafell tachylyte is a product of a rapid cooling on the surface of a basalt flow.

  14. Tracing Altiplano-Puna plateau surface uplift via radiogenic isotope composition of Andean arc lavas

    Science.gov (United States)

    Scott, E. M.; Allen, M. B.; Macpherson, C.; McCaffrey, K. J. W.; Davidson, J.; Saville, C.

    2016-12-01

    We have compiled published geochemical data for Jurassic to Holocene Andean arc lavas from 5oN to 47oS, covering the current extent of the northern, central and southern volcanic zones. Using this dataset we evaluate the spatial and temporal evolution of age corrected Sr- and Nd-radiogenic isotopes in arc lavas at a continental-scale, in order to understand the tectonic and surface uplift histories of the Andean margin. It has long been noted that baseline 87Sr/86Sr and 143Nd/144Nd ratios of Quaternary lavas from the central volcanic zone, located within the Altiplano-Puna plateau, are distinct from volcanic rocks to the north and south. This is commonly attributed to greater crustal thickness, which increases to roughly twice that of the average continental crust within the Altiplano-Puna plateau. By comparing 87Sr/86Sr and 143Nd/144Nd ratios in Quaternary lavas to published crustal thickness models, present day topography and the compositions of basement terranes, we note that Sr- and Nd-isotope values of Quaternary lavas are an effective proxy for present day regional elevation. In contrast, variation in basement terranes has only a small, second order effect on isotopic composition at the scale of our study. Using this isotopic proxy, we infer the spatial extent of the plateau and its surface uplift history from the Jurassic to the present. Our results concur with a crustal thickening model of continued surface uplift, which initiated in the Altiplano, with deformation propagating southwards into the Puna throughout the Neogene and then continuing in central Chile and Argentina up to the present day.

  15. Petrogenesis of Rinjani Post-1257-Caldera-Forming-Eruption Lava Flows

    Directory of Open Access Journals (Sweden)

    Heryadi Rachmat

    2016-06-01

    Full Text Available DOI:10.17014/ijog.3.2.107-126After the catastrophic 1257 caldera-forming eruption, a new chapter of Old Rinjani volcanic activity beganwith the appearance of Rombongan and Barujari Volcanoes within the caldera. However, no published petrogeneticstudy focuses mainly on these products. The Rombongan eruption in 1944 and Barujari eruptions in pre-1944, 1966,1994, 2004, and 2009 produced basaltic andesite pyroclastic materials and lava flows. A total of thirty-one sampleswere analyzed, including six samples for each period of eruption except from 2004 (only one sample. The sampleswere used for petrography, whole-rock geochemistry, and trace and rare earth element analyses. The Rombonganand Barujari lavas are composed of calc-alkaline and high K calc-alkaline porphyritic basaltic andesite. The magmashows narrow variation of SiO2 content that implies small changes during its generation. The magma that formedRombongan and Barujari lavas is island-arc alkaline basalt. Generally, data show that the rocks are enriched in LargeIon Lithophile Elements (LILE: K, Rb, Ba, Sr, and Ba and depleted in High Field Strength Elements (HFSE: Y, Ti,and Nb which are typically a suite from a subduction zone. The pattern shows a medium enrichment in Light REEand relatively depleted in Heavy REE. The processes are dominantly controlled by fractional crystallization andmagma mixing. All of the Barujari and Rombongan lavas would have been produced by the same source of magmawith little variation in composition caused by host rock filter process. New flux of magma would likely have occurredfrom pre-1944 until 2009 period that indicates slightly decrease and increase of SiO2 content. The Rombongan andBarujari lava generations show an arc magma differentiation trend.

  16. Cooling of a channeled lava flow with non-Newtonian rheology: crust formation and surface radiance

    Directory of Open Access Journals (Sweden)

    Stefano Santini

    2011-12-01

    Full Text Available We present here the results from dynamical and thermal models that describe a channeled lava flow as it cools by radiation. In particular, the effects of power-law rheology and of the presence of bends in the flow are considered, as well as the formation of surface crust and lava tubes. On the basis of the thermal models, we analyze the assumptions implicit in the currently used formulae for evaluation of lava flow rates from satellite thermal imagery. Assuming a steady flow down an inclined rectangular channel, we solve numerically the equation of motion by the finite-volume method and a classical iterative solution. Our results show that the use of power-law rheology results in relevant differences in the average velocity and volume flow rate with respect to Newtonian rheology. Crust formation is strongly influenced by power-law rheology; in particular, the growth rate and the velocity profile inside the channel are strongly modified. In addition, channel curvature affects the flow dynamics and surface morphology. The size and shape of surface solid plates are controlled by competition between the shear stress and the crust yield strength: the degree of crust cover of the channel is studied as a function of the curvature. Simple formulae are currently used to relate the lava flow rate to the energy radiated by the lava flow as inferred from satellite thermal imagery. Such formulae are based on a specific model, and consequently, their validity is subject to the model assumptions. An analysis of these assumptions reveals that the current use of such formulae is not consistent with the model.

  17. Risk from lava flow inundations in densely populated areas: the case of Etna volcano

    Science.gov (United States)

    Del Negro, C.; Cappello, A.; Bilotta, G.; Ganci, G.; Herault, A.

    2016-12-01

    The ever-expanding use of areas near the volcano increases the potential impact of future eruptions on the regional economy and on the health and safety of the inhabitants. The increasing exposure of a larger population, which has almost tripled in the area around Mt. Etna during the last 150 years, is often derived from a poor assessment of the volcanic hazard, allowing inappropriate land use in vulnerable areas. Therefore, a correct assessment is an essential component in reducing the losses due to volcanic disasters. A detailed map showing areas that are likely to be inundated by future lava flows is extremely useful, allowing people living nearby to judge for themselves the relation between potentially dangerous areas and their daily lives. Here we quantify the lava flow risk at Etna volcano using a GIS-based methodology that integrates the hazard with the exposure of elements at stake. The hazard, showing the long-term probability related to lava flow inundation, is obtained combining three different kinds of information: the spatiotemporal probability for the future opening of new eruptive vents, the event probability associated with classes of expected eruptions, and the overlapping of lava flow paths simulated by the MAGFLOW model. Data including all elements at stake were gathered from different web portals and organized in four thematic layers: population, strategic buildings, other buildings and networks, and land use. The total exposure is given by a weighted linear combination of the four thematic layers, where weights are calculated using the Analytic Hierarchy Process (AHP). The resulting risk map shows the likely damage caused by a lava flow eruption, allowing rapidly visualizing the areas in which there would be the greatest amount of losses in case of a flank eruption occurs at Etna.

  18. Emplacement dynamics and lava field evolution of the flood basalt eruption at Holuhraun, Iceland: Observations from field and remote sensing data

    Science.gov (United States)

    Pedersen, Gro; Höskuldsson, Armann; Riishuus, Morten S.; Jónsdóttir, Ingibjörg; Thórdarson, Thorvaldur; Dürig, Tobias; Gudmundsson, Magnus T.; Durmont, Stephanie

    2016-04-01

    The Holuhraun eruption (Aug 2014- Feb 2015) is the largest effusive eruption in Iceland since the Laki eruption in 1783-84, with an estimated lava volume of ~1.6 km3 covering an area of ~83 km2. The eruption provides an unprecedented opportunity to study i) lava morphologies and their emplacement styles, ii) Morphological transitions iii) the transition from open to closed lava pathways and iv) the implication of lava pond formation. This study is based on three different categories of data; field data, airborne data and satellite data. The field data include tracking of the lava advancement by Global Positioning System (GPS) measurements and georeferenced GoPro cameras allowing classification of the lava margin morphology. Furthermore, video footage on-site documented lava emplacement. Complimentary observations have been provided from aircraft platforms and by satellite data. Of particular importance for lava morphology observations are 1-12 m/pixel airborne Synthetic Aperture Radar (SAR) images (x-band), as well as SAR data from TerraSAR-X and COSMO-SkyMed satellites. The Holuhraun lava field comprises a continuum of morphologies from pāhoehoe to 'a'ā, which have varied temporally and spatially. Shelly pāhoehoe lava was the first morphology to be observed (08-29). Spatially, this lava type was not widely distributed, but was emplaced throughout the eruption close to the vent area and the lava channels. Slabby pāhoehoe lava was initially observed the 08-31 and was observed throughout most of the eruption during the high-lava-flux phase of new lava lobe emplacement. 'A'ā lavas were the dominating morphology the first three months of the eruption and was first observed 09-01 like Rubbly pāhoehoe lava. Finally, Spiny pāhoehoe lava was first observed the 09-05 as a few marginal outbreaks along the fairly inactive parts of the 'a'ā lava lobe. However, throughout the eruption this morphology became more important and from mid-November/beginning of December the

  19. The Hawaiian Volcano Observatory's current approach to forecasting lava flow hazards (Invited)

    Science.gov (United States)

    Kauahikaua, J. P.

    2013-12-01

    Hawaiian Volcanoes are best known for their frequent basaltic eruptions, which typically start with fast-moving channelized `a`a flows fed by high eruptions rates. If the flows continue, they generally transition into pahoehoe flows, fed by lower eruption rates, after a few days to weeks. Kilauea Volcano's ongoing eruption illustrates this--since 1986, effusion at Kilauea has mostly produced pahoehoe. The current state of lava flow simulation is quite advanced, but the simplicity of the models mean that they are most appropriately used during the first, most vigorous, days to weeks of an eruption - during the effusion of `a`a flows. Colleagues at INGV in Catania have shown decisively that MAGFLOW simulations utilizing satellite-derived eruption rates can be effective at estimating hazards during the initial periods of an eruption crisis. However, the algorithms do not simulate the complexity of pahoehoe flows. Forecasts of lava flow hazards are the most common form of volcanic hazard assessments made in Hawai`i. Communications with emergency managers over the last decade have relied on simple steepest-descent line maps, coupled with empirical lava flow advance rate information, to portray the imminence of lava flow hazard to nearby communities. Lavasheds, calculated as watersheds, are used as a broader context for the future flow paths and to advise on the utility of diversion efforts, should they be contemplated. The key is to communicate the uncertainty of any approach used to formulate a forecast and, if the forecast uses simple tools, these communications can be fairly straightforward. The calculation of steepest-descent paths and lavasheds relies on the accuracy of the digital elevation model (DEM) used, so the choice of DEM is critical. In Hawai`i, the best choice is not the most recent but is a 1980s-vintage 10-m DEM--more recent LIDAR and satellite radar DEM are referenced to the ellipsoid and include vegetation effects. On low-slope terrain, steepest

  20. Continuous gravity measurements reveal a low-density lava lake at Kīlauea Volcano, Hawai‘i

    Science.gov (United States)

    Carbone, Daniele; Poland, Michael P.; Patrick, Matthew R.; Orr, Tim R.

    2013-01-01

    On 5 March 2011, the lava lake within the summit eruptive vent at Kīlauea Volcano, Hawai‘i, began to drain as magma withdrew to feed a dike intrusion and fissure eruption on the volcanoʼs east rift zone. The draining was monitored by a variety of continuous geological and geophysical measurements, including deformation, thermal and visual imagery, and gravity. Over the first ∼14 hours of the draining, the ground near the eruptive vent subsided by about 0.15 m, gravity dropped by more than 100 μGal, and the lava lake retreated by over 120 m. We used GPS data to correct the gravity signal for the effects of subsurface mass loss and vertical deformation in order to isolate the change in gravity due to draining of the lava lake alone. Using a model of the eruptive vent geometry based on visual observations and the lava level over time determined from thermal camera data, we calculated the best-fit lava density to the observed gravity decrease — to our knowledge, the first geophysical determination of the density of a lava lake anywhere in the world. Our result, 950 +/- 300 kg m-3, suggests a lava density less than that of water and indicates that Kīlaueaʼs lava lake is gas-rich, which can explain why rockfalls that impact the lake trigger small explosions. Knowledge of such a fundamental material property as density is also critical to investigations of lava-lake convection and degassing and can inform calculations of pressure change in the subsurface magma plumbing system.

  1. Integrated, multi-parameter, investigation of eruptive dynamics at Santiaguito lava dome, Guatemala

    Science.gov (United States)

    Lavallée, Yan; De Angelis, Silvio; Rietbrock, Andreas; Lamb, Oliver; Hornby, Adrian; Lamur, Anthony; Kendrick, Jackie E.; von Aulock, Felix W.; Chigna, Gustavo

    2016-04-01

    Understanding the nature of the signals generated at volcanoes is central to hazard mitigation efforts. Systematic identification and understanding of the processes responsible for the signals associated with volcanic activity are only possible when high-resolution data are available over relatively long periods of time. For this reason, in November 2014, the Liverpool Earth Observatory (LEO), UK, in collaboration with colleagues of the Instituto Nacional de Sismologia, Meteorologia e Hidrologia (INSIVUMEH), Guatemala, installed a large multi-parameter geophysical monitoring network at Santiaguito - the most active volcano in Guatemala. The network, which is to date the largest temporary deployment on Santiaguito, includes nine three-component broadband seismometers, three tiltmeters, and five infrasound microphones. Further, during the initial installation campaign we conducted visual and thermal infrared measurements of surface explosive activity and collected numerous rock samples for geochemical, geophysical and rheological characterisation. Activity at Santiaguito began in 1922, with the extrusion of a series of lava domes. In recent years, persistent dome extrusion has yielded spectacularly episodic piston-like motion displayed by characteristic tilt/seismic patterns (Johnson et al, 2014). This cyclicity episodically concludes with gas emissions or gas-and-ash explosions, observed to progress along a complex fault system in the dome. The explosive activity is associated with distinct geophysical signals characterised by the presence of very-long period earthquakes as well as more rapid inflation/deflation cycles; the erupted ash further evidences partial melting and thermal vesiculation resulting from fault processes (Lavallée et al., 2015). One year of data demonstrates the regularity of the periodicity and intensity of the explosions; analysis of infrasound data suggests that each explosion expulses on the order of 10,000-100,000 kg of gas and ash. We

  2. Did the massive magnetite "lava flows" of El Laco (Chile) form by magmatic or hydrothermal processes? New constraints from magnetite composition by LA-ICP-MS

    Science.gov (United States)

    Dare, Sarah A. S.; Barnes, Sarah-Jane; Beaudoin, Georges

    2015-06-01

    The El Laco magnetite deposits consist of more than 98 % magnetite but show field textures remarkably similar to mafic lava flows. Therefore, it has long been suggested that they represent a rare example of an effusive Fe oxide liquid. Field and petrographic evidence, however, suggest that the magnetite deposits represent replacement of andesite flows and that the textures are pseudomorphs. We determined the trace element content of magnetite by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) from various settings at El Laco and compared them with magnetite from both igneous and hydrothermal environments. This new technique allows us to place constraints on the conditions under which magnetite in these supposed magnetite "lava flows" formed. The trace element content of magnetite from the massive magnetite samples is different to any known magmatic magnetite, including primary magnetite phenocrysts from the unaltered andesite host rocks at El Laco. Instead, the El Laco magnetite is most similar in composition to hydrothermal magnetite from high-temperature environments (>500 °C), such as iron oxide-copper-gold (IOCG) and porphyry-Cu deposits. The magnetite trace elements from massive magnetite are characterised by (1) depletion in elements considered relatively immobile in hydrothermal fluids (e.g. Ti, Al, Cr, Zr, Hf and Sc); (2) enrichment in elements that are highly incompatible with magmatic magnetite (rare earth elements (REE), Si, Ca, Na and P) and normally present in very low abundance in magmatic magnetite; (3) high Ni/Cr ratios which are typical of magnetite from hydrothermal environments; and (4) oscillatory zoning of Si, Ca, Mg, REE and most high field strength elements, and zoning truncations indicating dissolution, similar to that formed in hydrothermal Fe skarn deposits. In addition, secondary magnetite in altered, brecciated host rock, forming disseminations and veins, has the same composition as magnetite from the massive

  3. Perched Lava Pond Complex on South Rift of Axial Volcano Revealed in AUV Mapping

    Science.gov (United States)

    Paduan, J. B.; Clague, D. A.; Caress, D. W.; Thomas, H. J.

    2013-12-01

    An extraordinary lava pond complex is located on Axial Volcano's distal south rift. It was discovered in EM300 multibeam bathymetry collected in 1998, and explored and sampled with ROVs Tiburon in 2005 and Doc Ricketts in 2013. It was surveyed with the MBARI Mapping AUV D. Allan B. in 2011, in a complicated mission first flying above the levees at constant depth, then skimming ~5 m over the levees at a different constant depth to survey the floors, then twice switching to constant altitude mode to map outside the ponds. The AUV navigation was adjusted using the MB-System tool mbnavadjust so that bathymetric features match in overlapping and crossing swaths. The ~1-m resolution AUV bathymetry reveals extremely rough terrain, where low-resolution EM300 data had averaged acoustic returns and obscured details of walls, floors, a breach and surrounding flows, and gives context to the ROV observations and samples. The 6 x 1.5 km pond complex has 4 large and several smaller drained ponds with rims 67 to 106 m above the floors. The combined volume before draining was 0.56 km3. The ponds overflowed to build lobate-flow levees with elongate pillows draping outer flanks, then drained, leaving lava veneer on vertical inner walls. Levee rim depths vary by only 10 m and are deeper around the southern ponds. Deep collapse-pits in the levees suggest porosity of pond walls. The eastern levee of the northeastern pond breached, draining the interconnected ponds, and fed thick, rapidly-emplaced, sheet-flows along the complex's east side. These flows travelled at least 5.5 km down-rift and have 19-33 m deep drained ponds. They extended up-rift as well, forming a 10 x 2.5 km ponded flow with level 'bathtub rings' as high as 35 m above the floor marking that flow's high-stand. Despite the breach, at least 0.066 km3 of the molten interior of the large ponds also drained back down the eruptive fissures, as the pond floors are deeper than the sill and sea floor outside the complex. Tumulus

  4. Sill and lava geochemistry of the mid-Norway and NE Greenland conjugate margins

    DEFF Research Database (Denmark)

    Neumann, Else-Ragnhild; Svensen, Henrik; Tegner, Christian

    2013-01-01

    This paper presents major, trace-elements, and Sr-Nd isotopes for two prominent sills formed during the opening of the North Atlantic, sampled by the Utgard borehole (6607/5-2) in the VOring Plateau. The Utgard sills are compared to opening-related lavas recovered from ODP Leg 104 Hole 642E farther......, and 0.70303-0.70306 and 0.51297-0.51299 in the Lower Sill. Alteration is minor. The Utgard melts originated by partial melting of an asthenospheric, depleted mantle source (DMM or Iceland Rift Zone, IRZ, type) with chemical characteristics similar to the source that gave rise to NE Greenland lavas....... The Utgard magmas underwent extensive fractional crystallization in the lower crust (Upper Sill: >70%; Lower Sill: >55%) with removal mainly of olivine and pyroxenes, accompanied by 1% assimilation of crustal melts. This crystallization formed significant masses of dense cumulates (approximate to 3.25 g/cm(3...

  5. Geometry of Lava Tubes and Rheological Properties of Basalts: Piton De La Fournaise (reunion Island)

    Science.gov (United States)

    Coppola, D.; Cigolini, C.

    We have studied the geometry of selected sectors of lava tubes at Piton de la Fournaise (named Caverne Bateau and Kapor, respectively). An accurate survey and mapping (at the scale 1:750) allowed us to identify nearly elliptical transverse sections of the tube with multiple inner accretions of several lateral benches. Tube sectors with larger transverse sections are formed under steady-state effusion conditions and higher flow- rate, whereas the emplacement of lateral benches seems to be related to lower flow- rates, generally associated to fluctuations in the effusion rate at the crater. In some cases, transverse sections are subrectangular with moderately high height/width ratios, likely due to thermal erosion at the base of the tunnel. Image analyses on selected sam- ples allowed us to estimate the rheological parameters that characterize these basalts. Near-liquidus viscosities, calculated by means of modified Einstein-Roscoe equations, approach 1000 Pa s, and are comparable with viscosities measured during the erup- tion of September 1999. Under these conditions, the lavas approach a Newtonian be- haviour, whereas on cooling they develop yield strengths typical of non-Newtonian fluids. We simulated the cooling history of a basaltic lava from Piton the la Four- naise by using the computer code MELTS. This allowed us to compute the degree of crystallinity within the cooling lava in function of the chemical evolution of the crys- tallizing melt. Calculated yield strengths relative to several cooling steps allowed us to interpolate an exponential relationship between yield strength versus temperature. This methodological approach seems to be a powerful tool to calibrate the rheological parameters which characterize single eruptions.

  6. Quantitative geometric description of fracture systems in an andesite lava flow using terrestrial laser scanner data

    Science.gov (United States)

    Massiot, Cécile; Nicol, Andrew; Townend, John; McNamara, David D.; Garcia-Sellés, David; Conway, Chris E.; Archibald, Garth

    2017-07-01

    Permeability hosted in andesitic lava flows is dominantly controlled by fracture systems, with geometries that are often poorly constrained. This paper explores the fracture system geometry of an andesitic lava flow formed during its emplacement and cooling over gentle paleo-topography, on the active Ruapehu volcano, New Zealand. The fracture system comprises column-forming and platy fractures within the blocky interior of the lava flow, bounded by autobreccias partially observed at the base and top of the outcrop. We use a terrestrial laser scanner (TLS) dataset to extract column-forming fractures directly from the point-cloud shape over an outcrop area of ∼3090 m2. Fracture processing is validated using manual scanlines and high-resolution panoramic photographs. Column-forming fractures are either steeply or gently dipping with no preferred strike orientation. Geometric analysis of fractures derived from the TLS, in combination with virtual scanlines and trace maps, reveals that: (1) steeply dipping column-forming fracture lengths follow a scale-dependent exponential or log-normal distribution rather than a scale-independent power-law; (2) fracture intensities (combining density and size) vary throughout the blocky zone but have similar mean values up and along the lava flow; and (3) the areal fracture intensity is higher in the autobreccia than in the blocky zone. The inter-connected fracture network has a connected porosity of ∼0.5 % that promote fluid flow vertically and laterally within the blocky zone, and is partially connected to the autobreccias. Autobreccias may act either as lateral permeability connections or barriers in reservoirs, depending on burial and alteration history. A discrete fracture network model generated from these geometrical parameters yields a highly connected fracture network, consistent with outcrop observations.

  7. A low-cost method applicable worldwide for remotely mapping lava dome growth

    Science.gov (United States)

    Chaussard, Estelle

    2017-07-01

    Lava dome growth and collapse represents both a significant hazard, as it can trigger pyroclastic density currents, and a monitoring challenge, limiting monitoring to a few known active volcanoes. Here, I propose a new differencing technique based on Synthetic Aperture Radar (SAR) amplitude images to quantify the extent of lava dome growth. This differencing technique, which is both low cost and can be utilized worldwide, is applied to SAR amplitude images at Mount St. Helens and validated using 2004-2008 aerial photography observations. Difference of amplitude images accurately characterize the dome growth location. The low ground resolution of the 2004-2008 SAR data leads to underestimation by 10 to 15% of the dome extent, but the accuracy of this method will increase with the improved resolution of current and future SAR missions. Amplitude images are a low-level SAR product available from all SAR satellites, mostly freely, making the proposed method ideal for systematic, low-cost monitoring of lava dome growth worldwide with minimum processing required.

  8. The hottest lavas of the Phanerozoic and the survival of deep Archaean reservoirs

    Science.gov (United States)

    Trela, Jarek; Gazel, Esteban; Sobolev, Alexander V.; Moore, Lowell; Bizimis, Michael; Jicha, Brian; Batanova, Valentina G.

    2017-06-01

    Large igneous provinces and some hotspot volcanoes are thought to form above thermochemical anomalies known as mantle plumes. Petrologic investigations that support this model suggest that plume-derived melts originated at high mantle temperatures (greater than 1,500 °C) relative to those generated at ambient mid-ocean ridge conditions (about 1,350 °C). Earth's mantle has also cooled appreciably during its history and the temperatures of modern mantle derived melts are substantially lower than those produced during the Archaean (2.5 to 4.0 billion years ago), as recorded by komatiites (greater than 1,700 °C). Here we use geochemical analyses of the Tortugal lava suite to show that these Galapagos-Plume-related lavas, which formed 89 million years ago, record mantle temperatures as high as Archaean komatiites and about 400 °C hotter than the modern ambient mantle. These results are also supported by highly magnesian olivine phenocrysts and Al-in-olivine crystallization temperatures of 1,570 +/- 20 °C. As mantle plumes are chemically and thermally heterogeneous, we interpret these rocks as the result of melting the hot core of the plume head that produced the Caribbean large igneous province. Our results imply that a mantle reservoir as hot as those responsible for some Archaean lavas has survived eons of convection in the deep Earth and is still being tapped by mantle plumes.

  9. Cosmogenic 3He in terrestrial rocks: The summit lavas of Maui

    Science.gov (United States)

    Craig, H.; Poreda, R. J.

    1986-01-01

    We have identified terrestrial cosmic rayproduced 3He in three lava flows on the crest of Haleakala Volcano on Maui, 3 km above sea level, and ≈0.5 million years old. Although these lavas, like all oceanic basalts, contain primordial 3He from the mantle, the “cosmogenic” component (3HeC) can be identified unambiguously because it is extractable only by high-temperature vacuum fusion. In contrast, a large fraction of the mantle helium resides in fluid inclusions and can be extracted by vacuum crushing, leaving a residual component with 3He/4He ratios as high as 75× those in the atmosphere, which can be liberated by melting the crushed grains. Cosmogenic 3He is present in both olivines and clinopyroxenes at 0.8-1.2 × 10-12 ml(STP)/g and constitutes 75% ± 5% of the total 3He present. The observed 3HeC levels require a cosmic ray exposure age of only some 64,000 years, much less than the actual age of the lavas, if there is no erosion. Using a model that includes effects of uplift or submergence as well as erosion, we calculate an apparent “erosion rate” of the order of 8.5 m/106 years for the western rim of the summit crater, as an example of the application of measurements of cosmogenic rare gases to terrestrial geological problems. PMID:16593671

  10. LAV@HAZARD: a Web-GIS Framework for Real-Time Forecasting of Lava Flow Hazards

    Science.gov (United States)

    Del Negro, C.; Bilotta, G.; Cappello, A.; Ganci, G.; Herault, A.

    2014-12-01

    Crucial to lava flow hazard assessment is the development of tools for real-time prediction of flow paths, flow advance rates, and final flow lengths. Accurate prediction of flow paths and advance rates requires not only rapid assessment of eruption conditions (especially effusion rate) but also improved models of lava flow emplacement. Here we present the LAV@HAZARD web-GIS framework, which combines spaceborne remote sensing techniques and numerical simulations for real-time forecasting of lava flow hazards. By using satellite-derived discharge rates to drive a lava flow emplacement model, LAV@HAZARD allows timely definition of parameters and maps essential for hazard assessment, including the propagation time of lava flows and the maximum run-out distance. We take advantage of the flexibility of the HOTSAT thermal monitoring system to process satellite images coming from sensors with different spatial, temporal and spectral resolutions. HOTSAT was designed to ingest infrared satellite data acquired by the MODIS and SEVIRI sensors to output hot spot location, lava thermal flux and discharge rate. We use LAV@HAZARD to merge this output with the MAGFLOW physics-based model to simulate lava flow paths and to update, in a timely manner, flow simulations. Thus, any significant changes in lava discharge rate are included in the predictions. A significant benefit in terms of computational speed was obtained thanks to the parallel implementation of MAGFLOW on graphic processing units (GPUs). All this useful information has been gathered into the LAV@HAZARD platform which, due to the high degree of interactivity, allows generation of easily readable maps and a fast way to explore alternative scenarios. We will describe and demonstrate the operation of this framework using a variety of case studies pertaining to Mt Etna, Sicily. Although this study was conducted on Mt Etna, the approach used is designed to be applicable to other volcanic areas around the world.

  11. Subsidence in the Parícutin lava field: Causes and implications for interpretation of deformation fields at volcanoes

    Science.gov (United States)

    Chaussard, Estelle

    2016-06-01

    Assessment of volcanic hazards includes interpretation of ground deformation signal, which, at polygenetic volcanoes often results from the superposition of deformation due to pressure changes in the magmatic system and due to surficial processes such as cooling of emplaced lava. The deformation signal associated with emplaced lava is sometimes considered negligible if fields are decades old, but if the lava thickness is great, deformation may still be occurring, possibly leading to misinterpretation of the observed deformation. Here I evaluate the 2007-2011 ground motion of the 1943-1952 lava field of the Parícutin monogenetic cinder cone, Mexico. Interferometric Synthetic Aperture Radar (InSAR) time series reveal patchy subsidence restricted to the lava field and following linear rates up to 5.5 cm/year. There is a clear correlation between subsidence rates and topography suggesting a causal relationship with deposits or lava thickness. I estimate these thicknesses in the subsiding areas using pre- and post-eruption topographic maps and show that they reach up to 200 m. A numerical model for lava flow cooling was developed considering radiation and convection from the surface, conductive transfer inside the flow and to the ground, and vesiculation and latent heat generation at the top and bottom of the flow. The model shows that compaction induced by cooling of the thick deposits emplaced 60 years ago explains the observed subsidence when conductive transfer to the ground is considered. These results demonstrate that thick deposits can keep deforming significantly even decades after their emplacement, emphasizing the importance of considering cooling processes when interpreting deformation fields at polygenetic volcanoes producing massive lava fields.

  12. Metal biogeochemistry in constructed wetlands based on fluviatile sand and zeolite- and clinopyroxene-dominated lava sand

    OpenAIRE

    Huang, Jen-How; Paul, Sonja; Mayer, Silke; Moradpour, Eloise; Hasselbach, Ralf; Gier?, Reto; Alewell, Christine

    2017-01-01

    For the first time, speciation of Fe, Mn, Zn, Ni, Cu and Pb was determined along the profiles of 8 constructed wetlands (CWs) consisting of fluviatile sand (Fluv), clinopyroxene-dominated lava sand (Cl-LS) and zeolite-dominated lava sand (Ze-LS), aiming at quantifying metal behaviour in CWs and the impact caused by different filter materials. With the exception of Mn, which underwent reductive dissolution, CWs were sinks for the studied metals. Metal accumulation rates differed in the followi...

  13. Age and petrology of alkalic postshield and rejuvenated-stage lava from Kauai, Hawaii

    Science.gov (United States)

    Clague, D.A.; Dalrymple, G.B.

    1988-01-01

    At the top of the Waimea Canyon Basalt on the island of Kauai, rare flows of alkalic postshield-stage hawaiite and mugearite overlie tholeiitic flows of the shield stage. These postshield-stage flows are 3.92 Ma and provide a younger limit for the age of the tholeiitic shield stage. The younger Koloa Volcanics consist of widespread alkalic rejuvenated-stage flows and vents of alkalic basalt, basanite, nephelinite, and nepheline melilitite that erupted between 3.65 and 0.52 Ma. All the flows older than 1.7 Ma occur in the west-northwestern half of the island and all the flows younger than 1.5 Ma occur in the east-southeastern half. The lithologies have no spatial or chronological pattern. The flows of the Koloa Volcanics are near-primary magmas generated by variable small degrees of partial melting of a compositionally heterogeneous garnet-bearing source that has about two-thirds the concentration of P2O5, rare-earth elements, and Sr of the source of the Honolulu Volcanics on the island of Oahu. The same lithology in the Koloa and Honolulu Volcanics is generated by similar degrees of partial melting of distinct source compositions. The lavas of the Koloa Volcanics can be generated by as little as 3 percent to as much as 17 percent partial melting for nepheline melilitite through alkalic basalt, respectively. Phases that remain in the residue of the Honolulu Volcanics, such as rutile and phlogopite, are exhausted during formation of the Koloa Volcanics at all but the smallest degrees of partial melting. The mantle source for Kauai lava becomes systematically more depleted in 87Sr/86Sr as the volcano evolves from the tholeiitic shield stage to the alkalic postshield stage to the alkalic rejuvenated stage: at the same time, the lavas become systematically more enriched in incompatible trace elements. On a shorter timescale, the lavas of the Koloa Volcanics display the same compositional trends, but at a lower rate of change. The source characteristics of the Koloa

  14. Paleomagnetism and paleosecular variation from the late Miocene to recent lavas of Mauritius

    Science.gov (United States)

    Doubrovine, Pavel V.; Torsvik, Trond H.; Domeier, Mathew

    2017-04-01

    We present new paleomagnetic data from the late Miocene to recent lavas of the island of Mauritius in the southwestern Indian Ocean (20.3˚ S, 57.6˚ E). The island is a shield volcano that has formed over the Reunion hotspot and is composed of three temporally-distinct series of basaltic lavas: the Older Series (4.7-8.9 Ma), the Intermediate Series (1.7-3.5 Ma) and the Younger Series (0-1 Ma). Oriented core specimens were collected from 36 sampling sites covering all three lava series. Rock magnetic analyses indicate that the remanence carriers in these basalts are pseudo-single-domain titanomagnetites with variable degrees of high-temperature oxidation. Nearly half of the sites showed pervasive magnetic overprints imparted by lightning strikes. Nonetheless, in almost all cases (35 sites), we were able to isolate the characteristic (primary) remanence directions through detailed thermal and alternating field demagnetization experiments, using the principal component analysis of demagnetization data and the analysis of remagnetization circles. Both normal and reverse polarity directions were observed, with the mean direction of the reversely-magnetized lavas (15 sites, D = 189.2˚ , I = 44˚ , α95 = 5.3˚ ) being steeper than and ca. 9˚ of antiparallel from the mean direction of the normal-polarity flows (20 sites, D = 1.1˚ , I = -37.3˚ , α95 = 6.9˚ ). The mean normal and reverse directions yield a negative reversal test that is just significant at the 5% probability level (P = 4.5%). However, when our new data set is combined with previously published paleomagnetic results from Mauritius, the difference between the normal mean direction and the antipode of the reverse mean is not significant at the 5% level, yielding a positive reversal test. The paleomagnetic pole corresponding to the combined polarity data set excluding transitional directions (86.7˚ N, 186.2˚ E, A95 = 3.5˚ , n = 32) is slightly far-sided, but the difference between its position and the

  15. Lava Flow Emplacement Processes and Eruptive Characteristics of the Ontong Java Plateau: Inferences from High-Precision Glass Analysis

    Science.gov (United States)

    Trowbridge, S. R.; Michael, P. J.

    2015-12-01

    High-precision major and volatile element analyses were performed on natural basaltic glass from ODP Leg 192 Sites 1185 and 1187 of the Ontong Java Plateau (OJP) as a way to correlate lava flows within and between ODP drill sites. The ultimate goal is to estimate the dimensions, emplacement style, and eruption characteristics of the high-MgO Kroenke-type lavas: the youngest known flows at the two sites. The 122-Ma Ontong Java Plateau is the largest known magmatic event in Earth's history, yet little is known of the emplacement style (e.g. flow dimensions and durations) of OJP lavas due to its submarine nature and burial beneath hundreds of meters of sediment. Basalt samples were recovered from 110- and 130-m thick core sections from Sites 1185B and 1187A, respectively. Total Kroenke-type lava thickness is 125 m at 1185B and >136 m at 1187. Site 1187A is located 146 km north of Site 1185B and lies ≈50 m shallower than Site 1187. Remarkably, all of the glass compositions from both sites fall on a common liquid line of descent, suggesting that all lavas were the product of a single eruption from a common magma chamber. The range of MgO compositions reflects a 20ºC range in temperature, representing ~1.9% crystallization of olivine + spinel. Using measured phenocryst abundance, we examine whether this crystallization occurred within the magma chamber or during long transport of lavas on the seafloor. More primitive lavas are present in the upper 30 m of Site 1185B (average of ~9.54 wt. % MgO), overlying more fractionated lavas (average of ~9.06 wt. % MgO). Lavas from Site 1187A bridge the gap between the high- and low-MgO groups of 1185B. In contrast to MORB, OJP glasses have no vesicles, suggesting they remained liquid for much longer during flow. Paleoeruption depths calculated from H2O and CO2 contents of glasses show no systematic variation with depth in Core 1185B, and range from ~2130-2650 mbsl, while Site 1187 shows deeper eruption depths of ~2410-3040 mbsl

  16. Finite Element Model of a Two-Phase Non-Newtonian Thixotropic Fluid: Mount St. Helens Lava Dome

    Science.gov (United States)

    Vincent, P.; Zevada, P.

    2011-12-01

    Extrusion of highly viscous lavas that spread laterally and form lava domes in the craters of large volcanoes is associated with significant volcanic hazards. Gas overpressure driven fragmentation of the lava dome or collapse and slumping of marginal sections or the entire mass of the dome can trigger dangerous pyroclastic flows that threaten surrounding populations up to tens of kilometers away. The rate of lava dome growth in the mature state of the dome evolution is often oscillatory. Relatively quiescent episodes are terminated by renewed extrusion and emplacement of exogenous "lobes" or "spines" of lava on the surface of the dome. Emplacement of new lobes is preceded by pressurization of magma in the magmatic conduit that can trigger volcanic eruptions and is preceded by crater floor deformation (e.g. Swanson and Holcombe, 1990). This oscillatory behavior was previously attributed primarily to crystallization kinetics and gas exsolution generating cyclic overpressure build-ups. Analogue modeling of the lava domes has revealed that the oscillatory growth rate can be reproduced by extrusion of isothermal, pseudoplastic and thixotropic plaster of Paris (analogue material for the magma) on a sand layer (analogue material for the unconsolidated deposits of the crater floor). The patterns of dome growth of these models closely correspond to both the 1980-1985 and 2004-2005 growth episodes of Mt. St. Helens lava dome (Swanson and Holcombe, 1990; Major et al., 2005). They also suggest that the oscillatory growth dynamics of the lavas can be explained by the mechanical interaction of the non-Newtonian magma with the frictional and deformable substrate below the lava dome rather than complex crystallization kinetics (e.g. Melnik and Sparks, 1999). In addition, these results suggest that the renewed growth episode of Mt. St. Helens dome in 2006 could be associated with an even higher degree of magma pressurization in the conduit than occurred during the 1980 - 1986

  17. The Sequential Emplacement of the Chaos Crags Dome Complex in Lassen National Park and a Subsequent Avalanche Event Revealing the Internal Structure of a Crystal-Rich Lava Dome

    Science.gov (United States)

    Watts, R. B.; Clynne, M. A.; Sparks, R. S.; Christiansen, R. L.

    2013-12-01

    The Chaos Crags are an aptly named and spectacularly well-preserved nest of 6 crystal-rich rhyodacitic lava domes that lie in the shadow of the renowned Lassen Peak in Lassen National Park, northern California. Each of the domes is composed of a precarious pile of large angular lava blocks indicative of a relatively fast extrusion rate. However, the 2 southernmost domes (i.e. Group 1) exhibit a coulée-like appearance with asymmetric appearance, a thick, glassy basal breccia and distinct concentric flow ridges on the upper surface. The 4 northernmost domes (i.e. Group 2) are notably more dome-like, lacking lateral flow-features and any basal breccia but displaying steeper, blocky flanks and overall low Aspect Ratio. Petrologically, the 2 Groups are very similar in whole-rock composition except there is a distinct difference in the amount of mafic inclusions present - that is ~2 vol% (Group1 domes) and ~10vol% (Group 2 domes). The age of emplacement of the Crags has been previously determined as between 1125 and 375 years B.P (Clynne & Muffler, 1989). Following a period of quiescence, a series of 3 rock-fall avalanches, most likely triggered by a tectonic earthquake, collapsed away from one of the Group 2 domes to produce the 'Jumbles Avalanche' deposit. This impressive deposit (total volume of ~7km2) spilled across the northeastern landscape focused away from the base of Dome C, one of the Group 2 domes. The avalanche events left behind a near-vertical scarp composed of shattered, massive lava riddled with closely-spaced sigmoidal cooling joints to produce a very unstable ~250 meter high and ~300 meter wide metastable structure. On its upper surface, the remnants of a smooth semi-cylindical surface scored with striations is evident. Sampling from this surface and other points away from this surface highlighted the presence of highly fragmented lava with broken jigsaw-style phenocrysts up to one meter away from the smooth surface. Samples taken from a larger

  18. 3D seismic imaging of voluminous earliest Eocene buried lava fields and coastal escarpments off mid-Norway

    Science.gov (United States)

    Planke, Sverre; Millett, John M.; Maharjan, Dwarika; Jerram, Dougal A.; Mansour Abdelmalak, Mohamed

    2017-04-01

    Continental breakup between Greenland and NW Europe in the Paleogene was associated with massive basaltic volcanism, forming kilometer-thick sequences of flood basalts along the conjugate rifted margins. This event was temporarily associated with a warm world, the early Eocene greenhouse, and the short-lived Paleocene-Eocene Thermal Maximum (PETM). A 2500 km2 large industry-standard 3D seismic cube has recently been acquired on the Vøring Marginal High offshore mid-Norway to image sub-basalt sedimentary rocks. This cube also provides a unique opportunity for imaging top- and intra-basalt structures. Detailed seismic geomorphological interpretation of the Top basalt horizon reveal new insight into the late-stage development of the lava flow fields and the kilometer high coastal Vøring Escarpment. Subaerial lava flows with compressional ridges and inflated lava lobes cover the marginal high, with comparable structure and size to modern subaerial lava fields. Pitted surfaces, likely formed by lava emplaced in a wet environment, are present in the western part of the study area near the continent-ocean boundary. The prominent Vøring Escarpment formed when eastward-flowing lava reached the coastline. The escarpment morphology is influenced by pre-existing structural highs, and locally these highs are by-passed by the lava flows which are clearly deflected around them. Volcanogenic debris flows are well-imaged on the escarpment horizon along with large-scale slump blocks. Similar features exist in active volcanic environments, e.g. on the south coast of Hawaii. Numerous post-volcanic extensional faults and incised channels cut both into the marginal high and the escarpment, and show that the area was geologically active after the volcanism ceased. In conclusion, igneous seismic geomorphology and seismic volcanostratigraphy are two very powerful methods to understand the volcanic deposits and development of rifted margins, and the association of major volcanic events

  19. Gas piston activity of the Nyiragongo lava lake: First insights from a Stereographic Time-Lapse Camera system

    Science.gov (United States)

    Smets, Benoît; d'Oreye, Nicolas; Kervyn, Matthieu; Kervyn, François

    2017-10-01

    Nyiragongo volcano (D.R. Congo), in the western branch of the East African Rift System, is one of the most active volcanoes on Earth. Its eruptive activity is mainly characterized by the presence of a persistent lava lake in its main crater. As observed at other persistent lava lakes, the Nyiragongo lava lake level exhibits metric vertical variations in the form of minutes-to hour-long cycles, which we infer to be gas piston activity. To study this activity, we developed and tested a Stereographic Time-Lapse Camera (STLC) system, which takes stereo-pairs of photographs of the Nyiragongo crater at regular intervals. Each pair of gas- and steam-free images during daytime allows the production of a 3D point cloud. The comparison of the point clouds provides a measurement of topographic changes related to variations in lava lake level. The processing of a first dataset acquired between 18 and 20 September 2011, at an acquisition rate of 1 pair of images every 2 min, revealed cycles of vertical lava lake level variations reaching up to 3.8 m. Lava lake level variations >0.5 m are detected significantly. They are interpreted to result from gas accumulation and release in the lava lake itself. The limitations of the STLC approach are related to the number of cameras used and the atmospheric masking by steam and volcanic gas in the Nyiragongo crater. The proposed photogrammetric approach could be applied elsewhere or in other disciplines, where frequent topographic changes occur.

  20. Geometrical Complexity vs. Homogenization Time of Flow Structures Generated by Mixing of Magmas in Lava Flows

    Science.gov (United States)

    Petrelli, M.; Perugini, D.; Poli, G.

    2003-04-01

    Structures produced by mixing of magmas occurring in a lava flow cropping out on the island of Lesbos (Greece) are studied in order to investigate the relationships between the time of homogenization of such structures by chemical diffusion and their geometrical complexity. Several mixing structures having different geometries have been extracted from pictures acquired by a digital camera installed on a petrographical microscope using plane polarized light. All pictures have been acquired utilizing a fixed magnification so that mixing structures have comparable length scales and measure 1.0×1.0 cm^2. Digital images have been converted from color to grayscale and subsequently they have been processed applying a threshold filter to generate binary images in which the mixing structures appear black whereas the image background is white. A number of numerical simulations have been performed to estimate the time required to reach the homogenization of the magma mixing structures by diffusion. The numerical scheme that has been utilized to simulate the diffusion process is a typical finite difference scheme based on the classical binary diffusion protocol. Each black and white image containing mixing structures has been considered as the initial configuration of the magmatic system so that the initial condition of the simulations is determined by the geometry of mixing structures. In order to develop models free from dimensional constraints the simulations have been made dimensionless using a series of scaling factors. The parameter used to quantify the degree of homogenization of mixing structures is the Degree of Homogenization (DH). DH is defined as the ratio between the mean composition of a mixing structure at a given time and the theoretical hybrid composition calculated for the same structure. DH can vary between zero and 1.0; the more DH approaches to 1.0, the more the structures has been homogenized. In order to quantify the geometrical complexity of the mixing

  1. 120 ANNI DI STORIA DELL’ITALIA E DEL VESUVIO NELLA COLLEZIONE DI MEDAGLIE DI LAVA VESUVIANA DELL’OSSERVATORIO VESUVIANO

    OpenAIRE

    De Lucia, M.; Russo, M.; Ricciardi, G. P.

    2011-01-01

    Lava medals constitute a unique example that links Vesuvian eruptions to history, politics and science. Medals coined in the Vesuvius lava date back to the period in which the state of the volcano was characterized by an open conduit, so that warm lava was still used. This state of activity lasted from 1631 to 1944, a period of time during which effusive or effusive-explosive eruptions frequently occurred, followed by very short periods of rest. The medals were realized through...

  2. Nature and extent of lava-flow aquifers beneath Pahute Mesa, Nevada Test Site

    Energy Technology Data Exchange (ETDEWEB)

    Prothro, L.B.; Drellack, S.L. Jr.

    1997-09-01

    Work is currently underway within the Underground Test Area subproject of the US Department of Energy/Nevada Operations Office Environmental Restoration Program to develop corrective action plans in support of the overall corrective action strategy for the Nevada Test Site as established in the Federal Facility Agreement and Consent Order (FFACO, 1996). A closure plan is currently being developed for Pahute Mesa, which has been identified in the FFACO as consisting of the Western and Central Pahute Mesa Corrective Action Units. Part of this effort requires that hydrogeologic data be compiled for inclusion in a regional model that will be used to predict a contaminant boundary for these Corrective Action Units. Hydrogeologic maps have been prepared for use in the model to define the nature and extent of aquifers and confining units that might influence the flow of contaminated groundwater from underground nuclear tests conducted at Pahute Mesa. Much of the groundwater flow beneath Pahute Mesa occurs within lava-flow aquifers. An understanding of the distribution and hydraulic character of these important hydrogeologic units is necessary to accurately model groundwater flow beneath Pahute Mesa. This report summarizes the results of a study by Bechtel Nevada geologists to better define the hydrogeology of lava-flow aquifers at Pahute Mesa. The purpose of this study was twofold: (1) aid in the development of the hydrostratigraphic framework for Pahute Mesa, and (2) provide information on the distribution and hydraulic character of lava-flow aquifers beneath Pahute Mesa for more accurate computer modeling of the Western and Central Pahute Mesa Corrective Action Units.

  3. Primary succession of Hawaiian montane rain forest on a chronosequence of eight lava flows

    Energy Technology Data Exchange (ETDEWEB)

    Kitayama, K.; Mueller-Dombois, D. [Univ. of Hawaii at Manoa, Honolulu, HI, (United States) Dept. of Botany; Vitousek, P.M. [Stanford Univ., Stanford, CA (United States) Dept. of Biological Sciences

    1995-04-01

    The primary-successional sere of a Hawaiian montane rain forest was inferred from an age sequence of eight closely located `a`a flows (clinker type lava); 8, 50, 140, ca. 300, ca. 400, ca. 1400, ca. 3000 and ca.9000 yr, on a windward slope of Mauna Loa, Hawaii. All study sites (0.2 ha each) were at 1120-1250 m a.s.l. with 4000 mm mean annual rainfall. The 400-yr, 1400-yr, and 9000-yr flows had younger volcanic ash deposits, while the others were pure lava. Comparisons of tree size and foliar nutrients suggested that ash increased the availability of nitrogen, and subsequently standing biomass. An Unweighted Pair Group Cluster Analysis on the samples (flows) using quantitative vascular species composition revealed that clusters were correlated with age regardless of the substrate types (pure lava vs. ash), and an indirect ordination on the samples suggested that the sequence of sample scores along axis 1 was perfectly correlated with the age sequence. Although ash deposits increased biomass, they did not affect the sequence of the successional sere. Both pubescent and glabrous varieties of Metrosideros polymorpha (Myrtaceae) dominated upper canopy layers on all flows {>=} 50 yr and {<=} 1400 yr, but the pubescent variety was replaced by the glabrous on the flows {>=} 3000 yr. Lower layers were dominated initially by a mated fern, Dicranopteris linearis, up to 300 yr, and subsequently by tree ferns, Cibotium spp., to 9000 yr. The cover of Cibotium declined sightly after 3000 yr, while other native herb and shrub species increased. 43 refs, 7 figs, 4 tabs

  4. Compositional gradients surrounding spherulites in obsidian and their relationship to spherulite growth and lava cooling

    Science.gov (United States)

    Gardner, James E.; Befus, Kenneth S.; Watkins, James; Hesse, Marc; Miller, Nathan

    2012-10-01

    Spherical masses of crystal fibers (spherulites) crystalize from rhyolitic melt/glass mainly in response to significant undercooling while lava cools. Spherulite growth should induce compositional gradients in the surrounding glass from expulsion of incompatible constituents and diffusion of those constituents away from the spherulite. Finite-difference numerical modeling of one-dimensional diffusion, in which diffusivities are allowed to vary with temperature, is used to investigate how compositional gradients reflect spherulite growth and lava cooling. Overall, three forms of gradients are identified. Elements that diffuse quickly are expelled from the spherulite but then migrate away too quickly to become enriched at the boundary of the spherulite. Elements that diffuse slowly are trapped within the growing spherulite. Between those endmembers are elements that are not trapped, yet diffuse slow enough that they become enriched at the contact. Their slow diffusion away then elevates their concentrations in the surrounding glass. How enriched those elements are at the spherulite-matrix interface and how far their enrichments extend outwards into the glass reflect how spherulites grow and thermal conditions during growth. Concentrations of H2O, Rb, F, Li, Cl, Na, K, Sr, Cs, Ba, and Be were measured in and around spherulites in obsidian from a 4.7 ± 1 km3 rhyolite lava dome erupted from Tequila volcano, Mexico. Measurable concentration gradients are found for H2O, Rb, and F. Attributes of those gradients and the behaviors of the other elements are in accord with their experimentally constrained diffusivities. Spherulites appear to have grown following radial, rather than volumetric, growth. The observed gradients (and lack of others) are more consistent with growth mainly below the glass transition, which would necessitate the dome cooling at ca. 10-5 to 10-7 °C s-1. Such slow cooling is consistent with the relatively large volume of the dome.

  5. Palaeomagnetic secular variation from Holocene lava flows of the Taupo Volcanic Zone (TVZ), New Zealand

    Science.gov (United States)

    Greve, A.; Turner, G. M.; Hodgson, E.; Nilsson, A.; Hill, M. J.

    2014-12-01

    In order to understand the origin, temporal behaviour and spatial characteristics of Earth's magnetic field, global data coverage and high resolution age control are required. Previous studies and modelling approaches contain only little data from the southern hemisphere and in particular the Southwest Pacific. Here we study Holocene records of the direction and intensity of the palaeomagnetic field from volcanic materials sampled within Taupo Volcanic Zone, New Zealand. Altogether we sampled 49 sites on 17 individual basaltic to rhyolitic lava flows of Holocene age. Each individual flow was sampled at a minimum of three sites, allowing a direct comparison of palaeomagnetic and rock magnetic results with location in a lava flow. Estimates of palaeofield directions were obtained from principal component analysis of thermal and alternating field demagnetisation data. Site mean declinations range from 340° (W) to 18° (E) and inclinations range between - 45° and - 85°. The current values in Taupo, New Zealand are: declination 21°, inclination -65°, and intensity 54.5 μT. Successful palaeointensity estimates were obtained from five flows by combining extensive microwave and thermal experiments following Coe and IZZI Thellier-type protocols. Results were accepted on the basis of stringent quality criteria, agreement between different methods and consistency between sites from each lava flow. Palaeointensities range from 29 to 78 μT. The new data shows that the local field had a generally more easterly declination and was of higher intensity than suggested by the CALS series world models (e.g. Korte et al, 2011). The latter are predominantly based on northern hemisphere data and lack a full dataset from New Zealand. The implications of the new data on global and regional field models are discussed.

  6. Contenidos de uranio de lavas recientes en el sector sur de los Andes centrales

    Directory of Open Access Journals (Sweden)

    Guerra, N.

    1984-12-01

    Full Text Available We have studied the distribution of U in modern lava -flows of the southern part from the Central Andes (16°-28° S. For a given SiO2, content of the rocks, U abundance increases from west to east in a transects to the Andean Belt, while the depth of the subduction zone increases and the thickness of the continental curst decreases. Besides, U content tends to inerease steadly with the latitude, while the thick of the continental crust and the depth of the seismic zone decreases southward. Thus, on the basis of the available data, we are in a position to suggest that the U behavior in the studied lavas depends on the alkalanity and magmatic history of each volcanic center.

    Se presenta un estudio de distribución de U en lavas modernas del sector sur de los Andes centrales (16°-28° S. Para rocas de contenidos similares en SiO2 la abundancia de U crece de oeste a este en un perfil transversal al cordón andino, mientras que aumenta la profundidad de subducción, y disminuye la potencia de la corteza continental. Además, mientras la potencia de la corteza continental y la profundidad de la zona sísmica de Benioff disminuyen hacia el sur, U tiende a aumentar con la latitud. Así, y basado en los datos disponibles, estamos en posición de sugerir que el comportamiento de U en las rocas estudiadas, depende de la alcalinidad y de la historia magmática de cada centro volcánico.

  7. Subduction Controls of Hf and Nd Isotopes in Lavas of the Aleutian Island Arc

    Energy Technology Data Exchange (ETDEWEB)

    Yogodzinski, Gene; Vervoort, Jeffery; Brown, Shaun Tyler; Gerseny, Megan

    2010-08-29

    The Hf and Nd isotopic compositions of 71 Quaternary lavas collected from locations along the full length of the Aleutian island arc are used to constrain the sources of Aleutian magmas and to provide insight into the geochemical behavior of Nd and Hf and related elements in the Aleutian subduction-magmatic system. Isotopic compositions of Aleutian lavas fall approximately at the center of, and form a trend parallel to, the terrestrial Hf-Nd isotopic array with {var_epsilon}{sub Hf} of +12.0 to +15.5 and {var_epsilon}{sub Nd} of +6.5 to +10.5. Basalts, andesites, and dacites within volcanic centers or in nearby volcanoes generally all have similar isotopic compositions, indicating that there is little measurable effect of crustal or other lithospheric assimilation within the volcanic plumbing systems of Aleutian volcanoes. Hafnium isotopic compositions have a clear pattern of along-arc increase that is continuous from the eastern-most locations near Cold Bay to Piip Seamount in the western-most part of the arc. This pattern is interpreted to reflect a westward decrease in the subducted sediment component present in Aleutian lavas, reflecting progressively lower rates of subduction westward as well as decreasing availability of trench sediment. Binary bulk mixing models (sediment + peridotite) demonstrate that 1-2% of the Hf in Aleutian lavas is derived from subducted sediment, indicating that Hf is mobilized out of the subducted sediment with an efficiency that is similar to that of Sr, Pb and Nd. Low published solubility for Hf and Nd in aqueous subduction fluids lead us to conclude that these elements are mobilized out of the subducted component and transferred to the mantle wedge as bulk sediment or as a silicate melt. Neodymium isotopes also generally increase from east to west, but the pattern is absent in the eastern third of the arc, where the sediment flux is high and increases from east to west, due to the presence of abundant terrigenous sediment in the

  8. Secular Variation and Paleomagnetic Studies of Southern Patagonian Plateau Lavas, 46S to 52S, Argentina

    Science.gov (United States)

    Brown, L.; Gorring, M.; Mason, D.; Condit, C.; Lillydahl-Schroeder, H.

    2007-12-01

    Regional studies of paleosecular variation of the Earth's magnetic field can provide us with information beyond that available from one location. Southern Patagonia, Argentina (46S to 52S latitude and 68W to 72W longitude) is a place where numerous Plio-Pleistocene lava flows are available for such a study. Volcanic activity in this area is related to back arc volcanism due to slab window activity as the South Chile Ridge is subducted beneath western South America, producing Neogene volcanic centers capping Mesozoic basement extending far to the east of the active plate boundary. Published studies on young lavas from both the northern (Meseta del Lago Buenos Aires, Brown et al, 2004) and southern (Pali Aike Volcanic Field, Mejia et al, 2004) portions provide stable paleomagnetic data on nearly 70 lava flows. Paleosecular variation values for the two studies differ, with 17.1 degrees obtained from the Pali Aike field and 20.0 degrees from the Lago Buenos Aires field. Recent fieldwork in the plateau lavas between these two locations has provided some 80 new sites allowing us to better investigate secular variation and the time-averaged field over this entire region during the past 5 myr. Rock magnetic studies on selected new samples (isothermal remanent magnetization and hysteresis measurements) as well as optical observations indicate low titanium magnetite as the primary carrier of remanence. Hysteresis properties range from 0.1 to 0.4 for Mr/Ms and 1.4 to 3.0 for Hcr/Hc indicating psuedo-single domain behavior. Mean destructive fields for AF demagnetization average 40 to 60 mT. Thirty-three new sites, mostly from Gran Meseta Central (48°S), yield a mean direction of inclination -61.8, declination of 356.6 with an alpha-95 of 5.7 degrees. These directions, with additional sites recently collected from Meseta de la Muerte south to Rio Santa Cruz, will allow us to further investigate paleosecular variation over this wide region.

  9. Burned and buried by the Siberian traps: tree trunks in volcaniclastics and lavas

    Science.gov (United States)

    Polozov, Alexander G.; Planke, Sverre; Svensen, Henrik H.; Jerram, Dougal A.; Looy, Cindy

    2017-04-01

    Major Phanerozoic mass extinctions could be explained by intense volcanic activity related to the formation of Large Igneous Provinces (LIPs). The Siberian Traps LIP possibly caused the most severe mass extinction on the Earth, the end-Permian extinction. This event is documented by global data showing the extinction of floral and faunal species and by stable isotope excursions. Information about the direct impact of the Siberian Traps on the local flora and fauna is scarce. By our knowledge, no detailed description has been done on the faith of trees in Siberia. However, the story of Late Permian giant trees like Cordaites and wood ferns, could shed light on the impact of the onset of the LIP magmatism and the related mass extinction. For the first time we describe that Late Permian tree trunks were buried in volcaniclastic deposits and at the footwall contact of the oldest lava flows of the Siberian Traps, and despite that this phenomenon is known by local geologists it is not well described in the literature. Tree trunks in volcaniclastic deposits were compressed during consolidation of the volcaniclastic material originated from pyroclastic density currents from nearby volcanic centers. Tree petrification is presented by quartz with minor sulphides, zeolite, calcite and sulphates. Tree trunks at the footwall contact of the lava flows have a better preserved year rings structure and late permineralization presented by calcite with minor quartz and sulphides. Our results demonstrate that intensive magmatic activity related with LIP formation affects land vegetation at various grades. Lavas have had a local violent impact, but burned and buried tree trunks have a better preserved structure reflecting single dominated permineralization processes than the tree trunks buried by pyroclastics that have covered extensive areas and followed by trees compression and later multistage permineralization. In a global context, such type of volcanic activity has a variable

  10. The importance of being pillowed: using pillow lava as a paleo-climate proxie in glaciovolcanic settings

    Science.gov (United States)

    Edwards, Ben

    2010-05-01

    Pillow lava may be the most abundant type of lava morphology on Earth throughout most of Earth's history. Pillow presence always implies eruption/emplacement of lava into (1) a medium with a significantly different viscosity than that of the lava, and (2) a medium in which heat can be removed efficiently enough from the lava/medium interface to prevent whole scale physical and chemical homogenization. Although the ‘medium' is most commonly water, pillow-shaped lava can also form by intrusion into wet sediment or even emplacement into cooler, higher viscosity magma. During glaciovolcanic eruptions, pillow lava forms in a variety of different environments including (1) eruptions into water at variable confining pressures (e.g. pillow ridges/mounds), (2) intrusion into unconsolidated volcaniclastic materials (e.g. pepperite and pillowed dike margins), (3) eruption into water-filled, ice-confined tunnels, and (4) flow of subaerial lava into englacial lakes (e.g. pillow lava deltas). Differentiating between different eruption environments can require the use of both field and laboratory techniques. Field observations of pillow mounds/ridges or individual pillows can help distinguish (1) from (3) based on morphologies indicative of large-scale confinement, or shapes of individual pillows (e.g. Skilling 2009). However, differentiating between pillows formed in (1), (3) or (4) can also be difficult based solely on field observations. Dense, non-vesiculated pillows could form by eruptions of ‘wet' magmas at high confining pressures, from eruptions of ‘dry' magmas at a range of confining pressures, or by flow of subaerial, degassed lava into water. Differentiating between these three scenarios may require measurements of volatiles from fresh, pillow rim glass and use of one of a variety of techniques for documenting the heterogeneity and concentrations of volatile species (e.g. Tuffen et al and Owen et al, this session), as well as estimation of volatile saturation

  11. Compositional variation of lavas from a young volcanic field on the Southern Mid-Atlantic Ridge, 8°48'S

    Science.gov (United States)

    Haase, K.; Brandl, P. A.; Melchert, B.; Hauff, F.; Garbe-Schoenberg, C.; Paulick, H.; Kokfelt, T. F.; Devey, C. W.

    2012-12-01

    Volcanic eruptions along the mid-oceanic ridge system are the most abundant signs of volcanic activity on Earth but little is known about the timescales and nature of these processes. The main parameter determining eruption frequency as well as magma composition appears to be the spreading rate of the mid-oceanic ridge. However, few observations on the scale of single lava flows exist from the slow-spreading Mid-Atlantic Ridge so far. Here we present geological observations and geochemical data for the youngest volcanic features of the so-called A2 segment (Bruguier et al., 2003, Hoernle et al., 2011) of the slow-spreading (33 mm/yr) southern Mid-Atlantic Ridge at 8°48'S. This segment has a thickened crust of about 9 km indicating increased melt production in the mantle. Side-scan sonar mapping revealed a young volcanic field with high reflectivity that was probably erupted from two volcanic fissures each of about 3 km length. Small-scale sampling of the young lava field at 8°48'S by ROV and wax corer and geochemical analyses of the volcanic glasses reveal three different compositional lava units along this about 11 km long portion of the ridge. Based on the incompatible element compositions of volcanic glasses (e.g. K/Ti, Ce/Yb) we can distinguish two lava units forming the northern and the larger southern part of the lava field covering areas of about 5 and 9 square kilometres, respectively. Basalts surrounding the lava field and from an apparently old pillow mound within the young flows are more depleted in incompatible elements than glasses from the young volcanic field. Radium disequilibria suggest that most lavas from this volcanic field have ages of 3000 to 5000 yrs whereas the older lavas surrounding the lava field are older than 8000 yrs. Faults and a thin sediment cover on many lavas support the ages and indicate that this part of the Mid-Atlantic Ridge is in a tectonic rather than in a magmatic stage. Lavas from the northern and southern ends of the

  12. Lava fountaining and vent morphology analyzed at the 2014 Holuhraun eruption, Iceland, by video monitoring and topographic mapping

    Science.gov (United States)

    Witt, Tanja; Walter, Thomas R.; Müller, Daniel; Schöpa, Anne; Steinke, Bastian; Gudmundsson, Magnus T.

    2017-04-01

    Fissure eruptions are commonly linked to magma at depth and lava fountaining at the surface. Shortly after the onset of eruptive activity, erupting fissures begin to focus their activity at distinct vents, resulting in the formation of morphological craters shaping the sites of the eruption. A detailed analysis of the morphological development during fissure eruptions and the link to the lava fountain activity has not been conducted in large detail so far. To analyze the lava fountains in height and venting activity and compare that to the vent morphology, we used videos recorded from different locations at a distance up to 2 km during the first few days of the 2014 main Holuhraun eruption, Iceland. The videos have lengths of up to 2 hours and focus on the main eruptive vents. To investigate the morphology of the developing craters after the eruption in detail, a fieldwork mapping project combining terrestrial laser scanning (TLS) and unmanned aerial vehicle (UAV) based aerophoto analysis was realized in summer 2015. From the data, we generated a locally high-resolution digital elevation model by structure from motion (SfM) at the eruptive vents. We found that at the locations of highest venting activity the lava spatters formed craters during the very initial phase of the eruption of 4 days. Comparison to post-eruptive topography shows that the craters remain similar in shape, but increase in size as the eruption progressed. Therefore, the remaining morphology is mostly conditioned in the beginning of the eruption. Furthermore, the smaller craters of Sudri show distinct lava fountains, which are much smaller and thinner than the ones from the bigger Baugur crater. Comparably, the activity of the lava fountains is a little bit lower at Sudri. The Baugur crater is the locus of several high lava fountains, which slightly move in location by up to 20 m and intertwine/overlap each other. This might be due to the presence of the large lava lake at the Baugur crater. In

  13. Small crystals, big implications: glomerocrysts and their connections to large silicic magma reservoirs. Examples from Yellowstone rhyolite lavas.

    Science.gov (United States)

    Girard, G.

    2016-12-01

    Characterizing the nature and physical state of the magma reservoirs associated to large silicic volcanoes is critical to assess their potential to erupt. Yellowstone is among the most active of these systems, having produced 3 caldera-forming eruption sequences and >40 rhyolite lava flows over the last 2.15 Ma. The geochemical evolution of the most recently erupted lava flow sequences, the Upper Basin and Central Plateau members, argues for the existence of one large magma reservoir, from which melts are periodically extracted and erupted as lava with eruptions closely postdating the second and third caldera collapse events, the 1.28 Ma Osborne Butte lava dome, and the 0.6 Ma East Biscuit Basin lava flow. These more phyric units have complex mineralogy with multiple crystal textures and geochemistry. In particular, they exhibit plagioclase-clinopyroxene-oxides glomerocrysts with grain size erupted closely after caldera collapse (when the volcano subsurface is the most disturbed) argue for their origin from the magma body from which only melts normally originate. Subsequent to caldera collapse, magma mobility may be enhanced, allowing for extraction of some crystallized material. These glomerocrysts might thus constitute proxies for the nature of the imaged and presumably long-lived Yellowstone magma reservoir.

  14. Preliminary paragenetic interpretation of the Quaternary topaz rhyolite lava domes of the Blackfoot volcanic field, southeastern Idaho

    Science.gov (United States)

    Lochridge, W. K., Jr.; McCurry, M. O.; Goldsby, R.

    2015-12-01

    The Quaternary topaz rhyolite lava domes of the bimodal, basalt-dominated Blackfoot volcanic field (BVF), SE Idaho occur in three clusters. We refer to these as the China Hat lava dome field (southernmost; ~ 57 ka), and the 1.4 to 1.5 Ma Sheep Island and White Mountain (northernmost) lava dome fields. The rhyolites and surrounding, more voluminous basalt lavas closely resemble coeval Quaternary rocks erupted to the north along the Eastern Snake River Plain segment of the Yellowstone-Snake River Plain volcanic track. However rhyolites in BVF are distinguished by having more evolved Sr- and Nd-isotopic ratios, as well as having phenocryst assemblages that includes hydrous phases (biotite and hornblende), thorite, and vapor-phase topaz. This study seeks to improve our understanding of the unique conditions of magma evolution that led to these differences. We focus on textural features of major and accessory phenocrysts as a basis for inferring paragenesis for rhyolites from the China Hat lava dome field. Preliminary work indicates that there are three sequentially formed populations of textures among magmatic phases: 1. population of anhedral quartz and plagioclase; 2. population of euhedral grains that includes quartz, sandine, plagioclase, biotite, hornblende, Fe-Ti oxides, zircon and apatite; 3. boxy cellular (skeletal?) sanidine and quartz. We speculate that the first population are resorbed antecrysts, the second formed prior to eruption as autocrysts (at or near equilibrium?), and the third formed soon before or during eruption.

  15. Role of viscous dissipation in the dynamics of lava flows with power-law rheology

    Science.gov (United States)

    Piombo, A.; Dragoni, M.

    2011-09-01

    We model a lava flow as a one-dimensional flow of a pseudoplastic fluid with viscous dissipation. The flow is horizontally unbounded and is driven downslope by the gravity force. We consider a power-law constitutive equation and we take into account the temperature dependence of the rheological parameters. Given an effusion rate and an initial temperature at the eruption vent, the flow is assumed to cool down by heat radiation. We calculate the heat produced by viscous dissipation as a function of lava temperature and effusion rate. The cooling rate is calculated as a function of the surface temperature and flow rate. Viscous dissipation reduces the cooling rate by an amount which is independent of flow rate. We evaluate the effect of viscous dissipation on the flow thickness and velocity. The effect of dissipation is to decrease the flow thickness and to increase the flow velocity. The effect on flow thickness is greater for smaller flow rates, while the effect on velocity is greater for larger effusion rates. In principle, the model provides a method for estimating the flow rate from in-field measurements of distances and temperatures.

  16. Influence of topography on lava flow quantification from satellite thermal data

    Science.gov (United States)

    Zakšek, Klemen; Pick, Leonie; Coppola, Diego; Hort, Matthias

    2017-04-01

    Satellite images are an accessible data source for monitoring the heat emission from lava flows during effusive eruptions. Their evaluation regarding the size of a flow and volcanic radiant power (VRP) assists the hazard assessment. VRP is a most important parameter for estimation of lava discharge rate. Thus it is important to correct its value for all possible systematic influences. As several volcanoes have steep slopes, we propose a simple topographic correction of VRP observations. It is based on the corrected size of a pixel area. The proposed correction was first tested in a laboratory experiment, where we simulated a volcanic feature by an electrical heating alloy of 0.5 mm diameter installed on a plywood panel. Two thermographic cameras record images of the artificial heat source in wavebands comparable to those available from satellite data. The influence of the slope was in the laboratory setup reduced by a factor of five. The correction algorithm has been applied also to MODIS data of Etna's 2008-2009 eruption. The time series of corrected results contain significantly less noise than the original data.

  17. Aerodynamics Simulations for the D8 ``Double Bubble'' Aircraft Using the LAVA Unstructured Solver

    Science.gov (United States)

    Ballinger, Sean

    2013-11-01

    The D8 ``double bubble'' is a proposed design for quieter and more efficient domestic passenger aircraft of the Boeing 737 class. It features boundary layer-ingesting engines located under a non-load-bearing π-tail and a lightweight low-sweep wing for flight around Mach 0.7. The D8's wide lifting body is expected to supply 15% of its total lift, while a Boeing 737's fuselage contributes only 8%. The tapering rear of the fuselage is also predicted to experience a negative moment resulting in positive pitch, produce a thicker boundary layer for ingestion by distortion-tolerant engines, and act as a noise shield. To investigate these predictions, unstructured grids generated over a fine surface triangulation using Star-CCM+ are used to model the unpowered D8 with flow conditions mimicking those in the MIT Wright brothers wind tunnel at angles of attack from - 2 to 14 degrees. LAVA, the recently developed Launch Ascent and Vehicle Aerodynamics solver, is used to carry out simulations on an unstructured grid. The results are compared to wind tunnel data, and to data from structured grid simulations using the LAVA, Overflow, and Cart3D solvers. Applied Modeling and Simulation Branch, NASA Advanced Supercomputing Division, funded by New York Space Grant.

  18. Deformation, lava dome evolution, and eruption cyclicity at Merapi volcano, Indonesia

    Science.gov (United States)

    Young, Kirby D.

    Deformation monitoring results are reported here for the period 1988-1998 at Merapi volcano, one of the most active and dangerous volcanoes in Indonesia. Comprehensive databases of various geophysical parameters were concurrently studied and analyzed to 2000, and similar data were subsequently considered during periods of eruption crisis in 2001 and 2006. Of particular emphasis was the study of lava eruption rates based on dome volume estimates and seismic proxies for dome collapse volumes. The detailed study period of deformation includes a major resumption in lava effusion in January 1992 and major dome collapses in November 1994, January 1997, and July 1998. Monitoring techniques employed in the field are of two types. Translational movements were recorded via electronic distance measurements (EDM) on a summit trilateration network, slope distance changes measured to the upper flanks, and other data collected from 1988 to 1995. Tilt changes were detected by a summit and flank network of tilt stations that operated at various times from 1993 to 1998. A major consequence of the deformation results is the documentation of a significant 4-year period of deformation precursory to the 1992 eruption. Cross-crater strain rates accelerated from less than 3 x 10-6/day between 1988 and 1990 to more than 11 x 10-6/day just prior to the January 1992 activity, representing a general, asymmetric extension of the summit during highlevel conduit pressurization. After the vent opened and effusion of lava resumed, strain occurred at a much reduced rate of less than 2 x 10-6/day. The Gendol breach, a pronounced depression formed by the juxtaposition of old lava coulees on the southeast flank, functioned as a major displacement discontinuity. An elevated phase of magma production with respect to the long-term rate for the 20th Century characterized the activity at Merapi volcano, Central Java/Yogyakarta, Indonesia, for the period 1992-2006. Most large (0.2 - 3.4 x 106 m3) dome

  19. Osmium isotope variations accompanying the eruption of a single lava flow field in the Columbia River Flood Basalt Province

    Science.gov (United States)

    Vye-Brown, C.; Gannoun, A.; Barry, T. L.; Self, S.; Burton, K. W.

    2013-04-01

    Geochemical interpretations of continental flood basalts usually assume that individual lava flows represent compositionally homogenous and rapidly erupted products of large well-mixed magma reservoirs. However, inflated pāhoehoe lavas may develop over considerable periods of time and preserve chemical variations that can be temporally linked through flow formation to eruption sequence thus providing an understanding of magma evolution over the timescale of a single eruption. This study presents comprehensive major, trace element and Re-Os isotope data for a single eruption that formed the 2660 km3 Sand Hollow flow field in the Columbia River Basalt Province, USA. Major and trace element variations accompanying flow emplacement (e.g. MgO 3.09-4.55 wt%, Ni 17.5-25.6 ppm) are consistent with fractional crystallisation, but other petrogenetic processes or variable sources cannot be distinguished. However, there is a systematic shift in the initial 187Os/188Os isotope composition of the magma (age corrected to 15.27 Ma), from 0.174 (lava core) to 1.444 (lava crust) within a single 35 m thick sheet lobe. Lava crust values are more radiogenic than any known mantle source, consistent with previous data indicating that neither an enriched reservoir nor the sub-continental lithospheric mantle are likely to have sourced these basalts. Rather, these data indicate that lavas emplaced during the earliest stages of eruption have higher degrees of crustal contamination. These results highlight the limitations of applying chemostratigraphic correlation across continental flood basalt provinces, the use of single data points to define melt sources and magmatic processes, and the dangers of using conventional isochron techniques in such basalt sequences for absolute chronology.

  20. Subduction controls on Miocene back-arc lavas from Sierra de Huantraico and La Matancilla and new 40Ar/39Ar dating from the Mendoza Region, Argentina

    Science.gov (United States)

    Dyhr, Charlotte T.; Holm, Paul M.; Llambías, Eduardo J.; Scherstén, Anders

    2013-10-01

    Back-arc volcanism in the western Argentinian provinces of Mendoza and Neuquén has been widespread from the Miocene to historic times. We present a detailed investigation of profiles through two of the major Miocene volcanic areas of the region, the neighboring Huantraico and La Matancilla plateaus, including new 40Ar/39Ar age results of major and trace elements as well as Nd, Sr and Pb isotopic data. Four million years of eruptions from 24.4 ± 0.3 Ma (2σ) of alkali olivine basalts with OIB-type incompatible trace element enrichments at La Matancilla (~ 36.50°S) provide evidence for the presence of back-arc mantle devoid of subduction-related components. In contrast, the lower Huantraico lavas (~ 37.30°S) require an atypical back-arc mantle, almost devoid of arc-like components (e.g. low La/Ta = 15-18 and Ba/La = 12-18), but with a more depleted isotopic signature (e.g. 87Sr/86Sr, 0.7033-0.7037) than observed elsewhere in the Andean back-arc. The Lower to Upper Series development in the Huantraico sequence represents a gradual change from basaltic to trachyandesitic back-arc lavas with a weak but temporally increasing arc geochemical signature (e.g. La/Ta = 15-21; Ba/La = 12-45), which is accompanied by Sr, Nd and Pb isotopic compositions approaching present day values of the Andes arc. The compositional change is accompanied by a gradually decreasing role for garnet in the mantle source, a decreasing degree of melting, but also simultaneously increasing influence from subducted fluids, probably as the slab geometry changes through time. The volcanism at Huantraico ceased when a flat slab was established around 15 Ma.

  1. Protein expression and genetic structure of the coral Porites lobata in an environmentally extreme Samoan back reef: Does host genotype limit phenotypic plasticity?

    Science.gov (United States)

    Barshis, D.J.; Stillman, J.H.; Gates, R.D.; Toonen, R.J.; Smith, L.W.; Birkeland, C.

    2010-01-01

    The degree to which coral reef ecosystems will be impacted by global climate change depends on regional and local differences in corals' susceptibility and resilience to environmental stressors. Here, we present data from a reciprocal transplant experiment using the common reef building coral Porites lobata between a highly fluctuating back reef environment that reaches stressful daily extremes, and a more stable, neighbouring forereef. Protein biomarker analyses assessing physiological contributions to stress resistance showed evidence for both fixed and environmental influence on biomarker response. Fixed influences were strongest for ubiquitin-conjugated proteins with consistently higher levels found in back reef source colonies both pre and post-transplant when compared with their forereef conspecifics. Additionally, genetic comparisons of back reef and forereef populations revealed significant population structure of both the nuclear ribosomal and mitochondrial genomes of the coral host (FST = 0.146 P environmental conditions. This result is important in understanding genotypic and environmental interactions in the coral algal symbiosis and how corals may respond to future environmental changes. ?? 2010 Blackwell Publishing Ltd.

  2. An evaluation of the influence of the experimental cooling rate along with other thermomagnetic effects to explain anomalously low paleointensities obtained for historic lavas of Mt. Etna (Italy)

    NARCIS (Netherlands)

    de Groot, L.V.; Mullender, T.A.T.; Dekkers, M.J.

    2013-01-01

    Methodological aspects in obtaining reliable absolute palaeointensity estimates have attracted renewed attention in recent years. Obtaining a reliable palaeointensity from lavas, however, still is notoriously difficult: in many cases lavas have been shown to be a non-ideal recorder of the

  3. Crystallization history of Kilauea Iki lava lake as seen in drill core recovered in 1967-1979

    Science.gov (United States)

    Helz, R. T.

    1980-12-01

    Kilauea Iki lava lake formed during the 1959 summit eruption, one of the most picritic eruptions of Kilauea Volcano in the twentieth century. Since 1959 the 110 to 122 m thick lake has cooled slowly, developing steadily thickening upper and lower crusts, with a lens of more molten lava in between. Recent coring dates, with maximum depths reached in the center of the lake, are: 1967 (26.5 m). 1975 (44.2 m), 1976 (46.0 m) and 1979 (52.7 m). These depths define the base of the upper crust at the time of drilling. The bulk of the core consists of a gray, olivine-phyric basalt matrix, which locally contains coarser-grained diabasic segregation veins. The most important megascopic variation in the matrix rock is its variation in olivine content. The upper 15 m of crust is very olivine-rich. Abundance and average size of olivine decrease irregularly downward to 23 m; between 23 and 40 m the rock contains 5-10% of small olivine phenocrysts. Below 40 m. olivine content and average grainsize rise sharply. Olivine contents remain high (20-45%, by volume) throughout the lower crust, except for a narrow (contact. Petrographically the olivine phenocrysts in Kilauea Iki can be divided into two types. Type 1 phenocrysts are large (1-12 mm long), with irregular blocky outlines, and often contain kink bands. Type 2 crystals are relatively small (0.5-2 mm in length), euhedral and undeformed. The variations in olivine content of the matrix rock are almost entirely variations in the amount of type 1 olivines. Sharp mineral layering of any sort is rare in Kilauea Iki. However, the depth range 41-52 m is marked by the frequent occurrence of steeply dipping (70°-90°) bands or bodies of slightly vuggy olivine-rich rock locally capped with a small cupola of segregation-vein material. In thin section there is clear evidence for relative movement of melt and crystals within these structures. The segregation veins occur only in the upper crust. The most widely distributed (occurring from 4

  4. The Summer 1997 Eruption at Pillan Patera on Io: Implications for Ultrabasic Lava Flow Emplacement

    Science.gov (United States)

    Williams, David A.; Davies, Ashley G.; Keszthelyi, Laszlo P.; Greeley, Ronald

    2001-01-01

    Galileo data and numerical modeling were used to investigate the summer 1977 eruption at Pillan Patera on Io. This event, now defined as "Pillanian" eruption style, included a high-temperature (greater than 1600 C), possible ultrabasic , 140-km-high plume eruption that deposited dark, orthopyroxene-rich pyroclastic material over greater than 125,000 sq km, followed by emplacement of dark flow-like material over greater than 3100 sq km to the north of the caldera. We estimate that the high-temperature, energetic episode of this eruption had a duration of 52 - 167 days between May and September 1997, with peak eruption temperatures around June 28, 1997. Galileo 20 m/pixel images of part of the Pillan flow field show a wide-spread, rough, pitted surface that is unlike any flow surface we have seen before. We suggest that this surface may have resulted from: 1. A fractured lava crust formed during rapid, low-viscosity lava surging, perhaps including turbulent flow emplacement. 2. Disruption of the lava flow by explosive interaction with a volatile-rich substrate. or 3. A combination of 1 and 2 with or without accumulation of pyroclastic material on the surface. Well-developed flow lobes are observed, suggesting that this is a relatively distant part of the flow field.Shadow measurements at flow margins indicate a thickness of-8 - 10 m. We have modeled the emplacement of putative ultrabasic flow from the summer 1997 Pillan eruption using constraints from new Galileo data. Results suggest that either laminar sheet flows or turbulent channelized flows could have traveled 50 - 150 km on a flat, unobstructed surface, which is consistent with the estimated length of the Pillan flow field (approx. 60 km). Our modeling suggests low thermal erosion rates (less than 4.1 m/d), and that the formation of deep (greater than 20 m) erosion channels was unlikely, especially distal to the source. We calculate a volumetric flow rate of approx. 2 - 7 x 10(exp 3)cu m/s, which is greater

  5. High-resolution AUV mapping and lava flow ages at Axial Seamount

    Science.gov (United States)

    Clague, D. A.; Paduan, J. B.; Dreyer, B. M.; Caress, D. W.; Martin, J.

    2011-12-01

    Mapping along mid-ocean ridges, as on land, requires identification of flow boundaries and sequence, and ages of some flows to understand eruption history. Multibeam sonars on autonomous underwater vehicles (AUV) now generate 1-m resolution maps that resolve lava pillars, internal flow structures and boundaries, and lava flow emplacement sequences using crosscutting relations and abundance of fissures. MBARI has now mapped the summit caldera floor and rims and the upper south rift zone on Axial Seamount on the Juan de Fuca Ridge. With the advent of the high-resolution bathymetry and the ability to observe flow contacts to determine superposition using ROVs and submersibles, the missing component has been determining absolute ages of the flows. We used the MBARI ROV Doc Ricketts to collect short push cores (Six ages from the lowermost part of the south rift of Axial Seamount include samples on a cone with deep summit crater that is ~16,580 aBP and on 5 flows between 950 and 1510 aBP. Two additional flows from the southeast rim of the caldera are 905 and 2005 aBP. An age of 6910 aBP from 15 cm depth in a 2-m volcaniclastic unit on top of a pre-caldera flow on the eastern rim of the caldera suggests formation of the caldera several tens of thousands aBP. Seven ages on at least 5 flows on the floor of Axial caldera range from 620 to 1145 aBP, whereas 10 extensive mapped flows are all inferred to be <620 aBP as they are covered by sediment too thin to sample. The older pillow flows are difficult to map as discrete flows. In contrast, the 11 flows erupted during the last 620 years have an eruption frequency of 55 years. Of these, 6 not significantly overlapped by younger flows have a combined surface area of 30.2 km2 and represent roughly the output over 275 years of eruptive activity in the caldera at Axial Seamount, although they were not erupted in a continuous 275 year timespan. If we use average flow thicknesses of 3-5 m for these sheet flows, we estimate a lava

  6. Rheology and thermal budget of lunar basalts: an experimental study and its implications for rille formation of non-Newtonian lavas on the Moon

    Science.gov (United States)

    Sehlke, A.; Whittington, A. G.

    2015-12-01

    Sinuous lava channels are a characteristic feature observed on the Moon. Their formation is assumed to be due to a combination of mechanical and thermal erosion of the lava into the substrate during emplacement as surface channels, or due to collapsed subsurface lava tubes after the lava has evacuated. The viscosity (η) of the lava plays an important role, because it controls the volume flux of the emplaced lava that governs the mechanical and thermal erosion potential of the lava flow. Thermal properties, such as heat capacity (Cp) and latent heat of crystallization (ΔHcryst) are important parameters in order for the substrate to melt and causing thermal buffering during crystallization of the flowing lava. We experimentally studied the rheological evolution of analog lavas representing the KREEP terrain and high-Ti mare basalts during cooling and crystallization. We find that the two lavas behave very differently. High-Ti mare lava begins to crystallize around 1300 ºC with a viscosity of 8.6±0.6 Pa s and crystal content around 2 vol%. On cooling to 1169 ºC, the effective viscosity of the crystal-melt suspension is increased to only 538±33 Pa s (at a strain rate of 1 s-1) due to crystallization of 14±1 vol% blocky magnetite and acicular ulvöspinel-rich magnetite. The flow behavior of these suspensions depends on the strain rate, where flow curves below strain rates of 10 s-1show shear-thinning character, but resemble Bingham behavior at greater strain rates. In contrast, the KREEP lava crystallizes rapidly over a narrow temperature interval of ~ 30 degrees. The first crystals detected were ulvospinel-rich magnetites at 1204 ºC with ~2 vol% and a viscosity of 90±2 Pa s. On cooling to 1178 ºC, anorthite and enstatite appears, so that the crystal-melt suspension has become strongly pseudoplastic at a crystal content of 22±2 vol% with a flow index (n) of 0.63 and an effective viscosity of 1600±222 Pa s at a strain rate of 1 s-1. We are currently measuring

  7. Dynamics and viscosity of `a'a and pahoehoe lava flows of the 2012-2013 eruption of Tolbachik volcano, Kamchatka (Russia)

    Science.gov (United States)

    Belousov, Alexander; Belousova, Marina

    2018-01-01

    The 2012-2013 flank eruption of Tolbachik volcano (Kamchatka) lasted 9 months and produced 0.54 km3 of basaltic trachyandesite lava, thus becoming one of the most voluminous historical lava effusions of basic composition in subduction-related environments globally. From March to July 2013, the volcano monotonously erupted lava of constant composition (SiO2 = 52 wt%) with a nearly stable effusion rate of 18 m3/s. Despite the uniform eruptive and emplacement conditions, the dominant style of lava propagation throughout that time gradually changed from `a'a to pahoehoe. We report results of instrumental field measurements of the `a'a and pahoehoe flow dynamics (documented with time-lapse cameras) as well as the lava viscosity determined by flow rate and shear stress (using penetrometer) methods. Maximal propagation velocities of the `a'a fronts ranged from 2 to 25 mm/s, and those of the pahoehoe from 0.5 to 6 mm/s. The flow front velocities of both lava types experienced short-period fluctuations that were caused by complex flow mechanics of the advancing flow lobes. Minimal viscosities of lava of the `a'a lobes ranged from 1.3 × 105 to 3.3 × 107 Pa s (flow rate method), and those of the pahoehoe from to 5 × 103 to 5 × 104 Pa s (shear stress method). Our data include the first ever measured profiles of viscosity through the entire thickness of actively advancing pahoehoe lava lobes. We have found that both the `a'a and pahoehoe flows were fed by identical parental lava, which then developed contrasting rheological properties, owing to differences in the process of lava transport over the ground surface. The observed transition from the dominant `a'a to the dominant pahoehoe propagation styles occurred due to gradual elongation and branching of the lava tube system throughout the course of the eruption. Such evolution became possible because the growing lava field, composed of semisolidified flows, provided an environment for shallow subsurface intrusions and

  8. Sedimentary input into the source of Martinique lavas: a Li perspective

    Science.gov (United States)

    Tang, M.; Chauvel, C.; Rudnick, R. L.

    2013-12-01

    The Lesser Antilles arc is known for the prominent continental crustal signatures in its lavas. It thus provides an ideal target for studying crustal recycling in subduction zones. Martinique Island, located in the middle of the Lesser Antilles arc, has been well characterized for its elemental and radiogenic isotope geochemistry (Labanieh et al., 2012). We measured Li isotopes in the Martinique lavas as well as sediments cored at the southern (Site 144) and northern part (Site 543) of the subducting slab. The sediments show a large isotopic variation (δ7Li ~ -4.2‰ to +3.2‰) but the average δ7Li of -1.1 × 2.4‰ (1 σ, n = 15) is significantly lower than that of N-MORB (δ7Li = + 3.4 × 0.7‰, 1 σ, Tomascak et al., 2008), reflecting the influence of chemical weathering in the continental provenance. Although the subducting sediments display marked mineralogical and chemical shifts from south to north due to different deposition distances to the continental platform (Carpentier et al., 2009), their average Li isotopic compositions are indiscernible from each other. With a few exceptions, the Li isotopic compositions of the Martinique lavas are systematically lighter than MORB, giving an average δ7Li of 1.6 × 1.4‰ (1 σ, n = 25, 4 exceptions excluded). The δ7Li values show no correlation with any radiogenic isotope ratios (206Pb/204Pb, 87Sr/86Sr, 143Nd/144Nd and 176Hf/177Hf), Li/Y ratio, La/Sm ratio and SiO2 content. Therefore, the light Li isotopic composition likely reflects the source characteristics rather than contamination within the arc crust. Incorporation of the isotopically light sediments from Site 144 and 543 in the source may explain the depletion of 7Li in the Martinique lavas. A two-end-member mixing model requires 2-5% addition of the sediments into the depleted mantle source, compared with 1-10% sediments constrained by radiogenic isotopes (Carpentier et al., 2008). References Carpentier, M., Chauvel, C., & Mattielli, N., 2008. Pb

  9. Flow dynamics of dacite lava flow - AMS, microstructure and porosity case study

    Science.gov (United States)

    Závada, Prokop; Kusbach, Vladimír; Machek, Matěj; Staněk, Martin; Špičák, Aleš

    2017-04-01

    Pyroclastic flows derived from flow frontal collapse of highly viscous "block lavas" formed by andesite or dacite belong to the most serious volcano-related hazards for surrounding populations. The threat results from abrupt transition of lava flow from ductile flow to gravitational failure of the front, which exposes their overpressurized interior and triggers devastating pyroclastic flows. The goal of the study is to quantify the microfabrics and dynamic porosity in a lava flow to constrain the cavitation process (development and coalescence of dynamic porosity). Pleistocene dacite flow body situated on the slope of Middle Sister Volcano (OR, USA) was studied by means of field-based structural analysis, anisotropy of magnetic susceptibility (AMS), microstructural analysis and mercury injection porosimetry (MIP). The 500 m exposure of the flow is associated with a vertical feeding dyke at the beginning of the flow, 40 m upslope. The flow shows occasional layers, 5-15 cm thick, marked by evenly spaced and up to 10 cm long, lenticular to sigmoidal cracks often developed in the vicinity of the clasts/phenocrysts. These cracks frequently dip against the slope of the flow and show 15-50° difference with the layering. At the feeding dyke, highly oblate magnetic fabric shows subvertical foliations with horizontal lineations oriented parallel to the dyke walls. Middle part of the flow revealed highly prolate fabrics with subhorizontal magnetic foliations and lineations parallel to the flow direction. At the downslope limit of the flow, magnetic foliations are perpendicular to the flow direction. The dynamic porosity was studied in detail on larger sample from the central part of the flow. The sample contains three layers with different density of porosity and average crack length. All the cracks were oriented about 45° to the layer boundaries and alignment of the groundmass crystals. MIP data revealed total connected porosities between 11 and 15 %. Throat

  10. Paleomagnetism and geochronology from the Lunayyir and Khaybar lava fields, Saudi Arabia

    Science.gov (United States)

    Vigliotti, Luigi; Cai, Yue; Rasul, Najeeb M. A.; Ligi, Marco

    2017-04-01

    The Arabian Peninsula was one of the first plates to be investigated using paleomagnetic data (Irving & Tarling, 1961). However, very few additional results appeared in the literature since then and the available information are far from sufficient to explain the tectonics of the Red Sea region. In order to better constrain the tectonic history of the Arabian craton in the Tertiary, we carried out a combined paleomagnetic and Ar/Ar geochronological study on volcanic rocks from the Khaybar and Lunayyir Harrats (lava fields) plus a site of sediments deposited below the Miocene rocks in the former area. 86 hand-oriented samples were collected from 17 sites and progressive thermal or alternating field demagnetization isolated stable characteristic magnetizations (ChRM) that are consistent with a primary magnetization only in the Late Quaternary lava flows from the Lunayyir. Whole rock 39Ar/40Ar step-heating analyses yield whole-rock plateau ages of 12.8 to 16.3 Ma for four alkaline lava flows from Khaybar area, which is consistent with the estimated age range of the region-wide late Cenozoic alkaline volcanism in western Saudi Arabia. The paleomagnetic data from the rocks collected in this region appear to be affected by lightning and weathering and no significant tectonic/plate movement can be inferred from the obtained results. The direction of the high coercivity chemical remanent magnetization (CRM) isolated after thermal cleaning from the Pre-Miocene siltstones (D=169.6°, I=-44.8°; α95=5.4°) is consistent with the existing paleomagnetic results. The associated VGP (314.4°E, 80.6°N, A95=6.8°) is close to the Pliocene VGP of the Arabian Plate and CCW rotated (R=14.86°±6.38°) with respect to the Oligocene African VGP. The Lunayyir paleomagnetic data set of 11 Quaternary lava flows (D=0.31°, I=36.9°, α95=10.5) is statistically indistinguishable from the present field and the virtual geomagnetic poles (VGP: 214.1°E, 85.1°N; A95=12.3°) indicate a

  11. Primeros registros de Tarentola mauritanica (L. 1758 para el centro y norte de Álava

    Directory of Open Access Journals (Sweden)

    Conrado Tejado, María E. Potes.

    2011-01-01

    Full Text Available Se aportan los primeros registros de Tarentola mauritanica (L. 1758 para la provincia de Álava, recopilados entre los años 2006 y 2009. Todos ellos corresponden a observaciones de ejemplares aislados localizados en medios muy humanizados (muros en las proximidades de estaciones ferroviarias, edificios urbanos o ejemplares atropellados en carretera. La especie fue citada en el año 2000 en el Valle del Ebro, en el límite meridional alavés. Las citas en el centro y norte de la provincia (Llanada alavesa y Amurrio, en zonas que soportan inviernos fríos y climas lluviosos atlánticos, suponen un significativo ascenso latitudinal experimentado por la especie en las últimas décadas.

  12. Cooling and crystallization of rhyolite-obsidian lava: Insights from micron-scale projections on plagioclase microlites

    Science.gov (United States)

    Sano, Kyohei; Toramaru, Atsushi

    2017-07-01

    To reveal the cooling process of a rhyolite-obsidian flow, we studied the morphology of plagioclase microlites in the Tokachi-Ishizawa lava of Shirataki, northern Hokkaido, Japan, where the structure of the lava can be observed from obsidian at the base of the flow to the innermost rhyolite. Needle-like micron-scale textures, known as ;projections;, occur on the short side surfaces of the plagioclase microlites. Using FE-SEM we discovered a positive correlation between the lengths and spacings of these projections. On the basis of the instability theory of an interface between melt and crystal, and to understand the length and spacing data, we developed a model that explains the positive correlation and allows us to simultaneously estimate growth rates and growth times. Applying the model to our morphological data and the estimated growth rates and growth times, we suggest that the characteristics of the projections reflect the degree of undercooling, which in turn correlates with lava structure (the obsidian at the margin of the flow experienced a higher degree of undercooling than the interior rhyolite). The newly developed method provides insights into the degree of undercooling during the final stages of crystallization of a rhyolitic lava flow.

  13. Calc-alkaline lavas from the volcanic complex of Santorini, Aegean Sea, Greece : a petrological, geochemical and stratigraphic study

    NARCIS (Netherlands)

    Huijsmans, J.P.P.

    1985-01-01

    This thesis presents the results of a petrological-geochemical- and stratigraphic study of the calc-alkaline lavas from Santorini, Aegean Sea, Greece. The volcanic complex of Santorini consists of seven eruption centres, of which some have been active contemporaneous. The eruption centres in the

  14. PyFLOWGO: An open-source platform for simulation of channelized lava thermo-rheological properties

    Science.gov (United States)

    Chevrel, Magdalena Oryaëlle; Labroquère, Jérémie; Harris, Andrew J. L.; Rowland, Scott K.

    2018-02-01

    Lava flow advance can be modeled through tracking the evolution of the thermo-rheological properties of a control volume of lava as it cools and crystallizes. An example of such a model was conceived by Harris and Rowland (2001) who developed a 1-D model, FLOWGO, in which the velocity of a control volume flowing down a channel depends on rheological properties computed following the thermal path estimated via a heat balance box model. We provide here an updated version of FLOWGO written in Python that is an open-source, modern and flexible language. Our software, named PyFLOWGO, allows selection of heat fluxes and rheological models of the user's choice to simulate the thermo-rheological evolution of the lava control volume. We describe its architecture which offers more flexibility while reducing the risk of making error when changing models in comparison to the previous FLOWGO version. Three cases are tested using actual data from channel-fed lava flow systems and results are discussed in terms of model validation and convergence. PyFLOWGO is open-source and packaged in a Python library to be imported and reused in any Python program (https://github.com/pyflowgo/pyflowgo)

  15. Field-based description of rhyolite lava flows of the Calico Hills Formation, Nevada National Security Site, Nevada

    Science.gov (United States)

    Sweetkind, Donald S.; Bova, Shiera C.

    2015-01-01

    Contaminants introduced into the subsurface of Pahute Mesa, Nevada National Security Site, by underground nuclear testing are of concern to the U.S. Department of Energy and regulators responsible for protecting human health and safety. The potential for contaminant movement away from the underground test areas at Pahute Mesa and into the accessible environment is greatest by groundwater transport through fractured volcanic rocks. The 12.9 Ma (mega-annums, million years) Calico Hills Formation, which consists of a mixture of rhyolite lava flows and intercalated nonwelded and bedded tuff and pyroclastic flow deposits, occurs in two areas of the Nevada National Security Site. One area is north of the Rainier Mesa caldera, buried beneath Pahute Mesa, and serves as a heterogeneous volcanic-rock aquifer but is only available to study through drilling and is not described in this report. A second accumulation of the formation is south of the Rainier Mesa caldera and is exposed in outcrop along the western boundary of the Nevada National Security Site at the Calico Hills near Yucca Mountain. These outcrops expose in three dimensions an interlayered sequence of tuff and lava flows similar to those intercepted in the subsurface beneath Pahute Mesa. Field description and geologic mapping of these exposures described lithostratigraphic variations within lava flows and assisted in, or at least corroborated, conceptualization of the rhyolite lava-bearing parts of the formation.

  16. Eusarsiella bedoyai (Myodocopida, Sarsiellidae), a new ostracode species from a marine lava cave in the Canary Islands

    NARCIS (Netherlands)

    Baltanás, Angel

    1992-01-01

    A new species of the ostracode genus Eusarsiella (Myodocopida, Sarsiellidae) is described from a marine lava tube in Lanzarote (Canary Islands) and compared with other species known to occur in the same geographical area. Eusarsiella bedoyai n. sp. is the second species in that genus described from

  17. LAVA Subsystem Integration and Testing for the RESOLVE Payload of the Resource Prospector Mission: Mass Spectrometers and Gas Chromatography

    Science.gov (United States)

    Coan, Mary R.; Stewart, Elaine M.

    2015-01-01

    The Regolith and Environment Science & Oxygen and Lunar Volatile Extraction (RESOLVE) payload is part of Resource Prospector (RP) along with a rover and a lander that are expected to launch in 2020. RP will identify volatile elements that may be combined and collected to be used for fuel, air, and water in order to enable deeper space exploration. The Resource Prospector mission is a key part of In-Situ Resource Utilization (ISRU). The demand for this method of utilizing resources at the site of exploration is increasing due to the cost of resupply missions and deep space exploration goals. The RESOLVE payload includes the Lunar Advanced Volatile Analysis (LAVA) subsystem. The main instrument used to identify the volatiles evolved from the lunar regolith is the Gas Chromatograph-Mass Spectrometer (GC-MS). LAVA analyzes the volatiles emitted from the Oxygen and Volatile Extraction Node (OVEN) Subsystem. The objective of OVEN is to obtain, weigh, heat and transfer evolved gases to LAVA through the connection between the two subsystems called the LOVEN line. This paper highlights the work completed during a ten week internship that involved the integration, testing, data analysis, and procedure documentation of two candidate mass spectrometers for the LAVA subsystem in order to aid in determining which model to use for flight. Additionally, the examination of data from the integrated Resource Prospector '15 (RP' 15) field test will be presented in order to characterize the amount of water detected from water doped regolith samples.

  18. 3-päevane üliõpilastöö - "Roheline lava" = 3-day student project - "Green stage"

    Index Scriptorium Estoniae

    2008-01-01

    Tutvustatakse Tallinna Tehnikakõrgkooli Arhitektuuri õppetooli õpitoa "Intelligentsed konstruktsioonid" raames 4. kursuse arhitektuuri ja ehituse eriala üliõpilaste kavandatud 11 "Rohelise lava" lahendust Tallinna lauluväljaku maa-alale. Üliõpilasi juhendasid Irina Raud ja Stefan Polonyi (Saksamaa)

  19. Determination of trace elements in volcanic rock samples collected from cenozoic lava eruption sites using LIBS.

    Science.gov (United States)

    Gondal, Mohammed A; Nasr, Mohamed M; Ahmed, Zulfiqar; Yamani, Zain H

    2009-04-01

    Trace elements of environmental significance present in the volcanic rock samples collected from sites of the Cenozoic era flood basalt flows and eruptions were detected using locally developed laser-induced breakdown spectrometer. For spectro-chemical analysis of these samples, the plasma was generated by focusing a pulsed Nd: YAG laser radiation at 1064 nm wavelength on the target rock samples. These samples were collected from four widely separated locations surrounding the volcanic eruption sites belonging to the Harrat Hutaymah volcanic field in the vicinity of Taba town, situated to the east of Hail city of northern Saudi Arabia. These samples represent the scoria basalt lava flows as well as a large tuff-ring crater and it contains xenoliths. These flows occur widespread over the Earth's surface in this region, and their contained xenoliths are brought up from depths of a few tens of kilometers. This volcanic field has received much less attention in the previous geological studies; and consequently, its effects on the environment are not well defined. The concentration of different elements of environmental significance like Cr, Pb, Mn, Cd, Sr and other trace metals like Cu, Al, Ca, Mg, Zn, Ti and Fe in these rock samples were determined by spectral analysis. Parametric dependence for improvement of LIBS sensitivity for detection of these elements was also carried out. The highest concentration detected of environmentally significant elements like Cr, Mn, Pb, Sr and Ni are 1910, 1399, 90.5, 12412 and 461.5 ppm, respectively in four different lava samples which are considered to be much higher than the safe permissible limits. The LIBS results were compared with the results obtained using other analytical techniques such as the inductively coupled plasma atomic emission spectroscopy (ICP-AES).

  20. Fragmentation mechanisms associated with explosive lava-water interactions in a lacustrine environment

    Science.gov (United States)

    Fitch, Erin P.; Fagents, Sarah A.; Thordarson, Thorvaldur; Hamilton, Christopher W.

    2017-01-01

    Rootless cones form when partially outgassed lava interacts explosively with external water. The explosions represent an end-member system that can elucidate mechanisms of explosive magma-water interactions in the absence of magmatic fragmentation induced by outgassing. The proportion of finely fragmented ejecta (i.e., ash), generated in rootless explosions, may contribute significantly to the energy of the explosion even if the ash volume is small relative to coarser ejecta. Laboratory experiments indicate that the degree of melt-water mixing and energy release are proportional to the abundance of blocky grains, fragmented by brittle disintegration, which effectively contribute thermal energy to the system. To constrain the mechanisms and dynamics of rootless explosive activity, we assess the nature and modes of fragmentation and ejecta characteristics through morphological, textural, and density analysis of rootless tephra associated with a pāhoehoe lava flow in a lacustrine (lake basin) environment. We observe strong correlations between the mean grain size and the mass percentage of both blocky (negative power law trend) and fluidal (positive logarithmic) tephra clasts of all sizes. We interpret these trends as scale-dependent fragmentation behavior due to the decreasing efficacy of hydrodynamic fragmentation as it occurs over finer scales, especially over the ash size range. Additionally, all analyzed beds contain fine ash-sized blocky and mossy clasts, which are thought to be diagnostic of a high transfer rate of thermal to mechanical energy, characteristic of molten fuel-coolant interactions. These results agree with a recent model of rootless cone formation, prior fragmentation theory, and scaled laboratory experiments and therefore provide a field-based analog for future experimental and modeling efforts.

  1. Transitions in Lava Emplacement Recorded in the Deccan Traps Sequence (India)

    Science.gov (United States)

    Vanderkluysen, L.; Self, S.; Jay, A. E.; Sheth, H. C.; Clarke, A. B.

    2015-12-01

    Transitions in the style of lava flow emplacement are recognized in the stratigraphic sequence of several mafic large igneous provinces (LIPs), including the Etendeka (Namibia), the Faeroe Islands (North Atlantic LIP), the Ethiopian Traps, and the Deccan Traps (India). These transitions, from units dominated by meter-sized pāhoehoe toes and lobes to those dominated by inflated sheet lobes tens to hundreds of meters in width and meters to tens of meters in height, seems to be a fundamental feature of LIP emplacement. In the Deccan, this volcanological transition is thought to coincide with deeper changes to the volcano-magmatic system expressed, notably, in the trace element and isotopic signature of erupted flows. We investigated this transition in the Deccan Traps by logging eight sequences along the Western Ghats, an escarpment in western India where the Deccan province is thickest and best exposed. The Deccan province, which once covered ~1 million km2 of west-central India, is subdivided in eleven chemo-stratigraphic formations in the type sections of the Western Ghats. Where the lower Deccan formations are exposed, we found that as much as 65% of the exposed thickness (below the Khandala Formation) is made up of sheet lobes, from 40% in the Bhimashankar Formation to 75% in the Thakurvadi Formation. Near the bottom of the sequence, 25% of the Neral Formation is composed of sheet lobes ≥15 m in thickness. On this basis, the traditional view that inflated sheet lobes are an exclusive feature of the upper part of the stratigraphy must be challenged. Several mechanisms have been proposed to explain the development of compound flows and inflated sheet lobes, involving one or more of the following factors: underlying slope, varying effusion rate, and source geometry. Analogue experiments are currently under way to test the relative influence of each of these factors in the development of different lava flow morphologies in LIPs.

  2. Paleomagnetic study of an historical lava flow from the Llaima volcano, Chile

    Science.gov (United States)

    Di Chiara, A.; Moncinhatto, T.; Hernandez Moreno, C.; Pavón-Carrasco, F. J.; Trindade, R. I. F.

    2017-08-01

    The understanding of the paleosecular variations (PSV) of the geomagnetic field in South America is still biased by the scarcity of data. Especially, the recent geomagnetic PSV is characterized by the large growth of the South Atlantic Magnetic Anomaly (SAMA) during the last centuries, first documented by the geomagnetic model gufm1 (Jackson et al., 2000). A large amount of data is required to understand the time and geographic distribution of this primary feature, and the Andean Pleistocene and Holocene volcanoes are an excellent recorder of instant local changes in SV. Here we present a preliminary study from 18 paleomagnetic samples collected during 2015 on what it was supposed to be the 1750 or the 1957-58 AD lava flow on the Llaima Volcano (38.692° S; 71.729° W), one of the most active centers of the Chilean Andes, in the Southern Volcanic Zone. A detailed paleomagnetic study was performed in order to recover the Declination and Inclination of the geomagnetic field, obtain the paleointensity and define the magnetic mineralogy. AF demagnetization until 1 T yielded an average vector at Dec/Inc 2.3°/-33.1° with α95 of 2.4°. This direction is carried by titanomagnetite grains with 40-45% ulvospinel as revealed by thermomagnetic curves. Paleointensity estimates were obtained following the IZZI-Thellier protocol. Seven specimens from 5 samples provided reliable results (success rate of 35%), giving an average paleointensity for these specimens of 30.88 ± 2.39 μT. The full magnetic vector obtained here was compared to archaeomagnetic reference curves and the IGRF suggest that the lava flow has the age of 1957-58 AD.

  3. Lithologic combinations in Romanesque churches of Álava, northern Spain

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    Martínez-Torres, L. M.

    2014-03-01

    Full Text Available Certain windows and doorways on twenty five Romanesque churches of Álava (XII–XIII centuries were built using six types of rock in nine different combinations. These compositions were intended to highlight the contrast in colour between different rocks, from which it can be deduced that the openings were not hewn to be painted. After almost seven centuries during which the use of stone was anecdotal, Romanesque artists burst in with colourful blends, demonstrating a broad knowledge of the characteristics of each rock and its availability. The uniqueness of these openings is represented on lithologic maps which, in addition to facilitating its analysis and dissemination, serve as a reference in its restoration.Algunas ventanas y portadas de veinticinco iglesias románicas de Álava (siglos XII-XIII fueron construidas con hasta seis tipos de rocas en nueve combinaciones diferentes. Estas composiciones pretendían resaltar el contraste cromático entre rocas distintas, de lo que se deduce que los vanos no fueron tallados para ser policromados. Después de casi siete siglos en los que el uso de la piedra fuera anecdótico, los artistas románicos irrumpen con mezclas coloristas, mostrando un amplio conocimiento de las características de cada roca y su disponibilidad. La singularidad de estos vanos está representada en mapas litológicos que, además de facilitar su análisis y divulgación, servirán de referencia en su restauración

  4. Ultramafic lavas and pyroxene-spinifex high-Mg basaltic dykes from the Othris ophiolite complex, Greece

    Science.gov (United States)

    Baziotis, Ioannis; Economou-Eliopoulos, Maria; Asimow, Paul

    2017-04-01

    This study aims to constrain the physico-chemical conditions and processes associated with the origin of ultramafic lavas of the Agrilia formation and high-Mg basaltic dykes in the Pournari area within the Othris ophiolite complex, a supra-subduction zone ophiolite of Mesozoic age (Paraskevopoulos & Economou, 1986; Barth et al., 2008). Hand-sample-scale spinifex texture is lacking from the ultramafic lavas and, despite whole-rock MgO contents greater than 31 wt.%, we infer an upper bound of 17 wt.% MgO for the erupted liquid, and thus identify these lavas as picrites containing accumulated olivine. We use textural and compositional criteria to divide the crystals within the Agrilia lavas between pre-eruptive and post-eruptive growth phases. The high-Mg basaltic dyke margins display a distinctive thin-section-scale micro-spinifex texture of skeletal and plumose Al- and Fe-rich clinopyroxene surrounded by large crystals of orthopyroxene. Normally zoned clinopyroxene in the Agrilia lavas and clinopyroxene of various textures (skeletal, needle- and dendritic-like) and sizes in the Pournari dykes display anomalous enrichment in Al2O3 and FeO* with decreasing MgO that require rapid, disequilibrium growth. Quantitative characteristics of the micro-spinifex pyroxene textures (Elements and related metals are Pd/Ir=11.5-13.0, Cu/Pd=6000-7210, Ti/Pd=22.78-31.97×103 for Agrilia lavas and Pd/Ir=4.5-14.0, Cu/Pd=3140-5550, Ti/Pd=4.66-17.32×103 for Pournari dykes; all are very close to those reported for typical komatiites (Barnes et al., 1988). Despite the absence of true komatiite lavas, a number of geochemical features of the Othris suite, including the PGE contents and ratios and the micro-spinifex, disequilibrium cpx growth, are similar to Mesozoic and Archaean komatiites. References Barnes et al., 1988. Journal of Petrology 29, 305-331. Barth et al., 2008. Lithos, 100(1), 234-254. Faure et al., 2006. Journal of Petrology 47, 1591- 1610. Paraskevopoulos, G., Economou, M

  5. Magma chamber rejuvenation associated with Yellowstone 516-70 ka post-caldera rhyolitic lava flows : results from crystal geochemistry

    Science.gov (United States)

    Girard, G.; Stix, J.

    2007-12-01

    After Yellowstone caldera collapsed at 640 ka, it has been the focus of many voluminous rhyolite effusions. Over 900 km3 of magma have been erupted during relatively short periods, at 516 ka, 486-479 ka, 198 ka, and principally from 165 to 70 ka when the largest lava flows were emplaced. The last period itself consists of three episodes, from 165 to 147 ka, 117 to 102 ka, and 72 to 70 ka (Christiansen, 2001). The first-erupted lavas contain mainly plagioclase and sanidine. Quartz becomes increasingly abundant in younger flows, and clearly dominates over plagioclase in the 165 ka and younger rocks. Plagioclase is not present in the 117-102 ka and 72-70 ka lavas. Recent micro-analytical techniques have led to a better understanding of pre-eruptive conditions in magmatic systems by studying trace element concentrations and zoning in volcanic crystals. We analyzed plagioclase by electron microprobe and Ti in quartz by laser ablation-ICP-MS in order to assess changes in crystallization conditions from one period to the next, and also to reconstruct the pre-eruptive history of individual lava flows, by searching for potential dissolution, overgrowth or zoning features. Plagioclase in the lavas shifts progressively from a median value of An28 at 516 ka to An21 at ~ 160 ka. The plagioclase also contains decreasing amounts of K over time for a given level of Ca; for example, K2O at An22 declines from ~ 1.9 wt % in the oldest lavas to ~ 1.4 wt % in the 160 ka episode lavas, suggesting a reduced ability of plagioclase to incorporate K. This may translate into crystallization in a progressively cooler or shallower environment. Average Ti contents in quartz rims decrease from ~ 150- 200 ppm in the older lavas to ~ 100-125 ppm at ~ 160 ka and ~ 75-90 ppm at 70 ka. Zoned quartzes are found in most flows. They show higher Ti contents in the cores, with up to 240 ppm in the older lavas, 150 ppm at ~ 160 ka and 120 ppm at 70 ka. The temporal Ti decline in quartz rims and the normal

  6. The case of the missing vent: lessons in lava flow interpretation from Highway Flow, Craters of the Moon, Idaho

    Science.gov (United States)

    Hughes, S. S.; Nawotniak, S. K.; Haberle, C. W.; Downs, M.; Sehlke, A.; Elphic, R. C.; Lim, D. S. S.; Heldmann, J.

    2016-12-01

    Highway Flow, a latite lava flow at the northern edge of Craters of the Moon National Monument and Preserve in Idaho, appears to have been northward flowing on the basis of its footprint and broad morphology. In plan view, the overall morphology suggests a northward flow in a self-defined channel before finishing in a rounded terminus. Comparison with topographic maps clearly demonstrates, however, that this would require significant uphill travel. We hypothesize, based on topography, alteration, and contacts between flow lobes, that the lava flow emerged from a vent under the highest elevation in the central part of the flow. More detailed ground investigation with the Biologic Analog Science Associated with Lava Terrains (BASALT) and Field Investigations to Enable Solar System Science and Exploration (FINESSE) projects, using Highway flow as an analog for planetary lavas, demonstrates that Highway Flow is actually two separate compound flow lobes, one that flowed mostly westward and the other southward. The western lobe has a circular footprint and is extensively broken by radial fractures. The southern lobe is elongate, with sheared margins and interior ribs perpendicular to flow direction; the ribs include crude ogives and extension cracks. The vent for Highway Flow, previously thought to be buried by North Crater or Big Crater flows to the south or transported tephra from Sunset Cone to the east, is identifiable at the approximate center of the seam between the two lobes using new high-resolution DTMs from UAV flights and alteration patterns observed in the field and via multispectral imagery. Contrasting topographic controls surrounding the vent resulted in very different morphologies for the two lobes, despite emplacement under otherwise similar conditions. These results argue in favor of using multiple datasets, rather than simply using visual orbiter imagery, to interpret lava flow emplacement features on other planetary bodies.

  7. Using osmium isotopes to explore the link between alkaline lavas and metasomatized mantle in the Western Branch, Uganda

    Science.gov (United States)

    Nelson, W. R.; Furman, T.; Pitcavage, E.

    2016-12-01

    The subcontinental lithospheric mantle (SCLM) is foundational to understanding the construction, destruction, and division of tectonic plates. Tectonic processes both directly and indirectly influence the lithosphere's thermal, physical and mineralogical properties. Mantle melting and melt/fluid percolation cause fundamental changes to the lithosphere that affect its composition and stability. Specifically, metasomatism by silicate melts and hydrous/carbonated fluids can create lithologies (i.e. pyroxenites) that are denser, more fusible, and less viscous than adjacent peridotite. The resulting density instabilities may lead to lithospheric erosion, topographic uplift and even continental rifting. We explore the link between metasomatized SCLM and mafic volcanism in the Ugandan portion of the Western Branch of the East African Rift System using Re-Os isotopes from both alkaline mafic lavas and pyroxenite mantle xenoliths. The lavas record age-corrected 187Os/188Os that range from 0.1421 to 0.2105, which is more radiogenic than primitive mantle. These data demonstrate that many of the lavas were derived from a metasomatized mantle source though a few have experienced crustal contamination. Mantle xenoliths also record a wide range of 187Os abundances. One peridotite xenolith has a mildly radiogenic signature (187Os/188Os = 0.1342) whereas the pyroxenites span a wide range of 187Os/188Os ratios (0.1270-0.5052). Based on these data, we conclude that the lavas were derived from metasomatized SCLM. Some of the SCLM was sampled by mantle xenoliths but, as a whole, the SCLM is more heterogeneous than the lavas suggest. The widespread, metasomatized SCLM readily contributed to melt generation both in situ as well as during foundering via lithospheric drip (Furman et al., 2016). The SCLM-derived volcanism occurred prior to and during Western Rift extension, suggesting that the metasomatized SCLM played a vital role in rift development

  8. Hysteropexy in the treatment of uterine prolapse stage 2 or higher: a multicenter randomized controlled non-inferiority trial comparing laparoscopic sacrohysteropexy with vaginal sacrospinous hysteropexy (LAVA-trial, study protocol).

    Science.gov (United States)

    van IJsselmuiden, Mèlanie N; Coolen, Anne-Lotte W M; Detollenaere, Renée J; den Boon, Jan; Bongers, Marlies; van de Pol, Geerte; Vollebregt, Astrid; Radder, Celine M; Deprest, Jan; van Eijndhoven, Hugo W F

    2014-09-17

    Pelvic organ prolapse is a common health problem: the lifetime risk of undergoing surgery for pelvic organ prolapse by the age of 85 years is 19%. Pelvic organ prolapse has significant negative effects on a woman's quality of life. Worldwide, vaginal hysterectomy is the leading treatment method for patients with symptomatic uterovaginal prolapse. Several studies have shown that vaginal sacrospinous hysteropexy and laparoscopic sacrohysteropexy are safe and effective alternatives in treating uterine descent. To date, it is unclear which of these techniques leads to the best operative result and the highest patient satisfaction. Therefore, we conducted the LAVA trial. The LAVA trial is a randomized controlled multicenter non-inferiority trial. The study compares laparoscopic sacrohysteropexy with vaginal sacrospinous hysteropexy in women with uterine prolapse stage 2 or higher. The primary outcome of this study is surgical success of the apical compartment at 1 and 5 years follow-up. Secondary outcomes are subjective improvement on urogenital symptoms and quality of life (assessed by disease-specific and general quality of life questionnaires), complications following surgery, hospital stay, post-operative recovery, sexual functioning and costs-effectiveness. Evaluation will take place pre-operatively, and 6 weeks, 6 months, 12 months and annually till 60 months after surgery. Validated questionnaires will be used.Analysis will be performed according to the intention to treat principle. Based on comparable recurrence rates of 3% and a non-inferiority margin of 10%, 62 patients are needed in each arm to prove the hypothesis with a 95% confidence interval. The LAVA trial is a randomized controlled multicenter non-inferiority trial that will provide evidence whether the efficacy of laparoscopic sacrohysteropexy is non-inferior to vaginal sacrospinous hysteropexy in women with symptomatic uterine prolapse stage 2 or higher. Netherlands Trial Register (NTR): NTR4029.

  9. Silica-rich lavas in the oceanic crust: experimental evidence for fractional crystallization under low water activity

    Science.gov (United States)

    Erdmann, Martin; Koepke, Jürgen

    2016-10-01

    We experimentally investigated phase relations and phase compositions as well as the influence of water activity ( aH2O) and redox conditions on the equilibrium crystallization path within an oceanic dacitic potassium-depleted system at shallow pressure (200 MPa). Moreover, we measured the partitioning of trace elements between melt and plagioclase via secondary ion mass spectrometry for a highly evolved experiment (SiO2 = 74.6 wt%). As starting material, we used a dacitic glass dredged at the Pacific-Antarctic Rise. Phase assemblages in natural high-silica systems reported from different locations of fast-spreading oceanic crust could be experimentally reproduced only in a relatively small range of temperature and melt-water content ( T ~950 °C; melt H2O magnetite buffer. The relatively low water content is remarkable, because distinct hydrothermal influence is generally regarded as key for producing silica-rich rocks in an oceanic environment. However, our conclusion is also supported by mineral and melt chemistry of natural evolved rocks; these rocks are only congruent to the composition of those experimental phases that are produced under low aH2O. Low FeO contents under water-saturated conditions and the characteristic enrichment of Al2O3 in high aH2O experiments, in particular, contradict natural observations, while experiments with low aH2O match the natural trend. Moreover, the observation that highly evolved experimental melts remain H2O-poor while they are relatively enriched in chlorine implies a decoupling between these two volatiles during crustal contamination.

  10. Muon radiography and deformation analysis of the lava dome formed by the 1944 eruption of Usu, Hokkaido —Contact between high-energy physics and volcano physics—

    Science.gov (United States)

    TANAKA, Hiroyuki K. M.; YOKOYAMA, Izumi

    2008-01-01

    Lava domes are one of the conspicuous topographic features on volcanoes. The subsurface structure of the lava dome is important to discuss its formation mechanism. In the 1944 eruption of Volcano Usu, Hokkaido, a new lava dome was formed at its eastern foot. After the completion of the lava dome, various geophysical methods were applied to the dome to study its subsurface structure, but resulted in a rather ambiguous conclusion. Recently, from the results of the levelings, which were repeated during the eruption, “pseudo growth curves” of the lava dome were obtained. The curves suggest that the lava dome has a bulbous shape. In the present work, muon radiography, which previously proved effective in imaging the internal structure of Volcano Asama, has been applied to the Usu lava dome. The muon radiography measures the distribution of the “density length” of volcanic bodies when detectors are arranged properly. The result obtained is consistent with the model deduced from the pseudo growth curves. The measurement appears to afford useful method to clarify the subsurface structure of volcanoes and its temporal changes, and in its turn to discuss volcanic processes. This is a point of contact between high-energy physics and volcano physics. PMID:18941290

  11. Muon radiography and deformation analysis of the lava dome formed by the 1944 eruption of Usu, Hokkaido--contact between high-energy physics and volcano physics--.

    Science.gov (United States)

    K M Tanaka, Hiroyuki; Yokoyama, Izumi

    2008-01-01

    Lava domes are one of the conspicuous topographic features on volcanoes. The subsurface structure of the lava dome is important to discuss its formation mechanism. In the 1944 eruption of Volcano Usu, Hokkaido, a new lava dome was formed at its eastern foot. After the completion of the lava dome, various geophysical methods were applied to the dome to study its subsurface structure, but resulted in a rather ambiguous conclusion. Recently, from the results of the levelings, which were repeated during the eruption, "pseudo growth curves" of the lava dome were obtained. The curves suggest that the lava dome has a bulbous shape. In the present work, muon radiography, which previously proved effective in imaging the internal structure of Volcano Asama, has been applied to the Usu lava dome. The muon radiography measures the distribution of the "density length" of volcanic bodies when detectors are arranged properly. The result obtained is consistent with the model deduced from the pseudo growth curves. The measurement appears to afford useful method to clarify the subsurface structure of volcanoes and its temporal changes, and in its turn to discuss volcanic processes. This is a point of contact between high-energy physics and volcano physics.

  12. Discovery of a Plains Caldera Complex and Extinct Lava Lake in Arabia Terra, Mars: Implications for the Discovery of Additional Highland Volcanic Source Regions

    Science.gov (United States)

    Bleacher, Jacob; Michalski, Joseph

    2012-01-01

    Several irregularly shaped topographic depressions occur near the dichotomy boundary in northern Arabia Terra, Mars. The geomorphology of these features suggests that they formed by collapse, opposed to meteor impact. At least one depression (approx.55 by 85 km) displays geologic features indicating a complex, multi-stage collapse history. Features within and around the collapse structure indicate volcanic processes. The complex occurs within Hesperian ridged plains of likely volcanic origin and displays no crater rim or evidence for ejecta. Instead the depression consists of a series of circumferential graben and down-dropped blocks which also display upper surfaces similar to ridged plain lavas. Large blocks within the depression are tilted towards the crater center, and display graben that appear to have originally been linked with circumferential graben outside of the complex related to earlier collapse events. A nearly 700 m high mound exists along a graben within the complex that might be a vent. The deepest depression displays two sets of nearly continuous terraces, which we interpret as high-stands of a drained lava lake. These features appear similar to the black ledge described during the Kilauea Iki eruption in 1959. A lacustrine origin for the terraces seems unlikely because of the paucity of channels found in or around the depression that could be linked to aqueous surface processes. In addition, there is no obvious evidence for lacustrine sediments within the basin. Together with the presence of significant faulting that is indicative of collapse we conclude that this crater complex represents a large caldera formed in the Late Noachian to Early Hesperian. Other linear and irregular depressions in the region also might be linked to ancient volcanism. If that hypothesis is correct, it suggests that northern Arabia Terra could contain a large, previously unrecognized highland igneous province. Evacuation of magma via explosive and effusive activity

  13. Pre-eruptive volatile content, melt-inclusion chemistry, and microthermometry of interplinian Vesuvius lavas (pre-AD 1631)

    Science.gov (United States)

    Belkin, H.E.; de Vivo, B.; Torok, K.; Webster, J.D.

    1998-01-01

    Silicate-melt inclusions from lavas and pyroclastics from a selected suite of pre-A.D. 1631 interplinian Mt. Somma-Vesuvius lavas and scoria have been experimentally homogeneized and studied by microthermometry, electron microprobe (EMPA) and secondary-ion mass spectrometry (SIMS) to examine pre-eruptive volatile content and magma evolution. The melt inclusions have a bubble about 0.06% their volume, uncommonly contain non-condensable gas but do not contain any dense fluid phases. Clinopyroxene-hosted inclusions yield homogenization temperatures (Th) from 1170 to 1260??C, most between 1220 and 1240??C; plagiclase-hosted inclusions have Th from 1210 to 1230??C; these values are typical for the Vesuvius environment. The dominant factor controlling major element variability in the inclusions is clinopyroxene fractionation; MgO varies from 5 to 3 wt%, SiO2 varies from 60 to 48 wt%. total alkalis vary from 15 to 4 wt%, and CaO varies from 13 to 5 wt%. H2O varies from 2.7 to 0.6 wt% and is decoupled from incompatible element evolution suggesting vapor saturation during trapping. Chlorine and F vary from 1.- wt% to 0 and 0.63 to 0 wt%, respectively. Bulk rock and limited matrix glass analyses show that the lavas lost about half of their F and Cl content except for the A.D. 472-1631 lava which contains similar Cl abundances as the bulk rock. SO3 varies from 0.5 to 0 wt% and compared with matrix glass and bulk rock demonstrate that the lavas have lost essentially all sulfur. The samples can be classified into three age groups, ??? 25 000 yr B.P., 25 000-17 000 yr B.P., and A.D. 472-1631. There is a systematic increase in some components, e.g., total alkalis, SO3, Cl, Li, B, and Sr with the youth of the sample and a decrease in others, e.g., Zr and Y. However, on average these samples seem less evolved than later A.D. 1631-1944 lavas.

  14. Computer vision: automating DEM generation of active lava flows and domes from photos

    Science.gov (United States)

    James, M. R.; Varley, N. R.; Tuffen, H.

    2012-12-01

    Accurate digital elevation models (DEMs) form fundamental data for assessing many volcanic processes. We present a photo-based approach developed within the computer vision community to produce DEMs from a consumer-grade digital camera and freely available software. Two case studies, based on the Volcán de Colima lava dome and the Puyehue Cordón-Caulle obsidian flow, highlight the advantages of the technique in terms of the minimal expertise required, the speed of data acquisition and the automated processing involved. The reconstruction procedure combines structure-from-motion and multi-view stereo algorithms (SfM-MVS) and can generate dense 3D point clouds (millions of points) from multiple photographs of a scene taken from different positions. Processing is carried out by automated software (e.g. http://blog.neonascent.net/archives/bundler-photogrammetry-package/). SfM-MVS reconstructions are initally un-scaled and un-oriented so additional geo-referencing software has been developed. Although this step requires the presence of some control points, the SfM-MVS approach has significantly easier image acquisition and control requirements than traditional photogrammetry, facilitating its use in a broad range of difficult environments. At Colima, the lava dome surface was reconstructed from recent and archive images taken from light aircraft over flights (2007-2011). Scaling and geo-referencing was carried out using features identified in web-sourced ortho-imagery obtained as a basemap layer in ArcMap - no ground-based measurements were required. Average surface measurement densities are typically 10-40 points per m2. Over mean viewing distances of ~500-2500 m (for different surveys), RMS error on the control features is ~1.5 m. The derived DEMs (with 1-m grid resolution) are sufficient to quantify volumetric change, as well as to highlight the structural evolution of the upper surface of the dome following an explosion in June 2011. At Puyehue Cord

  15. Multi-component gas emission measurements of the active lava lake of Nyiragongo, DR Congo

    Science.gov (United States)

    Bobrowski, N.; Giuffrida, G. B.; Yalire, M.; Lübcke, P.; Arellano, S.; Balagizi, C.; Calabrese, S.; Galle, B.; Tedesco, D.

    2017-10-01

    Between 2007 and 2011 four measurement campaigns (June 2007, July 2010, June 2011, and December 2011) were carried out at the crater rim of Nyiragongo volcano, DR Congo. Nyiragongo is one of the most active volcanoes in Africa. The ground-based remote sensing technique Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS), which uses scattered sunlight, the in-situ Multi-Component Gas Analyzer System (Multi-GAS) and alkaline impregnated filter were simultaneously applied during all field trips. The bromine monoxide to sulfur dioxide (BrO/SO2) and carbon dioxide to sulfur dioxide (CO2/SO2) molar ratios were determined, among other ratios. During the different field trips variations of the level of the lava lake up to several tens of meters were observed during intervals of the order of minutes up to days and also between the years. The measured gas ratios presented covariations with the lava lake level changes. BrO/SO2 ratios and CO2/SO2 ratios showed similar behavior. Annual CO2/SO2 and BrO/SO2 average values are generally positively correlated. In June 2011 increased BrO/SO2 as well as increased CO2/SO2 ratios have been observed before a sudden decrease of the lava lake. Overall the Cl/S ratio, determined by filter-pack sampling, shows an increasing trend with time, which is accompanied by a decreasing sulfur dioxide flux, the later measured nearly continuously by automated MAX-DOAS instruments since 2004. Mean gas emission fluxes of CO2, Cl and 'minimum-BrO' fluxes are calculated using their ratio to SO2. The first two show an increase with time, in contrast to the SO2 fluxes. A simple conceptual model is proposed which can explain in particular the June 2011 data, but as well our entire data set. The proposed model takes up the idea of convective magma cells inside the conduit and the possible temporary interruption of part of the cycling. We propose than two alternatives to explain the observed gas emission variation: 1. It is assumed that the

  16. Siliceous alterations of the Montana Senalo lavas, Timanfaya eruption (1730-1736) (Lanzarote, Canary Islands); Las alteraciones siliceas de las lavas de Montana Senalo, eruption de Timanfaya (1730-1736) (Lanzarote, Islas Canarias)

    Energy Technology Data Exchange (ETDEWEB)

    Carmona, J.; Romero, C.; Doniz, J.; Garcia, A.

    2009-07-01

    The presence of hydrothermal alterations within the lavas of Timanfaya eruption (1730-1736), with high proportions of quartz and opal, suggests the effective circulation of hot fluids. The source of these fluids would be located under the island, where silica would be dissolved from sandstones and radiolarites, moving this way towards the surface as Si(OH){sub 4} colloids. Study of opal indicates the presence of A-initial CT and C phases in the collected samples, which, considering the time needed for producing this phase transformations in the diagenetic evolution of opal (10,000-50,000 years), suggests an accelerating process, probably related with either the presence of fluid circulation or weathering processes. Such circumstances are necessary for explaining the presence of such components affecting 300 years old lavas. (Author) 36 refs.

  17. Paleomagnetism and Rock Magnetic Properties from Quaternary Lavas and Tuffs of the Yellowstone Plateau Volcanic Field

    Science.gov (United States)

    Harlan, S. S.; Morgan, L. A.

    2008-12-01

    We report paleomagnetic and rock magnetic from rhyolite lava flows, ignimbrites, and basalt flows associated with the Yellowstone Caldera, within and surrounding Yellowstone National Park. These data were collected in order to understand sources of magnetic variations observed in high resolution aeromagnetic data reported by Finn and Morgan (2002), and to better understand the evolution of the Yellowstone magmatic system. Most paleomagnetic samples are from volcanic rocks of the third eruptive cycle (1.2 Ma to 0.070 Ma), including the ca. 0.640 Ma Lava Creek Tuff, postcaldera rhyolite flows, and contemporaneous marginal or post-caldera basalt flows. Magnetic intensities for samples ranged from 0.12 A/m to 5.9 A/m, with volume susceptibilities of 2.14x10-4 to 1.45x10-3 SI; Q ratios range from 0.67 to 23.8. As expected, most sites yield well-defined paleomagnetic directions of north declination and moderate positive inclination consistent with remanence acquisition during the Brunhes polarity chron. However, a few sites from older units such as the rhyolites of the Harlequin Lake (0.839 ± 0.007 Ma) and Lewis Canyon (0.853 ± 0.008 Ma) flows, and the basalts from the Junction Butte flow (at Tower Falls, 2.16 ± 0.04 Ma) and Hepburn Mesa (2.2 Ma) yield reverse polarity magnetizations (40Ar/39Ar dates from Obradovich, 1992, and Harlan, unpublished (Hepburn Mesa flow)). Rock magnetic behavior, including high coercivities during AF demagnetization, high laboratory unblocking temperatures, and susceptibility vs. temperature determinations indicate that remanence in the rhyolitic samples is carried by a combination of single or pseudo-single domain magnetite and/or hematite; in the basalt flows magnetite and high-Ti titanomagnetite carrys the remanence. Paleomagnetic results from 46 sites in 27 separate flows yields a grand mean direction with a declination of 356.9° and inclination of 61.9° (k = 35.2, α95 = 4.8°). VGPs calculated from the site-mean directions yield a

  18. The behavior of chalcophile elements during magmatic differentiation as observed in Kilauea Iki lava lake, Hawaii

    Science.gov (United States)

    Greaney, Allison T.; Rudnick, Roberta L.; Helz, Rosalind T.; Gaschnig, Richard M.; Piccoli, Philip M.; Ash, Richard D.

    2017-08-01

    We quantify the behavior of Cu, Ga, Ge, As, Mo, Ag, Cd, In, Sn, Sb, W, Tl, Pb, and Bi during the differentiation of a picritic magma in the Kilauea Iki lava lake, Hawaii, using whole rock and glass differentiation trends, as well as partition coefficients in Cu-rich sulfide blebs and minerals. Such data allow us to constrain the partitioning behavior of these elements between sulfide and silicate melts, as well as the chalcophile element characteristics of the mantle source of the Kilauea lavas. Nearly all of the elements are generally incompatible on a whole-rock scale, with concentrations increasing exponentially below ∼6 wt% MgO. However, in-situ laser ablation data reveal that Cu, Ag, Bi, Cd, In, Pb, and Sn are chalcophile; As, Ge, Sb, and Tl are weakly chalcophile to lithophile; and Mo, Ga, and W are lithophile. The average Dsulfide/silicate melt values are: DAg = 1252 ± 1201 (2SD), DBi = 663 ± 576, DCd = 380 ± 566, DIn = 40 ± 34, DPb = 34 ± 18, DSn = 5.3 ± 3.6, DAs = 2.4 ± 7.6, DGe = 1.6 ± 1.4, DSb = 1.3 ± 1.5, DTl = 1.1 ± 1.7, DMo = 0.56 ± 0.6, DGa = 0.10 ± 0.3, and DW = 0.11 ± 0.1. These findings are consistent with experimental partitioning studies and observations of Ni-rich sulfide liquid in mid-ocean ridge basalts (MORB), despite the different compositions of the KI sulfides. The KI glasses and whole rocks are enriched in As, Ag, Sb, W, and Bi, relative to elements of similar compatibility (as established by abundances in MORB), mimicking enrichments found in basalts from the Manus back arc basin (Jenner et al., 2012) and the upper continental crust (UCC). These enrichments suggest the presence of terrigenous sediments in the Kilauea mantle source. The KI source is calculated to be a mixture of depleted MORB mantle (DMM) and 10-20% recycled crust composed of MORB and minor terrigenous sediments.

  19. Receiver Function Imaging of Upper Mantle Discontinuities Beneath the Oregon High Lava Plains and Surrounding Regions

    Science.gov (United States)

    Eagar, K. C.; Fouch, M. J.

    2007-12-01

    The Pacific Northwestern United States has experienced wide-spread tectonomagmatism from the late Cenozoic to present-day, the reasons for which are likely linked to complex interactions between subduction zone processes near the edge of a Precambrian craton, possible hotspot effects, and mantle flow within the asthenosphere. The goal of this study is to examine upper mantle seismic velocity discontinuities beneath this region to investigate the connection between these geodynamic processes. We present results from analysis of Ps receiver functions using stations from the High Lava Plains temporary broadband seismic experiment, the USArray Transportable Array (TA), and other regional broadband stations for a total of over 108 stations in the region. We compute receiver functions at individual stations using an iterative deconvolution approach, and generate common conversion point (CCP) stacks using moveout corrections defined by the Tectonic North America (TNA) shear wave velocity model. Results from our imaging show that conversions from the 410 km discontinuity have narrow, high amplitude peaks across most of the region, with local complexity in peaks for some areas. Conversely, most conversions near the 660 km discontinuity exhibit peaks that are broad and less well-defined. Estimates in transition zone thickness show local variability, with notable areas of thickening in northeastern Oregon into Idaho and thinning under the coastal regions. The complexity in upper mantle discontinuity structure in this region is likely due to a combination of strong variations in isotropic and anisotropic seismic wavespeeds. The local complexities of the 410 km discontinuity correlate well with seismic wavespeed anomalies imaged by regional P-wave tomography. The source of the variations in the 660 km discontinuity are less apparent, but we note that seismic anisotropy is strong and regionally homogenous across much of the region, perhaps producing backazimuthal variations in

  20. Inflation Features of the Distal Pahoehoe Portion of the 1859 Mauna Loa Flow, Hawaii; Implications for Evaluating Planetary Lava Flows

    Science.gov (United States)

    Zimbelman, J. R.; Garry, W. B.; Bleacher, Jacob E.; Crumpler, L S.

    2011-01-01

    The 1859 eruption of Mauna Loa, Hawaii, resulted in the longest subaerial lava flow on the Big Island. Detailed descriptions were made of the eruption both from ships and following hikes by groups of observers; the first three weeks of the eruption produced an `a`a flow that reached the ocean, and the following 10 months produced a pahoehoe flow that also eventually reached the ocean. The distal portion of the 1859 pahoehoe flow component includes many distinctive features indicative of flow inflation. Field work was conducted on the distal 1859 pahoehoe flow during 2/09 and 3/10, which allowed us to document several inflation features, in or-der evaluate how well inflated landforms might be detected in remote sensing data of lava flows on other planets.

  1. Thermal, radioactive and magnetic properties of the lavas of the Mt Melbourne Volcanic Field (Victoria Land, Antarctica

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    Egidio Armadillo

    2009-06-01

    Full Text Available We present the results of measurements of physical properties carried out on mafic lavas from the Mt Melbourne
    Volcanic Field, useful for interpretation of geophysical surveys designed to shed light on the structure of the
    crust. The thermal conductivity is comparable to that of glass and shows a clear negative dependence on porosity.
    The volume heat capacity and the thermal diffusivity are less variable. The concentration of the thermally
    important natural radioactive isotopes was determined by gamma-ray spectrometry. Lavas denoted a rather low
    heat-production rate, and the largest concentration of heat-producing elements (potassium, uranium, thorium
    was found in the trachyte samples. The magnetic susceptibility is more variable than the other physical properties
    and, among the several iron-titanium oxides, it appears primarily controlled by the ulvöspinel-magnetite solid
    solution series.

  2. Basaltic lava characterization using magnetic susceptibility identification and presence of opaque minerals in Ijen volcanic complex, Banyuwangi, East Java

    Science.gov (United States)

    Pratama, Aditya; Hafidz, Abd.; Bijaksana, Satria; Abdurrachman, Mirzam

    2017-07-01

    Reliable volcanic map and deep understanding of magmatic processes are very important in exploration of natural resources and mitigation of volcanic hazards. The conservative method in volcanic mapping still depends on qualitative approach thus it often failed to characterize volcanic products properly. Rock magnetic methods are quantitative approaches that classify rocks based on their magnetic properties. In this study, magmatic processes in basaltic lavas from Ijen volcanic complex in Banyuwangi, East Java were studied using combined rock magnetic and petrogenesis approaches. Samples of basaltic lavas from 13 localities, taken from three eruption sources were measuredfor their mass-specific magnetic susceptibility. The samples were then also subjected to petrographic and X-ray Fluorescence Spectrometry (XRF) analyses for their minerals composition and petrogenesis. Preliminary results show that the distinction in magnetic characters might be due to the quantity of magnetic minerals contained in rocks.

  3. A high-resolution 40Ar/39Ar lava chronology and edifice construction history for Ruapehu volcano, New Zealand

    Science.gov (United States)

    Conway, Chris E.; Leonard, Graham S.; Townsend, Dougal B.; Calvert, Andrew T.; Wilson, Colin J. N.; Gamble, John A.; Eaves, Shaun R.

    2016-11-01

    Ruapehu is an active 150 km3 andesite-dacite composite volcano located at the southern end of the Taupo Volcanic Zone, New Zealand. The growth of the present-day edifice has occurred throughout coeval eruptive and glacial histories since 200 ka. We present high-precision 40Ar/39Ar eruption ages for 46 samples and whole-rock major element geochemical data for 238 samples from lava flows. These new and existing data are interpreted in the context of geomorphologic and geologic mapping, volcano-ice interaction processes and glacier reconstructions to present an improved chronostratigraphic framework and new edifice evolution history for Ruapehu. Sub-glacial to ice-marginal effusive eruption of medium-K basaltic-andesites and andesites constructed the northern portion of the exposed edifice between 200 and 150 ka, and a wide southeast planèze as well as parts of the northern, eastern and western flanks between 160 and 80 ka. None of the dated lava flows have ages in the range of 80-50 ka, which may reflect an eruptive hiatus. Alternatively the lack of ages may be the result of erosion and burial of lavas and syn-eruptive glacial conveyance of lava flows to the ring-plain during glacial advance at 70-60 ka. From 50-15 ka edifice growth occurred via effusive eruptions onto the glaciated flanks of the volcano, resulting in construction of ice-bounded planèzes and ridges. The distribution of dated ice-marginal lavas indicates a general decrease in glacier thicknesses over this time, except for a short-lived period centred at 31 ka when peak ice cover was reached. The compositional ranges of medium- to high-K andesite and dacite lava flows within 50-35 ka eruptive packages define broadly bimodal high- and low-MgO trends. Lavas erupted at 35-22 ka have compositions that fill a transitional geochemical field between older dacites and younger andesites. Large-scale retreat of flank glaciers since 15 ka has resulted in intra-valley lava flow emplacement at elevations below

  4. Diversity of carabid beetles (Carabidae in quarries of Pálava

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    Lucie Nováková

    2013-01-01

    Full Text Available During the vegetation period of 2012, a faunistic survey of carabid beetles was conducted with focus on selected limestone quarries in the Pálava PLA. In the Turold quarry, 39 species in the total number of 270 specimens were captured, while the most abundant species was Carabus cancellatus. In the Svatý kopeček quarry, a total of 36 species with the total number of 420 specimens were collected, the most numerous species here was Pseudoophonus rufipes. Four protected species under the Decree 395/1992 Coll., as amended by Decree No. 175/2006 Coll. – Brachinus crepitans, B. explodens, Carabus ullrichii ullrichii, and Cylindera germanica and 6 species listed in the Red List of the Czech Republic – Licinus cassideus, Carabus cancellatus, Cylindera germanica, Cymindis axillaris, Notiophilus laticollis, and Poecilus sericeus were recorded in the areas investigated. Typical xerothermophilous species preferred the medium-term quarry of Svatý kopeček to the Turold quarry, which has been closed for almost 70 years now.

  5. Muerte violenta en 1822: una fosa común en Ocio (Zambrana, Álava

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    Berjón, M.A.

    2012-01-01

    Full Text Available En la excavación llevada a cabo en el suelo de la Ermita de Nuestra Señora de Asunción en Ocio (Zambrana, Álava en 2010, se expusieron un total de 48 enterramientos individuales y uno de tipo colectivo. Este último corresponde a una fosa común en la que se hallaban 13 individuos de sexo masculino que murieron en un mismo episodio de carácter violento. Todos los individuos presentan lesiones en cráneo o/y en el cuerpo compatibles con el paso de proyectil de arma de fuego de plomo, así como heridas incisas provocadas por arma cortante, además de traumas directos. En la investigación histórica realizada se ha podido saber que en un enfrentamiento bélico en 1822 se produjo la muerte simultánea de 13 vecinos de la localidad de Brinas (próxima a Ocio. Este suceso estaría relacionado con las luchas entre absolutistas o realistas y liberales o constitucionalistas, en los prolegómenos de la Primera Guerra Carlista.

  6. Multiple subduction imprints in the mantle below Italy detected in a single lava flow

    Science.gov (United States)

    Nikogosian, Igor; Ersoy, Özlem; Whitehouse, Martin; Mason, Paul R. D.; de Hoog, Jan C. M.; Wortel, Rinus; van Bergen, Manfred J.

    2016-09-01

    Post-collisional magmatism reflects the regional subduction history prior to collision but the link between the two is complex and often poorly understood. The collision of continents along a convergent plate boundary commonly marks the onset of a variety of transitional geodynamic processes. Typical responses include delamination of subducting lithosphere, crustal thickening in the overriding plate, slab detachment and asthenospheric upwelling, or the complete termination of convergence. A prominent example is the Western-Central Mediterranean, where the ongoing slow convergence of Africa and Europe (Eurasia) has been accommodated by a variety of spreading and subduction systems that dispersed remnants of subducted lithosphere into the mantle, creating a compositionally wide spectrum of magmatism. Using lead isotope compositions of a set of melt inclusions in magmatic olivine crystals we detect exceptional heterogeneity in the mantle domain below Central Italy, which we attribute to the presence of continental material, introduced initially by Alpine and subsequently by Apennine subduction. We show that superimposed subduction imprints of a mantle source can be tapped during a melting episode millions of years later, and are recorded in a single lava flow.

  7. Paleomagnetism of the Caldwell lavas, Eastern Townships, Québec.

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    M. K. SEGUIN

    1978-06-01

    Full Text Available Forty two oriented samples (97 specimens were obtained from 17
    sites in metavolcanic rocks from the Caldwell Group of the Appalachians
    of Southern Québec (longitude: 71u00'-71"30' W, latitude: 46°00'-46"10'N.
    These metavolcanics of Lower Cambrian age are massive or pillowed lavas
    of andesitic and mainly basaltic composition metamorphosed to the
    sub-greenschist facies. Magnetite and occasionally hematite are the frequent
    magnetic memory carrier.
    In order to obtain some pertinent information relative to the stability
    of the remanent magnetization component, stepwise alternating field
    demagnetization was conducted on 35% of the specimens and the others
    were demagnetized at an optimum alternating field. After AF treatment,
    the paleopole position of the tilted formation from 16 localities is 148°E,
    43°N (dp=11.3°, dm = 22.4°. After omission of 3 localities for which
    a95>30°, the new paleopole position obtained is 173°E, 26°N. This formation
    of Early Cambrian age is characterized by a reversed polarity.

  8. Zeolites in Eocene basaltic pillow lavas of the Siletz River Volcanics, Central Coast Range, Oregon

    Science.gov (United States)

    Keith, Terry E.C.; Staplese, Lloyd W.

    1985-01-01

    Zeolites and associated minerals occur in a tholeiitic basaltic pillow lava sequence that makes up part of the Eocene Siletz River Volcanics in the central Coast Range, Oregon. Regional zoning of zeolite assemblages is not apparent; the zeolites formed in joints, fractures, and interstices, although most occur in central cavities of basalt pillows. The zeolites and associated minerals identified, in general order of paragenetic sequence, are smectite, pyrite, calcite (small spheres), thomsonite, natrolite, analcime, scolecite, mesolite, stilbite, heulandite, apophyllite, chahazite, mordenite, calcite (scalenohedra and twinned rhombohedra), laumontite, and amethystine quartz. Common three-mineral assemblages are: natrolite-analcime-sfilbite, stilbite-heulandite-chabazite, stilbite-apophyllie-chabazite, and natrolite-mesolite-laumontite.Alteration of basaltic glass, which was initially abundant, appears to have been an important factor in formation of the zeolites. Isotopic data suggest that zeolitization occurred during a low-temperature (60 ~ 70°C submarine hydrothermal event, or by reactions of cold (~ 10°C meteoric water with basalt over a long time. The occurrence of different mineral assemblages in cavities of adjacent basalt pillows indicates that these minerals crystallized in dosed systems that were isolated as fractures and joints were sealed by deposition of smectite and early zeolites. Although the total chemical composition of the mineral assemblages in cavities is similar, different mineral species formed because of the sensitivity of zeolite minerals to slight variations in physical and chemical conditions within individual cavities.

  9. Monitoring the Environment in a Lava Tube with a Wireless Sensor Network

    Science.gov (United States)

    Li, Y.; Jorgensen, A. M.; Wilson, J. L.; Rendon, N. M.

    2010-12-01

    Monitoring cave environments is important for several reasons. For instance, through the studies of cave environments, we can better protect cave ecology. Past experiments have monitored cave environments, although most of those were based on individual sensor nodes such as data loggers. In this paper we introduce and discuss a ZigBee wireless sensor network-based platform used for cave environment monitoring. The platform is based on a Freescale ZigBee evaluation kit. We carried out a proof-of-concept experiment in Junction Cave, a lava tube, at El Malpais National Monument in New Mexico. That experiment monitored temperature, humidity, and air turbulence inside the cave. The instrumentation consisted of a turbulence tower with five thermocouple-based sensors, reaching from the floor to the ceiling of the cave, temperature/humidity sensors distributed throughout the cave, and a low-power embedded Linux computer for data collection and storage. The experiment measured interesting air turbulence variations at different heights, which we related to to weather changes outside the cave and human activities inside the cave. The experiment also observed variations of air temperature at different locations inside the cave. In this presentation we will discuss the instrumentation as well as interpretations of the observations. The experiment demonstrated that a ZigBee wireless sensor network-based monitoring system is a potentially feasible platform for a cave environment monitoring system. We also found that network reliability, node cost, and power consumption need to be improved for future systems.

  10. Emplacement of Holocene silicic lava flows and domes at Newberry, South Sister, and Medicine Lake volcanoes, California and Oregon

    Science.gov (United States)

    Fink, Jonathan H.; Anderson, Steven W.

    2017-07-19

    This field guide for the International Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI) Scientific Assembly 2017 focuses on Holocene glassy silicic lava flows and domes on three volcanoes in the Cascade Range in Oregon and California: Newberry, South Sister, and Medicine Lake volcanoes. Although obsidian-rich lava flows have been of interest to geologists, archaeologists, pumice miners, and rock hounds for more than a century, many of their emplacement characteristics had not been scientifically observed until two very recent eruptions in Chile. Even with the new observations, several eruptive processes discussed in this field trip guide can only be inferred from their final products. This makes for lively debates at outcrops, just as there have been in the literature for the past 30 years.Of the three volcanoes discussed in this field guide, one (South Sister) lies along the main axis defined by major peaks of the Cascade Range, whereas the other two lie in extensional tectonic settings east of the axis. These two tectonic environments influence volcano morphology and the magmatic and volcanic processes that form silicic lava flows and domes. The geomorphic and textural features of glass-rich extrusions provide many clues about their emplacement and the magma bodies that fed them.The scope of this field guide does not include a full geologic history or comprehensive explanation of hazards associated with a particular volcano or volcanic field. The geochemistry, petrology, tectonics, and eruption history of Newberry, South Sister, and Medicine Lake volcanic centers have been extensively studied and are discussed on other field excursions. Instead, we seek to explore the structural, textural, and geochemical evolution of well-preserved individual lava flows—the goal is to understand the geologic processes, rather than the development, of a specific volcano.

  11. An analogue study of the influence of solidification on the advance and surface thermal signature of lava flows

    Science.gov (United States)

    Garel, F.; Kaminski, E.; Tait, S.; Limare, A.

    2014-06-01

    The prediction of lava flow advance and velocity is crucial during an effusive volcanic crisis. The effusion rate is a key control of lava dynamics, and proxies have been developed to estimate it in near real-time. The thermal proxy in predominant use links the satellite-measured thermal radiated power to the effusion rate. It lacks however a robust physical basis to allow time-dependent modeling. We investigate here through analogue experiments the coupling between the spreading of a solidifying flow and its surface thermal signal. We extract a first order behavior from experimental results obtained using polyethylene glycol (PEG) wax, that solidifies abruptly during cooling. We find that the flow advance is discontinuous, with relatively low supply rates yielding long stagnation phases and compound flows. Flows with higher supply rates are less sensitive to solidification and display a spreading behavior closer to that of purely viscous currents. The total power radiated from the upper surface also grows by stages, but the signal radiated by the hottest and liquid part of the flow reaches a quasi-steady state after some time. This plateau value scales around half of the theoretical prediction of a model developed previously for the spreading and cooling of isoviscous gravity currents. The corrected scaling yields satisfying estimates of the effusion rate from the total radiated power measured on a range of basaltic lava flows. We conclude that a gross estimate of the supply rate of solidifying flows can be retrieved from thermal remote-sensing, but the predictions of lava advance as a function of effusion rate appears a more difficult task due to chaotic emplacement of solidifying flows.

  12. Geochemistry of pillow lavas and their clinopyroxene: ophiolitic mélanges of Nain and Ashin, northeastern Isfahan province

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    Nargess Shirdashtzadeh

    2016-04-01

    Full Text Available The Nain and Ashin ophiolites are located in northeastern Isfahan province, in western Central-East Iranian Microplate. Pillow lavas are one of the most significant Cretaceous rock units. The lower partial melting degree in mantle peridotites of Ashin ophiolite, and the derived melt by melting their clinopyroxene caused a more basic (basalt and enriched nature for the Ashin pillow lavas, whereas higher partial melting degree and consequently incongruent melting of orthopyroxene and increment of silica in the ascending melt, together with aqueous fluids led to formation of more acidic (andesite – basaltic andesite and depleted melts (in trace elements in Nain ophiolite. The REE content of Nain samples have IAT chemical affinity, but the samples from Ashin show MORB characteristics. Based on petrograhic observations, lower Eu/Eu* of clinopyroxene phenocrystals of Ashin, calculated Kd of clinopyroxene together with HREE enrichment in the melt in equilibrium with clinopyroxene (especially in Ashin when compared with Nain, the plagioclase crystallization was primer and higher in comparison with clinopyroxene, especially in Ashin compared with Nain. The melt in equilibrium with clinopyroxene in Ashin was similar to MORB composition, whereas it is similar to IAT in Nain. Thus, despite the proximity of these two ophiolitic series and some field and petrographic similarities, pillow lavas from them are different from each other in both primary melt composition and the processes of differentiation and the tectonic setting.

  13. Lava Flow Alteration at Craters of the Moon, Idaho, as an Analog for Microbial Habitat on Mars

    Science.gov (United States)

    Kobs-Nawotniak, S. E.; Hughes, S. S.; Elphic, R. C.; Sehlke, A.; Haberle, C. W.; Brady, A. L.; Payler, S.; Cockell, C. S.; Lim, D. S. S.

    2016-12-01

    Craters of the Moon National Monument and Preserve (COTM), Idaho is host to lava flows with comparable composition and texture to those observed on Mars. As part of the Biologic Analog Science Associated with Lava Terrains (BASALT) project, we investigated the relationship between alteration style and gradient scales in three young ( 2000 y.b.p.) lava flows at COTM. Alteration of volcanic substrate is known to improve microbial habitability. As such, our investigation seeks to identify and characterize microbial habitat analogs potentially representative of Noachian and Amazonian Mars. Alteration in these flows is dominantly the result of two processes; (1) syn-emplacement degassing and (2) sub-aerial interaction with eolian material and meteoric water. Syn-emplacement alteration products are dominated by hematite and goethite along with various clays and zeolites. These products are concentrated where heat persists during and following emplacement (e.g. proximal to eruptive and non-eruptive vents and in areas exhibiting significant textural transitions, possibly related to degassing concentrated along disrupted surfaces). The syn-eruptive alteration zones display mineralogical variation across cm-scales, and occur as patchy zones spanning multiple meters. Post-emplacement, ambient meteoric alteration is characterized by carbonates, zeolites and clays concentrated along fractures and within vesicles. Owing to their deposition along fractures, these alteration zones may be less than a millimeter thick, but span multiple meters. Our multidisciplinary team of geologists, microbiologists and organic geochemists seek to identify associations of alteration styles and microbial habitability.

  14. Lava Cave Microbial Communities Within Mats and Secondary Mineral Deposits: Implications for Life Detection on Other Planets

    Science.gov (United States)

    Melim, L.A.; Spilde, M.N.; Hathaway, J.J.M.; Garcia, M.G.; Moya, M.; Stone, F.D.; Boston, P.J.; Dapkevicius, M.L.N.E.; Riquelme, C.

    2011-01-01

    Abstract Lava caves contain a wealth of yellow, white, pink, tan, and gold-colored microbial mats; but in addition to these clearly biological mats, there are many secondary mineral deposits that are nonbiological in appearance. Secondary mineral deposits examined include an amorphous copper-silicate deposit (Hawai‘i) that is blue-green in color and contains reticulated and fuzzy filament morphologies. In the Azores, lava tubes contain iron-oxide formations, a soft ooze-like coating, and pink hexagons on basaltic glass, while gold-colored deposits are found in lava caves in New Mexico and Hawai‘i. A combination of scanning electron microscopy (SEM) and molecular techniques was used to analyze these communities. Molecular analyses of the microbial mats and secondary mineral deposits revealed a community that contains 14 phyla of bacteria across three locations: the Azores, New Mexico, and Hawai‘i. Similarities exist between bacterial phyla found in microbial mats and secondary minerals, but marked differences also occur, such as the lack of Actinobacteria in two-thirds of the secondary mineral deposits. The discovery that such deposits contain abundant life can help guide our detection of life on extraterrestrial bodies. Key Words: Biosignatures—Astrobiology—Bacteria—Caves—Life detection—Microbial mats. Astrobiology 11, 601–618. PMID:21879833

  15. Lava cave microbial communities within mats and secondary mineral deposits: implications for life detection on other planets.

    Science.gov (United States)

    Northup, D E; Melim, L A; Spilde, M N; Hathaway, J J M; Garcia, M G; Moya, M; Stone, F D; Boston, P J; Dapkevicius, M L N E; Riquelme, C

    2011-09-01

    Lava caves contain a wealth of yellow, white, pink, tan, and gold-colored microbial mats; but in addition to these clearly biological mats, there are many secondary mineral deposits that are nonbiological in appearance. Secondary mineral deposits examined include an amorphous copper-silicate deposit (Hawai'i) that is blue-green in color and contains reticulated and fuzzy filament morphologies. In the Azores, lava tubes contain iron-oxide formations, a soft ooze-like coating, and pink hexagons on basaltic glass, while gold-colored deposits are found in lava caves in New Mexico and Hawai'i. A combination of scanning electron microscopy (SEM) and molecular techniques was used to analyze these communities. Molecular analyses of the microbial mats and secondary mineral deposits revealed a community that contains 14 phyla of bacteria across three locations: the Azores, New Mexico, and Hawai'i. Similarities exist between bacterial phyla found in microbial mats and secondary minerals, but marked differences also occur, such as the lack of Actinobacteria in two-thirds of the secondary mineral deposits. The discovery that such deposits contain abundant life can help guide our detection of life on extraterrestrial bodies.

  16. Pioneer microbial communities of the Fimmvörðuháls lava flow, Eyjafjallajökull, Iceland.

    Science.gov (United States)

    Kelly, Laura C; Cockell, Charles S; Thorsteinsson, Thorsteinn; Marteinsson, Viggó; Stevenson, John

    2014-10-01

    Little is understood regarding the phylogeny and metabolic capabilities of the earliest colonists of volcanic rocks, yet these data are essential for understanding how life becomes established in and interacts with the planetary crust, ultimately contributing to critical zone processes and soil formation. Here, we report the use of molecular and culture-dependent methods to determine the composition of pioneer microbial communities colonising the basaltic Fimmvörðuháls lava flow at Eyjafjallajökull, Iceland, formed in 2010. Our data show that 3 to 5 months post eruption, the lava was colonised by a low-diversity microbial community dominated by Betaproteobacteria, primarily taxa related to non-phototrophic diazotrophs such as Herbaspirillum spp. and chemolithotrophs such as Thiobacillus. Although successfully cultured following enrichment, phototrophs were not abundant members of the Fimmvörðuháls communities, as revealed by molecular analysis, and phototrophy is therefore not likely to be a dominant biogeochemical process in these early successional basalt communities. These results contrast with older Icelandic lava of comparable mineralogy, in which phototrophs comprised a significant fraction of microbial communities, and the non-phototrophic community fractions were dominated by Acidobacteria and Actinobacteria.

  17. Effect of temperature on the permeability of lava dome rocks from the 2004-2008 eruption of Mount St. Helens

    Science.gov (United States)

    Gaunt, H. Elizabeth; Sammonds, Peter R.; Meredith, Philip G.; Chadderton, Amy

    2016-04-01

    As magma ascends to shallow levels in the volcanic conduit, volatile exsolution can produce a dramatic increase in the crystal content of the magma. During extrusion, low porosity, highly crystalline magmas are subjected to thermal stresses which generate permeable microfracture networks. How these networks evolve and respond to changing temperature has significant implications for gas escape and hence volcano explosivity. Here, we report the first laboratory experimental study on the effect of temperature on the permeability of lava dome rocks under environmental conditions designed to simulate the shallow volcanic conduit and lava dome. Samples were collected for this study from the 2004-2008 lava dome eruption of Mount St. Helens (Washington State, USA). We show that the evolution of microfracture networks, and their permeability, depends strongly on temperature changes. Our results show that permeability decreases by nearly four orders of magnitude as temperature increases from room temperature to 800 °C. Above 800 °C, the rock samples become effectively impermeable. Repeated cycles of heating leads to sample compaction and a reduction in fracture density and therefore a decrease in permeability. We argue that changes in eruption regimes from effusive to explosive activity can be explained by strongly decreasing permeability caused by repeated heating of magma, conduit walls and volcanic plugs or domes. Conversely, magma becomes more permeable as it cools, which will reduce explosivity.

  18. Enriched and depleted source components for tholeiitic and alkaline lavas from Zuni-Bandera, New Mexico: Inferences about intraplate processes and stratified lithosphere

    Science.gov (United States)

    Menzies, Martin A.; Kyle, Philip R.; Jones, Michael; Ingram, Gerry

    1991-07-01

    During the Pleistocene and Holocene, alkaline and tholeiitic magmas were erupted in the Zuni-Bandera volcanic field (ZBVF) on the western flanks of the Rio Grande Rift, New Mexico. While most of the alkaline basalts are magnesian (i.e., >8.0% MgO), the tholeiitic basalts show evidence of fractionation of olivine and clinopyroxene. The ZBVF lavas have intraplate chemistry similar to that of alkaline and tholeiitic basalts in other continental and oceanic environments, and Sr and Nd isotopes range from depleted compositions similar to mid-ocean ridge basalts to enriched compositions similar to ocean islands like Kerguelen. Slightly higher Th/Ta and Ba/Nb ratios in some of the ZBVF tholeiitic basalts correlate with isotopic ratios, and this may indicate minor involvement of a Th rich component (i.e., crust). Alternatively, such characteristics may merely reflect intraplate processes if one considers that the isotopic variation observed in the ZBVF is not that different from what is observed in Hawaiian basalts. Systematic changes in elemental and isotopic ratios with the degree of partial melting (Zr/Y) reveal that the geochemistry of the ZBVF magmas is dominated by two components: (1) a depleted mantle component which produced an enriched alkaline magma as a small degree melt (e.g., Ta/Yb=6.0; {La/Yb}N=60; Zr/Y=19; 87Sr/86Sr=0.703); and (2) an enriched mantle component which produced tholeiitic magmas as a larger degree melt (e.g., Ta/Yb <0.5{La/Yb}N < 15.0; Zr/Y=3-4; 87Sr/86Sr = 0.706). While the depleted component is interpreted to be MORB asthenosphere the enriched component is more problematical and may reside in plume-contaminated asthenosphere or stratified lithosphere. The lower lithosphere beneath the Proterozoic crust of the western USA appears to be chemically stratified and comprises a depleted peridotite protolith stabilized in the Proterozoic that may have been subsequently enriched due to interaction with fluids related to (1) suprasubduction processes

  19. New Insights for Detecting and Deriving Thermal Properties of Lava Flow Using Infrared Satellite during 2014–2015 Effusive Eruption at Holuhraun, Iceland

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    Muhammad Aufaristama

    2018-01-01

    Full Text Available A new lava field was formed at Holuhraun in the Icelandic Highlands, north of Vatnajökull glacier, in 2014–2015. It was the largest effusive eruption in Iceland for 230 years, with an estimated lava bulk volume of ~1.44 km3 covering an area of ~84 km2. Satellite-based remote sensing is commonly used as preliminary assessment of large scale eruptions since it is relatively efficient for collecting and processing the data. Landsat-8 infrared datasets were used in this study, and we used dual-band technique to determine the subpixel temperature (Th of the lava. We developed a new spectral index called the thermal eruption index (TEI based on the shortwave infrared (SWIR and thermal infrared (TIR bands allowing us to differentiate thermal domain within the lava flow field. Lava surface roughness effects are accounted by using the Hurst coefficient (H for deriving the radiant flux ( Φ rad and the crust thickness (Δh. Here, we compare the results derived from satellite images with field measurements. The result from 2 December 2014 shows that a temperature estimate (1096 °C; occupying area of 3.05 m2 from a lava breakout has a close correspondence with a thermal camera measurement (1047 °C; occupying area of 4.52 m2. We also found that the crust thickness estimate in the lava channel during 6 September 2014 (~3.4–7.7 m compares closely with the lava height measurement from the field (~2.6–6.6 m; meanwhile, the total radiant flux peak is underestimated (~8 GW compared to other studies (~25 GW, although the trend shows good agreement with both field observation and other studies. This study provides new insights for monitoring future effusive eruption using infrared satellite images.

  20. Flowing and growing: a microanalytical and isotopic investigation of a large volume rhyolite lava flow at Yellowstone

    Science.gov (United States)

    Severin, Z.; Bindeman, I. N.; Lackey, J.

    2013-12-01

    Why large-volume rhyolitic magmas with identical properties and volatile budgets erupt as both pyroclastic rocks forming calderas, and quiet lava flows, has remained a long standing question at Yellowstone and volcanic centers worldwide. We have investigated the youngest lava flow of Yellowstone - the Central Plateau member (0.2-0.07 Ma) in attempt to better understand the following aspects of a large-volume (≤54 km^3) lava flow: 1) how long it takes to erupt; 2) how chemically and isotopically homogenous it is; and 3) how syneruptive cooling affects isotopic and chemical composition. We also analyze the homogeneity of the 112 ka, 37 km^3, low-δ^18O Summit Lake lava flow, which formed by remelting of hydrothermally altered and buried materials. On the surface twenty samples were collected along a southwest-northeast transect from the flow vent to the lava flow edge. We examined these samples petrographically and chemically, employing whole rock geochemistry, the titanium content of quartz phenocrysts to calculate relative temperature of growth using the Ti-in-quartz thermometer (TitaniQ), and the δ^18O of volcanic glass. The Ti content of quartz is useful for inferring the temperature, pressure, and/or chemical conditions of quartz crystallization. We also used cathodoluminescence imaging (CL) on a scanning electron microscopy (SEM) to distinguish quartz cores from overgrowths. Values of δ^18O are relatively homogeneous across the flow (4.60 × 0.59‰, n=20), showing no systematic variation with distance from the vent. Whole-rock major element composition is also homogenous across the flow (SiO2 = 75.08-77.03 wt.%). However, precise grid-counting reveals a general increase in the percent of phenocrysts (4.4-7.3%) and also the ratio of quartz to feldspar (40:60). CL shows that all quartz phenocrysts display a renewed growth as a dark ~200 μm-thick rims upon by bright cores. Among the quartz phenocrysts, Ti generally decreases from 139×39 ppm in bright cores

  1. Geochemistry of pillow lavas and sheeted dikes from Nain and Ashin ophiolites (Central Iran)

    Science.gov (United States)

    Saccani, Emilio; Pirnia Naeini, Tahmineh; Torabi, Ghodrat

    2017-04-01

    An extensive, worldwide database on the geochemistry of basalts from well-known tectonic settings is available. Knowing the chemistry of basalts on one hand, and the tectonic setting of their origin on the other hand, resulted in the development of tectonic discrimination diagrams. Recently developed discrimination diagrams allow us to determine the tectonic setting of volcanics with almost neglectable probability of misclassification (pillow lavas and sheeted dikes from two ophiolite mélanges of Central Iran, Nain and Ashin ophiolites. The two mélanges are located in the west of Central-East Iranian microplate. In total, 28 samples have been collected from the pillow lavas and sheeted dikes outcrops. The studied volcanic rocks consist mainly of basalts and minor ferrobasalts and basaltic andesites, all showing a clear subalkaline nature (e.g., Nb/Y = 0.03-0.21). Two samples from the Nain ophiolite are characterized by N-MORB normalized incompatible element patterns showing marked Th positive anomalies and Ta, Nb, Ti negative anomalies. Chondrite-normalized REE patterns show LREE/HREE (light REE/heavy REE) enrichment, with LaN/YbN=3.2-4.3. These rocks are chemically similar to the calc-alkaline basalts (CAB), as also highlighted by many discrimination diagrams. These rocks are interpreted to have generated in a cordilleran-type volcanic arc setting. All other samples from both the Nain and Ashin ophiolites display a wide range of chemical composition. However, the relatively less fractionated basalts are characterized by low TiO2 (0.60-1 wt%), P2O5 (0.03-0.08 wt%), Zr (23-75 ppm) and Y (9-27) contents. Cr (38-619 ppm) and Ni (22-220 ppm) contents show a wide range of variation. N-MORB normalized incompatible element patterns show rather flat trends and a general depletion (from 0.4 to 0.8 times N-MORB composition) coupled with a slight Th enrichment (1-3 times N-MORB). Chondrite-normalized REE patterns are generally flat and are characterized by either a slight

  2. A model of the geochemical and physical fluctuations of the lava lake at Erebus volcano, Antarctica

    Science.gov (United States)

    Molina, Indira; Burgisser, Alain; Oppenheimer, Clive

    2015-12-01

    Erebus volcano, Antarctica, exhibits periodical surface fluctuations of both geochemical and physical nature. Modeling the physics driving the lake oscillation is a challenge, even with a relatively simple theoretical framework. We present a quantitative analysis that aims to reconcile both lake level and gas geochemical cycles. Our model is based on the assumption that the periodicity is caused by the regular release of magma batches and/or core annular flow that have a fixed volume of melt and ascend and degas in equilibrium. Results suggest that cycles are not caused by the mixing between magma residing in the lake and a deep magma but by two distinct deep sources that rise separately. These sources of bubbly magma come from at most 2-3 km depth and rise buoyantly. Individual batches detach from the rising magmas at depths of 20-250 m. The two batch types can coexist in a single conduit up to a depth of 30 m, above which they rise alternately to release respectively 19 and 23 kg/s of gas at the lake surface every 10 min. The temperature of the descending flow is between 890 and 950 °C, which is roughly 100 °C colder than the ascending currents. Batch pairs have shapes likely constrained by the conduit width. Regardless of their shapes, the pairs reach very high porosities near the surface and have diameters of 4-14 m that are consistent with video observations showing spreading waves at the lake surface. The alternating arrival of these large batches suggests a lava lake mostly filled with gas-rich magma.

  3. Geochemistry of tertiary-quaternary lavas of Mt. Oku Northwest Cameroon

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    Njilah Konfor

    2007-01-01

    Full Text Available El Monte Oku ocupa la posición central en el sector continental de los volcanes de la Línea Volcánica de Camerún (CVL. Las observaciones del terreno, petrográfica mayor, huella y REE geoquímica, indican que esas lavas son basanita/basalto alcalino trachita/reolita junto al boquete composicional dentro del terreno benmoreita. Este boquete, que no se puede explicar por diagonal de muestreo, puede por lo tanto reflejar la densidad de filtración dentro del sistema magmático. Sin embargo, la acumulación y la fragmentación de las mayores fases minerales: piroxenas, olivinos y plagioclasa, parecen haber controlado la evolución del magma. La cristalización ha mostrado ser el mayor proceso de diferenciación que da a lugar al espectro de los magmas de este estrato-volcán, aunque la contaminación cortical en el nivel superior de las cámaras del magma no puede ser impedida en este medio continental intra-plato. Las determinaciones K-Ar age indican que la actividad volcánica del Monte Oku ocurrió en tres episodios precisos, 25-22 Ma, 18-14 Ma y < 1 Ma. No hay evidencia de actividad volcánica entre 14 y 1 Ma. Para edades < 1 Ma BP, la actividad volcánica fue reasumida creando conos y cráteres abundantes.

  4. The hottest lavas of the Phanerozoic and the survival of deep Archean reservoirs

    Science.gov (United States)

    Gazel, Esteban; Trela, Jarek; More, Lowell; Alex, Sobolev; Bizimis, Michael; Jicha, Brian

    2017-04-01

    The mantle plume hypothesis is widely accepted for the formation of large igneous provinces and many modern day hotspot volcanoes. Petrologic models suggest that plume-derived melts originate at high mantle temperatures (>1500 °C) relative to those generated at ambient mid-ocean ridge conditions ( 1350 °C). Earth's mantle has also cooled during its history due to heat loss and decrease in radioactive heat production, thus the temperatures of modern day basalts are substantially lower than those produced during the Archean (>2.5 Ga), as recorded by komatiites (>1700 °C). We discovered that the 90 Ma Galapagos-related Tortugal Suite accreted in Costa Rica not only record mantle potential temperatures as high as ancient Archean komatiites ( 1800 °C), but we also collected the highest olivine-spinel crystallization temperatures ever reported in the literature (1600 °C). Therefore, to the best of our knowledge, this suite represents the record of the hottest lavas of the Phanerozoic. These type of magmas occurred more frequently during the Archean due to overall higher ambient mantle temperatures, yet our data suggest that anomalously hot, isolated domains still exist in the deep portions of the planet that have survived billions of years of mantle convection and cooling. This finding is in line with the recent results that showed that early-formed 182W/184W mantle heterogeneities, produced during the first 50 million years of planetary accretion, survived to present time and has been sampled by mantle plumes. Our finding supports the existence of primitive Archean reservoirs, although in most plumes cooler ambient mantle entrainment probably dilutes its temperature signature.

  5. Isotopic constraints on the genesis and evolution of basanitic lavas at Haleakala, Island of Maui, Hawaii

    Science.gov (United States)

    Phillips, Erin H.; Sims, Kenneth W. W.; Sherrod, David R.; Salters, Vincent J. M.; Blusztajn, Jurek; Dulai, Henrietta

    2016-12-01

    To understand the dynamics of solid mantle upwelling and melting in the Hawaiian plume, we present new major and trace element data, Nd, Sr, Hf, and Pb isotopic compositions, and 238U-230Th-226Ra and 235U-231Pa-227Ac activities for 13 Haleakala Crater nepheline normative basanites with ages ranging from ∼900 to 4100 yr B.P. These basanites of the Hana Volcanics exhibit an enrichment in incompatible trace elements and a more depleted isotopic signature than similarly aged Hawaiian shield lavas from Kilauea and Mauna Loa. Here we posit that as the Pacific lithosphere beneath the active shield volcanoes moves away from the center of the Hawaiian plume, increased incorporation of an intrinsic depleted component with relatively low 206Pb/204Pb produces the source of the basanites of the Hana Volcanics. Haleakala Crater basanites have average (230Th/238U) of 1.23 (n = 13), average age-corrected (226Ra/230Th) of 1.25 (n = 13), and average (231Pa/235U) of 1.67 (n = 4), significantly higher than Kilauea and Mauna Loa tholeiites. U-series modeling shows that solid mantle upwelling velocity for Haleakala Crater basanites ranges from ∼0.7 to 1.0 cm/yr, compared to ∼10 to 20 cm/yr for tholeiites and ∼1 to 2 cm/yr for alkali basalts. These modeling results indicate that solid mantle upwelling rates and porosity of the melting zone are lower for Hana Volcanics basanites than for shield-stage tholeiites from Kilauea and Mauna Loa and alkali basalts from Hualalai. The melting rate, which is directly proportional to both the solid mantle upwelling rate and the degree of melting, is therefore greatest in the center of the Hawaiian plume and lower on its periphery. Our results indicate that solid mantle upwelling velocity is at least 10 times higher at the center of the plume than at its periphery under Haleakala.

  6. Magma storage and evolution in the Henties Bay-Outjo dyke swarm, Namibia -feeder systems of the Etendeka lavas

    Science.gov (United States)

    Keiding, J. K.; Frei, O.; Renno, A.; Veksler, I. V.; Trumbull, R. B.

    2012-04-01

    At the roots of continental flood basalts in the Paraná-Etendeka province are mafic dyke swarms that cover areas of several hundred kilometers. Studies of these dykes have focused mainly on the age, paleomagnetic properties and geochemistry, but less on pressure (P) and temperature (T) conditions of emplacement. However, the P and T conditions under which dyke magmas are stored are crucial for models of magma plumbing systems in flood basalt provinces. The erupted lavas are typically far from primitive compositions and generally show evidence for strong crustal assimilation in addition to magma fractionation. Unknown is where this magma modification took place in the crust. This is the kind of information that dyke studies can provide. The Henties Bay Outjo dyke swarm (HOD) in NW Namibia is the subject of this study. This is inarguably the best exposed of major dyke swarms associated with South Atlantic rifting and breakup and its geochemical diversity is well documented but aspects relating to the magma dynamics in the dyke swarm have not been studied before. Our approach is to use geochemical data from selected dykes to assess the differentiation and assimilation history of the magmas, and combine that with petrologic constraints on the temperature-pressure conditions of crystallization derived from mineral-melt equilibria. We have determined P-T estimates from olivine-melt and clinopyroxene-melt equilibria using analysis of phenocrysts by electron microprobe and applying the thermodynamic relations from Putirka (2008), who considered the standard error to be 1.7 kbar and 30°C. The calculations reflect only mineral-melt (proxied by whole-rock) compositions that are consistent with equilibrium. Crystallization temperatures range from 1040°C to 1350°C with a mean (n=58) of 1170 °C. These T-variations are not random, the high-temperature results come from a specific region of dyke emplacement but the reason for this is not yet clear. Olivine-melt temperatures

  7. Synergistic use of Thermal Infrared Satellite and Field-Based Data to Understand Silicic Lava Emplacement Processes

    Science.gov (United States)

    Ramsey, M. S.

    2004-05-01

    Intermediate to silicic lava domes commonly found capping active volcanic conduits can preserve an enormous quantity of information on the system's activity state. Such data could include the pressure, temperature, flow rate, and degassing state of the lava as it is extruded. Further, similar lavas found on inactive systems can serve as analogs for active domes thereby mitigating potentially hazardous field work while validating models. The clear objective is to collect data and refine models/techniques at the inactive sites so as to better understand the data from active systems, which reveal the potential hazard state of the volcano. However, in order to study both systems under similar conditions, a set of data collection techniques must be equally applicable to both. One obvious choice is remote sensing, which mitigates hazards to scientists in the field, can be collected relatively cheaply under most conditions, and can be an effective monitoring tool. In the past several years, new airborne and space-based instruments have provided data in multiple wavelength regions never before collected over volcanic flows and domes. One of the most promising satellite instruments for volcanology is the ASTER instrument launched by NASA in late 1999. Because it is the first spaceborne sensor to acquire high spatial resolution data from the visible to thermal infrared (TIR) wavelength region and has the ability to generate digital elevation models, it is particularly useful for numerous aspects of volcanic remote sensing. For example, its multispectral TIR capability is critical for monitoring low temperature anomalies and mapping both chemical and textural variations on the dome surfaces. However, the ability to derive this level of quantitative information currently relies on accurate field based data collection, laboratory modeling, and the development of new computer-based tools. Over the past three years, ASTER data acquired over the active dome-forming eruptions of

  8. Combining very-long-range terrestrial laser scanner data and thermal imagery for analysis of active lava flow fields

    Science.gov (United States)

    James, Mike; Pinkerton, Harry; Applegarth, Jane

    2010-05-01

    In order to increase our understanding of the processes involved in the evolution of lava flow fields, detailed and frequent assessments of the activity and the topographic change involved are required. Although topographic data of sufficient accuracy and resolution can be acquired by airborne lidar, the cost and logistics generally prohibit repeats at the daily (or more frequent) intervals necessary to assess flow processes. More frequent surveys can be carried out using ground-based terrestrial laser scanners (TLSs) but on volcanic terrain such instruments generally have ranges of only several hundreds of metres, with long range variants extending to ~1100 m. Here, we report preliminary results from the use of a new, ground-based Riegl LPM-321 instrument with a quoted maximum range of 6000 m. The LPM-321 was deployed at Mount Etna, Sicily during July 2009. At this time, active lava flows from the waning 2008-9 eruption were restricted to the upper region of a lava delta that had accumulated over the course of the eruption. Relatively small (a few hundreds of metres in length) and short lived (of order a few days) flows were being effused from a region of tumuli at the head of the delta. The instrument was used from three locations, Schiena dell' Àsino, the head of the Valle del Bove and Pizzi Deneri. From Schiena dell' Àsino, most of the 2008-9 lava flows could be observed, but, due to low reflectivities and viewing distances of ~4500 m, the active regions of the flows were out of range. The longest return was acquired from a range of 3978 m, but successful returns at this range were sparse; for dense topographic data, data were best acquired over distances of less than ~3500 m. The active flows were successfully imaged from the head of the Valle del Bove (9 and 12 July, 2009) and Pizzi Deneri (6 July, 2009). Despite low effusion rates (~1 m3s-1), topographic change associated with the emplacement and inflation of new flows and the inflation of a tumulus was

  9. The Use of Surveillance Cameras for the Rapid Mapping of Lava Flows: An Application to Mount Etna Volcano

    Directory of Open Access Journals (Sweden)

    Mauro Coltelli

    2017-02-01

    Full Text Available In order to improve the observation capability in one of the most active volcanic areas in the world, Mt. Etna, we developed a processing method to use the surveillance cameras for a quasi real-time mapping of syn-eruptive processes. Following an evaluation of the current performance of the Etna permanent ground NEtwork of Thermal and Visible Sensors (Etna_NETVIS, its possible implementation and optimization was investigated to determine the locations of additional observation sites to be rapidly set up during emergencies. A tool was then devised to process time series of ground-acquired images and extract a coherent multi-temporal dataset of georeferenced map. The processed datasets can be used to extract 2D features such as evolution maps of active lava flows. The tool was validated on ad-hoc test fields and then adopted to map the evolution of two recent lava flows. The achievable accuracy (about three times the original pixel size and the short processing time makes the tool suitable for rapidly assessing lava flow evolutions, especially in the case of recurrent eruptions, such as those of the 2011–2015 Etna activity. The tool can be used both in standard monitoring activities and during emergency phases (eventually improving the present network with additional mobile stations when it is mandatory to carry out a quasi-real-time mapping to support civil protection actions. The developed tool could be integrated in the control room of the Osservatorio Etneo, thus enabling the Etna_NETVIS for mapping purposes and not only for video surveillance.

  10. A geomagnetic field model for the Holocene based on archaeomagnetic and lava flow data

    Science.gov (United States)

    Pavón-Carrasco, Francisco Javier; Osete, María Luisa; Torta, Joan Miquel; De Santis, Angelo

    2014-02-01

    We propose a new geomagnetic field model for the Holocene period based on archaeomagnetic and lava flow data, avoiding the use of lake sediment data. The source of data comes from the GEOMAGIA50v2 database which has been updated with the new archaeomagnetic and volcanic studies published during the last 3 yr. The model, called SHA.DIF.14k, allows us to analyse the behaviour of the geomagnetic field for the last 14 000 yr: from 12 000 BC to 1900 AD. For the model construction we use the spherical harmonic analysis in space and the penalized cubic B-splines in time. Both spatial and temporal regularization norms are used to constrain the inversion problem and applied at the core-mantle boundary (CMB) to assure the convergence of the model. For the last 3 ka, the model predictions agree with those given by the global model ARCH3k.1 and the European model SCHA.DIF.3k. For older epochs, the new model presents a clear improvement in field resolution with respect to other current models of the geomagnetic field for the Holocene. For the last 9 ka, the time evolution of the dipolar moment obtained from the dipole field shows a clear minimum between 5500 BC and 3000 BC, and the well-known continuous decreasing trend of the geomagnetic field strength for the last millennium and a half. A general view of the time-average evolution of the geomagnetic field flux lobes at the CMB for the northern hemisphere suggests a marked lobe of positive magnetic flux when the dipole moment was maximum. This lobe vanishes when the dipolar field is decreasing. The north polar wander paths of both north magnetic dip and geomagnetic poles were obtained showing an average rate of motion of 5.1 km/yr and 3.7 km/yr respectively. The model shows that the geomagnetic field can be averaged as axial dipolar in ˜2000 yr within an error of 5°, the typical uncertainty of the palaeomagnetic studies. Finally, and following the recent definition of archaeomagnetic jerks, we found 8 critical events in the

  11. Isotopic constraints on the genesis and evolution of basanitic lavas at Haleakala, Island of Maui, Hawaii

    Science.gov (United States)

    Phillips, Erin H.; Sims, K.W.W.; Sherrod, David R.; Salters, Vincent; Blusztajn, Jurek; Dulaiova, Henrieta

    2016-01-01

    To understand the dynamics of solid mantle upwelling and melting in the Hawaiian plume, we present new major and trace element data, Nd, Sr, Hf, and Pb isotopic compositions, and 238U–230Th–226Ra and 235U–231Pa–227Ac activities for 13 Haleakala Crater nepheline normative basanites with ages ranging from ∼900 to 4100 yr B.P. These basanites of the Hana Volcanics exhibit an enrichment in incompatible trace elements and a more depleted isotopic signature than similarly aged Hawaiian shield lavas from Kilauea and Mauna Loa. Here we posit that as the Pacific lithosphere beneath the active shield volcanoes moves away from the center of the Hawaiian plume, increased incorporation of an intrinsic depleted component with relatively low 206Pb/204Pb produces the source of the basanites of the Hana Volcanics. Haleakala Crater basanites have average (230Th/238U) of 1.23 (n = 13), average age-corrected (226Ra/230Th) of 1.25 (n = 13), and average (231Pa/235U) of 1.67 (n = 4), significantly higher than Kilauea and Mauna Loa tholeiites. U-series modeling shows that solid mantle upwelling velocity for Haleakala Crater basanites ranges from ∼0.7 to 1.0 cm/yr, compared to ∼10 to 20 cm/yr for tholeiites and ∼1 to 2 cm/yr for alkali basalts. These modeling results indicate that solid mantle upwelling rates and porosity of the melting zone are lower for Hana Volcanics basanites than for shield-stage tholeiites from Kilauea and Mauna Loa and alkali basalts from Hualalai. The melting rate, which is directly proportional to both the solid mantle upwelling rate and the degree of melting, is therefore greatest in the center of the Hawaiian plume and lower on its periphery. Our results indicate that solid mantle upwelling velocity is at least 10 times higher at the center of the plume than at its periphery under Haleakala.

  12. The Central Atlantic Magmatic Province: Age Comparison Between the South Carolina Dykes and Morocco Lava Flows

    Science.gov (United States)

    Youbi, N.; Nomade, S.; Breutel, E.; Knight, K.

    2003-12-01

    Believed to be the largest volcanic province on Earth at more than 6000 km long and 2000 km wide, the Central Atlantic Magmatic Province (CAMP) stretches from Eastern Canada to Brazil and from Western Spain to the Ivory Coast. Due to the massive erosion and subsequent in filling of these areas since the 200 Ma rifting event, dikes and sills constitute the majority of the exposed CAMP volcanics. However, well preserved lava flows have been found in the Triassic basins of the Northeastern United States and Morocco. Despite numerous 40Ar/39Ar dating attempts, very few of the exposed CAMP volcanics have been successfully dated due to a variety of factors including; excess argon and alteration. Especially no age is available in the well-mapped but structurally complex South and North Carolina dykes swarm as well as only few scattered ages in the Moroccan Trias-Liassic basins. Our goal is to better constrain the emplacement timing of the dykes swarm but also to compare age of both intrusive and effusive rocks from the same magmatic event but separated from more than 1000 km, 200 Mys ago. Several questions continue to surround the CAMP volcanic province including its cause and emplacement mechanism. Toward that end we have collected and dated dyke samples from the Carolinas and flows in Morocco, 1000 km away and across the rift. We anticipate that a comparison of these dates will enable us to understand more about the timing between the emplacement of the flows and dykes. We have collected in South Carolina and High Atlas in Morocco 7 and 9 hand samples respectively. Specimens from South Carolina correspond to the three distinct dykes' direction NE-SW, NW-SE and NS. In Morocco, samples were collected in four sections (100 to 300 m thick) located in the High Atlas between Marrakech and Ouarzazate. From each hand sample two different transparent plagioclase fractions, 250-180 and 180 to 100 microns, were separated. We have performed step heating experiments at the Berkeley

  13. Analysis of Hydrogen Isotopic Exchange: Lava Creek Tuff Ash and Isotopically Labeled Water

    Science.gov (United States)

    Ross, A. M.; Seligman, A. N.; Bindeman, I. N.; Nolan, G. S.

    2015-12-01

    Nolan and Bindeman (2013) placed secondarily hydrated ash from the 7.7 ka eruption of Mt. Mazama (δD=-149‰, 2.3wt% H2Ot) in isotopically labeled water (+650 ‰ δD, +56 ‰ δ18O) and observed that the H2Ot and δ18O values remained constant, but the δD values of ash increased with the surrounding water at 20, 40 and 70 °C. We expand on this work by conducting a similar experiment with ash from the 640 ka Lava Creek Tuff (LCT, δD of -128 ‰; 2.1 wt.% H2Ot) eruption of Yellowstone to see if significantly older glass (with a hypothesized gel layer on the surface shielding the interior from alteration) produces the same results. We have experiments running at 70, 24, and 5 °C, and periodically remove ~1.5 mg of glass to measure the δD (‰) and H2Ot (wt.%) of water extracted from the glass on a TC/EA MAT 253 continuous flow system. After 600 hours, the δD of the samples left at 5 and 24 °C remains at -128 ‰, but increased 8‰ for the 70 °C run series. However, there is no measurable change in wt.% of H2Ot, indicating that hydrogen exchange is not dictated by the addition of water. We are measuring and will report further progress of isotope exchange. We also plan to analyze the water in the LCT glass for δ18O (‰) to see if, as is the case for the Mt. Mazama glass, the δ18O (‰) remains constant. We also analyzed Mt. Mazama glass from the Nolan and Bindeman (2013) experiments that have now been sitting in isotopically labeled water at room temperature for ~5 years. The water concentration is still unchanged (2.3 wt.% H2Ot), and the δD of the water in the glass is now -111 ‰, causing an increase of 38 ‰. Our preliminary results show that exchange of hydrogen isotopes of hydrated glass is not limited by the age of the glass, and that the testing of hydrogen isotopes of secondarily hydrated glass, regardless of age, may not be a reliable paleoclimate indicator.

  14. Changes in Mass Flux of Tephra from the Lava Lake in Overlook Crater, Kīlauea Volcano, Hawai`i

    Science.gov (United States)

    Swanson, D. A.; Orr, T. R.; Patrick, M. R.

    2016-12-01

    The mass flux of tephra (mostly Pele's hair and tears, hollow spherules, and lithic clasts) from the lava lake in Overlook crater varies on short (seconds-minutes), intermediate (hours-days), and long (months) time scales. The tephra is collected almost daily from a network of 10 buckets within 400 m of, and 100-150 m above, the lava lake; bucket locations have not changed during the eruption. A mass accumulation rate (AR) is calculated for the network; since April 2008, the AR averages 0.17 g/m2/h ( 5×10-8 kg/m2/s). The tephra forms during almost constant spattering at the SE sink (the main downwelling site) and ephemeral sites along the crater wall, as well as from sporadic, rockfall-induced violent outgassing that can eject decimeter-size spatter clots onto the crater rim; the average AR excludes these violent events. The rockfalls, and nearly constant raveling from the crater wall, introduce lithic clasts into the tephra. The lithic content of the tephra has decreased with time, reflecting both greater wall stability and higher lake level, and was usually 7 m/s). At intermediate and long time scales, juvenile AR shows no correlation with measured SO2 output and only weak or no correlation with wind speed, but it often tracks the elevation of the lake surface—higher when lava is nearer the buckets. For example, both lava level and juvenile AR were unusually high in January-July 2016. Before 2016, however, 7-9 periods of heightened juvenile production (see figure below), each lasting several months, show no correlation with other monitored parameters—lake level, SO2, wind speed and direction, or downwelling location. Often AR gradually increased to a peak before falling off, sometimes to nearly zero. We speculate that such long-term variations result from changes in magma supply rate, gas concentration, or rise frequency of decoupled gas slugs. These changes may be too small or slow to detect by current geodetic and gas monitoring. They suggest a slowly

  15. Community preparedness for lava flows from Mauna Loa and Hualālai volcanoes, Kona, Hawai'i

    Science.gov (United States)

    Gregg, Chris E.; Houghton, Bruce F.; Paton, Douglas; Swanson, Donald A.; Johnston, David M.

    2004-01-01

    Lava flows from Mauna Loa and Huala??lai volcanoes are a major volcanic hazard that could impact the western portion of the island of Hawai'i (e.g., Kona). The most recent eruptions of these two volcanoes to affect Kona occurred in A.D. 1950 and ca. 1800, respectively. In contrast, in eastern Hawai'i, eruptions of neighboring Ki??lauea volcano have occurred frequently since 1955, and therefore have been the focus for hazard mitigation. Official preparedness and response measures are therefore modeled on typical eruptions of Ki??lauea. The combinations of short-lived precursory activity (e.g., volcanic tremor) at Mauna Loa, the potential for fast-moving lava flows, and the proximity of Kona communities to potential vents represent significant emergency management concerns in Kona. Less is known about past eruptions of Huala??lai, but similar concerns exist. Future lava flows present an increased threat to personal safety because of the short times that may be available for responding. Mitigation must address not only the specific characteristics of volcanic hazards in Kona, but also the manner in which the hazards relate to the communities likely to be affected. This paper describes the first steps in developing effective mitigation plans: measuring the current state of people's knowledge of eruption parameters and the implications for their safety. We present results of a questionnaire survey administered to 462 high school students and adults in Kona. The rationale for this study was the long lapsed time since the last Kona eruption, and the high population growth and expansion of infrastructure over this time interval. Anticipated future growth in social and economic infrastructure in this area provides additional justification for this work. The residents of Kona have received little or no specific information about how to react to future volcanic eruptions or warnings, and short-term preparedness levels are low. Respondents appear uncertain about how to respond

  16. Magnetostratigraphy and 40Ar/39Ar dating of CAMP lava flows at the Triassic-Jurassic boundary, Morocco

    Science.gov (United States)

    Knight, K. B.; Nomade, S.; Renne, P.; Marzoli, A.; Youbi, N.

    2003-04-01

    The Central Atlantic Magmatic Province (CAMP), the largest known flood basalt province in the Phanerozoic, is generally associated with the incipient opening of the Atlantic Ocean at the Triassic-Jurassic boundary ca. 200 Ma. Paleomagnetic sampling targeted packages of CAMP lava flows in central Morocco from condensed sections identified on the basis of field observations and geochemistry. Lava flows in Moroccan CAMP are divided into four basic units, each comprising multiple flows (after Bertrand, 1991): the Formation (Fm.) Inférieure, Fm. Intermédiaire, Fm. Supérieure, and at the top, the Récurrente, separated from the first three by a period of red clay deposition. Oriented cores were demagnetized using both alternating field (AF) and thermal techniques. Cores from the same lava flow processed by AF demagnetization were later crushed for subsequent separation of plagioclase and dated by the 40Ar/39Ar method. Paleomagnetic results reveal wholly normal polarity interrupted by a brief reversal event defined by data from a single flow located at the base of the Fm. Intermédiaire. Preliminary results from a 250 m section of lavas spanning three formations in the Haut Atlas of Morocco confirm the presence of this brief reversal. 40Ar/39Ar analyses of these samples yielded six plateau ages including each formation. These ages are indistinguishable within 2σ error limits, sharing a mean age of 200.9 ± 0.7 Ma (2σ) relative to the Fish Canyon sanidine at 28.02 Ma (Renne et al., 1998). This demonstrates the brevity of these eruptions despite the presence of significant sedimentary horizons between them. These ages are slightly older than the average elsewhere around Pangea, suggesting CAMP volcanism initiated in Morocco and may span the Triassic-Jurassic transition. Correlation of our observed reversal with the E23n, E23r, E24 sequence reported in the Newark basin (Olsen et al., 2003) would further support this. These new data also contribute to the

  17. Constraints on the causes of the High Lava Plains volcanism from inversions of surface wave phase and amplitude data

    Science.gov (United States)

    Wagner, L. S.; Forsyth, D.; Fouch, M. J.

    2008-12-01

    The High Lava Plains (HLP) of southeastern and central Oregon is a province of bimodal volcanic activity which postdates the voluminous flood basalts of the Columbia River area. The north-westerly trend of the rhyolitic volcanism of the HLP lies at an oblique angle to the north-easterly trend of the silicic volcanism associated with the Snake River Plain and Yellowstone caldera, though both volcanic tracks originated at the same place and time in southeastern Oregon some 15 Ma. While the Snake River Plain's volcanism has often been associated with the possible existence of a Yellowstone hot spot due to its alignment with North American plate motion, the High Lava Plains volcanism defies such a simple explanation. Possible contributing factors in the formation of the High Lava Plains include the subducting Juan de Fuca plate to the east and its effects on mantle dynamics, the effects of varying lithospheric thickness throughout the area, and the debated existence of a Yellowstone plume head and/or tail. We present results of a preliminary tomographic inversion of Rayleigh wave phase and amplitude using the method of Forsyth and Li [2005] to constrain phase velocities and shear wave velocities in the area of the High Lava Plains. Data for this inversion are provided by a temporary array of broadband seismometers deployed in the region beginning in 2006 by Arizona State University and the Carnegie Institution of Washington. As of summer 2008, 104 stations were operating as part of the HLP seismic experiment, in addition to the broadband stations operated here as part of the USArray Transportable Array (TA). Preliminary results include waveforms from ~50 large events recorded at an average of >90 stations. The method of Forsyth and Li [2005] used in this inversion employs a 2-plane-wave approximation of the incoming surface waves. The improvements in lateral resolution of this methodology over previous phase velocity inversions is significant, and helps constrain the

  18. Difficulties in Forecasting Flow Paths During the 2014-2015 Lava Flow Crisis at Kīlauea Volcano (Hawaíi)

    Science.gov (United States)

    Patrick, M. R.; Orr, T. R.; Trusdell, F.; Llewellin, E. W.; Kauahikaua, J. P.

    2015-12-01

    Kīlauea's East Rift Zone (ERZ) eruptive activity at Púu ´Ō´ō shifted to a new vent in June 2014, sparking a lava flow crisis that threatened critical infrastructure near the town of Pāhoa in east Hawaíi. The lava flow proved to be challenging to forecast because of the influence of ground cracks on flow direction, frequent fluctuations in lava supply, and the subtle interplay between ground slope and confining topography that prevented the flow from spreading laterally. After its onset, the "June 27th" flow, named informally for its start date, advanced northeast at up to several hundred m/day. The flow's path through heavy forest was forecast using steepest-descent paths derived from a digital elevation model (DEM). Flow path uncertainties were minimized using a multiple-run technique and built-in random DEM errors (modified from Favalli et al., 2005). In mid-August, the flow encountered and entered one of many deep, discontinuous ground cracks along Kīlauea's middle ERZ. The flow continued to advance out of sight in the crack, as inferred from a forward-progressing line of steam. A week later, lava spilled from the crack 1.3 km downslope, advancing along a different flow path than was forecast. By early September, the flow had entered and exited three more cracks sequentially, carrying the flow across slope, thus making flow path forecasts unreliable. Moreover, lava-occupied cracks dilated by up to 3 m. The lava accumulating in the ground cracks forced immense, but apparently mobile, blocks to shift. Thus, while an open crack was required to capture the lava, the lava was able to force its way beyond where the crack closed. In this way, the lava flow acted as an intruding dike. The flow eventually advanced beyond the area of cracks and onto a steepest-descent path that guided the flow toward the town of Pāhoa, where it destroyed one house, reached to within ~155 m of the main street in Pāhoa, and threatened the main highway and shopping center serving

  19. Thermal Modeling of Permafrost Melt by Overlying Lava Flows with Applications to Flow-associated Outflow Channel Volumes in the Cerberus Plains, Mars

    Science.gov (United States)

    Chase, Z. A. J.; Sakimoto, S. E. H.

    2003-01-01

    The Cerberus region of Mars has numerous geologically recent fluvial and volcanic features superimposed spatially, with some of them using the same flow channels and apparent vent structures. Lava-water interaction landforms such as psuedocraters suggest some interaction of emplacing lava flows with underlying ground ice or water. This study investigates a related interaction type a region where the emplaced lava might have melted underlying ice in the regolith, as there are small outflow channel networks emerging from the flank flows of a lava shield over a portion of the Eastern Cerberus Rupes. Specifically, we use high-resolution Mars Orbiter Laser Altimeter (MOLA) topography to constrain channel and flow dimensions, and thus estimate the thermal pulse from the emplaced lava into the substrate and the resulting melting durations and refreezing intervals. These preliminary thermal models indicate that the observed flows could easily create thermal pulse(s) sufficient to melt enough ground ice to fill the observed fluvial small outflow channels. Depending on flow eruption timing and hydraulic recharge times, this system could easily have produced multiple thermal pulses and fluvial releases. This specific case suggests that regional small water releases from similar cases may be more common than suspected, and that there is a possibility for future fluvial releases if ground ices are currently present and future volcanic eruptions in this young region are possible.

  20. Characteristics and Similarities of Lava Suites from Jorullo and La Pilita Volcanoes, Volcanic Front of the Westernmost Trans-Mexican Volcanic Belt

    Science.gov (United States)

    Roberge, J.; Delgado Granados, H.

    2007-05-01

    The monogenetic volcanic field of Michoacán-Guanajuato is at the westernmost part of the Trans-Mexican Volcanic Belt. This is the region where the influence of the Cocos plate starts under the subduction system beneath North America. Jorullo volcano had eruptive activity between 1759-1774 and La Pilita within the Holocene. The eruption of Jorullo and the products from La Pilita were first treated in the incredible work of Luhr and Carmichael (1985), however nothing else has been done on those lava flows since. We have visited the lava flows from Jorullo and La Pilita volcanoes in January 2007 and many new observations were made. Two flows were emitted from the north cone, the age of these lavas is debatable and apparently are older than Jorullo. Also a big older flow is running from the southern base of the main Jorullo cone. So far, this big flow had been ignored in the literature and we found that it is texturally very similar to the La Pilita flow. In this work we present geochemical and textural analyses of over 20 lava flows samples from Jorullo, and 3 lava samples from La Pilita. These data are then compared with samples from the large flow south of Jorullo to constrain his origin and chronology. The origin of this big flow maybe the proof that Jorullo is in fact a volcanic complex, and it was active before the 1959 eruption. This implies that Jorullo may not be a monogenetic volcano.

  1. Mineralogy as a function of depth in the prehistoric Makaopuhi tholeiitic lava lake, Hawaii

    Science.gov (United States)

    Evans, B.W.; Moore, J.G.

    1968-01-01

    The electron probe X-ray microanalyzer has been used to determine the compositional variability of the groundmass minerals and glass in 10 specimens from a complete 225-foot section of the prehistoric tholeiitic lava lake of Makaopuhi Crater, Hawaii. The order of beginning of crystallization was: (1) chromite, (2) olivine, (3) augite, (4) plagioclase, (5) pigeonite, (6) iron-titanium oxides and orthopyroxene, (7) alkali feldspar and apatite, and (8) glass. Although the lake is chemically tholeiitic throughout, the occurrence of ferromagnesian minerals is as though there were a gradation from alkali olivine basalt in the upper chill downwards to olivine tholeiite. Groundmass olivine decreases downwards and disappears at about 20 feet. Pigeonite is absent in the uppermost 5??2 feet, then increases in amount down to 20 feet, below which augite and pigeonite coexist in constant 2:1 proportions. Strong zoning and metastable compositions characterize the pyroxenes of the chilled zones, but these features gradually disappear towards the interior of the lake to give way to equilibrium pyroxenes. Relatively homogeneous poikilitic orthopyroxene (??? Ca4Mg70Fe26) occurs in the olivine cumulate zone, having formed partly at the expense of pre-existing olivine, augite, and pigeonite (??? Ca8Mg66Fe26). The growth of orthopyroxene is believed to have been facilitated by the slower cooling rate and higher volatile pressure at depth, and by the rise in Mg/Fe ratio of the liquid due to the partial dissolution of settled olivine. Unlike olivine and pyroxene, feldspar is least zoned in the upper and lower chilled regions. The greatest range of compositional zoning in feldspar occurs at 160 to 190 feet, where it extends continuously from Or1.0Ab22An77 to Or64Ab33An3. The feldspar fractionation trend in the An-Ab-Or triangle gradually shifts with depth toward more "equilibrium" trends, even though the zoning becomes more extreme. The variation with depth in the initial (core

  2. Regolith and Environment Science and Oxygen and Lunar Volatile Extraction (RESOLVE): Lunar Advanced Volatile Analysis (LAVA) Capillary Fluid Dynamic Restriction Effects on Gas Chromatography

    Science.gov (United States)

    Gonzalez, Marianne; Quinn, Jacqueline; Captain, Janine; Santiago-Bond, Josephine; Starr, Stanley

    2015-01-01

    The Resource Prospector (RP) mission with the Regolith and Environment Science and Oxygen Lunar Volatile Extraction (RESOLVE) payload aims to show the presence of water in lunar regolith, and establish a proving ground for NASAs mission to Mars. One of the analysis is performed by the Lunar Advanced Volatiles Analysis (LAVA) subsystem, which consists of a fluid network that facilitates the transport of volatile samples to a gas chromatograph and mass spectrometer (GC-MS) instrument. The understanding of fluid dynamics directed from the GC to the MS is important due to the influence of flow rates and pressures that affect the accuracy of and prevent the damage to the overall GC-MS instrument. The micro-scale capillary fluid network within the GC alone has various lengths and inner-diameters; therefore, determination of pressure differentials and flow rates are difficult to model computationally, with additional complexity from the vacuum conditions in space and lack of a lunar atmosphere. A series of tests were performed on an experimental set-up of the system where the inner diameters of the GC transfer line connecting to the MS were varied. The effect on chromatography readings were also studied by applying these lines onto a GC instrument. It was found that a smaller inner diameter transfer line resulted in a lower flow rate, as well as a lower pressure differential across the thermal conductivity detector (TCD) unit of the GC and a negligible pressure drop across the mock-up capillary column. The chromatography was affected with longer retention times and broader peak integrations. It was concluded that a 0.050 mm inner diameter line still proved most suitable for the systems flow rate preferences. In addition, it was evident that this small transfer line portrayed some expense to GC signal characteristics and the wait time for steady-state operation.

  3. Relationships between deformation and mixing processes in lava flows: a case study from Salina (Aeolian Islands, Tyrrhenian Sea)

    Science.gov (United States)

    Rosa, Rosanna De; Mazzuoli, Roberto; Ventura, Guido

    1996-11-01

    The massive unit of a lava flow from Porri volcano (Salina, Aeolian Islands) displays many unusual structures related to the physical interaction between two different magmas. The magma A represents approximately 80% of the exposed lava surface; it has a crystal content of 51 vol.% and a dacitic glass composition (SiO2=63 64 wt.%). The magma B has a basaltic-andesite glass composition (SiO2=54 55 wt.%) and a crystal content of approximately 18 vol.%. It occurs as pillow-like enclaves, banding, boudin-like and rolling structures which are hosted in magma A. Structural analysis suggests that banding and boudin-like structures are the result of the deformation of enclaves at different shear strain. The linear correlation between strain and stratigraphic height of the measured elements indicates a single mode of deformation. We deduce that the component B deformed according to a simple shear model. Glass analyses of the A B boundary indicate that A and B liquids mix together at high shear strain, whereas only mingling occurs at low shear strain. This suggests that the amount of deformation (i.e. forced convection) plays an important role in the formation of hybrid magmas. High shear strain may induce stretching, shearing and rolling of fluids which promote both forced convection and dynamical diffusion processes. These processes allow mixing of magmas with large differences in their physical properties.

  4. Petrography, age, and paleomagnetism of basaltic lava flows in coreholes at Test Area North (TAN), Idaho National Engineering Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Lanphere, M.A.; Champion, D.E. [Geological Survey, Menlo Park, CA (United States). Branch of Isotope Geology; Kuntz, M.A. [Geological Survey, Denver, CO (United States). Branch of Central Regional Geology

    1994-12-31

    The petrography, age, and paleomagnetism were determined on basalt from 21 lava flows comprising about 1,700 feet of core from two coreholes (TAN CH No. 1 and TAN CH No. 2) in the Test Area North (TAN) area of the Idaho National Engineering Laboratory (INEL). Paleomagnetic studies were made on two additional cores from shallow coreholes in the TAN area. K-Ar ages and paleomagnetism also were determined on nearby surface outcrops of Circular Butte. Paleomagnetic measurements were made on 416 samples from four coreholes and on a single site in surface lava flows of Circular Butte. K-Ar ages were measured on 9 basalt samples from TAN CH No. 1 and TAN CH No. 2 and one sample from Circular Butte. K-Ar ages ranged from 1.044 Ma to 2.56 Ma. All of the samples have reversed magnetic polarity and were erupted during the Matuyama Reversed Polarity Epoch. The purpose of investigations was to develop a three-dimensional stratigraphic framework for geologic and hydrologic studies including potential volcanic hazards to facilities at the INEL and movement of radionuclides in the Snake River Plain aquifer.

  5. A long-scale biodiversity monitoring methodology for Spanish national forest inventory. Application to Álava region

    Directory of Open Access Journals (Sweden)

    Iciar Alberdi

    2014-04-01

    Full Text Available Aim of study: In this study, a methodology has been designed to assess biodiversity in the frame of the Spanish National Forest Inventory with the aim of evaluating the conservation status of Spanish forests and their future evolution. This methodology takes into account the different national and international initiatives together with the different types and characteristics of forests in Spain. Area of study: Álava province (Basque country, Spain.Material and methods: To analyse the contribution of each of the different indices to the biodiversity assessment, a statistical analysis using PCA multivariate techniques was performed for structure, composition and dead wood indicators. Main Results: The selected biodiversity indicators (based on field measurements are presented along with an analysis of the results from four representative forest types in Álava by way of an example of the potential of this methodology. Research highlights: The statistical analysis revealed the important information contribution of Mingling index to the composition indicators. Regarding the structure indicators, it is remarkable the interest of using standard deviations and skewness of height and diameter as indicators. Finally it is interesting to point out the interest of assessing dead saplings since they provide additional information and their volume is a particularly useful parameter for analyzing the success of regeneration.Keywords: species richness; structural diversity; dead wood; NFI; PCA.

  6. Geochemical and Mineralogical Analyses of Palagonitic Tuffs and Altered Rinds of Pillow Lavas on Iceland and Applications to Mars

    Science.gov (United States)

    Bishop, Janice; Schiffman, P.; Southard, R.; DeVincenzi, Donald L. (Technical Monitor)

    2000-01-01

    Samples of altered pillow lavas and hyalotuffs were collected from a volcanic Tuya and hyaloclastite ridge in western Iceland. Altered basaltic material from regions such as Hloudufell Tuya and Thorolfsfell Ridge may be similar to the surface fines on Mars, which are thought to contain altered basaltic components as well. Geochemical and mineralogical analyses have been performed on the Icelandic samples in order to characterize the properties that distinguish palagonitization from other forms of low temperature alteration in this environment. Major elements were measured using an electron microprobe and mineralogy was determined through X-ray diffraction and visible- infrared reflectance spectroscopy. The primary focus in this study was on the less than 2 microns size fractions of the Hloudufell altered pillow and Thorolfsfell palagonitic tuff samples. The palagonitic tuff contained more crystalline clay minerals and has a higher Al/Fe ratio. The altered pillow lava contained higher abundances of nanophase iron oxides/oxyhydroxides. The extended visible region spectra of the less than 2 microns fractions of both Icelandic samples are similar to bright Martian soils measured by Pathfinder.

  7. Variations of magnetic properties in thin lava flow profiles: Implications for the recording of the Laschamp Excursion

    Science.gov (United States)

    Vérard, Christian; Leonhardt, Roman; Winklhofer, Michael; Fabian, Karl

    2012-06-01

    Two blocks have been cut in two lava flows from the Skalamaelifell Hill (Iceland) known to have recorded the Laschamp magnetic excursion (40.4 ± 2.0 ka). Detailed sampling and analyses have revealed multiple magnetic components. The high temperature/coercivity component corresponds to the primary magnetisation, with corresponding pole position close to the equator in the Pacific Ocean (φ = 251.90°/λ = -06.49°; dp = 0.74°/dm = 2.12°) and palaeo-intensity determinations below 5 μT. The different VGPs, however, vary in relation with the position of samples in the profiles. It could not be firmly established whether this distribution is associated with a change in the Earth magnetic field during lava cooling. In any case, variations are related with zones in the profiles marked, in particular, by the presence of vesicles. Moreover, the other components are interpreted to be linked with alteration inside the rocks, caused by interactions between vesicles content and the surrounding matrix. Secondary component, however, is interpreted as recording an excursional magnetic field, and should be of greater consideration in studies of Earth magnetic field excursions or reversals.

  8. Metal biogeochemistry in constructed wetlands based on fluviatile sand and zeolite- and clinopyroxene-dominated lava sand.

    Science.gov (United States)

    Huang, Jen-How; Paul, Sonja; Mayer, Silke; Moradpour, Eloise; Hasselbach, Ralf; Gieré, Reto; Alewell, Christine

    2017-06-07

    For the first time, speciation of Fe, Mn, Zn, Ni, Cu and Pb was determined along the profiles of 8 constructed wetlands (CWs) consisting of fluviatile sand (Fluv), clinopyroxene-dominated lava sand (Cl-LS) and zeolite-dominated lava sand (Ze-LS), aiming at quantifying metal behaviour in CWs and the impact caused by different filter materials. With the exception of Mn, which underwent reductive dissolution, CWs were sinks for the studied metals. Metal accumulation rates differed in the following order: Ze-LS ≥ Cl-LS > Fluv CWs, reflecting the highest metal adsorption capacity and the lowest hydraulic conductivity of Ze-LS. Sequential extraction data indicated the highest metal mobility (readily mobilised and adsorbed fractions summing up to ~60%) in Fluv CWs, implying a higher risk of metal release into adjacent environments if Fluv from CWs will be improperly disposed after usage. Zinc and Ni were transported into the deeper CW layers to a larger extent than Cu and Pb, reflecting adsorption affinity to all filter materials in the order of Pb > Cu > Zn > Ni. Therefore, understanding metal speciation and mobility in such materials is crucial when they are considered for application as filters in CWs.

  9. Individual magma batches related to the origin of Yellowstone 516-70 ka post-caldera rhyolitic lava flows : results from glass geochemistry.

    Science.gov (United States)

    Stix, J.; Girard, G.

    2007-12-01

    Since its last collapse at 640 ka, Yellowstone caldera has been filled by at least 25 voluminous rhyolitic lava flows totalling more than 900 km3. The oldest identified flows have been erupted at 516 ka, 486-479 ka and 198 ka around the two resurgent domes. Most of the known effusions occurred during relatively short episodes from 165 to 147 ka, 117 to 102 ka, and 72 to 70 ka (Christiansen, 2001), erupting along 2 NNW-trending lineaments which are parallel to regional faults and do not intersect the resurgent domes. The intermittent nature of the volcanism and its spatial distribution remain largely unresolved questions. We used a combination of XRF whole rock major and trace element analyses, electron microprobe and laser ablation-ICP-MS major and trace element glass micro-analyses to examine the temporal and spatial links among the eruptions. Petrologically, we observe a broad-scale differentiation of the lavas over time. Lavas dated at 516 ka have SiO2 contents of 71-72 wt% for bulk rock and 76-76.5 wt% in glass, while 165 ka and younger lavas exhibit SiO2 contents of 76.5-77.5 wt% for both the bulk rock and glass. Mineralogically, the lavas evolve from plagioclase-dominated to sanidine and quartz with no plagioclase. These observations suggest an origin from a common source undergoing slow differentiation. Temporal changes of certain trace elements such as Sr and Ba also suggest a similar evolution. For instance, Sr evolves from 115 ppm in bulk rock in the most primitive lavas of the 516 ka group, to 60 ppm at 198 ka, declining to 2.5 ppm at 70 ka. A simultaneous increasingly negative Eu anomaly is observed in the glass. Such behavior is expected from feldspar fractionation in a long-lived reservoir. Elements such as Y, Th and REE also behave compatibly in the Yellowstone lavas, their concentrations being systematically higher in bulk rock compared to glass. Should the system be a long-lived magma chamber undergoing fractionation, their concentrations over time

  10. Analysis of multi-resolution satellite imagery of the 2012-2013 eruption of Tolbachik volcano, Kamchatka, with comparison of lava flow modeling and ground observations

    Science.gov (United States)

    Morgan, H. A.; Dehn, J.; Webley, P.

    2013-12-01

    The ongoing eruption of Tolbachik volcano (Kamchatka, Russia) began on November 27, 2012 and lava continues to effuse as of July 31, 2013. The voluminous lava flow field has spread to an area of over 30 km^2 and has traveled approximately 15 km from the main vent. Such a large, sustained effusive eruption provides a unique target for comparison of infrared- and visible-wavelength satellite imagery of various spatial, temporal, and spectral resolutions. We use imagery from five satellite sensors with infrared and visible imaging capabilities (i.e., ALI, Landsat 8, ASTER, MODIS, and AVHRR) to measure the areal extent of the lava throughout the eruption, identify morphological features, and calculate rough lava effusion rates based on new area accumulated between images. Additionally, we model lava effusion rates assuming a linear correlation with flow area, and compare our results to ground-based observations. Using the datasets with spatial resolutions ranging from 10 to 1090 m, we investigate how the choice of which and how many pixels to include in the model (i.e., all thermally anomalous pixels, only the single hottest pixel, or every pixel above a threshold temperature) affects the accuracy of the resulting effusion rates. We thus identify the method that produces the best effusion rates for a given sensor and/or spatial resolution. Figure 1: Outline of the lava flow field determined from thermal infrared and visible bands of three separate sensors over a 24-hour period. MODIS provides multiple images per day and is useful for detecting rapid changes in activity, while ALI and ASTER provide much higher-resolution imagery that reveals more detail but is only available about once per week.

  11. The 1998-2001 submarine lava balloon eruption at the Serreta ridge (Azores archipelago): Constraints from volcanic facies architecture, isotope geochemistry and magnetic data

    Science.gov (United States)

    Madureira, Pedro; Rosa, Carlos; Marques, Ana Filipa; Silva, Pedro; Moreira, Manuel; Hamelin, Cédric; Relvas, Jorge; Lourenço, Nuno; Conceição, Patrícia; Pinto de Abreu, Manuel; Barriga, Fernando J. A. S.

    2017-01-01

    The most recent submarine eruption observed offshore the Azores archipelago occurred between 1998 and 2001 along the submarine Serreta ridge (SSR), 4-5 nautical miles WNW of Terceira Island. This submarine eruption delivered abundant basaltic lava balloons floating at the sea surface and significantly changed the bathymetry around the eruption area. Our work combines bathymetry, volcanic facies cartography, petrography, rock magnetism and geochemistry in order to (1) track the possible vent source at seabed, (2) better constrain the Azores magma source(s) sampled through the Serreta submarine volcanic event, and (3) interpret the data within the small-scale mantle source heterogeneity framework that has been demonstrated for the Azores archipelago. Lava balloons sampled at sea surface display a radiogenic signature, which is also correlated with relatively primitive (low) 4He/3He isotopic ratios. Conversely, SSR lavas are characterized by significantly lower radiogenic 87Sr/86Sr, 206Pb/204Pb and 208Pb/204Pb ratios than the lava balloons and the onshore lavas from the Terceira Island. SSR lavas are primitive, but incompatible trace-enriched. Apparent decoupling between the enriched incompatible trace element abundances and depleted radiogenic isotope ratios is best explained by binary mixing of a depleted MORB source and a HIMU­type component into magma batches that evolved by similar shallower processes in their travel to the surface. The collected data suggest that the freshest samples collected in the SSR may correspond to volcanic products of an unnoticed and more recent eruption than the 1998-2001 episode.

  12. A geochronological study of mafic and acidic lavas from Veneto Volcanic province (North-East Italy)

    Science.gov (United States)

    Brombin, Valentina; Webb, Laura; Bonadiman, Costanza; Marzoli, Andrea; Coltorti, Massimo

    2017-04-01

    The Veneto Volcanic Province (VVP), in the North-East of Italy represents one of the most important magmatic province of the Adria Plate. VVP magmatism occurred in a period ranging from late Paleocene to late Oligocene (De Vecchi et al., 1976). Five main volcanic districts can be defined from north-west to south-east: Val d'Adige, Marosticano, Lessini Hills, Berici Hills and Euganean Hills. Most of the volcanic products are relatively undifferentiated lavas, ranging in compostion from mela-nephelinites to quartz-normative tholeiites (Beccaluva et al., 2007). By contrast in the Euganean Hills volcanic and subvolcanic rocks range from subordinate basalts to prevalently acidic types, mostly quartz-trachytes and rhyolites (Milani et al., 1999). Despite of the deep petrological knowledge about this province, the radioisotopic ages of the related volcanic activities for each district are still poorly defined or even totally missing. 40Ar/39Ar ages on 9 samples have been obtained to determine the age range for the VVP. 40Ar/39Ar whole rock step heating analyses yielded ages ranging from 40.7 ± 0.2 Ma to 23.3 ± 1.5 Ma for basanites of Val d'Adige and Marosticano area, respectively. For the Lessinean district, 40Ar/39Ar whole rock analyses for two basanites, one trachybasalt and one alkali basalt close to 40 Ma, while a tholeiite from the same area yielded the youngest age for this district (i.e. 32.9 ± 1.8 Ma). This young age is comparable to 40Ar/39Ar ages obtained for the Euganean Hills intermediate-acidic rocks (Jourdan, pers. comm., 2016), suggesting a time-related shift from more alkaline to Si-saturated magmatism in the whole province. References Barbieri G., Medizza F. (1969). Contributo alla conoscenza geologica della regione di Bolca (Monti Lessini). Memorie dell'Istituto di Geologia e Mineralogia dell'Università di Padova, 27, 1-36. Beccaluva L., Bianchini G., Bonadiman C., Coltorti M., Milani L., Salvini L., Siena F., Tassinari R. (2007). Intraplate

  13. Geochemical models of melting and magma storage conditions for basalt lava from Santorini Volcano, Greece

    Science.gov (United States)

    Baziotis, Ioannis; Kimura, Jun-Ichi; Pantazidis, Avgoustinos; Klemme, Stephan; Berndt, Jasper; Asimow, Paul

    2017-04-01

    Santorini volcano sits ˜150 km above the Wadati-Benioff zone of the Aegean arc, where the African plate subducts northward beneath the Eurasian continent (Papazachos et al. 2000). Santorini volcano has a long history: activity started ca. 650 ka (mainly rhyolites and rhyodacites), with active pulses following ca. 550 ka (basalt to rhyodacite) and ca. 360 ka (large explosive eruptions of andesite to rhyodacite and minor basalt), culminating in the caldera-forming Bronze-age Minoan event (Druitt et al. 1999). As in many arc volcanoes, scenarios of fractional crystallization with or without mixing between felsic and mafic magmas have been proposed to explain the compositions, textures, and eruptive styles of Santorini products (e.g., Huijsmans & Barton 1989; Montazavi & Sparks 2004; Andújar et al. 2015). Here we focus on a basalt lava from the southern part of Santorini volcano (Balos cove, 36˚ 21.7'N, 25˚ 23.8'E), one of the few basaltic localities in the Aegean arc. The goals are to infer constraints on the magma chamber conditions which lead to mafic eruption at Santorini Volcano and to evaluate the slab and mantle wedge conditions via geochemical and petrological mass balance modelling. We collected and characterised 20 samples for texture (SEM), mineral chemistry (FE-EPMA) and whole-rock chemistry (XRF). The basalts contain phenocrystic olivine (Ol) and clinopyroxene (Cpx) (magnetite (Mt) with minor glass and rare xenocrystic quartz. Santorini basalts exhibit a pilotaxitic to trachytic texture defined by randomly to flow-oriented tabular Pl, respectively. The predominant minerals are calcic Pl (core An78-85 and rim An60-76; 45-50 vol.%), Cpx (En36-48Wo41-44Fs11-21; 10-15 vol.%) and Ol (Fo74-88; 10-12 vol.%). Idiomorphic to subidiomorphic Mt (<10μm diameter) with variable TiO2 contents (1.9-16.5 wt%) is a minor constituent (˜1-2 vol.%) in the less mafic samples. Observed mineralogy and major element chemistry suggest fractionation in a shallow magma chamber

  14. Analog experimental models of solidification of crystal-laden Kīlauea Iki lava lake, Hawai`i and implications for cumulate development.

    Science.gov (United States)

    Burnett, C. T.; Patwardhan, K.

    2016-12-01

    We present results from experimental models of Kīlauea Iki lava lake with the goal of reproducing the S-shaped vertical distribution profile of phenocrysts in the solidifying lava lake. In November-December 1959, lava from a two-week long eruption at the summit of Kīlauea Volcano flowed into the adjoining Kīlauea Iki crater filling it with a lake of lava approximately 640 m across and 135 m deep. The erupted picritic lava contained approximately 17 modal % olivine phenocrysts (Garcia, 2003). As the lava lake filled most of the phenocrysts sank towards the lower parts of the lake while some were captured in the upper crust. This resulted in an S-shaped vertical profile with an olivine-depleted (1-3 % olivine) upper part and an olivine-enriched (up to 40 % olivine) lower part (Helz, 1989). In our experiments, molten paraffin wax, extra-fine craft glitter, and aluminum foil pans/bowls are used as analogs for magma, olivine phenocrysts, and Kīlauea Iki pit crater respectively. A molten paraffin-glitter mixture at approximately 54°C is stirred/poured into the crater to create the lake, and then frozen. Cross-sections of the solidified lake are photographed and imported into ImageJ to analyze the final distribution of glitter particles at various depths. This distribution depends primarily upon the competition between settling rate vs. solidification time. Particle settling rate is controlled by glitter-paraffin density difference and paraffin viscosity. Solidification time varies with initial paraffin temperature, aspect ratio of the model lake, and ambient temperature. Vertical profiles of several solidified lava lake models reveal a glitter particle (phenocryst) distribution similar to the S-shaped characteristic profile recorded at Kīlauea Iki. In effect, our lava lake models recreate the dynamic process of emplacement of crystal-laden magma with subsequent settling of these crystals to produce a phenocryst-enriched layer near the bottom. A similar process

  15. New Insights to the Mid Miocene Calc-alkaline Lavas of the Strawberry Volcanics, NE Oregon Surrounded by the Coeval Tholeiitic Columbia River Basalt Province

    Science.gov (United States)

    Steiner, A. R.; Streck, M. J.

    2013-12-01

    The Strawberry Volcanics (SV) of NE Oregon were distributed over 3,400 km2 during the mid-Miocene and comprise a diverse volcanic suite, which span the range of compositions from basalt to rhyolite. The predominant composition of this volcanic suite is calc-alkaline (CA) basaltic andesite and andesite, although tholeiitic (TH) lavas of basalt to andesite occur as well. The coeval flood basalts of the Columbia River province surround the SV. Here we will discuss new ages and geochemical data, and present a new geologic map and stratigraphy of the SV. The SV are emplaced on top of pre-Tertiary accreted terranes of the Blue Mountain Province, Mesozoic plutonic rocks, and older Tertiary volcanic rocks thought to be mostly Oligocene of age. Massive rhyolites (~300 m thick) are exposed mainly along the western flank and underlie the intermediate composition lavas. In the southern portion of this study area, alkali basaltic lavas, thought to be late Miocene to early Pliocene in age, erupted and overlie the SV. In addition, several regional ignimbrites reach into the area. The 9.7 Ma Devine Canyon Tuff and the 7.1 Ma Rattlesnake Tuff also overlie the SV. The 15.9-15.4 Ma Dinner Creek Tuff is mid-Miocene, and clear stratigraphic relationships are found in areas where the tuff is intercalated between thick SV lava flows. All of the basalts of the SV are TH and are dominated by phenocryst-poor (≤2%) lithologies. These basalts have an ophitic texture dominated by plagioclase, clinopyroxene and olivine (often weathered to iddingsite). Basalts and basaltic andesites have olivine Fo #'s ranging from 44 at the rims (where weathered to iddingsite) and as high as 88 at cores. Pyroxene Mg #'s range from 65 to 85. Andesites of the SV are sub-alkaline, and like the basalts, are exceedingly phenocryst-poor (≤3%) with microphenocrysts of plagioclase and lesser pyroxene and olivine, which occasionally occur as crystal clots of ~1-3 mm instead of single crystals. In addition, minimal

  16. A new intense lava fountain episode at Voragine crater (Mt. Etna): the event of 3 December 2015

    Science.gov (United States)

    Andronico, Daniele; Bonadonna, Costanza; Cioni, Raffaello; Cristaldi, Antonio; Pascual, Aurélie Joy; Russo, Alessandro; Scollo, Simona

    2016-04-01

    On 3 December 2015 Voragine crater, one of the five summit craters of Mt. Etna (Italy), produced a powerful lava fountain. The last paroxysmal episodes from this crater had occurred on July 1998 and September 1999; both events had been very intense, the first one classified as subPlinian and the latter causing significant disruption to road traffic due dense tephra sedimentation. Afterward, the Voragine entered in a period of relative quiescence interrupted by short events of Strombolian activity and weak ash emissions. In August 2015 the crater resumed its activity with discontinuous ash puffs that were followed by periods of relatively intense ash blasts in September. In October, this activity was clearly replaced by weak, pulsating Strombolian explosions confined inside the crater, which was several tens of meter deep. Gradually the Strombolian blasts became more continuous and intense and lapilli started to sediment around the crater rim. In the night between 2 and 3 December, the increase of seismic tremor coevally to the Strombolian activity heralded the lava fountain episode. During the paroxysm, that lasted around 40 minutes, vigorous magma jets were also produced by the adjacent Bocca Nuova summit crater, contributing to form a unique eruption column up to at least 7-8 km above the volcano and dispersed to the NE. Lighting was recurrently observed inside the column. Field survey, carried out between 3 and 5 December from a distance of 5 km from the vent, allowed to map the fallout dispersal and collect tephra samples. Estimation of uncertainty associated with ash sampling were also performed. Due to low-intense winds, the fallout mostly affected the area close to the volcanic slopes, but it also reached both the Tyrrhenian Sea to the N and the Ionian Sea to the E, more than 100 km of distance from the crater. Measurements of shape and density on the largest clasts collected within the first km from the Voragine were performed. Furthermore, we measured the

  17. Contributing to a precise and accurate chronostratigraphic time scale for climatic records: Absolute dating and paleomagnetism in lavas

    Science.gov (United States)

    Sasco, Romain; Guillou, Herve; Kissel, Catherine; Wandres, Camille; Carracedo, Juan-Carlos; Perez Torrado, Francisco Jose

    2014-05-01

    Understanding climatic mechanisms requires a robust and precise timescale allowing long-distance and multi-archives correlations. A unique tool to construct such time scales is provided by the Earth magnetic field (EMF), which is independent from climatic variations and the past evolution of which is recorded in most of the geological/climatic archives. Sedimentary sequences provide continuous records of relative intensities of the EMF on stratigraphic time scales, usually based on orbital tuning. They are transferred onto absolute intensity scale and chronological time scale using robust tie points available for the past ~40 ka. However, for older periods this calibration remains poorly constrained. Our study reports on new tie points over the last 200 ka by combining paleomagnetic and geochronological (K/Ar and 40Ar-39Ar dating) studies on lavas. Based on the K-Ar LSCE age database, a set of 18 lava flows corresponding to potential geomagnetic excursions and/or highs and lows in the paleomagnetic intensity as observed from sediments and occurring in the studied time-window were selected in the Canary Islands (Tenerife, La Palma and Gran Canaria). A total of 205 oriented cores were taken from these 18 lava flows. Rock magnetic experiments include thermomagnetic analyses on each core, hysteresis loop and First Order Reversal Curves. Stepwise thermal demagnetizations in zero-field provided reliable mean-site paleomagnetic direction of the EMF for 15 of the flows. Paleointensity values were determined using the original Thellier and Thellier method. Based on previous experiments, 170 samples were analyzed, among which 51% provided reliable paleointensity values (determined using PICRIT-03 criteria). The geochronological study focused on 40Ar-39Ar dating. Based on preliminary paleomagnetic results, 13 flows were analyzed and 11 provided ages consistent at the 2 sigma level with the already available K-Ar ages. This coupled K/Ar - 40Ar-39Ar results strongly constrain

  18. Prehistoric Agriculture and Soil Fertility on Lava Flows in Northern Arizona, USA: Results from the San Francisco Volcanic Field REU

    Science.gov (United States)

    Broadman, E.; Anderson, K. C.

    2013-12-01

    The San Francisco Volcanic Field in northern Arizona is home to ~600 cinder cones, the youngest of which is Sunset Crater (erupted ~AD 1100). This study documents trends in available phosphate and nitrate content with time, testing whether lowered soil pH from the addition of Sunset cinders increased soil fertility and became a factor in Anasazi agricultural success. Soil fertility is examined both before and after Sunset's eruption in soils of different ages that have developed from eolian deposition on top of lava flows. An increase in phosphate and nitrate levels following acidification would suggest that the presence of Sunset cinders brought the soils to the optimal pH for mobilization of these nutrients. The combined effects of the cinder layer retaining nutrients and water, wetter climates, and increases in phosphate and nitrate (both limiting nutrients for plant growth), would have contributed to Anasazi agricultural success after Sunset's eruption. Samples for this study were taken from eolian-derived soils of different ages atop lava flows in the San Francisco Volcanic Field. OSL data from these soils on Strawberry and SP Craters' lava flows yielded age estimates of ~12.3 ka (Strawberry) and ~32.7 ka (SP), on which a soil chronosequence was based. Results from the chronosequence supported these OSL ages, indicating that soils on the SP flow are older than those on the Strawberry flow. Field descriptions, Harden Development Indices, particle size analysis, and nutrient content analysis were used for this aspect of the project. An experimental acid wash method will be used to simulate the addition of Sunset's acidic cinders, and will yield data for phosphate and nitrate content after Sunset erupted. Preliminary results indicate that phosphate and nitrate accumulate in upper, eolian-derived horizons (Av, Bw) and in more deeply buried carbonate horizons (Bk). Higher concentrations of phosphate and nitrate were found in older (SP) soils than younger

  19. Cosmic ray exposure dating with in situ produced cosmogenic 3He: results from young Hawaiian lava flows

    Science.gov (United States)

    Kurz, M.D.; Colodner, D.; Trull, T.W.; Moore, R.B.; O'Brien, K.

    1990-01-01

    In an effort to determine the in situ production rate of spallation-produced cosmogenic 3He, and evaluate its use as a surface exposure chronometer, we have measured cosmogenic helium contents in a suite of Hawaiian radiocarbon-dated lava flows. The lava flows, ranging in age from 600 to 13,000 years, were collected from Hualalai and Mauna Loa volcanoes on the island of Hawaii. Because cosmic ray surface-exposure dating requires the complete absence of erosion or soil cover, these lava flows were selected specifically for this purpose. The 3He production rate, measured within olivine phenocrysts, was found to vary significantly, ranging from 47 to 150 atoms g-1 yr-1 (normalized to sea level). Although there is considerable scatter in the data, the samples younger than 10,000 years are well-preserved and exposed, and the production rate variations are therefore not related to erosion or soil cover. Data averaged over the past 2000 years indicate a sea-level 3He production rate of 125 ?? 30 atoms g-1 yr-1, which agrees well with previous estimates. The longer record suggests a minimum in sea level normalized 3He production rate between 2000 and 7000 years (55 ?? 15 atoms g-1 yr-1), as compared to samples younger than 2000 years (125 ?? 30 atoms g-1 yr-1), and those between 7000 and 10,000 years (127 ?? 19 atoms g-1 yr-1). The minimum in production rate is similar in age to that which would be produced by variations in geomagnetic field strength, as indicated by archeomagnetic data. However, the production rate variations (a factor of 2.3 ?? 0.8) are poorly determined due to the large uncertainties in the youngest samples and questions of surface preservation for the older samples. Calculations using the atmospheric production model of O'Brien (1979) [35], and the method of Lal and Peters (1967) [11], predict smaller production rate variations for similar variation in dipole moment (a factor of 1.15-1.65). Because the production rate variations, archeomagnetic data

  20. An experimental insight into the evolution of permeability at high temperatures and applications for shallow conduit and lava dome degassing

    Science.gov (United States)

    Chadderton, Amy; Sammonds, Peter; Meredith, Philip; Smith, Rosanna; Tuffen, Hugh; Gaunt, Elizabeth

    2016-04-01

    Two recent eruptions in Chile, at Chaitén Volcano in 2008-10 and Cordón Caulle in 2011-12, allowed the first detailed observations of rhyolitic activity and provided insights into the evolution of highly silicic eruptions. Both events exhibited simultaneous explosive and effusive activity, with both lava and ash plumes emitted from the same vent [1]. The permeability of fracture networks that act as fluid flow pathways is key to understanding such eruptive behaviour. Here, we report results from a systematic experimental investigation of permeability in volcanic rocks at magmatic temperatures and pressures, in the presence of pore fluids using our newly-developed high-temperature permeability facility. Enhancements to the High Temperature Triaxial Deformation Cell at UCL [2] have enabled us to make permeability measurements on 25mm x 50mm cores at both elevated temperature and elevated hydrostatic pressure [3]. We present results from several suites of permeability measurements on samples of dome dacite from the 2004-08 eruption of Mount St Helens, and rhyolite collected from the lava dome formed during the 2008-10 eruption of Chaitén, Chile. Tests were conducted at temperatures up to 900oC and under an effective pressure of 5 MPa, using the steady-state flow technique. Samples were cooled to room temperature between each high temperature test, and the permeability of each sample was re-measured before heating to the next temperature increment in the series. Additional longer duration high temperature tests were also conducted to investigate the development of a permeable network at high temperatures over time. The results show a complex permeability evolution that includes a reduction in permeability by approximately 3 orders of magnitude up to 600oC. Together with thermal cracking tests, AE data and SEM/thin section analysis these new experimental permeability results are applied to enhance our understanding of the complex issue of shallow conduit and lava

  1. Cyclic pressurisation of Mount St Helens dacites and basalt. Laboratory results and implications for lava dome monitoring

    Science.gov (United States)

    Kendrick, Jackie; Dainty, Matthew; Smith, Rosanna; Sammonds, Peter; Pallister, John; Meredith, Phillip

    2010-05-01

    Lava domes are frequently subjected to cyclic heating and pressurisation, which may weaken the dome rocks, leading to renewed extrusion, explosions or collapse. These heating and loading cycles can be recreated in the laboratory, allowing the level of crack damage caused by these cycles to be established through analysing elastic moduli. Acoustic emissions (AEs) indicate the timing of cracking, and can also be used to interpret precursory seismicity for eruption prediction. Experiment samples are from Mount St. Helens, USA: 3 dacites from the Pine Creek eruptive period (2.9-2.55 ka), a Castle Creek age basalt (2.55-1.895 ka), and 4 dacites from the 2004-2008 eruption. Each sample was cut into several cylindrical cores (25 mm diameter and 62.5-70 mm long). Some samples were then heated and cooled at 1˚C/ minute to a target temperature of 600o C or 900o C, and held for 2 hours to achieve thermal equilibrium. This heating can cause cracking due to contrasts in thermal expansion of different minerals. Dynamic elastic moduli were calculated for each sample using ultrasonic wave velocity, density and porosity for later comparison to static elastic moduli gathered during deformation. One core of each sample was loaded to failure in uniaxial compression in order to find the short term strength of the sample. For all cyclic loading tests, conducted on pre-heated and unheated cores, samples were loaded at 10-5 s-1 strain rate then unloaded to 5MPa. Subsequent cycles had an increasing peak load. Most had the same rate for unloading, with a few samples unloaded instantaneously. Axial, radial and volumetric strain were determined from the recorded displacement throughout the experiment and used with the axial stress measurements to calculate static elastic moduli. Samples loaded to failure with no cycling generally failed at higher stresses than their cyclically loaded counter-parts, whilst rapid unloading increased their strength. Failure stresses of the dacite lava dome

  2. Genesis of ultra-high-Ni olivine in high-Mg andesite lava triggered by seamount subduction.

    Science.gov (United States)

    Nishizawa, Tatsuji; Nakamura, Hitomi; Churikova, Tatiana; Gordeychik, Boris; Ishizuka, Osamu; Haraguchi, Satoru; Miyazaki, Takashi; Vaglarov, Bogdan Stefanov; Chang, Qing; Hamada, Morihisa; Kimura, Jun-Ichi; Ueki, Kenta; Toyama, Chiaki; Nakao, Atsushi; Iwamori, Hikaru

    2017-09-14

    The Kamchatka Peninsula is a prominent and wide volcanic arc located near the northern edge of the Pacific Plate. It has highly active volcanic chains and groups, and characteristic lavas that include adakitic rocks. In the north of the peninsula adjacent to the triple junction, some additional processes such as hot asthenospheric injection around the slab edge and seamount subduction operate, which might enhance local magmatism. In the forearc area of the northeastern part of the peninsula, monogenetic volcanic cones dated at subducted seamount triggered the ascent of Si-rich fluids to vein the wedge peridotite and formed a peridotite-pyroxenite source, causing the temporal evolution of local magmatism with wide compositional range.

  3. Magma-ice-sediment interactions and the origin of lava/hyaloclastite sequences in the Síða formation, South Iceland

    Science.gov (United States)

    Banik, Tenley J.; Wallace, Paul J.; Höskuldsson, Ármann; Miller, Calvin F.; Bacon, Charles R.; Furbish, David J.

    2013-01-01

    Products of subglacial volcanism can illuminate reconstructions of paleo-environmental conditions on both local and regional scales. Competing interpretations of Pleistocene conditions in south Iceland have been proposed based on an extensive sequence of repeating lava-and-hyaloclastite deposits in the Síða district. We propose here a new eruptive model and refine the glacial environment during eruption based on field research and analytical data for the Síða district lava/hyaloclastite units. Field observations from this and previous studies reveal a repeating sequence of cogenetic lava and hyaloclastite deposits extending many kilometers from their presumed eruptive source. Glasses from lava selvages and unaltered hyaloclastites have very low H2O, S, and CO2 concentrations, indicating significant degassing at or close to atmospheric pressure prior to quenching. We also present a scenario that demonstrates virtual co-emplacement of the two eruptive products. Our data and model results suggest repeated eruptions under thin ice or partially subaerial conditions, rather than eruption under a thick ice sheet or subglacial conditions as previously proposed.

  4. Rakvere suveteatri "Noor Eesti" lava = Stage design for the Rakvere summer theatre production "Noor Eesti" / Ott Kadarik, Mihkel Tüür ; intervjueerinud Margit Mutso

    Index Scriptorium Estoniae

    Kadarik, Ott, 1976-

    2012-01-01

    Lava autorid: Ott Kadarik, Mihkel Tüür (Kadarik Tüür Arhitektid), kaasautor: Uku-Kristjan Küttis. Näidendi lavastaja: Jaanus Rohumaa. Tallinna fotokuu puhul Vabaduse väljakul olnud installatsioonist "Camera obscura", autorid Ott Kadarik ja Mihkel Tüür

  5. A rock- and palaeomagnetic study of recent lavas and 1995 volcanic glass on Fogo (Cape Verde Islands)

    DEFF Research Database (Denmark)

    Knudsen, M.F.; Abrahamsen, N.; Riisager, P.

    2005-01-01

    Fogo is the only island in the Cape Verde archipelago with accounts of historical volcanic activity.Here we present palaeomagnetic data from seven geologically recent lava flows on Fogo, including one glassy, volcanic flow from the eruption in 1995. Almost all samples behaved well during...

  6. Flowing Hot or Cold: User-Friendly Computational Models of Terrestrial and Planetary Lava Channels and Lakes

    Science.gov (United States)

    Sakimoto, S. E. H.

    2016-12-01

    Planetary volcanism has redefined what is considered volcanism. "Magma" now may be considered to be anything from the molten rock familiar at terrestrial volcanoes to cryovolcanic ammonia-water mixes erupted on an outer solar system moon. However, even with unfamiliar compositions and source mechanisms, we find familiar landforms such as volcanic channels, lakes, flows, and domes and thus a multitude of possibilities for modeling. As on Earth, these landforms lend themselves to analysis for estimating storage, eruption and/or flow rates. This has potential pitfalls, as extension of the simplified analytic models we often use for terrestrial features into unfamiliar parameter space might yield misleading results. Our most commonly used tools for estimating flow and cooling have tended to lag significantly behind state-of-the-art; the easiest methods to use are neither realistic or accurate, but the more realistic and accurate computational methods are not simple to use. Since the latter computational tools tend to be both expensive and require a significant learning curve, there is a need for a user-friendly approach that still takes advantage of their accuracy. One method is use of the computational package for generation of a server-based tool that allows less computationally inclined users to get accurate results over their range of input parameters for a given problem geometry. A second method is to use the computational package for the generation of a polynomial empirical solution for each class of flow geometry that can be fairly easily solved by anyone with a spreadsheet. In this study, we demonstrate both approaches for several channel flow and lava lake geometries with terrestrial and extraterrestrial examples and compare their results. Specifically, we model cooling rectangular channel flow with a yield strength material, with applications to Mauna Loa, Kilauea, Venus, and Mars. This approach also shows promise with model applications to lava lakes, magma

  7. Volcano-tectonic control of Merapi's lava dome splitting observed from high resolution TerraSAR-X data

    KAUST Repository

    Luehr, Birger-G.

    2015-04-01

    Volcanism at active andesite-dacite volcanoes is often associated with the formation and collapse of circular shaped protrusions of extruded, highly viscous lava, the so-called domes, which are emplaced in the near summit region. Growing domes may experience stable and instable structural phases, with a gradual transition in between. Dome collapse and the break-off of instable blocks of viscous lava may lead to pyroclastic flows, one of the most lethal hazards at stratovolcanoes. At Merapi volcano, Indonesia, nearly 50 % of all eruptions are accompanied by these phenomena. After the climactic eruption in 2010 which left an amphitheater in the summit region, a new dome started growing. Three years later, the dome reached a height of approximately 100 m and diameters of 220 and 190 m with a plateau-like surface area of 40,000m2 approximately. On 18/11/2013, an explosion occurred without identified precursors, leaving a major fracture cutting the complete dome structure. Based on high resolution TerraSAR-X satellite radar imagery, we could identify this linear fracture, traceable over ~200m in the long axis, and up to 40m width. After geocoding of the radar amplitude imagery, the fractures azimuthal trend could be compared to other structural lineaments, indicative of a significant NNW-SSE structural direction that has formed on Merapi volcano in the past. This alignment is also visible in a seismic velocity tomographic imagery for the upper crust, down to 15 km depth. The Merapi dome fractured in a NW-SE direction, and is consistent with the alignment of regional tectonic structures and of anticipated directions of pyroclastic flows. The fracture may be part of a larger volcano-tectonic system and may affect the dynamics and the stability of the Merapi dome.

  8. Hot pressing in conduit faults during lava dome extrusion: Insights from Mount St. Helens 2004-2008

    Science.gov (United States)

    Ryan, Amy G.; Friedlander, Elizabeth A.; Russell, James K.; Heap, Michael J.; Kennedy, Lori A.

    2018-01-01

    Rhyodacitic volcanoes such as Mount St. Helens (MSH), Soufrière Hills, Mount Unzen and Mount Pelée erupt spines mantled by layers of magma-derived cataclasite and fault gouge. MSH produced seven lava spines from 2004-2008 composed of low-porosity, compositionally uniform, crystalline dacite. Dome extrusion was attended by continuous 'drumbeat' seismicity, derived from faulting along the conduit margin at 0.5-1 km depth, and evidenced by the enveloping gouge layers. We describe the properties of the gouge-derived fault rocks, including laboratory measurements of porosity and permeability. The gouge varies from unconsolidated powder to lithified low-porosity low-permeability fault rocks. We reconstruct the subsurface ascent of the MSH magma using published field observations and create a model that reconciles the diverse properties of the gouge with conditions in the conduit during ascent (i.e. velocity, temperature). We show lithification of the gouge to be driven by 'hot pressing' processes, wherein the combination of elevated temperature, confining pressure and dwell-time cause densification and solid-state sintering of the comminuted, crystal-rich (glass-poor) gouge. The degree of gouge lithification corresponds with residence time in the conduit such that well-lithified materials reflect extended times in the subsurface due to slower ascent rates. With this insight, we suggest that gouge competence can be used as a first-order estimate of lava ascent rates. Furthermore we posit gouge lithification, which reduces porosity and permeability, inhibits volcanic outgassing thereby increasing the potential for explosive events at spine-producing volcanoes.

  9. Lava Lake Thermal Pattern Classification Using Self-Organizing Maps and Relationships to Eruption Processes at Kīlauea Volcano, Hawaii

    Science.gov (United States)

    Burzynski, A. M.; Anderson, S. W.; Morrison, K.; LeWinter, A. L.; Patrick, M. R.; Orr, T. R.; Finnegan, D. C.

    2014-12-01

    Nested within the Halema'uma'u Crater on the summit of Kīlauea Volcano, the active lava lake of Overlook Crater poses hazards to local residents and Hawaii Volcanoes National Park visitors. Since its formation in March 2008, the lava lake has enlarged to +28,500 m2 and has been closely monitored by researchers at the USGS Hawaiian Volcano Observatory (HVO). Time-lapse images, collected via visible and thermal infrared cameras, reveal thin crustal plates, separated by incandescent cracks, moving across the lake surface as lava circulates beneath. We hypothesize that changes in size, shape, velocity, and patterns of these crustal plates are related to other eruption processes at the volcano. Here we present a methodology to identify characteristic lava lake surface patterns from thermal infrared video footage using a self-organizing maps (SOM) algorithm. The SOM is an artificial neural network that performs unsupervised clustering and enables us to visualize the relationships between groups of input patterns on a 2-dimensional grid. In a preliminary trial, we input ~4 hours of thermal infrared time-lapse imagery collected on December 16-17, 2013 during a transient deflation-inflation deformation event at a rate of one frame every 10 seconds. During that same time period, we also acquired a series of one-second terrestrial laser scans (TLS) every 30 seconds to provide detailed topography of the lava lake surface. We identified clusters of characteristic thermal patterns using a self-organizing maps algorithm within the Matlab SOM Toolbox. Initial results from two SOMs, one large map (81 nodes) and one small map (9 nodes), indicate 4-6 distinct groups of thermal patterns. We compare these surface patterns with lava lake surface slope and crustal plate velocities derived from concurrent TLS surveys and with time series of other eruption variables, including outgassing rates and inflation-deflation events. This methodology may be applied to the continuous stream of

  10. Pahoehoe-a‧a transitions in the lava flow fields of the western Deccan Traps, India-implications for emplacement dynamics, flood basalt architecture and volcanic stratigraphy

    Science.gov (United States)

    Duraiswami, Raymond A.; Gadpallu, Purva; Shaikh, Tahira N.; Cardin, Neha

    2014-04-01

    Unlike pahoehoe, documentation of true a‧a lavas from a modern volcanological perspective is a relatively recent phenomenon in the Deccan Trap (e.g. Brown et al., 2011, Bull. Volcanol. 73(6): 737-752) as most lava flows previously considered to be a‧a (e.g. GSI, 1998) have been shown to be transitional (e.g. Rajarao et al., 1978, Geol. Soc. India Mem. 43: 401-414; Duraiswami et al., 2008 J. Volcanol. Geothermal. Res. 177: 822-836). In this paper we demonstrate the co-existence of autobrecciation products such as slabby pahoehoe, rubbly pahoehoe and a‧a in scattered outcrops within the dominantly pahoehoe flow fields. Although volumetrically low in number, the pattern of occurrence of the brecciating lobes alongside intact ones suggests that these might have formed in individual lobes along marginal branches and terminal parts of compound flow fields. Complete transitions from typical pahoehoe to 'a‧a lava flow morphologies are seen on length scales of 100-1000 m within road and sea-cliff sections near Uruli and Rajpuri. We consider the complex interplay between local increase in the lava supply rates due to storage or temporary stoppage, local increase in paleo-slope, rapid cooling and localized increase in the strain rates especially in the middle and terminal parts of the compound flow field responsible for the transitional morphologies. Such transitions are seen in the Thakurwadi-, Bushe- and Poladpur Formation in the western Deccan Traps. These are similar to pahoehoe-a‧a transitions seen in Cenozoic long lava flows (Undara ˜160 km, Toomba ˜120 km, Kinrara ˜55 km) from north Queensland, Australia and Recent (1859) eruption of Mauna Loa, Hawaii (a‧a lava flow ˜51 km) suggesting that flow fields with transitional tendencies cannot travel great lengths despite strong channelisation. If these observations are true, then it arguably limits long distance flow of Deccan Traps lavas to Rajahmundry suggesting polycentric eruptions at ˜65 Ma in

  11. Fracture patterns at lava-ice contacts on Kokostick Butte, OR, and Mazama Ridge, Mount Rainier, WA: Implications for flow emplacement and cooling histories

    Science.gov (United States)

    Lodge, Robert W. D.; Lescinsky, David T.

    2009-09-01

    Cooling lava commonly develop polygonal joints that form equant hexagonal columns. Such fractures are formed by thermal contraction resulting in an isotropic tensional stress regime. However, certain linear cooling fracture patterns observed at some lava-ice contacts do not appear to fit the model for formation of cooling fractures and columns because of their preferred orientations. These fracture types include sheet-like (ladder-like rectangular fracture pattern), intermediate (pseudo-aligned individual column-bounding fractures), and pseudopillow (straight to arcuate fractures with perpendicular secondary fractures caused by water infiltration) fractures that form the edges of multiple columns along a single linear fracture. Despite the relatively common occurrence of these types of fractures at lava-ice contacts, their significance and mode of formation have not been fully explored. This study investigates the stress regimes responsible for producing these unique fractures and their significance for interpreting cooling histories at lava-ice contacts. Data was collected at Kokostick Butte dacite flow at South Sister, OR, and Mazama Ridge andesite flow at Mount Rainier, WA. Both of these lava flows have been interpreted as being emplaced into contact with ice and linear fracture types have been observed on their ice-contacted margins. Two different mechanisms are proposed for the formation of linear fracture networks. One possible mechanism for the formation of linear fracture patterns is marginal bulging. Melting of confining ice walls will create voids into which flowing lava can deform resulting in margin-parallel tension causing margin-perpendicular fractures. If viewed from the ice-wall, these fractures would be steeply dipping, linear fractures. Another possible mechanism for the formation of linear fracture types is gravitational settling. Pure shear during compression and settling can result in a tensional environment with similar consequences as

  12. Variation of olivine composition in the volcanic rocks in the Songliao basin, NE China: lithosphere control on the origin of the K-rich intraplate mafic lavas

    Science.gov (United States)

    Zhang, L.-Y.; Prelević, D.; Li, N.; Mertz-Kraus, R.; Buhre, S.

    2016-10-01

    Lithospheric thickness and the heterogeneity of the mantle lithosphere are two major parameters that play a role in determining the final composition of the mafic melts and their minerals. The Songliao basin in northeast China represents an ideal natural laboratory to study the effect of these two parameters on early Pliocene to Holocene K-rich mafic lavas (K2O > 4 wt.%; K2O/Na2O > 1). A series of Cenozoic volcanic edifices (Erkeshan, Wudalianchi, Keluo and Xiaogulihe) are tentatively divided into three groups (Group 1 - thin, Group 2 - middle, and Group 3 - thick) according to the lithosphere thickness. They are located in the northern region of the Songliao basin extending in a near north-south direction along a broad zone where the lithosphere thickness increases gradually. We present a detailed petrographical and geochemical study on olivine macrocrysts in combination with new geochemical data on their host lavas, including major and trace element abundances as well as Sr, Nd, and Pb isotopic signatures. Our ultimate aim is to quantitatively and qualitatively determine the role of lithospheric mantle thickness (named as ;lid effect;) and composition in the variation of mafic lavas and olivine composition. When corrected to Mg# = 0.72, a number of major elements in the lavas correlate with increasing lithospheric thickness (L): Si72 and Al72 decrease, whereas Mg72, Fe72, Ti72 and P72 increase. Sm/Yb ratios in the lavas increase, implying that lithospheric thickness exerts an important control. Group 3 mafic lavas are ultrapotassic (showing lamproite affinity) with K2O/Na2O > 4: their La/Sm and Pb isotope ratios deviate from the above correlations, indicating that the lavas from the thickest part of the basin exhibit the highest extent of metasomatic enrichment of the mantle source. Several parameters (e.g. [Ni], Ni/Mg, Ni/(Mg/Fe), Mn/Fe and Ca/Fe) in melt-related olivine from Group 1 and Group 2 lavas are controlled by variable lithosphere thickness. Olivine

  13. High-resolution topography of 1974 Mount Etna lava flow based on Unmanned Aerial Vehicle (UAV) surveys and Structure from Motion (SfM) photogrammetry

    Science.gov (United States)

    Fornaciai, Alessandro; Favalli, Massimiliano; Nannipieri, Luca; Harris, Andrew; Calvari, Sonia; Lormand, Charline

    2017-04-01

    The production of high resolution Digital Elevation Models (DEMs) of lava is of increasing interest in volcanology because the time scales of change are fast and involve vertical and planimetric changes of millimeters to meters. Among the wide range of terrestrial and aerial methods available to collect topographic data, the use of unmanned aerial vehicle (UAV) acquiring platform and structure from motion (SfM) photogrammetric technique is especially useful because it allow collecting data of inaccessible, kilometer scale areas, with low cost and minimal hazard to personnel. This study presents the application of UAV-SfM method to generate a high-resolution DEMs and orthomosaic of the 1974 Mount Etna lava field. The UAV was flown over lava field at flight altitude to about 70 m above ground level (AGL) and acquired 2781 photographs. SfM-photogrammetry applied to these images enabled the extraction of very (20 cm) high-resolution DEMs and 3 cm orthomosaic for a total area of 1.35 square kilometers. The data produced by the UAV-SfM was compared with airborne LiDAR data. Such comparison gives a root mean squared error between the two DEMs of 0.24 m. The unprecedented topographic resolution obtained with UAV-SfM methods enabled us to derive morphometry of sub-meter-scale lava features, such as folds, blocks, and cracks, over kilometric scale areas. The 3 cm orthomosaic allowed us to further push the analysis to dm-scale grain distribution of the lava surface. This study shows that SfM and UAV platforms can be effectively used for mapping volcanic features producing topographic data in a manner not possible with the 1-m LiDAR-derived DEM. The spectral analysis of surface folding support this analysis showing a much larger spectrum of frequencies of the SfM-derived DEM than the LiDAR DEM.

  14. Breccia-cored columnar rosettes in a rubbly pahoehoe lava flow, Elephanta Island, Deccan Traps, and a model for their origin

    Directory of Open Access Journals (Sweden)

    Hetu Sheth

    2017-11-01

    Full Text Available Rubbly pahoehoe lava flows are abundant in many continental flood basalts including the Deccan Traps. However, structures with radial joint columns surrounding cores of flow-top breccia (FTB, reported from some Deccan rubbly pahoehoe flows, are yet unknown from other basaltic provinces. A previous study of these Deccan “breccia-cored columnar rosettes” ruled out explanations such as volcanic vents and lava tubes, and showed that the radial joint columns had grown outwards from cold FTB inclusions incorporated into the hot molten interiors. How the highly vesicular (thus low-density FTB blocks might have sunk into the flow interiors has remained a puzzle. Here we describe a new example of a Deccan rubbly pahoehoe flow with FTB-cored rosettes, from Elephanta Island in the Mumbai harbor. Noting that (1 thick rubbly pahoehoe flows probably form by rapid inflation (involving many lava injections into a largely molten advancing flow, and (2 such flows are transitional to ‘a’ā flows (which continuously shed their top clinker in front of them as they advance, we propose a model for the FTB-cored rosettes. We suggest that the Deccan flows under study were shedding some of their FTB in front of them as they advanced and, with high-eruption rate lava injection and inflation, frontal breakouts would incorporate this FTB rubble, with thickening of the flow carrying the rubble into the flow interior. This implies that, far from sinking into the molten interior, the FTB blocks may have been rising, until lava supply and inflation stopped, the flow began solidifying, and joint columns developed outward from each cold FTB inclusion as already inferred, forming the FTB-cored rosettes. Those rubbly pahoehoe flows which began recycling most of their FTB became the ‘a’ā flows of the Deccan.

  15. Numerical modelling of erosion and assimilation of sulfur-rich substrate by martian lava flows: Implications for the genesis of massive sulfide mineralization on Mars

    Science.gov (United States)

    Baumgartner, Raphael J.; Baratoux, David; Gaillard, Fabrice; Fiorentini, Marco L.

    2017-11-01

    Mantle-derived volcanic rocks on Mars display physical and chemical commonalities with mafic-ultramafic ferropicrite and komatiite volcanism on the Earth. Terrestrial komatiites are common hosts of massive sulfide mineralization enriched in siderophile-chalcophile precious metals (i.e., Ni, Cu, and the platinum-group elements). These deposits correspond to the batch segregation and accumulation of immiscible sulfide liquids as a consequence of mechanical/thermo-mechanical erosion and assimilation of sulfur-rich bedrock during the turbulent flow of high-temperature and low-viscosity komatiite lava flows. This study adopts this mineralization model and presents numerical simulations of erosion and assimilation of sulfide- and sulfate-rich sedimentary substrates during the dynamic emplacement of (channelled) mafic-ultramafic lava flows on Mars. For sedimentary substrates containing adequate sulfide proportions (e.g., 1 wt% S), our simulations suggest that sulfide supersaturation in low-temperature ( 1400 °C). The precious-metals tenor in the derived immiscible sulfide liquids may be significantly upgraded as a result of their prolonged equilibration with large volumes of silicate melts along flow conduits. The influence of sulfate assimilation on sulfide supersaturation in martian lava flows is addressed by simulations of melt-gas equilibration in the Csbnd Hsbnd Osbnd S fluid system. However, prolonged sulfide segregation and deposit genesis by means of sulfate assimilation appears to be limited by lava oxidation and the release of sulfur-rich gas. The identification of massive sulfide endowments on Mars is not possible from remote sensing data. Yet the results of this study aid to define regions for the potential occurrence of such mineral systems, which may be the large canyon systems Noctis Labyrinthus and Valles Marineris, or the Hesperian channel systems of Mars' highlands (e.g., Kasei Valles), most of which have been periodically draped by mafic

  16. The origin and significance of load-induced deformation structures in soft-sediment and lava at the base of the Archaean Ventersdorp Supergroup, South Africa

    Science.gov (United States)

    Hall, R. C. B.; Els, B. G.

    2002-07-01

    Many sedimentary deposits throughout the geologic record display structures that indicate the post-depositional disruption of their primary sedimentary features. Characteristically, the deformation, leading to irregular, broken or shifted stratification, takes place soon after deposition. The process of soft-sediment deformation, to which it is more commonly referred, can be attributed to four main mechanisms: reverse density gradation, liquefaction, slumping (slope deposit) and shear stress exerted by flow. Two or more of these mechanisms may act together and are notably described in purely sedimentary environments. As such, soft-sediment deformation can be considered an intra-formational response to the accumulation of a sediment pile, being largely confined to a single (sedimentary) bed, within undeformed (sedimentary) beds. However, deformation structures may also form where two compositionally and genetically contrasting substrates occur in intimate juxtaposition, as in the case of a volcano-sedimentary setting. Recognizable `soft-igneous' structures, analogous to those observed in sedimentary deposits, may form where lava flows have extruded over water-saturated sediments. In this instance, the lava `bed' substitutes for a sedimentary bed by inducing loading of the underlying sediments, resulting in the formation of deformation structures within both substrates, at their common interface. Such a situation commonly arises at the base of the Klipriviersberg Group, a±2000 m volcanic pile comprising the lower formations of the Ventersdorp Supergroup. Deformation structures in what was once soft-sediment and lava, commonly occur where lava flows comprising the basal Formation(s) of the Klipriviersberg Group overlie a pervasive, multi-lateral, multi-storey sand and gravel placer, the Ventersdorp Contact Reef (VCR). The VCR by definition forms the basal, (auriferous) conglomeratic portion of the Venterspost Conglomerate Formation (VCF) and is developed to varying

  17. Faults, Post-1720 Explosion Craters, and the Remains of a Lava Lake at Castro Bank Seamount (E Azores)

    Science.gov (United States)

    Wunderman, R.; Barriga, F. J.; Nishimura, C.; Pacheco, J. M.; Vogt, P. R.; Gaspar, J. L.; Queiroz, G.; Santos, R.

    2003-12-01

    During 25-28 July 2003 the US Navy submarine NR-1 dove on the seamount D. Joao de Castro Bank, compiling reconnaissance sonar and visual data. Castro Bank sits along strike and between the eastern Azorian islands of Terceira and S. Miguel, occupying a seismically active region ˜60 km from each of these islands and apparently controlled by the same underlying tectonics as other islands found along the Azores' northern margin. Castro Bank's last recorded eruptions built a ˜1 km diameter ephemeral island in the 1720s. The bathimetry of the uppermost 40 m or so of the Bank is rather well known via single beam sonar, scuba diving and AUV surveys (IH, DOP/UA and ISR/IST, unpublished work). Our dives compiled data in concentric rings along contours, collecting side- and forward-looking sonar along an overall track length of ˜20 km, with the deepest ring approaching ˜200 m depth. To document key features we came near the sea floor and took videos in water with typical visibility of ˜10-15 m. This is the first progress report on our work, which found the edifice morphologically complex and irregular. We noted that the seamount was often covered by aerially extensive yellow-brown hyaloclastic tuffs that were presumably products of the 1720s eruption, but also cut by faults and fissures (with offsets of ten's of meters) exposing abundant areas of older edifice. The faults typically lacked sediment cover, and in one case a very fresh, sediment-free fault trended along the base of a steep cliff. This suggested the faults were much younger than the 1720 eruption, an observation in accord with intense seismicity recorded in this area. The faults provided exposures of older rocks, which included abundant breccia and lesser clearly identified pillows or thick lava flows. The NW quadrant contains two small, shallow, elliptical craters. These lie side-by-side and crosscut inferred 1720s-age tuffs. One crater held a lava lake, the body of which apparently withdrew or subsided

  18. Factors controlling permeability and fluid flow within the 2004-2008 Mount St Helens lava dome complex

    Science.gov (United States)

    Gaunt, H. E.; Meredith, P. G.; Sammonds, P.; Smith, R.; Kilburn, C.

    2011-12-01

    Magma degassing is an important control on whether an eruption will be explosive or effusive. Although the process of gas exsolution has been well-studied, the factors that determine how gases subsequently escape are still poorly understood, especially from high-viscosity magmas with evolved compositions, such as dacite. A preferred model for viscous magmas is that shear fracturing during ascent can occur along conduit margins and lead to the development of a permeable fracture network. Such fracture networks facilitate gas escape and the effusion of magma as a lava dome or flow. The model, however, has yet to be tested against direct laboratory measurements on the potential for magma to develop permeable networks of fractures. Between 2004 and 2008, dacite magma was extruded almost continuously from Mount St Helens (Cascade Range, USA) as a succession of gas-poor and solidified lava spines. The dacite is thought to have solidified about 1 km below the vent and to have experienced intense strain localisation at the conduit margins during ascent. The most prominent of all the spines, Spine 4, formed a smooth 'whaleback' feature and had a distinct internal structure analogous to that of a tectonic fault zone. Extruded dacite lava was coated with a thick (~1m) layer of fault gouge, containing multiple sets of sub-parallel slickensides and shear bands orientated preferentially in the direction of spine growth. To investigate the controls on degassing processes, we have measured how permeability varied progressively with increasing temperature and deformation on samples from the 2004-2008 dome at Mount St Helens. Permeability was measured on cylindrical samples, 25 mm in diameter, in a hydrostatic permeameter at confining pressures up to 30 MPa (a depth of c.1.2 km) and, also, in a high temperature deformation apparatus at temperatures up to 900oC, confining pressures of 12 MPa and pore fluid pressures of 4 MPa. Samples of intact dacite from the interior of Spine 4 were

  19. Diverse lavas from closely spaced volcanoes drawing from a common parent: Emmons Lake Volcanic Center, Eastern Aleutian Arc

    Science.gov (United States)

    Mangan, M.; Miller, T.; Waythomas, C.; Trusdell, F.; Calvert, A.; Layer, P.

    2009-01-01

    Emmons Lake Volcanic Center (ELVC) on the lower Alaskan Peninsula is one of the largest and most diverse volcanic centers in the Aleutian Arc. Since the Middle Pleistocene, eruption of ~ 350 km3 of basalt through rhyolite has produced a 30 km, arc front chain of nested calderas and overlapping stratovolcanoes. ELVC has experienced as many as five major caldera-forming eruptions, the most recent, at ~ 27 ka, produced ~ 50 km3 of rhyolitic ignimbrite and ash fall. These violent silicic events were interspersed with less energetic, but prodigious, outpourings of basalt through dacite. Holocene eruptions are mostly basaltic andesite to andesite and historically recorded activity includes over 40 eruptions within the last 200 yr, all from Pavlof volcano, the most active site in the Aleutian Arc. Geochemical and geophysical observations suggest that although all ELVC eruptions derive from a common clinopyroxene + spinel + plagioclase fractionating high-aluminum basalt parent in the lower crust, magma follows one of two closely spaced, but distinct paths to the surface. Under the eastern end of the chain, magma moves rapidly and cleanly through a relatively young (~ 28 ka), hydraulically connected dike plexus. Steady supply, short magma residence times, and limited interaction with crustal rocks preserve the geochemistry of deep crustal processes. Below the western part of the chain, magma moves haltingly through a long-lived (~ 500 ka) and complex intrusive column in which many generations of basaltic to andesitic melts have mingled and fractionated. Buoyant, silicic melts periodically separate from the lower parts of the column to feed voluminous eruptions of dacite and rhyolite. Mafic lavas record a complicated passage through cumulate zones and hydrous silicic residues as manifested by disequilibrium phenocryst textures, incompatible element enrichments, and decoupling of REEs and HFSEs ratios. Such features are absent in mafic lavas from the younger part of the chain

  20. The dynamics of post-collapse magmatism at rhyolitic calderas: Analogue experiments and geochemistry of Yellowstone lavas

    Science.gov (United States)

    Girard, Guillaume

    The dynamics of magma replenishment in silicic magma reservoirs are not well understood. This is an important issue, since replenishment may lead to the rapid accumulation of large volumes of crystal-poor magma, a condition potentially leading to cataclysmic caldera-forming eruptions. To shed light on this process, I have undertaken a combined experimental---geochemical approach designed to provide an integrated and synthetic view of magma replenishment processes. Scaled analogue experiments show that in silicic systems, buoyant injections rise through a magma reservoir without significant mixing with resident material, forming a layered reservoir. When a crystal mush is present at the base of the reservoir, its presence does not hinder buoyant injections to ascend. Indeed, such injections entrain crystals from the mush and transport them to the uppermost layers of the reservoir, resulting in the accumulation of a mix of replenishing magma and mush crystals. This process may have played a significant role in the generation of early post-collapse rhyolites of Yellowstone caldera, the Upper Basin Member rhyolites. In these lavas, I observe the coexistence of large, isolated, sieved plagioclase crystals with small, fresh, more calcic plagioclase crystals occurring as aggregates with pyroxenes and oxides. This unusual mineral assemblage suggests that a higher-temperature, more primitive silicic replenishing magma mixed with crystals from a mush shortly before eruption. In this scenario, the aggregates crystallized from the replenishing magma while the sieved crystals were extracted from the mush. Unlike the Upper Basin Member rhyolites, the younger voluminous Central Plateau Member rhyolites define a cogenetic series in which younger lavas exhibit more evolved mineralogy and trace element signatures, while crystal geochemistry suggests crystallization from progressively cooler melts. At the same time, the crystals also exhibit dissolution textures, suggesting a

  1. Influence of porcelain veneering on the marginal fit of Digident and Lava CAD/CAM zirconia ceramic crowns.

    Science.gov (United States)

    Pak, Hyun-Soon; Han, Jung-Suk; Lee, Jai-Bong; Kim, Sung-Hun; Yang, Jae-Ho

    2010-06-01

    Marginal fit is a very important factor considering the restoration's long-term success. However, adding porcelain to copings can cause distortion and lead to an inadequate fit which exposes more luting material to the oral environment and causes secondary caries. The purpose of this study was to compare the marginal fit of 2 different all-ceramic crown systems before and after porcelain veneering. This study was also intended to verify the marginal fit of crowns originated from green machining of partially sintered blocks of zirconia (Lava CAD/CAM system) and that of crowns obtained through machining of fully sintered blocks of zirconia (Digident CAD/CAM system). 20 crowns were made per each system and the marginal fit was evaluated through a light microscope with image processing (Accura 2000) at 50 points that were randomly selected. Each crown was measured twice: the first measurement was done after obtaining a 0.5 mm coping and the second measurement was done after porcelain veneering. The means and standard deviations were calculated and statistical inferences among the 2 groups were made using independent t-test and within the same group through paired t-test. The means and standard deviations of the marginal fit were 61.52 ± 2.88 µm for the Digident CAD/CAM zirconia ceramic crowns before porcelain veneering and 83.15 ± 3.51 µm after porcelain veneering. Lava CAD/CAM zirconia ceramic crowns showed means and standard deviations of 62.22 ± 1.78 µm before porcelain veneering and 82.03 ± 1.85 µm after porcelain veneering. Both groups showed significant differences when analyzing the marginal gaps before and after porcelain veneering within each group. However, no significant differences were found when comparing the marginal gaps of each group before porcelain veneering and after porcelain veneering as well. The 2 all-ceramic crown systems showed marginal gaps that were within a reported clinically acceptable range of marginal discrepancy.

  2. Functional and Biochemical Characterization of Three Recombinant Human Glucose-6-Phosphate Dehydrogenase Mutants: Zacatecas, Vanua-Lava and Viangchan

    Science.gov (United States)

    Gómez-Manzo, Saúl; Marcial-Quino, Jaime; Vanoye-Carlo, America; Serrano-Posada, Hugo; González-Valdez, Abigail; Martínez-Rosas, Víctor; Hernández-Ochoa, Beatriz; Sierra-Palacios, Edgar; Castillo-Rodríguez, Rosa Angélica; Cuevas-Cruz, Miguel; Rodríguez-Bustamante, Eduardo; Arreguin-Espinosa, Roberto

    2016-01-01

    Glucose-6-phosphate dehydrogenase (G6PD) deficiency in humans causes severe disease, varying from mostly asymptomatic individuals to patients showing neonatal jaundice, acute hemolysis episodes or chronic nonspherocytic hemolytic anemia. In order to understand the effect of the mutations in G6PD gene function and its relation with G6PD deficiency severity, we report the construction, cloning and expression as well as the detailed kinetic and stability characterization of three purified clinical variants of G6PD that present in the Mexican population: G6PD Zacatecas (Class I), Vanua-Lava (Class II) and Viangchan (Class II). For all the G6PD mutants, we obtained low purification yield and altered kinetic parameters compared with Wild Type (WT). Our results show that the mutations, regardless of the distance from the active site where they are located, affect the catalytic properties and structural parameters and that these changes could be associated with the clinical presentation of the deficiency. Specifically, the structural characterization of the G6PD Zacatecas mutant suggests that the R257L mutation have a strong effect on the global stability of G6PD favoring an unstable active site. Using computational analysis, we offer a molecular explanation of the effects of these mutations on the active site. PMID:27213370

  3. Formation of cordierite-bearing lavas during anatexis in the lower crust beneath Lipari Island (Aeolian arc, Italy)

    Science.gov (United States)

    Di, Martino C.; Forni, F.; Frezzotti, M.L.; Palmeri, R.; Webster, J.D.; Ayuso, R.A.; Lucchi, F.; Tranne, C.A.

    2011-01-01

    Cordierite-bearing lavas (CBL;~105 ka) erupted from the Mt. S. Angelo volcano at Lipari (Aeolian arc, Italy) are high-K andesites, displaying a range in the geochemical and isotopic compositions that reflect heterogeneity in the source and/or processes. CBL consist of megacrysts of Ca-plagioclase and clinopyroxene, euhedral crystals of cordierite and garnet, microphenocrysts of orthopyroxene and plagioclase, set in a heterogeneous rhyodacitic-rhyolitic groundmass containing abundant metamorphic and gabbroic xenoliths. New petrographic, chemical and isotopic data indicate formation of CBL by mixing of basaltic-andesitic magmas and high-K peraluminous rhyolitic magmas of anatectic origin and characterize partial melting processes in the lower continental crust of Lipari. Crustal anatectic melts generated through two main dehydration-melting peritectic reactions of metasedimentary rocks: (1) Biotite + Aluminosilicate + Quartz + Albite = Garnet + Cordierite + K-feldspar + Melt; (2) Biotite + Garnet + Quartz = Orthopyroxene + Cordierite + K-feldspar + Melt. Their position into the petrogenetic grid suggests that heating and consequent melting of metasedimentary rocks occurred at temperatures of 725 < T < 900??C and pressures of 0.4-0.45 GPa. Anatexis in the lower crust of Lipari was induced by protracted emplacement of basic magmas in the lower crust (~130 Ky). Crustal melting of the lower crust at 105 ka affected the volcano evolution, impeding frequent maficmagma eruptions, and promoting magma stagnation and fractional crystallization processes. ?? 2011 Springer-Verlag.

  4. Pleniglacial sedimentation process reconstruction on laminated lacustrine sediments from lava-dammed Paleolake Alf, West Eifel Volcanic Field (Germany)

    Science.gov (United States)

    Eichhorn, Luise; Pirrung, Michael; Zolitschka, Bernd; Büchel, Georg

    2017-09-01

    Differentiating between regularly seasonal, irregular and event-based clastic sedimentation is difficult if sedimentation structures resemble and dating methods are imprecise. In this study - clastic light and dark laminae from lava-dammed Paleolake Alf in the Late Pleistocene in the Quaternary West Eifel Volcanic Field are analyzed to clarify how they formed and if they are of annual origin and comparable to assumed periglacial varves from neighboring Lake Holzmaar. Therefore, a multiproxy approach is applied combining sediment thin section analysis which focuses on composition and structure with 14C dates. The results are compared to recently-formed annually-laminated clastic sediments of, e.g., the High Canadian Arctic. Observed sedimentation structures reveal sediment delivery by over- and interflows and deposition from suspension forming two characteristic microfacies: Type I graded laminae and Type II laminae with graded sublayers. Additionally, erosional bases and event deposits indicate episodic underflows. Thus, lamination is potentially seasonal but is significantly veiled by extreme runoff causing erosion and resuspension processes or a mixed water body preventing sediment delivery into the lake basin. However, sedimentation processes between watershed and lake could be reconstructed by comparing recent and paleosediment structures.

  5. Palaeomagnetic intensities from 14C-dated lava flows on the Big Island, Hawaii: 0-21 kyr

    Science.gov (United States)

    Pressling, Nicola; Laj, Carlo; Kissel, Catherie; Champion, Duane E.; Gubbins, David

    2006-01-01

    Thellier–Thellier experiments were carried out on 216 lava samples collected by the USGS on the Big Island. 35 individual flows from the Kilauea, Mauna Loa and Hualalai volcanoes are represented and independent radiocarbon dating of the flows yields absolute ages ranging from 290 to 20,240 yrs old. The palaeomagnetic analysis was carried out at the Laboratoire des Sciences du Climat et de l'Environnement in Gif-sur-Yvette, France, in two custom built, large capacity furnaces that have been specifically designed to minimise oxidation. The temperature steps were adapted to accommodate the characteristic loss of magnetisation at low temperatures seen in the Curie balance results and the use of half-size samples allowed secondary experiments to be carried out where necessary. The strict PICRIT-03 selection criteria were rigorously applied to the data and a high success rate of 53% has been achieved on a sample level. The flow averaged results almost double the existing 14C-dated palaeointensity dataset for this time window and confirm a period of high intensity over the past 4 kyr preceded by a period in which the dipole moment was weaker. However, the values attained in this study are on average higher than previously published data; reliability of these values is discussed.

  6. Functional and Biochemical Characterization of Three Recombinant Human Glucose-6-Phosphate Dehydrogenase Mutants: Zacatecas, Vanua-Lava and Viangchan.

    Science.gov (United States)

    Gómez-Manzo, Saúl; Marcial-Quino, Jaime; Vanoye-Carlo, America; Serrano-Posada, Hugo; González-Valdez, Abigail; Martínez-Rosas, Víctor; Hernández-Ochoa, Beatriz; Sierra-Palacios, Edgar; Castillo-Rodríguez, Rosa Angélica; Cuevas-Cruz, Miguel; Rodríguez-Bustamante, Eduardo; Arreguin-Espinosa, Roberto

    2016-05-21

    Glucose-6-phosphate dehydrogenase (G6PD) deficiency in humans causes severe disease, varying from mostly asymptomatic individuals to patients showing neonatal jaundice, acute hemolysis episodes or chronic nonspherocytic hemolytic anemia. In order to understand the effect of the mutations in G6PD gene function and its relation with G6PD deficiency severity, we report the construction, cloning and expression as well as the detailed kinetic and stability characterization of three purified clinical variants of G6PD that present in the Mexican population: G6PD Zacatecas (Class I), Vanua-Lava (Class II) and Viangchan (Class II). For all the G6PD mutants, we obtained low purification yield and altered kinetic parameters compared with Wild Type (WT). Our results show that the mutations, regardless of the distance from the active site where they are located, affect the catalytic properties and structural parameters and that these changes could be associated with the clinical presentation of the deficiency. Specifically, the structural characterization of the G6PD Zacatecas mutant suggests that the R257L mutation have a strong effect on the global stability of G6PD favoring an unstable active site. Using computational analysis, we offer a molecular explanation of the effects of these mutations on the active site.

  7. Functional and Biochemical Characterization of Three Recombinant Human Glucose-6-Phosphate Dehydrogenase Mutants: Zacatecas, Vanua-Lava and Viangchan

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    Saúl Gómez-Manzo

    2016-05-01

    Full Text Available Glucose-6-phosphate dehydrogenase (G6PD deficiency in humans causes severe disease, varying from mostly asymptomatic individuals to patients showing neonatal jaundice, acute hemolysis episodes or chronic nonspherocytic hemolytic anemia. In order to understand the effect of the mutations in G6PD gene function and its relation with G6PD deficiency severity, we report the construction, cloning and expression as well as the detailed kinetic and stability characterization of three purified clinical variants of G6PD that present in the Mexican population: G6PD Zacatecas (Class I, Vanua-Lava (Class II and Viangchan (Class II. For all the G6PD mutants, we obtained low purification yield and altered kinetic parameters compared with Wild Type (WT. Our results show that the mutations, regardless of the distance from the active site where they are located, affect the catalytic properties and structural parameters and that these changes could be associated with the clinical presentation of the deficiency. Specifically, the structural characterization of the G6PD Zacatecas mutant suggests that the R257L mutation have a strong effect on the global stability of G6PD favoring an unstable active site. Using computational analysis, we offer a molecular explanation of the effects of these mutations on the active site.

  8. The ‘exceptional finds’ of Iruña-Veleia (Álava: syntax of an archaeological forgery

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    Ignacio RODRÍGUEZ TEMIÑO

    2017-06-01

    Full Text Available In 2006, news broke of the discovery of ostraca bearing text in Latin and Basque, as well as Christian drawings, during the 2005 and 2006 excavation campaigns at the Iruña-Veleia site in Álava, Spain. In 2008, these pieces were shown to be fakes. The ‘Iruña-Veleia case’, as it has come to be known, has been the subject of several partial studies, primarily focused on the forgeries. This paper will analyse it from a contextual perspective. To this end, it first defines the general pattern, or ‘syntax’, followed by historical forgeries. It then applies this syntax to the Iruña-Veleia case, reviewing how it unfolded in the academic, political, institutional and social spheres. In each one, the syntax showed certain oddities, mainly due to the social context in which the events took place and their link to nationalist identity, a subject related to the content of the forged specimens. Despite this link, however, in this case it cannot be concluded that nationalism was the driving force behind the forgery.

  9. Geomagnetic field secular variation in Pacific Ocean: A Bayesian reference curve based on Holocene Hawaiian lava flows

    Science.gov (United States)

    Tema, E.; Herrero-Bervera, E.; Lanos, Ph.

    2017-11-01

    Hawaii is an ideal place for reconstructing the past variations of the Earth's magnetic field in the Pacific Ocean thanks to the almost continuous volcanic activity during the last 10 000 yrs. We present here an updated compilation of palaeomagnetic data from historic and radiocarbon dated Hawaiian lava flows available for the last ten millennia. A total of 278 directional and 66 intensity reference data have been used for the calculation of the first full geomagnetic field reference secular variation (SV) curves for central Pacific covering the last ten millennia. The obtained SV curves are calculated following recent advances on curve building based on the Bayesian statistics and are well constrained for the last five millennia while for older periods their error envelopes are wide due to the scarce number of reference data. The new Bayesian SV curves show three clear intensity maxima during the last 3000 yrs that are accompanied by sharp directional changes. Such short-term variations of the geomagnetic field could be interpreted as archaeomagnetic jerks and could be an interesting feature of the geomagnetic field variation in the Pacific Ocean that should be further explored by new data.

  10. PETROGENESIS AND TECTONIC IMPLICATION OF THE NEOPROTEROZOIC BONINITIC-THOLEIITIC LAVAS AND MAGNESIAN ANDESITES IN THE GORNY ALTAI TERRANE, NORTHWESTERN CENTRAL ASIAN OROGENIC BELT

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    Ming Chen

    2017-01-01

    Full Text Available The late Neoproterozoic tholeiitic-boninitic lavas and minor magnesian andesites cropping out in the Kurai Ridge, southeast of the Gorny Altai terrane, represent magmatic products of the nascent Kuznetsk-Altai intra-oceanic island arc southwest off the Siberian continent. Samples of these rocks can provide key information about sub-arc mantle and slab-mantle interaction during the early phase of ocean-ocean subduction.

  11. The Kilauea 1974 Flow: Quantitative Morphometry of Lava Flows using Low Altitude Aerial Image Data using a Kite-based Platform in the Field

    Science.gov (United States)

    Scheidt, S. P.; Whelley, P.; Hamilton, C.; Bleacher, J. E.; Garry, W. B.

    2015-12-01

    The December 31, 1974 lava flow from Kilauea Caldera, Hawaii within the Hawaii Volcanoes National Park was selected for field campaigns as a terrestrial analog for Mars in support of NASA Planetary Geology and Geophysics (PGG) research and the Remote, In Situ and Synchrotron Studies for Science and Exploration (RIS4E) node of the Solar System Exploration Research Virtual Institute (SSERVI) program). The lava flow was a rapidly emplaced unit that was strongly influenced by existing topography, which favored the formation of a tributary lava flow system. The unit includes a diverse range of surface textures (e.g., pāhoehoe, ´áā, and transitional lavas), and structural features (e.g., streamlined islands, pits, and interactions with older tumuli). However, these features are generally below the threshold of visibility within previously acquired airborne and spacecraft data. In this study, we have generated unique, high-resolution digital images using low-altitude Kite Aerial Photography (KAP) system during field campaigns in 2014 and 2015 (National Park Service permit #HAVO-2012-SCI-0025). The kite-based mapping platform (nadir-viewing) and a radio-controlled gimbal (allowing pointing) provided similar data as from an unmanned aerial vehicle (UAV), but with longer flight time, larger total data volumes per sortie, and fewer regulatory challenges and cost. Images acquired from KAP and UAVs are used to create orthomosaics and DEMs using Multi-View Stereo-Photogrammetry (MVSP) software. The 3-Dimensional point clouds are extremely dense, resulting in a grid resolution of < 2 cm. Airborne Light Detection and Ranging (LiDAR) / Terrestrial Laser Scanning (TLS) data have been collected for these areas and provide a basis of comparison or "ground truth" for the photogrammetric data. Our results show a good comparison with LiDAR/TLS data, each offering their own unique advantages and potential for data fusion.

  12. Identification of iron-bearing minerals in basalts and pillow lavas of the Kaczawa Mountains using 57Fe Mössbauer spectroscopy

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    Malczewski Dariusz

    2017-06-01

    Full Text Available The Kaczawa Mountains along with the Kaczawa foothill comprise a complicated geological unit that is called the Kaczawa metamorphic (Sudetes, SW Poland. The aim of our work was to identify the iron-bearing minerals in samples of basalts and pillow lavas from the Kaczawa metamorphic using 57Fe Mössbauer spectroscopy. Based on the preliminary results, the Fe3+/Fe2+ ratio in the samples was determined.

  13. Deformation patterns in a high-viscosity lava flow inferred from the crystal preferred orientation and imbrication structures: an example from Salina (Aeolian Islands, southern Tyrrhenian Sea, Italy)

    Science.gov (United States)

    Ventura, Guido; Rosa, Rosanna De; Colletta, Elena; Mazzuoli, Roberto

    1996-04-01

    Shape-preferred orientation and imbrication structures of crystals have been measured on samples representative of the base, centre and top of a highly viscous lava flow on Salina (Aeolian Islands, southern Tyrrhenian Sea). The data allow zones with different deformation patterns to be identified. In the base and top of the flow, deformation leads to the development of discrete preferred orientation and imbrication of the elongate crystals. The sense of shear is right-lateral at the base and left-lateral at the top of the flow. Shear strain can be estimated by the analysis of crystal preferred orientation. Deformation increases from the flow centre to the outer, more viscous boundary layers. Random orientation of crystals in the inner zone supports the presence of plug flow in a pseudoplastic lava. The textural features of the studied lava may be related to different mechanisms (i.e. lateral expansion). We conclude that the observed crystal alignments and imbrication structures may be related to a plug flow moving between two non-deforming walls. The walls are represented by the solidified, broken upper and basal crust of the flow. The low shear strain values calculated in the outer margins of the flow are indicative of the last deformation event. Crystal preferred orientation and imbrication structures may be related to the occurrence of velocity gradients existing between the inner zone of the flow and its solidus or near-solidus outer margins.

  14. Statistical analysis of the sustained lava dome emplacement and destruction processes at Popocatépetl volcano, Central México

    Science.gov (United States)

    Mendoza-Rosas, Ana Teresa; Gómez-Vázquez, Ángel; De la Cruz-Reyna, Servando

    2017-06-01

    Popocatépetl volcano reawakened in 1994 after nearly 70 years of quiescence. Between 1996 and 2015, a succession of at least 38 lava domes have been irregularly emplaced and destroyed, with each dome reaching particular volumes at specific emplacement rates. The complexity of this sequence is analyzed using statistical methods in an attempt to gain insight into the physics and dynamics of the lava dome emplacement and destruction process and to objectively assess the hazards related to that volcano. The time series of emplacements, dome residences, lava effusion lulls, and emplaced dome volumes and thicknesses are modeled using the simple exponential and Weibull distributions, the compound non-homogeneous generalized Pareto-Poisson process (NHPPP), and the mixture of exponentials distribution (MOED). The statistical analysis reveals that the sequence of dome emplacements is a non-stationary, self-regulating process most likely controlled by the balance between buoyancy-driven magma ascent and volatile exsolution crystallization. This balance has supported the sustained effusive activity for decades and may persist for an undetermined amount of time. However, the eruptive history of Popocatépetl includes major Plinian phases that may have resulted from a breach in that balance. Certain criteria to recognize such breaching conditions are inferred from this statistical analysis.

  15. Palaeomagnetic refinement of the eruption ages of Holocene lava flows, and implications for the eruptive history of the Tongariro Volcanic Centre, New Zealand

    Science.gov (United States)

    Greve, Annika; Turner, Gillian M.; Conway, Chris E.; Townsend, Dougal B.; Gamble, John A.; Leonard, Graham S.

    2016-11-01

    We present a detailed palaeomagnetic study from 35 sites on Holocene lava flows of the Tongariro Volcanic Centre, central North Island, New Zealand. Prior to the study the eruption ages of these flows were constrained to within a few thousand years by recently published high-precision 40Ar/39Ar geochronological data and tephrostratigraphic controls. Correlation of flow mean palaeomagnetic directions with a recently published continuous sediment record from Lake Mavora, Fiordland, allows us to reduce the age uncertainty to 300-500 yr in some cases. Our refined ages significantly improve the chronology of Holocene effusive eruptions of the volcanoes of the Tongariro Volcanic Centre. For instance, differences in the palaeomagnetic directions recorded by lavas from the voluminous Iwikau and Rangataua members suggest that individual effusive periods lasted up to thousands of years and that these bursts have been irregularly spaced over time. While over the last few millennia the effusive eruptive activity from Mt Ruapehu has been relatively quiet, the very young age (200-500 BP) of a Red Crater sourced flow suggests that effusive activity around Mt Tongariro lasted into the past few centuries. This adds an important hazard context to the historical record, which has otherwise comprised frequent relatively small, tephra producing, explosive eruptions without the production of lava flows.

  16. Chlorine degassing during the lava dome-building eruption of Mount St. Helens, 2004-2005: Chapter 27 in A volcano rekindled: the renewed eruption of Mount St. Helens, 2004-2006

    Science.gov (United States)

    Edmonds, Marie; McGee, Kenneth A.; Doukas, Michael P.; Sherrod, David R.; Scott, William E.; Stauffer, Peter H.

    2008-01-01

    Remote measurements of volcanic gases from the Mount St. Helens lava dome were carried out using OpenPath Fourier-Transform Infrared spectroscopy on August 31, 2005. Measurements were performed at a site ~1 km from the lava dome, which was used as a source of IR radiation. On average, during the period of measurement, the volcanic gas contained 99 mol percent H2

  17. Channel and tube flow features associated with the Twin Craters Lava Flow, Zuni-Bandera Volcanic Field, NM: Insights into similar features on Mars

    Science.gov (United States)

    Samuels, R.; deWet, A.; Bleacher, J. E.; von Meerscheidt, H. C.; Hamilton, C.; Garry, W. B.

    2013-12-01

    The Zuni-Bandera Volcanic Field lies near the center of the Jemez lineament that extends from central Arizona to northeastern New Mexico. The Jemez lineament is a result of rifting in the Earth's crust and is associated with volcanic activity that spans the last 16 Ma. The youngest volcanic activity associated with the lineament includes basaltic lava that was erupted 3 ka ago to form the McCartys Flow. The Twin Craters flow is moderately older (18.0 ka), but it also well-preserved and provides an ideal location to investigate volcanic processes and landforms. In this study, we combined detailed field observations and mapping with remote sensing to better understand variations in morphology along the transport system of the flow . The Twin Craters flow is characterized as an aā and tube-fed pāhoehoe flow with braided or branching tubes and channels; and associated aā and pāhoehoe break-outs. It is possible that the variations in morphology along the same transport structure might be related to pre-flow slope, which might have also been variable along flow. Shatter ring features are thought to be related to changes in eruption rate, and therefore, local flux through the system. However, over-pressurization of the tube might also be related to changes in local discharge rate associated with the ponding and release of lava within the transport system that may be due to interactions between the lava and obstacles along the flow's path (see Mallonee et al., this meeting). Many of these features are similar to features present in the Tharsis Montes region of Mars and particularly on the southern apron of Ascraeus Mons. The detailed description of the morphology of the Twin Craters Lava Flow and the understanding of the emplacement mechanisms will be crucial in identifying the processes that formed the Ascraeus flows and channels. This will aid in determining if the lava surface textures are directly related to eruption conditions or if they have been significantly

  18. Appraisal of the new occurrence of götzenite ss, khibinskite and apophyllite in kalsilite-bearing lavas from San Venanzo and Cupaello (Umbria), Italy

    Science.gov (United States)

    Cundari, A.; Ferguson, A. J.

    1994-01-01

    Minerals corresponding in chemical composition to probable götzenite solid solutions, götzenite ss, ideally (Ca, Na) 3 (Ti, Zr) (Si 2O 7) (F, O, OH) 2, khibinskite (K 4Zr 2Si 4O 14) and apophyllite (KCa 4Si 8O 20(OH, F)) were first reported in an aphyric, glass-bearing kalsilitite from Cupaello (Umbria), Italy, by Cundari and Ferguson (1991). To the authors knowledge, this occurrence of khibinskite is only the second recorded. Götzenite ss was also found in a leucite-, melilite-rich pegmatoid in an olivine-melilitite from San Venanzo, S. Venanzo, in the same region. The S. Venanzo phase, with significant Zr (0.18 atoms per formula unit) is transitional to rosenbuschite, which is the Zr-rich end-member of the isostructural series götzenite-rosenbuschite, while that from Cupaello, virtually Zr free, is close to the ideal götzenite end-member. The S. Venanzo phase crystallized as the preferred Zr phase from the relatively low-Zr (Zr=335 ppm) S. Venanzo lava. This probably inhibited khibinskite crystallization in the S. Venanzo lava, whereas khibinskite is the preferred Zr phase in the Cupaello lava (Zr=760 ppm), coexisting with low-Zr götzenite ss. The structural formula of the Cupaello khibinskite, based on 10 cations, yielded: K 3.89[Zr 1.99Mg 0.01Fe 0.042+Ti 0.02] 2.06Si 4.05O 14.1 which is very close to the composition first reported by Khomiakov et al. (1974). Apophyllite, also occurring in the Cupaello assemblages and in cavities in the lava, yielded a composition close to the ideal formula and supports the important role of alkali-rich fluids in the crystallization history of this lava. The rare records of these minerals reflect, at least in part, the difficulty in identifying them. Their role as potential acceptors of both large ion lithophile and high field strength elements in peralkaline rock compositions is important in understanding the geochemistry of lamproitic rocks and in detecting possible genetic links with related rocks.

  19. Magma ascent and lava dome evolution at Volcán de Colima, Mexico

    Science.gov (United States)

    Varley, N. R.; Arámbula, R.; Lavallée, Y.; Bernstein, M.; Ryan, A. G.; Maskell, A.

    2009-12-01

    The transition between explosive and effusive activity can be triggered by subtle variations in parameters which dictate the efficiency and speed of degassing from an ascending magma body. Indirect methods have to be utilized to constrain these parameters, to test and refine numerical models, which ultimately permit a more powerful interpretation of monitoring data. Recent activity at Volcán de Colima has included many transitions between different regimes, offering a great opportunity to examine conduit processes. Explosive activity peaked in 2005 with 30 Vulcanian eruptions producing pyroclastic flows, some reaching >5km from the volcano. Each event was associated with a swarm of long-period (LP) seismic events. A poor correlation between swarm characteristics and the size of the explosion suggests independence between the source mechanisms of each phenomenon. The LP events were divided into 10 families, all of which reappeared in different swarms and the majority continued to occur after the Vulcanian explosion. This is evidence of the complexity of the upper edifice, with the source regions for the LP events remaining unaffected by the explosions. We believe they are produced by brittle deformation once a certain strain-rate threshold has been surpassed. The explosions were associated with rapidly ascending magma bodies that were degassing and crystallizing near the surface, each one being destroyed in the subsequent explosion. Magma sometimes reached the crater, with small short-lived domes being observed. In some cases a post-explosion increase in amplitude of the LP events might have reflected an increase in effusion rate after an unloading of material higher in the vent. Volcán de Colima has produced 5 episodes of effusive activity in the last 11 years. These have been of variable duration and intensity, with over 2 orders of magnitude variation in the effusion rate. The current phase has been characterised by a remarkably sustained (from Jan. 07 to at

  20. Alteration mineralogy, mineral chemistry and stable isotope geochemistry of the Eocene pillow lavas from the Trabzon area, NE Turkey

    Science.gov (United States)

    Abdioğlu Yazar, Emel

    2018-02-01

    The Eocene subaqueous volcanic units in NE Turkey developed as pillow, closely packed pillow, isolated pillow, pillow breccia, hyaloclastite breccia and rare peperitic facies with red micritic limestones. They are locally set on volcaniclastic sandstone and claystone alternations and gradually pass to tuffs and volcanic breccias. The pillow lava samples generally exhibit intersertal, intergranular, microlitic porphyritic, variolitic, vesicular and glomeroporphyritic and glassy textures with clinopyroxene (Wo47-52En40-45Fs6-8), plagioclase (An10 to An96), olivine (Fo79-87) and Fe-Ti oxides (Usp0-0.27). Saponite, interlayered chlorite/saponite, rare beidellite and calcite were determined after olivine, rarely after plagioclase as well as in the glassy groundmass. Illite was restricted to plagioclase and the glassy groundmass. Na-Ca zeolites, chlorites/saponites, beidellite, dolomite and calcite occur as void infillings and in the glassy groundmass. Mineralogical, lithochemical and isotopic interpretations as well as thermometric calculations reveal a low-temperature seawater alteration in a semi-closed environment for the alteration of primary minerals and volcanic glass in addition to sealed vesicles and open systems for crosscutting veins. Due to the short exposure time intervals of seawater to rocks, the total chemistry of the rocks is not fully changed and most of the elements seem to be immobile, remaining in the system as a result of precipitation in voids and cracks. Thermometric estimations indicate that, the temperature of heated seawater is approximately 160 °C at the highest point especially in the vesicles, and decreases to approximately 85 °C due to circulation, resulting in alterations of the primary phases and volcanic glass.

  1. A Multi-Sensor Approach for Volcanic Ash Cloud Retrieval and Eruption Characterization: The 23 November 2013 Etna Lava Fountain

    Directory of Open Access Journals (Sweden)

    Stefano Corradini

    2016-01-01

    Full Text Available Volcanic activity is observed worldwide with a variety of ground and space-based remote sensing instruments, each with advantages and drawbacks. No single system can give a comprehensive description of eruptive activity, and so, a multi-sensor approach is required. This work integrates infrared and microwave volcanic ash retrievals obtained from the geostationary Meteosat Second Generation (MSG-Spinning Enhanced Visible and Infrared Imager (SEVIRI, the polar-orbiting Aqua-MODIS and ground-based weather radar. The expected outcomes are improvements in satellite volcanic ash cloud retrieval (altitude, mass, aerosol optical depth and effective radius, the generation of new satellite products (ash concentration and particle number density in the thermal infrared and better characterization of volcanic eruptions (plume altitude, total ash mass erupted and particle number density from thermal infrared to microwave. This approach is the core of the multi-platform volcanic ash cloud estimation procedure being developed within the European FP7-APhoRISM project. The Mt. Etna (Sicily, Italy volcano lava fountaining event of 23 November 2013 was considered as a test case. The results of the integration show the presence of two volcanic cloud layers at different altitudes. The improvement of the volcanic ash cloud altitude leads to a mean difference between the SEVIRI ash mass estimations, before and after the integration, of about the 30%. Moreover, the percentage of the airborne “fine” ash retrieved from the satellite is estimated to be about 1%–2% of the total ash emitted during the eruption. Finally, all of the estimated parameters (volcanic ash cloud altitude, thickness and total mass were also validated with ground-based visible camera measurements, HYSPLIT forward trajectories, Infrared Atmospheric Sounding Interferometer (IASI satellite data and tephra deposits.

  2. The geomagnetic field intensity in New Zealand: palaeointensities from Holocene lava flows of the Tongariro Volcanic Centre

    Science.gov (United States)

    Greve, Annika; Hill, Mimi J.; Turner, Gillian M.; Nilsson, Andreas

    2017-11-01

    Very few absolute palaeointensity data exist from Holocene-aged rocks in New Zealand. Here we present a new suite of high-quality palaeointensities, supported by detailed rock magnetic investigations. Samples from 23 sites representing 10 distinct eruptive units of the Tongariro Volcanic Centre, Taupo Volcanic Zone, New Zealand, were studied. Both traditional double heating and microwave palaeointensity methods were employed. The reliability of the palaeointensity data varies with rock magnetic properties of the samples, corresponding, in particular, to their positions within the lava flows. The highest success rates are from samples obtained from near the flow tops where a significant proportion of the remanence unblocked at intermediate temperatures (200-350 °C). By contrast, samples from flow centres, particularly the parts showing platey fracturing, have the lowest success rates. Reliable, high-quality palaeointensity results ranging from 32.4 ± 5.1 μT to 72.1 ± 4.7 μT were obtained from six flows with ages between c. 12 800 yr BP and the present. These correspond to virtual dipole moments that increase from 52 ± 10 ZAm2 in the early Holocene and peak at 112 ± 14 ZAm2 about 300 yr ago. The data agree well with calibrated relative palaeointensities from New Zealand lake sediments. The volcanic and sedimentary data together yield a Holocene virtual axial dipole moment curve that fits the global average variation well in the early Holocene, but which differs significantly in recent millennia. This difference is associated with recent migration of the southern high latitude core-mantle boundary flux lobe towards New Zealand, as is seen in global field models.

  3. Geochemistry of Mesozoic Basaltic Lavas from the West Pacific Seamount Province (WPSP): Constraints on Their Origin and Genesis

    Science.gov (United States)

    Yan, Q.; Shi, X.

    2014-12-01

    There distributed many relatively isolated seamounts in several inferred seamount chains in west Pacific, and the area has been named as west Pacific seamount province (WPSP). Studying on basaltic rocks from the WPSP will be helpful to better understanding the diversity of plume geodymanics and developing the plume theory. Basaltic lavas from eight seamounts in the WPSP have been studied for petrography, major-, trace element and Sr-Nd-Pb isotopic composition. The petrographic characteristics of these rocks show moderately to highly altered. Major element compositions show all of these rocks belong to alkalic series, and some samples lost their alkalis elements during submarine seawater alteration. Primitive mantle normalized spider diagram and chondrite normalized rare earth element distributional pattern show that they were originated from OIB-like source and possibly underwent low degree partial melting. Isotopic characteristics imply that three mantle end-members (DMM, EMI and HIMU) can explain Sr-Nd-Pb compositions of these rocks from the WPSP, i.e., DMM is depleted MORB mantle identical to that being created MORB in EPR, EMI (reprecented by Rarotonga island) is possibly from subducted ancient continental crust, and HIMU (represented by Cook-Austral Islands) is typically originated from recycled oceanic crust. Based on the present study combined with published data, we proposed that the origin of some (maybe all) of seamounts in the WPSP are splash plumes proposed by Davies and Bunge (2006) or smaller plumes branched at the base of lithosphere from the Superwell which has created the Ontong Java plateau. (This work was supported by the National Natural Science Foundation of China under contract Nos. 41322036, and 41276003)

  4. Enriched continental flood basalts from depleted mantle melts: modeling the lithospheric contamination of Karoo lavas from Antarctica

    Science.gov (United States)

    Heinonen, Jussi S.; Luttinen, Arto V.; Bohrson, Wendy A.

    2016-01-01

    Continental flood basalts (CFBs) represent large-scale melting events in the Earth's upper mantle and show considerable geochemical heterogeneity that is typically linked to substantial contribution from underlying continental lithosphere. Large-scale partial melting of the cold subcontinental lithospheric mantle and the large amounts of crustal contamination suggested by traditional binary mixing or assimilation-fractional crystallization models are difficult to reconcile with the thermal and compositional characteristics of continental lithosphere, however. The well-exposed CFBs of Vestfjella, western Dronning Maud Land, Antarctica, belong to the Jurassic Karoo large igneous province and provide a prime locality to quantify mass contributions of lithospheric and sublithospheric sources for two reasons: (1) recently discovered CFB dikes show isotopic characteristics akin to mid-ocean ridge basalts, and thus help to constrain asthenospheric parental melt compositions and (2) the well-exposed basaltic lavas have been divided into four different geochemical magma types that exhibit considerable trace element and radiogenic isotope heterogeneity (e.g., initial ɛ Nd from -16 to +2 at 180 Ma). We simulate the geochemical evolution of Vestfjella CFBs using (1) energy-constrained assimilation-fractional crystallization equations that account for heating and partial melting of crustal wall rock and (2) assimilation-fractional crystallization equations for lithospheric mantle contamination by using highly alkaline continental volcanic rocks (i.e., partial melts of mantle lithosphere) as contaminants. Calculations indicate that the different magma types can be produced by just minor (1-15 wt%) contamination of asthenospheric parental magmas by melts from variable lithospheric reservoirs. Our models imply that the role of continental lithosphere as a CFB source component or contaminant may have been overestimated in many cases. Thus, CFBs may represent major juvenile crustal

  5. Crustal structure beneath the High Lava Plains of eastern Oregon and surrounding regions from receiver function analysis

    Science.gov (United States)

    Eagar, Kevin C.; Fouch, Matthew J.; James, David E.; Carlson, Richard W.

    2011-02-01

    We analyze teleseismic P-to-S receiver functions to image crustal structure beneath the High Lava Plains (HLP) of eastern Oregon and surrounding regions. Coverage from 206 broadband seismic stations provides the first opportunity to resolve variations in crustal composition, thickness, and heterogeneity on scales of a few km in depth and tens of km laterally across the HLP region. We utilize both H - κ stacking and a new Gaussian-weighted common conversion point stacking technique. We find crust that is ≥40 km thick beneath the Cascades, Idaho Batholith, and Owyhee Plateau and thinner (˜31 km) crust beneath the HLP and northern Great Basin. Low Poisson's ratios of ˜0.240 characterize the granitic crust beneath the Idaho Batholith, while the Owyhee Plateau exhibits values of ˜0.270, typical of average continental crust. The Owyhee Plateau is a thick simple crustal block with distinct edges at depth. The western HLP exhibits high average values of 0.304, typical for regions of widespread basaltic volcanism. Combined with other geological and geophysical observations, the areas of abnormally high Poisson's ratios (˜0.320) and low-velocity zones in the crust beneath north-central and southern Oregon are consistent with the presence of partial melt on either side of the HLP trend, suggesting a central zone where crustal melts have drained to the surface, perhaps enabled by the Brothers Fault Zone. Thicker crust and an anomalous N-S band of low Poisson's ratios (˜0.252) skirting the Steens Mountain escarpment is consistent with residuum from a midcrustal magma source of the massive flood basalts, supporting the view of extensive mafic underplating and intraplating of the crust from Cenozoic volcanism.

  6. Digital evidence

    Directory of Open Access Journals (Sweden)

    Lukić Tatjana

    2012-01-01

    Full Text Available Although computer makes human activities faster and easier, innovating and creating new forms of work and other kinds of activities, it also influenced the criminal activity. The development of information technology directly affects the development of computer forensics without which, it can not even imagine the discovering and proving the computer offences and apprehending the perpetrator. Information technology and computer forensic allows us to detect and prove the crimes committed by computer and capture the perpetrators. Computer forensics is a type of forensics which can be defined as a process of collecting, preserving, analyzing and presenting digital evidence in court proceedings. Bearing in mind, that combat against crime, in which computers appear as an asset or object of the offense, requires knowledge of digital evidence as well as specific rules and procedures, the author in this article specifically addresses the issues of digital evidence, forensic (computer investigation, specific rules and procedures for detecting, fixing and collecting digital evidence and use of this type of evidence in criminal proceedings. The author also delas with international standards regarding digital evidence and cyber-space investigation.

  7. Pairing Geochemistry with Geophysical Models to Constrain the Petrogenesis of Age-Progressive Rhyolites from the High Lava Plains and Northwest Basin and Range, Oregon

    Science.gov (United States)

    Ford, M. T.; Grunder, A.; Carlson, R. W.; Cox, C. M.

    2012-12-01

    Over the past 12 Ma, the High Lava Plains (HLP) and northwestern Basin and Range (NWBR) of Oregon have been adjacent areas of bimodal, basalt-rhyolite volcanism. Rhyolitic volcanism in both provinces is age-progressive, tracking to the west-northwest, and is temporally decoupled from the tholeiitic basalts which show no such spatial relationship. The rhyolites are temporally linked but geochemically distinct in some major and trace elements and isotopic (Sr, Nd, Pb) compositions indicating that rhyolites in this region can have a different origins. These differences are caused primarily by the amount of mantle-derived basalt and state of transtension in the crust. We speculate that the basaltic flux is produced by asthenospheric flow which is caused by the steepening and retreating Cascadia slab and is the only geodynamic mantle feature required to produce the age-progressive silicic volcanism in the HLP and NWBR. The HLP has experienced less extension and a significantly greater flux of mantle-derived basalts, based on the volumes of eruptive products and crustal densities derived from seismic refraction models. Increased crustal densities suggest that basaltic magmas stall in the mid to lower crust (intraplate). Other workers have shown that low silica rhyolites can be produced by partial melts of mafic protoliths, which in this case are likely recently emplaced mantle-derived basaltic magmas in mid to lower crustal "hot zones". These low silica rhyolites coalesce and buoyantly rise into the upper crust where they differentiate into high silica rhyolites. Likewise, basaltic andesites form by differentiation of basalts in upper crustal regions. Rare mixes of basaltic andesite and rhyolite produce intermediate (andesite and dacite) compositions in this upper-crustal region. A few rhyolites show evidence of minor assimilation of earlier Cenozoic volcanic products but anatexis of older, accreted terranes and associated plutons is precluded. Mantle-sourced magma flux

  8. Petrogenesis of Tertiary continental intra-plate lavas between Siebengebirge and Westerwald, Germany: Constraints from trace element systematics and Nd, Sr and Pb isotopes

    Science.gov (United States)

    Schubert, S.; Jung, S.; Pfänder, J. A.; Hauff, F.; Garbe-Schönberg, D.

    2015-10-01

    fractionation has occurred. Miocene intraplate basaltic volcanism in the area probably occurred as a result of minor "baby plume" activity. Each volcanic plug records evidence of a specific stage of fractionation with or without assimilation; however, in summary the lavas plot on a single fractionation path. This implies that during evolution of the volcanic field initial melting took place in the asthenosphere or at the lithosphere-asthenosphere interface. The melts moved through the lithospheric mantle and stagnated at crustal levels, however the observed fractionation paths suggest that they were fed from a single reservoir. This model, which involves small-scale plume impact followed by asthenosphere-lithosphere interaction together with minor crustal contamination, should also be applicable to other intra-continental rift-related areas.

  9. Evolución del grado de implantación de programas de autocontrol en las piscinas de temporada en Araba/Álava Evolution of the implementation level of self-monitoring programmes for outdoor swimming pools in Araba/Álava Evolução do grau de implementação de programas de autocontrolo em piscinas sazonais em Araba/Álava

    OpenAIRE

    Arantza Armentia Álvarez; Nagore Irazabal Tamayo; Raquel Hernández García

    2012-01-01

    El objetivo principal de este estudio ha sido realizar una valoración de la evolución del grado de implantación de programas de autocontrol en las piscinas descubiertas de Araba/Álava durante seis años (2006-2011). Para ello, en las inspecciones se cumplimentaron protocolos de comprobación basados en instrucciones técnicas, elaboradas para aunar criterios y valorar los diferentes planes del Programa de autocontrol (Estos planes son: 1. Tratamiento y vigilancia del agua; 2. Análisis del agua; ...

  10. High-resolution TanDEM-X DEM: An accurate method to estimate lava flow volumes at Nyamulagira Volcano (D. R. Congo)

    Science.gov (United States)

    Albino, F.; Smets, B.; d'Oreye, N.; Kervyn, F.

    2015-06-01

    Nyamulagira and Nyiragongo are two of the most active volcanoes in Africa, but their eruptive histories are poorly known. Assessing lava flow volumes in the region remains difficult, as field surveys are often impossible and available Digital Elevation Models (DEMs) do not have adequate spatial or temporal resolutions. We therefore use TerraSAR-X add-on for Digital Elevation Measurement (TanDEM-X) interferometry to produce a series of 0.15 arc sec (˜5 m) DEMs from between 2011 and 2012 over these volcanoes. TanDEM-X DEMs have an absolute vertical accuracy of 1.6 m, resulting from the comparison of elevation with GPS measurements acquired around Nyiragongo. The difference between TanDEM-X-derived DEMs from before and after the 2011-2012 eruption of Nyamulagira provides an accurate thickness map of the lava flow emplaced during that activity. Values range from 3 m along the margins to 35 m in the middle, with a mean of 12.7 m. The erupted volume is 305.2 ± 36.0 × 106 m3. Height errors on thickness depend on the land covered by the flow and range from 0.4 m in old lavas to 5.5 m in dense vegetation. We also reevaluate the volume of historical eruptions at Nyamulagira since 2001 from the difference between TanDEM-X and SRTM 1 arc sec DEMs and compare them to previous work. Planimetric methods used in literature are consistent with our results for short-duration eruptions but largely underestimate the volume of the long-lived 2011-2012 eruption. Our new estimates of erupted volumes suggest that the mean eruption rate and the magma supply rate were relatively constant at Nyamulagira during 2001-2012, respectively, 23.1 m3 s-1 and 0.9 m3 s-1.

  11. Flow analyses for the LAVA-ERVC experiment and the KSNP under the external reactor vessel cooling using RELAP5/MOD3 code

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Kyoung-Ho; Park, Rae-Joon; Cho, Young-Ro; Kim, Sang-Baik

    2005-01-01

    Flow analyses were performed using RELAP5/MOD3 code to investigate and verify the steam binding phenomena in the LAVA-ERVC experiment and to investigate the occurrence and the effects of steam binding for the KSNP under the external reactor vessel cooling. Flow analyses for the LAVA-ERVC experiments confirmed the steam binding occurrence in case of the limited steam venting and represented the LAVA-ERVC experimental results quite well. The flow analyses results for the KSNP under the external reactor vessel cooling address that water ingression and steam ventilation through the insulator are crucial factors determining the effective cool down via boiling heat removal at the outer surface of the RPV lower plenum. The flow analyses results for the base cases of the SBO and the 9.6 inch LBLOCA imply that the limited steam venting through the insulator induced the steam binding and eventually prevented the effective cooling at the outer surface of the RPV lower plenum. From the sensitivity study on the additional flow area for the steam venting, it could be found that the RPV lower plenum experienced effective cooling by smooth water circulation. The current RELAP5 flow analyses results for the KSNP under the external reactor vessel cooling address that prevention of steam binding phenomena should be settled first for the in-vessel corium retention through the external reactor vessel cooling. Implementation of additional flow path for the effective steam ventilation is highly recommended as one of the most promising countermeasures to enhance the coolability through the external reactor vessel cooling.

  12. Lack of direct evidence for natural selection at the candidate thrifty gene locus, PPARGC1A.

    Science.gov (United States)

    Cadzow, Murray; Merriman, Tony R; Boocock, James; Dalbeth, Nicola; Stamp, Lisa K; Black, Michael A; Visscher, Peter M; Wilcox, Phillip L

    2016-11-15

    The gene PPARGC1A, in particular the Gly482Ser variant (rs8192678), had been proposed to be subject to natural selection, particularly in recent progenitors of extant Polynesian populations. Reasons include high levels of population differentiation and increased frequencies of the derived type 2 diabetes (T2D) risk 482Ser allele, and association with body mass index (BMI) in a small Tongan population. However, no direct statistical tests for selection have been applied. Using a range of Polynesian populations (Tongan, Māori, Samoan) we re-examined evidence for association between Gly482Ser with T2D and BMI as well as gout. Using also Asian, European, and African 1000 Genome Project samples a range of statistical tests for selection (F ST , integrated haplotype score (iHS), cross population extended haplotype homozygosity (XP-EHH), Tajima's D and Fay and Wu's H) were conducted on the PPARGC1A locus. No statistically significant evidence for association between Gly482Ser and any of BMI, T2D or gout was found. Population differentiation (F ST ) was smallest between Asian and Pacific populations (New Zealand Māori ≤ 0.35, Samoan ≤ 0.20). When compared to European (New Zealand Māori ≤ 0.40, Samoan ≤ 0.25) or African populations (New Zealand Māori ≤ 0.80, Samoan ≤ 0.66) this differentiation was larger. We did not find any strong evidence for departure from neutral evolution at this locus when applying any of the other statistical tests for selection. However, using the same analytical methods, we found evidence for selection in specific populations at previously identified loci, indicating that lack of selection was the most likely explanation for the lack of evidence of selection in PPARGC1A. We conclude that there is no compelling evidence for selection at this locus, and that this gene should not be considered a candidate thrifty gene locus in Pacific populations. High levels of population differentiation at this locus and the

  13. Satellite-Based Thermophysical Analysis of Volcaniclastic Deposits: A Terrestrial Analog for Mantled Lava Flows on Mars

    Directory of Open Access Journals (Sweden)

    Mark A. Price

    2016-02-01

    example. Accurate identification of non-mantled lava surfaces within an apparently well-mantled flow field on either planet provides locations to extract important mineralogical constraints on the individual flows using TIR data.

  14. Petrologic Insights into the Triggering Mechanism for the Lava Creek Tuff Super-Eruption, Yellowstone Caldera, WY

    Science.gov (United States)

    Shamloo, H. I.; Till, C. B.

    2016-12-01

    Yellowstone's most recent caldera-forming eruption occurred 631,000 years ago and was responsible for producing the >1000 km3 Lava Creek Tuff (LCT), which was deposited over most of contiguous United States. The LCT contains zoned sanidine (55 vol. %) and quartz (35%) phenocrysts, along with minor plagioclase and clinopyroxene (8%), magnetite and ilmenite (2%). This study takes two approaches to interrogate the mechanisms leading to eruption recorded in the LCT: 1) the application of feldspar thermometry to chemically zoned sanidine from LCT Member B ash analyzed via electron probe, and 2) modeling the phase equilibria for the LCT using rhyolite-MELTS. Sanidine-liquid thermometry yields average temperatures of 820-840°C (±22°C) for the sanidine rims, and suggests a slight heating trend from core to rim. The major element composition of the outermost sanidine rims reveals two distinct drops in orthoclase content that coincide with sharp increases in barium content. When compared to the feldspar compositions predicted by MELTS, these sharp changes in composition each require temperature increases of ≥25°C and are interpreted to reflect two magmatic rejuvenation events shortly before eruption. MELTS models best align with the feldspar thermometry at relatively low water contents (e.g., 1-2 wt.% H2O) and suggest the LCT may be drier than previously thought (Gansecki et al., Geology, 1998). The crystallization sequence predicted by MELTS for the LCT at 3 kbar includes quartz as the liquidus phase at 1000°C, precipitation of the first feldspar at 950°C, followed by precipitation of two feldspar phases (sanidine and albite) below the feldspar solvus at 850°C, with the ternary minimum and water exsolution occurring at 740°C. Despite the uncertainty in the absolute temperatures of the phase boundaries predicted by MELTS, the phase proportions and feldspar compositions in the LCT suggest that the last feldspar crystallization prior to eruption occurred well above

  15. Multi-phase saturation experiments on the Oldoinyo Lengai natrocarbonatite lavas: derived from a sodic-potassic calciocarbonatite through fractionation

    Science.gov (United States)

    Weidendorfer, D.; Schmidt, M. W.; Mattsson, H. B.

    2015-12-01

    Typical natrocarbonatite eruption temperatures are 490-595°C and are at least 200-300°C lower than temperatures for any suitable silicic liquid that could be conjugate across a miscibility gap. In particular, the 2007 Oldoinyo Lengai (OL) eruption delivered a mix of nephelinitic and carbonatite melts, supporting the commonly accepted supposition that carbonatites are conjugate to spatially associated peralkaline nephelinites. We constrain possible parental melt compositions of the natrocarbonatites by saturation with calcite, apatite, cpx, wollastonite, nepheline, combeite or nyerereite (at 1 kbar, 650-1200°C, fast-quench cold-seal vessels); all occurring in the silicate or carbonatite rocks of OL The results show that the natrocarbonatite is highly undersaturated in calcite and apatite. At 1200°C, calcite saturation results in decreasing Na2O+K2O from initially 41.5 to 10.3 wt% while the CaCO3-component is increased to 80 wt%. In the complex system, there is no thermal (nyerereite-fairchildite) maximum, hence fractionation of calcite+apatite may proceed from a parent melt with 15 wt% alkali and 70% Ca-component to the observed OL natrocarbonatites. The observed melt inclusions in phenocrysts in the nephelinites at Keramasi (Guzmics et al. 2012, CMP) would serve as ideal parents, these melt compositions correspond to 1050oC. The modelled liquid line of descent along the calcite surface requires a total fractionation of ~48% calcite and ~9 wt% apatite. SiO2 solubility only increases from 0.2-2.9 wt% at 750-1200°C, leaving little leeway for reaction with silicates. A peritectic reaction among the above silicates conserving the Si-content in the carbonatite could not be identified. At >950°C cpx yields, through peritectic melting, an immiscible peralkaline silicate melt + extensive wollastonite (as observed in OL cumulates). This experimental silicate melt resembles the unusual silicate ash compositions from the 2007 eruption. The natrocarbonatite lavas from OL

  16. Ties of Heat and Mass Transport Properties in Glasses and Melts, with Emphasis on Natural Lava Compositions

    Science.gov (United States)

    Hofmeister, A. M.; Whittington, A. G.; Robert, G.; Sehlke, A.

    2016-12-01

    We have discovered strong ties of mass and heat transport properties in glasses and melts via coordinated measurements of thermal diffusivity (D) and viscosity (η). Over the course of several studies we have compared over 50 remelted natural lavas, tektites, and synthetic glasses and melts, with substantially different chemical compositions, e.g., from 50 to 100% silica, and with slight variations in H and Fe cations and the presence/absence of Al. We use laser flash analysis to obtain D, which avoids contact and radiative errors and constrain η over a wide range of temperature (T). We use a combination of parallel-plate and concentric-cylinder viscometry to obtain η from the glass transition to above the liquidus. Our most recent studies include differential scanning calorimetric measurements of heat capacity (CP) to calculate their thermal conductivity (k), and we are now measuring thermal expansivity using dilatometry. The combined datasets show consistent macroscopic behavior, providing an improved understanding of microscopic behavior, particularly of heat transport properties, which have been misunderstood. Both viscosity and the glass transition temperature decrease with decreasing melt polymerization. Clear correlations exist between D of glass or melt with Si content, density, NBO/T, and, most strongly, with fragility (obtained from η). Glass thermal diffusivity is represented by D = FT-G +HT, where F, G and H are fitting parameters. For melts, D drops upon melting but we could only resolve D/T for a small number of samples. The results show that high-T behavior is controlled by Fe oxidation state and polymerization and involves radiative transfer (HT) but at infrared frequencies. In disordered materials, acoustic scattering is less important to heat transfer than is IR absorption/re-emissions. We find that k for glasses is described by a Maier-Kelly formula, consistent with the T response being dominated by CP. Trends in k are irregular due to k being

  17. Textural variations and fragmentation processes in peperite formed between felsic lava flow and wet substrate: An example from the Cretaceous Buan Volcanics, southwest Korea

    Science.gov (United States)

    Gihm, Yong Sik; Kwon, Chang Woo

    2017-02-01

    Multiple exposures of peperite within the Cretaceous Buan Volcanics, southwest Korea, have been examined in order to determine variations in their textural characteristics and to investigate their mode of formation. Along undulating boundaries between rhyolite (lava flow) and deformed host sediment expressed as a series of load and flame structures, exposures commonly contain two distinct types of peperite. Type-1 peperites are composed mostly of rounded juvenile clasts at their base and polyhedral juvenile clasts at their upper levels, interpreted to have formed via a two-stage process. Firstly, abrasion of juvenile clasts occurred after their fragmentation due to shear stress imparted by the overlying and still-moving lava flow, forming rounded juvenile clasts. Subsequent in situ quenching fragmentation of the lava flow produced clasts with platy to polyhedral shapes immediately after emplacement of the lava flow. Type-2 peperites laterally extend into the interior of featureless rhyolite as layers that decrease in thickness with increasing distance away from the flame zone. These layers exhibit horizontal textural variations, ranging from poorly sorted mixtures of ash- to block-sized angular juvenile clasts in the proximal zone, to closely packed polyhedral and tabular juvenile clasts with jigsaw-crack textures in the middle and distal zones. Type-2 peperite are inferred to have formed due to internal steam explosions that resulted from an expansion of heated pore water (leading to an increase in pore fluid pressure) that had been vertically injected into the interior of the rhyolite from the flame zone. The proximal zone, composed mainly of poorly sorted mixtures of juvenile clasts, represents the explosion sites. Juvenile clasts in the middle and distal zones are interpreted to have formed due to three separate processes: the development of fractures in the rhyolite during the internal steam explosions, injection of the host sediment through the fractures, and

  18. Olivine-Respiring Bacteria Isolated from the Rock-Ice Interface in a Lava-Tube Cave, a Mars Analog Environment

    OpenAIRE

    Popa, Radu; Smith, Amy R.; Popa, Rodica; Boone, Jane; Fisk, Martin

    2012-01-01

    The boundary between ice and basalt on Earth is an analogue for some near-surface environments of Mars. We investigated neutrophilic iron-oxidizing microorganisms from the basalt-ice interface in a lava tube from the Oregon Cascades with perennial ice. One of the isolates (Pseudomonas sp. HerB) can use ferrous iron Fe(II) from the igneous mineral olivine as an electron donor and O2 as an electron acceptor. The optimum growth temperature is ∼12–14°C, but growth also occurs at 5°C. Bicarbonate ...

  19. Análisis antropológico de los restos humanos de la necrópolis medieval de Quintana (Leza, Álava

    Directory of Open Access Journals (Sweden)

    Fernández Crespo, T.

    2010-01-01

    Full Text Available Se presenta una síntesis de los resultados obtenidos en el estudio antropológico de más de un centenar de sujetos inhumados en la necrópolis medieval de Quintana (Leza, Álava, la cual muestra un excepcional número de amortizaciones o reutilizaciones sepulcrales. Se evidencia un esquema demográfico caracterizado por un inusual predominio del colectivo subadulto. Destacan asimismo la preeminencia de tallas medianas y la presencia de artropatías degenarativas como patologías más comunes.

  20. Magmatic degassing, lava dome extrusion, and explosions from Mount Cleveland volcano, Alaska, 2011–2015: Insight into the continuous nature of volcanic activity over multi-year timescales

    Science.gov (United States)

    Werner, Cynthia; Kern, Christoph; Coppola, Diego; Lyons, John; Kelly, Peter; Wallace, Kristi; Schneider, David; Wessels, Rick

    2017-01-01