Sample records for basaltic lava flows

  1. Similarities in basalt and rhyolite lava flow emplacement processes (United States)

    Magnall, Nathan; James, Mike; Tuffen, Hugh; Vye-Brown, Charlotte


    Here we use field observations of rhyolite and basalt lava flows to show similarities in flow processes that span compositionally diverse lava flows. The eruption, and subsequent emplacement, of rhyolite lava flows is currently poorly understood due to the infrequency with which rhyolite eruptions occur. In contrast, the emplacement of basaltic lava flows are much better understood due to very frequent eruptions at locations such as Mt Etna and Hawaii. The 2011-2012 eruption of Cordón Caulle in Chile enabled the first scientific observations of the emplacement of an extensive rhyolite lava flow. The 30 to 100 m thick flow infilled a topographic depression with a negligible slope angle (0 - 7°). The flow split into two main channels; the southern flow advanced 4 km while the northern flow advanced 3 km before stalling. Once the flow stalled the channels inflated and secondary flows or breakouts formed from the flow front and margins. This cooling rather than volume-limited flow behaviour is common in basaltic lava flows but had never been observed in rhyolite lava flows. We draw on fieldwork conducted at Cordón Caulle and at Mt Etna to compare the emplacement of rhyolite and basaltic flows. The fieldwork identified emplacement features that are present in both lavas, such as inflation, breakouts from the flow font and margins, and squeeze-ups on the flow surfaces. In the case of Cordón Caulle, upon extrusion of a breakout it inflates due to a combination of continued lava supply and vesicle growth. This growth leads to fracturing and breakup of the breakout surface, and in some cases a large central fracture tens of metres deep forms. In contrast, breakouts from basaltic lava flows have a greater range of morphologies depending on the properties of the material in the flows core. In the case of Mt Etna, a range of breakout morphologies are observed including: toothpaste breakouts, flows topped with bladed lava as well as breakouts of pahoehoe or a'a lava. This

  2. Field Detection of Chemical Assimilation in A Basaltic Lava Flow (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.


    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.

  3. The Influence of Topographic Obstacles on Basaltic Lava Flow Morphologies (United States)

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


    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.

  4. Rock magnetic evidence of inflation of a flood basalt lava flow (United States)

    Cañón-Tapia, Edgardo; Coe, Robert


    The anisotropy of magnetic susceptibility (AMS) of lava flows is an innovative method which has been proved to be directly related to the shear history of lava. One of the advantages of this method is that it can be used in the absence of other morphological features commonly employed to study the mechanism of emplacement of lava flows. This feature of the AMS method makes it very attractive to gain insight into the mechanism of emplacement of massive, relatively featureless, long lava flows such as those forming flood basalt provinces. In this work, we report the results of the measurement of AMS as a function of vertical position within the Birkett lava flow, one of the Columbia River Basalt Group flows. The observed variation of AMS allows us to identify at least 16 discrete events of lava injection and to estimate the thickness of individual injection events. The AMS-estimated thickness of each injection event (in the range of 0.5-4.0 m) coincides with the range inferred for injected lava pulses in modern Hawaiian lava flows. Thus, the evidence provided by the AMS method supports the notion that at least some flood basalt lava flows were emplaced by the same mechanism as many present-day inflated pahoehoe flows. Regarding the orientation of the principal susceptibilities, in the central part of the flow they define a preferred orientation along an E-W trend, whereas in the outer parts of the flow they have a NNE-SSW trend. This difference in the orientation of the principal susceptibilities is interpreted as the result of a change of flow direction of the lava as emplacement progressed. Electronic supplementary material to this paper can be obtained by using the Springer LINK server located at

  5. Impact of environmental factors on the spectral characteristics of lava surfaces:field spectrometry of basaltic lava flows on Tenerife, Canary Islands, Spain


    Long Li; Carmen Solana; Frank Canters; Jonathan C.-W. Chan; Matthieu Kervyn


    We report on spectral reflectance measurements of basaltic lava flows on Tenerife Island, Spain. Lava flow surfaces of different ages, surface roughness and elevations were systematically measured using a field spectroradiometer operating in the range of 350–2500 nm. Surface roughness, oxidation and lichen coverage were documented at each measured site. Spectral properties vary with age and morphology of lava. Pre-historical lavas with no biological coverage show a prominent increase in spect...

  6. One-, two- and three-phase viscosity treatments for basaltic lava flows. (United States)

    Harris, Andrew J L; Allen, John S


    Lava flows comprise three-phase mixtures of melt, crystals, and bubbles. While existing one-phase treatments allow melt phase viscosity to be assessed on the basis of composition, water content, and/or temperature, two-phase treatments constrain the effects of crystallinity or vesicularity on mixture viscosity. However, three-phase treatments, allowing for the effects of coexisting crystallinity and vesicularity, are not well understood. We investigate existing one- and two-phase treatments using lava flow case studies from Mauna Loa (Hawaii) and Mount Etna (Italy) and compare these with a three-phase treatment that has not been applied previously to basaltic mixtures. At Etna, melt viscosities of 425 ± 30 Pa s are expected for well-degassed (0.1 w. % H(2)O), and 135 ± 10 Pa s for less well-degassed (0.4 wt % H(2)O), melt at 1080°C. Application of a three-phase model yields mixture viscosities (45% crystals, 25-35% vesicles) in the range 5600-12,500 Pa s. This compares with a measured value for Etnean lava of 9400 ± 1500 Pa s. At Mauna Loa, the three-phase treatment provides a fit with the full range of field measured viscosities, giving three-phase mixture viscosities, upon eruption, of 110-140 Pa s (5% crystals, no bubble effect due to sheared vesicles) to 850-1400 Pa s (25-30% crystals, 40-60% spherical vesicles). The ability of the three-phase treatment to characterize the full range of melt-crystal-bubble mixture viscosities in both settings indicates the potential of this method in characterizing basaltic lava mixture viscosity.

  7. Emplacement history and inflation evidence of a long basaltic lava flow located in Southern Payenia Volcanic Province, Argentina (United States)

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


    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.

  8. Impact of Environmental Factors on the Spectral Characteristics of Lava Surfaces: Field Spectrometry of Basaltic Lava Flows on Tenerife, Canary Islands, Spain

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    Long Li


    Full Text Available We report on spectral reflectance measurements of basaltic lava flows on Tenerife Island, Spain. Lava flow surfaces of different ages, surface roughness and elevations were systematically measured using a field spectroradiometer operating in the range of 350–2500 nm. Surface roughness, oxidation and lichen coverage were documented at each measured site. Spectral properties vary with age and morphology of lava. Pre-historical lavas with no biological coverage show a prominent increase in spectral reflectance in the 400–760 nm range and a decrease in the 2140–2210 nm range. Pāhoehoe surfaces have higher reflectance values than ʻaʻā ones and attain a maximum reflectance at wavelengths < 760 nm. Lichen-covered lavas are characterized by multiple lichen-related absorption and reflection features. We demonstrate that oxidation and lichen growth are two major factors controlling spectra of Tenerife lava surfaces and, therefore, propose an oxidation index and a lichen index to quantify surface alterations of lava flows: (1 the oxidation index is based on the increase of the slope of the spectral profile from blue to red as the field-observed oxidation level strengthens; and (2 the lichen index is based on the spectral reflectance in the 1660–1725 nm range, which proves to be highly correlated with lichen coverage documented in the field. The two spectral indices are applied to Landsat ETM+ and Hyperion imagery of the study area for mapping oxidation and lichen coverage on lava surfaces, respectively. Hyperion is shown to be capable of discriminating different volcanic surfaces, i.e., tephra vs. lava and oxidized lava vs. lichen-covered lava. Our study highlights the value of field spectroscopic measurements to aid interpretation of lava flow characterization using satellite images and of the effects of environmental factors on lava surface evolution over time, and, therefore, has the potential to contribute to the mapping as well as dating

  9. Vertical AMS variation within basalt flow profiles from the Xitle volcano (Mexico) as indicator of heterogeneous strain in lava flows (United States)

    Caballero-Miranda, C. I.; Alva-Valdivia, L. M.; González-Rangel, J. A.; Gogitchaishvili, A.; Urrutia-Fucugauchi, J.; Kontny, A.


    The within-flow vertical variation of anisotropy of the magnetic susceptibility (AMS) of three basaltic flow profiles from the Xitle volcano were investigated in relation to the lava flow-induced shear strain. Rock magnetic properties and opaque microscopy studies have shown that the magnetic mineralogy is dominated by Ti-poor magnetite with subtle vertical variations in grain size distribution: PSD grains dominate in a thin bottommost zone, and from base to top from PSD-MD to PSD-SD grains are found. The vertical variation of AMS principal direction patterns permitted identification of two to three main lava zones, some subdivided into subzones. The lower zone is very similar in all profiles with the magnetic foliation dipping toward the flow source, whereas the upper zone has magnetic foliation dipping toward the flow direction or alternates between dipping against and toward the flow direction. The K1 (maximum AMS axis) directions tend to be mostly parallel to the flow direction in both zones. The middle zone shows AMS axes diverging among profiles. We present heterogeneous strain ellipse distribution models for different flow velocities assuming similar viscosity to explain the AMS directions and related parameters of each zone. Irregular vertical foliations and transverse to flow lineation of a few samples at the bottommost and topmost part of profiles suggest SD inverse fabric, levels of intense friction, or degassing effects in AMS orientations.

  10. Very long pahoehoe inflated basaltic lava flows in the Payenia volcanic province (Mendoza and la Pampa, Argentina

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    Giorgio Pasquarè


    Full Text Available Extremely long basaltic lava flows are here presented and described. The flows originated from the great, polygenetic, fissural Payen Volcanic Complex, in the Andean back-arc volcanic province of Payenia in Argentina. The lava flows outpoured during the Late Quaternary from the summit rift of a shield volcano representing the first volcanic centre of this complex. One of these flows presents an individual tongue-like shape with a length of 181 km and therefore is the longest known individual Quaternary lava flow on Earth. Leaving the flanks of the volcano this flow reached the Salado river valley at La Pampa and, in its distal portion, maintained its narrow and straight shape without any topographic control over a flat alluvial plain. It has a hawaiite composition with low phenocryst content of prevailing olivine and minor plagioclase. Rare Earth element patterns are typical of Na-alkaline basalts, but incompatible trace element patterns and Sr -Nd isotope ratios, suggest a geodynamic setting transitional to the orogenic one. The flow advanced following the thermally efficient "inflation" mechanism, as demonstrated by a peculiar association of well developed morphological, structural and textural features. The temperature of 1130-1160°C and the viscosity of 3-73 Pa*s, calculated by petrochemical data, may be considered, together with a very low cooling rate and a sustained and long lasting effusion rate, the main causes of the extremely long transport system of this flow. Both the extreme length of the flow and the partial lack of topographic control may provide new constraints on the physics of large inflated flows, which constitute the largest volcanic provinces on Earth and probably also on the terrestrial planets.

  11. A brief comparison of lava flows from the Deccan Volcanic Province and the Columbia-Oregon Plateau Flood Basalts: Implications for models of flood basalt emplacement

    Indian Academy of Sciences (India)

    Ninad Bondre; Raymond A Duraiswami; Gauri Dole


    The nature and style of emplacement of Continental Flood Basalt (CFB) lava flows has been a atter of great interest as well as considerable controversy in the recent past. 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. In this paper, we first present a short overview of important studies pertaining to the emplacement of flood basalt flows. We then briefly review the morphology of lava flows from the Deccan Volcanic Province (DVP) and the Columbia-Oregon Plateau flood basalts. The review underscores the existence of significant variations in lava flow morphology between different provinces, and even within the same province. It is quite likely that there were more than one way of emplacing the voluminous and extensive CFB lava flows. We argue that the establishment of general models of emplacement must be based on a comprehensive documentation of lava flow morphology from all CFB provinces.

  12. The morphology and evolution of the Stromboli 2002-2003 lava flow field--An example of a basaltic flow field emplaced on a steep slope (United States)

    Lodato, Luigi; Harris, A.; Spampinato, L.; Calvari, Sonia; Dehn, J.; Patrick, M.


    The use of a hand-held thermal camera during the 2002–2003 Stromboli effusive eruption proved essential in tracking the development of flow field structures and in measuring related eruption parameters, such as the number of active vents and flow lengths. The steep underlying slope on which the flow field was emplaced resulted in a characteristic flow field morphology. This comprised a proximal shield, where flow stacking and inflation caused piling up of lava on the relatively flat ground of the vent zone, that fed a medial–distal lava flow field. This zone was characterized by the formation of lava tubes and tumuli forming a complex network of tumuli and flows linked by tubes. Most of the flow field was emplaced on extremely steep slopes and this had two effects. It caused flows to slide, as well as flow, and flow fronts to fail frequently, persistent flow front crumbling resulted in the production of an extensive debris field. Channel-fed flows were also characterized by development of excavated debris levees in this zone (Calvari et al. 2005). Collapse of lava flow fronts and inflation of the upper proximal lava shield made volume calculation very difficult. Comparison of the final field volume with that expecta by integrating the lava effusion rates through time suggests a loss of ~70% erupted lava by flow front crumbling and accumulation as debris flows below sea level. Derived relationships between effusion rate, flow length, and number of active vents showed systematic and correlated variations with time where spreading of volume between numerous flows caused an otherwise good correlation between effusion rate, flow length to break down. Observations collected during this eruption are useful in helping to understand lava flow processes on steep slopes, as well as in interpreting old lava–debris sequences found in other steep-sided volcanoes subject to effusive activity.

  13. Characterizing Lava Flows With LiDAR (United States)

    Deligne, N. I.; Cashman, K. V.; Deardorff, N.; Dietterich, H. R.; House, P. K.; Soule, S.


    Digital elevation models (DEMs) have been used in volcanology in predictive modeling of lava flow paths, both for assessment of potential hazards and specific predictions of lava flow paths. Topographic analysis of a lava flow is potentially useful for mapping and quantifying flow surface morphologies, which in turn can be used to determine flow emplacement conditions, such as effusion rate, steadiness of flow, and interactions with pre-existing topography and surface water. However, this has been limited in application because of the coarse resolution of most DEMs. In recent years, use of Light Detection and Ranging (LiDAR) airborne laser altimetry, capable of producing high resolution (≤ 1 meter) DEMs, has become increasingly common in the geomorphic and mapping community. However, volcanologists have made little use of airborne LiDAR. Here we compare information obtained using field observations and standard (10 meter) DEMs against LiDAR high resolution DEMs to assess the usefulness, capabilities, and limitations of LiDAR as applicable to lava flows. We compare morphologic characteristics of five lava flows of different compositions, tectonic settings, flow extents, slopes, and eruption duration: (1) 1984 Mauna Loa lava flow, Hawaii; (2) December 1974 Kilauea lava flow, Hawaii; (3) c. 1600 ybp Collier Cone lava flow, central Oregon Cascades; (4) Holocene lava flows from the Sand Mountain volcanic chain, central Oregon Cascades; and (5) Pleistocene lava flows along the Owyhee River, eastern Oregon basin and range. These lava flows range in composition from basalt to andesite, and have eruption durations ranging from 6 hours (observed) to years (inferred). We measure channel width, levee and flow front heights, compression ridge amplitude, wavelength and tumuli dimensions, and surface roughness. For all but the smallest scale features, LiDAR is easily used to quantify these features, which often is impossible or technically challenging to do in the field, while

  14. Martian Lava Flows (United States)


    19 October 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows lava flows at the southeast base of the giant volcano, Olympus Mons. The flat plain in the south-southeast (bottom/lower right) portion of the image is younger than and cuts off the ends of many of the lava flows that came from the northwest (upper left). Many of the lava flows in this image exhibit channels with levees bounding their margins. As each lava flow was advancing, its outer margins cooled and hardened, forming a channel or tube through which the molten rock continued to advance. Location near: 17.2oN, 129.0oW Image width: width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Winter

  15. Metamorphic gradients in burial metamorphosed vesicular lavas: Comparison of basalt and spilite in Cretaceous basic flows from central Chile (United States)

    Levi, Beatriz; Aguirre, Luis; Nyström, Jan Olov


    Partial spilitization of a 9 km thick pile of flood basalts with highly vesicular flow tops gave rise to patterns of secondary mineralogy at different scales: (a) a local pattern of mineralogical variation from the almost unaltered bottom towards the altered top of each flow, and (b) an overall pattern, comparing flow tops throughout the pile, with changes in mineralogical composition within a sequence of metamorphic zones and facies. The local patterns mimic the trend of the overall pattern, but are of opposite direction and telescoped. Thus, a gradual ordering and Andepletion of the secondary “albite” and increases in the Fe*/Al ratio of epidote and pumpellyite upwards within individual flows are comparable in range to corresponding overall changes downwards throughout several kilometres. The mineralogical changes within the flows diminish in range towards the more altered deeper part of the pile. The local and overall patterns cannot be interpreted in terms of grade. They represent trends from metastable towards stable equilibrium, this latter only approached in the flow tops of the lower part of the pile. The patterns of secondary mineralogy were formed by an interplay of metamorphic gradients at different scales at any given time, and as burial proceeded. The overall pattern was caused by depth-controlled gradients: increasing P fluid, temperature and temperature-induced increase of reaction rates, and decreasing fO2 (downwards in the pile). The local patterns resulted from permeability-controlled gradients: increasing reaction rates, fO2 and contrast in chemical activity between different domains, and decreasing P fluid (upwards in each flow). The mineralogical observations reported in this paper fall into line if the overall temperature-induced increase of reaction rates and the local permeability-controlled rate factors played the leading role during burial metamorphism of the pile.

  16. Basalt: Biologic Analog Science Associated with Lava Terrains (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.


    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

  17. Very long pahoehoe inflated basaltic lava flows in the Payenia volcanic province (Mendoza and la Pampa, Argentina Flujos de lava basáltica pahoehoe muy extendidos en la provincia volcánica Payenia (Mendoza y La Pampa, Argentina

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    Giorgio Pasquarè


    Full Text Available Extremely long basaltic lava flows are here presented and described. The flows originated from the great, polygenetic, fissural Payen Volcanic Complex, in the Andean back-arc volcanic province of Payenia in Argentina. The lava flows outpoured during the Late Quaternary from the summit rift of a shield volcano representing the first volcanic centre of this complex. One of these flows presents an individual tongue-like shape with a length of 181 km and therefore is the longest known individual Quaternary lava flow on Earth. Leaving the flanks of the volcano this flow reached the Salado river valley at La Pampa and, in its distal portion, maintained its narrow and straight shape without any topographic control over a flat alluvial plain. It has a hawaiite composition with low phenocryst content of prevailing olivine and minor plagioclase. Rare Earth element patterns are typical of Na-alkaline basalts, but incompatible trace element patterns and Sr -Nd isotope ratios, suggest a geodynamic setting transitional to the orogenic one. The flow advanced following the thermally efficient "inflation" mechanism, as demonstrated by a peculiar association of well developed morphological, structural and textural features. The temperature of 1130-1160°C and the viscosity of 3-73 Pa*s, calculated by petrochemical data, may be considered, together with a very low cooling rate and a sustained and long lasting effusion rate, the main causes of the extremely long transport system of this flow. Both the extreme length of the flow and the partial lack of topographic control may provide new constraints on the physics of large inflated flows, which constitute the largest volcanic provinces on Earth and probably also on the terrestrial planets.En este trabajo se presentan y describen flujos de lava extremadamente largos. Estos flujos se originaron en el complejo volcánico fisural Payen, dentro de la provincia volcánica Payenia en el retroarco andino. Los flujos de lava

  18. Lava tubes from the Paraná-Etendeka Continental Flood Basalt Province: Morphology and importance to emplacement models (United States)

    Waichel, Breno L.; Tratz, Eliza B.; Pietrobelli, Gisele; Jerram, Dougal A.; Calixto, Geovane R.; Bacha, Rafael R.; Tomazzolli, Edison R.; da Silva, Wellington B.


    Lava tubes are a common feature in active volcanic areas around the world. They are related to pahoehoe and 'a'ā lava flow fields, that are predominantly basaltic, and form as the most efficient mechanism to transport lava in insulated fedder pathways. Continental Flood Basalt Provinces (CFBs) are thick volcanic sequences of predominantly basaltic lava flows and flow fields, which cover huge areas and are often related to continental breakup. The proposed emplacement model for CFB's is synonymous with the inflation processes observed in modern active flows. Although pahoehoe and 'a'ā lava flows are recognized in CFB's provinces, good examples of lava tubes, pipes or tube systems are rarely reported. Lava feeder systems (tube/pipes) are a common feature of modern pahoehoe flow systems so it would be expected to find good examples in CFB's provinces formed by the same emplacement processes. Here we describe the morphology of two lava tube systems discovered in the Paraná CFB Province in Southern Brazil. Comparisons are made with active systems and the importance of CFB lava tube systems, and their recognition in the rock record, are discussed in the context of the current emplacement model.

  19. Primary oxidation variation and distribution of uranium and thorium in a lava flow. (United States)

    Watkins, N D; Holmes, C W; Haggerty, S E


    An Icelandic basalt lava flow has a systematic oxidation variation, formed during the initial cooling, with a resultant maximum oxidation just below the center of the lava. The ratio of thorium to uranium shows a clear dependence on this primary oxidation variation. Between-lava comparisons of thorium and uranium may be critically dependent on the position of the samples in each lava.

  20. Paleomagnetism of Basaltic Lava Flows in Coreholes ICPP 213, ICPP-214, ICPP-215, and USGS 128 Near the Vadose Zone Research Park, Idaho Nuclear Technology and Engineering Center, Idaho National Engineering and Environmental Laboratory, Idaho (United States)

    Champion, Duane E.; Herman, Theodore C.


    A paleomagnetic study was conducted on basalt from 41 lava flows represented in about 2,300 ft of core from coreholes ICPP-213, ICPP-214, ICPP-215, and USGS 128. These wells are in the area of the Idaho Nuclear Technology and Engineering Center (INTEC) Vadose Zone Research Park within the Idaho National Engineering and Environmental Laboratory (INEEL). Paleomagnetic measurements were made on 508 samples from the four coreholes, which are compared to each other, and to surface outcrop paleomagnetic data. In general, subhorizontal lines of correlation exist between sediment layers and between basalt layers in the area of the new percolation ponds. Some of the basalt flows and flow sequences are strongly correlative at different depth intervals and represent important stratigraphic unifying elements. Some units pinch out, or thicken or thin even over short separation distances of about 1,500 ft. A more distant correlation of more than 1 mile to corehole USGS 128 is possible for several of the basalt flows, but at greater depth. This is probably due to the broad subsidence of the eastern Snake River Plain centered along its topographic axis located to the south of INEEL. This study shows this most clearly in the oldest portions of the cored sections that have differentially subsided the greatest amount.

  1. Tachylyte in Cenozoic basaltic lavas from the Czech Republic and Iceland: contrasting compositional trends (United States)

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


    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.

  2. Newberry Volcano's youngest lava flows (United States)

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


    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.

  3. Heat transfer measurements of the 1983 kilauea lava flow. (United States)

    Hardee, H C


    Convective heat flow measurements of a basaltic lava flow were made during the 1983 eruption of Kilauea volcano in Hawaii. Eight field measurements of induced natural convection were made, giving heat flux values that ranged from 1.78 to 8.09 kilowatts per square meter at lava temperatures of 1088 and 1128 degrees Celsius, respectively. These field measurements of convective heat flux at subliquidus temperatures agree with previous laboratory measurements in furnace-melted samples of molten lava, and are useful for predicting heat transfer in magma bodies and for estimating heat extraction rates for magma energy.

  4. The Payun-Matru lava field: a source of analogues for Martian long lava flows (United States)

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


    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

  5. A flexible open-source toolkit for lava flow simulations (United States)

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


    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

  6. Lava Flow at Kilauea, Hawaii (United States)


    On July 21, 2007, the world's most active volcano, Kilauea on Hawaii's Big Island, produced a new fissure eruption from the Pu'u O'o vent, which fed an open lava channel and lava flows toward the east. Access to the Kahauale'a Natural Area Reserve was closed due to fire and gas hazards. The two Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) nighttime thermal infrared images were acquired on August 21 and August 30, 2007. The brightest areas are the hottest lava flows from the recent fissure eruption. The large lava field extending down to the ocean is part of the Kupaianaha field. The most recent activity there ceased on June 20, but the lava is still hot and appears bright on the images. Magenta areas are cold lava flows from eruptions that occurred between 1969 and 2006. Clouds are cold (black) and the ocean is a uniform warm temperature, and light gray in color. These images are being used by volcanologists at the U.S. Geological Survey Hawaii Volcano Observatory to help monitor the progress of the lava flows. With its 14 spectral bands from the visible to the thermal infrared wavelength region, and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), ASTER images Earth to map and monitor the changing surface of our planet. ASTER is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra spacecraft. The instrument was built by Japan's Ministry of Economy, Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. The broad spectral coverage and high spectral resolution of ASTER provides scientists in numerous disciplines with critical information for surface mapping, and monitoring of dynamic conditions and temporal change. Example applications are: monitoring glacial advances and retreats; monitoring potentially active volcanoes; identifying crop stress; determining cloud morphology and physical properties

  7. Zeolites in Eocene basaltic pillow lavas of the Siletz River Volcanics, Central Coast Range, Oregon. (United States)

    Keith, T.E.C.; Staples, L.W.


    Zeolites and associated minerals occur in a tholeiitic basaltic pillow lava sequence. Although the zeolite assemblages are similar to those found in other major zeolite occurrences in basaltic pillow lavas, regional zoning of the zeolite assemblages is not apparent. The formation of the different assemblages is discussed.-D.F.B.

  8. Windstreak on Lava Flow (United States)


    [figure removed for brevity, see original site] Today's image of the flows west of Arsia Mons also contains a large windstreak. Note the the surface texture in the 'white' part of the windstreak is more subdued than the rest of the flow. This is because the wind has deposited fine materials in this area. The wind can both erode the surface and cover it with deposits. Image information: VIS instrument. Latitude -7.7, Longitude 227.5 East (132.5 West). 17 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  9. Paleomagnetic correlation of surface and subsurface basaltic lava flows and flow groups in the southern part of the Idaho National Laboratory, Idaho, with paleomagnetic data tables for drill cores (United States)

    Champion, Duane E.; Hodges, Mary K.V.; Davis, Linda C.; Lanphere, Marvin A.


    Paleomagnetic inclination and polarity studies have been conducted on thousands of subcore samples from 51 coreholes located at and near the Idaho National Laboratory. These studies are used to paleomagnetically characterize and correlate successive stratigraphic intervals in each corehole to similar depth intervals in adjacent coreholes. Paleomagnetic results from 83 surface paleomagnetic sites, within and near the INL, are used to correlate these buried lava flow groups to basaltic shield volcanoes still exposed on the surface of the eastern Snake River Plain. Sample handling and demagnetization protocols are described as well as the paleomagnetic data averaging process. Paleomagnetic inclination comparisons between coreholes located only kilometers apart show comparable stratigraphic successions of mean inclination values over tens of meters of depth. At greater distance between coreholes, comparable correlation of mean inclination values is less consistent because flow groups may be missing or additional flow groups may be present and found at different depth intervals. Two shallow intersecting cross-sections, A-A- and B-B- (oriented southwest-northeast and northwest-southeast, respectively), drawn through southwest Idaho National Laboratory coreholes show the corehole to corehole or surface to corehole correlations derived from the paleomagnetic inclination data. From stratigraphic top to bottom, key results included the (1) Quaking Aspen Butte flow group, which erupted from Quaking Aspen Butte southwest of the Idaho National Laboratory, flowed northeast, and has been found in the subsurface in corehole USGS 132; (2) Vent 5206 flow group, which erupted near the southwestern border of the Idaho National Laboratory, flowed north and east, and has been found in the subsurface in coreholes USGS 132, USGS 129, USGS 131, USGS 127, USGS 130, USGS 128, and STF-AQ-01; and (3) Mid Butte flow group, which erupted north of U.S. Highway 20, flowed northwest, and has been

  10. Episodic soil succession on basaltic lava fields in a cool, dry environment (United States)

    Vaughan, K.L.; McDaniel, P.A.; Phillips, W.M.


    Holocene- to late Pleistocene-aged lava flows at Craters of the Moon National Monument and Preserve provide an ideal setting to examine the early stages of soil formation under cool, dry conditions. Transects were used to characterize the amount and nature of soil cover on across basaltic lava flows ranging in age from 2.1 to 18.4 ka. Results indicate that on flows soils (Folists in Soil Taxonomy) are the dominant soil type, providing an areal coverage of up to ∼25%. On flows ≥13.9 ka, deeper mineral soils including Entisols, Aridisols, and Mollisols become dominant and the areal extent increases to ≥95% on flows older than 18.4 ka. These data suggest there are two distinct pedogenic pathways associated with lava flows of the region. The first pathway is illustrated by the younger flows, where Folists dominate. In the absence of a major source of loess, relatively little mineral material accumulates and soils provide only minor coverage of the lava flows. Our results indicate that this pathway of soil development has not changed appreciably over the past ∼10 ka. The second pedogenic pathway is illustrated by the flows older than 13.9 ka. These flows have been subject to deposition of large quantities of loess during and after the last regional glaciation, resulting in almost complete coverage. Subsequent pedogenesis has given rise to Aridisols and Mollisols with calcic and cambic horizons and mollic epipedons. This research highlights the importance of regional climate change on the evolution of Craters of the Moon soilscapes.

  11. Tube coalescence in the Jingfudong lava tube and implications for lava flow hazard of Tengchong volcanism


    Zhengquan Chen; Yongshun Liu; Haiquan Wei; Jiandong Xu; Wenfeng Guo


    Tube-fed structure occurs as a general phenomenon in Tengchong basic lavas, such as lava tubes, lava plugs and tube-related collapse depressions. We deduced the development of Laoguipo lava flows, which is the longest lava tube (Jingfudong lava tube) evolved in Tengchong volcanic area. Following the detailed documentation of the tube morphology of the Jingfudong lava tube, we propose that the Jingfudong lava tube was formed through vertical coalescence of at least three tubes. The coalescence...

  12. Taylor instability in rhyolite lava flows (United States)

    Baum, B. A.; Krantz, W. B.; Fink, J. H.; Dickinson, R. E.


    A refined Taylor instability model is developed to describe the surface morphology of rhyolite lava flows. The effect of the downslope flow of the lava on the structures resulting from the Taylor instability mechanism is considered. Squire's (1933) transformation is developed for this flow in order to extend the results to three-dimensional modes. This permits assessing why ridges thought to arise from the Taylor instability mechanism are preferentially oriented transverse to the direction of lava flow. Measured diapir and ridge spacings for the Little and Big Glass Mountain rhyolite flows in northern California are used in conjunction with the model in order to explore the implications of the Taylor instability for flow emplacement. The model suggests additional lava flow features that can be measured in order to test whether the Taylor instability mechanism has influenced the flows surface morphology.

  13. The cervantes lava flow geomorfology, irazú volcano (costa rica): description of the central america`s greater lava flow field


    Guillermo E. Alvarado; Vega, Ana E.


    The Cervantes lava flow field, on the southeastern flank of Irazú volcano, is the most recent and large effusive event dated at this volcano. The Cervantes lava flow actually consists of two different bi-modal lava flow fields. The Western composite lava field (10.85 km2, 0.18 ± 0.1 km3) has a basaltic (SiO2: 50.71-52.06%; MgO: 8.13- 9.50%) and basaltic andesite composition due to magma mixing (SiO2: 52.90-53.42%; MgO: 6.71-7.12%) and is older in age (57 ka ± 13 ka years B.P.). The Eastern co...

  14. Tephra on Lava Flows Promotes Vegetation Development: Case Studies From Recent Holocene Lava Flows (United States)

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


    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.

  15. Evoluton of polygonal fracture patterns in lava flows. (United States)

    Aydin, A; Degraff, J M


    Cooling-induced fractures, also known as columnar joints, divide basaltic lava flows into prismatic columns with polygonal cross sections. The regularity and symmetry of the fracture patterns have long fascinated naturalists. In view of the recent selection of two candidate nuclear waste sites in areas where polygonally fractured volcanic rocks are located, a better understanding of the fracture patterns is required. Field data indicate that the tetragonal networks at flow surfaces evolve systematically to hexagonal networks as the joints grow inward during solidification of lava. This evolution occurs by the gradual change of most orthogonal intersections to nonorthogonal intersections of about 120 degrees. The surface features and intersection geometries of columnar joints show that joint segments at any given level form sequentially yet harmoniously.

  16. Field and experimental constraints on the rheology of arc basaltic lavas: the January 2014 Eruption of Pacaya (Guatemala) (United States)

    Soldati, A.; Sehlke, A.; Chigna, G.; Whittington, A.


    We estimated the rheology of an active basaltic lava flow in the field, and compared it with experimental measurements carried out in the laboratory. In the field we mapped, sampled, and recorded videos of the 2014 flow on the southern flank of Pacaya, Guatemala. Velocimetry data extracted from videos allowed us to determine that lava traveled at ˜2.8 m/s on the steep ˜45° slope 50 m from the vent, while 550 m further downflow it was moving at only ˜0.3 m/s on a ˜4° slope. Estimates of effective viscosity based on Jeffreys' equation increased from ˜7600 Pa s near the vent to ˜28,000 Pa s downflow. In the laboratory, we measured the viscosity of a representative lava composition using a concentric cylinder viscometer, at five different temperatures between 1234 and 1199 °C, with crystallinity increasing from 0.1 to 40 vol%. The rheological data were best fit by power law equations, with the flow index decreasing as crystal fraction increased, and no detectable yield strength. Although field-based estimates are based on lava characterized by a lower temperature, higher crystal and bubble fraction, and with a more complex petrographic texture, field estimates and laboratory measurements are mutually consistent and both indicate shear-thinning behavior. The complementary field and laboratory data sets allowed us to isolate the effects of different factors in determining the rheological evolution of the 2014 Pacaya flows. We assess the contributions of cooling, crystallization, and changing ground slope to the 3.7-fold increase in effective viscosity observed in the field over 550 m, and conclude that decreasing slope is the single most important factor over that distance. It follows that the complex relations between slope, flow velocity, and non-Newtonian lava rheology need to be incorporated into models of lava flow emplacement.

  17. New Insights to the Mid Miocene Calc-alkaline Lavas of the Strawberry Volcanics, NE Oregon Surrounded by the Coeval Tholeiitic Columbia River Basalt Province (United States)

    Steiner, A. R.; Streck, M. J.


    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

  18. Lava flow hazard at Fogo Volcano, Cabo Verde, before and after the 2014-2015 eruption (United States)

    Richter, Nicole; Favalli, Massimiliano; de Zeeuw-van Dalfsen, Elske; Fornaciai, Alessandro; da Silva Fernandes, Rui Manuel; Pérez, Nemesio M.; Levy, Judith; Silva Victória, Sónia; Walter, Thomas R.


    observations will be important for the next eruption of Fogo Volcano and have implications for future lava flow crises and disaster response efforts at basaltic volcanoes elsewhere in the world.

  19. Mineral chemistry of Pangidi basalt flows from Andhra Pradesh

    Indian Academy of Sciences (India)

    P V Nageswara Rao; P C Swaroop; Syed Karimulla


    This paper elucidates the compositional studies on clinopyroxene, plagioclase, titaniferous magnetite and ilmenite of basalts of Pangidi area to understand the geothermometry and oxybarometry conditions. Petrographic evidence and anorthite content (up to 85%) of plagioclase and temperature estimates of clinopyroxene indicate that the clinopyroxene is crystallized later than or together with plagioclase. The higher An content indicates that the parent magma is tholeiitic composition. The equilibration temperatures of clinopyroxene (1110–1190°C) and titaniferous magnetite and ilmenite coexisting mineral phases (1063–1103°C) are almost similar in lower basalt flow and it is higher for clinopyroxene (900–1110°C) when compared to titaniferous magnetite and ilmenite coexisting mineral phases (748–898°C) in middle and upper basalt flows. From this it can be inferred that the clinopyroxene is crystallized earlier than Fe–Ti oxide phases reequilibration, which indicates that the clinopyroxene temperature is the approximate eruption temperature of the present lava flows. The wide range of temperatures (900–1190°C) attained by clinopyroxene may point out that the equilibration of clinopyroxene crystals initiated from depth till closer to the surface before the melt erupted. Pangidi basalts follow the QFM buffer curve which indicates the more evolved tholeiitic composition. This suggests the parent tholeiitic magma suffered limited fractionation at high temperature under increasing oxygen fugacity in lower basalt flow and more fractionation at medium to lower temperatures under decreasing oxygen fugacity conditions during cooling of middle and upper basalt flows. The variation of oxygen fugacity indicates the oxidizing conditions for lower basalt flow (9.48–10.3) and extremely reducing conditions for middle (12.1–15.5) and upper basalt (12.4–15.54) flows prevailed at the time of cooling. Temperature vs. (FeO+Fe2O3)/(FeO+Fe2O3+MgO) data plots for present

  20. Studies of fluid instabilities in flows of lava and debris (United States)

    Fink, Jonathan H.


    At least two instabilities have been identified and utilized in lava flow studies: surface folding and gravity instability. Both lead to the development of regularly spaced structures on the surfaces of lava flows. The geometry of surface folds have been used to estimate the rheology of lava flows on other planets. One investigation's analysis assumed that lava flows have a temperature-dependent Newtonian rheology, and that the lava's viscosity decreased exponentially inward from the upper surface. The author reviews studies by other investigators on the analysis of surface folding, the analysis of Taylor instability in lava flows, and the effect of surface folding on debris flows.

  1. Voluminous submarine lava flows from Hawaiian volcanoes

    Energy Technology Data Exchange (ETDEWEB)

    Holcomb, R.T.; Moore, J.G.; Lipman, P.W.; Belderson, R.H.


    The GLORIA long-range sonar imaging system has revealed fields of large lava flows in the Hawaiian Trough east and south of Hawaii in water as deep as 5.5 km. Flows in the most extensive field (110 km long) have erupted from the deep submarine segment of Kilauea's east rift zone. Other flows have been erupted from Loihi and Mauna Loa. This discovery confirms a suspicion, long held from subaerial studies, that voluminous submarine flows are erupted from Hawaiian volcanoes, and it supports an inference that summit calderas repeatedly collapse and fill at intervals of centuries to millenia owing to voluminous eruptions. These extensive flows differ greatly in form from pillow lavas found previously along shallower segments of the rift zones; therefore, revision of concepts of volcano stratigraphy and structure may be required.

  2. Contamination of basaltic lava by seawater: Evidence found in a lava pillar from Axial Seamount, Juan de Fuca Ridge (United States)

    Schiffman, Peter; Zierenberg, Robert; Chadwick, William W.; Clague, David A.; Lowenstern, Jacob


    A lava pillar formed during the 1998 eruption at Axial Seamount exhibits compositional and textural evidence for contamination by seawater under magmatic conditions. Glass immediately adjacent to anastomosing microfractures within 1 cm of the inner pillar wall is oxidized and significantly enriched in Na and Cl and depleted in Fe and K with respect to that in glassy selvages from the unaffected outer pillar wall. The affected glass contains up to 1 wt % Cl and is enriched by ˜2 wt % Na2O relative to unaffected glass, consistent with a nearly 1:1 (molar) incorporation of NaCl. Glass bordering the Cl-enriched glass in the inner pillar wall is depleted in Na but enriched in K. The presence of tiny (<10 μm) grains of Cu-Fe sulfides and Fe sulfides as well as elemental Ni, Ag, and Au in the Na-depleted, K-enriched glass of the inner pillar wall implies significant reduction of this glass, presumably by hydrogen generated during seawater contamination and oxidation of lava adjacent to microfractures. We interpret the compositional anomalies we see in the glass of the interior pillar wall as caused by rapid incorporation of seawater into the still-molten lava during pillar growth, probably on the time scale of seconds to minutes. Only one of seven examined lava pillars shows this effect, and we interpret that seawater has to be trapped in contact with molten lava (inside the lava pillar, in this case) to produce the effects we see. Thus, under the right conditions, seawater contamination of lavas during submarine eruptions is one means by which the oceanic crust can sequester Cl during its global flux cycle. However, since very few recent lava flows have been examined in similar detail, the global significance of this process in effecting Earth's Cl budget remains uncertain.

  3. Owyhee River intracanyon lava flows: does the river give a dam? (United States)

    Ely, Lisa L.; Brossy, Cooper C.; House, P. Kyle; Safran, Elizabeth B.; O'Connor, Jim E.; Champion, Duane E.; Fenton, Cassandra R.; Bondre, Ninad R.; Orem, Caitlin A.; Grant, Gordon E.; Henry, Christopher D.; Turrin, Brent D.


    Rivers carved into uplifted plateaus are commonly disrupted by discrete events from the surrounding landscape, such as lava flows or large mass movements. These disruptions are independent of slope, basin area, or channel discharge, and can dominate aspects of valley morphology and channel behavior for many kilometers. We document and assess the effects of one type of disruptive event, lava dams, on river valley morphology and incision rates at a variety of time scales, using examples from the Owyhee River in southeastern Oregon. Six sets of basaltic lava flows entered and dammed the river canyon during two periods in the late Cenozoic ca. 2 Ma–780 ka and 250–70 ka. The dams are strongly asymmetric, with steep, blunt escarpments facing up valley and long, low slopes down valley. None of the dams shows evidence of catastrophic failure; all blocked the river and diverted water over or around the dam crest. The net effect of the dams was therefore to inhibit rather than promote incision. Once incision resumed, most of the intracanyon flows were incised relatively rapidly and therefore did not exert a lasting impact on the river valley profile over time scales >106 yr. The net long-term incision rate from the time of the oldest documented lava dam, the Bogus Rim lava dam (≤1.7 Ma), to present was 0.18 mm/yr, but incision rates through or around individual lava dams were up to an order of magnitude greater. At least three lava dams (Bogus Rim, Saddle Butte, and West Crater) show evidence that incision initiated only after the impounded lakes filled completely with sediment and there was gravel transport across the dams. The most recent lava dam, formed by the West Crater lava flow around 70 ka, persisted for at least 25 k.y. before incision began, and the dam was largely removed within another 35 k.y. The time scale over which the lava dams inhibit incision is therefore directly affected by both the volume of lava forming the dam and the time required for sediment

  4. Benchmarking Computational Fluid Dynamics Models for Application to Lava Flow Simulations and Hazard Assessment (United States)

    Dietterich, H. R.; Lev, E.; Chen, J.; Cashman, K. V.; Honor, C.


    Recent eruptions in Hawai'i, Iceland, and Cape Verde highlight the need for improved lava flow models for forecasting and hazard assessment. Existing models used for lava flow simulation range in assumptions, complexity, and the degree to which they have been validated against analytical solutions, experiments, and natural observations. In order to assess the capabilities of existing models and test the development of new codes, we conduct a benchmarking study of computational fluid dynamics models for lava flows, including VolcFlow, OpenFOAM, Flow3D, and COMSOL. Using new benchmark scenarios defined in Cordonnier et al. (2015) as a guide, we model Newtonian, Herschel-Bulkley and cooling flows over inclined planes, obstacles, and digital elevation models with a wide range of source conditions. Results are compared to analytical theory, analogue and molten basalt experiments, and measurements from natural lava flows. Our study highlights the strengths and weakness of each code, including accuracy and computational costs, and provides insights regarding code selection. We apply the best-fit codes to simulate the lava flows in Harrat Rahat, a predominately mafic volcanic field in Saudi Arabia. Input parameters are assembled from rheology and volume measurements of past flows using geochemistry, crystallinity, and present-day lidar and photogrammetric digital elevation models. With these data, we use our verified models to reconstruct historic and prehistoric events, in order to assess the hazards posed by lava flows for Harrat Rahat.

  5. Modeling steam pressure under martian lava flows (United States)

    Dundas, Colin M.; Keszthelyi, Laszlo P.


    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.

  6. Physical volcanology of a voluminous rhyolite lava flow: The Badlands lava, Owyhee Plateau, southwestern Idaho (United States)

    Manley, Curtis R.


    This paper describes an extraordinarily well preserved example of a large, high-SiO 2 rhyolite unit that by its exposed physical features can be demonstrated to be an effusive lava flow, not a rheomorphic ignimbrite. The Badlands lava flow of southwestern Idaho shows a multi-lobate form, with flow lobes that advanced along several azimuths from a long fissure vent. The lava flowed around one of its tephra ridges and a bedrock topographic high, creating a kipuka in the middle of the flow; the other tephra ridge was shoved aside by the lava. The lava itself is everywhere flow foliated, with foliation horizontal at the base, steepening toward the top, and convex in the direction of flow advance. The foliation parallels the margins of the flow lobes and reveals the position and orientation of the vent. Many samples of the lava flow's dense upper vitrophyre show one or more fragmental textures that formed by the settling of pumiceous and glassy debris into open fractures and the debris' subsequent welding into a rock that in many respects resembles welded tuff. By this process, the lava flow mimics an ignimbrite at the scale of an outcrop or thin section. Identical textures in other units have been cited as indicative of ash-flow emplacement mechanisms. The Badlands eruption tapped a stratified magma chamber, in which a large volume of phenocryst-rich (30 vol.%) magma underlay a small volume of magma more evolved and nearly aphyric. The lava flow shows mingling relations between the two magmas, with minor volumes of the aphyric magma occurring as early, small lava lobes and as individual layers in the dominant phenocryst-rich lava. Effusion of the 15 km 3 of rhyolite lava may have continued for as short as 6 or as long as 16 years, with effusion rates comparable to those observed at the Mount St. Helens dome. The Badlands lava had a pre-eruptive volatile content of about 2.75 wt.% H 2O or less, and erupted at approximately 830 °C, much lower than the temperatures of

  7. Regional Similarity of Leveed Lava Flows on the Mars Plains (United States)

    Baloga, Steve M.; Glaze, Lori, S.


    The dynamics of lava flow movement are controlled by the fluid interior. Crust, solids, and nondeformable material can only retard the advance or spreading of a lava flow. Figure 1 shows a typical large, channelized lava flow found on the Mars plains. It has been suggested in [I] that such large leveed flows on the Mars plains were emplaced by a balance between the formation and shedding of crust as the flow advances. For the prototypical flow north of Pavonis Mons (Fig. I), such a balance leads to a flow morphology that approximately self-replicates at all locations along the flow path [2,3]. Moreover, most quantitative characteristics of emplacement (e.g., viscosity, volumetric flow rate) of the prototype flow at Pavonis Mons resembled those of large channelized lava flows on Earth. The exception was the relatively long, sustained supply of lava, on the order of a year as opposed to hours or days for terrestrial analogs.

  8. Late Holocene lava flow morphotypes of northern Harrat Rahat, Kingdom of Saudi Arabia: Implications for the description of continental lava fields (United States)

    Murcia, H.; Németh, K.; Moufti, M. R.; Lindsay, J. M.; El-Masry, N.; Cronin, S. J.; Qaddah, A.; Smith, I. E. M.


    A "lava morphotype" refers to the recognizable and distinctive characteristics of the surface morphology of a lava flow after solidification, used in a similar way to a sedimentary facies. This classification method is explored on an example volcanic field in the Kingdom of Saudi Arabia, where copious lava outpourings may represent an important transition between monogenetic and flood basalt fields. Here, young and well-preserved mafic lava fields display a wide range of surface morphologies. We focussed on four post-4500 yrs. BP lava flow fields in northern Harrat Rahat (morphotypes down-flow. The morphotypes give insight into intrinsic and extrinsic parameters of emplacement, rheology and dominant flow behavior, as well as the occurrence and character of other lava structures. The Harrat Rahat lava flow fields studied extend up to 23 km from the source, and vary between 1-2 m and 12 m in thickness. Areas of the lava flow fields are between ˜32 and ˜61 km2, with individual flow field volumes estimated between ˜0.085 and ˜0.29 km3. They exhibit Shelly-, Slabby-, and Rubbly-pahoehoe, Platy-, Cauliflower-, and Rubbly-a'a, and Blocky morphotypes. Morphotypes reflect the intrinsic parameters of: composition, temperature, crystallinity and volatile-content/vesicularity; along with external influences, such as: emission mechanism, effusion rate, topography and slope control of flow velocity. One morphotype can transition to another in individual flow-units or lobes and they may dominate zones. Not all morphotypes were found in a single lava flow field. Pahoehoe morphotypes are related to the simple mechanical disaggregation of the crust, whereas a'a morphotypes are related to the transitional emergence and subsequent transitional disappearance of clinker. Blocky morphotypes result from fracturing and auto-brecciation. A'a morphotypes (i.e. platy-, cauliflower-, rubbly-a'a) dominate the lava flow field surfaces in northern Harrat Rahat, which suggests that core

  9. In situ thermal characterization of cooling/crystallizing lavas during rheology measurements and implications for lava flow emplacement (United States)

    Kolzenburg, S.; Giordano, D.; Cimarelli, C.; Dingwell, D. B.


    Transport properties of natural silicate melts at super-liquidus temperatures are reasonably well understood. However, migration and transport of silicate melts in the Earth's crust and at its surface generally occur at sub-liquidus temperatures and in settings where the melts undergo crystallization under various cooling and/or decompression conditions. In such dynamic situations the occurrence of processes such as the release of latent heat during phase changes, viscous heating, thermal advection and -inertia, and changing heat capacity, all represent potential influences on the state, and thereby on the physico-chemical behavior of the system. To date, rheological data at sub-liquidus temperatures are scarce and cooling-rate dependent, disequilibrium rheological data are virtually absent. In fact, no in situ thermal characterization of liquid or multiphase mixtures during rheological experiments, under either static or dynamic thermal conditions has been presented to date. Here we describe a new experimental setup for in situ thermal characterization of cooling/crystallizing lavas during viscosity measurement at temperatures up to 1600 °C. We use this device to recover in situ, real-time, observations of the combined rheological and thermal evolution of natural, re-melted lava samples during the transient disequilibrium conditions characteristic of lava flows and shallow crustal magma migration and storage systems in nature. We present the calibration procedure and the method employed to recover the thermal evolution of an experimental sample during flow in varying shear regimes, assess the experimental uncertainty and show the ability of the apparatus to measure the release of latent heat of crystallization during transient rheological experiments. We further report the results from a first experimental study on the rheological and thermal evolution of a basaltic lava undergoing continuous cooling at a series of different cooling rates and discuss the

  10. The generation of a diverse suite of Late Pleistocene and Holocene basalt through dacite lavas from the northern Cascade arc at Mount Baker, Washington (United States)

    Baggerman, Troy David; Debari, S. M.


    Mt. Baker is a dominantly andesitic stratovolcano in the northern Cascade arc. In this study, we show that the andesites are not all derived from similar sources, and that open-system processes were dominant during their petrogenesis. To this end, we discuss petrographic observations, mineral chemistry, and whole rock major and trace element chemistry for three of Mt. Baker's late Pleistocene to Holocene lava flow units. These include the basalt and basaltic andesite of Sulphur Creek (SC) (51.4-55.8 wt% SiO2, Mg# 57-58), the Mg-rich andesite of Glacier Creek (GC) (58.3-58.7 wt% SiO2, Mg# 63-64), and the andesite and dacite of Boulder Glacier (BG) (60.2-64.2 wt% SiO2, Mg# 50-57). Phenocryst populations in all units display varying degrees of reaction and disequilibrium textures along with complicated zoning patterns indicative of open-system processes. All lavas are medium-K and calc-alkaline, but each unit displays distinctive trace element and REE characteristics that do not correlate with the average SiO2 content of the unit. The mafic lavas of SC have relatively elevated REE abundances with the lowest (La/Yb)N (~4.5). The intermediate GC andesites (Mg- and Ni-rich) have the lowest REE abundances and the highest (La/Yb)N (~6.7) with strongly depleted HREE. The more felsic BG lavas have intermediate REE abundances and (La/Yb)N (~6.4). The high-Mg character of the GC andesites can be explained by addition of 4% of a xenocrystic olivine component. However, their depleted REE patterns are similar to other high-Mg andesites reported from Mt. Baker and require a distinct mantle source. The two dominantly andesitic units (GC and BG) are different enough from each other that they could not have been derived from the same parent basalt. Nor could either of them have been derived from the SC basalt by crystal fractionation processes. Crystal fractionation also cannot explain the compositional diversity within each unit. Compositional diversity within the SC unit (basalt to

  11. Constraining Eruptive Conditions From Lava Flow Morphometry: A Case Study With Field Evidence (United States)

    Bowles, Z. R.; Clarke, A.; Greeley, R.


    Volcanism is widely recognized as one of the primary factors affecting the surfaces of solid planets and satellites throughout the solar system. Basaltic lava is thought to be the most common composition based on observed features typical of basaltic eruptions found on Earth. Lava flows are one of the most easily recognizable landforms on planetary surfaces and their features may provide information about eruption dynamics, lava rheology, and potential hazards. More recently, researchers have taken a multi-faceted approach to combine remote sensing, field observations and quantitative modeling to constrain volcanic activity on Earth and other planets. Here we test a number of published models, including empirically derived relationships from Mt. Etna and Kilauea, models derived from laboratory experiments, and theoretical models previously applied to remote sensing of planetary surfaces, against well-documented eruptions from the literature and field observations. We find that the Graetz (Hulme and Felder, 1977, Phil.Trans., 285, 227 - 234) method for estimating effusion rates compares favorably with published eruption data, while, on the other hand, inverting lava flow length prediction models to estimate effusion rates leads to several orders of magnitude in error. The Graetz method also better constrains eruption duration. Simple radial spreading laws predict Hawaiian lava flow lengths quite well, as do using the thickness of the lava flow front and chilled crust. There was no observed difference between results from models thought to be exclusive to aa or pahoehoe flow fields. Interpreting historic conditions should therefore follow simple relationships to observable morphologies no matter the composition or surface texture. We have applied the most robust models to understand the eruptive conditions and lava rheology of the Batamote Mountains near Ajo, AZ, an eroded shield volcano in southern Arizona. We find effusion rates on the order of 100 - 200 cubic

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

    Directory of Open Access Journals (Sweden)

    Heryadi Rachmat


    Full Text Available After 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.

  13. Idunn Mons on Venus: Location and extent of recently active lava flows (United States)

    D'Incecco, Piero; Müller, Nils; Helbert, Jörn; D'Amore, Mario


    From 2006 until 2014 the ESA Venus Express probe observed the atmosphere and surface of the Earth's twin planet. The Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) has provided data that indicate the occurrence of recent volcanic activity on Venus. We selected the eastern flank of Idunn Mons - Imdr Regio's single large volcano - as the study area, since it was identified in VIRTIS data as one of the regions with relatively high values of thermal emissivity at 1 μm wavelength. Using the capabilities of specific techniques developed in the Planetary Emissivity Laboratory group at DLR in Berlin, our study intends to identify location and extent of the sources of such anomalies, thus the lava flows responsible for the relatively high emissivity observed by VIRTIS over the eastern flank of Idunn Mons. We map the lava flow units on the top and eastern flank of Idunn Mons, varying the values of simulated 1 μm emissivity assigned to the mapped units. For each configuration we calculate the total RMS error in comparison with the VIRTIS observations. In the best-fit configuration, the flank lava flows are characterized by high values of 1 μm simulated emissivity. Hence, the lava flow units on the eastern flank on Idunn Mons are likely responsible for the relatively high 1 μm emissivity anomalies observed by VIRTIS. This result is supported by the reconstructed post-eruption stratigraphy, displaying the relative dating of the mapped lava flows, that is independent of the 1 μm emissivity modeling. Values of average microwave emissivity extracted from the lava flow units range around the global mean, which is consistent with dry basalts.

  14. Degassing-induced crystallization of basaltic magma and effects on lava rheology (United States)

    Lipman, P.W.; Banks, N.G.; Rhodes, J.M.


    During the north-east rift eruption of Mauna Loa volcano, Hawaii, on 25 March-14 April 1984 (Fig. 1), microphenocryst contents of erupted lava increased from 0.5 to 30% without concurrent change in either bulk magma composition or eruption temperature (1,140 ?? 3 ??C). The crystallization of the microphenocrysts is interpreted here as being due to undercooling of the magma 20-30 ??C below its liquidas; the undercooling probably resulted from separation and release of volatiles as the magma migrated 12 km from the primary summit reservoir to the eruption site on the north-east rift zone. Such crystallization of magma during an eruption has not been documented previously. The undercooling and crystallization increased the effective viscosity of the magma, leading to decreased eruption rates and stagnation of the lava flow. ?? 1985 Nature Publishing Group.

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


    Eugenio Rustico; Annamaria Vicari; Giuseppe Bilotta; Alexis Hérault; Ciro Del Negro


    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, an...

  16. Stochastic modeling of a lava-flow aquifer system (United States)

    Cronkite-Ratcliff, Collin; Phelps, Geoffrey A.


    This report describes preliminary three-dimensional geostatistical modeling of a lava-flow aquifer system using a multiple-point geostatistical model. The purpose of this study is to provide a proof-of-concept for this modeling approach. An example of the method is demonstrated using a subset of borehole geologic data and aquifer test data from a portion of the Calico Hills Formation, a lava-flow aquifer system that partially underlies Pahute Mesa, Nevada. Groundwater movement in this aquifer system is assumed to be controlled by the spatial distribution of two geologic units—rhyolite lava flows and zeolitized tuffs. The configuration of subsurface lava flows and tuffs is largely unknown because of limited data. The spatial configuration of the lava flows and tuffs is modeled by using a multiple-point geostatistical simulation algorithm that generates a large number of alternative realizations, each honoring the available geologic data and drawn from a geologic conceptual model of the lava-flow aquifer system as represented by a training image. In order to demonstrate how results from the geostatistical model could be analyzed in terms of available hydrologic data, a numerical simulation of part of an aquifer test was applied to the realizations of the geostatistical model.

  17. The Influence of Slope Breaks on Lava Flow Surface Disruption (United States)

    Glaze, Lori S.; Baloga, Stephen M.; Fagents, Sarah A.; Wright, Robert


    Changes in the underlying slope of a lava flow impart a significant fraction of rotational energy beyond the slope break. The eddies, circulation and vortices caused by this rotational energy can disrupt the flow surface, having a significant impact on heat loss and thus the distance the flow can travel. A basic mechanics model is used to compute the rotational energy caused by a slope change. The gain in rotational energy is deposited into an eddy of radius R whose energy is dissipated as it travels downstream. A model of eddy friction with the ambient lava is used to compute the time-rate of energy dissipation. The key parameter of the dissipation rate is shown to be rho R(sup 2/)mu, where ? is the lava density and mu is the viscosity, which can vary by orders of magnitude for different flows. The potential spatial disruption of the lava flow surface is investigated by introducing steady-state models for the main flow beyond the steepening slope break. One model applies to slow-moving flows with both gravity and pressure as the driving forces. The other model applies to fast-moving, low-viscosity, turbulent flows. These models provide the flow velocity that establishes the downstream transport distance of disrupting eddies before they dissipate. The potential influence of slope breaks is discussed in connection with field studies of lava flows from the 1801 Hualalai and 1823 Keaiwa Kilauea, Hawaii, and 2004 Etna eruptions.

  18. Influence of cooling on lava-flow dynamics (United States)

    Stasiuk, Mark V.; Jaupart, Claude; Stephen, R.; Sparks, J.


    Experiments have been carried out to determine the effects of cooling on the flow of fluids with strongly temperature dependent viscosity. Radial viscous-gravity currents of warm glucose syrup were erupted at constant rate into a flat tank filled with a cold aqueous solution. Cold, viscous fluid accumulates at the leading edge, altering the flow shape and thickness and slowing the spreading. The flows attain constant internal temperature distributions and bulk viscosities. The value of the bulk viscosity depends on the Péclet number, which reflects the advective and diffusive heat transport properties of the flow, the flow skin viscosity, which reflects cooling, and the eruption viscosity. Our results explain why most lava flows have bulk viscosities much higher than the lava eruption viscosity. The results can be applied to understanding dynamic lava features such as flow-front thickening, front avalanches, and welded basal breccias.

  19. Modeling Central American Volcanic Front Primitive Lavas with the Arc Basalt Simulator (abs 4.0) (United States)

    Feigenson, M.; Carr, M. J.; Gazel, E.


    We have used the Arc Basalt Simulator (ABS), developed by J-I Kimura, to explore the conditions and components of melting beneath the Central American volcanic front. ABS is a comprehensive forward model that incorporates slab dehydration and melting and mantle wedge fluxing and melting using realistic P-T conditions and experimentally determined phase relations and partition coefficients. We have applied ABS version 4.00, which includes melting/dehydration relations in eight distinct subducting layers, to model representative magma types along the Central American volcanic front. These magmas are first projected to primary melt compositions by the addition of olivine until they reach Fo90. Then, using a wide range of input parameters including variations in slab components, extent of peridotite depletion, depth of slab dehydration and wedge fluxing and degree of peridotite melting, successful model fits are generated (based on trace element and isotope matching). The solution space is probed using a Monte Carlo technique to cover the enormous range of parameter values. Nicaragua and Costa Rica represent geochemical and geophysical end members of the volcanic front, differing greatly in volcano volume, slab dip beneath the volcano, isotopic composition and incompatible element enrichment. Using appropriate input compositions for ABS 4.0, we find through millions of simulations that the Cerro Negro primary magma (Nicaragua) requires high degrees of source melting (22-27%) and large amounts of slab-derived water (3-5%). In contrast, the Irazu primary magma (central Costa Rica) is generated from more enriched sources with only a small amount of water (less than 0.5%) and at low degrees of partial melting (less than 5%). Other Central American lavas with intermediate geochemical characteristics are produced from conditions within the Nicaragua-Costa Rica range. By reproducing the lava geochemistry with ABS 4.0, it becomes possible to extract constraints on source input


    Schaber, Gerald C.; Kozak, R.C.; Burns, Barbara A.; Bartels, K.I.


    The objective of this poster paper is to present a site-specific atlas showing a wide variety of remote sensing data sets collected for the area of S. P. Mountain and lava flow (basaltic-andesite) in north-central Arizona. The data set to be displayed includes a number of radar images, representing three wavelength regions (1-, 3- and 25-cm), multiple incidence angles, look directions, and polarization combinations, in addition to thermal infrared scanner imagery, multispectral scanner imagery, aerial and ground photography, micro- and macro topography, and four-frequency, multipolarization radar scatterometer spectra. The expression of different surface units on the S. P. lava flow are effectively displayed on the ERIM four-channel images by the registration and combination of the four bands. Multi-color imagery of band combinations demonstrate the information content of multi-channel SAR imagery as well as the suitability of extending data manipulation methods developed for Landsat data to SAR data.

  1. Emplacement conditions of the c. 1,600-year bp Collier Cone lava flow, Oregon: a LiDAR investigation (United States)

    Deardorff, Nicholas D.; Cashman, Katharine V.


    A long-standing question in lava flow studies has been how to infer emplacement conditions from information preserved in solidified flows. From a hazards perspective, volumetric flux (effusion rate) is the parameter of most interest for open-channel lava flows, as the effusion rate is important for estimating the final flow length, the rate of flow advance, and the eruption duration. The relationship between effusion rate, flow length, and flow advance rate is fairly well constrained for basaltic lava flows, where there are abundant recent examples for calibration. Less is known about flows of intermediate compositions (basaltic andesite to andesite), which are less frequent and where field measurements are limited by the large block sizes and the topographic relief of the flows. Here, we demonstrate ways in which high-resolution digital topography obtained using Light Detection and Ranging (LiDAR) systems can provide access to terrains where field measurements are difficult or impossible to collect. We map blocky lava flow units using LiDAR-generated bare earth digital terrain models (DTMs) of the Collier Cone lava flow in the central Oregon Cascades. We also develop methods using geographic information systems to extract and quantify morphologic features such as channel width, flow width, flow thickness, and slope. Morphometric data are then analyzed to estimate both effusion rates and emplacement times for the lava flow field. Our data indicate that most of the flow outline (which comprises the earliest, and most voluminous, flow unit) can be well explained by an average volumetric flux ˜14-18 m3/s; channel data suggest an average flux ˜3 m3/s for a later, channel-filling, flow unit. When combined with estimates of flow volume, these data suggest that the Collier Cone lava flow was most likely emplaced over a time scale of several months. This example illustrates ways in which high-resolution DTMs can be used to extract and analyze morphologic measurements and

  2. 40Ar-39Ar age of a lava flow from the Bhimashankar Formation, Giravali Ghat, Deccan Traps

    Indian Academy of Sciences (India)

    Kanchan Pande; S K Pattanayak; K V Subbarao; P Navaneethakrishnan; T R Venkatesan


    We report here a 40Ar-39Ar age of 66.0 ± 0.9Ma (2 ) for a reversely magnetised tholeiitic lava flow from the Bhimashankar Formation (Fm.), Giravali Ghat, western Deccan province, India. This age is consistent with the view that the 1.8–2km thick bottom part of the exposed basalt flow sequence in the Western Ghats was extruded very close to 67.4 Ma.

  3. High-resolution Digital Mapping of Historical Lava Flows as a Test-bed for Lava Flow Models (United States)

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


    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

  4. Numerical modeling of fluid flow with rafts: An application to lava flows (United States)

    Tsepelev, Igor; Ismail-Zadeh, Alik; Melnik, Oleg; Korotkii, Alexander


    Although volcanic lava flows do not significantly affect the life of people, its hazard is not negligible as hot lava kills vegetation, destroys infrastructure, and may trigger a flood due to melting of snow/ice. The lava flow hazard can be reduced if the flow patterns are known, and the complexity of the flow with debris is analyzed to assist in disaster risk mitigation. In this paper we develop three-dimensional numerical models of a gravitational flow of multi-phase fluid with rafts (mimicking rigid lava-crust fragments) on a horizontal and topographic surfaces to explore the dynamics and the interaction of lava flows. We have obtained various flow patterns and spatial distribution of rafts depending on conditions at the surface of fluid spreading, obstacles on the way of a fluid flow, raft landing scenarios, and the size of rafts. Furthermore, we analyze two numerical models related to specific lava flows: (i) a model of fluid flow with rafts inside an inclined channel, and (ii) a model of fluid flow from a single vent on an artificial topography, when the fluid density, its viscosity, and the effusion rate vary with time. Although the studied models do not account for lava solidification, crust formation, and its rupture, the results of the modeling may be used for understanding of flows with breccias before a significant lava cooling.

  5. AMS analysis and flow source relationship of lava flows and ignimbrites from the eastern Trans-Mexican Volcanic Belt, Mexico (United States)

    Caballero, C. I.; Alva-Valdivia, L. M.; Morales-Barrera, W.; Rodríguez, S. R.


    The results of an AMS analysis carried on 36 sites from a late Miocene - Holocene volcanic stratigraphic sequence from the eastern Trans-Mexican Volcanic Belt is presented. 22 sites (450 samples) belong to lava flows, mainly of basaltic composition, from different emission centers from the Xalapa Monogenitc Volcanic Field, (Rodríguez et al 2010, González-Mercado, 2005), "Cofre de Perote Vent Cluster" (CPVC), "Naolinco Volcanic Field" (NVF), (Siebert and Carrasco-Núñez, 2002), and the Chiconquiaco-Palma Sola volcanic complex (López-Infanzón, 1991; Ferrari et al., 2005). 14 sites belong to the widely distributed El Castillo rhyolitic ignimbrite dated 2.44 to 2.21 Ma (Morales-Barrera, 2009) which is a non-welded to welded ignimbrite. AMS measurements were performed with a KLY2 Kappabridge and processed with Anisoft software using Jelinek statistics. Sometimes a density distribution analysis was also performed when magnetic fabric showed more dispersed distribution patterns. AMS ellipsoids from basalt sites show mostly prolate shapes, while those from ignimbrites show mostly oblate shapes, which may partly due to magnetic mineralogy and also to flow dynamics. Flow directions were mostly obtained from the imbrication angle of magnetic foliation (evaluated from kmin axis mean as corresponding to its pole) and considering the symmetry of the axes distribution. Flow direction inferences are discussed in relation with flow source when it is clearly evident from geologic field observations, as it is usually the case with basalt lava flows. While in ignimbrites, flow inferences from petrographic and facies distributions are compared with AMS flow inferences, showing agreement between them in some cases but not in others, may be due to local tilting occurring after ignimbrite emplacement.

  6. Tracing volatile loss during the eruption of individual flood basalt flows in the Columbia River Flood Basalt Province (United States)

    Burton, K. W.; Vye, C.; Gannoun, A.; Self, S.


    Continental flood basalt (CFB) volcanism is characterised by the repeated eruption of huge batches of magma, producing enormous basalt provinces (105-106 km3) over relatively brief intervals of time, and delivering large masses of volcanic gas to the atmosphere. The release of gases and aerosols during CFB volcanism is thought to have had a significant impact on the atmosphere, ocean chemistry and climate [1-3]. The key factors influencing atmospheric chemistry and the environmental impact of CFB eruptions are the timing, mechanism and duration of volatile release during individual eruptions, but for the most part such information remains poorly known. The 187Re-187Os isotope system offers a highly sensitive tracer of the evolution of melt chemistry, and of the timing and mechanism of volatile release. This is partly because the contrasting behaviour of Re and Os during melting results in the extreme fractionation of parent/daughter (Re/Os) isotope ratios, thus magmatic phases can yield precise chronological information, and crustal rocks develop highly radiogenic isotope compositions that can be readily traced if assimilated [4]. Partly also because Re behaves as a highly volatile element during sub-aerial volcanism [5]. This study presents 187Re-187Os isotope data for rocks and minerals from two flows in the Columbia River Flood Basalt Group, one of the youngest flood basalt provinces that formed over a 2 million year interval in the Mid-Miocene. The 2,660 km3 Sand Hollow flow field displays small major and trace element variations, both laterally and vertically across the flow, indicative of fractional crystallisation, but the elemental data cannot be used to distinguish source variations and/or crustal contamination. However, Os isotopes indicate systematic crustal contamination over the timescale of an individual eruption, where the earliest formed lavas show the greatest degree of contamination. Isotope and elemental data for phenocryst phases from the 40

  7. Rheology of Icelandic lava flows as analogues for Mars: comparison between morphometric and experimental determinations (United States)

    Chevrel, M. O.; Platz, T.; Hauber, E.; Baratoux, D.; Dingwell, D. B.


    The rheological properties and emplacement parameters of extra-terrestrial lava flows (effusion rate, yield strength, viscosity), such as those on the Moon and Mars, are commonly derived from their morphology through simple physical models (1). Since observations are mostly limited to remote sensing data (images and topography) with no possible ground-truth evaluations of the results, a critical assessment of these methods is required. In experimental volcanology, the temperature-dependence of liquid viscosity and the effect of crystals on the viscosity of a suspension can be investigated. The purpose of this study is to compare the viscosity obtained from morphometric analysis on terrestrial lava flows to that can be measured in the laboratory (by using samples taken from the same flows). Two postglacial lava flows from the Western Volcanic Zone in Iceland were selected for their similarity with some basaltic lava flows on Mars. The geometrical parameters are estimated from high-resolution Digital Elevation Models obtained with the HRSC-AX camera, which is an airborne version of the High Resolution Stereo Camera on board of ESA`s Mars Express spacecraft. Laboratory techniques are applied to samples collected along the lava flow. The viscosity of the pure liquid lava is measured with the concentric cylinder between 1500°C and 1250° C. The crystallisation sequence during the cooling of the magma during ascent and emplacement at the surface is described from hand samples and is thermodynamically modelled with MELTS (2). The apparent lava viscosity of the magma (residual liquid + crystals) is calculated as a function of temperature from the residual liquid composition (using the GRD model, 3) and characteristics of the solid fraction (using the fit parameters from 4). When the lava erupts, its viscosity is slightly higher than a pure liquid (due to the presence of phenocrysts) and then strongly increases as the groundmass crystallises. Assuming a Newtonian behaviour

  8. Degassing dynamics of basaltic lava lake at a top-ranking volatile emitter: Ambrym volcano, Vanuatu arc (United States)

    Allard, Patrick; Burton, Mike; Sawyer, Georgina; Bani, Philipson


    Persistent lava lakes are rare on Earth and provide volcanologists with a remarkable opportunity to directly investigate magma dynamics and degassing at the open air. Ambrym volcano, in Vanuatu, is one of the very few basaltic arc volcanoes displaying such an activity and voluminous gas emission, but whose study has long remained hampered by challenging accessibility. Here we report the first high temporal resolution (every 5 s) measurements of vigorous lava lake degassing inside its 300 m deep Benbow crater using OP-FTIR spectroscopy. Our results reveal a highly dynamic degassing pattern involving (i) recurrent (100-200 s) short-period oscillations of the volcanic gas composition and temperature, correlating with pulsated gas emission and sourced in the upper part of the lava lake, (ii) a continuous long period (∼8 min) modulation probably due to the influx of fresh magma at the bottom of the lake, and (iii) discrete CO2 spike events occurring in coincidence with the sequential bursting of meter-sized bubbles, which indicates the separate ascent of large gas bubbles or slugs in a feeder conduit with estimated diameter of 6 ± 1 m. This complex degassing pattern, measured with unprecedented detail and involving both coupled and decoupled magma-gas ascent over short time scales, markedly differs from that of quieter lava lakes at Erebus and Kilauea. It can be accounted for by a modest size of Benbow lava lake and its very high basalt supply rate (∼20 m3 s-1), favouring its rapid overturn and renewal. We verify a typical basaltic arc signature for Ambrym volcanic gas and, based on contemporaneous SO2 flux measurements, we evaluate huge emission rates of 160 Gg d-1 of H2O, ∼10 Gg d-1 of CO2 and ∼8 Gg d-1 of total acid gas (SO2, HCl and HF) during medium activity of the volcano in 2008. Such rates make Ambrym one of the three most powerful volcanic gas emitters at global scale, whose atmospheric impact at local and regional scale may be considerable.

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


    Alessandro Fornaciai; Simone Tarquini; Massimiliano Favalli


    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...

  10. Basic Paleomagnetism: Some old and new Lessons From Icelandic Lava Flows (United States)

    Kristjansson, L.


    In the history of paleomagnetic research, sequences of stably-magnetized undisturbed lava flows have been among the best sources of reliable consistent information about the behavior of the geomagnetic field through time. Such sequences occur in scattered locations around the world, not all offering favorable sampling conditions. Iceland's basalt lavas cover more or less continuously the last 15 million years. In the last two million years or so, eruptions here often took place under water or ice, causing stratigraphic complexities. The older subaerially erupted lavas which are on average 10 m thick and separated by thin clastic sediments, form quite regular and accessible series. The lava pile is gently tilted, generally towards the active volcanic zone. Research on these lavas in the 1950's to 1970's, especially by J. Hospers, T. Sigurgeirsson, R.L. Wilson and N.D. Watkins, contributed to several steps in the development of paleomagnetic methods and understanding of variations in the geomagnetic field. Their contributions concerned for instance statistical concepts, stratigraphic correlation, alternating-field demagnetization, the discovery of transitional directions, stability of remanence in lavas, and delineation of short reversal events. As in some of the projects of Wilson and Watkins, subsequent research by the present author has mostly been done in collaboration with geologists interested in mapping composite sections (of order 300 lava flows) through parts of the lava pile. Preference has been given to locations with little hydrothermal alteration or tectonic movements. These sections are pieced together from hillside profiles partly overlapping in age, commonly with 20-60 successive flows in each profile. Single-polarity zones which have very variable thicknesses but on average 15-20 flows, are often useful in correlation; for this however, distances between profiles should be 2-3 km or less rather than, say, 5-10 km. The stratigraphic mapping projects

  11. Geology of the Tyrrhenus Mons Lava Flow Field, Mars (United States)

    Crown, David A.; Mest, Scott C.


    The ancient, eroded Martian volcano Tyrrhenus Mons exhibits a central caldera complex, layered flank deposits dissected by radial valleys, and a 1000+ km-long flow field extending to the southwest toward Hellas Planitia. Past studies suggested an early phase of volcanism dominated by large explosive eruptions followed by subsequent effusive activity at the summit and to the southwest. As part of a new geologic mapping study of northeast Hellas, we are examining the volcanic landforms and geologic evolution of the Tyrrhenus Mons flow field, including the timing and nature of fluvial activity and effects on volcanic units. New digital geologic mapping incorporates THEMIS IR (100 m/pixel) and CTX (5 m/pixel) images as well as constraints from MOLA topography.Mapping results to-date include delineation of the boundaries of the flow field, identification and mapping of volcanic and erosional channels within the flow field, and mapping and analysis of lava flow lobes. THEMIS IR and CTX images allow improved discrimination of the numerous flow lobes that are observed in the flow field, including refinement of the margins of previously known flows and identification of additional and smaller lobes. A prominent sinuous rille extending from Tyrrhenus Mons’ summit caldera is a major feature that supplied lava to the flow field. Smaller volcanic channels are common throughout the flow field; some occur in segments along crests of local topographic highs and may delineate lava tubes. In addition to volcanic channels, the flow field surface is characterized by several types of erosional channels, including wide troughs with scour marks, elongate sinuous channels, and discontinuous chains of elongate pits and troughs. High-resolution images reveal the widespread and significant effects of fluvial activity in the region, and further mapping studies will examine spatial and temporal interactions between volcanism and fluvial processes.

  12. Modelling lava flows by Cellular Nonlinear Networks (CNN: preliminary results

    Directory of Open Access Journals (Sweden)

    C. Del Negro


    Full Text Available The forecasting of lava flow paths is a complex problem in which temperature, rheology and flux-rate all vary with space and time. The problem is more difficult to solve when lava runs down a real topography, considering that the relations between characteristic parameters of flow are typically nonlinear. An alternative approach to this problem that does not use standard differential equation methods is Cellular Nonlinear Networks (CNNs. The CNN paradigm is a natural and flexible framework for describing locally interconnected, simple, dynamic systems that have a lattice-like structure. They consist of arrays of essentially simple, nonlinearly coupled dynamic circuits containing linear and non-linear elements able to process large amounts of information in real time. Two different approaches have been implemented in simulating some lava flows. Firstly, a typical technique of the CNNs to analyze spatio-temporal phenomena (as Autowaves in 2-D and in 3-D has been utilized. Secondly, the CNNs have been used as solvers of partial differential equations of the Navier-Stokes treatment of Newtonian flow.

  13. Location and extent of recently active lava flows on the eastern flank of Idunn Mons on Venus (United States)

    D'Incecco, Piero; Mueller, Nils; Helbert, Joern; D'Amore, Mario


    The eastern flank of Idunn Mons, Imdr Regio's single large volcano, was identified in VIRTIS data as one of the regions with relatively high values of thermal emissivity at 1 μm wavelength. Our study intends to identify location and extent of the sources of such anomalies, thus the lava flows responsible for the relatively high emissivity observed by VIRTIS over the eastern flank of Idunn Mons. We perform a simulation iterating the geologic mapping made over Magellan radar images of the same area with modeling of the blurring caused by the scattering of the 1 μm radiation in the atmosphere. At every iteration, we map the lava flow units in the surroundings of Idunn Mons and we assign each unit an assumed value of emissivity. We observed a good match between the mapped flows and the clusters resulting from the consistency of the mapped lava flows through the ISO clustering analysis. We tested eight different configurations, calculating the total RMS error compared to VIRTIS observations. The best-fit configuration is that where we assigned high values of emissivity to the flank lava flows. Results also show a correlation between the ISO clustering analysis and the best-fit configuration. We reconstructed the post-eruption stratigraphy of the eastern flank of Idunn Mons, displaying the three flank lava flows units likely responsible for the relatively high 1 μm emissivity anomalies observed by VIRTIS. The average microwave emissivity provides a further evidence of the basaltic composition of the mapped lava flows.

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

    Directory of Open Access Journals (Sweden)

    Eugenio Rustico


    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. Rock size distributions on lava flow surfaces: New results from a range of compositions (United States)

    Burke, M. P.; Anderson, S. W.; Bulmer, M. H.


    We measured block sizes along 15-25m orthogonal transects on 12 lava flows of compositions ranging from basalt to rhyolite. At each site, we stretched a line across the flow surface then measured the length of each block cut by this line that were greater than 3-12cm (depending on composition). The measurements from each site were reduced to cumulative size frequency distribution plots, with block size (D) plotted against the fraction of the line f(D) composed of blocks greater than or equal to that size, and fitted with an exponential curve of the form f(D) = k exp(-qD) where k is the intercept and q is the decay parameter. Average block size and geometric mean were also determined for each site. Our data show no clear trends linking average or mean block size to composition, although there does seem to be relationship between block size and the decay parameter. Block size corresponds with the decay parameter at each site except for the basaltic andesite flow at Paint Pot Crater (CA). Many sites at this flow were covered with secondary spatter deposits. Largest blocks and smallest decay parameters were found for the andesite flows at Sabancaya (Peru), while the basalt flows at Cima (CA) exhibited the smallest blocks and largest decay parameters. The second largest block sizes occurred at the four Inyo domes composed of both crystal-rich and glassy rhyolite, and these domes also showed the second smallest decay parameters. All four of the Inyo domes were emplaced along the same feeder dike trend, and the average and mean sizes and decay parameters at these domes are nearly identical, suggesting that composition, extrusion rate, or eruption history controls the block size distributions. However, values for the two andesitic flows, Mt. Shasta (CA) and Sabancaya, were very different, suggesting that extrusion rate and/or eruption history exert a stronger control over the block size distributions than does composition. LIDAR data sets are capable of detecting sub

  16. Experimental study of the surface thermal signature of gravity currents: application to the assessment of lava flow effusion rate (United States)

    Garel, F.; Kaminski, E.; Tait, S.; Limare, A.


    During an effusive volcanic eruption, the crisis management is mainly based on the prediction of lava flows advance and its velocity. As the spreading of lava flows is mainly controlled by its rheology and the eruptive mass flux, the key question is how to evaluate them during the eruption (rather than afterwards.) A relationship between the heat flux lost by the lava at its surface and the eruption rate is likely to exist, based on the first-order argument that higher eruption rates should correspond to larger power radiated by a lava flow. The semi-empirical formula developed by Harris and co-workers (e.g. Harris et al., Bull. Volc. 2007) is currently used to estimate lava flow rate from satellite surveys yielding the surface temperatures and area of the lava flow field. However, this approach is derived from a static thermal budget of the lava flow and does not explicitly model the time-evolution of the surface thermal signal. Here we propose laboratory experiments and theoretical studies of the cooling of a viscous axisymmetric gravity current fed at constant flux rate. We first consider the isoviscous case, for which the spreading is well-know. The experiments using silicon oil and the theoretical model both reveal the establishment of a steady surface thermal structure after a transient time. The steady state is a balance between surface cooling and heat advection in the flow. The radiated heat flux in the steady regime, a few days for a basaltic lava flow, depends mainly on the effusion rate rather than on the viscosity. In this regime, one thermal survey of the radiated power could provide a consistent estimate of the flow rate if the external cooling conditions (wind) are reasonably well constrained. We continue to investigate the relationship between the thermal radiated heat flux and the effusion rate by using in the experiments fluids with temperature-dependent viscosity (glucose syrup) or undergoing solidification while cooling (PEG wax). We observe a

  17. Extensive young dacite lava flows between boninite and BABB in a backarc setting: NE Lau Basin (United States)

    Embley, R. W.; Rubin, K. H.


    Several hundred square kilometers of young dacite lava flows mapped by their high acoustic backscatter erupted in several batches in proximity to boninite and back-arc basin basalt (BABB) in the NE Lau Basin, the world's fastest opening back-arc region and a site proposed as a modern analogue in some ophiolite models. Where sampled, these lavas are aphyric, glassy dacites and are not associated with andesite extrusives (commonly observed elsewhere). Several flow fields occur on the flank of the large silicic Niuatahi seamount. Two of the largest lava fields and several smaller ones (~220 km2) erupted as far as 60 km north of Niuatahi. Their occurrence is likely controlled by crustal fractures from the long-term extension in this rear-arc region. Determining thickness of these flows is problematic, but relief of 30-100 m on flow fronts and in collapsed areas yields volume estimates as high as ~7-18 km3 for the northern group. The mean silica content of the largest and best sampled dacite flow field (LL-B) is 65.6 ±0.2%, a remarkably consistent composition for such an extensive flow (~140 km2). Camera tows show lower viscosity flow forms, including many anastomatosing pillow tubes and ropey surfaces, as well as endogenous domes, ridges and lobes (some with "crease-like" extrusion ridges, and inflated lobes with extrusion structures). An enigmatic 2 x 1.5 km, 30-m deep collapse depression could mark an eruption center for the LL-B flow field. Low viscosity flow morphologies on portions of LL-B and a nearby smaller flow field implies high effusion rates during some phases of the eruption(s), which in turn implies some combination of higher than normal liquidus temperature and high water content. Submarine dacite flows have been described in ancient sequences from the Archaean through the Miocene but this is the first modern occurrence of large volume submarine dacite flows. The volume of these young dacite flows implies the presence of large differentiated melt

  18. Inverse steptoes in Las Bombas volcano, as an evidence of explosive volcanism in a solidified lava flow field. Southern Mendoza-Argentina (United States)

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


    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.

  19. Erosion and assimilation of substrate by Martian low-viscosity lava flows: implications for sulphur degassing and the genesis of orthomagmatic Ni-Cu±(PGE) sulphide mineralisation (United States)

    Baratoux, D.; Baumgartner, R. J.; Gaillard, F.; Fiorentini, M. L.


    Archean and Proterozoic komatiites and ferropicrites are mantle plume-related, low-viscosity, high-temperature, mafic to ultramafic lava flows. They are hosts to Ni-Cu±(PGE) sulphide mineralisation, which generally formed due to the segregation of sulphides following thermo-mechanical erosion and assimilation of sulphur-rich crustal rocks. We numerically simulated erosion and assimilation during the turbulent emplacement of iron-rich Martian lavas displaying chemical and rheological analogies with terrestrial mafic to ultramafic lavas, on a variety of basaltic and sedimentary sulphate-rich substratum. With the adoption of the lava flow and erosion model of Williams et al. (JGR, 1998), thermodynamic simulations were implemented to (semi-) quantify the potential changes in melt parameter (i.e., chemistry, temperature, and oxygen fugacity) that dictate the sulphur capacity of silicate melts. Modelling was also performed to assess the role of volatile degassing (Gaillard et al., SSR, 2013) on the sulphur inventory of Martian lavas. Our modelling show that lavas emplacing over basaltic crust are governed by low cooling rates, as well as low erosion and assimilation capacities, thus resulting in calculated near-cotectic proportions of sulphides segregating relatively late upon lava emplacement (usually > 100 km flow distance). The rapid assimilation of highly erodible and sulphate-rich Martian regolith may trigger sulphide supersaturation and batch segregation of sulphides well above cotectic proportions relatively early during the establishment of magmatic flow (<100 km flow distance). However, the assimilation of sulphate, which serves as a strongly oxidising agent, could result in dramatic sulphur loss due to increased volatile degassing rates. This process may limit or even counteract the overall positive effect of sulphate assimilation on achieving sulphide supersaturation, sulphide segregation and the genesis of Ni-Cu±(PGE) sulphide mineralisation.

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


    Ciro Del Negro; Annamaria Vicari; Annalisa Cappello


    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 t...

  1. Topaz rhyolites of Nathrop, Colorado: Lava domes or rheomorphic flows? (United States)

    Hernandez, B. M.; Panter, K. S.; Van Der Voo, R.


    Deposits of topaz-bearing rhyolite at Ruby and Sugarloaf Mountains in central Colorado are considered to be remnants of lava domes. The deposits are part of the Late Eocene-Oligocene Central Colorado Volcanic Field [1] that lies along the eastern margin of the Arkansas Graben of the Rio Grande Rift. Topaz-bearing rhyolite lava domes and flows have been identified elsewhere in Colorado and the western U.S., but an assortment of geomorphological, lithostratigraphical, and textural features of Ruby and Sugarloaf Mountains call into question their strict classification as such. Alternatively, the lava flows may be interpreted as rheomorphic ignimbrites. The volcanic deposits encompass a sequence of steeply (~70°) west-dipping units that form two N-S elongated edifices ~0.5 km long and a few hundred meters high. Their common lithostratigraphy from bottom to top is tuff breccia, vitrophyre, and flow-banded rhyolite. The tuff breccia includes large (up to ~1 m) pumice blocks and lithics that vary from nearly absent to moderately abundant (10-20%). At Sugarloaf lithics include rare cobble-sized clasts of granite, but the majority consists of flow-banded rhyolite. The tuff breccia grades normally upward into the vitrophyre with increased welding and a eutaxitic fabric defined by fiamme with increasing aspect ratios. Lithics are abundant in the vitrophyre at Sugarloaf but are rare or absent in the vitrophyre at Ruby Mountain. The transition from the vitrophyre to the flow-banded rhyolite is abrupt (welding fabric is apparent at both locations. At Ruby Mountain, evidence of vapor-phase alteration and an interlocked mosaic of quartz crystals in the groundmass is not typically found in deposits of effusive origin and is not a result of metamorphism. Preliminary remnant magnetism (RM) indicates no discernible tectonic modification of deposits on Sugarloaf Mountain, indicating that the steep westward dip is a primary depositional feature. This result supports the view of a

  2. Pioneer microbial communities of the Fimmvörðuháls lava flow, Eyjafjallajökull, Iceland. (United States)

    Kelly, Laura C; Cockell, Charles S; Thorsteinsson, Thorsteinn; Marteinsson, Viggó; Stevenson, John


    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.

  3. RIS4E at Kilauea's December 1974 Flow: Lava Flow Texture LiDAR Signatures (United States)

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


    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

  4. Cosmic ray exposure dating with in situ produced cosmogenic He-3 - Results from young Hawaiian lava flows (United States)

    Kurz, Mark D.; Colodner, Debra; Trull, Thomas W.; Moore, Richard B.; O'Brien, Keran


    Cosmogenic helium contents in a suite of Hawaiian radiocarbon-dated lava flows were measured to study the use of the production rate of spallation-produced cosmogenic He-3 as a surface exposure chronometer. Basalt samples from the Mauna Loa and Hualalai volcanoes were analyzed, showing that exposure-age dating is feasible in the 600-13000 year age range. The data suggest a present-day sea-level production rate in olivine of 125 + or - 30 atoms/g yr.

  5. NVP melt/magma viscosity: insight on Mercury lava flows (United States)

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


    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

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

    Directory of Open Access Journals (Sweden)

    Alessandro Fornaciai


    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.

  7. Morphological complexities and hazards during the emplacement of channel-fed `a`ā lava flow fields: A study of the 2001 lower flow field on Etna (United States)

    Applegarth, L. J.; Pinkerton, H.; James, M. R.; Calvari, S.


    Long-lived basaltic eruptions often produce structurally complex, compound `a`ā flow fields. Here we reconstruct the development of a compound flow field emplaced during the 2001 eruption of Mt. Etna (Italy). Following an initial phase of cooling-limited advance, the reactivation of stationary flows by superposition of new units caused significant channel drainage. Later, blockages in the channel and effusion rate variations resulted in breaching events that produced two new major flow branches. We also examined small-scale, late-stage ‘squeeze-up’ extrusions that were widespread in the flow field. We classified these as ‘flows’, ‘tumuli’ or ‘spines’ on the basis of their morphology, which depended on the rheology, extrusion rate and cooling history of the lava. Squeeze-up flows were produced when the lava was fluid enough to drain away from the source bocca, but fragmented to produce blade-like features that differed markedly from `a`ā clinker. As activity waned, increased cooling and degassing led to lava arriving at boccas with a higher yield strength. In many cases this was unable to flow after extrusion, and laterally extensive, near-vertical sheets of lava developed. These are considered to be exogenous forms of tumuli. In the highest yield strength cases, near-solid lava was extruded from the flow core as a result of ramping, forming spines. The morphology and location of the squeeze-ups provides insight into the flow rheology at the time of their formation. Because they represent the final stages of activity of the flow, they may also help to refine estimates of the most advanced rheological states in which lava can be considered to flow. Our observations suggest that real-time monitoring of compound flow field evolution may allow complex processes such as channel breaching and bocca formation to be forecast. In addition, documenting the occurrence and morphology of squeeze-ups may allow us to determine whether there is any risk of a

  8. Three-phase flow dynamics in the lava lakes at Mount Erebus, Antarctica (United States)

    Qin, Z.; Suckale, J.


    Long-lived, persistently active lava lakes expose the top of a convecting magma column to direct observation and offer a unique window into the cryptic magmatic plumbing system at depth. In this paper, we focus on the lava lake at Mount Erebus, a large intraplate stratovolcano at Ross Island, Antarctica, to gain new insights into the multi-phase interactions between gas bubbles, crystals and magmatic liquid in basaltic volcanoes. Early studies of magmatic convection have considered multi-phase magmas as perfectly homogeneous mixtures. The high proportion of erupted gas relative to magma, however, suggests that gas separates from the flow and drives eruptive activity. Similarly, the large size (up to 10cm) of the megacrysts that make up 97% of the crystal cargo at Erebus begs the question whether these crystals are likely to remain entrained and how crystal segregation in the lava lakes and conduit alters eruptive behavior. We study the multiphase behavior of magmatic convection at Mount Erebus through two dimensional numerical simulations. Our model was developed with Mount Erebus in mind, but we argue that it could also serve as a virtual laboratory for studying multiphase flow in other basaltic systems. To accurately capture the deformability, breakup and coalescence of large gas bubbles, we track the gas-liquid interfaces with level-set functions. The crystal phase is incorporated using distributed Lagrange multipliers. We discretize the multiphase Stokes and energy equation through an iterative finite difference method that captures the potentially discontinuous jumps in the pressure, stresses, density and viscosity through a Ghost-Fluid approach. We have benchmarked and validated our numerical approach against analytical results and laboratory experiments. We synthesize observations of thermal flux, seismic behavior, geodesy and geochemistry to deduce constraints on the mass flux, conduit dimensions, reservoir size, and crystal growth as a basis for our

  9. Depleted basaltic lavas from the proto-Iceland plume, Central East Greenland

    DEFF Research Database (Denmark)

    Waight, Tod Earle; Baker, Joel A.


    ridges considered to be derived from upper mantle sources polluted by the Iceland plume. However, small positive Pb peaks when normalised to MORB, and lower Nb distinguish the CEG low-Ti basalts from depleted Icelandic compositions. The lower ¿Nb (... in crustally uncontaminated parental melts implies a closer affinity to compositions from the oceanic ridges surrounding Iceland (especially Reykjanes), yet they are subtly distinct on the basis of available trace element data. We suggest that this depleted component was an integral part of the plume...

  10. Subglacial lava propagation, ice melting and heat transfer during emplacement of an intermediate lava flow in the 2010 Eyjafjallajökull eruption (United States)

    Oddsson, Björn; Gudmundsson, Magnús T.; Edwards, Benjamin R.; Thordarson, Thorvaldur; Magnússon, Eyjólfur; Sigurðsson, Gunnar


    During the 2010 Eyjafjallajökull eruption in South Iceland, a 3.2-km-long benmoreite lava flow was emplaced subglacially during a 17-day effusive-explosive phase from April 18 to May 4. The lava flowed to the north out of the ice-filled summit caldera down the outlet glacier Gígjökull. The flow has a vertical drop of about 700 m, an area of ca. 0.55 km2, the total lava volume is ca. 2.5·107 m3 and it is estimated to have melted 10-13·107 m3 of ice. During the first 8 days, the lava advanced slowly (caldera where the ice was 60-100 m thick. This subglacial lava flow was emplaced along meltwater tunnels under ice for the entire 3.2 km of the flow field length and constitutes 90 % of the total lava volume. The remaining 10 % belong to subaerial lava that was emplaced on top of the subglacial lava flow in an ice-free environment at the end of effusive activity, forming a 2.7 km long a'a lava field. About 45 % of the thermal energy of the subglacial lava was used for ice melting; 4 % was lost with hot water; about 1 % was released to the atmosphere as steam. Heat was mostly released by forced convection of fast-flowing meltwater with heat fluxes of 125-310 kWm-2.

  11. Possible lava tube system in a hummocky lava flow at Daund, western Deccan Volcanic Province, India

    Indian Academy of Sciences (India)

    Raymond A Duraiswami; Ninad R Bondre; Gauri Dole


    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. The lava tube system is exposed as several exhumed outcrops and is composed of complex branching and discontinuous segments. The roof of the lava tube has collapsed but original lava tube walls and fragments of the tube roof are seen at numerous places along the tube. At some places the tube walls exhibit a single layer of lava lining, whereas, at other places it shows an additional layer characterised by smooth surface and polygonal cracks. The presence of a branching and meandering lava tube system in the Daund flow, which represents the terminal parts of Thakurwadi Formation, shows that the hummocky flow developed at a low local volumetric flow rate. This tube system developed in the thinner parts of the flow sequence; and tumuli developed in areas where the tube clogged temporarily in the sluggish flow.

  12. Platinum-alloy and sulfur saturation in an arc-related basalt to rhyolite suite: Evidence from the Pual Ridge lavas, the Eastern Manus Basin (United States)

    Park, Jung-Woo; Campbell, Ian H.; Arculus, Richard J.


    We have measured the platinum group element (PGE) and Re concentrations of arc-type lavas from the Pual Ridge and the surrounding area in the Eastern Manus Basin. These magmas followed an Fe-enrichment trend to produce a wide range of compositions with MgO varying between 8 and 0.1 wt.%. We found distinct differences in the PGE geochemistry of the high (>3 wt.% MgO) and the low-Mg lavas (high-Mg lavas suggest that the depletion of these elements is due to Pt-rich alloy saturation. This is consistent with the high Pt contents in the high-Mg lavas, which is close to the solubility of Pt in the basaltic melt at similar conditions. In contrast, the concentrations of all PGE and Re drop rapidly in the low-Mg lavas (except for Ru and Ir), with the PGE concentrations falling at a rate that is appreciably faster than Cu, which we attribute to sulfide saturation. As a consequence, there is a marked decline in Pd/Cu in the low-Mg lavas and we suggest that this ratio is the best indicator of sulfide saturation in an evolving magmatic system. A feature of the data is that duplicate analyses of the same sample often do not agree within error. We attribute this scatter to the nugget effect, with nuggets of a Pt-rich alloy in the high-Mg lavas and sulfide blebs in the low-Mg lavas. The PGE concentrations of phenocryst-bearing high-Mg lavas are higher than in the associated glassy lavas, and scatter on MgO variation diagrams is significantly reduced if only glassy lavas are considered, which indicates that the micron scale Pt-rich alloy grains are intimately associated with the phenocrysts. Our results provide strong evidence that Pt-rich alloys can crystallize from a basaltic-andesitic magma, along with the silicate minerals, and fractionate Pt from Pd during magmatic differentiation. As a consequence, Pd/Pt increases during Pt alloy fractionation and this ratio can be used to identify Pt-rich metal saturation. The Pual Ridge alloys are Pt-rich because the primary magmas are Pt

  13. Retrieving geomagnetic secular variations from lava flows: evidence from Mounts Arso, Etna and Vesuvius (southern Italy) (United States)

    Incoronato, Alberto; Angelino, Antimo; Romano, Romolo; Ferrante, Agostino; Sauna, Renata; Vanacore, Gianpio; Vecchione, Claudio


    Mean directions of magnetization from Mounts Arso (Ischia Island, Gulf of Naples), Etna and Vesuvius lava flows have been determined based on very stringent linearity criteria. These indicate that, regardless of the source volcano, the lava flow mean directions of magnetization form a common path, the SISVC (Southern Italy Secular Variation Curve). This curve enables a reassessment of the age of eruption of several lavas. A date of AD 1169 is demonstrated to be the only possible time of emplacement for one Etna lava flow previously assigned an age of AD 812/1169. It is also demonstrated that two Etna lava flows, which, according to the literature, were emplaced in AD 1536 and 1595 respectively, were actually both emplaced around AD 1037. Three other Etna lava flows, one ascribed to AD 1566 and two to AD 1595, were actually emplaced between AD 1169 and 1284/85. The same time window also holds for a Vesuvius lava flow for which only an upper time threshold was previously available. Only one of the studied flows needs further sampling and analysis to verify whether this flow has been affected by a complete remagnetization or has an erroneous historical dating. The applied procedure seems to be the most appropriate one in carrying out palaeomagnetic surveys of lava flows, as also suggested by the broad agreement with some 17th and 19th century measurements of the geomagnetic field in Rome, relocated to Etna, and is likely to improve knowledge of past history of a volcano significantly.

  14. The eruption characteristics of the Tarim flood basalt



    Integration of field investigation, regional stratigraphic comparison, remote sensing and image interpretation allow us to divide the Tarim Permian flood basalt province into three eruptive cycles listed by decreasing age; Kupukuziman flood basalt (KP), Felsic pyroclastic rocks (FP), Kaipaizileike flood basalt (KZ). KP features flood basalt and tuff; in the outcrop in Keping and Yingmaili areas, it can be differentiated into two units containing three thick layers of basaltic lava flows. Thes...

  15. Geochemistry of Mesozoic Basaltic Lavas from the West Pacific Seamount Province (WPSP): Constraints on Their Origin and Genesis (United States)

    Yan, Q.; Shi, X.


    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)

  16. Exploring Inflated Pahohoe Lava Flow Morphologies and the Effects of Cooling Using a New Simulation Approach (United States)

    Glaze, L. S.; Baloga, S. M.


    Pahoehoe lavas are recognized as an important landform on Earth, Mars and Io. Observations of such flows on Earth (e.g., Figure 1) indicate that the emplacement process is dominated by random effects. Existing models for lobate a`a lava flows that assume viscous fluid flow on an inclined plane are not appropriate for dealing with the numerous random factors present in pahoehoe emplacement. Thus, interpretation of emplacement conditions for pahoehoe lava flows on Mars requires fundamentally different models. A new model that implements a simulation approach has recently been developed that allows exploration of a variety of key influences on pahoehoe lobe emplacement (e.g., source shape, confinement, slope). One important factor that has an impact on the final topographic shape and morphology of a pahoehoe lobe is the volumetric flow rate of lava, where cooling of lava on the lobe surface influences the likelihood of subsequent breakouts.

  17. SHARAD Constrains on Lava Flow Properties at Southeastern Utopia Planitia (United States)

    Nunes, D. C.


    with the middle to upper range of permittivities for basalt, and, therefore, porosity does not dominate the volume of the lobate flow, and supports the morphologic interpretation of the flow and geologic history of this area offered by Russell and Head [2003] and Tanaka et al. [2003]. Russell P. S. and Head J. W. [2003] JGR, 108, 5064. Tanaka K. L. et al. [2005], USGS Sci. Invest. Maps, 2888. Werner S. C. et al. [2011], PSS, 59, 1143-1165.

  18. Extending Interfield Analysis of Tumuli on Terrestrial Inflated Lava Flows to Mars (United States)

    Sangha, S. S.; Diniega, S.; Smrekar, S. E.


    In our study, we identify and measure tumuli - small-scale, positive topographic features (~10m in width) - on both terrestrial and Martian inflated lava flows. Inflated lava flows are aptly named for their domed, rigid upper crust that insulates and is lifted by a fluid interior. Locally high magmatic pressures arising from the transport of lava through a network of subsurface lava pathways within these flows can cause a section of the upper crust to tilt upwards and outwards on opposite sides of an axial fracture and produce a tumulus. Thus, tumuli can be used as records of a flow's interior structure. We aim to quantitatively investigate hypothesized relationships between tumuli morphometrics (such as tumuli sizes, shapes, and orientations) and larger-scale lava flow emplacement structure (flow directions, placement of flow boundaries, and scale of the flow). Measurements of >2000 tumuli on six diverse terrestrial fields and also >2000 tumuli on seven Martian fields within the Elysium Planitia region suggest that: (1) Tumuli form predominantly over very low slopes (source vents, due to increasing bifurcations in lava pathways within the distal portions of the flow, and (4) Tumuli elongation (length/width ratio) decreases away from the source vent. Furthermore, basic tumuli dimensions (length, width, elongation, etc.) are strikingly similar between the planets--suggesting commonality in tumuli formation. Additionally, we have not yet found tumuli on Martian lava flows outside of very young flows within Elysium Planitia (features may be very susceptible to degradation and have eroded beyond recognition on older flows. Our study may thus provide information about regional or global changes in lava eruption and flow emplacement dynamics on Mars. [Left] Tumulus from Amboy lava field, CA. [Right] Two tumuli from Elysium Planitia, Mars. Summary of terrestrial and Martian tumuli survey measurements

  19. Late Holocene lava flow morphotypes of the northern Harrat Rahat, Kingdom of Saudi Arabia: implications for the description of continental lava fields (United States)

    Murcia, H. F.; Nemeth, K.; Moufti, R.; Lindsay, J. M.; El-Masry, N.; Cronin, S. J.; Qaddah, A.; Smith, I. E.


    Lava morphotype refers to the surface morphology of a lava flow after solidification. In Saudi Arabia, young and well-preserved mafic lava fields (Harrats) display a wide range of these morphotypes. This study examines those exhibited by four of the post-4500 yrs. BP lava fields in the northern Harrat Rahat (morphotypes, and proposes a preliminary correlation with whole-rock chemical composition. The Harrat Rahat lava fields include one or more lobes that may extend over 20 km from the source, with thicknesses varying between 1-2 m up to 12 m. Each lava flow episode covered areas between ~32 and ~61 km2, with individual volumes estimated between ~0.085 and ~0.29 km3. The whole-rock chemical compositions of these lavas lie between 44.3 to 48.4% SiO2, 9.01-4.28% MgO and 3.13-6.19% NaO+K2O. Seven different morphotypes with several lava structures are documented: Shelly, Slabby, Rubbly-pahoehoe, Platy, Cauliflower, Rubbly-a'a, and Blocky. These may be related to the shear strain and/or apparent viscosity of the lava flows formed from typical pahoehoe (pure or Hawaiian-pahoehoe, or sheet-pahoehoe). The well-preserved lava fields in Harrat Rahat allow the development of a more expanded classification scheme than has been traditionally applied. In addition to the whole-rock composition, these morphotypes may be indicators of other properties such as vesicularity, crystallization, effusion mechanism, as well as significant along-flow variations in topography and lava thickness and temperature that modify the rheology. The linearity of transitions between morphotypes observed in the lava fields suggest that real time forecasting of the evolution of lava flows might be possible.

  20. Rheology and Morphology of a Trachybasaltic Lava Flow: a Case Study from the Cima Volcanic Field (CA) (United States)

    Soldati, A.; Beem, J. R.; Robertson, T.; Gomez, F. G.; Whittington, A. G.


    Subliquidus rheology of a trachybasaltic lava was measured in the laboratory for the first time. Field observations of the parent flow focused on surface morphology characterization, which was later quantified in terms of surface roughness. The studied lava flow was emitted during the Holocene by a monogenetic cinder cone in the Cima Volcanic Field (CA). Surface morphology transitions from smooth pahoehoe ropes near the vent to jagged `a`a blocks over the majority of the flow. A variety of 2 m2 outcrops were photographed using a hand-held DSLR camera, and their surface texture was reconstructed with photogrammetry. The roughness of each outcrop, effectively described by the standard deviation between the real photogrammetric point cloud and the best-fitting surface, was quantified at different spatial scales, ranging from 0.5 cm to 200 m. We found that the roughness of the flow increases linearly as spatial resolution decreases, with a slope break corresponding to the average size of the outcrop lava blocks. The rheology of Cima lavas was determined by concentric cylinder viscometry in the 1220 °C to 1160 °C temperature range. The obtained rheological flow curves indicate a Bingham rheology, with clearly detected yield strength ranging from 25 Pa at the higher temperatures up to 650 Pa at the lower temperatures. Plagioclase crystallization begins at 1170 °C, likely playing a key role in promoting yield strength escalation. Viscosity increases by one order of magnitude (from 94 to 1116 Pa·s) over the 60 °C span of cooling considered, remaining consistently lower than most basaltic melts due to the high alkali content (6 wt%). The rheological and morphological results are being integrated, in order to assess if it is possible to identify the rheological fingerprint of the active flow on the preserved flow morphology. The composition-dependence of the morphological pahoehoe to `a`a transition in a rheological map is being assessed by comparing our results to

  1. Determination of thermal/dynamic characteristics of lava flow from surface thermal measurements (United States)

    Ismail-Zadeh, Alik; Melnik, Oleg; Korotkii, Alexander; Tsepelev, Igor; Kovtunov, Dmitry


    Rapid development of ground based thermal cameras, drones and satellite data allows getting repeated thermal images of the surface of the lava flow. Available instrumentation allows getting a large amount of data during a single lava flow eruption. These data require development of appropriate quantitative techniques to link subsurface dynamics with observations. We present a new approach to assimilation of thermal measurements at lava's surface to the bottom of the lava flow to determine lava's thermal and dynamic characteristics. Mathematically this problem is reduced to solving an inverse boundary problem. Namely, using known conditions at one part of the model boundary we determine the missing condition at the remaining part of the boundary. Using an adjoint method we develop a numerical approach to the mathematical problem based on the determination of the missing boundary condition and lava flow characteristics. Numerical results show that in the case of smooth input data lava temperature and velocity can be determined with a high accuracy. A noise imposed on the smooth input data results in a less accurate solution, but still acceptable below some noise level. The proposed approach to assimilate measured data brings an opportunity to estimate thermal budget of the lava flow.

  2. The significance of late-stage processes in lava flow emplacement: squeeze-ups in the 2001 Etna flow field (United States)

    Applegarth, L. J.; Pinkerton, H.; James, M. R.


    The general processes associated with the formation and activity of ephemeral boccas in lava flow fields are well documented (e.g. Pinkerton & Sparks 1976; Polacci & Papale 1997). The importance of studying such behaviour is illustrated by observations of the emplacement of a basaltic andesite flow at Parícutin during the 1940s. Following a pause in advance of one month, this 8 km long flow was reactivated by the resumption of supply from the vent, which forced the rapid drainage of stagnant material in the flow front region. The material extruded during drainage was in a highly plastic state (Krauskopf 1948), and its displacement allowed hot fluid lava from the vent to be transported in a tube to the original flow front, from where it covered an area of 350,000 m2 in one night (Luhr & Simkin 1993). Determining when a flow has stopped advancing, and cannot be drained in such a manner, is therefore highly important in hazard assessment and flow modelling, and our ability to do this may be improved through the examination of relatively small-scale secondary extrusions and boccas. The 2001 flank eruption of Mt. Etna, Sicily, resulted in the emplacement of a 7 km long compound `a`ā flow field over a period of 23 days. During emplacement, many ephemeral boccas were observed in the flow field, which were active for between two and at least nine days. The longer-lived examples initially fed well-established flows that channelled fresh material from the main vent. With time, as activity waned, the nature of the extruded material changed. The latest stages of development of all boccas involved the very slow extrusion of material that was either draining from higher parts of the flow or being forced out of the flow interior as changing local flow conditions pressurised parts of the flow that had been stagnant for some time. Here we describe this late-stage activity of the ephemeral boccas, which resulted in the formation of ‘squeeze-ups' of lava with a markedly different

  3. The Fe-rich clay microsystems in basalt-komatiite lavas: importance of Fe-smectites for pre-biotic molecule catalysis during the Hadean eon. (United States)

    Meunier, Alain; Petit, Sabine; Cockell, Charles S; El Albani, Abderrazzak; Beaufort, Daniel


    During the Hadean to early Archean period (4.5-3.5 Ga), the surface of the Earth's crust was predominantly composed of basalt and komatiite lavas. The conditions imposed by the chemical composition of these rocks favoured the crystallization of Fe-Mg clays rather than that of Al-rich ones (montmorillonite). Fe-Mg clays were formed inside chemical microsystems through sea weathering or hydrothermal alteration, and for the most part, through post-magmatic processes. Indeed, at the end of the cooling stage, Fe-Mg clays precipitated directly from the residual liquid which concentrated in the voids remaining in the crystal framework of the mafic-ultramafic lavas. Nontronite-celadonite and chlorite-saponite covered all the solid surfaces (crystals, glass) and are associated with tiny pyroxene and apatite crystals forming the so-called "mesostasis". The mesostasis was scattered in the lava body as micro-settings tens of micrometres wide. Thus, every square metre of basalt or komatiite rocks was punctuated by myriads of clay-rich patches, each of them potentially behaving as a single chemical reactor which could concentrate the organics diluted in the ocean water. Considering the high catalytic potentiality of clays, and particularly those of the Fe-rich ones (electron exchangers), it is probable that large parts of the surface of the young Earth participated in the synthesis of prebiotic molecules during the Hadean to early Archean period through innumerable clay-rich micro-settings in the massive parts and the altered surfaces of komatiite and basaltic lavas. This leads us to suggest that Fe,Mg-clays should be preferred to Al-rich ones (montmorillonite) to conduct experiments for the synthesis and the polymerisation of prebiotic molecules.

  4. Geochemical Stratigraphy of Southern Parana' Lava Piles (United States)

    Marzoli, A.; De Min, A.; Marques, L. S.; Nardy, A.; Chiaradia, M.


    Basaltic lava flows of the Paranà Large Igneous Province exhibit significant regional and stratigraphic geochemical variations. While the most notable difference concerns the dominance of low-Ti (TiO2 Esmeralda low-Ti basalts (these latter being present both towards the base and the top of the sequence) in Paranà State, while in Santa Caterina State Gramado flows are interlayered with Urubici-type high-Ti basalts. The interlayering of distinct basaltic magma type requires near-synchronous eruption of chemically strongly different magma types generated from clearly heterogeneous mantle sources and erupted through separated magma plumbing systems, without apparent interaction (mixing) among the distinct basalts. In conclusion, the relative timing of low- and high-Ti magma types seems to be much more complicated than previously thought, as for example Esmeralda or Pitanga basalts, previously considered as quite late and postdating Gramado basalts, are indeed synchronous with them.

  5. Fractionation of the platinum-group elments and Re during crystallization of basalt in Kilauea Iki Lava Lake, Hawaii (United States)

    Pitcher, L.; Helz, R.T.; Walker, R.J.; Piccoli, P.


    Kilauea Iki lava lake formed during the 1959 summit eruption of Kilauea Volcano, then crystallized and differentiated over a period of 35??years. It offers an opportunity to evaluate the fractionation behavior of trace elements in a uniquely well-documented basaltic system. A suite of 14 core samples recovered from 1967 to 1981 has been analyzed for 5 platinum-group elements (PGE: Ir, Os, Ru, Pt, Pd), plus Re. These samples have MgO ranging from 2.4 to 26.9??wt.%, with temperatures prior to quench ranging from 1140????C to ambient (110????C). Five eruption samples were also analyzed. Osmium and Ru concentrations vary by nearly four orders of magnitude (0.0006-1.40??ppb for Os and 0.0006-2.01??ppb for Ru) and are positively correlated with MgO content. These elements behaved compatibly during crystallization, mostly likely being concentrated in trace phases (alloy or sulfide) present in olivine phenocrysts or included chromite. Iridium also correlates positively with MgO, although less strongly than Os and Ru. The somewhat poorer correlation for Ir, compared with Os and Ru, may reflect variable loss of Ir as volatile IrF6 in some of the most magnesian samples. Rhenium is negatively correlated with MgO, behaving as an incompatible trace element. Its behavior in the lava lake is complicated by apparent volatile loss of Re, as suggested by a decrease in Re concentration with time of quenching for lake samples vs. eruption samples. Platinum and Pd concentrations are negatively, albeit weakly, correlated with MgO, so these elements were modestly incompatible during crystallization of the major silicate phases. Palladium contents peaked before precipitation of immiscible sulfide liquid, however, and decline sharply in the most differentiated samples. In contrast, Pt appears to have been unaffected by sulfide precipitation. Microprobe data confirm that Pd entered the sulfide liquid before Re, and that Pt is not strongly chalcophile in this system. Occasional high Pt values

  6. Incorporation of seawater into mid-ocean ridge lava flows during emplacement (United States)

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


    Mid-ocean ridge (MOR) lava flows erupted at ~2000-3500 m below sea level contain large, cm- to m-sized cavities close to the upper surfaces of the flows. Within these cavities, lava drips (similar to lava stalactites found in terrestrial lava tubes) hang from the base of the upper crust. In order for these features to form, the cavities must exist as vapor-filled open space under hydrostatic pressures up to 35 MPa, and must maintain near-magmatic temperatures to attain the observed morphology of the drips. We have examined numerous lobate and sheet lava crusts from the fast-spreading East Pacific Rise in order to constrain the nature of the vapor that filled the cavities beneath these crusts, the extent of the interaction between the vapor and the liquid lava, and the impact of the vapor phase on flow emplacement. On the inner surfaces of large vesicles and cavities within the flow are mineral phases that appear to have grown at the interface between the liquid lava and vapor. These mineral phases have compositions distinct from those found in the flow interior (e.g., pure albite and forsterite), and show mineral growth habits indicative of undercooling of the lava. Preliminary thermodynamic modeling of the gas-liquid-solid interaction suggests that vapor derived from heated seawater is capable of producing the observed mineral compositions. In addition, we have found that quenched glass adjacent to analyzed vesicles can be enriched in Cl by an order of magnitude over ambient glass within the same sample suggesting that local mass exchange between the seawater and the lava has occurred. Here we present results of these analyses and accompanying thermodynamic modeling that lead us to conclude that the vapor filling the cavities is derived directly from seawater. In addition, we present numerical models investigating mechanisms for seawater incorporation and its impact on flow emplacement.

  7. Lower crustal xenoliths, Chinese Peak lava flow, central Sierra Nevada. (United States)

    Dodge, F.C.W.; Calk, L.C.; Kistler, R.W.


    This assemblage of pyroxenite, peridotite and mafic granulite xenoliths in the toe of a 10 m.y. trachybasalt flow remnant overlying late Cretaceous granitic rocks, indicates the presence of a mafic-ultramafic complex beneath this part of central California; orthopyroxenites, websterites and clinopyroxenites are dominant. A few of the xenoliths contain ovoid opaque patches that are apparently pseudomorphs after garnet and have pyralspite garnet compositions; using a garnet-orthopyroxene geobarometer, they indicate a lower crustal depth of approx 40 km. Abundant mafic granulites can be subdivided into those with Al2O3 = or 15% and showing considerable scatter on oxide variation diagrams. The high-alumina granulite xenoliths have relatively low 87Rb/86Sr but high 87Sr/86Sr, whereas the low-alumina and ultramafic xenoliths have a wide range of 87Rb/86Sr, but lower 87Sr/86Sr; the isotopic data indicate roughly the same age as that of overlying granitic plutons (approx 100 m.y.). However, the granitic rocks have initial 87Sr/86Sr ratios intermediate between those of the high-alumina and ultramafic xenoliths, suggesting that they result from the mixing of basaltic magma (represented by the ultramafic rocks) and crustal materials, with subsequent crystal fractionation.-R.A.H.

  8. Basalt features observed in outcrops, cores, borehole video imagery and geophysical logs, and basalt hydrogeologic study at the Idaho National Engineering Laboratory, Eastern Idaho

    Energy Technology Data Exchange (ETDEWEB)

    Bennecke, William M. [Boise State Univ., ID (United States)


    A study was undertaken to examine permeable zones identified in boreholes open to the underlying basalt and to describe the vertical cross flows present in the boreholes. To understand the permeable zones in the boreholes detailed descriptions and measurements of three outcrops in the Snake River Plain, three cores at the Idaho Chemical Processing Plant (ICPP) at the INEL, and over fifty borehole TV logs from the INEL were carried out. Based on the observations made on the three outcrops an idealized basalt lava flow model was generated that used a set of nomenclature that would be standard for the basalt lava flows studied. An upper vesicular zone, a sometimes absent columnar zone, central zone, and lower vesicular zone make up the basalt lava flow model. The overall distinction between the different zones are based on the vesicle shape size, vesicularity, and fractures present. The results of the studies also indicated that the basalt lava flows at the INEL are distal to medial facies pahoehoe lava flows with close fitting contacts. The most permeable zones identified in these basalts are fractured vesiculated portions of the top of the lava flow, the columnar areas, and basalt-flow contacts in order of importance. This was determined from impeller flowmeter logging at the INEL. Having this information a detailed stratigraphy of individual basalt lava flows and the corresponding permeable units were generated. From this it was concluded that groundwater flow at the ICPP prefers to travel along thin basalt lava flows or flow-units. Flow direction and velocity of intrawell flows detected by flowmeter is controlled by a nearby pumping well.

  9. Assessing uncertainties in remotely sensed lava flow emplacement - results from an indoor analog experiment (United States)

    Pick, Leonie; Zakšek, Klemen; Lombardo, Valerio; Hort, Matthias


    Infrared satellite images are an easily accessible data source for monitoring the radiant power (RP) emitted from lava flows during effusive eruptions in close to real time. Although not necessary for RP estimations, lava temperature is a crucial parameter in the determination of the flow's convected heat. In conjunction with the flow's spatial extent it assists the identification of potentially threatened areas and thereby the overall lava inundation hazard assessment. The accurate determination of the flow's size and temperature is however afflicted with uncertainty as the lava occupies only a small fraction (wire temperatures corresponding to barely glowing (experiment 1), glowing (experiment 2) and strongly glowing (experiment 3) was confirmed. The deviation of the hotspot's pixel fraction yielded by the Dual-Band method from the theoretically calculated one was found to be within the expected limits given that the hotspot is larger than about 3 % of the pixel area, a resolution boundary most remotely sensed volcanic hotspots fall below.

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

    DEFF Research Database (Denmark)

    Dierking, Wolfgang; Haack, Henning


    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...... of different morphologic types within a flow. The largest contrasts are observed at cross-polarization. The phase difference between the VV- and HH-channels may provide information about a vegetation cover on the lava. The radar signal scattered from the flows is dominated by surface scattering contributions...

  11. Lava flow hazard at Fogo Volcano, Cabo Verde, before and after the 2014-2015 eruption


    Richter, Nicole; Favalli, Massimiliano; de Zeeuw-van Dalfsen, Elske; Fornaciai, Alessandro; Silva Fernandes, Rui Manuel; Pérez, Nemesio M.; Levy, Judith; Victória, Sónia Silva; Thomas R. Walter


    Lava flow simulations help to better understand volcanic hazards and may assist emergency preparedness at active volcanoes. We demonstrate that at Fogo Volcano, Cabo Verde, such simulations can explain the 2014–2015 lava flow crisis and therefore provide a valuable base to better prepare for the next inevitable eruption. We conducted topographic mapping in the field and a satellite-based remote sensing analysis. We produced the first topographic model of the 2014&ndash...

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

    Jarboe, N.A.; Coe, R.S.; Glen, J.M.


    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 to cratonic

  13. Channel and tube flow features associated with the Twin Craters Lava Flow, Zuni-Bandera Volcanic Field, NM: Insights into similar features on Mars (United States)

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


    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

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

    Directory of Open Access Journals (Sweden)

    Ciro Del Negro


    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.

  15. The flank eruption history of Etna (1610-2006 as a constraint on lava flow hazard

    Directory of Open Access Journals (Sweden)

    Stefano Branca


    Full Text Available Data of the flank eruptions of Etna from over the last 400 years were extracted from the new geological map for the lava flow extensions and vent positions, and from the catalogs of historical eruptions for the eruption durations and lava volumes. The partially or widely hidden lava fields on the new geological map were retrieved from older geological maps. The distributions of the eruption durations and lava volumes were analyzed, with the definition of six eruptive classes for use in numerical simulations. The threshold values for the eruption durations and lava volumes were set at 45 days and at 35 × 106 m3 and 100 × 106 m3, respectively. A global analysis was performed on the whole volcano to evaluate the recurrence of the classes, and to estimate for each class the ranges, means and standard deviations of the durations, volumes and elevations of the main vent. The same analysis was repeated by subdividing the volcano into three sectors, which were defined on the basis of the distribution of the eruptive fissures over the last 15 ka. The classes have different recurrences across these various sectors, and different distributions of volumes, durations and elevations of the main vent. Finally, a lava flow resurfacing map that counts the number of lava flows on each given area of the volcano over the last 400 years was compiled and then normalized.

  16. Palaeomagnetic dating of two recent lava flows from Ceboruco volcano, western Mexico (United States)

    Böhnel, Harald; Pavón-Carrasco, Francisco Javier; Sieron, Katrin; Mahgoub, Ahmed Nasser


    Two lava flows from the Ceboruco volcano in west-central Mexico were sampled for palaeomagnetic dating. The younger one was emitted in 1870 and used to validate the method, while the older one known as Ceboruco flow is of unknown age but probably younger than ˜1005 AD and older than 1528 AD. Each flow was sampled in at least four sites, in order to unravel between site variations. For the 1870 flow, between site differences were notable and additionally post-cooling block movements were important; therefore, two sites had to be rejected. Three sites from the vent area and one at the tip of the 1870 flow provided well-constrained directions. This is also true for Ceboruco lava flow, and overall mean directions and palaeointensities were then used for palaeomagnetic dating applying the Matlab tool archaeo_dating and the global palaeosecular variation model SHA.DIF.14k. For the 1870 lava flow, the dating resulted in an age ranging between 1755 and 1871 AD (95 per cent probability level), which includes the real emplacement age. In addition, the Ceboruco lava flow was dated between 1000 and 1134 AD, which is close to the large plinian Jala eruption producing the crater of Ceboruco volcano around 1005 AD. This age is older than previously assumed and suggests an emplacement only shortly after the Jala eruption. As this lava flow is considered to be the youngest one of seven post-Jala lava flows, the age also defines a period of inactivity of Ceboruco volcano of about 730-860 yr before the historic 1870 eruption. Future volcanic hazard analysis will have to take into account this result. Our work also shows that multiple sampling of single lava flows is important to obtain a reliable mean direction. Sampling sites have to be carefully selected so that they represent un-tilted parts of the flows. We interpret this to be the case for the Ceboruco lava flow, while three of the six sites of the 1870 lava flow may have been partly or completely affected by movements after

  17. Magma discharge and lava flow field growth in the Nornahraun/Bardarbunga eruption Iceland. (United States)

    Hoskuldsson, Armann; Jónsdóttir, Ingibjörg; Riishus, Morten S.; Pedersen, Gro B. M.; Gudmundsson, Magnus T.; Thordarson, Torvaldur; Drouin, Vincent; Futurevolc IES field work Team


    Bardarbunga volcano was reactivated by an intense seismic swarm on 16/8 2014. The seismic swarm originating at the central volcano propagated north out into the associated fissure swarm during following days. As it reached the outwash plains of Jokulsa a fjollum a subaerial eruption began. Three eruptions have taken place on the outwash plane in the event, on the 29/8, 31/8 to present and on 5/9. In this presentation we discuss the second eruption that began on the 31/8 and how we do approach magma discharge parameters by combination of field observation and satellite photogrammetry. The eruption took place at the northern end of the eruptive fissure from AD 1797 and the lava was expelled out onto to relatively flat outwash plains of the glacial river Jokulsa a Fjollum thus access to eruptive products was relatively easy. It was clear from the first moments of the eruption that it had a high initial effusion rate, with lava covering the sandur plains at the rate of 25-30 m2/s. Within the first week the lava flow had covered more than 18 km2. That amounts to an average effusion rate between 195 to 280 m3/s. On the 11/9 the lava flow had grown to 25 km2, at that time effusion rate was between 140 to 247 m3/s, The lava stopped advancing and started to grow sideways and inflating. This reoccurred on the 26/9 and 12/10, with clockwise horizontal stacking of lobes to the south. From mid-November the lava growth has been controlled by tube-fed lava streams, at first generating breakouts close to the vent area and then during the last week before Christmas breaking out at the far NE end of the lava flow. As the eruption proceeded effusion rate gradually decreased and at the time of writing it is down to 9 to 76 m3/s. For assessment of areal extent of the lava field a combination of ground gps tracking and satellite photogrammetry was used. However one of the main challenges in the monitoring of the eruption was to obtain volumetric effusion rates. In the beginning of the

  18. Computer vision: automating DEM generation of active lava flows and domes from photos (United States)

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


    ón-Caulle, images of the active lava flow were taken on foot from a ridge overlooking the flow. To assess the evolution of the flow front, two DEMs were derived from collections of ~400 images taken on different days. To scale and geo-reference the data, one image sequence was accompanied by simultaneous collection of a GPS track using a consumer handheld GPS unit; no control points were used. The second survey was then scaled and georeferenced to the first, using features identifiable in both image sets, giving an RMS error of ~0.22 m. DEM comparison then allows advance rates and mechanisms to be identified, and comparisons drawn with emplacement processes of basaltic flows. In both case studies, the SfM-MVS approach allowed DEM generation when access or lack of dedicated surveying equipment and expertise prevented standard techniques from being deployed.olima dome 2011: 3D point cloud data

  19. Influence of basal slip on the propagation and cooling of lava flows (United States)

    Melnik, Oleg; Vedeneeva, Elena; Utkin, Ivan


    A thin layer approximation is used for studying of viscous gravity currents on the horizontal topography from a point source. The main difference from a self-similar solution obtained in Huppert (1982) is the account for partial slip of lava on the ground surface. We assume that the slip velocity is proportional to the tangential stress in some positive power. This condition is widely used in polymer science and for the flows on superhydrophobic surfaces. This condition is also applicable for lava flows because of a large roughness of volcanic terrains and the presence of unconsolidated material (ash, lapilli). The system of Stokes equations was reduced to a non-linear parabolic differential equation. Its solution was found both numerically and by a reduction to an ODE that describes similarity solution. In the latter case there is a dependence between lava mass growth rate and the power exponent in the friction law. It was shown that the presence of basal slip allows much faster propagation of lava flows in comparison with no-slip condition at the ground surface. Analytical solutions were proved by a good comparison with fully 2D axisymmetric finite volume simulations. Based on the velocity field obtained from a thin layer theory the heat budget of a lava flow was studied for the case of constant lava viscosity. Heat equation was solved in the lava domain with no flux condition at the bottom, radiative and convective fluxes at the free surface and the influx of a fresh magma from a point source. It was shown that due to a strong difference in the velocity profile the distribution of the temperature inside the lava flow is different in the cases of no-slip and partial slip conditions.

  20. 256 Shades of Grey: Dating young lava flows using high-resolution sidescan imagery from the Kolbeinsey Ridge (United States)

    Yeo, I. A.; Rothenbeck, M.; Devey, C. W.


    We present high-resolution (1 m) sidescan data from the slow-spreading (1.8 cm/yr) Kolbeinsey Ridge between 71°45'N and 70°30'N collected using an Edgetech 2200-MP 120 kHz sidescan sonar. Comparing the sound intensity between flat, heavily sedimented, off-axis areas and flat, brightly reflective, on-axis lava flows yields a difference of 20 - 30 dB and therefore a detection depth for basaltic lava flows of 30 - 60 cm of sediment burial at a grazing angle of 30 degrees. The single sensor does not allow for the extraction of phase bathymetry from the sidescan, however hummocks covered by the surveys were characterized by relatively flat summits (as seen in profiles extracted from the AUV depth and altitude measurements), and so summit regions could be considered comparable to flatter areas of seafloor. As volcanic hummocks are likely to be monogenetic edifices, sediment thicknesses extracted for the summits should be equivalent to those for the whole edifice. Using only flat areas also removes the problems of sediment slumping downslope. Ground truthing of actual sediment thicknesses will be carried out on cruises in November/December 2013 and September/October 2014 and will open up the potential for in-cruise estimation of the actual ages of young volcanic features covered by sidescan surveys, where good estimates of sedimentation rates are available.

  1. Post-emplacement cooling and contraction of lava flows: InSAR observations and thermal model for lava fields at Hekla volcano, Iceland (United States)

    Wittmann, Werner; Dumont, Stephanie; Lavallee, Yan; Sigmundsson, Freysteinn


    Gradual post-emplacement subsidence of lava flows has been observed at various volcanoes, e.g. Okmok volcano in Alaska, Kilauea volcano on Hawaii and Etna volcano on Sicily. In Iceland, this effect has been observed at Krafla volcano and Hekla volcano. The latter was chosen as a case study for investigating subsidence mechanisms, specifically thermal contraction. Effects like gravitational loading, clast repacking or creeping of a hot and liquid core can contribute to subsidence of emplaced lava flows, but thermal contraction is considered being a crucial effect. The extent to which it contributes to lava flow subsidence is investigated by mapping the relative movement of emplaced lava flows and flow substrate, and modeling the observed signal. The slow vegetation in Iceland is advantageous for Interferometric Synthetic Aperture Radar (InSAR) and offers great coherence over long periods after lava emplacement, expanding beyond the outlines of lava flows. Due to this reason, InSAR observations over volcanoes in Iceland have taken place for more than 20 years. By combining InSAR tracks from ERS, Envisat and Cosmo-SkyMed satellites we gain six time series with a total of 99 interferograms. Making use of the high spatial resolution, a temporal trend of vertical lava movements was investigated over a course of over 23 years over the 1991 lava flow of Hekla volcano, Iceland. From these time series, temporal trends of accumulated subsidence and subsidence velocities were determined in line of sight of the satellites. However, the deformation signal of lava fields after emplacement is vertically dominated. Subsidence on this lava field is still ongoing and subsidence rates vary from 14.8 mm/year in 1995 to about 1.0 mm/year in 2014. Fitting a simple exponential function suggests a exponential decay constant of 5.95 years. Additionally, a one-dimensional, semi-analytical model was fitted to these data. While subsidence due to phase change is calculated analytically

  2. Asthenosphere–lithosphere interactions in Western Saudi Arabia: Inferences from 3He/4He in xenoliths and lava flows from Harrat Hutaymah (United States)

    Konrad, Kevin;; Graham, David W; Thornber, Carl; Duncan, Robert A; Kent, Adam J.R.; Al-Amri, Abdulla


    Extensive volcanic fields on the western Arabian Plate have erupted intermittently over the last 30 Ma following emplacement of the Afar flood basalts in Ethiopia. In an effort to better understand the origin of this volcanism in western Saudi Arabia, we analyzed3He/4He, and He, CO2 and trace element concentrations in minerals separated from xenoliths and lava flows from Harrat Hutaymah, supplemented with reconnaissance He isotope data from several other volcanic fields (Harrat Al Birk, Harrat Al Kishb and Harrat Ithnayn). Harrat Hutaymah is young (lava flows at Hutaymah spans the He isotope range of the xenoliths. The lower 3He/4He in the anhydrous spinel lherzolites appears to be tied to remnant Proterozoic lithosphere prior to metasomatic fluid overprinting.

  3. Surface degassing and modifications to vesicle size distributions in active basalt flows (United States)

    Cashman, K.V.; Mangan, M.T.; Newman, S.


    The character of the vesicle population in lava flows includes several measurable parameters that may provide important constraints on lava flow dynamics and rheology. Interpretation of vesicle size distributions (VSDs), however, requires an understanding of vesiculation processes in feeder conduits, and of post-eruption modifications to VSDs during transport and emplacement. To this end we collected samples from active basalt flows at Kilauea Volcano: (1) near the effusive Kupaianaha vent; (2) through skylights in the approximately isothermal Wahaula and Kamoamoa tube systems transporting lava to the coast; (3) from surface breakouts at different locations along the lava tubes; and (4) from different locations in a single breakout from a lava tube 1 km from the 51 vent at Pu'u 'O'o. Near-vent samples are characterized by VSDs that show exponentially decreasing numbers of vesicles with increasing vesicle size. These size distributions suggest that nucleation and growth of bubbles were continuous during ascent in the conduit, with minor associated bubble coalescence resulting from differential bubble rise. The entire vesicle population can be attributed to shallow exsolution of H2O-dominated gases at rates consistent with those predicted by simple diffusion models. Measurements of H2O, CO2 and S in the matrix glass show that the melt equilibrated rapidly at atmospheric pressure. Down-tube samples maintain similar VSD forms but show a progressive decrease in both overall vesicularity and mean vesicle size. We attribute this change to open system, "passive" rise and escape of larger bubbles to the surface. Such gas loss from the tube system results in the output of 1.2 ?? 106 g/day SO2, an output representing an addition of approximately 1% to overall volatile budget calculations. A steady increase in bubble number density with downstream distance is best explained by continued bubble nucleation at rates of 7-8/cm3s. Rates are ???25% of those estimated from the vent

  4. Sensibility analysis of VORIS lava-flow simulations: application to Nyamulagira volcano, Democratic Republic of Congo

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    A. M. Syavulisembo


    Full Text Available Assessment and management of volcanic risk are important scientific, economic, and political issues, especially in densely populated areas threatened by volcanoes. The Virunga area in the Democratic Republic of Congo, with over 1 million inhabitants, has to cope permanently with the threat posed by the active Nyamulagira and Nyiragongo volcanoes. During the past century, Nyamulagira erupted at intervals of 1–4 years – mostly in the form of lava flows – at least 30 times. Its summit and flank eruptions lasted for periods of a few days up to more than two years, and produced lava flows sometimes reaching distances of over 20 km from the volcano, thereby affecting very large areas and having a serious impact on the region of Virunga. In order to identify a useful tool for lava flow hazard assessment at the Goma Volcano Observatory (GVO, we tested VORIS 2.0.1 (Felpeto et al., 2007, a freely available software ( based on a probabilistic model that considers topography as the main parameter controlling lava flow propagation. We tested different Digital Elevation Models (DEM – SRTM1, SRTM3, and ASTER GDEM – to analyze the sensibility of the input parameters of VORIS 2.0.1 in simulation of recent historical lava-flow for which the pre-eruption topography is known. The results obtained show that VORIS 2.0.1 is a quick, easy-to-use tool for simulating lava-flow eruptions and replicates to a high degree of accuracy the eruptions tested. In practice, these results will be used by GVO to calibrate VORIS model for lava flow path forecasting during new eruptions, hence contributing to a better volcanic crisis management.

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

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    Polona Kralj


    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.

  6. Q-LAVHA: A flexible GIS plugin to simulate lava flows (United States)

    Mossoux, Sophie; Saey, Mathijs; Bartolini, Stefania; Poppe, Sam; Canters, Frank; Kervyn, Matthieu


    Q-LavHA is a freeware plugin which simulates lava flow inundation probability from one or regularly distributed eruptive vents on a Digital Elevation Model (DEM). It combines existing probabilistic and deterministic models and proposes some improvements to calculate the probability of lava flow spatial propagation and terminal length. Spatial propagation is constrained by the probabilistic steepest slope. Corrective factors are included to allow the flow simulation to overcome small topographical obstacles and to fill pits. The terminal length of the flow simulation can be determined based on a fixed length value, a statistical length probability function or based on the thermo-rheological properties of an open-channel lava flow. The impact of model parameters, background slope and DEM resolution on the accuracy of the simulations are discussed. The user-friendly interface and the flexibility of Q-LavHA makes it a tool applicable from long-term volcanic hazard assessment to short-term hazard forecasting.

  7. Effect of Levee and Channel Structures on Long Lava Flow Emplacement: Martian Examples from THEMIS and MOLA Data (United States)

    Peitersen, M. N.; Zimbelman, J. R.; Christensen, P. R.; Bare, C.


    Long lava flows (discrete flow units with lengths exceeding 50 km) are easily identified features found on many planetary surfaces. An ongoing investigation is being conducted into the origin of these flows. Here, we limit our attention to long lava flows which show evidence of channel-like structures.

  8. Shatter Complex Formation in the Twin Craters Lava Flow, Zuni-Bandera Field, New Mexico (United States)

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


    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

  9. Eruption and emplacement dynamics of a thick trachytic lava flow of the Sancy volcano (France) (United States)

    Latutrie, Benjamin; Harris, Andrew; Médard, Etienne; Gurioli, Lucia


    A 70-m-thick, 2200-m-long (51 × 106 m3) trachytic lava flow unit underlies the Puy de Cliergue (Mt. Dore, France). Excellent exposure along a 400-m-long and 60- to 85-m-high section allows the flow interior to be accessed on two sides of a glacial valley that cuts through the unit. We completed an integrated morphological, structural, textural, and chemical analysis of the unit to gain insights into eruption and flow processes during emplacement of this thick silicic lava flow, so as to elucidate the chamber and flow dynamic processed that operate during the emplacement of such systems. The unit is characterized by an inverse chemical stratification, where there is primitive lava beneath the evolved lava. The interior is plug dominated with a thin basal shear zone overlying a thick basal breccia, with ramping affecting the entire flow thickness. To understand these characteristics, we propose an eruption model that first involves processes operating in the magma chamber whereby a primitive melt is injected into an evolved magma to create a mixed zone at the chamber base. The eruption triggered by this event first emplaced a trachytic dome, into which banded lava from the chamber base was injected. Subsequent endogenous dome growth led to flow down the shallow slope to the east on which the highly viscous (1012 Pa s) coulée was emplaced. The flow likely moved extremely slowly, being emplaced over a period of 4-10 years in a glacial manner, where a thick (>60-m) plug slid over a thin (5-m-thick) basal shear zone. Excellent exposure means that the Puy de Cliergue complex can be viewed as a case type location for understanding and defining the eruption and emplacement of thick, high-viscosity, silicic lava flow systems.

  10. The Origin of Ina: Evidence for Inflated Lava Flows on the Moon (United States)

    Garry, W. B.; Robinson, M. S.; Zimbelman, J. R.; Bleacher, J. E.; Hawke, B. R.; Crumpler, L. S.; Braden, S. E.; Sato, H.


    Ina is an enigmatic volcanic feature on the Moon known for its irregularly shaped mounds, the origin of which has been debated since the Apollo Missions. Three main units are observed on the floor of the depression (2.9 km across, lava flows. Comparison of these unusual lunar mounds and possible terrestrial analogs leads us to hypothesize that features in Ina were formed through lava flow inflation processes. While the source of the lava remains unclear, this new model suggests that as the mounds inflated, breakouts along their margins served as sources for surface flows that created the lower morphologic unit. Over time, mass wasting of both morphologic units has exposed fresh surfaces observed in the blocky unit. Ina is different than the terrestrial analogs presented in this study in that the lunar features formed within a depression, no vent sources are observed, and no cracks are observed on the mounds. However, lava flow inflation processes explain many of the morphologic relationships observed in Ina and are proposed to be analogous with inflated lava flows on Earth.

  11. Volatile abundances and oxygen isotopes in basaltic to dacitic lavas on mid-ocean ridges: The role of assimilation at spreading centers (United States)

    Wanless, V.D.; Perfit, M.R.; Ridley, W.I.; Wallace, P.J.; Grimes, Craig B.; Klein, E.M.


    Most geochemical variability in MOR basalts is consistent with low- to moderate-pressure fractional crystallization of various mantle-derived parental melts. However, our geochemical data from MOR high-silica glasses, including new volatile and oxygen isotope data, suggest that assimilation of altered crustal material plays a significant role in the petrogenesis of dacites and may be important in the formation of basaltic lavas at MOR in general. MOR high-silica andesites and dacites from diverse areas show remarkably similar major element trends, incompatible trace element enrichments, and isotopic signatures suggesting similar processes control their chemistry. In particular, very high Cl and elevated H2O concentrations and relatively light oxygen isotope ratios (~ 5.8‰ vs. expected values of ~ 6.8‰) in fresh dacite glasses can be explained by contamination of magmas from a component of ocean crust altered by hydrothermal fluids. Crystallization of silicate phases and Fe-oxides causes an increase in δ18O in residual magma, but assimilation of material initially altered at high temperatures results in lower δ18O values. The observed geochemical signatures can be explained by extreme fractional crystallization of a MOR basalt parent combined with partial melting and assimilation (AFC) of amphibole-bearing altered oceanic crust. The MOR dacitic lavas do not appear to be simply the extrusive equivalent of oceanic plagiogranites. The combination of partial melting and assimilation produces a distinct geochemical signature that includes higher incompatible trace element abundances and distinct trace element ratios relative to those observed in plagiogranites.

  12. Paleosecular Variation Study of Brunhes and Matuyama Chrons of Dated Lava Flows Obtained from West Maui, Hawaii, USA (United States)

    Lau, J. K.; Herrero-Bervera, E.; Valet, J.


    Fifteen oriented sites of basaltic lava flows from the West Maui Volcanic Series (island of Maui, Hawaii) were selected to improve the determination of the Brunhes and Matuyama time-averaged geomagnetic field between >0.6 and 1.8 and 2.6 Ma respectively. We sampled five flows from the Wailuku Volcanics (ca. 1.97+/-0.96-1.58+/-0.13 Ma), five flows from the Honolua Volcanics (ca.1.50+/-0.13 Ma) and five flows were drilled from the rejuvenated-stage Lahaina Volcanics (ca. plate motion, which has been neglected so far in most studies. The mean corrected direction is almost perfectly antipodal to the Brunhes mean direction derived from the Lahaina Volcanics and Honolulu Volcanic series (HVS) which is part of the Koolau Volcano on the island of Oahu. After applying the tectonic correction, the inclination remains several degrees larger than the inclination of the axial dipole and cannot be accounted for by a small axial quadrupole which would reverse with the dipole. The mean inclinations of other Hawaiian records (mostly younger than 1 Ma) involving long sequences of lava flows exhibit similar deviations from the GAD which are too large to be accounted for by a small axial quadrupole. Tilting of all sections is difficult to defend for so many localities and persistent secondary components have not been detected. Thus, these inclination anomalies would reflect the presence of a long-term standing component under Hawaii, but crustal magnetization linked to the volcanic edifice cannot be completely ruled out.

  13. Lava flow hazards at Mount Etna: constraints imposed by eruptive history and numerical simulations. (United States)

    Del Negro, Ciro; Cappello, Annalisa; Neri, Marco; Bilotta, Giuseppe; Hérault, Alexis; Ganci, Gaetana


    Improving lava flow hazard assessment is one of the most important and challenging fields of volcanology, and has an immediate and practical impact on society. Here, we present a methodology for the quantitative assessment of lava flow hazards based on a combination of field data, numerical simulations and probability analyses. With the extensive data available on historic eruptions of Mt. Etna, going back over 2000 years, it has been possible to construct two hazard maps, one for flank and the other for summit eruptions, allowing a quantitative analysis of the most likely future courses of lava flows. The effective use of hazard maps of Etna may help in minimizing the damage from volcanic eruptions through correct land use in densely urbanized area with a population of almost one million people. Although this study was conducted on Mt. Etna, the approach used is designed to be applicable to other volcanic areas.

  14. Quantitative reconstruction of thermal and dynamic characteristics of lava flow from surface thermal measurements (United States)

    Korotkii, Alexander; Kovtunov, Dmitry; Ismail-Zadeh, Alik; Tsepelev, Igor; Melnik, Oleg


    We study a model of lava flow to determine its thermal and dynamic characteristics from thermal measurements of the lava at its surface. Mathematically this problem is reduced to solving an inverse boundary problem. Namely, using known conditions at one part of the model boundary we determine the missing condition at the remaining part of the boundary. We develop a numerical approach to the mathematical problem in the case of steady-state flow. Assuming that the temperature and the heat flow are prescribed at the upper surface of the model domain, we determine the flow characteristics in the entire model domain using a variational (adjoint) method. We have performed computations of model examples and showed that in the case of smooth input data the lava temperature and the flow velocity can be reconstructed with a high accuracy. As expected, a noise imposed on the smooth input data results in a less accurate solution, but still acceptable below some noise level. Also we analyse the influence of optimization methods on the solution convergence rate. The proposed method for reconstruction of physical parameters of lava flows can also be applied to other problems in geophysical fluid flows.

  15. Volcanic risk: mitigation of lava flow invasion hazard through optimized barrier configuration (United States)

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


    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.

  16. A laboratory investigation into the effects of slope on lava flow morphology (United States)

    Gregg, Tracy K. P.; Fink, Jonathan H.


    In an attempt to model the effect of slope on the dynamics of lava flow emplacement, four distinct morphologies were repeatedly produced in a series of laboratory simulations where polyethylene glycol (PEG) was extruded at a constant rate beneath cold sucrose solution onto a uniform slope which could be varied from 1° through 60°. The lowest extrusion rates and slopes, and highest cooling rates, produced flows that rapidly crusted over and advanced through bulbous toes, or pillows (similar to subaerial "toey" pahoehoe flows and to submarine pillowed flows). As extrusion rate and slope increased, and cooling rate decreased, pillowed flows gave way to rifted flows (linear zones of liquid wax separated by plates of solid crust, similar to what is observed on the surface of convecting lava lakes), then to folded flows with surface crusts buckled transversely to the flow direction, and, at the highest extrusion rates and slopes, and lowest cooling rates, to leveed flows, which solidified only at their margins. A dimensionless parameter, Ψ, primarily controlled by effusion rate, cooling rate and flow viscosity, quantifies these flow types. Increasing the underlying slope up to 30° allows the liquid wax to advance further before solidifying, with an effect similar to that of increasing the effusion rate. For example, conditions that produce rifted flows on a 10° slope result in folded flows on a 30° slope. For underlying slopes of 40°, however, this trend reverses, slightly owing to increased gravitational forces relative to the strength of the solid wax. Because of its significant influence on heat advection and the disruption of a solid crust, slope must be incorporated into any quantitative attempt to correlate eruption parameters and lava flow morphologies. These experiments and subsequent scaling incorporate key physical parameters of both an extrusion and its environment, allowing their results to be used to interpret lava flow morphologies on land, on the

  17. Investigation of Layered Lunar Mare Lava flows through LROC Imagery and Terrestrial Analogs (United States)

    Needham, H.; Rumpf, M.; Sarah, F.


    High resolution images of the lunar surface have revealed layered deposits in the walls of impact craters and pit craters in the lunar maria, which are interpreted to be sequences of stacked lava flows. The goal of our research is to establish quantitative constraints and uncertainties on the thicknesses of individual flow units comprising the layered outcrops, in order to model the cooling history of lunar lava flows. The underlying motivation for this project is to identify locations hosting intercalated units of lava flows and paleoregoliths, which may preserve snapshots of the ancient solar wind and other extra-lunar particles, thereby providing potential sampling localities for future missions to the lunar surface. Our approach involves mapping layered outcrops using high-resolution imagery acquired by the Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC), with constraints on flow unit dimensions provided by Lunar Orbiter Laser Altimeter (LOLA) data. We have measured thicknesses of ~ 2 to > 20 m. However, there is considerable uncertainty in the definition of contacts between adjacent units, primarily because talus commonly obscures contacts and/or prevents lateral tracing of the flow units. In addition, flows may have thicknesses or geomorphological complexity at scales approaching the limit of resolution of the data, which hampers distinguishing one unit from another. To address these issues, we have undertaken a terrestrial analog study using World View 2 satellite imagery of layered lava sequences on Oahu, Hawaii. These data have a resolution comparable to LROC NAC images of 0.5 m. The layered lava sequences are first analyzed in ArcGIS to obtain an initial estimate of the number and thicknesses of flow units identified in the images. We next visit the outcrops in the field to perform detailed measurements of the individual units. We have discovered that the number of flow units identified in the remote sensing data is fewer compared to

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

    Directory of Open Access Journals (Sweden)

    Stefano Santini


    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.

  19. 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.


    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 heatin

  20. Magnetic properties and paleointensities as function of depth in a Hawaiian lava flow

    NARCIS (Netherlands)

    de Groot, L.V.; Dekkers, M.J.; Visscher, M.; ter Maat, G.W.


    The outcome of paleointensity experiments largely depends on the rock-magnetic properties of the samples. To assess the relation between volcanic emplacement processes and rock-magnetic properties, we sampled a vertical transect in a ∼6 m thick inflated lava flow at Hawaii, emplaced in ∼588 AD. Its

  1. Tracking lava flow emplacement on the east rift zone of Kilauea, Hawai’i with synthetic aperture radar (SAR) coherence (United States)

    Dietterich, Hannah R.; Poland, Michael P.; Schmidt, David; Cashman, Katharine V.; Sherrod, David R.; Espinosa, Arkin Tapia


    Lava flow mapping is both an essential component of volcano monitoring and a valuable tool for investigating lava flow behavior. Although maps are traditionally created through field surveys, remote sensing allows an extraordinary view of active lava flows while avoiding the difficulties of mapping on location. Synthetic aperture radar (SAR) imagery, in particular, can detect changes in a flow field by comparing two images collected at different times with SAR coherence. New lava flows radically alter the scattering properties of the surface, making the radar signal decorrelated in SAR coherence images. We describe a new technique, SAR Coherence Mapping (SCM), to map lava flows automatically from coherence images independent of look angle or satellite path. We use this approach to map lava flow emplacement during the Pu‘u ‘Ō‘ō-Kupaianaha eruption at Kīlauea, Hawai‘i. The resulting flow maps correspond well with field mapping and better resolve the internal structure of surface flows, as well as the locations of active flow paths. However, the SCM technique is only moderately successful at mapping flows that enter vegetation, which is also often decorrelated between successive SAR images. Along with measurements of planform morphology, we are able to show that the length of time a flow stays decorrelated after initial emplacement is linearly related to the flow thickness. Finally, we use interferograms obtained after flow surfaces become correlated to show that persistent decorrelation is caused by post-emplacement flow subsidence.

  2. Toothpaste lava: Characteristics and origin of a lava structural type transitional between pahoehoe and aa (United States)

    Rowland, Scott K.; Walker, George P. L.


    Toothpaste lava, an important basalt structural type which illustrates the transition from pahoehoe to aa, is particularly well displayed on the 1960 Kapoho lava of Kilauea Volcano. Its transitional features stem from a viscosity higher than that of pahoehoe and a rate of flow slower than that of aa. Viscosity can be quantified by the limited settling of olivine phenocrysts and rate of flow by field observations related to the low-angle slope on which the lava flowed. Much can be learned about the viscosity, rheologic condition, and flow velocity of lavas long after solidification by analyses of their structural characteristics, and it is possible to make at least a semiquantitative assessment of the numerical values of these parameters.

  3. Numerical experiments on the dynamics of channelised lava flows at Mount Cameroon volcano with the FLOWGO thermo-rheological model (United States)

    Wantim, M. N.; Kervyn, M.; Ernst, G. G. J.; del Marmol, M. A.; Suh, C. E.; Jacobs, P.


    As for many other effusive volcanoes, Mount Cameroon (MC) is a volcano for which only limited information exists on lava flow properties and emplacement dynamics for recent eruptions. This study provides new quantitative constraints for rheological and dynamic characteristics of lava flow effusion for the 1982 and 2000 eruptive events, used to calibrate the FLOWGO thermo-rheological model for these lava flows. The FLOWGO 1-D physical model is used to simulate down-flow evolution of the geometry and rheology of channel-contained cooling-limited lava flows. Morphometric data from historical lava flows were acquired from the field, e.g. channel geometry, levee and background slope, in order to estimate lava yield strength, velocity and effusion rate. Lava density and viscosity were also estimated from compositional data and laboratory methods. To account for uncertainty in the input rheological and geometrical data, three end-member scenarios were used to bracket the potential range in lava channel initial dimension, initial lava temperature and phenocryst content. For each of these scenarios, two crustal growth models were used: one assuming strong insulation due to lava flow surface crusting, the other a much lower crusting rate. Twelve numerical simulations were made per flow and the results were compared against the channel geometry, microlite content, yield strength and viscosity estimates from field and laboratory investigations. Best-fit models where obtained for both the 1982 and 2000 lava flows using a low rate of surface crusting, high initial temperature and low phenocryst content. Model-predicted lengths were within 5% of the actual lengths. Modelled mean effusion rates for the 1982 (52-64 m3 s- 1) and 2000 (10 m3 s- 1) flows closely matched field data derived estimations (26-68 and 9.5 m3 s- 1 respectively). FLOWGO model results are highly sensitive to initial channel dimensions, phenocryst content and the FLOWGO model is unable to reproduce the observed

  4. Communicating Science to Officials and People at Risk During a Slow-Motion Lava Flow Crisis (United States)

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


    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

  5. The importance of solid-phase distribution on the oral bioaccessibility of Ni and Cr in soils overlying Palaeogene basalt lavas, Northern Ireland. (United States)

    Cox, Siobhan F; Chelliah, Merlyn C M; McKinley, Jennifer M; Palmer, Sherry; Ofterdinger, Ulrich; Young, Michael E; Cave, Mark R; Wragg, Joanna


    Potentially toxic elements (PTEs) including nickel and chromium are often present in soils overlying basalt at concentrations above regulatory guidance values due to the presence of these elements in underlying geology. Oral bioaccessibility testing allows the risk posed by PTEs to human health to be assessed; however, bioaccessibility is controlled by factors including mineralogy, particle size, solid-phase speciation and encapsulation. X-ray diffraction was used to characterise the mineralogy of 12 soil samples overlying Palaeogene basalt lavas in Northern Ireland, and non-specific sequential extraction coupled with chemometric analysis was used to determine the distribution of elements amongst soil components in 3 of these samples. The data obtained were related to total concentration and oral bioaccessible concentration to determine whether a relationship exists between the overall concentrations of PTEs, their bioaccessibility and the soils mineralogy and geochemistry. Gastric phase bioaccessible fraction (BAF %) ranged from 0.4 to 5.4 % for chromium in soils overlying basalt and bioaccessible and total chromium concentrations are positively correlated. In contrast, the range of gastric phase BAF for nickel was greater (1.4-43.8 %), while no significant correlation was observed between bioaccessible and total nickel concentrations. However, nickel BAF was inversely correlated with total concentration. Solid-phase fractionation information showed that bioaccessible nickel was associated with calcium carbonate, aluminium oxide, iron oxide and clay-related components, while bioaccessible chromium was associated with clay-related components. This suggests that weathering significantly affects nickel bioaccessibility, but does not have the same effect on the bioaccessibility of chromium.

  6. A Self-Replication Model for Long Channelized Lava Flows on the Mars Plains (United States)

    Baloga, S. M.; Glaze, L. S.


    A model is presented for channelized lava flows emplaced by a self-replicating, levee-building process over long distances on the plains of Mars. Such flows may exhibit morphologic evidence of stagnation, overspills, and upstream breakouts. However, these processes do not inhibit the formation and persistence of a prominent central channel that can often be traced for more than 100 km. The two central assumptions of the self-replication model are (1) the flow advances at the average upstream velocity of the molten core and (2) the fraction of the lava that travels faster than the average upstream velocity forms stationary margins in the advancing distal zone to preserve the self-replication process. For an exemplary 300 km long flow north of Pavonis Mons, the model indicates that 8 m of crust must have formed during emplacement, as determined from the channel and levee dimensions. When combined with independent thermal dynamic estimates for the crustal growth rate, relatively narrow constraints are obtained for the flow rate (2250 m3 s 1), emplacement duration (600 d), and the lava viscosity of the molten interior (106 Pa s). Minor, transient overspills and breakouts increase the emplacement time by only a factor of 2. The primary difference between the prodigious channelized Martian flows and their smaller terrestrial counterparts is that high volumetric flow rates must have persisted for many hundreds of days on Mars, in contrast to a few hours or days on Earth.

  7. Inflation Features of the Distal Pahoehoe Portion of the 1859 Mauna Loa Flow, Hawaii; Implications for Evaluating Planetary Lava Flows (United States)

    Zimbelman, J. R.; Garry, W. B.; Bleacher, Jacob E.; Crumpler, L S.


    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.

  8. Propagation style controls lava-snow interactions. (United States)

    Edwards, B R; Belousov, A; Belousova, M


    Understanding interactions between volcanic eruptions and the cryosphere (a.k.a. glaciovolcanism) is important for climate reconstructions as well as for hazard mitigation at ice-clad volcanoes. Here we present unique field observations of interactions between snowpack and advancing basaltic lava flows during the 2012-13 eruption at Tolbachik volcano, Kamchatka, Russia. Our observations show that lava-snow heat transfer is slow, and that styles of lava propagation control snowpack responses. 'A'a and sheet lava flows advance in a rolling caterpillar-track motion on top of the rigid, snowpack substrate with minor lava-snow interaction. In contrast, pahoehoe lava propagates by inflation of lobes beneath/inside the snowpack, producing rigorous lava-snow interaction via meltwater percolation down into the incandescent lava causing production of voluminous steam, rapid surface cooling and thermal shock fragmentation. The textures produced by pahoehoe-snowpack interactions are distinctive and, where observed at other sites, can be used to infer syn-eruption seasonality and climatic conditions.

  9. Flood lavas on Earth, Io and Mars (United States)

    Keszthelyi, L.; Self, S.; Thordarson, T.


    Flood lavas are major geological features on all the major rocky planetary bodies. They provide important insight into the dynamics and chemistry of the interior of these bodies. On the Earth, they appear to be associated with major and mass extinction events. It is therefore not surprising that there has been significant research on flood lavas in recent years. Initial models suggested eruption durations of days and volumetric fluxes of order 107 m3 s-1 with flows moving as turbulent floods. However, our understanding of how lava flows can be emplaced under an insulating crust was revolutionized by the observations of actively inflating pahoehoe flows in Hawaii. These new ideas led to the hypothesis that flood lavas were emplaced over many years with eruption rates of the order of 104 m3 s-1. The field evidence indicates that flood lava flows in the Columbia River Basalts, Deccan Traps, Etendeka lavas, and the Kerguelen Plateau were emplaced as inflated pahoehoe sheet flows. This was reinforced by the observation of active lava flows of ??? 100 km length on Io being formed as tube-fed flow fed by moderate eruption rates (102-103 m3 s-1). More recently it has been found that some flood lavas are also emplaced in a more rapid manner. New high-resolution images from Mars revealed 'platy-ridged' flood lava flows, named after the large rafted plates and ridges formed by compression of the flow top. A search for appropriate terrestrial analogues found an excellent example in Iceland: the 1783-1784 Laki Flow Field. The brecciated Laki flow top consists of pieces of pahoehoe, not aa clinker, leading us to call this 'rubbly pahoehoe'. Similar flows have been found in the Columbia River Basalts and the Kerguelen Plateau. We hypothesize that these flows form with a thick, insulating, but mobile crust, which is disrupted when surges in the erupted flux are too large to maintain the normal pahoehoe mode of emplacement Flood lavas emplaced in this manner could have

  10. Computational modeling of lava domes using particle dynamics to investigate the effect of conduit flow mechanics on flow patterns (United States)

    Husain, Taha Murtuza

    Large (1--4 x 106 m3) to major (> 4 x 106 m3) dome collapses for andesitic lava domes such as Soufriere Hills Volcano, Montserrat are observed for elevated magma discharge rates (6--13 m3/s). The gas rich magma pulses lead to pressure build up in the lava dome that result in structural failure of the over steepened canyon-like walls which may lead to rockfall or pyroclastic flow. This indicates that dome collapse intimately related to magma extrusion rate. Variation in magma extrusion rate for open-system magma chambers is observed to follow alternating periods of high and low activity. Periodic behavior of magma exhibits a rich diversity in the nature of its eruptive history due to variation in magma chamber size, total crystal content, linear crystal growth rate and magma replenishment rate. Distinguished patterns of growth were observed at different magma flow rates ranging from endogenous to exogenous dome growth for magma with varying strengths. Determining the key parameters that control the transition in flow pattern of the magma during its lava dome building eruption is the main focus. This dissertation examines the mechanical effects on the morphology of the evolving lava dome on the extrusion of magma from a central vent using a 2D particle dynamics model. The particle dynamics model is coupled with a conduit flow model that incorporates the kinetics of crystallization and rheological stiffening to investigate important mechanisms during lava dome building eruptions. Chapter I of this dissertation explores lava dome growth and failure mechanics using a two-dimensional particle-dynamics model. The model follows the evolution of fractured lava, with solidification driven by degassing induced crystallization of magma. The particle-dynamics model emulates the natural development of dome growth and rearrangement of the lava dome which is difficult in mesh-based analyses due to mesh entanglement effects. The deformable talus evolves naturally as a frictional

  11. Application of THEMIS Data to an Investigation of a Long Lava Flow in the Tharsis Montes Region of Mars (United States)

    Zimbelman, J. R.; Peitersen, M. N.; Christensen, P. R.; Rice, J. W.


    The Tharsis region of Mars has long been known for the numerous lava flows radiating from the Tharsis Montes shield volcanoes. A 480-km-long flow southwest of Ascraeus Mons has been the subject of previous investigations using Viking and MGS data. The new data currently being obtained with the Thermal Emission Imaging System (THEMIS) on the Mars Odyssey spacecraft can shed new light on the volcanology of Martian lava flows, illustrated in this paper by two THEMIS images of the previously studied flow near Ascraeus Mons. The lava flow examined is on the western flank of the topographic saddle between the Ascraeus Mons and Pavonis Mons shield volcanoes. Flow morphology in the dust-covered Tharsis region is revealed in exquisite detail in daytime IR and VIS images from THEMIS, which will aid in documentation and analysis of lava flow features on Mars and improve constraints for volcanic modeling.

  12. Pāhoehoe, `a`ā, and block lava: an illustrated history of the nomenclature (United States)

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


    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.

  13. Eruption mechanisms and short duration of large rhyolitic lava flows of Yellowstone (United States)

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


    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

  14. Assimilation of Seawater in Basaltic Magmas: Evidence Found in a Lava Pillar From Axial Seamount, Juan de Fuca Ridge (United States)

    Schiffman, P.; Zierenberg, R.; Chadwick, W. W.; Clague, D. A.


    A lava pillar formed during the 1998 eruption at Axial Seamount exhibits compositional and textural evidence consistent with the direct assimilation of seawater under magmatic conditions. Glass immediately adjacent to anastomosing microfractures within 1 cm of the inner pillar wall is oxidized and significantly enriched in both Na and Cl (and depleted in Fe and K) with respect to that in selvages from the (unaffected) outer pillar wall. The affected glass contains up to 1 wt. % Cl and is enriched by ca. 2 wt. % Na2O relative to unaffected glass, consistent with a nearly 1:1 (molar) assimilation of NaCl. Glass not adjacent to microfractures in the inner pillar wall is depleted in Na, but enriched in K, with respect to the NaCl-enriched, inner pillar wall glass and the unaffected outer pillar wall glass. The 87Sr/86Sr ratio of the NaCl-enriched glass (ca. 0.704 +/- .001), as determined by LA ICPMS, is slightly elevated with respect to that of unaffected glass (ca. .703) consistent with the incorporation of a seawater-derived fluid. The presence of tiny (< 10 mm) grains of Cu-Fe- and Fe-sulfides as well as elemental Ni, Ag, and Au in the Na-depleted, K-enriched glass of the inner pillar wall implies significant reduction of this glass, presumably by hydrogen generated during seawater assimilation and oxidation of magma adjacent to microfractures. We interpret that the chemical anomalies we see in the glass of the interior pillar wall are caused by nearly instantaneous assimilation of seawater into the magma during pillar growth. Other lava pillars we have examined from Axial Seamount and elsewhere on the Juan de Fuca Ridge do not display similar features, although we have not examined a statistically significant number of samples to ascertain how widespread a process this is for seawater assimilation.

  15. Comparison of Natural Dams from Lava Flows and Landslides on the Owyhee River, Oregon (United States)

    Ely, L. L.; Brossy, C. C.; Othus, S. M.; Orem, C.; Fenton, C.; House, P. K.; O'Connor, J. E.; Safran, E. B.


    Numerous large lava flows and mass movements have temporarily dammed the Owyhee River in southeastern Oregon at various temporal and spatial scales. These channel-encroaching events potentially play a significant role in creating and maintaining the geomorphic features of river canyons in uplifted volcanic terranes that compose a significant part of the western U.S. Abundant landslides and lava flows have the capacity to inhibit incision by altering channel slope, width, and bed character, and burying valley- bottom bedrock under exogenous material; or promote incision by generating cataclysmic floods through natural dam failures. The natural dams vary in their source, morphology, longevity and process of removal, which in turn affects the extent and duration of their impact on the river. The 3 most recent lava flows filled the channel 10-75 m deep and flowed up to 26 kilometers downvalley, creating long, low dams that were subject to gradual, rather than catastrophic, removal. In the last 125 ka, the Saddle Butte and West Crater lava dams created reservoirs into which 10-30 meters of silt and sand were deposited. The river overtopped the dams and in most reaches eventually cut a new channel through the adjacent, less resistant bedrock buttresses. Terraces at several elevations downstream and upstream of the West Crater dam indicate periods of episodic incision ranging from 0.28 to 1.7 mm/yr., based on 3He exposure ages on strath surfaces and boulder-rich fluvial deposits. In contrast to the lava dams, outburst flood deposits associated with landslide dams are common along the river. The mechanisms of failure are related to the geologic setting, and include rotational slump complexes, cantilevered blocks and block slides, and massive earthflows. Most large-scale mass movements occur in reaches where the Owyhee canyon incises through stacks of interbedded fluviolacustrine sediments capped with lava flows. The frequently observed association of landslides and flood

  16. The eruption in Holuhraun, NE Iceland 2014-2015: Real-time monitoring and influence of landscape on lava flow (United States)

    Jónsdóttir, Ingibjörg; Höskuldsson, Ármann; Thordarson, Thor; Bartolini, Stefania; Becerril, Laura; Marti Molist, Joan; Þorvaldsson, Skúli; Björnsson, Daði; Höskuldsson, Friðrik


    The largest eruption in Iceland since the Laki 1783-84 event began in Holuhraun, NE Iceland, on 31 August 2014, producing a lava flow field which, by the end of the eruption on February 27th 2015, covered 84,5 km2 with volume of 1,44 km3. Throughout the event, various satellite images (NOAA AVHRR, MODIS, SUOMI NPP VIIRS, ASTER, LANDSAT7&8, EO-1 ALI & HYPERION, RADARSAT-2, SENTINEL-1, COSMO SKYMED, TERRASAR X) were analysed to monitor the development of activity, identify active flow fronts and channels, and map the lava extent in close collaboration with the on-site field group. Aerial photographs and radar images from the Icelandic Coast Guard Dash 8 aircraft supported this effort. By the end of 2015, Loftmyndir ehf had produced a detailed 3D model of the lava using aerial photographs from 2013 and 2015. The importance of carrying out real-time monitoring of a volcanic eruption is: i) to locate sites of elevated temperature that may be registering new areas of activity within the lava or opening of vents or fissures. ii) To establish and verify timing of events at the vents and within the lava. iii) To identify potential volcanic hazard that can be caused by lava movements, eruption-induced flash flooding, tephra fallout or gas pollution. iv) to provide up-to-date regional information to field groups concerning safety as well as to locate sites for sampling lava, tephra and polluted water. v) to produce quantitative information on magma discharge and lava flow advance, map the lava extent, document the flow morphology and plume/tephra dispersal. During the eruption, these efforts supported mapping of the extent of the lava every 3-4 days on average underpinning the time series of magma discharge calculations. Digitial elevation models from before and after the event, combined with the real-time data series, supports detailed analysis of how landscape affects lava flow in a flat terrain (<0,4°), and provides important input to further developing lava flow models

  17. Petrogenesis of Late Cretaceous lava flows from a Ceno-Tethyan island arc: The Raskoh arc, Balochistan, Pakistan (United States)

    Siddiqui, Rehanul Haq; Qasim Jan, M.; Asif Khan, M.


    The Raskoh arc is about 250 km long, 40 km wide and trends in an ENE direction. The oldest rock unit in the Raskoh arc is an accretionary complex (Early to Late Jurassic), which is followed in age by Kuchakki Volcanic Group, the most wide spread unit of the Raskoh arc. The Volcanic Group is mainly composed of basaltic to andesitic lava flows and volcaniclastics, including agglomerate, volcanic conglomerate, breccia and tuff, with subordinate shale, sandstone, limestone and chert. The flows generally form 3-15 m thick lenticular bodies but rarely reach up to 300 m. They are mainly basaltic-andesites with minor basalts and andesites. The main textures exhibited by these rocks are hypocrystalline porphyritic, subcumulophyric and intergranular. The phenocrysts comprise mainly plagioclase (An30-54 in Nok Chah and An56-64 in Bunap). They are embedded in a micro-cryptocrystalline groundmass having the same minerals. Apatite, magnetite, titanomagnetite and hematite occur as accessory minerals. Major, trace and rare earth elements suggest that the volcanics are oceanic island arc tholeiites. Their low Mg # (42-56) and higher FeO (total)/MgO (1.24-2.67) ratios indicate that the parent magma of these rocks was not directly derived from a mantle source but fractionated in an upper level magma chamber. The trace element patterns show enrichment in LILE and depletion in HFSE relative to N-MORB. Their primordial mantle-normalized trace element patterns show marked negative Nb anomalies with positive spikes on K, Ba and Sr which confirm their island arc signatures. Slightly depleted LREE to flat chondrite normalized REE patterns further support this interpretation. The Zr versus Zr/Y and Cr versus Y studies show that their parent magma was generated by 20-30% melting of a depleted mantle source. The trace elements ratios including Zr/Y (1.73-3.10), Ti/Zr (81.59-101.83), Ti/V (12.39-30.34), La/YbN (0.74-2.69), Ta/Yb (0.02-0.05) and Th/Yb (0.11-0.75) of the volcanics are more

  18. Structural and temporal requirements for geomagnetic field reversal deduced from lava flows. (United States)

    Singer, Brad S; Hoffman, Kenneth A; Coe, Robert S; Brown, Laurie L; Jicha, Brian R; Pringle, Malcolm S; Chauvin, Annick


    Reversals of the Earth's magnetic field reflect changes in the geodynamo--flow within the outer core--that generates the field. Constraining core processes or mantle properties that induce or modulate reversals requires knowing the timing and morphology of field changes that precede and accompany these reversals. But the short duration of transitional field states and fragmentary nature of even the best palaeomagnetic records make it difficult to provide a timeline for the reversal process. 40Ar/39Ar dating of lavas on Tahiti, long thought to record the primary part of the most recent 'Matuyama-Brunhes' reversal, gives an age of 795 +/- 7 kyr, indistinguishable from that of lavas in Chile and La Palma that record a transition in the Earth's magnetic field, but older than the accepted age for the reversal. Only the 'transitional' lavas on Maui and one from La Palma (dated at 776 +/- 2 kyr), agree with the astronomical age for the reversal. Here we propose that the older lavas record the onset of a geodynamo process, which only on occasion would result in polarity change. This initial instability, associated with the first of two decreases in field intensity, began approximately 18 kyr before the actual polarity switch. These data support the claim that complete reversals require a significant period for magnetic flux to escape from the solid inner core and sufficiently weaken its stabilizing effect.

  19. Petrochemistry and origin of basalt breccia from Ban Sap Sawat area, Wichian Buri, Phetchabun, central Thailand

    Directory of Open Access Journals (Sweden)

    Phisit Limtrakun


    Full Text Available Thailand is usually considered to be controlled by escape tectonics associated with India-Asia collision during theLate Cenozoic, and basaltic volcanism took place in this extensional period. This volcanism generated both subaqueous andsubaerial lava flows with tholeiitic to alkalic basaltic magma. The subaqueous eruptions represented by the studied WichianBuri basalts, Ban Sap Sawat in particular, are constituted by two main types of volcanic lithofacies, including lava flows andbasalt breccias. The lava flows are commonly porphyritic with olivine and plagioclase phenocrysts and microphenocrysts,and are uncommonly seriate textured. The basalt breccias are strongly vitrophyric texture with olivine and plagioclasephenocrysts and microphenocrysts. Chemical analyses indicate that both lava flows and basalt breccias have similar geochemical compositions, signifying that they were solidified from the same magma. Their chondrite normalized REE patternsand N-MORB normalized patterns are closely analogous to the Early to Middle Miocene tholeiites from central Sinkhote-Alinand Sakhalin, northeastern margin of the Eurasian continent which were erupted in a continental rift environment. The originfor the Wichian Buri basalts show similarity of lava flows and basalt breccias, in terms of petrography and chemical compositions, signifying that they have been formed from the same continental within-plate, transitional tholeiitic magma.

  20. Basaltic cannibalism at Thrihnukagigur volcano, Iceland (United States)

    Hudak, M. R.; Feineman, M. D.; La Femina, P. C.; Geirsson, H.


    Magmatic assimilation of felsic continental crust is a well-documented, relatively common phenomenon. The extent to which basaltic crust is assimilated by magmas, on the other hand, is not well known. Basaltic cannibalism, or the wholesale incorporation of basaltic crustal material into a basaltic magma, is thought to be uncommon because basalt requires more energy than higher silica rocks to melt. Basaltic materials that are unconsolidated, poorly crystalline, or palagonitized may be more easily ingested than fully crystallized massive basalt, thus allowing basaltic cannibalism to occur. Thrihnukagigur volcano, SW Iceland, offers a unique exposure of a buried cinder cone within its evacuated conduit, 100 m below the main vent. The unconsolidated tephra is cross-cut by a NNE-trending dike, which runs across the ceiling of this cave to a vent that produced lava and tephra during the ~4 Ka fissure eruption. Preliminary petrographic and laser ablation inductively coupled mass spectrometry (LA-ICP-MS) analyses indicate that there are two populations of plagioclase present in the system - Population One is stubby (aspect ratio 2.1), subhedral to euhedral, and has much higher Ba/Sr ratios. Population One crystals are observed in the cinder cone, dike, and surface lavas, whereas Population Two crystals are observed only in the dike and surface lavas. This suggests that a magma crystallizing a single elongate population of plagioclase intruded the cinder cone and rapidly assimilated the tephra, incorporating the stubbier population of phenocrysts. This conceptual model for basaltic cannibalism is supported by field observations of large-scale erosion upward into the tephra, which is coated by magma flow-back indicating that magma was involved in the thermal etching. While the unique exposure at Thrihnukagigur makes it an exceptional place to investigate basaltic cannibalism, we suggest that it is not limited to this volcanic system. Rather it is a process that likely

  1. Recent advances in the GPUSPH model for the thermal and rheological evolution of lava flows (United States)

    Zago, Vito; Bilotta, Giuseppe; Cappello, Annalisa; Dalrymple, Robert A.; Fortuna, Luigi; Ganci, Gaetana; Herault, Alexis; Del Negro, Ciro


    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. Because of the very high degree of parallelism, GPUSPH is implemented very efficiently on high-performance graphics processing units (GPUs) employing the Compute Unified Device Architecture (CUDA), a parallel programming language developed by NVIDIA for GPU computing. GPUSPH follows the very general Herschel-Bulkley rheological model, which encompasses Newtonian, power-law and Bingham flow behaviour and can thus be used to explore in detail the impact of rheology on the behaviour of lava flows and on their emplacement. We present here the first validation tests of the GPUSPH model against well known analytical problems, considering the different rheological models, heat exchanges by thermal conduction and radiation, and providing the relative error estimates.

  2. Lava Tube Collapse Pits (United States)


    [figure removed for brevity, see original site] We will be looking at collapse pits for the next two weeks. Collapse pits on Mars are formed in several ways. In volcanic areas, channelized lava flows can form roofs which insulate the flowing lava. These features are termed lava tubes on Earth and are common features in basaltic flows. After the lava has drained, parts of the roof of the tube will collapse under its own weight. These collapse pits will only be as deep as the bottom of the original lava tube. Another type of collapse feature associated with volcanic areas arises when very large eruptions completely evacuate the magma chamber beneath the volcano. The weight of the volcano will cause the entire edifice to subside into the void space below it. Structural features including fractures and graben will form during the subsidence. Many times collapse pits will form within the graben. In addition to volcanic collapse pits, Mars has many collapse pits formed when volatiles (such as subsurface ice) are released from the surface layers. As the volatiles leave, the weight of the surrounding rock causes collapse pits to form. These collapse pits are found in the southern hemisphere of Mars. They are likely lava tube collapse pits related to flows from Hadriaca Patera. Image information: VIS instrument. Latitude -36.8, Longitude 89.6 East (270.4 West). 19 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D

  3. 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.


    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.

  4. Evolution of the lava flow field by daily thermal and visible airborne surveys


    L. Spampinato; Calvari, S.; Harris, H; Dehn, J.


    On 28 December 2002, an effusive flank eruption started at Stromboli volcano (Aeolian Islands, 15 Italy). This lasted until 22 July 2003 and produced two lava flow fields that were emplaced onto the 16 steep slopes of Sciara del Fuoco. The first flow field was fed by a vent that opened at 500 m 17 elevation and was active between 30 December 2002 and 15 February 2003. The second was 18 supplied by a vent at 670 m and was emplaced mainly between 15 February and 22 July 2003. Here ...

  5. 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


    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

  6. High-resolution AUV mapping and lava flow ages at Axial Seamount (United States)

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


    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 (<30 cm) of the thin sediment nestled between pillow lava lobes and sieve and then hand-pick planktic foraminifera from the base of the cores to date by AMS 14C. Ages of planktic foraminifera are marine-calibrated in years before present, and provide minimum ages for the underlying flows, as there is probably some basal sediment that is not recovered. 14C ages have been determined for 10 cores near the summit of Axial Seamount and for 6 from the lowermost south rift. Ages of nearby samples commonly yield statistically identical ages, and 2 cores near the center of the caldera had multiple layers dated. These ages systematically increase with depth, indicating that redistribution of sediment by bottom currents does not significantly affect the stratigraphy. We will expand these collections in summer 2011. The coring is accompanied by collection of flow samples for chemistry and video observations to confirm contact locations and flow superposition inferred from the mapping data. 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

  7. Cerberus Fossae and Elysium Planitia Lavas, Mars: Source Vents, Flow Rates, Edifice Styles and Water Interactions (United States)

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


    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.

  8. Simulation of substrate erosion and sulphate assimilation by Martian low-viscosity lava flows: implications for the genesis of precious metal-rich sulphide mineralisation on Mars (United States)

    Baumgartner, Raphael; Baratoux, David; Gaillard, Fabrice; Fiorentini, Marco


    On Earth, high temperature mafic to ultramafic lava flows, such as komatiites and ferropicrites of the Archean and Proterozic eons, can be hosts to Ni-Cu-PGE sulphide mineralisation. Mechanical/thermo-mechanical erosion and assimilation of sulphur-rich crustal rocks is ascribed as the principal mechanism that leads to sulphide supersaturation, batch segregation and subsequent accumulation of metal-enriched magmatic sulphides (e.g., Bekker et al., Science, 2009). In order to investigate the likelihood of the occurrence of similar sulphide mineralisation in extraterrestrial magmatic systems, we numerically modelled erosion and assimilation during the turbulent emplacement of Martian lavas, some of which display chemical and rheological analogies with terrestrial komatiites and ferropicrites, on a variety of consolidated sedimentary sulphate-rich substrates. The modelling approach relies on the integration of i) mathematical lava erosion models for turbulent flows (Williams et al., J. Geophys. Res., 1998), ii) thermodynamic volatile degassing models (Gaillard et al., Space Sci. Rev., 2013), and iii) formulations on the stability of sulphides (Fortin et al., Geochim. Cosmochim. Acta, 2015). A series of scenarios are examined in which various Martian mafic to ultramafic mantle-derived melts emplace over, and assimilate consolidated sulphate-rich substrates, such as the sedimentary lithologies (i.e., conglomerates, sandstones and mudstones) recently discovered at the Gale Crater landing site. Our modellings show that lavas emplacing over consolidated sedimentary substrate rather than stiff basaltic crust, are governed by relatively high cooling and substrate erosion rates. The rapid assimilation of sulphate, which serves as a strongly oxidising agent, could result in dramatic sulphur loss due to increased volatile degassing rates at fO2 ≳QFM-1. This effect is further enhanced with increased temperature. Nevertheless, sulphide supersaturation in the way of sulphate

  9. The Role of Late-Cenozoic Lava Flows in the Evolution of the Owyhee River Canyon, Oregon (United States)

    Brossy, C. C.; House, P. K.; Ely, L. L.; O'Connor, J. E.; Safran, E. B.; Bondre, N.; Champion, D. E.; Grant, G.


    Over the last 2 Ma, at least six lava flows entered the canyon of the Owyhee River in southeastern Oregon, dramatically and repeatedly altering the river's course and profile. A combination of geochronologic, geochemical, and paleomagnetic analyses accompanied by extensive field mapping shows that these lava flows erupted from upland vents 10s of km from the river, entered the canyon via tributary or rim, and formed blockages sufficient to create lakes. Thick deltas of pillow lavas and rising passage zones in the head of the dams and subaerial lavas downstream of the dam indicate effective damming. The presence of fine grained laminated sediments deposited in the lakes suggests the dams were fairly long lived. Pending OSL dates and ongoing field study of these sediments will shed light on the nature and duration of dam construction and removal. Lava-water interaction during dam construction was extensive, and thick pillow lava deltas are common. In contrast to rivers in other locations, we did not find evidence of pyroclastics such as cinders associated with the dams. The three oldest intracanyon lava flows: the lower undivided Bogus lavas (>1.92 ± 0.22 Ma), the Bogus Rim (1.92 ± 0.22 Ma), and the Greeley Bar lavas (>780 ka), all record the filling of a wide, deep canyon, damming of the Owyhee River, and creation of extensive lakes at elevations 230 to 310 m above the modern river. The three younger lava flows, the Clarks Butte (248 ± 45 ka), the Saddle Butte (~125 ka), and the West Crater (60-90 ka), record the occurrence of similar events but in a narrower, deeper canyon similar to the modern one. Overall, this array of late Cenozoic intracanyon lava flows provides key insights into the long-term incision history of the canyon, possibly including the effect of integration with the Snake River, and supports a model of long-term, regional landscape evolution that is strongly linked to lava-water interactions.

  10. Lava Flow Mapping and Change Detection in the Mt. Etna Volcano Between 2009-2012 Using Hyperion Hyperspectral Imagery (United States)

    Karagiannopoulou, Catherine; Sykioti, Olga; Parcharidis, Issaak Briole, Pierre


    Mt. Etna is a young composite strato-volcano and one of the most active volcanoes in the world. Eruptions occur almost every year with a persistent degassing activity at the summit craters. In the last 100 years it has produced in average 107m3 of new lava per year. The main goal of our work is to detect land cover changes, including different lava flows, over the volcano that occurred between 2009 and 2012 using hyperspectral imagery (EO-1 Hyperion). For this purpose, we separated the volcano into three main land cover types: dense vegetation, urban and semi-urban areas and bare lava areas. For each area, a change detection map was produced. For the bare lava areas, two classification maps were produced based on (i) reflectance differences and (ii) chronology as proposed in bibliography. Results have shown changes in all three land cover types. In particular, for the bare lava areas, the most significant lava changes are observed in the northern and central part of the volcano, where several lava flows occurred during the 3-year study period.

  11. Movement of coliform bacteria and nutrients in ground water flowing through basalt and sand aquifers. (United States)

    Entry, J A; Farmer, N


    Large-scale deposition of animal manure can result in contamination of surface and ground water and in potential transfer of disease-causing enteric bacteria to animals or humans. We measured total coliform bacteria (TC), fecal coliform bacteria (FC), NO3, NH4, total P, and PO4 in ground water flowing from basalt and sand aquifers, in wells into basalt and sand aquifers, in irrigation water, and in river water. Samples were collected monthly for 1 yr. Total coliform and FC numbers were always higher in irrigation water than in ground water, indicating that soil and sediment filtered most of these bacteria before they entered the aquifers. Total coliform and FC numbers in ground water were generally higher in the faster flowing basalt aquifer than in the sand aquifer, indicating that the slower flow and finer grain size may filter more TC and FC bacteria from water. At least one coliform bacterium/100 mL of water was found in ground water from both basalt and sand aquifers, indicating that ground water pumped from these aquifers is not necessarily safe for human consumption according to the American Public Health Association and the USEPA. The NO3 concentrations were usually higher in water flowing from the sand aquifer than in water flowing from the basalt aquifer or in perched water tables in the basalt aquifer. The PO4 concentrations were usually higher in water flowing from the basalt aquifer than in water flowing from the sand aquifer. The main concern is fecal contamination of these aquifers and health consequences that may arise from human consumption.

  12. Emplacement dynamics and lava field evolution of the flood basalt eruption at Holuhraun, Iceland: Observations from field and remote sensing data (United States)

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


    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

  13. Emplacement mechanism of gravity flows inferred from high resolution Lidar data: The 1944 Somma Vesuvius lava flow (Italy) (United States)

    Ventura, Guido; Vilardo, Giuseppe


    A Digital Terrain Model derived from high resolution Lidar data allows the determination of the morphometric and physical parameters of a lava flow erupted from the Somma-Vesuvius volcano in 1944. The downstream variation of morphometric parameters including slope, aspect, relative relief, thickness, width, and cross sectional area is analyzed, and the changes in viscosity, velocity and flow rate are estimated. The aims of the analyses are to recognize different flow surfaces, to reconstruct the flow kinematics, and to obtain information on the mechanism of emplacement. The results indicate that the 1944 lava flow can be divided in three sectors: a near vent sector (NVS) characterized by a toe-like surface, an intermediate sector (IS) with an 'a'ātype brittle surface, and a distal sector (DS) with a sheet-like ductile surface. Lateral leveés and channels do not occur in NVS, whereas they are well developed in IS. In DS, leveés increase with an increasing distance from the vent. Fold-like surfaces occur in NVS and DS, reflecting local shortening processes due to a decrease in the slope of the substratum and overflows from the main channel. IS and DS emplaced between March 18 and 21, 1944, whereas NVS emplaced on March 19 and partly covered IS. The morphometric and physical parameters indicate that IS moved in a 'tube'-like regime, whereas DS emplaced in a 'mobile crust' regime. The IS to DS transition is marked by an increase in velocity and the flow rate, and by a decrease in thickness, width, cross sectional area, and viscosity. This transition is due to an abrupt increase in the slope of the substratum. The estimated velocity values are in good agreement with the measurements during the 1944 eruption. The analysis used here may be extended to other lava flows. Some gravity flows (debris/mud flows, floods, and avalanches) have rheological properties and shapes similar to those of lavas, and the same process-form relationships may apply to these flows. The

  14. Petrology and chemistry of the Huntzinger flow, Columbia River basalt, Washington

    Energy Technology Data Exchange (ETDEWEB)

    Ward, A.W. Jr.


    Drill core samples of basalts of the Columbia River Group from the Hanford Reservation reveal a spotted, diabasic flow of up to 60 meters in thickness. These samples and those from the flow outcropping at Wahatis Peak (Saddle Mountains, Washington) were examined in detail to document intraflow textural, mineralogical, and chemical variations, which are of importance in basalt flow correlations. Analyses were by atomic absorption, instrumental neutron activation, electron microprobe, natural gamma well logging, K-Ar age dating, X-ray fluorescence, field (portable) magnetometer, and petrographic microscope.

  15. Magnetic properties and paleointensities as function of depth in a Hawaiian lava flow (United States)

    de Groot, Lennart V.; Dekkers, Mark J.; Visscher, Martijn; ter Maat, Geertje W.


    outcome of paleointensity experiments largely depends on the rock-magnetic properties of the samples. To assess the relation between volcanic emplacement processes and rock-magnetic properties, we sampled a vertical transect in a ˜6 m thick inflated lava flow at Hawaii, emplaced in ˜588 AD. Its rock-magnetic properties vary as function of distance from the flow top; the observations can be correlated to the typical cooling rate profile for such a flow. The top and to a lesser extent the bottom parts of the flow cooled faster and reveal a composition of ˜TM60 in which the magnetic remanence is carried by fine-grained titanomagnetites, relatively rich in titanium, with associated low Curie and unblocking temperatures. The titanomagnetite in the slower cooled central part of the flow is unmixed into the magnetite and ülvospinel end-members as evidenced by scanning electron microscope observation. The remanence is carried by coarse-grained magnetite lamella (˜TM0) with high Curie and unblocking temperatures. The calibrated pseudo-Thellier results that can be accepted yield an average paleointensity of 44.1 ± 2.4 μT. This is in good agreement with the paleointensity results obtained using the thermal IZZI-Thellier technique (41.6 ± 7.4 μT) and a recently proposed record for Hawaii. We therefore suggest that the chance of obtaining a reliable paleointensity from a particular cooling unit can be increased by sampling lavas at multiple levels at different distances from the top of the flow combined with careful preliminary testing of the rock-magnetic properties.

  16. Remote characterization of dominant wavelengths of surface folds on lava flows using Lidar and Discrete Fourier Transform analyses (United States)

    Deardorff, N.; Cashman, K.


    The crust of lava flows (of all compositions) is commonly folded into arcuate ridges, bent such that the convex ridges point down flow. In theory, the geometry of flow surface folds can be used to constrain the thickness and viscosity of the folding layer (from the fold wavelength) and the compressional stress (from the fold amplitude). Crustal thickness is controlled primarily by lava composition and extent of cooling. Therefore, lavas of more evolved compositions (higher silica content) have thicker crusts, which should generate surface folds with larger wavelengths. We have determined the characteristic scale of surface folds using 1000m along-channel segments from Lidar-derived 3D Digital Terrain Models over a range of lava compositions (53-72 wt% SiO2). All profiles were analyzed by discrete Fourier transform (DFT) analysis in Matlab, used to determine the spatial scale of periodic surface features. The DFT periodograms produce 1D arrays of spectral density over a range of spatial frequencies, which describe the amplitude and spatial scale (wavelength) of lava surface topography. The DFT analysis allows for unbiased measurements of dominant surface fold wavelengths as well as identification of primary and secondary folds (i.e. folds within folds). Measurements of multiple fold generations are not possible from satellite images or in the field on intermediate to high silica blocky lavas. In our analyses, strong signals of surface periodicities were found at multiple frequencies for all lava flows, indicating multiple generations of surface folds. Additionally, mafic to intermediate lavas (65 wt% SiO2) which have a much larger range in dominant wavelength (10 - >100m). The deviation in expected dominant wavelengths for high silica flows is likely explained by effective viscosity, which is strongly influenced by lava crystallinity. Crystallization both adds solid particles to the lava, increasing the effective viscosity, and increases the silica content (and

  17. Quantifying glassy and crystalline basalt partitioning in the oceanic crust (United States)

    Moore, Rachael; Ménez, Bénédicte


    The upper layers of the oceanic crust are predominately basaltic rock, some of which hosts microbial life. Current studies of microbial life within the ocean crust mainly focus on the sedimentary rock fraction, or those organisms found within glassy basalts while the potential habitability of crystalline basalts are poorly explored. Recently, there has been recognition that microbial life develops within fractures and grain boundaries of crystalline basalts, therefore estimations of total biomass within the oceanic crust may be largely under evaluated. A deeper understanding of the bulk composition and fractionation of rocks within the oceanic crust is required before more accurate estimations of biomass can be made. To augment our understanding of glassy and crystalline basalts within the oceanic crust we created two end-member models describing basalt fractionation: a pillow basalt with massive, or sheet, flows crust and a pillow basalt with sheeted dike crust. Using known measurements of massive flow thickness, dike thickness, chilled margin thickness, pillow lava size, and pillow lava glass thickness, we have calculated the percentage of glassy versus crystalline basalts within the oceanic crust for each model. These models aid our understanding of textural fractionation within the oceanic crust, and can be applied with bioenergetics models to better constrain deep biomass estimates.

  18. Lava-flow hazard with optimized non-uniform grid of vents (United States)

    Lucà, Federica; Rongo, Rocco; Lupiano, Valeria; Iovine, Giulio


    The aim of the study is to assess the sensitivity to vents (in terms of number and distribution) of sectors affected by lava flows and of hazard values at Mount Etna. The proposed methodology relies on the application of the Cellular Automata model SCIARA, and on the adoption of an optimization algorithm for progressively integrating an initial uniform distribution of 1006 vents (1-km spaced) with 500 additional sources. Vents have iteratively been added, at steps of 50, through spatial simulated annealing, using slope roughness as weigh function. For each vent, 41 types of simulations have been executed to take into proper account the potential behaviour of the volcano, based on historical records. The performed simulations have been further processed to derive lava-flow hazard, by assigning each simulation: i) a spatial likelihood of vent opening; ii) a magnitude probability, depending on the type of eruption; and iii) a temporal probability of source activation, based on historical occurrences in the past 400 years. First results are discussed, and the influence of the number and distribution of additional vents is preliminarily investigated.

  19. Monitoring Inflation and Emplacement During the 2014-2015 Kilauea Lava Flow With an Unmanned Aerial Vehicle (United States)

    Perroy, R. L.; Turner, N.; Hon, K. A.; Rasgado, V.


    Unmanned aerial vehicles (UAVs) provide a powerful new tool for collecting high resolution on-demand spatial data over volcanic eruptions and other active geomorphic processes. These data can be used to improve hazard forecasts and emergency response efforts, and also allow users to economically and safely observe and quantify lava flow inflation and emplacement on spatially and temporally useful scales. We used a small fixed-wing UAV with a modified point-and-shoot camera to repeatedly map the active front of the 2014-2015 Kīlauea lava flow over a one-month period in late 2014, at times with a two-hour repeat interval. An additional subsequent flight was added in July, 2015. We used the imagery from these flights to generate a time-series of 5-cm resolution RGB and near-infrared orthoimagery mosaics and associated digital surface models using structure from motion. Survey-grade positional control was provided by ground control points with differential GPS. Two topographic transects were repeatedly surveyed across the flow surface, contemporaneously with UAV flights, to independently confirm topographic changes observed in the UAV-derived surface models. Vertical errors were generally 10 cm. Inside our 50 hectare study site, the flow advanced at a rate of 0.47 hectares/day during the first three weeks of observations before abruptly stalling out inflation >4 m. New outbreak areas, both on the existing flow surface and along the flow margins, were readily mapped across the study area. We detected sinuous growing inflation ridges within the flow surface that correlated with subsequent outbreaks of new lava, suggesting that repeat UAV flights can provide a means of better predicting pahoehoe lava flow behavior over flat or uneven topography. Our results show that UAVs can generate accurate and digital surface models quickly and inexpensively over rapidly changing active pahoehoe lava flows.

  20. New and revised 14C dates for Hawaiian surface lava flows: Paleomagnetic and geomagnetic implications (United States)

    Pressline, N.; Trusdell, F.A.; Gubbins, David


    Radiocarbon dates have been obtained for 30 charcoal samples corresponding to 27 surface lava flows from the Mauna Loa and Kilauea volcanoes on the Island of Hawaii. The submitted charcoal was a mixture of fresh and archived material. Preparation and analysis was undertaken at the NERC Radiocarbon Laboratory in Glasgow, Scotland, and the associated SUERC Accelerator Mass Spectrometry facility. The resulting dates range from 390 years B.P. to 12,910 years B.P. with corresponding error bars an order of magnitude smaller than previously obtained using the gas-counting method. The new and revised 14C data set can aid hazard and risk assessment on the island. The data presented here also have implications for geomagnetic modelling, which at present is limited by large dating errors. Copyright 2009 by the American Geophysical Union.

  1. High-Resolution AUV Mapping Reveals Structural Details of Submarine Inflated Lava Flows (United States)

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


    The MBARI mapping AUV D. Allan B. has now been used to map volcanic terrain at mid-ocean ridges, back-arc spreading centers, and seamounts. These include the summit caldera and upper south rift zone at Axial Volcano, the summit of Davidson Seamount, the Endeavour hydrothermal fields, the Northeast Lau Spreading Center and West Mata Volcano, and, most recently, the CoAxial, North Cleft and North Gorda historic eruption sites on the Juan de Fuca and Gorda Ridges. ROV and submersible dives at most of these sites have provided groundtruth for the textures and features revealed in the roughly 1-m resolution maps. A prominent feature in the maps from four of the sites are inflated flows that did not deflate or drain. These resemble subaerial tumuli but differ in being located on level terrain, apparently atop or very near eruptive vents instead of being in the distal portions of flows. The largest inflated flow at Axial Volcano is on the caldera floor. The main part is 500 by 300 m, and up to 30 m high, with a lobe that extends another 750 m in a sinuous path. It and two nearby, medium-sized inflated flows were first described from sidescan imagery and a submersible dive by Appelgate and Embley (Bull. Volcanol., 54, 447-458, 1992). The AUV maps show clearly the smooth, gently domed relief of the large inflated flow and its sinuous shape on the seafloor, the medium-sized nearby inflated flows, and several additional smaller ones. Particularly striking is a network of 4 to 10 m deep cracks along the crest of each inflation. The cracks occur 30 to 50 m from the margins on all sides of the wider parts of the inflated flows, and become medial cracks along the entire length of the narrow parts, which are nearly triangular in cross-section. An inflation pit 35 m in diameter has a depth equal to the surrounding lava fields. ROV Doc Ricketts dove on these flows in August 2009 and photographed the deeply cracked, uplifted, once flat-lying lineated and ropy sheet flows that form

  2. Porosity evolution, contact metamorphism, and fluid flow in the host basalts of the Skaergaard magma-hydrothermal system

    Energy Technology Data Exchange (ETDEWEB)

    Manning, C.E.


    Temporal and spatial variations in porosity during contact metamorphism of the basaltic country rocks to the Skaergaard intrusion in East Greenland resulted in a complex hydrological evolution of the metamorphic aureole. Contrasts in macroscopic porosities in different lithologies led to differences in mineralogical, bulk chemical, and oxygen isotopic alteration, and units with greater macroscopic porosities record larger fluid flux during metamorphism. Calculated Darcy velocities indicate that the horizontal component of fluid flow in the aureole was toward the intrusive contact. In the actinolite + chlorite zone time-integrated fluid flux was higher in aa units ({approximately} 300 kg cm{sup {minus}2}) than in massive units ({approximately} 130 kg cm{sup {minus}2}). Approximately equal time-integrated fluxes of respectively 4 and 5 kg cm{sup {minus}2} in aa and massive units in the pyroxene zone indicate that the volume of fluid flow in the higher grade rocks was independent of primary porosity. These results are consistent with inward fluid migration in the actinolite + chlorite zone through an open network of pores whose abundance varied as a function of primary lava morphology. At higher metamorphic grades fluid fluxes were lower and were independent of primary porosity, probably as a consequence of (1) channelization of fluids due to more extensive pore filling and (2) decreasing horizontal component of flow due to upward migration of fluids near the contact. The results of this study indicate that explicit provision for rock porosity aids interpretation of the nature of fluid flow during contact metamorphism in magma-hydrothermal systems.

  3. Field-based description of rhyolite lava flows of the Calico Hills Formation, Nevada National Security Site, Nevada (United States)

    Sweetkind, Donald S.; Bova, Shiera C.


    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.

  4. Investigating the Early Atmospheres of Earth and Mars through Rivers, Raindrops, and Lava Flows (United States)

    Som, Sanjoy M.


    twice present levels and perhaps well below present levels. To constrain this further, I re-evaluate a published paleobarometry technique using the vesicle size-distribution in simply emplaced lava flows and apply it to sea-level erupted lava flows from the 2.7 billion year old Fortescue group of Western Australia. Results from three flows suggest a range for atmospheric pressure 0.07 < Patm < 0.64 atm, which has profound consequences for our interpretation of the history of the nitrogen cycle by implying that the development of the nitrogenase enzyme necessary for nitrogen fixation happened very early on in the development of life.

  5. Tracking lava flow emplacement on the east rift zone of Kīlauea, Hawai‘i, with synthetic aperture radar coherence (United States)

    Dietterich, Hannah R.; Poland, Michael P.; Schmidt, David A.; Cashman, Katharine V.; Sherrod, David R.; Espinosa, Arkin Tapia


    Lava flow mapping is both an essential component of volcano monitoring and a valuable tool for investigating lava flow behavior. Although maps are traditionally created through field surveys, remote sensing allows an extraordinary view of active lava flows while avoiding the difficulties of mapping on location. Synthetic aperture radar (SAR) imagery, in particular, can detect changes in a flow field by comparing two images collected at different times with SAR coherence. New lava flows radically alter the scattering properties of the surface, making the radar signal decorrelated in SAR coherence images. We describe a new technique, SAR Coherence Mapping (SCM), to map lava flows automatically from coherence images independent of look angle or satellite path. We use this approach to map lava flow emplacement during the Pu`u `Ō`ō-Kupaianaha eruption at Kīlauea, Hawai`i. The resulting flow maps correspond well with field mapping and better resolve the internal structure of surface flows, as well as the locations of active flow paths. However, the SCM technique is only moderately successful at mapping flows that enter vegetation, which is also often decorrelated between successive SAR images. Along with measurements of planform morphology, we are able to show that the length of time a flow stays decorrelated after initial emplacement is linearly related to the flow thickness. Finally, we use interferograms obtained after flow surfaces become correlated to show that persistent decorrelation is caused by post-emplacement flow subsidence.

  6. Rb-Sr and Sm-Nd chronology and genealogy of mare basalts from the Sea of Tranquility (United States)

    Papanastassiou, D. A.; Depaolo, D. J.; Wasserburg, G. J.


    Rb-Sr and Sm-Nd ages of two Apollo 11 mare basalts, high-K basalt 10072 and low-K basalt 10062, are reported. Rb-Sr, Sm-Nd, and Ar-40-Ar-39 ages are in good agreement and indicate an extensive time interval for filling of the Sea of Tranquility, presumably by thin lava flows, in agreement with similar observations for the Ocean of Storms. Initial Sr and Nd isotopic compositions on Apollo 11 basalts reveal at least two parent sources producing basalts. The Sm-Nd isotopic data demonstrate that low-K and high-Ti basalts from Apollo 11 and 17 derived from distinct reservoirs, while low-Ti Apollo 15 mare basalt sources have Sm/Nd similar to the sources of Apollo 11 basalts. Groupings of mare basalt based on Ti content and on isotopic data do not coincide.

  7. Toothpaste lava from the Barren Island volcano (Andaman Sea) (United States)

    Sheth, Hetu C.; Ray, Jyotiranjan S.; Kumar, Alok; Bhutani, Rajneesh; Awasthi, Neeraj


    Toothpaste lava is a basaltic lava flow type transitional between pahoehoe and aa and has been described from Paricutin, Kilauea and Etna volcanoes. Here we describe a spectacular example of toothpaste lava, forming part of a recent (possibly 1994-95) aa flow on the active volcano of Barren Island (Andaman Sea). This flow of subalkalic basalt shows abundant squeeze-ups of viscous toothpasate lava near its entry into the sea. The squeeze-ups are sheets and slabs, up to several meters across and tens of centimeters thick, extruded from boccas. They are often prominently curved, have striated upper surfaces with close-spaced, en echelon linear ridges and grooves, broad wave-like undulations perpendicular to the striations, and sometimes, clefts. Textural, geochemical, and Sr-Nd isotopic data on the squeeze-ups and the exposed aa flow core indicate very crystal-rich, viscous, and isotopically very homogeneous lava. We envisage that a greatly reduced speed of this viscous flow at the coastline, possibly aided by a shallowing of the basal slope, led to lateral spreading of the flow, which caused tension in its upper parts. This, with continued (albeit dwindling) lava supply at the back, led to widespread tearing of the flow surface and extrusion of the squeeze-ups. The larger slabs, while extruding in a plastic condition, curved under their own weight, whereas their surfaces experienced brittle deformation, forming the en echelon grooves. The extruded, detached, and rotated sheets and slabs were carried forward for some distance atop the very slowly advancing aa core, before the flow solidified.

  8. Direct observation of a submarine volcanic eruption from a sea-floor instrument caught in a lava flow. (United States)

    Fox, C G; Chadwick, W W; Embley, R W


    Our understanding of submarine volcanic eruptions has improved substantially in the past decade owing to the recent ability to remotely detect such events and to then respond rapidly with synoptic surveys and sampling at the eruption site. But these data are necessarily limited to observations after the event. In contrast, the 1998 eruption of Axial volcano on the Juan de Fuca ridge was monitored by in situ sea-floor instruments. One of these instruments, which measured bottom pressure as a proxy for vertical deformation of the sea floor, was overrun and entrapped by the 1998 lava flow. The instrument survived-being insulated from the molten lava by the solidified crust-and was later recovered. The data serendipitously recorded by this instrument reveal the duration, character and effusion rate of a sheet flow eruption on a mid-ocean ridge, and document over three metres of lava-flow inflation and subsequent drain-back. After the brief two-hour eruption, the instrument also measured gradual subsidence of 1.4 metres over the next several days, reflecting deflation of the entire volcano summit as magma moved into the adjacent rift zone. These findings are consistent with our understanding of submarine lava effusion, as previously inferred from seafloor observations, terrestrial analogues, and laboratory simulations.

  9. Mono Lake or Laschamp geomagnetic event recorded from lava flows in Amsterdam Island (southeastern Indian Ocean)

    CERN Document Server

    Carvallo, C; Ruffet, G; Henry, B I; Poidras, T; Carvallo, Claire; Camps, Pierre; Ruffet, Gilles; Henry, Bernard; Proxy, Thierry Poidras


    We report a survey carried out on basalt flows from Amsterdam Island in order to check the presence of intermediate directions interpreted to belong to a geomagnetic field excursion within the Brunhes epoch, completing this paleomagnetic record with paleointensity determinations and radiometric dating. The directional results corroborate the findings by Watkins and Nougier (1973) : normal polarity is found for two units and an intermediate direction, with associated VGPs close to the equator, for the other two units. A notable result is that these volcanic rocks are well suited for absolute paleointensity determinations. Fifty percent of the samples yields reliable intensity values with high quality factors. An original element of this study is that we made use of the PTRM-tail test of Shcherbakova et al. (2000) to help in the interpretation of the paleointensity measurements. Doing thus, only the high temperature intervals, beyond 400 degres C, were retained to obtain the most reliable estimate of the streng...

  10. Surface exposure dating of Holocene basalt flows and cinder cones in the Kula volcanic field (western Turkey) using cosmogenic 3He and 10Be (United States)

    Heineke, Caroline; Niedermann, Samuel; Hetzel, Ralf; Akal, Cüneyt


    The Kula volcanic field is the youngest volcanic province in western Anatolia and covers an area of about 600 km2 around the town Kula (Richardson-Bunbury, 1996). Its alkali basalts formed by melting of an isotopically depleted mantle in a region of long-lived continental extension and asthenospheric upwelling (Prelevic et al., 2012). Based on morphological criteria and 40Ar/39Ar dating, four phases of Quaternary activity have been distinguished in the Kula volcanic field (Richardson-Bunbury, 1996; Westaway et al., 2006). The youngest lava flows are thought to be Holocene in age, but so far only one sample from this group was dated by 40Ar/39Ar at 7±2 ka (Westaway et al., 2006). In this study, we analysed cosmogenic 3He in olivine phenocrysts from three basalt flows and one cinder cone to resolve the Holocene history of volcanic eruptions in more detail. In addition, we applied 10Be exposure dating to two quartz-bearing xenoliths found at the surface of one flow and at the top of one cinder cone. The exposure ages fall in the range between ~500 and ~3000 years, demonstrating that the youngest volcanic activity is Late Holocene in age and therefore distinctly younger than previously envisaged. Our results show that the Late Holocene lava flows are not coeval but formed over a period of a few thousand years. We conclude that surface exposure dating of very young volcanic rocks provides a powerful alternative to 40Ar/39Ar dating. References Prelevic, D., Akal, C. Foley, S.F., Romer, R.L., Stracke, A. and van den Bogaard, P. (2012). Ultrapotassic mafic rocks as geochemical proxies for post-collisional dynamics of orogenic lithospheric mantle: the case of southwestern Anatolia, Turkey. Journal of Petrology, 53, 1019-1055. Richardson-Bunbury, J.M. (1996). The Kula Volcanic Field, western Turkey: the development of a Holocene alkali basalt province and the adjacent normal-faulting graben. Geological Magazine, 133, 275-283. Westaway, R., Guillou, H., Yurtmen, S., Beck, A

  11. In situ formation of welded tuff-like textures in the carapace of a voluminous silicic lava flow, Owyhee County, SW Idaho (United States)

    Manley, C. R.


    The Badlands rhyolite, on the Owyhee Plateau of southwestern Idaho, can be demonstrated to be a large lava flow on the basis of its geometry of large and small flow lobes, its well-exposed near-vent features, and its response to pre-existing topography. However, samples of the dense upper vitrophyre of the unit reveal a range of annealed fragmental textures, including material which closely resembles the compressed, welded glass shards which are characteristic of ignimbrites. Formation of these tuff-like textures involved processes probably common to emplacement of most silicic lava flow units. Decompression upon extrusion causes inflation of pumice at the surface of the lava flow; some of this pumice is subsequently comminuted, producing loose bubble-wall shards, bits of pumice, chips of dense glass, and fragments of phenocrysts. This debris sifts down around loose blocks and into open fractures deeper in the flow, where it can be reheated, compressed, and annealed to varying degrees. The end result is a dense vitrophyre layer (beneath the true upper, non-welded carapace breccia) which can be extremely texturally heterogeneous, with areas of flow-foliated lava occurring very near lava which in many aspects looks like welded ignimbrite, complete with flattened pumices. Identical textures in other silicic units have been cited by previous workers as evidence that those units erupted as pyroclastic flows which then underwent sufficient rheomorphism to create a flow-foliated rock which otherwise appears to be lava. The textures described herein indicate that lava flows can come to mimic rheomorphic ignimbrites, at least at scales ranging from thin sections to outcrops. Voluminous silicic units with scattered fragmental textures, but with otherwise lava-like features, are probably true effusive lava flows.

  12. Geochronological, morphometric and geochemical constraints on the Pampas Onduladas long basaltic flow (Payún Matrú Volcanic Field, Mendoza, Argentina) (United States)

    Espanon, Venera R.; Chivas, Allan R.; Phillips, David; Matchan, Erin L.; Dosseto, Anthony


    The Pampas Onduladas flow in southern Mendoza, Argentina, is one of the four longest Quaternary basaltic flows on Earth. Such flows (> 100 km) are relatively rare on Earth as they require special conditions in order to travel long distances and there are no recent analogues. Favourable conditions include: a gentle topographic slope, an insulation process to preserve the melt at high temperature, and a large volume of lava with relatively low viscosity. This study investigates the rheological and geochemical characteristics of the ~ 170 km long Pampas Onduladas flow, assessing conditions that facilitated its exceptional length. The study also reports the first geochronological results for the Pampas Onduladas flow. 40Ar/39Ar step-heating analyses of groundmass reveal an eruption age of 373 ± 10 ka (2σ), making the Pampas Onduladas flow the oldest Quaternary long flow. The methods used to assess the rheological properties include the application of several GIS tools to a digital elevation model (DEM) to determine the length, width, thickness, volume and topographic slope of the flow as well as algorithms to determine its density, viscosity and temperature. The slope of the Pampas Onduladas flow determined from the initial part of the flow on the eastern side of La Carbonilla Fracture to its end point in the province of La Pampa is 0.84% (0.29°), the steepest substrate amongst long Quaternary flows. The rheological properties, such as density viscosity and temperature from the Pampas Onduladas flow are similar to values reported for other long Quaternary flows. However, the minimum volume calculated is relatively low for its length compared with other long Quaternary flows. Therefore, the extension of the Pampas Onduladas flow was probably controlled by a steep slope, combined with an insulating mechanism, which helped in providing optimal conditions for a travel length of almost 170 km.

  13. The 2014-2015 Pāhoa lava flow crisis at Kīlauea Volcano, Hawai‘i: Disaster avoided and lessons learned (United States)

    Poland, Michael; Orr, Tim; Kauahikaua, James P.; Brantley, Steven R.; Babb, Janet; Patrick, Matthew R.; Neal, Christina; Anderson, Kyle R.; Antolik, Loren; Burgess, Matthew K.; Elias, Tamar; Fuke, Steven; Fukunaga, Pauline; Johanson, Ingrid; Kagimoto, Marian; Kamibayashi, Kevan P.; Lee, Lopaka; Miklius, Asta; Million, William; Moniz, Cyril J.; Okubo, Paul G.; Sutton, Andrew; Takahashi, T. Jane; Thelen, Weston A.; Tollett, Willam; Trusdell, Frank A.


    Lava flow crises are nothing new on the Island of Hawai‘i, where their destructive force has been demonstrated repeatedly over the past several hundred years. The 2014–2015 Pāhoa lava flow crisis, however, was unique in terms of its societal impact and volcanological characteristics. Despite low effusion rates, a long-lived lava flow whose extent reached 20 km (the longest at Kīlauea Volcano in the past several hundred years) was poised for months to impact thousands of people, although direct impacts were ultimately minor (thus far). Careful observation of the flow reaffirmed and expanded knowledge of the processes associated with pāhoehoe emplacement, including the direct correlation between summit pressurization and flow advance, the influence of existing geologic structures on flow pathways, and the possible relationship between effusion rate and flow length. Communicating uncertainty associated with lava flow hazards was a challenge throughout the crisis, but online distribution of information and direct contact with residents proved to be effective strategies for keeping the public informed and educated about flow progress and how lava flows work (including forecasting limitations). Volcanological and sociological lessons will be important for inevitable future lava flow crises in Hawai‘i and, potentially, elsewhere in the world.

  14. Climate Throughout Geologic Time Was Cooled by Sequences of Explosive Volcanic Eruptions Forming Aerosols That Reflect and Scatter Ultraviolet Solar Radiation and Warmed by Relatively Continuous Extrusion of Basaltic Lava that Depletes Ozone, Allowing More Solar Ultraviolet Radiation to Reach Earth (United States)

    Ward, P. L.


    Active volcanoes of all sizes and eruptive styles, emit chlorine and bromine gases observed to deplete ozone. Effusive, basaltic volcanic eruptions, typical in Hawaii and Iceland, extrude large lava flows, depleting ozone and causing global warming. Major explosive volcanoes also deplete ozone with the same emissions, causing winter warming, but in addition eject megatons of water and sulfur dioxide into the lower stratosphere where they form sulfuric-acid aerosols whose particles grow large enough to reflect and scatter ultraviolet sunlight, causing net global cooling for a few years. The relative amounts of explosive and effusive volcanism are determined by the configuration of tectonic plates moving around Earth's surface. Detailed studies of climate change throughout geologic history, and since 1965, are not well explained by greenhouse-gas theory, but are explained quite clearly at Ozone concentrations vary substantially by the minute and show close relationships to weather system highs and lows (as pointed out by Dobson in the 1920s), to the height of the tropopause, and to the strength and location of polar vortices and jet streams. Integrating the effects of volcanism on ozone concentrations and the effects of ozone concentrations on synoptic weather patterns should improve weather forecasting. For example, the volcano Bárðarbunga, in central Iceland, extruded 85 km2 of basaltic lava between August 29, 2014, and February 28, 2015, having a profound effect on weather. Most surprising, more than a week before the March 4 eruption of Eyjafjallajökull in 2010, substantial amounts of ozone were released in the vicinity of the volcano precisely when surface deformation showed that magma first began moving up from sills below 4 km depth. Ozone similarly appears to have been emitted 3.5 months before the Pinatubo eruption in 1991. Readily available daily maps of ozone concentrations may allow early warning of an imminent volcanic

  15. Emplacement of subaerial pahoehoe lava sheet flows into water: 1990 Kūpaianaha flow of Kilauea volcano at Kaimū Bay, Hawai`i (United States)

    Umino, Susumu; Nonaka, Miyuki; Kauahikaua, James P.


    Episode 48 of the ongoing eruption of Kilauea, Hawai`i, began in July 1986 and continuously extruded lava for the next 5.5 years from a low shield, Kūpaianaha. The flows in March 1990 headed for Kalapana and inundated the entire town under 15–25 m of lava by the end of August. As the flows advanced eastward, they entered into Kaimū Bay, replacing it with a plain of lava that extends 300 m beyond the original shoreline. The focus of our study is the period from August 1 to October 31, 1990, when the lava buried almost 406,820 m2 of the 5-m deep bay. When lava encountered the sea, it flowed along the shoreline as a narrow primary lobe up to 400 m long and 100 m wide, which in turn inflated to a thickness of 5–6 m. The flow direction of the primary lobes was controlled by the submerged delta below the lavas and by damming up lavas fed at low extrusion rates. Breakout flows through circumferential and axial inflation cracks on the inflating primary lobes formed smaller secondary lobes, burying the lows between the primary lobes and hiding their original outlines. Inflated flow lobes eventually ruptured at proximal and/or distal ends as well as mid-points between the two ends, feeding new primary lobes which were emplaced along and on the shore side of the previously inflated lobes. The flow lobes mapped with the aid of aerial photographs were correlated with daily observations of the growing flow field, and 30 primary flow lobes were dated. Excluding the two repose periods that intervened while the bay was filled, enlargement of the flow field took place at a rate of 2,440–22,640 square meters per day in the bay. Lobe thickness was estimated to be up to 11 m on the basis of cross sections of selected lobes measured using optical measurement tools, measuring tape and hand level. The total flow-lobe volume added in the bay during August 1–October 31 was approximately 3.95 million m3, giving an average supply rate of 0.86 m3/s.

  16. Geology of the Sabie River Basalt Formation in the Southern Kruger National Park

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    R.J. Sweeney


    Full Text Available The Sabie River Basalt Formation (SRBF in the central Lebombo is a virtually continuous sequence of basaltic lavas some 2 500 m thick that was erupted 200 - 179 Ma ago. Flows are dominantly pahoehoe in character and vary from 2 m to 20 m in thickness. Dolerite dykes cross-cutting the basalt sequence probably represent feeders to this considerable volcanic event. Volcanological features observed within the SRBF are described. Two chemically distinct basaltic magma types are recognised, the simultaneous eruption of which presents an intriguing geochemical problem as to their origins.

  17. Assessing the Practicality and Viability of Basalt Vesicle Paleoaltimetry in Solving Regional Tectonic Problems in the Basin and Range (United States)

    Niemi, N.; Sahagian, D.; Proussevitch, A.; Carlson, W.


    Understanding the paleoelevation history of orogens is fundamental to answering a number of significant questions about continental deformation. Most paleoaltimeters rely on proxies for measuring paleoelevation that may be affected by factors other than elevation, such as climate. The basalt vesicle paleoaltimeter avoids problems associated with such proxies by directly measuring the paleo-atmospheric pressure recorded by vesicle size-distributions in basalt lava flows. Comparison of "paleoelevation" determinations from recent lava flows with their actual modern elevations on Hawaii has demonstrated the potential of this technique. Application to a study of the evolution of Cenozoic topography in the Basin and Range has revealed some of the practical limitations to the technique. Mafic lavas in the Basin and Range are more silicic than the basalts erupted on Hawaii. As a result, typical mafic lava flows in the Basin and Range are thicker, have less well-defined flow stratigraphy, and are less well-preserved than basaltic lava flows on Hawaii. Each of these factors increases the difficulty of locating a suitable sampling site for basalt vesicle paleoaltimetry. In an attempt to ameliorate these difficulties, a number of guidelines for sampling for basalt paleoaltimetry can be applied. Where available, stacks of flows offer the best opportunity for finding preserved flow tops and bottoms. The suitability of the flow for sampling is inversely proportional to SiO2 content, where samples with SiO2 54% are unsuitable. Samples in between this range display vesicles in the field, but the vesicle sizes are near the resolution of CT scans. Paleoelevation determination from young mafic lava flows of a variety of compositions will be presented to assess the viability of this technique to a wider range of lithologies, and thus a wider range of potential tectonic problems.

  18. Studies of vesicle distribution patterns in Hawaiian lavas (United States)

    Walker, George P. L.


    Basaltic lava flows are generally vesicular, and the broader facts relating to vesicle distribution have long been established; few studies have yet been made with a view to determining how and when vesicles form in the cooling history of the lava, explaining vesicle shape and size distribution, and gaining enough understanding to employ vesicles as a geological tool. Various avenues of approach exist by which one may seek to gain a better understanding of these ubiquitous structures and make a start towards developing a general theory, and three such avenues have recently been explored. One avenue involves the study of pipe vesicles; these are a well known feature of lava flows and are narrow pipes which occur near the base of many pahoehoe flow units. Another avenue of approach is that presented by the distinctive spongy pahoehoe facies of lava that is common in distal locations on Hawaiian volcanoes. A third avenue of approach is that of the study of gas blisters in lava. Gas blisters are voids, which can be as much as tens of meters wide, where the lava split along a vesicle-rich layer and the roof up-arched by gas pressure. These three avenues are briefly discussed.

  19. Science Operations for the 2008 NASA Lunar Analog Field Test at Black Point Lava Flow, Arizona (United States)

    Garry W. D.; Horz, F.; Lofgren, G. E.; Kring, D. A.; Chapman, M. G.; Eppler, D. B.; Rice, J. W., Jr.; Nelson, J.; Gernhardt, M. L.; Walheim, R. J.


    Surface science operations on the Moon will require merging lessons from Apollo with new operation concepts that exploit the Constellation Lunar Architecture. Prototypes of lunar vehicles and robots are already under development and will change the way we conduct science operations compared to Apollo. To prepare for future surface operations on the Moon, NASA, along with several supporting agencies and institutions, conducted a high-fidelity lunar mission simulation with prototypes of the small pressurized rover (SPR) and unpressurized rover (UPR) (Fig. 1) at Black Point lava flow (Fig. 2), 40 km north of Flagstaff, Arizona from Oct. 19-31, 2008. This field test was primarily intended to evaluate and compare the surface mobility afforded by unpressurized and pressurized rovers, the latter critically depending on the innovative suit-port concept for efficient egress and ingress. The UPR vehicle transports two astronauts who remain in their EVA suits at all times, whereas the SPR concept enables astronauts to remain in a pressurized shirt-sleeve environment during long translations and while making contextual observations and enables rapid (less than or equal to 10 minutes) transfer to and from the surface via suit-ports. A team of field geologists provided realistic science scenarios for the simulations and served as crew members, field observers, and operators of a science backroom. Here, we present a description of the science team s operations and lessons learned.

  20. Paleosecular variation of directions from lava flows of the Xalapa Volcanic Field, Veracruz, Mexico (United States)

    Alva-Valdivia, Luis; Gonzalez-Rangel, Antonio; Caballero-Miranda, Cecilia; Rodriguez, Sergio; Morales, Wendy


    We collected 21 monogenetic type lava flows (316 specimens) in the Xalapa Volcanic Field, eastern part of the Mexican Volcanic Belt. Geochronological results of twelve Ar-Ar determinations range from late Pleistocene to Holocene. The ages fall into three groups, those older than 2.0 Ma, those between 0.25-0.40 Ma and those less than approximately 0.1 Ma. All the samples were demagnetized by thermal and AF treatment, showing mostly a single stable component of magnetization with unblocking temperature above 530°C and/or 40-60 mT. We calculate the mean direction (D= 359.70°, I=27.4°, k=24, 95=7.7°) and the VGP to compare and integrate with previous paleosecular variation analyses. The paleosecular variation parameter, upper and lower limit are: SF=14.6, SU=17.5 and SL=11.2, respectively. So, the VGP dispersion is consistent with the expected value of latitude-dependent variation of McFadden for the last 5My.

  1. Multiple subduction imprints in the mantle below Italy detected in a single lava flow (United States)

    Nikogosian, Igor; Ersoy, Özlem; Whitehouse, Martin; Mason, Paul R. D.; de Hoog, Jan C. M.; Wortel, Rinus; van Bergen, Manfred J.


    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.

  2. Magnetic properties and paleointensities as function of depth in a Hawai'ian lava flow (United States)

    Dekkers, M. J.; de Groot, L. V.; ter Maat, G. W.


    The outcome of paleointensity experiments largely depends on the rock-magnetic properties of the samples. To assess the relation between volcanic emplacement processes and rock-magnetic properties we sampled a vertical transect in a ~6 m thick inflated lava flow at Hawai'i, with an age of 588 (558 - 640) AD (Rubin et al., 1987, recalibrated with INTCAL.09). This profile was sampled at sixteen levels in the flow; at six of these levels up to twelve samples were taken horizontally to have sufficient sample material for paleointensity experiments. Samples from all levels were rock magnetically characterized by determining hysteresis loops and FORC (first-order-reversal-curve) diagrams, and the low-field susceptibility, all at room temperature. To test for thermochemical alteration the temperature dependence of the low-field susceptibility and magnetization was determined. Overall, rock magnetic properties appear to vary as function of distance from the top; the observations can be correlated to the typical cooling rate profile for such a flow. The solidified crust under which the flow continued to flow during emplacement is ~1.8 m thick. Its rock-magnetic properties - notably the low-field susceptibility and the coercivity ratio - are more variable than those of the inflated part underneath. FORC diagrams indicate a fair portion of very small superparamagnetic particles in the top and to a lesser extent the bottom parts of the flow. In line with their faster cooling the dominant titanomagnetite composition is ~TM60 with associated low Curie and unblocking temperatures. The titanomagnetite in the slower cooled central part of the flow is unmixed into the magnetite (~TM0) and ülvospinel end-members; the remanence has therefore high Curie and unblocking temperatures. FORC diagrams and hysteresis parameters indicate larger pseudo-single-domain particles. We performed both IZZI-Thellier and calibrated pseudo-Thellier (AGU Fall 2012 contribution GP43A-1122, submitted

  3. Flow-by-flow chemical stratigraphy and evolution of thirteen Serra Geral Group basalt flows from Vista Alegre, southernmost Brazil

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    Viter M Pinto


    Full Text Available The geochemical characterization of thirteen Serra Geral Group flows in the Vista Alegre region (RS-SC, southern Brazil, displays the homogeneous basaltic composition near 50 wt.% SiO2. Each of the five basal flows (Pitanga-type, high-Ti/Y ~600, TiO2 > 3 wt.% and eight upper flows (Paranapanema-type, medium Ti/Y ~400, TiO2 > 2 wt.% can be identified from their chemical composition; sets of flows have parallel variation in chemical composition. The flow-by-flowcorrelation in four sections shows the horizontal position of the flows in three profiles and an approximately 200-m downdrop of the Itapiranga block with respect to the Frederico Westphalen block. The world-class amethyst geode mineralization and the systematic presence of native copper in the basalts make the correlation of great geological and economic significance.A caracterização geoquímica de treze derrames do Grupo Serra Geral na região de Vista Alegre (RS e SC, sul do Brasil, exibe uma composição basáltica homogênea próxima a 50% de SiO2. Os cinco derrames basais são classificados quimicamente como tipo Pitanga (alto Ti/Y ~600 e TiO2 > 3 em peso percentual, os demais oito derrames possuem médio Ti/Y ~400 com TiO2 ~2.5 em peso percentual, sendo classificados como magma tipo Paranapanema. Cada derrame pode ser identificado através de sua composição química e correlacionado, com variação paralela entre os perfis estudados. A correlação derrame a derrame nos quatro perfis demonstra uma posição horizontal em três perfis e um rejeito vertical de aproximadamente 200 m do bloco Itapiranga em relação ao bloco Frederico Westphalen. A presença de jazidas de ametista em geodos e a sistemática ocorrência de cobre nativo nos basaltos da região tornam a correlação de grande significado geológico e econômico.

  4. The Flow of the Gibbon LAVA Element Is Facilitated by the LINE-1 Retrotransposition Machinery. (United States)

    Meyer, Thomas J; Held, Ulrike; Nevonen, Kimberly A; Klawitter, Sabine; Pirzer, Thomas; Carbone, Lucia; Schumann, Gerald G


    LINE-Alu-VNTR-Alu-like (LAVA) elements comprise a family of non-autonomous, composite, non-LTR retrotransposons specific to gibbons and may have played a role in the evolution of this lineage. A full-length LAVA element consists of portions of repeats found in most primate genomes: CT-rich, Alu-like, and VNTR regions from the SVA retrotransposon, and portions of the AluSz and L1ME5 elements. To evaluate whether the gibbon genome currently harbors functional LAVA elements capable of mobilization by the endogenous LINE-1 (L1) protein machinery and which LAVA components are important for retrotransposition, we established a trans-mobilization assay in HeLa cells. Specifically, we tested if a full-length member of the older LAVA subfamily C that was isolated from the gibbon genome and named LAVAC, or its components, can be mobilized in the presence of the human L1 protein machinery. We show that L1 proteins mobilize the LAVAC element at frequencies exceeding processed pseudogene formation and human SVAE retrotransposition by > 100-fold and ≥3-fold, respectively. We find that only the SVA-derived portions confer activity, and truncation of the 3' L1ME5 portion increases retrotransposition rates by at least 100%. Tagged de novo insertions integrated into intronic regions in cell culture, recapitulating findings in the gibbon genome. Finally, we present alternative models for the rise of the LAVA retrotransposon in the gibbon lineage.

  5. Secular variation of the Earth's magnetic field and application to paleomagnetic dating of historical lava flows in Chile (United States)

    Roperch, Pierrick; Chauvin, Annick; Lara, Luis E.; Moreno, Hugo


    The recent geomagnetic secular variation is mainly characterized by the large growth of the South Atlantic Magnetic Anomaly during the last three centuries, first documented by the geomagnetic model gufm1 (Jackson et al., 2000). We report new paleomagnetic results (directions and paleointensities) from several sites in two well dated lava flows in Chile, the 1835 AD eruption of the Osorno volcano and the 1751 AD eruption of the Llaima volcano. In addition, paleointensities were obtained on 14 samples from bricks of shelters built along the main road across the Andes from Santiago (Chile) to Mendoza (Argentina) in 1770 ± 5 AD. The results confirm the high reliability of the global geomagnetic model gufm1 for the last three centuries with a large amplitude of the secular variation in inclination (∼20°) and intensity (∼25 μT). Results from three 14C dated volcanic units in the time interval 1400-1750 AD indicate that more paleomagnetic results in well dated lava flows are necessary to improve the robustness of existing global geomagnetic models. At this stage, precise paleomagnetic or archeomagnetic dating in South America using global models should be restricted to the last 3 centuries. To illustrate the potential of paleomagnetic dating in region and time interval with very large geomagnetic secular variation, we report paleomagnetic data from several sites in historical lava flows (1700-1900 AD) from the Antuco, Llaima and Villarrica volcanoes that permit to refine the ages of the major historical effusive volcanic events.

  6. Melt migration in basalt columns driven by crystallization-induced pressure gradients. (United States)

    Mattsson, Hannes B; Caricchi, Luca; Almqvist, Bjarne S G; Caddick, Mark J; Bosshard, Sonja A; Hetényi, György; Hirt, Ann M


    The structure of columnar-jointed lava flows and intrusions has fascinated people for centuries and numerous hypotheses on the mechanisms of formation of columnar jointing have been proposed. In cross-section, weakly developed semicircular internal structures are a near ubiquitous feature of basalt columns. Here we propose a melt-migration model, driven by crystallization and a coeval specific volume decrease inside cooling and solidifying columns, which can explain the observed macroscopic features in columnar-jointed basalts. We study basalts from Hrepphólar (Iceland), combining macroscopic observations, detailed petrography, thermodynamic and rheological modelling of crystallization sequences, and Anisotropy of Magnetic Susceptibility (AMS) of late crystallizing phases (that is, titanomagnetite). These are all consistent with our proposed model, which also suggests that melt-migration features are more likely to develop in certain evolved basaltic lava flows (with early saturation of titanomagnetite), and that the redistribution of melt within individual columns can modify cooling processes.

  7. Componentry of pyroclastic fall deposits from 2008-2012 small explosive eruptions at Kilauea summit crater: insights into the dynamics of an open basaltic lava column (United States)

    Eychenne, J.; Houghton, B. F.; Swanson, D.; Orr, T. R.; Carey, R. J.


    Eruptive activity began at Kilauea volcano's summit in March 2008 after 25 years of repose, when a small explosive event opened a 35-m-wide vent on the south wall of Halema`uma`u crater, initiating an eruptive period that extends to the time of writing. The activity has been characterized by: 1) a vigorous outgassing, 2) an unevenly intense spattering of the free surface at the top of the lava column (background activity), and 3) the occurrence of small explosive events consistently triggered by conduit-wall and/or rim collapses. A daily sampling of the pyroclasts ejected from the vent has been organized by the Hawaii Volcano Observatory since 2008. The componentry analyses of samples collected prior to and following different events from 2008 to 2012 allow us to distinguish consistent classes of juvenile particles according to their vesicularity, crystallinity and morphology. The abundances of these different classes vary from background- to explosion-samples, revealing consistent contrasting degassing and fragmentation processes before the disruption of the lava free surface by the rockfalls, and during and soon after the explosive events. These results, for samples collected in 2011-2012 combined with geophysical and visual datasets, give insights into the dynamics of the lava column and particularly into the behavior of the top of the column responding to outgassing and external disruption of the free surface-equilibrium state.

  8. The Effects of Heterogeneity in Magma Water Concentration on the Development of Flow Banding and Spherulites in Rhyolitic Lava

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    Seaman, S.; Dyar, D; Marinkovic, N


    This study focuses on the origin of flow-banded rhyolites that consist of compositionally similar darker and lighter flow bands of contrasting texture and color. Infrared radiation was used to obtain Fourier transform infrared (FTIR) spectra from which water concentrations were calculated, and to map variations in water concentrations across zones of spherulites and glass from the 23 million year old Sycamore Canyon lava flow of southern Arizona. Lighter-colored, thicker flow bands consist of gray glass, fine-grained quartz, and large (1.0 to 1.5 mm) spherulites. Darker-colored, thinner flow bands consist of orange glass and smaller (0.1 to 0.2 mm) spherulites. The centers of both large and small spherulites are occupied by either (1) a quartz or sanidine crystal, (2) a granophyric intergrowth, or (3) a vesicle. Mapping of water concentration (dominantly OH- in glass and OH- and H2O in sanidine crystals) illustrates fluctuating water availability during quenching of the host melt. Textures of large spherulites in the lighter (gray) bands in some cases indicate complex quenching histories that suggest that local water concentration controlled the generation of glass versus crystals. Small spherulites in darker (orange) bands have only one generation of radiating crystal growth. Both the glass surrounding spherulites, and the crystals in the spherulites contain more water in the gray flow bands than in the orange flow bands. Flow banding in the Sycamore Canyon lava flow may have originated by the stretching of a magma that contained pre-existing zones (vesicles or proto-vesicles) of contrasting water concentration, as the magma flowed in the conduit and on the surface. Variation in the original water concentration in the alternating layers is interpreted to have resulted in differences in undercooling textures in spherulites in the lighter compared to the darker flow bands.

  9. Effect of Dissolved Organic Matter on Basalt Weathering Rates under Flow Conditions (United States)

    Dontsova, K.; Steefel, C. I.; Chorover, J. D.


    Rock weathering is an important aspect of soil formation that is tightly coupled to the progressive colonization of grain surfaces by microorganisms and plant tissue, both of which are associated with the exudation of complexing ligands and reducing equivalents that are incorporated into dissolved organic matter. As part of a larger hillslope experimental study being designed for Biosphere 2 (Oracle, AZ), we seek to determine how the presence and concentration of dissolved organic matter affects the incongruent dissolution rates of basaltic tuff. Saturated flow column experiments are being conducted using plant-derived soluble organic matter solutions of variable concentrations, and comparisons are being made to experiments conducted with malic acid, a low-molecular weight organic acid commonly exuded into the rhizosphere. Dissolved organic matter was extracted from Ponderosa Pine forest floor and was characterized for aqueous geochemical parameters (pH, EC, ion balance, DOC/TN) and also for DOC composition (UV-Vis, FTIR spectroscopy). Column effluents are being analyzed for major and trace cations, anions, silica and organic solutes. Dissolution rates of primary minerals and precipitation rates of secondary phases will be estimated by fitting the data to a numerical reactive transport model, CrunchFlow2007. At the end of the fluid flow experiment, column materials will be analyzed for biogeochemical composition to detect preferential dissolution of specific phases, the precipitation of new ones, and to monitor the associated formation of biofilms. The influence of organic solutions on weathering patterns of basalt will be discussed.

  10. Hawaii Volcanism: Lava Forms (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...

  11. The eruptive history of the Trous Blancs pit craters, La Réunion Island: The origin of a 24 km long lava flow (United States)

    Walther, Georg; Frese, Ingmar; Di Muro, Andrea; Kueppers, Ulrich; Michon, Laurent; Métrich, Nicole


    The assessment of volcanic hazards is strongly based on the past eruptive behaviour of volcanoes and its morphological parameters. Since past eruption characteristics and their frequency provide the best probabilities of such eruptions for the future, understanding the complete eruptive history of a volcano is one of the most powerful tools in assessing the potential hazards or eruptions. At Piton de la Fournaise (PdF) volcano (La Réunion, Indian Ocean), the most frequent style of activity is the effusion of lava flows, which pose the greatest hazard by invasion of inhabited areas and destruction of human property. Here we examined the eruptive history of a previously uninvestigated area, believed to be the origin of a 24 km long lava flow. The eruptions recurrence time of PdF is about one eruption every 9 months in the central caldera. Besides this central activity, eruptive vents have been built along three main rift zones cutting the edifice during the last 50 kyrs. In this study we focused on the largest rift zone of about 15 km width and 20 km length, which extends in a north westerly direction between PdF and the nearby Piton des Neiges volcanic complex. This rift zone is typified by deep seismicity (up to 30 km), emitting mostly primitive magmas, indicative of high fluid pressures (up to 5 kbar) and large volume eruptions. Our area of investigation focused on four consecutively aligned pit craters called the Trous Blancs. These have been identified [1] as the source area of one of the youngest (ca. 6 kyrs) and largest lava field, which extends for 24 km from a height of 1800m asl, passing Le Tampon and Saint Pierre city, until it reaches the coast. To gain insight into the development of this eruption and possible future similar activity, we collected new field data (including stratigraphic logs, a geological map of the area, C-14 dating and geochemical analyses of the eruptive products). Fieldwork revealed that the eruption initiated with intense

  12. The 1928 eruption of Mount Etna (Italy): Reconstructing lava flow evolution and the destruction and recovery of the town of Mascali (United States)

    Branca, Stefano; De Beni, Emanuela; Chester, David; Duncan, Angus; Lotteri, Alessandra


    Mount Etna in Sicily (Italy) shows > 2500 years of interactions between volcanic eruptions and human activity, and these are well documented in historical sources. During the last 400 years, flank eruptions have had major impacts on the urban fabric of the Etna region, especially in 1651-54, 1669, 1923 and 1928, and it is the last of these which is the focus of this paper. A detailed field and historical reconstruction of the 1928 eruption is presented which allows three themes to be discussed: the evolution of the flow field, lava volume and average magma discharge rate trend; the eruption's human impact, particularly the destruction of the town of Mascali; and the recovery of the region with re-construction of Mascali in a new location. Detailed mapping of lava flows allowed the following dimensions to be calculated: total area, 4.38 × 106 m2; maximum length, 9.4 km; volume, 52.91 ± 5.21 × 106 m3 and an average effusion rate of 38.5 m3 s-1. Time-averaged discharged rates are calculated allowing the reconstruction of their temporal variations during the course of the eruption evidencing a high maximum effusion rate of 374 m3 s- 1. These trends, in particular with regard to the Lower Fissure main phase of the eruption, are in accordance with the 'idealized discharge model' of Wadge (1981), proposed for basaltic eruptions driven by de-pressurization of magma sources, mainly through reservoir relaxation (i.e. elastic contraction of a magma body). The eruption took place when Italy was governed by Mussolini and the fascist party. The State response both, during and in the immediate aftermath of the eruption and in the years that followed during which Mascali was reconstructed, was impressive. This masked a less benign legacy, however, that can be traced for several subsequent decades of using responses to natural catastrophes to manufacture State prestige by reacting to, rather than planning for, disasters.

  13. Asthenosphere-lithosphere interactions in Western Saudi Arabia: Inferences from 3He/4He in xenoliths and lava flows from Harrat Hutaymah (United States)

    Konrad, Kevin; Graham, David W.; Thornber, Carl R.; Duncan, Robert A.; Kent, Adam J. R.; Al-Amri, Abdullah M.


    Extensive volcanic fields on the western Arabian Plate have erupted intermittently over the last 30 Ma following emplacement of the Afar flood basalts in Ethiopia. In an effort to better understand the origin of this volcanism in western Saudi Arabia, we analyzed 3He/4He, and He, CO2 and trace element concentrations in minerals separated from xenoliths and lava flows from Harrat Hutaymah, supplemented with reconnaissance He isotope data from several other volcanic fields (Harrat Al Birk, Harrat Al Kishb and Harrat Ithnayn). Harrat Hutaymah is young (< 850 ka) and the northeasternmost of the volcanic fields. There is a remarkable homogeneity of 3He/4He trapped within most xenoliths, with a weighted mean of 7.54 ± 0.03 RA (2σ, n = 20). This homogeneity occurs over at least eight different xenolith types (including spinel lherzolite, amphibole clinopyroxenite, olivine websterite, clinopyroxenite and garnet websterite), and encompasses ten different volcanic centers within an area of ~ 2500 km2. The homogeneity is caused by volatile equilibration between the xenoliths and fluids derived from their host magma, as fluid inclusions are annealed during the infiltration of vapor-saturated magmas along crystalline grain boundaries. The notable exceptions are the anhydrous spinel lherzolites, which have a lower weighted mean 3He/4He of 6.8 ± 0.3 RA (2σ, n = 2), contain lower concentrations of trapped He, and have a distinctly depleted light rare earth element signature. 3He/4He values of ~ 6.8 RA are also commonly found in spinel lherzolites from harrats Ithnayn, Al Birk, and from Zabargad Island in the Red Sea. Olivine from non-xenolith-bearing lava flows at Hutaymah spans the He isotope range of the xenoliths. The lower 3He/4He in the anhydrous spinel lherzolites appears to be tied to remnant Proterozoic lithosphere prior to metasomatic fluid overprinting. Elevated 3He/4He in the western harrats has been observed only at Rahat (up to 11.8 RA; Murcia et al., 2013), a

  14. A geomagnetic field model for the Holocene based on archaeomagnetic and lava flow data (United States)

    Pavón-Carrasco, Francisco Javier; Osete, María Luisa; Torta, Joan Miquel; De Santis, Angelo


    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

  15. Learning to Characterize Submarine Lava Flow Morphology at Seamounts and Spreading Centers using High Definition Video and Photomosaics (United States)

    Fundis, A. T.; Sautter, L. R.; Kelley, D. S.; Delaney, J. R.; Kerr-Riess, M.; Denny, A. R.; Elend, M.


    In August, 2010 the UW ENLIGHTEN ’10 expedition provided ~140 hours of seafloor HD video footage at Axial Seamount, the most magmatically robust submarine volcano on the Juan de Fuca Ridge. During this expedition, direct imagery from an Insite Pacific HD camera mounted on the ROV Jason 2 was used to classify broad expanses of seafloor where high power (8 kw) and high bandwidth (10 Gb/s) fiber optic cable will be laid as part of the Regional Scale Nodes (RSN) component of the NSF funded Ocean Observatories Initiative. The cable will provide power and two-way, real-time communication to an array of >20 sensors deployed at the summit of the volcano and at active sites of hydrothermal venting to investigate how active processes within the volcano and at seafloor hot springs within the caldera are connected. In addition to HD imagery, over 10,000 overlapping photographs from a down-looking still camera were merged and co-registered to create high resolution photomosaics of two areas within Axial’s caldera. Thousands of additional images were taken to characterize the seafloor along proposed cable routes, allowing optimal routes to be planned well in advance of deployment. Lowest risk areas included those free of large collapse basins, steep flow fronts and fissures. Characterizing the modes of lava distribution across the seafloor is crucial to understanding the construction history of the upper oceanic crust at mid-ocean ridges. In part, reconstruction of crustal development and eruptive histories can be inferred from surface flow morphologies, which provide insights into lava emplacement dynamics and effusion rates of past eruptions. An online resource is under development that will educate students about lava flow morphologies through the use of HD video and still photographs. The objective of the LavaFlow exercise is to map out a proposed cable route across the Axial Seamount caldera. Students are first trained in appropriate terminology and background content

  16. Rapid ascent and emplacement of basaltic lava during the 2005-06 eruption of the East Pacific Rise at ca. 9°51‧N as inferred from CO2 contents (United States)

    Gardner, J. E.; Jackson, B. A.; Gonnermann, H.; Soule, S. A.


    Eruption rates at the mid-ocean ridges (MORs) are believed to strongly control the morphology and length of lava flows emplaced along the ridge axis, and thus the structure and porosity of the upper oceanic crust. Eruption rate also represents one of the few tools to gain insight into the driving pressures within sub-ridge magmatic systems. As eruption rate is inferred to vary systematically along the global mid-ocean ridge system, understanding of how to assess eruption rate in submarine systems and how it maps to observable features of the ridge axis would provide a powerful tool to understand Earth's largest magmatic system. Eruption rates at MORs are poorly constrained, however, because of a lack of direct observations, preventing the duration of an eruption to be quantified. This study uses decompression experiments of MORB samples and numerical modeling of CO2 degassing to reconstruct the timescales for magma ascent and lava emplacement during the 2005-06 eruption of the East Pacific Rise at ca. 9°51‧N. Samples collected from the lava flow are all supersaturated in dissolved CO2 contents, but CO2 decreases with distance from the vent, presumably as a consequence of progressive CO2 diffusion into growing bubbles. Samples collected at the vent contain ∼105 vesicles per cm3. Pieces of these samples were experimentally heated to 1225 °C at high pressure and then decompressed at controlled rates. Results, plus those from numerical modeling of diffusive bubble growth, indicate that magma rose from the axial magma chamber to the seafloor in ≤1 h and at a rate of ≥2-3 km h-1. Our modeling, as validated by experimental decompression of MORB samples with ∼106 vesicles cm-3, also suggests that CO2 degassed from the melt within ∼10-100 min as the vesicular lava traveled ∼1.7 km along the seafloor, implying a volumetric flow rate on order of 103-4 m3 s-1. Given an ascent rate of ≥0.2 m s-1, the width of a rectangular dike feeding the lava would have been

  17. 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


    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.

  18. A Sinuous Tumulus over an Active Lava Tube at Klauea Volcano: Evolution, Analogs, and Hazard Forecasts (United States)

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


    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.

  19. Simulation of Cooling and Pressure Effects on Inflated Pahoehoe Lava Flows (United States)

    Glaze, Lori S.; Baloga, Stephen M.


    Pahoehoe lobes are often emplaced by the advance of discrete toes accompanied by inflation of the lobe surface. Many random effects complicate modeling lobe emplacement, such as the location and orientation of toe breakouts, their dimensions, mechanical strength of the crust, micro-topography and a host of other factors. Models that treat the movement of lava parcels as a random walk have explained some of the overall features of emplacement. However, cooling of the surface and internal pressurization of the fluid interior has not been modeled. This work reports lobe simulations that explicitly incorporate 1) cooling of surface lava parcels, 2) the propensity of breakouts to occur at warmer margins that are mechanically weaker than cooler ones, and 3) the influence of internal pressurization associated with inflation. The surface temperature is interpreted as a surrogate for the mechanic strength of the crust at each location and is used to determine the probability of a lava parcel transfer from that location. When only surface temperature is considered, the morphology and dimensions of simulated lobes are indistinguishable from equiprobable simulations. However, inflation within a lobe transmits pressure to all connected fluid locations with the warmer margins being most susceptible to breakouts and expansion. Simulations accounting for internal pressurization feature morphologies and dimensions that are dramatically different from the equiprobable and temperature-dependent models. Even on flat subsurfaces the pressure-dependent model produces elongate lobes with distinct directionality. Observables such as topographic profiles, aspect ratios, and maximum extents should be readily distinguishable in the field.

  20. Diffuse flow environments within basalt- and sediment-based hydrothermal vent ecosystems harbor specialized microbial communities. (United States)

    Campbell, Barbara J; Polson, Shawn W; Zeigler Allen, Lisa; Williamson, Shannon J; Lee, Charles K; Wommack, K Eric; Cary, S Craig


    Hydrothermal vents differ both in surface input and subsurface geochemistry. The effects of these differences on their microbial communities are not clear. Here, we investigated both alpha and beta diversity of diffuse flow-associated microbial communities emanating from vents at a basalt-based hydrothermal system along the East Pacific Rise (EPR) and a sediment-based hydrothermal system, Guaymas Basin. Both Bacteria and Archaea were targeted using high throughput 16S rRNA gene pyrosequencing analyses. A unique aspect of this study was the use of a universal set of 16S rRNA gene primers to characterize total and diffuse flow-specific microbial communities from varied deep-sea hydrothermal environments. Both surrounding seawater and diffuse flow water samples contained large numbers of Marine Group I (MGI) Thaumarchaea and Gammaproteobacteria taxa previously observed in deep-sea systems. However, these taxa were geographically distinct and segregated according to type of spreading center. Diffuse flow microbial community profiles were highly differentiated. In particular, EPR dominant diffuse flow taxa were most closely associated with chemolithoautotrophs, and off axis water was dominated by heterotrophic-related taxa, whereas the opposite was true for Guaymas Basin. The diversity and richness of diffuse flow-specific microbial communities were strongly correlated to the relative abundance of Epsilonproteobacteria, proximity to macrofauna, and hydrothermal system type. Archaeal diversity was higher than or equivalent to bacterial diversity in about one third of the samples. Most diffuse flow-specific communities were dominated by OTUs associated with Epsilonproteobacteria, but many of the Guaymas Basin diffuse flow samples were dominated by either OTUs within the Planctomycetes or hyperthermophilic Archaea. This study emphasizes the unique microbial communities associated with geochemically and geographically distinct hydrothermal diffuse flow environments.

  1. The internal structure of lava flows—insights from AMS measurements II: Hawaiian pahoehoe, toothpaste lava and 'a'ā (United States)

    Cañón-Tapia, Edgardo; Walker, George P. L.; Herrero-Bervera, Emilio


    We studied the anisotropy of magnetic susceptibility (AMS) of 22 basaltic flow units, including S-type pahoehoe, P-type pahoehoe, toothpaste lava and 'a'ā emplaced over different slopes in two Hawaiian islands. Systematic differences occur in several aspects of AMS (mean susceptibility, degree of anisotropy, magnetic fabric and orientation of the principal susceptibilities) among the morphological types that can be related to different modes of lava emplacement. AMS also detects systematic changes in the rate of shear with position in a unit, allowing us to infer local flow direction and some other aspects of the velocity field of each unit. 'A'ā flows are subject to stronger deformation than pahoehoe, and also their internal parts behave more like a unit. According to AMS, the central part of pahoehoe commonly reveals a different deformation history than the upper and lower extremes, probably resulting from endogenous growth.

  2. Groundmass Crystallinities of Proximal and Distal Lavas from Cinder Cone, Lassen Volcanic Field (United States)

    Szymanski, M. E.; Teasdale, R.


    Cinder Cone is located in the northeast corner of Lassen Volcanic Center, approximately 35 km southeast of Old Station, California. The area consists of a cinder cone constructed of loose scoria, lava flows and a 13-16 km diameter ash deposit. According to radiocarbon ages from trees affected by the lava flows and paleomagnetic data, Cinder Cone erupted in about 1650 AD (1). The youngest products of the Cinder Cone eruption are two Fantastic Lava Beds flows which are basaltic andesite and andesite with olivine (1). Samples were collected along the longest flow from Cinder Cone, the Fantastic Lava Beds Flow 2 (4.5 km) at approximately 0.5 km interval. The samples contain olivine, plagioclase and clinopyroxene phenocrysts in fine grained groundmass with varying vesicularity. Quartz xenocrysts also occur. SEM-Back Scatter Electron images are used to map and quantify groundmass crystallinities along the length of the Fantastic Lava Beds flow 2 and of tephra units. The average area of groundmass plagioclase crystals increases along the length of the lava flow from 94.7 to 292.6 μm2. The number of groundmass plagioclase crystals per area (μm2) decreases from 0.0045 to 0.0018 from proximal to distal samples. Crystals also become blockier in distal samples along the lava flow. The larger number of crystals per area in near vent samples establishes a baseline from which we interpret crystal growth and nucleation to have occurred in the flow channel. Increasing crystal size and a decrease in the number of crystals per area indicates growth dominated nucleation during cooling and crystallization in the flow channel. Relative cooling rates along the length of the flow from proximal to distal samples can be inferred based on groundmass crystallinities, distance travelled and estimates of flow and crystallization rates. (1) Muffler and Clynne, 2015.

  3. Permeameter studies of water flow through cement and clay borehole seals in granite, basalt and tuff

    Energy Technology Data Exchange (ETDEWEB)

    South, D.L.; Daemen, J.J.K.


    Boreholes near a repository must be sealed to prevent rapid migration of radionuclide-contaminated water to the accessible environment. The objective of this research is to assess the performance of borehole seals under laboratory conditions, particularly with regard to varying stress fields. Flow through a sealed borehole is compared with flow through intact rock. Cement or bentonite seals have been tested in granite, basalt, and welded tuff. The main conclusion is that under laboratory conditions, existing commercial materials can form high quality seals. Triaxial stress changes about a borehole do not significantly affect seal performance if the rock is stiffer than the seal. Temperature but especially moisture variations (drying) significantly degrade the quality of cement seals. Performance partially recovers upon resaturation. A skillfully sealed borehole may be as impermeable as the host rock. Analysis of the influence of relative seal-rock permeabilities shows that a plug with permeability one order of magnitude greater than that of the rock results in a flow increase through the hole and surrounding rock of only 1-1/2 times compared to the undisturbed rock. Since a borehole is only a small part of the total rock mass, the total effect is even less pronounced. The simplest and most effective way to decrease flow through a rock-seal system is to increase the seal length, assuming it can be guaranteed that no dominant by-pass flowpath through the rock exists.

  4. Bringing the Volcano to the Students: The Syracuse University LAVA Project (United States)

    Karson, J.; Wysocki, B.; Kissane, M. T.


    A collaborative effort between the Department of Earth Sciences and Sculpture Department at Syracuse University has resulted in the facility to make natural-scale lava flows in a laboratory environment for K-university students and the general public. Using a large, gas-fired, furnace with a tilting crucible, basaltic gravel is heated at temperatures of 1100° to 1300°C resulting in up to 800 lbs of homogeneous, basaltic lava. Lava is poured over a variety of surfaces including rock slab, wet or dry sand, ice and dry ice. A ceramic funnel permits pouring into and under water. Differing set-ups provide analogs for a wide range of terrestrial, marine, and extraterrestrial lava flows. Composition is held constant, but varying key parameters such as temperature, pouring (effusion) rate, and slope result in different flow morphologies including ropey to toey pahoehoe, inflated flows, channelized flows with levees, and hyaloclastites. Typical flows are 2-4 m long and blast of heat. Grabbing student attention in this environment opens the door to discussions ranging from the nature of Earth materials (solid vs. liquid, rock vs glass, viscous vs brittle, etc.) to major planetary processes.

  5. Cosmic ray exposure dating with in situ produced cosmogenic 3He: results from young Hawaiian lava flows (United States)

    Kurz, M.D.; Colodner, D.; Trull, T.W.; Moore, R.B.; O'Brien, K.


    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

  6. Utility of Lava Tubes on Other Worlds (United States)

    Walden, Bryce E.; Billings, T. L.; York, Cheryl Lynn; Gillett, S. L.; Herbert, M. V.


    On Mars, as on Earth, lava tubes are found in the extensive lava fields associated with shield volcanism. Lunar lava-tube traces are located near mare-highland boundaries, giving access to a variety of minerals and other resources, including steep slopes, prominent heights for local area communications and observation, large-surface areas in shade, and abundant basalt plains suitable for landing sites, mass-drivers, surface transportation, regolith harvesting, and other uses. Methods for detecting lava tubes include visual observations of collapse trenches and skylights, ground-penetrating radar, gravimetry, magnetometry, seismography, atmospheric effects, laser, lidar, infrared, and human or robotic exploration.

  7. A Thorium-rich Mare Basalt Rock Fragment from the Apollo 12 Regolith: A Sample from a Young Procellarum Flow? (United States)

    Jolliff, B. L.; Zeigler, R. A.; Korotev, R. L.; Barra, F.; Swindle, T. D.


    In this abstract, we report on the composition, mineralogy and petrography of a basaltic rock fragment, 12032,366-18, found in the Apollo 12 regolith. Age data, collected as part of an investigation by Barra et al., will be presented in detail in. Here, only the age dating result is summarized. This rock fragment garnered our attention because it is significantly enriched in incompatible elements, e.g., 7 ppm thorium, compared to other known lunar basalts. Its mineral- and trace-element chemistry set it apart from other Apollo 12 basalts and indeed from all Apollo and Luna basalts. What makes it potentially very significant is the possibility that it is a sample of a relatively young, thorium-rich basalt flow similar to those inferred to occur in the Procellarum region, especially northwestern Procellarum, on the basis of Lunar Prospector orbital data. Exploiting the lunar regolith for the diversity of rock types that have been delivered to a landing site by impact processes and correlating them to their likely site of origin using remote sensing will be an important part of future missions to the Moon. One such mission is Moonrise, which would collect regolith samples from the South Pole-Aitken Basin, concentrating thousands of rock fragments of 3-20 mm size from the regolith, and returning the samples to Earth.

  8. Lava tubes and aquifer vulnerability in the upper Actopan River basin, Veracruz, México (United States)

    Espinasa-Pereña, R.; Delgado Granados, H.


    Rapid infiltration leads to very dry conditions on the surface of some volcanic terrains, with large allogenic streams sometimes sinking underground upon reaching a lava flow. Aquifers in lava flows tend to be heterogeneous and discontinuous, generally unconfined and fissured, and have high transmissivity. Springs associated with basalts may be very large but are typically restricted to lava-flow margins. Concern has been expressed regarding the potential for lava-tube caves to facilitate groundwater contamination similar to that afflicting some karst aquifers (Kempe et al., 2003; Kiernan et al., 2002; Halliday 2003). The upper Actopan River basin is a series of narrow valleys excavated in Tertiary volcanic brechias. Several extensive Holocene basaltic tube-fed lava flows have partially filled these valleys. The youngest and longest flow originates at El Volcancillo, a 780 ybP monogenetic volcano. It is over 50 km long, and was fed through a major master tube, the remains of which form several lava-tube caves (Gassos and Espinasa-Pereña, 2008). Another tube-fed flow initiates at a vent at the bottom of Barranca Huichila and can be followed for 7 km to where it is covered by the Volcancillo flow. The Huichila River is captured by this system of lava tubes and can be followed through several underground sections. In dry weather the stream disappears at a sump in one of these caves, although during hurricanes it overflows the tube, floods the Tengonapa plain, and finally sinks through a series of skylights into the master tube of the Volcancillo flow. Near villages, the cave entrances are used as trash dumps, which are mobilized during floods. These include household garbage, organic materials associated with agriculture and even medical supplies. This is a relatively recent phenomenon, caused by population growth and the building of houses above the lava flows. The water resurges at El Descabezadero, gushing from fractures in the lava above the underlying brechias

  9. Using submarine lava pillars to record mid-ocean ridge eruption dynamics (United States)

    Gregg, Tracy K.P.; Fornari, Daniel J.; Perfit, Michael R.; Ridley, W. Ian; Kurz, Mark D.


    Submarine lava pillars are hollow, glass-lined, basaltic cylinders that occur at the axis of the mid-ocean ridge, and within the summit calderas of some seamounts. Typically, pillars are ~1-20 m tall and 0.25-2.0 m in diameter, with subhorizontal to horizontal glassy selvages on their exterior walls. Lava pillars form gradually during a single eruption, and are composed of lava emplaced at the eruption onset as well as the last lava remaining after the lava pond has drained. On the deep sea floor, the surface of a basaltic lava flow quenches to glass within 1 s, thereby preserving information about eruption dynamics, as well as chemical and physical properties of lava within a single eruption. Investigation of different lava pillars collected from a single eruption allows us to distinguish surficial lava-pond or lava-lake geochemical processes from those operating in the magma chamber. Morphologic, major-element, petrographic and helium analyses were performed on portions of three lava pillars formed during the April 1991 eruption near 9°50'N at the axis of the East Pacific Rise. Modeling results indicate that the collected portions of pillars formed in ~2-5 h, suggesting a total eruption duration of ~8-20 h. These values are consistent with observed homogeneity in the glass helium concentrations and helium diffusion rates. Major-element compositions of most pillar glasses are homogeneous and identical to the 1991 flow, but slight chemical variations measured in the outermost portions of some pillars may reflect post-eruptive processes rather than those occurring in subaxial magma bodies. Because lava pillars are common at mid-ocean ridges (MORs), the concepts and techniques we present here may have important application to the study of MOR eruptions, thereby providing a basis for quantitative comparisons of volcanic eruptions in geographically and tectonically diverse settings. More research is needed to thoroughly test the hypotheses presented here. (C) 2000

  10. Pomona Member of the Columbia River Basalt Group: an intracanyon flow in the Columbia River Gorge, Oregon. (United States)

    Anderson, J.L.


    The Pomona Member of the Saddle Mountains Basalt (Columbia River Basalt Group) occurs as an intracanyon flow greater than 75m (250ft) thick along the S side of the Columbia River Gorge between Mitchell Point and Shellrock Mountain, Oregon. Best exposures are at Mitchell Point, where this flow caps more than 70m (230ft) of cobble conglomerate that partially fills a canyon cut into flows of the underlying Frenchman Springs Member. These exposures provide a necessary link between outcrops of the Pomona Member in the Columbia Plateau and western Washington. Post-Frenchman Springs, pre-Pomona canyon cutting implies deformation in the ancestral Cascade Range between about 14.5 and 12Ma ago.-Author

  11. Paleomagnetic correlation and ages of basalt flow groups in coreholes at and near the Naval Reactors Facility, Idaho National Laboratory, Idaho (United States)

    Champion, Duane E.; Davis, Linda C.; Hodges, Mary K.V.; Lanphere, Marvin A.


    Paleomagnetic inclination and polarity studies were conducted on subcore samples from eight coreholes located at and near the Naval Reactors Facility (NRF), Idaho National Laboratory (INL). These studies were used to characterize and to correlate successive stratigraphic basalt flow groups in each corehole to basalt flow groups with similar paleomagnetic inclinations in adjacent coreholes. Results were used to extend the subsurface geologic framework at the INL previously derived from paleomagnetic data for south INL coreholes. Geologic framework studies are used in conceptual and numerical models of groundwater flow and contaminant transport. Sample handling and demagnetization protocols are described, as well as the paleomagnetic data averaging process. Paleomagnetic inclination comparisons among NRF coreholes show comparable stratigraphic successions of mean inclination values over tens to hundreds of meters of depth. Corehole USGS 133 is more than 5 kilometers from the nearest NRF area corehole, and the mean inclination values of basalt flow groups in that corehole are somewhat less consistent than with NRF area basalt flow groups. Some basalt flow groups in USGS 133 are missing, additional basalt flow groups are present, or the basalt flow groups are at depths different from those of NRF area coreholes. Age experiments on young, low potassium olivine tholeiite basalts may yield inconclusive results; paleomagnetic and stratigraphic data were used to choose the most reasonable ages. Results of age experiments using conventional potassium argon and argon-40/argon-39 protocols indicate that the youngest and uppermost basalt flow group in the NRF area is 303 ± 30 ka and that the oldest and deepest basalt flow group analyzed is 884 ± 53 ka. A south to north line of cross-section drawn through the NRF coreholes shows corehole-to-corehole basalt flow group correlations derived from the paleomagnetic inclination data. From stratigraphic top to bottom, key results

  12. Predicting the impact of lava flows at Mount Etna by an innovative method based on Cellular Automata: Applications regarding land-use and civil defence planning (United States)

    Crisci, G. M.; Avolio, M. V.; D'Ambrosio, D.; di Gregorio, S.; Lupiano, G. V.; Rongo, R.; Spataro, W.; Benhcke, B.; Neri, M.


    Forecasting the time, character and impact of future eruptions is difficult at volcanoes with complex eruptive behaviour, such as Mount Etna, where eruptions occur from the summit and on the flanks, affecting areas distant from each other. Modern efforts for hazard evaluation and contingency planning in volcanic areas draw heavily on hazard maps and numerical simulations. The computational model here applied belongs to the SCIARA family of lava flow simulation models. In the specific case this is the SCIARA-fv release, which is considered to give the most accurate and efficient performance, given the extent (567 km2) of the study area and the great number of simulations to be carried out. The model is based on the Cellular Automata computational paradigm and, specifically, on the Macroscopic Cellular Automata approach for the modelling of spatially extended dynamic systems2. This work addresses the problem of compiling high-detailed susceptibility maps with an elaborate approach in the numerical simulation of Etnean lava flows, based on the results of 39,300 simulations of flows erupted from a grid of 393 hypothetical vents in the eastern sector of Etna. This sector was chosen because it is densely populated and frequently affected by flank eruptions. Besides the definition of general susceptibility maps, the availability of a large number of lava flows of different eruption types, magnitudes and locations simulated for this study allows the instantaneous extraction of various scenarios on demand. For instance, in a Civil Defence oriented application, it is possible to identify all source areas of lava flows capable of affecting a given area of interest, such as a town or a major infrastructure. Indeed, this application is rapidly accomplished by querying the simulation database, by selecting the lava flows that affect the area of interest and by circumscribing their sources. Eventually, a specific category of simulation is dedicated to the assessment of protective

  13. Late Permian basalts in the Yanghe area, eastern Sichuan Province, SW China: Implications for the geodynamics of the Emeishan flood basalt province and Permian global mass extinction (United States)

    Li, Hongbo; Zhang, Zhaochong; Santosh, M.; Lü, Linsu; Han, Liu; Liu, Wei


    We report the finding of a ∼20 m thick sequence of massive pyroxene-plagioclase-phyric basalt lava flows in the Yanghe area of the northeastern Sichuan Basin, within the Yangtze craton of SW China, which were previously considered to be located outside the Emeishan flood basalt province. This basaltic sequence above the middle Permian Maokou Formation (Fm.) is overlain by the late Permian Longtan Fm. Thus, the Yanghe basalts should be stratigraphically correlated with the Emeishan flood basalts. The Yanghe basalts show typical oceanic island basalt (OIB) affinity, and geochemically resemble Emeishan basalts, especially in the case of high-Ti (HT) basalts from the eastern domain of the Emeishan flood basalt province. The rocks have low age-corrected (87Sr/86Sr)t (t = 260 Ma) ratios (0.704158-0.704929) and Pb isotopic ratios [206Pb/204Pb(t) (18.264-18.524), 207Pb/204Pb(t) (15.543-15.58), and 208Pb/204Pb(t) (38.147-38.519)], and positive εNd(t) values (+3.15 to +3.61), suggesting that the lavas have not undergone any significant crustal contamination. The crystallization temperature of clinopyroxene is estimated to be 1368-1420 °C, suggesting anomalously thermal inputs from a mantle source and a possible plume-head origin. The fractionation of middle rare earth elements (MREE) to heavy REE (HREE) suggests that these rocks were produced by small degrees of partial melting of mantle peridotite within the garnet-spinel transition region. The stratigraphic relationships and similar geochemical signatures with the Emeishan flood basalts suggest that the Yanghe basalts are part of the Emeishan flood basalt province and can be considered as the northeastern limit of the Emeishan flood basalt province. Our finding extends the diameter of the Emeishan flood basalt province to ∼1200-1400 km, covering an area of up to ∼7 × 105 km2, two times more than previously estimated. The larger areal extent and giant eruption volume, incorporating the Sichuan Basin, lend support

  14. Palaeomagnetic intensities from 14C-dated lava flows on the Big Island, Hawaii: 0-21 kyr (United States)

    Pressling, Nicola; Laj, Carlo; Kissel, Catherie; Champion, Duane E.; Gubbins, David


    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.

  15. Conceptual Model of the Geometry and Physics of Water Flow in a Fractured Basalt Vadose Zone: Box Canyon Site, Idaho

    Energy Technology Data Exchange (ETDEWEB)

    Faybishenko, Boris [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Doughty, Christine [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Steiger, Michael [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Long, Jane C.S. [Univ. of Nevada, Reno, NV (US). Mackay School of Mines; Wood, Tom [Parsons Engineering, Inc., Idaho Falls, ID (United States); Jacobsen, Janet [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Lore, Jason [Stanford Univ., CA (United States); Zawislanski, Peter T. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)


    A conceptual model of the geometry and physics of water flow in a fractured basalt vadose zone was developed based on the results of lithological studies and a series of ponded infiltration tests conducted at the Box Canyon site near the Idaho National Engineering and Environmental Laboratory (INEEL) in Idaho. The infiltration tests included one two-week test in 1996, three two-day tests in 1997, and one four-day test in 1997. For the various tests, initial infiltration rates ranged from 4.1 cm/day to 17.7 cm/day and then decreased with time, presumably due to mechanical or microbiological clogging of fractures and vesicularbasalt in the near-surface zone, as well as the effect of entrapped air. The subsurface moisture redistribution was monitored with tensiometers, neutron logging, time domain reflectrometry and ground penetrating radar. A conservative tracer, potassium bromide, was added to the pond water at a concentration of 3 g/L to monitor water flow with electrical resistivity probes and water sampling. Analysis of the data showed evidence of preferential flow rather than the propagation of a uniform wetting front. We propose a conceptual model describing the saturation-desaturation behavior of the basalt, in which rapid preferential flow through vertical column-bounding fractures occurs from the surface to the base of the basalt flow. After the rapid wetting of column-bounding fractures, a gradual wetting of other fractures and the basalt matrix occurs. Fractures that are saturated early in the tests may become desaturated thereafter, which we attribute to the redistribution of water between fractures and matrix. Lateral movement of water was also observed within a horizontal central fracture zone and rubble zone, which could have important implications for contaminant accumulation at contaminated sites.

  16. Morphology and development of pahoehoe flow-lobe tumuli and associated features from a monogenetic basaltic volcanic field, Bahariya Depression, Western Desert, Egypt (United States)

    Khalaf, Ezz El Din Abdel Hakim; Hammed, Mohamed Saleh


    The dimensions, landforms, and structural characteristics of pahoehoe flow-lobe tumuli from Bahariya Depression are collectively reported here for the first time. The flow-lobe tumuli documented here characterize hummocky flow surfaces. These tumuli are characterized by low, dome-like mounds, lava-inflation clefts, and squeeze ups. Flow-lobe tumuli are of various shapes and sizes, which are affected by the mechanism of inflation because they formed in response to the increase of pressure within the flow when the flow's crust becomes thicker. The tumuli often appear isolated or in small groups in the middle sectors of the lava flows, whereas in the distal sectors they form large concentration, suggesting the presence of complex lava tubes inside of the flow. Tumuli exhibited by El Bahariya lava flows are between 3.0 and 50 m in length and up to 5.0 m in height with lenticular geometry in aerial view. The flow emplacement of flow-lobe tumuli is controlled by variations in local characteristics such as nature of the substrate, flow orientation, slope, interferrence with other lobes, and rate of lava supply. Their presence generally towards the terminal ends of flow fields suggests that they seldom form over the clogged portions of distributary tubes or pathways. Thus, localized inflations that formed over blockages in major lava tubes result in formation of flow-lobe tumuli. The three-tiered (crust-core-basal zone) internal structure of the flow-lobe tumuli, resembling the typical distribution of vesicles in P-type lobes, confirms emplacement by the mechanism of inflation. All the available data show that the morphology and emplacement mechanism of the studied flow-lobe tumuli may be analogous to similar features preserved within topographically confined areas of the Hawaiian and Deccan hummocky lava flows. Considering the age of the studied volcanic fields (˜22 Ma) it is most probable that the structures described here may be amongst the oldest recognized examples

  17. Middle Triassic back-arc basalts from the blocks in the Mersin Mélange, southern Turkey: Implications for the geodynamic evolution of the Northern Neotethys (United States)

    Sayit, Kaan; Bedi, Yavuz; Tekin, U. Kagan; Göncüoglu, M. Cemal; Okuyucu, Cengiz


    The Mersin Mélange is a tectonostratigraphic unit within the allochthonous Mersin Ophiolitic Complex in the Taurides, southern Turkey. This chaotic structure consists of blocks and tectonic slices of diverse origins and ages set in a clastic matrix of Upper Cretaceous age. In this study, we examine two blocks at two different sections characterized by basaltic lava flows alternating with radiolarian-bearing pelagic sediments. The radiolarian assemblage extracted from the mudstone-chert alternation overlying the lavas yields an upper Anisian age (Middle Triassic). The immobile element geochemistry suggests that the lava flows are predominantly characterized by sub-alkaline basalts. All lavas display pronounced negative Nb anomalies largely coupled with normal mid-ocean basalt (N-MORB)-like high field strength element (HFSE) patterns. On the basis of geochemical modelling, the basalts appear to have dominantly derived from spinel-peridotite and pre-depleted spinel-peridotite sources, while some enriched compositions can be explained by contribution of garnet-facies melts from enriched domains. The overall geochemical characteristics suggest generation of these Middle Triassic lavas at an intra-oceanic back-arc basin within the northern branch of Neotethys. This finding is of significant importance, since these rocks may represent the presence of the oldest subduction zone found thus far from the Neotethyan branches. This, in turn, suggests that the rupturing of the Gondwanan lithosphere responsible for the opening of the northern branch of Neotethys should have occurred during the Lower Triassic or earlier.

  18. A Link of measurements of lava flows to Palaeoelevation estimations and its application in Tengchong volcanic eruptive field in Yunnan Province ( SW China )%火山“熔岩流气泡古高度计”及其在云南腾冲火山区的应用

    Institute of Scientific and Technical Information of China (English)

    郭正府; 张茂亮; 成智慧; 刘嘉麒; 张丽红; 李晓惠


    Based on measurements of thickness of lava flow and sizes of the vesicles at the top and the bottom of the lava flow, the palaeoelevation of Heikongshan lava flow emplacement in Tengchong volcanic eruptive field (SW China) at the Holocene times may be calculated by a relation of the palaeoatmospheric pressure with vesicle sizes in the lava flow. The lava flow, which could be used as paleoelevation calculations in Tengchong, had to merely undergo a simple and clearly recognized history from eruption, cooling to emplacement without inflation and deflation based on the observations and analyses in the field works during 2009 ~ 2010AD. In theory, the best fit thickness for the lava flow to the calculations of palaeopressure and then palaeoelevation is about 3m, which could produce one bar of palaeoatmospheric pressure at its top and two bars of total pressure at its bottom. In fact, the basaltic flows with 1 ~ Sm in thickness have been used as candidates for the calculations of palaeoelevation in the Heikongshan lava flows of Tengchong volcanic eruptive field (SW China). Unlike the measurements of the thickness of lava flow in the field work, sizes of the vesicles at the top and the bottom of the lava flow could be merely determined in the laboratory, the most accurate technique of which is 3D X-ray Tomography in situ. We have carried out the analysis of the sizes of the vesicles at the top and the bottom of the Heikongshan lava flows by microscope observations, based on a conversion from 2D to 3D by calculations. The final calculation results have indicated that palaeoelevation of the Heikongshan lava flow is about 1713 ~ 2613m. On the basis of comparison between actual and calculation elevations, our calculated results could be accepted. Outcrops of the post-collisional most primitive lava flows are widely distributed across the Tibetan Plateau including its interior and margins; there are more than 50 sites of the Cenozoic volcanic eruptive fields in the plateau

  19. Palaeomagnetic refinement of the eruption ages of Holocene lava flows, and implications for the eruptive history of the Tongariro Volcanic Centre, New Zealand (United States)

    Greve, Annika; Turner, Gillian M.; Conway, Chris E.; Townsend, Dougal B.; Gamble, John A.; Leonard, Graham S.


    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.

  20. Precaldera lavas of the southeast San Juan Volcanic Field: Parent magmas and crustal interactions (United States)

    Colucci, M. T.; Dungan, M. A.; Ferguson, K. M.; Lipman, P. W.; Moorbath, S.


    Early intermediate composition volcanic rocks of the Oligocene (circa 34-29 Ma) southeast San Juan volcanic field, southern Colorado, comprise the Conejos Formation. Conejos lavas include both high-K calc-alkaline and alkaline magma series (54-69% SiO2) ranging in composition from basaltic andesite (basaltic trachyandesite) to dacite (trachydacite). The subsequent Platoro caldera complex (29-27 Ma) was superimposed on a cluster of broadly precursory Conejos stratocones. Precaldera volcanism occurred in three pulses corresponding to three time-stratigraphic members: (1) the Horseshoe Mountain member, (2) the Rock Creek member, and (3) the Willow Mountain member. Each member exhibits distinctive phenocryst modes and incompatible trace element contents. Horseshoe Mountain lavas (hornblende-phyric) have relatively low alkali and incompatible element abundances, Rock Creek lavas (anhydrous phenocrysts) and ash-flow tuffs have the highest abundances, and Willow Mountain lavas (diverse mineralogy) are intermediate. All Conejos lavas exhibit low ratios of lead (206Pb/204Pb = 17.5 to 18.2) and neodymium (ɛNd = -8 to -4) isotopes and high 87Sr/86Sr (0.7045 to 0.7056) compared to depleted asthenospheric mantle. These values lie between those of likely mantle compositions and the isotopic composition of Proterozoic crust of the southern Rocky Mountains. Mafic lavas of the Horseshoe Mountain member have the lowest Pb and Nd isotope ratios among Conejos members but trend toward higher isotopic values with increasing degrees of differentiation. Compositions within the Rock Creek series trend toward higher Pb and lower Nd isotope ratios with increasing SiO2. Willow mountain volcanic sequences define diverse chemical-isotopic correlations. We interpret the chemical and isotopic differences observed between mafic lavas of each member to reflect derivation from compositionally distinct mantle derived parent magmas that have experienced extensive deep level crustal contamination

  1. Estimation of lava flow field volumes and volumetric effusion rates from airborne radar profiling and other data: Monitoring of the Nornahraun (Holuhraun) 2014/15 eruption in Iceland (United States)

    Dürig, Tobias; Gudmundsson, Magnús; Högnadóttir, Thordís; Jónsdóttir, Ingibjörg; Gudbjörnsson, Snaebjörn; Lárusson, Örnólfur; Höskuldsson, Ármann; Thordarson, Thorvaldur; Riishuus, Morten; Magnússon, Eyjólfur


    Monitoring of lava-producing eruptions involves systematic measurement of flow field volumes, which in turn can be used to obtain average magma discharge over the period of observation. However, given inaccessibility to the interior parts of active lava fields, remote sensing techniques must be applied. Several satellite platforms provide data that can be geo-referenced, allowing area estimation. However, unless sterographic or tandem satellite data are available, the determination of thicknesses is non-trivial. The ongoing eruption ('Nornaeldar')at Dyngjusandurin the Icelandic highlands offers an opportunity to monitor the temporal and spatial evolution of a typical Icelandic lava flow field. The mode of emplacementis complex and includesboth horizontal and vertical stacking, inflation of lobes and topographic inversions. Due to the large extent of the flow field (>83 km2 on 5 Jan 2015, and still growing) and its considerable local variation in thickness (30 m) and surface roughness, obtaining robust quantification of lava thicknesses is very challenging,despite the lava is being emplaced onto a low-relief sandur plain. Creative methods have been implemented to obtain as reliable observation as possible into the third dimension: Next to areal extent measurements from satellites and maps generated with airborne synthetic-aperture radar (SAR), lava thickness profiles are regularly obtained by low-level flights with a fixed-wing aircraft that is equipped with a ground clearance radar coupled witha submeter DGPS,a system originally designed for monitoring surface changes of glaciers above geothermally active areas.The resulting radar profile data are supplemented by analyses of aerial photos and complemented by results from an array of ground based thickness measurement methods. The initial results indicate that average effusion ratewas ~200 m3/s in the first weeks of the eruption (end August, early September) but declined to 50-100 m3/s in November to December period

  2. Hawaiian cultural influences on support for lava flow hazard mitigation measures during the January 1960 eruption of Kīlauea volcano, Kapoho, Hawai‘i (United States)

    Gregg, Chris E.; Houghton, B.F.; Paton, Douglas; Swanson, D.A.; Lachman, R.; Bonk, W.J.


    In 1960, Kīlauea volcano in Hawaii erupted, destroying most of the village of Kapoho and forcing evacuation of its approximately 300 residents. A large and unprecedented social science survey was undertaken during the eruption to develop an understanding of human behavior, beliefs, and coping strategies among the adult evacuees (n = 160). Identical studies were also performed in three control towns located at varying distances from the eruption site (n = 478). During these studies data were collected that characterized ethnic grouping and attitudes toward Hawaiian cultural issues such as belief in Pele and two lava flow mitigation measures—use of barriers and bombs to influence the flow of lava, but the data were never published. Using these forgotten data, we examined the relationship between Hawaiian cultural issues and attitudes toward the use of barriers and bombs as mitigation strategies to protect Kapoho.

  3. The mode of emplacement of Neogene flood basalts in eastern Iceland: Facies architecture and structure of simple aphyric basalt groups (United States)

    Óskarsson, Birgir V.; Riishuus, Morten S.


    Simple flows (tabular) in the Neogene flood basalt sections of Iceland are described and their mode of emplacement assessed. The flows belong to three aphyric basalt groups: the Kumlafell group, the Hólmatindur group and the Hjálmadalur group. The groups can be traced over 50 km and originate in the Breiðdalur-Thingmuli volcanic zone. The groups have flow fields that display mixed volcanic facies architecture and can be classified after dominating type morphology. The Kumlafell and the Hólmatindur groups have predominantly simple flows of pāhoehoe and rubbly pāhoehoe morphologies with minor compound or lobate pāhoehoe flows. The Hjálmadalur group has simple flows of rubbly pāhoehoe, but also includes minor compound or lobate flows of rubble and 'a'ā. Simple flows are most common in the distal and medial areas from the vents, while more lobate flows in proximal areas. The simple flows are formed by extensive sheet lobes that are several kilometers long with plane-parallel contacts, some reaching thicknesses of ~ 40 m (aspect ratios inflation structures. Their internal structure consists generally of a simple upper vesicular crust, a dense core and a thin basal vesicular zone. The brecciated flow-top is formed by clinker and crustal rubble, the clinker often welded or agglutinated. The simple flows erupted from seemingly short-lived fissures and have the characteristics of cooling-limited flows. We estimate the effusion rates to be ~ 105 m3/s for the simple flows of the Kumlafell and Hólmatindur groups and ~ 104 m3/s for the Hjálmadalur group. The longest flows advanced 15-20 km from the fissures, with lava streams of fast propagating flows inducing tearing and brecciation of the chilled crust. Compound or lobate areas appear to reflect areas of low effusion rates or the interaction of the lava with topographic barriers or wetlands, resulting in chaotic flowage. Slowing lobes with brecciated flow-tops developed into 'a'ā flows. The groups interdigitated

  4. The influence of effusion rate and rheology on lava flow dynamics and morphology: A case study from the 1971 and 1988-1990 eruptions at Villarrica and Lonquimay volcanoes, Southern Andes of Chile (United States)

    Castruccio, Angelo; Contreras, María Angélica


    We analyzed two historical lava flows from the Southern Andes of Chile: The lava flows from the 1971 Villarrica volcano eruption and the 1988-1990 Lonquimay volcano eruption. The 1971 lava flow has a volume of 2.3 × 107 m3, a maximum length of 16.5 km and was emplaced in two days, with maximum effusion rates of 800 m3/s. The lava has a mean width of 150 m and thicknesses that decrease from 10 to 12 m at 5 km from the vent to 5-8 m at the flow front. The morphology is mainly 'a'ā. The 1988-1990 lava flow has a volume of 2.3 × 108 m3, a maximum length of 10.2 km and was emplaced in 330 days, with peak effusion rates of 80 m3/s. The flow has a mean width of 600 m and thicknesses that increase from 10 to 15 m near the vent to > 50 m at the front. The morphology varies from 'a'ā in proximal sectors to blocky in the rest of the flow. We modelled the advance rate and thickness of these flows assuming two possible dynamical regimes: An internal rheology regime modelled as a Herschel-Bulkley (HB) fluid and a Yield Strength in the Crust (YSC) regime. We compared our results with the widely used Newtonian and Bingham rheologies. Our results indicate that the 1971 flow can be modelled either by the HB, Bingham or Newtonian rheologies using a single temperature, while the 1988-1990 flow was controlled by the YSC regime. Our analysis and comparison of models shows that care should be taken when modelling a lava flow, as different rheologies and assumptions can reach the same results in terms of advance rate and flow thickness. These examples suggest that the crustal strength should be taken into account in any model of lava flow advance.

  5. Constraining the onset of flood volcanism in Isle of Skye Lava Field, British Paleogene Volcanic Province (United States)

    Angkasa, Syahreza; Jerram, Dougal. A.; Svensen, Henrik; Millet, John M.; Taylor, Ross; Planke, Sverre


    In order to constrain eruption styles at the onset of flood volcanism, field observations were undertaken on basal sections of the Isle of Skye Lava Field, British Paleogene Volcanic Province. This study investigates three specific sections; Camus Ban, Neist Point and Soay Sound which sample a large area about 1500 km2 and can be used to help explain the variability in palaeo-environments at the onset of flood volcanism. Petrological analysis is coupled with petrophysical lab data and photogrammetry data to create detailed facies models for the different styles of initiating flood basalt volcanism. Photogrammetry is used to create Ortho-rectified 3D models which, along with photomontage images, allow detailed geological observations to be mapped spatially. Petrographic analyses are combined with petrophysical lab data to identify key textural variation, mineral compositions and physical properties of the volcanic rocks emplaced during the initial eruptions. Volcanism initiated with effusive eruptions in either subaerial or subaqueous environments resulting in tuff/hyaloclastite materials or lava flow facies lying directly on the older Mesozoic strata. Volcanic facies indicative of lava-water interactions vary significantly in thickness between different sections suggesting a strong accommodation space control on the style of volcanism. Camus Ban shows hyaloclastite deposits with a thickness of 25m, whereas the Soay Sound area has tuffaceous sediments of under 0.1m in thickness. Subaerial lavas overly these variable deposits in all studied areas. The flood basalt eruptions took place in mixed wet and dry environments with some significant locally developed water bodies (e.g. Camus Ban). More explosive eruptions were promoted in some cases by interaction of lavas with these water bodies and possibly by local interaction with water - saturated sediments. We record key examples of how palaeotopography imparts a primary control on the style of volcanism during the

  6. 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


    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.

  7. Inverse modeling of Central American lavas: old lithospheric and young asthenospheric heterogeneities (United States)

    Feigenson, M.; Gazel, E.; Carr, M. J.


    In recent years, there have been a number of models proposed to account for the OIB-like geochemical characteristics of lavas from central Costa Rica. The source for most basalts of the Central American volcanic front (ranging from Guatemala to northern Costa Rica) is dominantly DM (depleted MORB-source mantle) fluxed by subduction-derived fluids. In contrast, central Costa Rican basalts display striking isotopic similarities to the Galapagos hotspot. How the Galapagos signature is introduced into the Central American source is at the heart of the conflicting theories. Several models incorporate asthenospheric flow of this enriched mantle, either around the Central American arc via South America, or through a slab window, which may have opened about 5 my ago beneath central Costa Rica. Alternatively, passage of the Caribbean plate over the Galapagos hotspot may have left veins of unerupted melt within the sub-Caribbean lithosphere. These veins may be preferentially tapped during later superimposed arc volcanism. Although these models yield identical isotopic systematics, it may be possible to distinguish between them by a geochemical technique that can indicate the presence of garnet in the source region. This method, developed by Hofmann and coworkers in the 1980s, is termed inverse modeling, and uses the variation of REEs in lavas to assess the relative importance of garnet vs. clinopyroxene during partial melting. We have applied this method to new REE data from back arc lavas throughout Central America, and preliminary results indicate that garnet is not present in their sources. In contrast, direct slab melts (adakites) from Central America, as well as volcanic front lavas and alkaline basalt (with minimal slab signature) from central Costa Rica and Panama, require a source with garnet. Therefore, enriched mantle in the back arc is likely stored in the shallow lithosphere rather than introduced through asthenospheric flow. Enriched material in the volcanic

  8. A field investigation of the basaltic ring structures of the Channeled Scabland and the relevance to Mars (United States)

    Kestay, Laszlo P.; Jaeger, Windy L.


    The basaltic ring structure (BRS) is a class of peculiar features only reported in the Channeled Scabland of eastern Washington State. They have been suggested to be good analogs, however, for some circular features on Mars. BRSs are found where Pleistocene floods scoured the Columbia River Basin, stripping off the uppermost part of the Miocene Columbia River Basalt Group and exposing structures that were previously embedded in the lava. The “Odessa Craters,” near Odessa, WA, are 50–500-m-wide BRSs that are comprised of discontinuous, concentric outcrops of subvertically-jointed basalt and autointrusive dikes. Detailed field investigation of the Odessa Craters in planform and a cross-sectional exposure of a similar structure above Banks Lake, WA, lead us to propose that BRSs formed by concurrent phreatovolcanism and lava flow inflation. In this model, phreatovolcanic (a.k.a., “rootless”) cones formed on a relatively thin, active lava flow; the lava flow inflated around the cones, locally inverting topography; tensile stresses caused concentric fracturing of the lava crust; lava from within the molten interior of the flow exploited the fractures and buried the phreatovolcanic cones; and subsequent erosive floods excavated the structures. Another population of BRSs near Tokio Station, WA, consists of single-ringed, raised-rimmed structures that are smaller and more randomly distributed than the Odessa Craters. We find evidence for a phreatovolcanic component to the origin as well, and hypothesize that they are either flood-eroded phreatovolcanic cones or Odessa Crater-like BRSs. This work indicates that BRSs are not good analogs to the features on Mars because the martian features are found on the uneroded surfaces. Despite this, the now superseded concepts for BRS formation are useful for understanding the formation of the martian features.

  9. Enhanced crystal fabric analysis of a lava flow sample by neutron texture diffraction: A case study from the Castello d'Ischia dome (United States)

    Walter, Jens M.; Iezzi, Gianluca; Albertini, Gianni; Gunter, Mickey E.; Piochi, Monica; Ventura, Guido; Jansen, Ekkehard; Fiori, Fabrizio


    The crystal fabric of a lava has been analyzed for the first time by neutron texture diffraction. In this study we quantitatively investigate the crystallographic preferred orientation of feldspars in the Castello d'Ischia (Ischia Island, Italy) trachytic exogenous dome. The crystallographic preferred orientation was measured with the monochromatic neutron texture diffractometer SV7 at the Forschungszentrum Jülich in Germany and a Rietveld refinement was applied to the sum diffraction pattern. The complementary thin section analysis showed that the three-dimensional crystal shape and the corresponding shape preferred orientation are in agreement with the quantitative orientation distributions of the neutron texture data. The (0k0) crystallographic planes of the feldspars are roughly parallel to the local flow bands, whereas the other corresponding pole figures show that a pivotal rotation of the anorthoclase and sanidine crystals was active during the emplacement of this lava dome. In combination with scanning electron microscopy investigations, electron probe microanalysis, XRF, and X-ray diffraction, the Rietveld refinement of the neutron diffraction data indicates a slow cooling dynamic on the order of several months during their crystallization under subaerial conditions. Results attained here demonstrate that neutron texture diffraction is a powerful tool that can be applied to lava flows.

  10. Development of lava tubes in the light of observations at Mauna Ulu, Kilauea Volcano, Hawaii (United States)

    Peterson, D.W.; Holcomb, R.T.; Tilling, R.I.; Christiansen, R.L.


    conclude, therefore, that the tendency of active pahoehoe flows to form lava tubes is a significant factor in producing the common shield morphology of basaltic volcanoes. ?? 1994 Springer-Verlag.

  11. Energy and Carbon Flow: Comparing ultramafic- and basalt-hosted vents (United States)

    Perner, M.; Bach, W.; Seifert, R.; Strauss, H.; Laroche, J.


    In deep-sea vent habitats hydrothermal fluids provide the grounds for life by supplying reduced inorganic compounds (e.g. H2, sulfide). Chemolithoautotrophs can oxidize these substrates hereby yielding energy, which can then be used to fuel autotrophic CO2 fixation. Depending on the type of host rocks (and the degree of admixed ambient seawater) the availability of inorganic electron donors can vary considerably. While in ultramafic-hosted vents H2 levels are high and H2-oxidizing metabolisms are thought to dominate, in basalt-hosted vents, H2 is much lower and microbial sulfide oxidation is considered to prevail [1, 2]. We have investigated the effect of H2 and sulfide availability on the microbial community of distinct H2-rich and H2-poor vent sites along the Mid-Atlantic Ridge. Hydrothermally influenced samples were collected from the H2-rich ultramafic-hosted Logatchev field (15°N) and the comparatively H2-poor basalt-hosted vents from 5°S and 9°S. We conducted catabolic energy calculations to estimate the potential of various electron donors to function as microbial energy sources. We performed incubation experiments with hydrothermal fluids amended with H2 or sulfide and radioactively labelled bicarbonate and determined H2 and sulfide consumption and carbon incorporation rates. We constructed metagenomic libraries for sequence-based screening of genes encoding key enzymes for H2 uptake (NiFe uptake hydrogenases, group 1), sulfide oxidation (sulfide quinone oxidoreductase, sqr) and CO2 fixation pathways (RubisCOs of the Calvin cycle [CBB] and beta-subunit of the ATP citrate lyase of the reductive tricarboxylic acid cycle [rTCA]). We evaluated parts of the metagenomes from basalt-hosted sites by pyrosequencing. Based on our incubation experiments - under the conditions applied - we could not confirm that generally H2 consumption rates and biomass syntheses in fluids derived from ultramafic-hosted locations are significantly enhanced over those from basalt

  12. Naming Lunar Mare Basalts: Quo Vadimus Redux (United States)

    Ryder, G.


    Nearly a decade ago, I noted that the nomenclature of lunar mare basalts was inconsistent, complicated, and arcane. I suggested that this reflected both the limitations of our understanding of the basalts, and the piecemeal progression made in lunar science by the nature of the Apollo missions. Although the word "classification" is commonly attached to various schemes of mare basalt nomenclature, there is still no classification of mare basalts that has any fundamental grounding. We remain basically at a classification of the first kind in the terms of Shand; that is, things have names. Quoting John Stuart Mill, Shand discussed classification of the second kind: "The ends of scientific classification are best answered when the objects are formed into groups respecting which a greater number of propositions can be made, and those propositions more important than could be made respecting any other groups into which the same things could be distributed." Here I repeat some of the main contents of my discussion from a decade ago, and add a further discussion based on events of the last decade. A necessary first step of sample studies that aims to understand lunar mare basalt processes is to associate samples with one another as members of the same igneous event, such as a single eruption lava flow, or differentiation event. This has been fairly successful, and discrete suites have been identified at all mare sites, members that are eruptively related to each other but not to members of other suites. These eruptive members have been given site-specific labels, e.g., Luna24 VLT, Apollo 11 hi-K, A12 olivine basalts, and Apollo 15 Green Glass C. This is classification of the first kind, but is not a useful classification of any other kind. At a minimum, a classification is inclusive (all objects have a place) and exclusive (all objects have only one place). The answer to "How should rocks be classified?" is far from trivial, for it demands a fundamental choice about nature

  13. Measurement and Modeling on Flow Hydrodynamics in Crushed Basalt in Support of Constructed Hillslopes in Biosphere 2 (United States)

    Schaap, M. G.; Gallo, P.


    The University of Arizona has recently acquired Biosphere 2 (B2) as an environmental research and environmental facility. As part of a ten year management plan 3 hillslopes (12x30x1 meters) will be constructed within one of the B2 greenhouses. The general objective is to carry out ground-breaking integrated hydro-geo-ecological research that cannot be carried out anywhere else. The intended soil for the hillslopes will have a loamy sand texture and consist of crushed basalt to ensure both reasonable hydraulic properties and weatherability. At this point there is still significant uncertainty about how crushing and grinding basalt will affect the hydraulic characteristics of the soil material. To date some initial textural and saturated hydraulic conductivity analyses of different grindings have been carried out, but an integrated 1D flow experiment will provide much more definitive data about the hydrological and geochemical dynamics that can be expected in the final 3D hillslopes. To this end we will carry out drainage experiments on four (L=90, D=10 cm) columns holding material with different grinding times. Final results for water content, flow rate and pressure will be modeled with Hydrus-1D, while Hydrus 3D will be used to assess the hydrodynamics of the full 3D hillslopes

  14. Influence of Geological and Geomorphological Characteristics on Groundwater Occurrence in Deccan Basalt Hard Rock Area of Tawarja river Sub-Basin Latur, Maharashtra, India

    Directory of Open Access Journals (Sweden)



    Full Text Available The entire study area is covered by Deccan basalt formations comprising nearly horizontal lava flows of late Cretaceous to early Eocene. There are eight flows of lava found in the area and these flows have been considered to be a result of fissure type lava eruption. The types of basaltic flows occurring in the area are simple basalt (aa type and vesicular-amygdaloidal (Compound pahoehoe type basalt flow and also red bole beds (Tachylitic bands are observed in the exposures, quarries and well sections. The drainage pattern varies from dendritic to sub-dendritic and sub-parallel. The bifurcation ratio is moderate (3.00 to 4.67 and the lower values of drainage density (1.77 km/km2 and stream frequency (1.74 streams/km2 indicates the region is of permeable subsoil strata of the basin. Morphometric attributes like form factor (0.85, circularity ratio (0.37 and elongation ratio (0.63 reflects the early mature stage of erosional development. The groundwater occurrence with reference to hydrogeological and geomorphological characters of the sub-basin is discussed. The groundwater occurrence is good productive in the geomorphic surfaces like moderately dissected plateau and pediplains, moderate in highly dissected plateau and lateritic uplands and poor in denudational hills.

  15. Understanding heat and groundwater flow through continental flood basalt provinces: insights gained from alternative models of permeability/depth relationships for the Columbia Plateau, USA (United States)

    Burns, Erick R.; Williams, Colin F.; Ingebritsen, Steven E.; Voss, Clifford I.; Spane, Frank A.; DeAngelo, Jacob


    Heat-flow mapping of the western USA has identified an apparent low-heat-flow anomaly coincident with the Columbia Plateau Regional Aquifer System, a thick sequence of basalt aquifers within the Columbia River Basalt Group (CRBG). A heat and mass transport model (SUTRA) was used to evaluate the potential impact of groundwater flow on heat flow along two different regional groundwater flow paths. Limited in situ permeability (k) data from the CRBG are compatible with a steep permeability decrease (approximately 3.5 orders of magnitude) at 600–900 m depth and approximately 40°C. Numerical simulations incorporating this permeability decrease demonstrate that regional groundwater flow can explain lower-than-expected heat flow in these highly anisotropic (kx/kz ~ 104) continental flood basalts. Simulation results indicate that the abrupt reduction in permeability at approximately 600 m depth results in an equivalently abrupt transition from a shallow region where heat flow is affected by groundwater flow to a deeper region of conduction-dominated heat flow. Most existing heat-flow measurements within the CRBG are from shallower than 600 m depth or near regional groundwater discharge zones, so that heat-flow maps generated using these data are likely influenced by groundwater flow. Substantial k decreases at similar temperatures have also been observed in the volcanic rocks of the adjacent Cascade Range volcanic arc and at Kilauea Volcano, Hawaii, where they result from low-temperature hydrothermal alteration.

  16. Understanding heat and groundwater flow through continental flood basalt provinces: insights gained from alternative models of permeability/depth relationships for the Columbia Plateau, USA

    Energy Technology Data Exchange (ETDEWEB)

    Burns, Erick R.; Williams, Colin F.; Ingebritsen, Steven E.; Voss, Clifford I.; Spane, Frank A.; DeAngelo, Jacob


    Heat-flow mapping of the western USA has identified an apparent low-heat-flow anomaly coincident with the Columbia Plateau Regional Aquifer System, a thick sequence of basalt aquifers within the Columbia River Basalt Group (CRBG). A heat and mass transport model (SUTRA) was used to evaluate the potential impact of groundwater flow on heat flow along two different regional groundwater flow paths. Limited in situ permeability (k) data from the CRBG are compatible with a steep permeability decrease (approximately 3.5 orders of magnitude) at 600–900 m depth and approximately 40°C. Numerical simulations incorporating this permeability decrease demonstrate that regional groundwater flow can explain lower-than-expected heat flow in these highly anisotropic (kx/kz ~ 104) continental flood basalts. Simulation results indicate that the abrupt reduction in permeability at approximately 600 m depth results in an equivalently abrupt transition from a shallow region where heat flow is affected by groundwater flow to a deeper region of conduction-dominated heat flow. Most existing heat-flow measurements within the CRBG are from shallower than 600 m depth or near regional groundwater discharge zones, so that heat-flow maps generated using these data are likely influenced by groundwater flow. Substantial k decreases at similar temperatures have also been observed in the volcanic rocks of the adjacent Cascade Range volcanic arc and at Kilauea Volcano, Hawaii, where they result from low-temperature hydrothermal alteration.

  17. Temperature profile around a basaltic sill intruded into wet sediments (United States)

    Baker, Leslie; Bernard, Andrew; Rember, William C.; Milazzo, Moses; Dundas, Colin M.; Abramov, Oleg; Kestay, Laszlo P.


    The transfer of heat into wet sediments from magmatic intrusions or lava flows is not well constrained from field data. Such field constraints on numerical models of heat transfer could significantly improve our understanding of water–lava interactions. We use experimentally calibrated pollen darkening to measure the temperature profile around a basaltic sill emplaced into wet lakebed sediments. It is well known that, upon heating, initially transparent palynomorphs darken progressively through golden, brown, and black shades before being destroyed; however, this approach to measuring temperature has not been applied to volcanological questions. We collected sediment samples from established Miocene fossil localities at Clarkia, Idaho. Fossils in the sediments include pollen from numerous tree and shrub species. We experimentally calibrated changes in the color of Clarkia sediment pollen and used this calibration to determine sediment temperatures around a Miocene basaltic sill emplaced in the sediments. Results indicated a flat temperature profile above and below the sill, with T > 325 °C within 1 cm of the basalt-sediment contact, near 300 °C at 1–2 cm from the contact, and ~ 250 °C at 1 m from the sill contact. This profile suggests that heat transport in the sediments was hydrothermally rather than conductively controlled. This information will be used to test numerical models of heat transfer in wet sediments on Earth and Mars.

  18. Undercooled water in basaltic regoliths and implications for fluidized debris flows on Mars (United States)

    Gooding, James L.


    Pursuant to the past attribution of many geomorphic features on Mars to the movements of water- or ice-lubricated debris, experiments have been conducted for water freezing in wet, sand-like basaltic substrates. It is found that substantial undercooling can be achieved under Martian conditions, independently of freezing-point depressions due to soluble salts. Attention is given to results for a clay-poor soil with negligible salinity from Mauna Kea, Hawaii, which demonstrate that the degree of undercooling is essentially independent of both soil particle size and water/soil mass ratio, albeit with cooling rate variations.

  19. Environmental implication of subaqueous lava flows from a continental Large Igneous Province: Examples from the Moroccan Central Atlantic Magmatic Province (CAMP) (United States)

    El Ghilani, S.; Youbi, N.; Madeira, J.; Chellai, E. H.; López-Galindo, A.; Martins, L.; Mata, J.


    The Late Triassic-Early Jurassic volcanic sequence of the Central Atlantic Magmatic Province (CAMP) of Morocco is classically subdivided into four stratigraphic units: the Lower, Middle, Upper and Recurrent Formations separated by intercalated sediments deposited during short hiatuses in volcanic activity. Although corresponding to a Large Igneous Province formed in continental environment, it contains subaqueous lava flows, including dominant pillowed flows but also occasional sheet flows. We present a study of the morphology, structure and morphometry of subaqueous lava flows from three sections located at the Marrakech High-Atlas (regions of Aït-Ourir, Jbel Imzar and Oued Lhar-Herissane), as well as an analysis of the sediments, in order to characterize them and to understand their environmental meaning. The analysis of clays by the diffraction method X-ray revealed the presence of illite, mica, phengite, céladonite, talc and small amounts of quartz, hematite, calcite and feldspar, as well as two pairs of interbedded irregular (chlorite Smectite/chlorite-Mica). Fibrous minerals such as sepiolite and palygorskite were not detected. The peperite of Herissane region (Central High Atlas) provided an excellent overview on the factors favoring the magma-sediment interaction. These are the products of a mixture of unconsolidated or poorly consolidated sediments, low permeability with a low viscosity magma. The attempt of dating palynology proved unfortunately without results.

  20. 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 (United States)

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


    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

  1. Additional Observations of Actively Forming Lava Tubes and Associated Structures, Hawaii (United States)

    Greeley, Ronald


    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.

  2. Discrete Fracture Network Modeling and Simulation of Subsurface Transport for the Topopah Springs and Lava Flow Aquifers at Pahute Mesa, FY 15 Progress Report

    Energy Technology Data Exchange (ETDEWEB)

    Makedonska, Nataliia [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Kwicklis, Edward Michael [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Birdsell, Kay Hanson [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Harrod, Jeremy Ashcraft [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Karra, Satish [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)


    This progress report for fiscal year 2015 (FY15) describes the development of discrete fracture network (DFN) models for Pahute Mesa. DFN models will be used to upscale parameters for simulations of subsurface flow and transport in fractured media in Pahute Mesa. The research focuses on modeling of groundwater flow and contaminant transport using DFNs generated according to fracture characteristics observed in the Topopah Spring Aquifer (TSA) and the Lava Flow Aquifer (LFA). This work will improve the representation of radionuclide transport processes in large-scale, regulatory-focused models with a view to reduce pessimistic bounding approximations and provide more realistic contaminant boundary calculations that can be used to describe the future extent of contaminated groundwater. Our goal is to refine a modeling approach that can translate parameters to larger-scale models that account for local-scale flow and transport processes, which tend to attenuate migration.

  3. Textural variations and fragmentation processes in peperite formed between felsic lava flow and wet substrate: An example from the Cretaceous Buan Volcanics, southwest Korea (United States)

    Gihm, Yong Sik; Kwon, Chang Woo


    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

  4. Stratigraphy of amethyst geode-bearing lavas and fault-block structures of the Entre Rios mining district, Paraná volcanic province, southern Brazil

    Directory of Open Access Journals (Sweden)



    Full Text Available The Entre Rios mining district produces a large volume of amethyst geodes in underground mines and is part of the world class deposits in the Paraná volcanic province of South America. Two producing basalt flows are numbered 4 and 5 in the lava stratigraphy. A total of seven basalt flows and one rhyodacite flow are present in the district. At the base of the stratigraphy, beginning at the Chapecó river bed, two basalt flows are Esmeralda, low-Ti type. The third flow in the sequence is a rhyodacite, Chapecó type, Guarapuava subtype. Above the rhyodacite flow, four basalt flows are Pitanga, high-Ti type including the two mineralized flows; only the topmost basalt in the stratigraphy is a Paranapanema, intermediate-Ti type. Each individual flow is uniquely identified from its geochemical and gamma-spectrometric properties. The study of several sections in the district allowed for the identification of a fault-block structure. Blocks are elongated NW and the block on the west side of the fault was downthrown. This important structural characterization of the mining district will have significant consequences in the search for new amethyst geode deposits and in the understanding of the evolution of the Paraná volcanic province.

  5. Mineral resources of the Devil's Garden Lava Bed, Squaw Ridge Lava Bed, and Four Craters Lava Bed Wilderness Study Areas, Lake County, Oregon

    Energy Technology Data Exchange (ETDEWEB)

    Keith, W.J.; King, H.D.; Gettings, M.E. (Geological Survey, Reston, VA (USA)); Johnson, F.L. (US Bureau of Mines (US))


    The Devel's Garden lava Bed, Squaw Ridge Lava Bed, and Four Craters Lava Bed Wilderness Study Areas include approximately 70,940 acres and are underlain entirely by Pleistocene or Holocene lava flows and associated sediments. There is no evidence of hydrothermal alteration in the study areas. No resources were identified in the study areas, but there is low potential for perlite resources in the southern part of the Devil's Garden Lava Bed and the northern half of the Squaw Ridge Lava Bed areas. All three study areas have low potential for geothermal resources and for oil and gas resources.

  6. Effets thermique et hydrothermal de la coulée de basalte triasico-liasique sur les argiles du bassin d'Argana (Maroc)Thermal and hydrothermal effects of Triassic Liassic basalt flow deposition on clays (Agana Basin, Morocco) (United States)

    Daoudi, Lahcen; Pot de Vin, Jean-Luc

    Thermal and hydrothermal effects of Triassic-Liassic basalt flow deposition on sedimentary series of the Argana Basin are responsible for major modifications in detrital clays, until 20 m in depth. It expressed by transformation of detrital smectite to corrensite and moreover to chlorite, and by increasing illite crystallinity. On the 2 m of sediments located immediately under the flow, magnesium-rich hydrothermal fluids have caused precipitation of new mineral phases. To cite this article: L. Daoudi, J.-L. Pot de Vin, C. R. Geoscience 334 (2002) 463-468.

  7. LA-ICP-MS U-Pb ages of pillow lava basalts in southwestern Langshan, Inner Mongolia and their implication%内蒙古狼山西南地区枕状玄武岩LA-ICP-MS锆石U-Pb年龄及意义

    Institute of Scientific and Technical Information of China (English)

    张进; 李锦轶; 刘建峰; 李岩峰; 曲军峰; 张义平


    报道了新近在华北北缘西段狼山地区发现的枕状玄武岩的初步定年工作.前人将其时代定为早古生代.对选自玄武岩的32颗锆石进行了LA-ICP-MS U-Pb定年结果表明,玄武岩的锆石大量为捕获基底的锆石,其年龄和锆石内部结构复杂多样.根据锆石内部特征将其划分为4类,其中的板状锆石被定为玄武岩的自生锆石,年龄为晚古生代末期—早三叠世早期.其余均为来自阿拉善地块基底的锆石,主要为古元古代—新大古代和古生代锆石.狼山晚古生代末期的玄武岩可能产自古亚洲洋封闭后由于岩石圈拆沉导致的伸展环境,该期伸展贯穿华北北缘直至阿拉善地块,暗示华北板块与阿拉善地块至少在晚古生代之前就已经拼合在一起了.%Recent found pillow lava basalts in the southwestern Langshan and its preliminary dating has been reported here. Previous survey had assigned its age at the Early Paleozoic. 32 zircons from pillow lava basalts have been dated using LA-ICP-MS. Most zircons from basalts are captured from the basement, the distribution of ages and internal structures of which are complicated. Four groups of zircons have been distinguished by their internal structures. Among them the tabular zircons have been believed as the autogenetic zircons of pillow lava basalts, the ages of these zircons range from the end of Permian to the Early Triassic. The rest zircons in the samples are all from the Alashan basement, among which Paleoproterozoic and Newarchaeozoic zircons and Paleozoic zircons are most. The latest Late Permian Langshan basalts may developed in the extensional tectonics resulting from the delamination of the lithosphere after the closure of the Paleoasian Ocean, the extension of this period occurred along the whole north margin of the North China Plate including the Alashan block, which means that the Alashan block jointed with the North China Plate at least before the Late Paleozoic.

  8. Aspects of a conceptual groundwater flow model of the Serra Geral basalt aquifer (Sao Paulo, Brazil) from physical and structural geology data (United States)

    Fernandes, Amélia J.; Maldaner, Carlos H.; Negri, Francisco; Rouleau, Alain; Wahnfried, Ingo D.


    A preliminary conceptual model of groundwater flow was developed for the Serra Geral fractured basalt aquifer in order to assess the recharge to the underlying sandstone Guarani Aquifer System, one of the main aquifer systems in Brazil, which supplies water to millions of people. Detailed geological investigations included macroscopic description of the basalt flow units and the underlying sandstone. Petrographic and chemical analyzes were conducted on rock samples from outcrops and from five drilled boreholes. Detailed fracture surveys were accomplished at outcrops to characterize fracture sets and their potential to transmit water in the current tectonic context. Four basalt flows were identified in the Ribeirao Preto area and were named B1, B2, B3 and B4 (from oldest to youngest). The cooling process in flow B3 led to the generation of large sub-horizontal fractures at the contacts B2/B3 and B3-C/B3-E, which are the most transmissive structures. Groundwater flow in the basalt appears to be of the stratabound type because fractures, in general, do not propagate through the basalt vesicular layers, which behave as a regional hydraulic barrier for the vertical groundwater flow. However, it is proposed that the localized, continuous and closely spaced subvertical tectonic fractures, the only features that have the potential to crosscut the vesicular layers and the intertrappe sediments, can vertically connect the sub-horizontal transmissive fractures. Weathering and water seepage, observed in rock exposures, indicate that subvertical NE-trending fractures would be the most transmissive in the Ribeirao Preto area.

  9. Deduction of groundwater flow regime in a basaltic aquifer using geochemical and isotopic data: The Golan Heights, Israel case study (United States)

    Dafny, Elad; Burg, Avi; Gvirtzman, Haim


    SummaryGroundwater flow-paths through shallow-perch and deep-regional basaltic aquifers at the Golan Heights, Israel, are reconstructed by using groundwater chemical and isotopic compositions. Groundwater chemical composition, which changes gradually along flow-paths due to mineral dissolution and water-rock interaction, is used to distinguish between shallow-perched and deep-regional aquifers. Groundwater replenishment areas of several springs are identified based on the regional depletion in rainwater δ18O values as a function of elevation (-0.25‰ per 100 m). Tritium concentrations assist in distinguishing between pre-bomb and post-bomb recharged rainwater. It was found that waters emerging through the larger springs are lower in δ18O than surrounding meteoric water and poor in tritium; thus, they are inferred to originate in high-elevation regions up to 20 km away from their discharge points and at least several decades ago. These results verify the numerically simulated groundwater flow field proposed in a previous study, which considered the geological configuration, water mass balance and hydraulic head spatial distribution.

  10. Experimental Parameters for Wax Modeling of the Deccan Traps Flood Basalt Province (United States)

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


    The Deccan Traps consist of ~1,000,000 km3 of predominantly tholeiitic basaltic lava flows, which cover the western Indian subcontinent. Their eruption occurred over a ~1-3 million year period overlapping with the Cretaceous-Paleogene (K-Pg) boundary and, hence, has been implicated in one of the most significant extinction events in the history of the planet. The extent of environmental impacts caused by flood basalt eruptions is thought to be related, in part, to the amount, species, and timescales of volcanic gases released. Therefore, constraining the effusion rate of Deccan Traps lava flows is fundamental to understanding the K-Pg extinction event. Previous field and experimental work with polyethylene glycol (PEG) wax has shown that effusion rate is a primary factor controlling flow morphology. While sinuous flows and lava domes have been successfully recreated with PEG wax, the two most common morphologies seen in the Deccan Traps (compound and inflated sheet lobes) have not. We used heated PEG-400 wax injected into a tank of chilled water with a peristaltic pump to form experimental eruptions with high flow rate and low viscosity to replicate inflated flow lobes, and low flow rate with higher viscosity for compound flows. Unlike previous experiments, flow rate was varied during a single experiment to examine the effect on flow morphology. The Psi value is used as a scaling parameter to estimate effusion rates for compound and 'simple' inflated flows in the Deccan Traps. When combined with field work for volume estimates of the two flow types, these experiments will provide the best constraint on eruption rates to date.

  11. New argon-argon (40Ar/39Ar) radiometric age dates from selected subsurface basalt flows at the Idaho National Laboratory, Idaho (United States)

    Hodges, Mary K.; Turrin, Brent D.; Champion, Duane E.; Swisher, Carl C.


    In 2011, the U.S. Geological Survey, in cooperation with the U.S. Department of Energy, collected samples for 12 new argon-argon radiometric ages from eastern Snake River Plain olivine tholeiite basalt flows in the subsurface at the Idaho National Laboratory. The core samples were collected from flows that had previously published paleomagnetic data. Samples were sent to Rutgers University for argon-argon radiometric dating analyses.

  12. Additive Construction using Basalt Regolith Fines (United States)

    Mueller, Robert P.; Sibille, Laurent; Hintze, Paul E.; Lippitt, Thomas C.; Mantovani, James G.; Nugent, Matthew W.; Townsend, Ivan I.


    Planetary surfaces are often covered in regolith (crushed rock), whose geologic origin is largely basalt. The lunar surface is made of small-particulate regolith and areas of boulders located in the vicinity of craters. Regolith composition also varies with location, reflecting the local bedrock geology and the nature and efficiency of the micrometeorite-impact processes. In the lowland mare areas (suitable for habitation), the regolith is composed of small granules (20 - 100 microns average size) of mare basalt and volcanic glass. Impacting micrometeorites may cause local melting, and the formation of larger glassy particles, and this regolith may contain 10-80% glass. Studies of lunar regolith are traditionally conducted with lunar regolith simulant (reconstructed soil with compositions patterned after the lunar samples returned by Apollo). The NASA Kennedy Space Center (KSC) Granular Mechanics & Regolith Operations (GMRO) lab has identified a low fidelity but economical geo-technical simulant designated as Black Point-1 (BP-1). It was found at the site of the Arizona Desert Research and Technology Studies (RATS) analog field test site at the Black Point lava flow in adjacent basalt quarry spoil mounds. This paper summarizes activities at KSC regarding the utilization of BP-1 basalt regolith and comparative work with lunar basalt simulant JSC-1A as a building material for robotic additive construction of large structures. In an effort to reduce the import or in-situ fabrication of binder additives, we focused this work on in-situ processing of regolith for construction in a single-step process after its excavation. High-temperature melting of regolith involves techniques used in glassmaking and casting (with melts of lower density and higher viscosity than those of metals), producing basaltic glass with high durability and low abrasive wear. Most Lunar simulants melt at temperatures above 1100 C, although melt processing of terrestrial regolith at 1500 C is not

  13. Shallow Miocene basaltic magma reservoirs in the Bahia de Los Angeles basin, Baja California, Mexico (United States)

    Delgado-Argote, Luis A.; García-Abdeslem, Juan


    The basement in the Bahı´a de Los Angeles basin consists of Paleozoic metamorphic rocks and Cretaceous granitoids. The Neogene stratigraphy overlying the basement is formed, from the base to the top, by andesitic lava flows and plugs, sandstone and conglomeratic horizons, and Miocene pyroclastic flow units and basaltic flows. Basaltic dikes also intrude the whole section. To further define its structure, a detailed gravimetric survey was conducted across the basin about 1 km north of the Sierra Las Flores. In spite of the rough and lineal topography along the foothills of the Sierra La Libertad, we found no evidence for large-scale faulting. Gravity data indicates that the basin has a maximum depth of 120 m in the Valle Las Tinajas and averages 75 m along the gravimetric profile. High density bodies below the northern part of the Sierra Las Flores and Valle Las Tinajas are interpreted to be part of basaltic dikes. The intrusive body located north of the Sierra Las Flores is 2.5 km wide and its top is about 500 m deep. The lava flows of the top of the Sierra Las Flores, together with the distribution of basaltic activity north of this sierra, suggests that this intrusive body continues for 20 km along a NNW-trending strike. Between the sierras Las Flores and Las Animas, a 0.5-km-wide, 300-m-thick intrusive body is interpreted at a depth of about 100 m. This dike could be part of the basaltic activity of the Cerro Las Tinajas and the small mounds along the foothills of western Sierra Las Animas. The observed local normal faulting in the basin is inferred to be mostly associated with the emplacement of the shallow magma reservoirs below Las Flores and Las Tinajas.

  14. Geochemistry of the lava and its implications in Musicians Seamounts

    Institute of Scientific and Technical Information of China (English)

    LI Chuanshun; PAN Yucheng; LI Anchun; Rodey Batiza


    Chemical and isotopic data of the lava samples dredged in the southern Bach Ridge and the northern Italian Ridge of the Musicians Seamounts province, northeast of Hawaii. Although most of the samples analyzed are generally altered, a few are fresh. The latter exhibits similar geochemical and isotopic characteristics to normal MORB (Mid-Ocean Ridge Basalts). There are systematic geochemical trends from hotspot to mid-ocean ridge in the province. Incompatible element and isotopic variations suggest that the flow field had at least two distinct parental magmas, one with higher and one with lower MgO concentrations. The two parental magmas could be related by a magma mixing model. The major and trace element modeling shows that the two parental magmas could not have been produced by different degrees of melting of a homogeneous mantle source, but they are consistent with melting of a generally depleted mantle containing variable volumes of embedded enriched heterogeneity enriched interbeds.

  15. Evolution of Lava Sheets for LIPs: Types of Local and Regional Trends (United States)

    Rakhmenkulova, I. F.; Sharapov, V. N.


    The North-Atlantic Igneous Province (NAIP), the Permian-Triassic traps of the Siberian Platform (SP), and the volcanic shields of the Hawaiian Ridge can be regarded as the examples of local and regional trends for lava sheets evolution of LIPs. Complex statistical analysis for distribution functions of petrogenic and trace components showed that cyclicity and spatial asymmetry for melt compositions are typical for all lava sheets of LIPs. NAIP has the following features: 1) the formation of continental swell and its rifting; 2) the oceanic basin formation as a system of open basins at the east and the opening of the Central Atlantic to the north with the transverse volcanic zone of the Ferraro Ridge; 3) quick opening of the oceanic basin with the formation and accretion of lava sheet in the centre of the spreading zone (MOR). At the western NAIP part, during the sheet breakage, magnesian melts were forming, in the east - 'typical' trap tholeiitic association with thick lava profiles; oceanic part of the system contains various oceanic basalts. Iceland lava sheet passed through at least three subsequent formation stages with typical petrochemical igneous rock complexes. There are local petrochemical trends in the Iceland sheet: as the basalt crust thickens, acid melt amounts increase. The Permian-Triassic SP traps at the southern part of the Khatanga Rift (where the province started to develop spatially) have the following zones: layered profiles of tuffaceous rocks in the Tunguska Syncline, with various quantities of lava flows in the upper part of the profiles; to the south, within the holes between the net of fissure and central lava-breccia volcanic structures, reloaded tuff material is located; more to the south this structural zone changes to swarms of dyke-diatreme structures having typical near-vent depressions. The explosive coefficient within these zones increases from the north to the south. In the western part of trap zone there is a petrochemical zoning


    Institute of Scientific and Technical Information of China (English)

    赵勇伟; 樊祺诚; 李霓; 刘贵; 张柳毅


    Based on detailed field investigation, three lava flow styles are identified in the Dayingshan, Maanshan and Heikongshan in the volcanic field of Tengchong: pipe flow, inflated flow and laminar flow. Lava flows of Dayingshan are characterized by pipe flow. Heat lost gradually increased from the core to the edge of the flow pipe, resulting in lava consolidating gradually from the surface to the core. Lava of Maanshan is dominated by plane pahoehoe inflated by aa. The lava,in high temperature,was inflated into the lava tunnel as liquid-gas mixing phase, which generated aa. Heikongshan is featured by typical aa lava flow in the proximal phase and middle phase from the vent. The high-temperature plastic lava carried breccias on its top when advancing in a state of laminar flow,forming typical aa lava flow sections with breccias on the top and bottom and dense lava in the middle. Tn the distal phase,the lava flow formed numerous strip-shaped uplifts of breccias.%对腾冲打鹰山、马鞍山和黑空山的熔岩流进行详细地质勘察,发现存在3类熔岩流动方式:管状流动、“底侵”式流动和层状流动.管状流动出现于打鹰山熔岩中.熔岩管道中的温度由核心向表层递减,当表层冷却固结时,管道中的塑性熔岩继续前进,最终由表及里逐渐固结.马鞍山火山熔岩为渣状熔岩“底侵”结壳熔岩流动.结壳熔岩由表层向底部增生,早期熔岩固结形成结壳熔岩,晚期高温气液混合相的熔岩注入结壳熔岩之下的通道,最终固结形成渣状熔岩.黑空山熔岩为渣状熔岩层状流动.熔岩流顶部自碎形成的渣块在底部塑性致密熔岩的驼动下流动,在火口近源和中源形成顶部和底部都是角砾的渣状熔岩,在熔岩流的远端尽头,形成垂直于熔岩流动方向的条带状隆起.

  17. The structural stability of lunar lava tubes (United States)

    Blair, David M.; Chappaz, Loic; Sood, Rohan; Milbury, Colleen; Bobet, Antonio; Melosh, H. Jay; Howell, Kathleen C.; Freed, Andrew M.


    Mounting evidence from the SELENE, LRO, and GRAIL spacecraft suggests the presence of vacant lava tubes under the surface of the Moon. GRAIL evidence, in particular, suggests that some may be more than a kilometer in width. Such large sublunarean structures would be of great benefit to future human exploration of the Moon, providing shelter from the harsh environment at the surface-but could empty lava tubes of this size be stable under lunar conditions? And what is the largest size at which they could remain structurally sound? We address these questions by creating elasto-plastic finite element models of lava tubes using the Abaqus modeling software and examining where there is local material failure in the tube's roof. We assess the strength of the rock body using the Geological Strength Index method with values appropriate to the Moon, assign it a basaltic density derived from a modern re-analysis of lunar samples, and assume a 3:1 width-to-height ratio for the lava tube. Our results show that the stability of a lava tube depends on its width, its roof thickness, and whether the rock comprising the structure begins in a lithostatic or Poisson stress state. With a roof 2 m thick, lava tubes a kilometer or more in width can remain stable, supporting inferences from GRAIL observations. The theoretical maximum size of a lunar lava tube depends on a variety of factors, but given sufficient burial depth (500 m) and an initial lithostatic stress state, our results show that lava tubes up to 5 km wide may be able to remain structurally stable.

  18. A comparison of Thellier-type and multispecimen paleointensity determinations on Pleistocene and historical lava flows from Lanzarote (Canary Islands, Spain) (United States)

    Calvo-Rathert, Manuel; Morales-Contreras, Juan; Carrancho, Ángel; Goguitchaichvili, Avto


    Sixteen Miocene, Pleistocene, and historic lava flows have been sampled in Lanzarote (Canary Islands) for paleointensity analysis with both the Coe and multispecimen methods. Besides obtaining new data, the main goal of the study was the comparison of paleointensity results determined with two different techniques. Characteristic Remanent Magnetization (ChRM) directions were obtained in 15 flows, and 12 were chosen for paleointensity determination. In Thellier-type experiments, a selection of reliable paleointensity determinations (43 of 78 studied samples) was performed using sets of criteria of different stringency, trying to relate the quality of results to the strictness of the chosen criteria. Uncorrected and fraction and domain-state corrected multispecimen paleointensity results were obtained in all flows. Results with the Coe method on historical flows either agree with the expected values or show moderately lower ones, but multispecimen determinations display a large deviation from the expected result in one case. No relation can be detected between correct or anomalous results and paleointensity determination quality or rock-magnetic properties. However, results on historical flows suggest that agreement between both methods could be a good indicator of correct determinations. Comparison of results obtained with both methods on seven Pleistocene flows yields an excellent agreement in four and disagreements in three cases. Pleistocene determinations were only accepted if either results from both methods agreed or a result was based on a sufficiently large number (n > 4) of individual Thellier-type determinations. In most Pleistocene flows, a VADM around 5 × 1022 Am2 was observed, although two flows displayed higher values around 9 × 1022 Am2.

  19. 基于GPU的元胞自动机熔岩流动模拟%Lava flow simulation in cellular automata based on GPU

    Institute of Scientific and Technical Information of China (English)

    高超; 孟宪海; 李吉刚; 杨钦


    为解决基于元胞自动机进行熔岩流动模拟的计算效率问题,提出一种应用在元胞自动机上的GPU并行计算方法。将元胞自动机中每一个方形网格映射到GPU的一个逻辑计算单元上,通过并行计算,提高模拟的效率,解决传统串行计算方法的不足,使模拟达到实时性。模拟结果表明,在元胞自动机的物理模型理论基础上,用GPU并行计算进行加速,在模拟效果和时间效率上均取得了良好的效果。%To solve the computing efficiency problem of lava flow simulation based on cellular automata ,a GPU parallel compu‐ting method applied to cellular automata was proposed .Each square mesh in cellular automata was mapped to each core in the GPU .Through GPU parallel computing ,the efficiency of real‐time simulation was improved ,which solved the deficiency of tra‐ditional serial computing .The result demonstrates that lava flow simulation in cellular automata ,with the combination of the GPU parallel computing ,can achieve a high computing efficiency and a better simulation performance .

  20. The Late Pliocene mafic lavas from the Camusú Aike volcanic field (˜50°S, Argentina): Evidence for geochemical variability in slab window magmatism (United States)

    D'Orazio, M.; Innocenti, F.; Manetti, P.; Haller, M. J.; Di Vincenzo, G.; Tonarini, S.


    The Camusú Aike volcanic field (CAVF), part of the discontinuous N-S-trending belt of Cenozoic mafic lava formations that occur in a backarc position along extra-Andean Patagonia, is located in southern Patagonia (˜50°S, Santa Cruz province), approximately 70 km east of the extensive Meseta de las Vizcachas and just south of the upper Río Santa Cruz valley. The CAVF volcanics cover a surface of ˜200 km 2 and occur mainly as lava flows and scoria cones. They are subdivided into two groups: Group I volcanics are high-TiO 2, low-Mg# olivine-hypersthene-normative basalts and trachybasalts that erupted at about 2.9 Ma; Group II lavas are much less abundant, more primitive basaltic andesites that erupted at about 2.5 Ma. Both groups show a within-plate geochemical signature, though it is more marked in Group I lavas. The main geochemical characteristics, age, and location of CAVF volcanics are consistent with the slab window opening model proposed by different authors for the genesis of the Miocene-Recent mafic magmatism of Patagonia south of 46.5°S. The whole-rock geochemical and Sr-Nd isotope features of Group I lavas ( 87Sr/ 86Sr=0.7035-0.7037; 143Nd/ 144Nd=0.51288-0.51291) indicate a genetic link between these lavas and the primitive basalts in southernmost Patagonia (Pali Aike volcanic field and Estancia Glencross area), which have been interpreted as melting products of an isotopically depleted asthenosphere. The relatively evolved compositions of the erupted Group I magmas are modeled by a polybaric crystal fractionation process without significant involvement of crustal contamination. The more primitive Group II lavas are strongly depleted in incompatible elements, have slightly higher (LREE+Ba+Th+U)/HFSE ratios, and have more enriched Sr-Nd isotope compositions ( 87Sr/ 86Sr≈0.7039; 143Nd/ 144Nd≈0.51277) that are more akin to the Patagonian basalts farther to the north. The most likely explanation for the geochemical features of Group II lavas is the

  1. Absolute paleointensity determinations by using of conventional double-heating and multispecimen approaches on a Pliocene lava flow sequence from the Lesser Caucasus (United States)

    Goguitchaichvili, Avto; Caccavari, Ana; Calvo-Rathert, Manuel; Morales, Juan; Solano, Miguel Cervantes; Vashakidze, Goga; Huaiyu, He; Vegas, Néstor


    We report 28 successful Thellier type absolute geomagnetic paleointensity determinations from a Pleistocene lava sequence composed of 39 successive flows in the Djavakheti Highland (Lesser Caucasus, Georgia). Additionally, multispecimen technique provided the estimation of geomagnetic field strength for 12 independent cooling units. Paleointensity studies were performed using both Thellier type double heating and multispecimen techniques. Samples selection was mainly based on uni-vectorial remanent magnetization, thermal stability and domain size of the samples. Flow-mean Thellier paleointensity values range from 16.3 ± 5.2 to 71.0 ± 0.3 μT, while intensities obtained using multispecimen approach vary from17.2 ± 2.3 to 69.3 ± 7.9 μT. One of the flows is located near a possible discontinuity in the sequence and yields a rather low Thellier absolute intensity (16.3 ± 5.2) suggesting a transitional regime and the onset of the Matuyama-Olduvai polarity transition, which does not appear on the directional record. Multispecimen paleointensities from the same flow, however, yield higher, close to present day values which makes untenable the hypothesis of occurrence of transitional field. Thus the whole sequence was emplaced in a short time between the Olduvai chron and 1.73 ± 0.03 Ma, as suggested by available radiometric and paleomagnetic data (Caccavari et al., 2014).

  2. Multiphase Alkaline Basalts of Central Al-Haruj Al-Abyad of Libya: Petrological and Geochemical Aspects

    Directory of Open Access Journals (Sweden)

    Abdel-Aal M. Abdel-Karim


    Full Text Available Al-Haruj basalts that represent the largest volcanic province in Libya consist of four lava flow phases of varying thicknesses, extensions, and dating. Their eruption is generally controlled by the larger Afro-Arabian rift system. The flow phases range from olivine rich and/or olivine dolerites to olivine and/or normal basalts that consist mainly of variable olivine, clinopyroxene, plagioclase, and glass. Olivine, plagioclase, and clinopyroxene form abundant porphyritic crystals. In olivine-rich basalt and olivine basalt, these minerals occur as glomerophyric or seriate clusters of an individual mineral or group of minerals. Groundmass textures are variably intergranular, intersertal, vitrophyric, and flow. The pyroclastic, clastogenic flows and/or ejecta of the volcanic cones show porphyritic, vitrophric, pilotaxitic, and vesicular textures. They are classified into tholeiite, alkaline, and olivine basalts. Three main groups are recorded. Basalts of phase 1 are generated from tholeiitic to alkaline magma, while those of phases 3 and 4 are derived from alkaline magma. It is proposed that the tholeiitic basalts represent prerift stage magma generated by higher degree of partial melting (2.0–3.5% of garnet-peridotite asthenospheric mantle source, at shallow depth, whereas the dominant alkaline basalts may represent the rift stage magma formed by low degree of partial melting (0.7–1.5% and high fractionation of the same source, at greater depth in an intra-continental plate with OIB affinity. The melt generation could be also attributed to lithosphere extension associated with passive rise of variable enriched mantle.

  3. Determination of eruption temperature of Io's lavas using lava tube skylights (United States)

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


    Determining the eruption temperature of Io's dominant silicate lavas would constrain Io's present interior state and composition. We have examined how eruption temperature can be estimated at lava tube skylights through synthesis of thermal emission from the incandescent lava flowing within the lava tube. Lava tube skylights should be present along Io's long-lived lava flow fields, and are attractive targets because of their temporal stability and the narrow range of near-eruption temperatures revealed through them. We conclude that these skylights are suitable and desirable targets (perhaps the very best targets) for the purposes of constraining eruption temperature, with a 0.9:0.7-μm radiant flux ratio ≤6.3 being diagnostic of ultramafic lava temperatures. Because the target skylights may be small - perhaps only a few m or 10 s of m across - such observations will require a future Io-dedicated mission that will obtain high spatial resolution (lava fountains or roiling lava lakes, where accurate determination of surface temperature distribution requires simultaneous or near-simultaneous (< 0.1 s) observations at different wavelengths, skylight thermal emission data are superior for the purposes of temperature derivation, as emission is stable on much longer time scales (minutes, or longer), so long as viewing geometry does not greatly change during that time.

  4. Isotopic and trace element constraints on the petrogenesis of lavas from the Mount Adams volcanic field, Washington (United States)

    Jicha, B.R.; Hart, G.L.; Johnson, C.M.; Hildreth, W.; Beard, B.L.; Shirey, S.B.; Valley, J.W.


    Strontium, Nd, Pb, Hf, Os, and O isotope compositions for 30 Quaternary lava flows from the Mount Adams stratovolcano and its basaltic periphery in the Cascade arc, southern Washington, USA indicate a major component from intraplate mantle sources, a relatively small subduction component, and interaction with young mafic crust at depth. Major- and trace-element patterns for Mount Adams lavas are distinct from the rear-arc Simcoe volcanic field and other nearby volcanic centers in the Cascade arc such as Mount St. Helens. Radiogenic isotope (Sr, Nd, Pb, and Hf) compositions do not correlate with geochemical indicators of slab-fluids such as (Sr/P)n and Ba/Nb. Mass-balance modeling calculations, coupled with trace-element and isotopic data, indicate that although the mantle source for the calc-alkaline Adams basalts has been modified with a fluid derived from subducted sediment, the extent of modification is significantly less than what is documented in the southern Cascades. The isotopic and trace-element compositions of most Mount Adams lavas require the presence of enriched and depleted mantle sources, and based on volume-weighted chemical and isotopic compositions for Mount Adams lavas through time, an intraplate mantle source contributed the major magmatic mass of the system. Generation of basaltic andesites to dacites at Mount Adams occurred by assimilation and fractional crystallization in the lower crust, but wholesale crustal melting did not occur. Most lavas have Tb/Yb ratios that are significantly higher than those of MORB, which is consistent with partial melting of the mantle in the presence of residual garnet. ??18O values for olivine phenocrysts in Mount Adams lavas are within the range of typical upper mantle peridotites, precluding involvement of upper crustal sedimentary material or accreted terrane during magma ascent. The restricted Nd and Hf isotope compositions of Mount Adams lavas indicate that these isotope systems are insensitive to crustal

  5. Isotopic and trace element constraints on the petrogenesis of lavas from the Mount Adams volcanic field, Washington (United States)

    Jicha, Brian R.; Hart, Garret L.; Johnson, Clark M.; Hildreth, Wes; Beard, Brian L.; Shirey, Steven B.; Valley, John W.


    Strontium, Nd, Pb, Hf, Os, and O isotope compositions for 30 Quaternary lava flows from the Mount Adams stratovolcano and its basaltic periphery in the Cascade arc, southern Washington, USA indicate a major component from intraplate mantle sources, a relatively small subduction component, and interaction with young mafic crust at depth. Major- and trace-element patterns for Mount Adams lavas are distinct from the rear-arc Simcoe volcanic field and other nearby volcanic centers in the Cascade arc such as Mount St. Helens. Radiogenic isotope (Sr, Nd, Pb, and Hf) compositions do not correlate with geochemical indicators of slab-fluids such as (Sr/P) n and Ba/Nb. Mass-balance modeling calculations, coupled with trace-element and isotopic data, indicate that although the mantle source for the calc-alkaline Adams basalts has been modified with a fluid derived from subducted sediment, the extent of modification is significantly less than what is documented in the southern Cascades. The isotopic and trace-element compositions of most Mount Adams lavas require the presence of enriched and depleted mantle sources, and based on volume-weighted chemical and isotopic compositions for Mount Adams lavas through time, an intraplate mantle source contributed the major magmatic mass of the system. Generation of basaltic andesites to dacites at Mount Adams occurred by assimilation and fractional crystallization in the lower crust, but wholesale crustal melting did not occur. Most lavas have Tb/Yb ratios that are significantly higher than those of MORB, which is consistent with partial melting of the mantle in the presence of residual garnet. δ 18O values for olivine phenocrysts in Mount Adams lavas are within the range of typical upper mantle peridotites, precluding involvement of upper crustal sedimentary material or accreted terrane during magma ascent. The restricted Nd and Hf isotope compositions of Mount Adams lavas indicate that these isotope systems are insensitive to crustal

  6. 基性熔岩火山地层单元类型、特征及其储层意义%Types, characteristics and reservoir significance of basic lava flow units

    Institute of Scientific and Technical Information of China (English)

    衣健; 唐华风; 王璞珺; 高有峰; 赵然磊


    Based on profile measurements, the observation of the core samples, the interpretation of detection logging and seismic profiles, three typical fields and wells in Songliao Basin were chosen, and the types, the characteristics and the stacking patterns of the volcanic units were studied. The results show that the basic lava volcanic units can be formed by the diagenesis of solidification with cooling, and can be divided into four types according to their external morphology:the braid lava flow units, the fan-like lava flow units, the tabular lava flow units, and the tube lava flow units. The first three of these lava flow units are formed by the lava effusion on the ground, and the tube lava flow units are formed by the lava flowing along the buried tube underground. The internal structure of the lava flow units can be characterized by the vesicular zones. The braid lava flow units are divided into three parts:the rich vesicular zone on the tope, the spare vesicular zone in the middle, and the base vesicular zone at the base. The fan-like lava flow units have an autoclastic breccia zone on the rich vesicular zone, and a thin dense zone under the spare vesicular zone. The tabular lava flow units have a thick dense zone under the spare vesicular zone. The tube lava flow consists of a loop columnar zone in the outer ring and an autoclastic breccia core. The volcanostratigraphy is built by the stacking of volcanic units, and the spatial and temporal distribution of the lithology, and facies and reservoir are directly controlled by the shape and stacking patterns of lava flow units, and make up three distribution modes of reservoirs: the layered, the quasi layered and the mixed-lenticular. Thus this study may provide theoretic foundation for the final target attempt to define the fine characterization of the volcanostratigraphy using outcrop, well and seismic data.%为了探索基性熔岩的火山地层单元类型、特征与叠置关系,精选中国东北3个具

  7. Magnetic links among lava flows, tuffs and the underground plumbing system in a monogenetic volcano, derived from magnetics and paleomagnetic studies (United States)

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


    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.

  8. An analysis of Apollo lunar soil samples 12070,889, 12030,187, and 12070,891: Basaltic diversity at the Apollo 12 landing site and implications for classification of small-sized lunar samples (United States)

    Alexander, Louise; Snape, Joshua F.; Joy, Katherine H.; Downes, Hilary; Crawford, Ian A.


    Lunar mare basalts provide insights into the compositional diversity of the Moon's interior. Basalt fragments from the lunar regolith can potentially sample lava flows from regions of the Moon not previously visited, thus, increasing our understanding of lunar geological evolution. As part of a study of basaltic diversity at the Apollo 12 landing site, detailed petrological and geochemical data are provided here for 13 basaltic chips. In addition to bulk chemistry, we have analyzed the major, minor, and trace element chemistry of mineral phases which highlight differences between basalt groups. Where samples contain olivine, the equilibrium parent melt magnesium number (Mg#; atomic Mg/[Mg + Fe]) can be calculated to estimate parent melt composition. Ilmenite and plagioclase chemistry can also determine differences between basalt groups. We conclude that samples of approximately 1-2 mm in size can be categorized provided that appropriate mineral phases (olivine, plagioclase, and ilmenite) are present. Where samples are fine-grained (grain size lava flow diversity and petrological significance.

  9. Contrasting Sr isotope ratios in plagioclase from different formations of the mid-Miocene Columbia River Basalt Group (United States)

    Starkel, W. A.; Wolff, J.; Eckberg, A.; Ramos, F.


    Many early Columbia River Basalt flows of the Steens and Imnaha Formations are characterized by abundant, texturally complex, coarse plagioclase phenocrysts. In Imnaha lavas, the feldspars typically have more radiogenic 87Sr/86Sr than whole rock and matrix, and may exhibit complex isotopic zoning that is not correlated with An content. Imnaha plagioclase grains are interpreted as variably-contaminated crystals produced when high-crystallinity mid-crustal basaltic intrusions exchanged interstitial melt with adjacent partly-melted crustal rock; this isotopically variable debris was then remobilized by subsequent intrusion of mantle-derived basalt and brought to the surface as an isotopically heterogeneous mixture. In contrast, plagioclase grains in the texturally very similar Steens lavas are isotopically near-homogeneous and 87Sr/86Sr is not significantly displaced from that of the bulk rock. This is consistent with magma- crust interaction at low degrees of crustal melting during the early stages of the Columbia River flood basalt episode, where Steens and Imnaha lavas were erupted from distinct magma systems hosted by different types of crust that exerted different degrees of isotopic leverage on the mantle-derived magmas [1]. Thermal input to the Steens system declined at the same time as the Imnaha magmatic flux increased to ultimately produce the huge outpouring of Grande Ronde lavas, which are mixtures of mantle- and crust-derived liquids, the latter produced during high degrees of crustal melting during the time of peak magmatic flux. [1] Wolff et al. (2008) Nature Geoscience 1, 177-180.

  10. Eruption styles of Quaternary basalt in the southern Sierra Nevada Kern Plateau recorded in outcrop and mineral-scale stratigraphies (United States)

    Browne, B. L.; Becerra, R. A.


    The Kern River Plateau in the southern Sierra Nevada contains Quaternary basalt (~0.1 km3) and rhyolite (~2 km3) that ascended through ~30 km of Mesozoic granitic crust. Basaltic vents include from oldest to youngest: Little Whitney Cone, Tunnel and South Fork Cones, and unglaciated Groundhog Cone. Little Whitney Cone is a 120-m-high pile of olivine-CPX-phyric scoria overlying two columnar jointed lava flows extending to the south and east. Tunnel Cone formed through a Hawaiian style eruption along a 400-m-long north-south trending fissure that excavated at least three 25-65-m-wide craters. Crater walls up to 12 meters high are composed of plagioclase-olivine-phyric spatter-fed flows that dip radially away from the crater center and crumble to form steep unconsolidated flanks. South Fork Cone is a 170-m-tall pile of plagioclase-olivine-phyric scoria that formed as a result of Strombolian to violent Strombolian eruptions. It overlies the South Fork Cone lava, the largest lava flow of the Kern Plateau (~0.05 km3), which flowed 7.5 km west into the Kern River Canyon. Scoria and ash fall deposits originating from South Fork Cone are found up to 2 km from the vent. Groundhog Cone is a 140-m-tall cinder and spatter cone breached on the north flank by a 0.03 km3 lava flow that partially buried the South Fork Cone lava and extends 5 km west to Kern River Canyon. Trends in mineral assemblage, texture, composition, and xenocryst abundance exist as a function of eruption style. Scoria and spatter deposits typically have (1) elevated olivine/plagioclase ratios, (2) oscillatory zoned (An63-An72) plagioclase phenocrysts surrounded by unzoned rims and (3) abundant xenocrysts, where up to 20% of plagioclase >200 micron diameter in some samples are granitoid xenocrysts with resorbed and/or reacted textures overprinted by abrupt compositional changes. In contrast, lava flow samples have (1) reduced olivine/plagioclase ratios and (2) plagioclase aggregates with oscillatory zoned

  11. Stratigraphy of the Basalt Flows of the Formação Serra Geral (Ribeirão Preto - SP Based on Physical Geology, Petrography and Geochemistry

    Directory of Open Access Journals (Sweden)

    Amélia João Fernandes


    Full Text Available The study of the physical geology and geochemistry of the basalts of Ribeirão Preto was part of a hydrogeologicalresearch that aimed at investigating the recharge of the Guarani Aquifer System (SAG through the basalts of the SerraGeral Aquifer (ASG, a project shortly named FRATASG. In addition to hydrogeological methods, the research demandeda detailed geological investigation, which is essential for the elaboration of conceptual models of groundwater circulationin complex aquifers, as is the case of the fractured basalts of the ASG. Thus, the study encompassed field work for thedescription of the macroscopic aspects and relationships among the basalts and the underlying sandstones, as well as, rocksampling and petrographic and chemical analysis. Furthermore, the use of lithologic logs of five wells drilled in FRATASG project was essential for the establishment of the subsurface basalt stratigraphy. The study concluded that, in Bonfim Paulista region,there are four basalt floods, namely B1, B2, B3 and B4. The B4 occurrence is very restricted as it was largely eroded. B1 and B2average thicknesses are 45 and 60 m, respectively. All four basalts are of sheet-like lobe types and were probably emplaced by inflation,B1 being the one that presents more evidence in that respect. B1 presents a thick vesicular top and, as well as B2, can show more thanone vesicular layer at the top. Columnar joints were observed in B2 and B3 and are more remarkable in B3, where a lower colonnadetier (B3-C is overlain by an entablature layer (B3-E. B3 is the thickest flow (75 to 105 m and contains irregular and roughly roundpatches of hydraulic breccia in B3-C or along sub-horizontal fractures that allow the circulation of fluids (groundwater at the present. The chemical composition of B3 is homogeneous and very different from B1 and B2 with regard to several oxides (Al2O3, P2O5, Fe2O3, TiO2 e MgO and trace elements (Ni, Zn, Cu, Y. B1 is very different from B2 with regard

  12. Pliocene Basaltic Volcanism in The East Anatolia Region (EAR), Turkey (United States)

    Oyan, Vural; Özdemir, Yavuz; Keskin, Mehmet


    East Anatolia Region (EAR) is one of the high Plateau which is occurred with north-south compressional regime formed depending on continent-continent collision between Eurasia and Arabia plates (Şengör and Kidd, 1979). Recent studies have revealed that last oceanic lithosphere in the EAR have completely depleted to 20 million years ago based on fission track ages (Okay et al. 2010). Our initial studies suggest that extensively volcanic activity in the EAR peaked in the Pliocene and continued in the same productivity throughout Quaternary. Voluminous basaltic lava plateaus and basaltic lavas from local eruption centers occurred as a result of high production level of volcanism during the Pliocene time interval. In order to better understand the spatial and temporal variations in Pliocene basaltic volcanism and to reveal isotopic composition, age and petrologic evolution of the basaltic volcanism, we have started to study basaltic volcanism in the East Anatolia within the framework of a TUBITAK project (project number:113Y406). Petrologic and geochemical studies carried out on the Pliocene basaltic lavas indicate the presence of subduction component in the mantle source, changing the character of basaltic volcanism from alkaline to subalkaline and increasing the amount of spinel peridotitic melts (contributions of lithospheric mantle?) in the mantle source between 5.5-3.5 Ma. FC, AFC and EC-AFC modelings reveal that the while basaltic lavas were no or slightly influenced by crustal contamination and fractional crystallization, to more evolved lavas such as bazaltictrachyandesite, basalticandesite, trachybasalt might have been important processes. Results of our melting models and isotopic analysis data (Sr, Nd, Pb, Hf, 18O) indicate that the Pliocene basaltic rocks were derived from both shallow and deep mantle sources with different melting degrees ranging between 0.1 - 4 %. The percentage of spinel seems to have increased in the mantle source of the basaltic

  13. Flow in the western Mediterranean shallow mantle: Insights from xenoliths in Pliocene alkali basalts from SE Iberia (eastern Betics, Spain) (United States)

    Hidas, Károly; Konc, Zoltán.; Garrido, Carlos J.; Tommasi, Andréa.; Vauchez, Alain; Padrón-Navarta, José Alberto; Marchesi, Claudio; Booth-Rea, Guillermo; Acosta-Vigil, Antonio; Szabó, Csaba; Varas-Reus, María. Isabel; Gervilla, Fernando


    Mantle xenoliths in Pliocene alkali basalts of the eastern Betics (SE Iberia, Spain) are spinel ± plagioclase lherzolite, with minor harzburgite and wehrlite, displaying porphyroclastic or equigranular textures. Equigranular peridotites have olivine crystal preferred orientation (CPO) patterns similar to those of porphyroclastic xenoliths but slightly more dispersed. Olivine CPO shows [100]-fiber patterns characterized by strong alignment of [100]-axes subparallel to the stretching lineation and a girdle distribution of [010]-axes normal to it. This pattern is consistent with simple shear or transtensional deformation accommodated by dislocation creep. One xenolith provides evidence for synkinematic reactive percolation of subduction-related Si-rich melts/fluids that resulted in oriented crystallization of orthopyroxene. Despite a seemingly undeformed microstructure, the CPO in orthopyroxenite veins in composite xenoliths is identical to those of pyroxenes in the host peridotite, suggesting late-kinematic crystallization. Based on these observations, we propose that the annealing producing the equigranular microstructures was triggered by melt percolation in the shallow subcontinental lithospheric mantle coeval to the late Neogene formation of veins in composite xenoliths. Calculated seismic properties are characterized by fast propagation of P waves and polarization of fast S waves parallel to olivine [100]-axis (stretching lineation). These data are compatible with present-day seismic anisotropy observations in SE Iberia if the foliations in the lithospheric mantle are steeply dipping and lineations are subhorizontal with ENE strike, implying dominantly horizontal mantle flow in the ENE-WSW direction within vertical planes, that is, subparallel to the paleo-Iberian margin. The measured anisotropy could thus reflect a lithospheric fabric due to strike-slip deformation in the late Miocene in the context of WSW tearing of the subducted south Iberian margin

  14. Modeling the lava flow of Changbaishan Volcano, China based on kinematic thermo-rheological model%基于热流变运动学模型的长白山熔岩流数值模拟

    Institute of Scientific and Technical Information of China (English)

    潘波; 许建东; 林旭东; 万园; 于红梅


    The kinematic thermo-rheological model is a means of modeling the complicated flowing process of lava flow. The model can be used to determine the flow velocity, temperature variation and flowing distance of the lava flow through the calculation of relief and thermal system. In this paper, the Qixiangzhan period pantellerite lava flow in Changbaishan volcano has been modeled by using this model on the basis of relevant parameters obtained from field investigation on the lava flow. The result of modeling shows that the variation trend of flow velocity is consistent well with the variation trend of topographic slope, but with increasing viscosity during flowing process, the effect of topography becomes less important. In heat budget terms, the radiation heat and crystallization heat of microlites are the most significant heat loss and heat gain in the lava flow, respectively. The final flowing distance of the Qixiangzhan period pantellerite lava flow is calculated by the model to be 5. 17 km, approximate to the actual length of 5. 4 km. The consistency between the modeling results and geologic observation data indicates the feasibility and reliability of the modeling method. In addition, this study may provide a reference to the geologic study of lava flow, as well as a new train of thought and method of assessing lava flow hazard.%热流变运动学模型是熔岩流复杂流动过程模拟的一种方法,其通过热量系统和地形的计算来模拟熔岩流的流动速度、温度变化和流动距离等.本文以气象站期碱流岩的野外调查数据为依据,应用该模型对其进行模拟研究.通过对模拟结果的分析发现,速度变化趋势与地形坡度变化趋势一致,但随着流动过程中黏度的增大,地形影响作用逐渐减小.在热量系统中,辐射热和微晶结晶热分别为熔岩流流动中最多的热损失和热增加.气象站期碱流岩模拟计算的最终流动距离为5.17 km,这与实测约5.4 km的长度相

  15. Using thermal remanent magnetisation (TRM) to distinguish block and ash flow and debris flow deposits, and to estimate their emplacement temperature: 1991-1995 lava dome eruption at Mt. Unzen Volcano, Japan (United States)

    Uehara, D.; Cas, R. A. F.; Folkes, C.; Takarada, S.; Oda, H.; Porreca, M.


    The 1991-1995 Mt. Unzen eruption (Kyushu, Japan) produced 13 lava domes, approximately 9400 block and ash pyroclastic flows (BAF) resulting from lava dome collapse events and syn- and post-dome collapse debris flow (DF) events. In the field, it can be very difficult to distinguish from field facies characteristics which deposits are primary hot BAF, cold BAF or rock avalanche, or secondary DF deposits. In this study we use a combination of field observations and thermal remanent magnetisation (TRM) analysis of juvenile, lava dome derived clasts from seven deposits of the 1991-1995 Mt. Unzen eruption in order to distinguish between primary BAF deposits and secondary DF deposits and to determine their emplacement temperature. Four major TRM patterns were identified: (1) Type I: clasts with a single magnetic component oriented parallel to the Earth's magnetic field at time and site of emplacement. This indicates that these deposits were deposited at very high temperature, between the Curie temperature of magnetite (~ 540 °C) and the glass transition temperature of the lava dome (~ 745 °C). These clasts are found in high temperature BAF deposits. (2) Type II: clasts with two magnetic components of magnetisation. The lower temperature magnetic components are parallel to the Earth's magnetic field at time of the Unzen eruption. Temperature estimations for these deposits can range from 80 to 540 °C. We found this paleomagnetic behaviour in moderate temperature BAF or warm DF deposits. (3) Type III: clasts with three magnetic components, with a lower temperature component oriented parallel to the Earth's magnetic field at Unzen. The individual clast temperatures estimated for this kind of deposit are usually less than 300 °C. We interpret this paleomagnetic behaviour as the effect of different thermal events during their emplacement history. There are several interpretations for this paleomagnetic behaviour including remobilisation of moderate temperature BAF, warm DF

  16. A Plagioclase Ultraphyric Basalt group in the Neogene flood basalt piles of eastern Iceland: Volcanic architecture and mode of emplacement (United States)

    Oskarsson, B. V.; Riishuus, M. S.


    3D photogrammetry in conjunction with ground mapping was applied in order to assess the architecture of a Plagioclase Ultraphyric Basalt (PUB) group in eastern Iceland, namely the Grænavatn group. The ~10 Myr old group is exposed in steep glacially carved fjords and can be traced over 60 km along strike. Two feeder dikes have been found and show that the group erupted along the trend of the dike swarm associated with the Breiddalur central volcano. The group has 9--14 flows where thickest, and thins to about 3--4 flows up-dip to the east within the distance of 15-20 km from the source. We have estimated the volume of the group to exceed 40 km3. The flows have mixed architecture of simple and compound morphology. The flow lobes have thicknesses from 1--24 m and many reach lengths over 1000 m. The surface morphology varies from rubbly to scoriaceous, but is dominantly of pahoehoe style. The internal structure of the lava flows is well preserved and the flows display abundant vesicle cylinders. The modal percentage of An-rich plagioclase macrocrysts varies from 25--50 % and they are in the range of 5--30 mm. The aspect ratio of the group and the nature of the flows indicate fissure-fed eruptions. A thick flow found at the base of the group in various locations seems to record the largest eruption episode in the formation of the group. This phase is also the most abundant in macrocryst. An asymmetric buildup is seen in one location and may have characterized the general buildup of the group. The general morphology of the lava flows suggests low viscous behavior, at odds with the high crystal content. Petrographic observations and mineral chemistry shows that the plagioclase macrocrysts are very calcic (An80-85) and in disequilibrium with the groundmass and plagioclases therein (An50-70). Thus the apparent lava rheology and emplacement of the PUBs was likely achieved due to fast ascent of the magma through the crust and transfer of heat from the primitive macrocrysts

  17. Bacterial diversity and successional patterns during biofilm formation on freshly exposed basalt surfaces at diffuse-flow deep-sea vents. (United States)

    Gulmann, Lara K; Beaulieu, Stace E; Shank, Timothy M; Ding, Kang; Seyfried, William E; Sievert, Stefan M


    Many deep-sea hydrothermal vent systems are regularly impacted by volcanic eruptions, leaving fresh basalt where abundant animal and microbial communities once thrived. After an eruption, microbial biofilms are often the first visible evidence of biotic re-colonization. The present study is the first to investigate microbial colonization of newly exposed basalt surfaces in the context of vent fluid chemistry over an extended period of time (4-293 days) by deploying basalt blocks within an established diffuse-flow vent at the 9°50' N vent field on the East Pacific Rise. Additionally, samples obtained after a recent eruption at the same vent field allowed for comparison between experimental results and those from natural microbial re-colonization. Over 9 months, the community changed from being composed almost exclusively of Epsilonproteobacteria to a more diverse assemblage, corresponding with a potential expansion of metabolic capabilities. The process of biofilm formation appears to generate similar surface-associated communities within and across sites by selecting for a subset of fluid-associated microbes, via species sorting. Furthermore, the high incidence of shared operational taxonomic units over time and across different vent sites suggests that the microbial communities colonizing new surfaces at diffuse-flow vent sites might follow a predictable successional pattern.

  18. First Recovery of Submarine Basalts from the Chukchi Borderland and Alpha / Mendeleev Ridge, Arctic Ocean (United States)

    Andronikov, A.; Mukasa, S.; Mayer, L. A.; Brumley, K.


    , suggesting fairly thin lava flows). These samples have a strongly altered glassy matrix with abundant plagioclase phenocrysts (up to 3 mm in length). Thin chilled basaltic crust on the lava surfaces displays pahoehoe structures, suggesting subaerial eruptions. Presence of subaerial basalts in this area supports the notion that the Chukchi Borderland has a continental origin. It is possible that further mapping using multibeam bathymetric methods and geochemical studies will show the high Arctic to possess a large igneous province built on both continental and oceanic crust.

  19. Holocene Flows of the Cima Volcanic Field, Mojave Desert, Part 2: Flow Rheology from Laboratory Measurements (United States)

    Robertson, T.; Whittington, A. G.; Soldati, A.; Sehlke, A.; Beem, J. R.; Gomez, F. G.


    Lava flow morphology is often utilized as an indicator of rheological behavior during flow emplacement. Rheological behavior can be characterized by the viscosity and yield strength of lava, which in turn are dependent on physical and chemical properties including crystallinity, vesicularity, and bulk composition. We are studying the rheology of a basaltic lava flow from a monogenetic Holocene cinder cone in the Cima lava field (Mojave Desert, California). The flow is roughly 2.5 km long and up to 700m wide, with a well-developed central channel along much of its length. Samples were collected along seven different traverses across the flow, along with real-time kinematic (RTK) GPS profiles to allow levee heights and slopes to be measured. Surface textures change from pahoehoe ropes near the vent to predominantly jagged `a`a blocks over the majority of the flow, including all levees and the toe. Chemically the lava shows little variation, plotting on the trachybasalt-basanite boundary on the total alkali-silica diagram. Mineralogically the lava is dominated by plagioclase, clinopyroxene and olivine phenocrysts, with abundant flow-aligned plagioclase microcrystals. The total crystal fraction is ~50% near the vent, with higher percentages in the distal portion of the flow. Vesicularity varies between ~10 and more than ~60%. Levees are ~10-15m high with slopes typically ~25-35˚, suggesting a yield strength at final emplacement of ~150,000 Pa. The effective emplacement temperature and yield strength of lava samples will be determined using the parallel-plate technique. We will test the hypothesis that these physical and rheological properties of the lava during final emplacement correlate with spatial patterns in flow morphology, such as average slope and levee width, which have been determined using remote sensing observations (Beem et al. 2014).

  20. Photogrammetric and Global Positioning System Measurements of Active Pahoehoe Lava Lobe Emplacement on Kilauea, Hawaii (United States)

    Hamilton, Christopher W.; Glaze, Lori S.; James, Mike R.; Baloga, Stephen M.; Fagents, Sarah A.


    Basalt is the most common rock type on the surface of terrestrial bodies throughout the solar system and -- by total volume and areal coverage -- pahoehoe flows are the most abundant form of basaltic lava in subaerial and submarine environments on Earth. A detailed understanding of pahoehoe emplacement processes is necessary for developing accurate models of flow field development, assessing hazards associated with active lava flows, and interpreting the significance of lava flow morphology on Earth and other planetary bodies. Here, we examine the active emplacement of pahoehoe lobes along the margins of the Hook Flow from Pu'u 'O'o on Kilauea, Hawaii. Topographic data were acquired between 21 and 23 February 2006 using stereo-imaging and differential global positing system (DGPS) measurements. During this time, the average discharge rate for the Hook Flow was 0.01-0.05 cubic m/s. Using stereogrammetric point clouds and interpolated digital terrain models (DTMs), active flow fronts were digitized at 1 minute intervals. These areal spreading maps show that the lava lobe grew by a series of breakouts tha t broadly fit into two categories: narrow (0.2-0.6 m-wide) toes that grew preferentially down-slope, and broad (1.4-3.5 m-wide) breakouts that formed along the sides of the lobe, nearly perpendicular to the down-flow axis. These lobes inflated to half of their final thickness within approx 5 minutes, with a rate of inflation that generally deceased with time. Through a combination of down-slope and cross-slope breakouts, lobes developed a parabolic cross-sectional shape within tens of minutes. We also observed that while the average local discharge rate for the lobe was generally constant at 0.0064 +/- 0.0019 cubic m/s, there was a 2 to 6 fold increase in the areal coverage rate every 4.1 +/- 0.6 minutes. We attribute this periodicity to the time required for the dynamic pressurization of the liquid core of the lava lobe to exceed the cooling-induced strength of the

  1. Eruptive behavior of the Marum/Mbwelesu lava lake, Vanuatu and comparisons with lava lakes on Earth and Io (United States)

    Radebaugh, Jani; Lopes, Rosaly M.; Howell, Robert R.; Lorenz, Ralph D.; Turtle, Elizabeth P.


    Observations from field remote sensing of the morphology, kinematics and temperature of the Marum/Mbwelesu lava lake in the Vanuatu archipelago in 2014 reveal a highly active, vigorously erupting lava lake. Active degassing and fountaining observed at the 50 m lava lake led to large areas of fully exposed lavas and rapid ( 5 m/s) movement of lava from the centers of upwelling outwards to the lake margins. These rapid lava speeds precluded the formation of thick crust; there was never more than 30% non-translucent crust. The lava lake was observed with several portable, handheld, low-cost, near-infrared imagers, all of which measured temperatures near 1000 °C and one as high as 1022 °C, consistent with basaltic temperatures. Fine-scale structure in the lava fountains and cooled crust was visible in the near infrared at 5 cm/pixel from 300 m above the lake surface. The temperature distribution across the lake surface is much broader than at more quiescent lava lakes, peaking 850 °C, and is attributed to the highly exposed nature of the rapidly circulating lake. This lava lake has many characteristics in common with other active lava lakes, such as Erta Ale in Ethiopia, being confined, persistent and high-temperature; however it was much more active than is typical for Erta Ale, which often has > 90% crust. Furthermore, it is a good analogue for the persistent, high-temperature lava lakes contained within volcanic depressions on Jupiter's moon Io, such as Pele, also believed from spacecraft and ground-based observations to exhibit similar behavior of gas emission, rapid overturn and fountaining.

  2. Effect of melt composition and crystal content on flow morphology along the Alarcón Rise, Mexico (United States)

    Martin, J. F.; Lieberg-Clark, P.; Clague, D. A.; Caress, D. W.; Portner, R. A.; Paduan, J. B.; Dreyer, B. M.


    Differences in submarine lava flow morphology have been related to differences in eruption rate; low eruption rates form pillow-flow morphologies whereas high eruption rates form sheet-flow morphologies. Eruption rate is likely controlled by dike intrusion width, exsolved bubble content of the magma, viscosity of the magma, or some combination these three properties. Samples and observations from a 2012 expedition to the Alarcón Rise, Mexico, are used to evaluate the potential control of viscosity due to melt composition and crystal content on observed flow morphologies and associated eruption rates. A 1-m resolution multibeam survey, covering the entire 50 km length of the neovolcanic zone, was completed using the MBARI Mapping AUV. Based on the high-resolution bathymetry, two basic flow morphologies could be distinguished: pillow flows, comprising ~ 40 % of the rise, and sheet flows, comprising the remaining ~ 60 %. A series of dives using the ROVs Doc Ricketts in 2012 and Tiburon in 2003 visually confirmed pillow flows, lobate flows, sheet flows, and jumbled sheet flows at the sampled sites. Over 150 lava samples collected during the dives, spanning the entire length of the rise were analyzed for major-element chemistry, crystal content, and corresponding flow morphology. Lavas selected for this analysis ranged from basalt to basaltic-andesite (100 pa s, only pillow lavas are generated. The majority (> 80 %) of sampled pillow lavas are plagioclase-phyric to ultraphyric whereas the majority of lobate and sheet flow lavas are aphyric. Crystal fractions in the pillow lavas are as high as 30-40%, resulting in magma viscosities ~ 5-15 times the melt viscosities. The majority of pillow lavas (~77%) have magma viscosities > 100 pa s. Only ~ 25 % of lobate and sheet flow lavas have magma viscosities > 100 pa s. Many of the phyric lobate and sheet flow samples show evidence of strong flow segregation of crystals to the outer surface of the flow, resulting in samples

  3. Scientific results from the deepened Lopra-1 borehole, Faroe Islands: Mineralogical and thermodynamic constraints on Palaeogene palaeotemperature conditions during low-grade metamorphism of basaltic lavas recovered from the Lopra-1/1A deep hole, Faroe Islands

    Directory of Open Access Journals (Sweden)

    Glassley, William E.


    Full Text Available The sequene of secondary minerals that are reported for the Lopra-1/1A well records progressive zeolite facies to prehnite–pumpellyite-facies mineral progressions consistent with those of other wellstudied hydrothermally altered rock sequences. Detailed comparison of the calc–silicate (zeolites and prehnite mineral distributions of the Lopra-1/1A sequence with those from other regions indicates that this sequence exhibits consistently longer down-hole intervals for secondary mineral species than reported elsewhere. When compared to measured down-hole temperatures reported in other hydrothermally altered regions, the results suggest that the Lopra-1/1A mineral progression formed under conditions typical of low temperature hydrothermal systems that form shortly after eruption of thick basaltic piles. Maximum temperatures achieved at the 3500 m level of the well were at or below 200°C. The implied geothermal gradient was less than 50°C/km. An analysis of prehnite – fluid composition relationships was also conducted in order to determine if results compatible with the paragenetic sequence study could be obtained from thermodynamic constraints. In this case, thelimiting temperature for prehnite formation in equilibrium with albite–quartz–calcite–laumontite (the mineral assemblage at the bottom of the hole was determined for a range of fluid compositions.The resulting calculations suggest temperatures of formation of prehnite in the range of 140°C to 205°C, a conclusion which is broadly consistent with those reached from study of the parageneticrelationships. Comparison of these results with other studies of palaeogeothermal gradients of the North Atlantic margins suggests a consistent pattern in which relatively low geothermal gradientspersisted in the Palaeogene rift basin.

  4. Eruptive and tectonic history of the Endeavour Segment, Juan de Fuca Ridge, based on AUV mapping data and lava flow ages (United States)

    Clague, David A.; Dreyer, Brian M; Paduan, Jennifer B; Martin, Julie F; Caress, David W; Gillespie, James B.; Kelley, Deborah S; Thomas, Hans; Portner, Ryan A; Delaney, John R; Guilderson, Thomas P.; McGann, Mary L.


    High-resolution bathymetric surveys from autonomous underwater vehicles ABE and D. Allan B. were merged to create a coregistered map of 71.7 km2 of the Endeavour Segment of the Juan de Fuca Ridge. Radiocarbon dating of foraminifera in cores from three dives of remotely operated vehicle Doc Ricketts provide minimum eruption ages for 40 lava flows that are combined with the bathymetric data to outline the eruptive and tectonic history. The ages range from Modern to 10,700 marine-calibrated years before present (yr BP). During a robust magmatic phase from >10,700 yr BP to ~4300 yr BP, flows erupted from an axial high and many flowed >5 km down the flanks; some partly buried adjacent valleys. Axial magma chambers (AMCs) may have been wider than today to supply dike intrusions over a 2 km wide axial zone. Summit Seamount formed by ~4770 yr BP and was subsequently dismembered during a period of extension with little volcanism starting ~4300 yr BP. This tectonic phase with only rare volcanic eruptions lasted until ~2300 yr BP and may have resulted in near-solidification of the AMCs. The axial graben formed by crustal extension during this period of low magmatic activity. Infrequent eruptions occurred on the flanks between 2620–1760 yr BP and within the axial graben since ~1750 yr BP. This most recent phase of limited volcanic and intense hydrothermal activity that began ~2300 yr BP defines a hydrothermal phase of ridge development that coincides with the present-day 1 km wide AMCs and overlying hydrothermal vent fields.

  5. Eruptive and tectonic history of the Endeavour Segment, Juan de Fuca Ridge, based on AUV mapping data and lava flow ages (United States)

    Clague, David. A.; Dreyer, Brian M.; Paduan, Jennifer B.; Martin, Julie F.; Caress, David W.; Gill, James B.; Kelley, Deborah S.; Thomas, Hans; Portner, Ryan A.; Delaney, John R.; Guilderson, Thomas P.; McGann, Mary L.


    bathymetric surveys from autonomous underwater vehicles ABE and D. Allan B. were merged to create a coregistered map of 71.7 km2 of the Endeavour Segment of the Juan de Fuca Ridge. Radiocarbon dating of foraminifera in cores from three dives of remotely operated vehicle Doc Ricketts provide minimum eruption ages for 40 lava flows that are combined with the bathymetric data to outline the eruptive and tectonic history. The ages range from Modern to 10,700 marine-calibrated years before present (yr BP). During a robust magmatic phase from >10,700 yr BP to ˜4300 yr BP, flows erupted from an axial high and many flowed >5 km down the flanks; some partly buried adjacent valleys. Axial magma chambers (AMCs) may have been wider than today to supply dike intrusions over a 2 km wide axial zone. Summit Seamount formed by ˜4770 yr BP and was subsequently dismembered during a period of extension with little volcanism starting ˜4300 yr BP. This tectonic phase with only rare volcanic eruptions lasted until ˜2300 yr BP and may have resulted in near-solidification of the AMCs. The axial graben formed by crustal extension during this period of low magmatic activity. Infrequent eruptions occurred on the flanks between 2620-1760 yr BP and within the axial graben since ˜1750 yr BP. This most recent phase of limited volcanic and intense hydrothermal activity that began ˜2300 yr BP defines a hydrothermal phase of ridge development that coincides with the present-day 1 km wide AMCs and overlying hydrothermal vent fields.

  6. Nornahraun lava morphology and mode of emplacement (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


    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

  7. Mapping Planetary Volcanic Deposits: Identifying Vents and Distingushing between Effects of Eruption Conditions and Local Lava Storage and Release on Flow Field Morphology (United States)

    Bleacher, J. E.; Eppler, D. B.; Skinner, J. A.; Evans, C. A.; Feng, W.; Gruener, J. E.; Hurwitz, D. M.; Whitson, P.; Janoiko, B.


    Terrestrial geologic mapping techniques are regularly used for "photogeologic" mapping of other planets, but these approaches are complicated by the diverse type, areal coverage, and spatial resolution of available data sets. When available, spatially-limited in-situ human and/or robotic surface observations can sometimes introduce a level of detail that is difficult to integrate with regional or global interpretations. To assess best practices for utilizing observations acquired from orbit and on the surface, our team conducted a comparative study of geologic mapping and interpretation techniques. We compared maps generated for the same area in the San Francisco Volcanic Field (SFVF) in northern Arizona using 1) data collected for reconnaissance before and during the 2010 Desert Research And Technology Studies campaign, and 2) during a traditional, terrestrial field geology study. The operations, related results, and direct mapping comparisons are discussed in companion LPSC abstracts [1-3]. Here we present new geologic interpretations for a volcanic cone and related lava flows as derived from all approaches involved in this study. Mapping results indicate a need for caution when interpreting past eruption conditions on other planetary surfaces from orbital data alone.

  8. Role of mechanical erosion in controlling the effusion rate of basaltic eruptions (United States)

    Piombo, Antonello; Tallarico, Andrea; Dragoni, Michele


    In many basaltic eruptions, observations show that the effusion rate of magma has a typical dependence on time: the effusion rate curves show first a period of increasing and later a decreasing phase by a maximum value. We present a model to explain this behavior by the emptying of a magma reservoir through a vertical cylindrical conduit with elliptical cross section, coupled with the its widening due to mechanical erosion, produced by the magma flow. The model can reproduce the observed dependence on time of effusion rate in basaltic eruptions. Eruption duration and the maximum value of effusion rate depend on the size of magma chamber, on lava viscosity and strongly on erosion rate per unit traction.

  9. Chemical mobility during low-grade metamorphism of a Jurassic lava flow: Río Grande Formation, Peru (United States)

    Aguirre, L.

    Chemical and mineralogical changes produced by very low-grade metamorphism in a 40 meter thick, K-rich, calc-alkaline andesite flow of the marine Jurassic Río Grande Formation of southern coastal Peru are discussed. This metamorphism (=spilitization) was non-deformational and generated spilitic domains at (and near) both vesicular margins of the flow, whereas the massive central zone remained relatively unaltered. The metadomains are characterized by mineral associations of the zeolite facies. Primary minerals are Ca-plagioclase, augitic pyroxene, iron-titanium oxides, and (pseudomorphs after) olivine. Metamorphic minerals are: albite (three generations), K-feldspar, pumpellyite, chlorite, interlayered chlorite-celadonite, celadonite, various mixed-layer Si- and Fe-rich phyllosilicates, "iddingsite," calcite, analcime, titanite, and white mica. The effect of the metamorphism on the rock chemistry is reflected in changes especially observed at the marginal zones of the flow which affect major, trace, and RE elements: 1) strong increase of the iron oxidation ratio (Fe 2O 3/FeO); 2) enrichment in Na 2O accompanied by a concomitant depletion of CaO in non-amygdaloidal domains; 3) depletion of SiO 2; 4) strong enrichment in H 2O and CO 2; 5) marked depletion of Sr and Rb; 6) enrichment in Cl and S; and 7) slight depletion in RE elements, notably in the top zone of the flow. Conversely, elements such as Ti, P, Nb, and Y were fairly immobile, whereas Zr and K were only slightly mobilized. The effect of the metamorphism on the mineral chemistry is expressed by the predominance of metastable equilibrium evidenced by the existence of wide compositional ranges in the phyllosilicates, the incomplete albitization of the Ca-plagioclase, and the Al-rich character of the pumpellyites. The metamorphism is considered to be of hydrothermal-burial type, which takes place at low temperature and pressure — probably about 125-230°C and less than 3 kb, and is produced mainly through

  10. Volcanic succession and feeder systems of acidic lava-domes of Serra Geral Formation in São Marcos-Antônio Prado region, South Brazil

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    Evandro Fernandes de Lima


    Full Text Available In the São Marcos (RS and Antonio Prado (RS, the Serra Geral Formation exposes at the base basalts of pahoehoe type, coveredby basalts of the ´a´ā type. The first succession was generated by a low rate of eruption in a closed flow system allowed the flow toreach distances > 100 km of the source.T he ´a´ā lava flow types were generated by higher rates of eruption andt ransported in openchannels where rapid cooling prevented long distances from the source to be reached. The two types of basalts are low-TiO2 tholeiiticand the morphology of flows is not related to variations in SiO2 and MgO contents. Above these rock types outcrop acidic volcanicrocks geochemically of Caxias Group (Palmas Subgroup. Dimension stones extraction exposed the inner portions of the acidicfeeder dikes with vertical magmatic foliations. The lava domes have exogenous characteristics and horizontal foliations. We proposea model for the generation of domes involving the diapirically rise of acids magmas that become vesicular and more viscous, thatstop near the surface. New magmatic pulses extracted “pieces” of the vesicular fraction generating autobreccias in the conduit andvertical structures that extend laterally toward the surface organizing the lava domes with vitrophyres in the base and in the top, witha thin massive phaneritic core. Magmatic textures of the domes are typical of effusive units and the identification of the feeder dykesin the area allows the understanding of the emplacement process of acidic flows in the Serra Geral Formation.

  11. Making rhyolite in a basalt crucible (United States)

    Eichelberger, John


    Iceland has long attracted the attention of those concerned with the origin of rhyolitic magmas and indeed of granitic continental crust, because it presents no alternative for such magmas other than deriving them from a basaltic source. Hydrothermally altered basalt has been identified as the progenitor. The fact that rhyolite erupts as pure liquid requires a process of melt-crustal separation that is highly efficient despite the high viscosity of rhyolite melt. Volcanoes in Iceland are foci of basaltic magma injection along the divergent plate boundary. Repeated injection produces remelting, digestion, and sometimes expulsion or lateral withdrawal of material resulting in a caldera, a "crucible" holding down-dropped and interlayered lava flows, tephras, and injected sills. Once melting of this charge begins, a great deal of heat is absorbed in the phase change. Just 1% change in crystallinity per degree gives a melt-present body an effective heat capacity >5 times the subsolidus case. Temperature is thus buffered at the solidus and melt composition at rhyolite. Basalt inputs are episodic ("fires") so likely the resulting generation of rhyolite by melting is too. If frequent enough to offset cooling between events, rhyolite melt extractions will accumulate as a rhyolite magma reservoir rather than as discrete crystallized sills. Evidently, such magma bodies can survive multiple firings without themselves erupting, as the 1875 eruption of Askja Caldera of 0.3 km3 of rhyolite equilibrated at 2-km depth without previous leakage over a ten-millennium period and the surprise discovery of rhyolite magma at 2-km depth in Krafla suggest. Water is required for melting; otherwise melting cannot begin at a temperature lower than that of the heat source. Because the solubility of water in melt is pressure-dependent and almost zero at surface pressure, there must be a minimum depth at which basalt-induced melting can occur and a rhyolite reservoir sustained. In practice, the

  12. Analysing diagenetic effects of flood basalts on sedimentary basins during Gondwanan break-up: case studies from NW Namibia. (United States)

    Thompson, G. A.; Jerram, D. A.; Harris, C.; Pearson, D. G.


    ABSTRACT The eruption of large volumes of lava associated with the break-up and dispersal of the Gondwana Supercontinent is a phenomenon that has been well documented in literature. The Etendeka Flood Basalt Province of NW Namibia is correlated with the Paraná Flood Basalt Province of South America and was extruded between 139Ma for the earliest flows and 130Ma for the most recent. The passive, inflated pahoehoe lava flows have preserved bedforms within sand dunes found in the Huab Basin without significant deformation. This allows the internal structures of the palaeo-dunes to be analysed with great accuracy; a phenomenon rarely seen within the geological record. The sediments directly beneath, and interbedded with, the Etendeka Flood Basalt are lithostratigraphically similar to those in the Kudu Gas Province, offshore Namibia, where gas-bearing aeolian sands are interspersed with lava flows. Research by the authors is focussed on the diagenetic effects, both direct and indirect, of the emplacement of the lava, and the associated sills and dykes, on the aeolian sands. Specific interests include: the compartmentalisation of the basin by sills/dykes/lava: how does this affect fluid flow paths? Diagenesis along hot contacts: is the dramatic reduction in porosity/permeability along such contacts the result of the igneous bodies alone or do they need ground water present? Can large igneous events trigger the movement of hot fluids through the basin and to what extent does this cause alteration to sediments? To address these issues we have identified a number of outcrop case studies within the Huab Basin in NW Namibia. Here, excellent 3 dimensional outcrop coupled with almost 100 percent exposure allows detailed sampling strategies to be employed on locations of interest. In some cases igneous dykes have acted as flow barriers to pore fluids and have therefore altered the type and degree of cementation either side of the dyke. Geochemical analysis of the cement can

  13. 31+/-17 ka 40Ar/39Ar Plateau Age on the Very Low-Potassium Hat Creek Basalt Fits Stratigraphic and Geochronologic Constraints of Contiguous Units (United States)

    Clynne, M. A.; Turrin, B. D.; Champion, D. E.; Muffler, L. P.


    The Hat Creek Basalt is a late Pleistocene low-K olivine tholeiite that floors much of the Hat Creek Valley, north of the Lassen volcanic highland in NE California. The flow erupted from a fissure trending N 10° W located 0.5 to 4.0 km SSE of Old Station and flowed north nearly 30 km, mainly through lava tubes. Paleomagnetic data indicate that the Hat Creek Basalt is a single eruptive unit with an inclination of 64.3° and a declination of 1.0° . The Hat Creek Basalt is overlain by gravel related to the last major glaciation, which ended about 15 to 17 ky ago. The Hat Creek Basalt overlies numerous andesite and basaltic andesite lava flows that are closely related geographically, stratigraphically, petrographically and geochemically and probably represent the same eruptive episode (although not necessarily the same year or century). Three of these flows have been dated by the 40Ar/39Ar method and yield concordant plateau, integrated (total fusion), and isochron ages: Little Potato Butte (1.42% K2O; 67+/-4 ka), Sugarloaf (1.85% K2O; 55+/-7 ka), and Big Potato Butte (1.62% K2O; 73+/-14 ka). The Hat Creek Basalt also overlies the basaltic andesite of Cinder Butte (1.65% K2O) with a 40Ar/39Ar plateau age of 38+/-7 ka. Given that the age of the Hat Creek Basalt is thus firmly bracketed between ˜15 ka and 38+/-7 ka, we attempted to date this low-potassium tholeiitic basalt directly. One sample produced 40Ar/39Ar data that cannot be interpreted, but a second sample (0.17% K2O) yielded concordant plateau, integrated (total fusion), and isochron ages of 31+/-17 ka, 30+/-20 ka, and 24+/-6 ka; within the time bracket determined by stratigraphic relations. These data indicate that samples of latest Pleistocene tholeiitic basalt with very low K2O can give useful 40Ar/39Ar ages. As with all isotopically determined ages, the confidence of the results are significantly enhanced when additional constraints imposed by other isotopic ages within a stratigraphic context are taken

  14. Geochemistry of quaternary shoshonitic lavas related to the Calama-Olacapato-El Toro Lineament, NW Argentina (United States)

    Schreiber, U.; Schwab, K.

    Along the NW/SE-trending Calama-Olacapato-El Toro Lineament, Cenozoic volcanics occur far to the east of the main volcanic chain of the Central Andes. The petrochemical data of Quaternary shoshonitic lava flows of Cerro San Gerónimo and Cerro Negro de Chorrillos, situated on this lineament, are discussed in comparison with the data of presumably late Tertiary lavas and pyroclastics of the same area. The presence of foids and high temperature quartz crystals rimmed by pyroxene in the study samples indicates magma mixing. The REE patterns of the shoshonites are steep, with LREE enrichment up to 200 times that of chondritic values. This points to garnet as a constituent mineral in the residual phase during magma generation. The influence of fractionation of plagioclase can be ignored. The petrochemical data point to a basanitic alkali basaltic primordial magma. It is suggested that this magma could pass the very thick crust (>60km) along the deep-reaching Calama-Olacapato-El Toro Lineament. On the way up the magma was contaminated by mixing of up to 25% with a silicic magma to produce the shoshonitic lavas.

  15. Age of the youngest Palaeogene flood basalts in East Greenland

    DEFF Research Database (Denmark)

    Heilmann-Clausen, C.; Piasecki, Stefan; Abrahamsen, Niels;


    Intra-basaltic sediments 50 m below the top of the Paleogene lava succession at Kap Dalton, East Greenland, contain dinoflagellate cysts of late Ypresian-earliest Lutetian age, while sediments immediately above the lavas contain an assemblage of early Lutetian age. Combined with paleomagnetic...... results, this constrains the termination of the East Greenland Paleogene Igneous Province to the Early-Middle Eocene transition (nannoplankton chronozones NP13-NP14/earliest NP15). This is 6-8 Ma younger than according to previous biostratigraphic age assignments. The new data show that flood basalt...

  16. Paleomagnetism and dating of a thick lava pile in the Permian Bakaly formation of eastern Kazakhstan: Regularities and singularities of the paleomagnetic record in thick lava series (United States)

    Bazhenov, Mikhail L.; Van der Voo, Rob; Menzo, Zachary; Dominguez, Ada R.; Meert, Joseph G.; Levashova, Natalia M.


    Paleomagnetic results on thick lava series are among the most important sources of information on the characteristics of ancient geomagnetic fields. Most paleo-secular variation data from lavas (PSVL) are of late Cenozoic age. There are far fewer results from lavas older than 5 Ma. The Central Asia Orogenic Belt that occupies several million square kilometers in Asia is probably the world's largest area of Paleozoic volcanism and is thus an attractive target for PSVL studies. We studied a ca. 1700 m thick lava pile in eastern Kazakhstan of Early Permian age. Magmatic zircons, successfully separated from an acid flow in this predominantly basaltic sequence, yielded an Early Permian age of 286.3 ± 3.5 Ma. Oriented samples were collected from 125 flows, resulting in 88 acceptable quality flow-means (n ⩾ 4 samples, radius of confidence circle α95 ⩽ 15°) of the high-temperature magnetization component. The uniformly reversed component is pre-tilting and arguably of a primary origin. The overall mean direction has a declination = 242.0° and an inclination = -56.2° (k = 71.5, α95 = 1.8°; N = 88 sites; pole at 44.1°N, 160.6°E, A95 = 2.2°). Our pole agrees well with the Early Permian reference data for Baltica, in accord with the radiometric age of the lava pile and geological views on evolution of the western part of the Central Asia Orogenic Belt. The new Early Permian result indicates a comparatively low level of secular variation especially when compared to PSVL data from intervals with frequent reversals. Still, the overall scatter of dispersion estimates that are used as proxies for SV magnitudes, elongation values and elongation orientations for PSVL data is high and cannot be fitted into any particular field model with fixed parameters. Both observed values and numerical simulations indicate that the main cause for the scatter of form parameters (elongation values and elongation orientations) is the too small size of collections. Dispersion estimates


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    G.A. Valentine; F.V. Perry; D. Krier; G.N. Keating; R.E. Kelley; A.H. Cogbill


    Five Pleistocene basaltic volcanoes in Crater Flat (southern Nevada) demonstrate the complexity of eruption processes associated with small-volume basalts and the effects of initial emplacement characteristics on post-eruptive geomorphic evolution of the volcanic surfaces. The volcanoes record eruptive processes in their pyroclastic facies ranging from ''classical'' Strombolian mechanisms to, potentially, violent Strombolian mechanisms. Cone growth was accompanied, and sometimes disrupted, by effusion of lavas from the bases of cones. Pyroclastic cones were built upon a gently southward-sloping surface and were prone to failure of their down-slope (southern) flanks. Early lavas flowed primarily southward and, at Red and Black Cone volcanoes, carried abundant rafts of cone material on the tops of the flows. These resulting early lava fields eventually built platforms such that later flows erupted from the eastern (at Red Cone) and northern (at Black Cone) bases of the cones. Three major surface features--scoria cones, lava fields with abundant rafts of pyroclastic material, and lava fields with little or no pyroclastic material--experienced different post-eruptive surficial processes. Contrary to previous interpretations, we argue that the Pleistocene Crater Flat volcanoes are monogenetic, each having formed in a single eruptive episode lasting months to a few years, and with all eruptive products having emanated from the area of the volcanoes main cones rather than from scattered vents. Geochemical variations within the volcanoes must be interpreted within a monogenetic framework, which implies preservation of magma source heterogeneities through ascent and eruption of the magmas.

  18. Paleomagnetic correlation of basalt flows in selected coreholes near the Advanced Test Reactor Complex, the Idaho Nuclear Technology and Engineering Center, and along the southern boundary, Idaho National Laboratory, Idaho (United States)

    Hodges, Mary K.V.; Champion, Duane E.


    The U.S. Geological Survey, in cooperation with the U.S. Department of Energy, used paleomagnetic data from 18 coreholes to construct three cross sections of subsurface basalt flows in the southern part of the Idaho National Laboratory (INL). These cross sections, containing descriptions of the subsurface horizontal and vertical distribution of basalt flows and sediment layers, will be used in geological studies, and to construct numerical models of groundwater flow and contaminant transport.Subsurface cross sections were used to correlate surface vents to their subsurface flows intersected by coreholes, to correlate subsurface flows between coreholes, and to identify possible subsurface vent locations of subsurface flows. Correlations were identified by average paleomagnetic inclinations of flows, and depth from land surface in coreholes, normalized to the North American Datum of 1927. Paleomagnetic data were combined, in some cases, with other data, such as radiometric ages of flows. Possible vent locations of buried basalt flows were identified by determining the location of the maximum thickness of flows penetrated by more than one corehole.Flows from the surface volcanic vents Quaking Aspen Butte, Vent 5206, Mid Butte, Lavatoo Butte, Crater Butte, Pond Butte, Vent 5350, Vent 5252, Tin Cup Butte, Vent 4959, Vent 5119, and AEC Butte are found in coreholes, and were correlated to the surface vents by matching their paleomagnetic inclinations, and in some cases, their stratigraphic positions.Some subsurface basalt flows that do not correlate to surface vents, do correlate over several coreholes, and may correlate to buried vents. Subsurface flows which correlate across several coreholes, but not to a surface vent include the D3 flow, the Big Lost flow, the CFA buried vent flow, the Early, Middle, and Late Basal Brunhes flows, the South Late Matuyama flow, the Matuyama flow, and the Jaramillo flow. The location of vents buried in the subsurface by younger basalt

  19. Using 40Ar/39Ar ages of intercalated silicic tuffs to date flood basalts: Precise ages for Steens Basalt Member of the Columbia River Basalt Group (United States)

    Mahood, Gail A.; Benson, Thomas R.


    To establish causality between flood basalt eruptions and extinction events and global environmental effects recorded by isotopic excursions in marine sediments, highly accurate and precise ages for the flood basalts are required. But flood basalts are intrinsically difficult to date. We illustrate how 40Ar/39Ar feldspar ages for silicic tuffs intercalated with and overlying sections of Steens Basalt, the earliest lavas of the Middle Miocene Columbia River Basalt Group in the northwestern United States, provide high-precision ages that, for the first time, make it possible to resolve age differences with stratigraphic position within a section of these flood lavas. The stratigraphically lowest rhyolitic tuff, a fall deposit, yielded an age of 16.592 ± ± 0.028 Ma (FCs = 28.02 Ma), and the uppermost, the alkali rhyolite ignimbrite Tuff of Oregon Canyon, is 16.468 ± ± 0.014 Ma. The argon and stratigraphic data indicate that Steens Basalt eruptions occurred from ∼16.64 to 16.43 Ma in the southern end of its distribution. We estimate that the Steens Mountain geomagnetic reversal occurred at 16.496 ± ± 0.028 Ma (±0.18 Ma total error). Our estimates of the timing for initiation of volcanism and volumetric eruptive rates do not seem to support volcanic forcing by the initial stages of Columbia River Basalt Group eruptions as an explanation for the abrupt warming and carbonate dissolution at the beginning of the Miocene Climatic Optimum.

  20. Evaluation of Sulfur Flow Emplacement on Io from Galileo Data and Numerical Modeling (United States)

    Williams, David A.; Greeley, Ronald; Lopes, Rosaly M. C.; Davies, Ashley G.


    Galileo images of bright lava flows surrounding Emakong Patera have bee0 analyzed and numerical modeling has been performed to assess whether these flows could have resulted from the emplacement of sulfur lavas on Io. Images from the solid-state imaging (SSI) camera show that these bright, white to yellow Emakong flows are up to 370 km long and contain dark, sinuous features that are interpreted to be lava conduits, -300-500 m wide and >lo0 km lorig. Neiu-Infrared Mapping S estimate of 344 K f 60 G131'C) within the Bmakong caldera. We suggest that these bright flows likely resulted from either sulfur lavas or silicate lavas that have undergone extensive cooling, pyroclastic mantling, and/or alteration with bright sulfurous materials. The Emakoag bright flows have estimated volume of -250-350 km', similar to some of the smaller Columbia River Basalt flows, If the Emakong flows did result from effusive sulfur eruptions, then they are orders of magnitude reater in volume than any terrestrial sulfur flows. Our numerical modeling capable of traveling tens to hundreds of kilometers, consistent with the predictions of Sagan. Our modeled flow distances are also consistent with the measured lengths of the Emakong channels and bright flows.

  1. 3-D reconstructions of subsurface Pleistocene basalt flows from paleomagnetic inclination data and 40Ar/39Ar ages in the southern part of the Idaho National Laboratory (INL), Idaho (USA) (United States)

    Hodges, Mary K.; Champion, Duane E.; Turrin, B.D.; Swisher, C. C.


    The U. S. Geological Survey, in cooperation with the U.S. Department of Energy, is mapping the distribution of basalt flows and sedimentary interbeds at the Idaho National Laboratory in three dimensions to provide data for refining numerical models of groundwater flow and contaminant transport in the eastern Snake River Plain aquifer. Paleomagnetic inclination and polarity data from basalt samples from 47 coreholes are being used to create a three-dimensional (3-D) model of the subsurface of the southern part of the INL. Surface and sub-surface basalt flows can be identified in individual cores and traced in three dimensions on the surface and in the subsurface for distances of more than 20 km using a combination of paleomagnetic, stratigraphic, and 40Ar/39Ar data. Eastern Snake River Plain olivine tholeiite basalts have K2O contents of 0.2 to 1.0 weight per cent. In spite of the low-K content, high-precision 40Ar/39Ar ages were obtained by applying a protocol that employs short irradiation times (minimizing interferences from Ca derived 36Ar), frequent measurement of various size atmospheric Ar pipettes to monitor and correct for temporal variation, and signal size dependent nonlinearity in spectrometer mass bias, resulting in age dates with resolution generally between 2 to 10% of the age. 3-D models of subsurface basalt flows are being used to: (1) Estimate eruption volumes; (2) locate the approximate vent areas and extent of sub-surface flows; and (3) Help locate high and low transmissivity zones. Results indicate that large basalt eruptions (>3 km3) occurred at and near the Central Facilities Area between 637 ka and 360 ka; at and near the Radioactive Waste Management Complex before 540 ka; and north of the Naval Reactors Facility at about 580 ka. Since about 360 ka, large basalt flows have erupted along the Arco-Big Southern Butte Volcanic Rift Zone and the Axial Volcanic Zone, and flowed northerly towards the Central Facilities Area. Basalt eruptions shifted

  2. Visualization of space competition and plume formation with complex potentials for multiple source flows: Some examples and novel application to Chao lava flow (Chile)

    NARCIS (Netherlands)

    Weijermars, R.


    Fluid displacement in a continuum pressured by a variable constellation of source flows can be visualized as solutions of line integrals. The algorithms are based on complex potentials that provide exact solutions of the Navier-Stokes equation and allow users to specify both the location and flux st

  3. A comparative Study of Circulation Patterns at Active Lava Lakes (United States)

    Lev, Einat; Oppenheimer, Clive; Spampinato, Letizia; Hernandez, Pedro; Unglert, Kathi


    Lava lakes present a rare opportunity to study magma dynamics in a large scaled-up "crucible" and provide a unique natural laboratory to ground-truth dynamic models of magma circulation. The persistence of lava lakes allows for long-term observations of flow dynamics and of lava properties, especially compared to surface lava flows. There are currently five persistent lava lakes in the world: Halemaumau in Kilauea (Hawaii, USA), Erta Ale (Ethiopia), Nyiragongo (Congo), Erebus (Antarctica), and Villarica (Chile). Marum and Benbow craters of Ambrym volcano (Vanuatu) and Masaya (Nicaragua) have often hosted lava lakes as well. We use visible-light and thermal infrared time-lapse and video footage collected at all above lakes (except Villarica, where the lake is difficult to observe), and compare the circulation patterns recorded. We calculate lake surface motion from the footage using the optical flow method (Lev et al., 2012) to produce 2D velocity fields. We mined both the surface temperature field and the surface velocity field for patterns using machine learning techniques such as "self-organizing maps (SOMs)" and "principle component analysis (PCA)". We use automatic detection technique to study the configuration of crustal plates at the lakes' surface. We find striking differences among the lakes, in flow direction, flow speed, frequency of changes in flow direction and speed, location and consistency of upwelling and downwelling, and crustal plate configuration. We relate the differences to lake size, shallow conduit geometry, lava viscosity, crystal and gas content, and crust integrity.

  4. Rock magnetism and magnetic anisotropy in folded sills and basaltic flows: A case study of volcanics from the Taimyr Peninsula, Northern Russia

    Institute of Scientific and Technical Information of China (English)

    ZHANG ShuWei; J. Harald WALDERHAUG; YANG YueJun


    Magnetic measurements were performed on apparently deformed igneous rocks of 23 sites from the southeastern part of the Taimyr Peninsula. Rock magnetism and reflected light microscopy analyses reveal that fine-grained titanomagnetites up to pure magnetites mainly carry the majority of magnetic fabrics in the sills, and that the slightly coarser Ti-poor or-medium titanomagnetites carry most mag-netic fabrics in the basaltic flows. Magnetic anisotropies were determined by applying anisotropy of low-field magnetic susceptibility (AMS) on 180 unheated samples and 128 samples that had been pre-viously heated to 600℃ during a paleomagnetic study to detect heating effects on the anisotropy of magnetic susceptibility (AMS) properties of volcanic rocks. Laboratory heating significantly affects anisotropy variations of these igneous rocks corresponding to the mineralogical changes during the heat treatment.

  5. The foaming of lavas (United States)

    Okeefe, J. A.; Walton, W.


    Foaming is of great practical and theoretical significance for volcanic processes on the earth, the moon, and perhaps the meteorite parent bodies. The theory of foams agrees with steelmaking experience to indicate that their presence depends on the existence of solutes in the lavas which reduce the surface tension, and are not saturated. These solutes concentrate at the surface, and are called surfactants. The surfactant responsible for the formation of volcanic ash was not identified; it appears to be related to the oxygen partial pressure above the lava. This fact may explain why lunar and meteoritic melts are not observed to foam. Experimental studies are needed to clarify the process.

  6. Volcanism on Mercury (dikes, lava flows, pyroclastics): Crust/mantle density contrasts, the evolution of compressive stress and the presence of mantle volatiles (United States)

    Wilson, L.; Head, J. W., III


    Background. There is great uncertainty about the internal structure of Mercury and the composition of the mantle [e.g., 1, 2]. The high mean density of the body suggests that it may have lost parts of its crust and mantle in a giant impact at some stage after most of its initial accretion was sufficiently complete that at least partial separation of a core had occurred. It is the uncertainty about the timing of the giant impact, and hence the physico-chemical state of proto-Mercury at the time that it occurred, that leads to difficulties in predicting the interior structure and mantle composition. However, it seems reasonable to assume that the Mercury we see today has some combination of a relatively low-density crust and a relatively highdensity mantle; uncertainty remains about the presence and types of volatiles [2]. The second uncertainty is the nature of the surface plains units, specifically, are these lava flows and pyroclastics erupted from the interior, or impact-reworked earlier crust [3-5] (Figs. 1-2)? The detection of candidate pyroclastic deposits [4] has very important implications for mantle volatiles. Furthermore, whatever the surface composition, the presence of planet-wide systems of wrinkle ridges and thrust faults implies that a compressive crustal stress regime became dominant at some stage in the planet's history [3, 6]. If the plains units are indeed lava flows, then the fact that the products of the compressive regime deform many plains units suggests that the development of the compressive stresses may have played a vital role in determining when and if surface eruptions of mantle-derived magmas could occur. This would be analogous to the way in which the change with time from extensional to compressive global stresses in the lithosphere of the Moon influenced the viability of erupting magmas from deep mantle sources [7-9]. Analysis: To investigate the relationship between lithospheric stresses and magma eruption conditions [e.g., 9-11] we

  7. The mode of emplacement of Neogene flood basalts in Eastern Iceland: The plagioclase ultraphyric basalts in the Grænavatn group (United States)

    V. Óskarsson, Birgir; B. Andersen, Christina; S. Riishuus, Morten; Sørensen, Erik Vest; Tegner, Christian


    Plagioclase ultraphyric basalt lava with high fraction of solids have a mode of emplacement that is poorly understood. In this study we conduct detailed mapping of a PUB group in eastern Iceland, namely the Grænavatn group, and assess the group architecture, flow morphology and internal structure with additional constraints from petrography, petrology and crystal size distribution, to derive information on emplacement dynamics of plagioclase ultraphyric basalts. We also derive information on the plumbing system of the group with reference to the source of the macrocysts. The group is exposed in steep glacially carved fjords and can be traced for more than 70 km along strike. The flows have mixed architecture of simple and compound flows. Individual flow lobes have thicknesses in the range of 1-24 m and many reach widths and lengths exceeding 1000 m. The flows vary from rubbly to slabby pahoehoe, but are predominantly of pahoehoe type. The aspect ratio of the group and the nature of the flows indicate fissure-fed eruptions. The plagioclase macrocrysts (5-30 mm) are An-rich, exhibit bimodal size distribution and the modal proportions within the group varies from 15-40%. Clinopyroxene macrocrysts are also present ranging from 1-6%. The lowermost flow is thickest and carries the greatest crystal cargo load. The morphology of the lava flows suggests low viscous behavior, at odds with the high crystal content. The very calcic plagioclase macrocrysts (An80-85) are in disequilibrium with the groundmass and plagioclase microlaths therein (An50-70), meaning that the crystal-laden magmas quickly ascended from deeper crustal levels to the surface. The flows with highest crystal content may have maintained high temperatures by heat exchange with the primitive macrocrysts in the flows and developed non-Newtonian behavior such as shear thinning. Such conditions would have enabled the flows to advance rapidly during episodes with high effusion rates forming the simple flows, and

  8. Sharing geographic databases via the world wide web: applications to the whole Italian territory and a focus on lava flow hazard at Mount Etna (United States)

    Tarquini, S.; Favalli, M.; Nannipieri, L.


    DAR survey of the Vesuvius volcano (1 m resolution). Additionally, the GE-based system can be effectively used to present the simulation results from numerical models within a geographic context, to support the assessment and communication of the impact associated to geophysical mass flow on a volcanic area. Finally, we are currently developing a system to interactively navigate a large database of lava flow simulations at Mount Etna (including more than 80,000 simulated vents). The simulations database has been derived using the DEM-driven DOWNFLOW probabilistic code. By elaborating this database a 10m-resolution hazard map has been derived and can be loaded via Web using GE. Upon a click on any location on a map of the volcano, this system is expected to convert on the fly the requested simulation from the database to an image format that can be loaded and visualized by GE.

  9. Non-equilibrium freezing of water-ice in sandy basaltic regoliths and implications for fluidized debris flows on Mars (United States)

    Gooding, J. L.


    Many geomorphic features on Mars were attributed to Earth-analogous, cold-climate processes involving movement of water or ice lubricated debris. Clearly, knowledge of the behavior of water in regolith materials under Martian conditions is essential to understanding the postulated geomorphic processes. Experiments were performed with sand-sized samples of natural basaltic regoliths in order to further elucidate how water/regolith interactions depend upon grain size and mineralogy. The data reveal important contrasts with data for clay-mineral substrates and suggest that the microphysics of water/mineral interactions might affect Martian geomorphic processes in ways that are not fully appreciated. Sand and silt sized fractions of two soils from the summit of Mauna Kea were used as Mars-analogous regolith materials. Temperatures were measured for water/ice phase transitions as wet slurries of individual soil fractions which were cooled or heated at controlled rates under a carbon dioxide atmosphere. Freezing and melting of ice was studied as a function of water/soil mass ratio, soil particle size, and thermal-cycle rate. Comparison tests were done under the same conditions with U.S. Geological Survey standard rock powders.

  10. Terrestrial analogues for lunar impact melt flows (United States)

    Neish, C. D.; Hamilton, C. W.; Hughes, S. S.; Nawotniak, S. Kobs; Garry, W. B.; Skok, J. R.; Elphic, R. C.; Schaefer, E.; Carter, L. M.; Bandfield, J. L.; Osinski, G. R.; Lim, D.; Heldmann, J. L.


    Lunar impact melt deposits have unique physical properties. They have among the highest observed radar returns at S-Band (12.6 cm wavelength), implying that they are rough at the decimeter scale. However, they are also observed in high-resolution optical imagery to be quite smooth at the meter scale. These characteristics distinguish them from well-studied terrestrial analogues, such as Hawaiian pāhoehoe and ´a´ā lava flows. The morphology of impact melt deposits can be related to their emplacement conditions, so understanding the origin of these unique surface properties will help to inform us as to the circumstances under which they were formed. In this work, we seek to find a terrestrial analogue for well-preserved lunar impact melt flows by examining fresh lava flows on Earth. We compare the radar return and high-resolution topographic variations of impact melt flows to terrestrial lava flows with a range of surface textures. The lava flows examined in this work range from smooth Hawaiian pāhoehoe to transitional basaltic flows at Craters of the Moon (COTM) National Monument and Preserve in Idaho to rubbly and spiny pāhoehoe-like flows at the recent eruption at Holuhraun in Iceland. The physical properties of lunar impact melt flows appear to differ from those of all the terrestrial lava flows studied in this work. This may be due to (a) differences in post-emplacement modification processes or (b) fundamental differences in the surface texture of the melt flows due to the melts' unique emplacement and/or cooling environment. Information about the surface properties of lunar impact melt deposits will be critical for future landed missions that wish to sample these materials.

  11. Variable Sources and Differentiation of Lavas from the Copahue-Caviahue Eruptive Complex, Neuquen Argentina (United States)

    Todd, E.; Ort, M. H.


    Caldera collapse (˜180 km2) associated with a large Pliocene pyroclastic eruption and subsequent glacial erosion exposed an extensive and complex cross-section of pre-caldera volcanic history (at least 5 My) at the Copahue-Caviahue Eruptive Center (CCEC) in the Andean Southern Volcanic Zone (SVZ) of Argentina. Lava flows in wall exposures range from olivine-rich basaltic andesite to trachyte, are typically horizontal, vary in abundance and thickness at different wall exposures, and rarely correlate with flows in adjacent sections, although some lava and pyroclastic deposits from adjacent sections are similar in petrography, mineral assemblage, and geochemistry. Bulk-rock geochemical and isotopic data indicate at least two distinct primary melt types contributed to pre-caldera CCEC volcanism, and their differentiates produced a high-K and a low-K series. Incompatible element and isotope systematics suggest they are not related by differentiation of a common parental melt, and less-evolved examples of both types occur throughout the pre-caldera stratigraphic section, suggesting long-lived recharge of the local system by variably-sourced magmas. Petrographic and mineral chemistry evidence indicates that mixing of dissimilar magma types produced compositionally intermediate magmas. The location of the CCEC, rear of the volcanic front (VF), yet trenchward of regional backarc basin (BAB) volcanism, is reflected by the composition of CCEC lavas, which are transitional between local VF and BAB types. Thus, contrasting low- and high-K CCEC magmas in the SVZ rear-arc may reflect local focusing of VF-like (low-K) and BAB-like (high-K) melts.

  12. Age and Duration of the Paraná-Etendeka Flood Basalts and Related Plumbing System (United States)

    Renne, P. R.


    The Paraná-Etendeka Igneous Province (PEIP) comprises a large volume sequence of continental flood basalts presently distributed assymetrically between South America (mainly southern Brazil but also parts of Uruguay, Paraguay and Argentina) and southwestern Africa (Namibia, Angola), following opening of the South Atlantic ocean. The PEIP is dominated by tholeiitic basalts to basaltic andesites, with subordinate silicic rocks spanning the dacite-trachyte-rhyolite fields, which occur as lava flows, sills and dike swarms as well as intrusive complexes closely related to the eruptive rocks. The PEIP has long been subject of 40Ar/39Ar geochronologic and paleomagnetic studies which led to conclude its rapid formation near the Hauterivian stage (~133 Ma) with onward progression to Barremian from the intrusive equivalents exposed northwards. Two decades after publication of the first 40Ar/39Ar ages for the Paraná flood basalts (Renne et al., 1992) we report here an updated study of the age and duration of this magmatic event. We calibrated a set of sixty published and new results to the calibration of Renne et al. (2011), which indicates an inception age of the volcanism now estimated at 135 ± 1 Ma, before the initiation of sea floor spreading. Lava extrusion progressed over ~2 Ma from south to north. A protracted duration of ~10 Ma inferred by Stewart et al. (1996) for PEIP volcanism is clearly incorrect, as also concluded by Thiede and Vasconcelos (2010). Low-Ti mafic magmas prevailed during the earlier stages followed over time by enhanced dominance of their silicic equivalents. Eruption of the high-Ti (mafic and silicic) magmas initiated simultaneously ~0.5 m.y. later, continuing up to ~133 Ma with injection of the Ponta Grossa dyke swarm. Despite several paleomagnetic polarity intervals recorded by the lava piles in the southern (> 27°S) and central (latitudes of ~24-27°S) domains of the Brazilian PEIP, the paleomagnetic data show small dispersion in agreement

  13. Comparison of Inflation Processes at the 1859 Mauna Loa Flow, HI, and the McCartys Flow Field, NM (United States)

    Bleacher, Jacob E.; Garry, W. Brent; Zimbelman, James R.; Crumpler, Larry S.


    Basaltic lavas typically form channels or tubes during flow emplacement. However, the importance of sheet flow in the development of basalt ic terrains received recognition over the last 15 years. George Walke r?s research on the 1859 Mauna Loa Flow was published posthumously in 2009. In this paper he discusses the concept of endogenous growth, or inflation, for the distal portion of this otherwise channeldominated lava flow. We used this work as a guide when visiting the 1859 flow to help us better interpret the inflation history of the McCartys flow field in NM. Both well preserved flows display similar clues about the process of inflation. The McCartys lava flow field is among the you ngest (approx.3000 yrs) basaltic lava flows in the continental United States. It was emplaced over slopes of crust or sa gging along fractures that enable gas release. It is not clear which of these processes is responsible for polygonal terrains, and it is po ssible that one explanation is not the sole cause of this morphology between all inflated flows. Often, these smooth surfaces within an inflated sheet display lineated surfaces and occasional squeeze-ups alon g swale contacts. We interpret the lineations to preserve original fl ow direction and have begun mapping these orientations to better interpret the emplacement history. At the scale of 10s to 100s of meters t he flow comprises multiple topographic plateaus and depressions. Some depressions display level floors with surfaces as described above, while some are bowl shaped with floors covered in broken lava slabs. Th e boundaries between plateaus and depressions are also typically smoo th, grooved surfaces that have been tilted to angles sometimes approaching vertical. The upper margin of these tilted surfaces displays lar ge cracks, sometimes containing squeeze-ups. The bottom boundary with smooth floored depressions typically shows embayment by younger lavas. It appears that this style of terrain represents the

  14. Paleomagnetic secular variation study of Ar-Ar dated lavas flows from Tacambaro area (Central Mexico): Possible evidence of Intra-Jaramillo geomagnetic excursion in volcanic rocks (United States)

    Peña, Rafael Maciel; Goguitchaichvili, Avto; Guilbaud, Marie-Noëlle; Martínez, Vicente Carlos Ruiz; Rathert, Manuel Calvo; Siebe, Claus; Reyes, Bertha Aguilar; Morales, Juan


    More than 350 oriented paleomagnetic cores were obtained for rock-magnetic and paleomagnetic analysis from radiometrically dated (40Ar-39Ar) magmatic rocks occurring in the southern segment (Jorullo and Tacámbaro areas) of the Michoacán-Guanajuato Volcanic Field in the Trans-Mexican Volcanic Belt. Most of the lavas (37) stem from monogenetic volcanoes dated at less than 4 Ma. Two additional sites were sampled from the plutonic basement dated at 33-30 Ma. Primary remanences carried by low-Ti titanomagnetites allowed to determining 34 reliable site-mean directions of mostly normal (27) but also reversed (7) polarities. The mean directions of these two populations are antipodal, and suggest neither major vertical-axis rotations with respect to the North America craton nor tilting in the region for the last 4 Ma (rotation and flattening of the inclination parameters being less than -5.9 ± 3.8 and 0.1 ± 3.9, respectively). The corresponding paleomagnetic pole obtained for Pliocene-Pleistocene times is PLAT = 83.4°, PLON = 2.4° (N = 32, A95 = 2.7°). Virtual geomagnetic poles also contribute to the time averaged field global database and to the paleosecular variation (PSV) investigations at low latitudes from lavas for the last 5 Ma, showing a geomagnetic dispersion value that is in agreement with available PSV models. When comparing the magnetic polarities and corresponding radiometric ages of the studied sites with the Cenozoic geomagnetic polarity time scale (GPTS), a good correlation is observable. This finding underscores the suitability of data obtained on lavas in Central Mexico for contributing to the GPTS. Furthermore, the detection of short-lived geomagnetic features seems possible, since the possible evidence of Intra-Jaramillo geomagnetic excursion could be documented for the first time in these volcanic rocks.

  15. Magmatic inclusions in rhyolites, contaminated basalts, and compositional zonation beneath the Coso volcanic field, California (United States)

    Bacon, C.R.; Metz, J.


    Basaltic lava flows and high-silica rhyolite domes form the Pleistocene part of the Coso volcanic field in southeastern California. The distribution of vents maps the areal zonation inferred for the upper parts of the Coso magmatic system. Subalkalic basalts (Coso volcanic field contain sparse andesitic inclusions (55-61% SiO2). Pillow-like forms, intricate commingling and local diffusive mixing of andesite and rhyolite at contacts, concentric vesicle distribution, and crystal morphologies indicative of undercooling show that inclusions were incorporated in their rhyolitic hosts as blobs of magma. Inclusions were probably dispersed throughout small volumes of rhyolitic magma by convective (mechanical) mixing. Inclusion magma was formed by mixing (hybridization) at the interface between basaltic and rhyolitic magmas that coexisted in vertically zoned igneous systems. Relict phenocrysts and the bulk compositions of inclusions suggest that silicic endmembers were less differentiated than erupted high-silica rhyolite. Changes in inferred endmembers of magma mixtures with time suggest that the steepness of chemical gradients near the silicic/mafic interface in the zoned reservoir may have decreased as the system matured, although a high-silica rhyolitic cap persisted. The Coso example is an extreme case of large thermal and compositional contrast between inclusion and host magmas; lesser differences between intermediate composition magmas and inclusions lead to undercooling phenomena that suggest smaller ??T. Vertical compositional zonation in magma chambers has been documented through study of products of voluminous pyroclastic eruptions. Magmatic inclusions in volcanic rocks provide evidence for compositional zonation and mixing processes in igneous systems when only lava is erupted. ?? 1984 Springer-Verlag.

  16. Characteristics of terrestrial basaltic rock populations: Implications for Mars lander and rover science and safety (United States)

    Craddock, Robert A.; Golombek, Matthew P.


    We analyzed the morphometry of basaltic rock populations that have been emplaced or affected by a variety of geologic processes, including explosive volcanic eruptions (as a proxy for impact cratering), catastrophic flooding, frost shattering, salt weathering, alluvial deposition, and chemical weathering. Morphometric indices for these rock populations were compared to an unmodified population of rocks that had broken off a solidified lava flow to understand how different geologic processes change rock shape. We found that a majority of rocks have an sphericity described as either a disc or sphere in the Zingg classification system and posit that this is a function of cooling fractures in the basalt (Zingg [1935] Schweiz. Miner. Petrogr. Mitt., 15, 39-140). Angularity (roundness) is the most diagnostic morphometric index, but the Corey Shape Factor (CSF), Oblate-Prolate Index (OPI) and deviation from compactness (D) also sometimes distinguished weathering processes. Comparison of our results to prior analyses of rock populations found at the Mars Pathfinder, Spirit, and Curiosity landing sites support previous conclusions. The observation that the size-frequency distribution of terrestrial rock populations follow exponential functions similar to lander and orbital measurements of rocks on Mars, which is expected from fracture and fragmentation theory, indicates that these distributions are being dominantly controlled by the initial fracture and fragmentation of the basalt.

  17. What factors control the superficial lava dome explosivity? (United States)

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


    Dome-forming eruption is a frequent eruptive style; lava domes result from intermittent, slow extrusion of viscous lava. Most dome-forming eruptions produce highly microcrystallized and highly- to almost totally-degassed magmas which have a low explosive potential. During lava dome growth, recurrent collapses of unstable parts are the main destructive process of the lava dome, generating concentrated pyroclastic density currents (C-PDC) channelized in valleys. These C-PDC have a high, but localized, damage potential that largely depends on the collapsed volume. Sometimes, a dilute ash cloud surge develops at the top of the concentrated flow with an increased destructive effect because it may overflow ridges and affect larger areas. In some cases, large lava dome collapses can induce a depressurization of the magma within the conduit, leading to vulcanian explosions. By contrast, violent, laterally directed, explosions may occur at the base of a growing lava dome: this activity generates dilute and turbulent, highly-destructive, pyroclastic density currents (D-PDC), with a high velocity and propagation poorly dependent on the topography. Numerous studies on lava dome behaviors exist, but the triggering of lava dome explosions is poorly understood. Here, seven dome-forming eruptions are investigated: in the Lesser Antilles arc: Montagne Pelée, Martinique (1902-1905, 1929-1932 and 650 y. BP eruptions), Soufrière Hills, Montserrat; in Guatemala, Santiaguito (1929 eruption); in La Chaîne des Puys, France (Puy de Dome and Puy Chopine eruptions). 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 these 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

  18. Bubble Growth in Lunar Basalts (United States)

    Zhang, Y.


    Although Moon is usually said to be volatile-"free", lunar basalts are often vesicular with mm-size bubbles. The vesicular nature of the lunar basalts suggests that they contained some initial gas concentration. A recent publication estimated volatile concentrations in lunar basalts (Saal et al. 2008). This report investigates bubble growth on Moon and compares with that on Earth. Under conditions relevant to lunar basalts, bubble growth in a finite melt shell (i.e., growth of multiple regularly-spaced bubbles) is calculated following Proussevitch and Sahagian (1998) and Liu and Zhang (2000). Initial H2O content of 700 ppm (Saal et al. 2008) or lower is used and the effect of other volatiles (such as carbon dioxide, halogens, and sulfur) is ignored. H2O solubility at low pressures (Liu et al. 2005), concentration-dependent diffusivity in basalt (Zhang and Stolper 1991), and lunar basalt viscosity (Murase and McBirney 1970) are used. Because lunar atmospheric pressure is essentially zero, the confining pressure on bubbles is completely supplied by the overlying magma. Due to low H2O content in lunar basaltic melt (700 ppm H2O corresponds to a saturation pressure of 75 kPa), H2O bubbles only grow in the upper 16 m of a basalt flow or lake. A depth of 20 mm corresponds to a confining pressure of 100 Pa. Hence, vesicular lunar rocks come from very shallow depth. Some findings from the modeling are as follows. (a) Due to low confining pressure as well as low viscosity, even though volatile concentration is very low, bubble growth rate is extremely high, much higher than typical bubble growth rates in terrestrial melts. Hence, mm-size bubbles in lunar basalts are not strange. (b) Because the pertinent pressures are so low, bubble pressure due to surface tension plays a main role in lunar bubble growth, contrary to terrestrial cases. (c) Time scale to reach equilibrium bubble size increases as the confining pressure increases. References: (1) Liu Y, Zhang YX (2000) Earth

  19. H 2O in basalt and basaltic andesite glass inclusions from four subduction-related volcanoes (United States)

    Sisson, T. W.; Layne, G. D.


    Total dissolved H 2O and major element abundances were measured in basalt and basaltic andesite glass inclusions in olivine phenocrysts from Quaternary eruptions of four subduction-related volcanoes to test the hypothesis that low-MgO high-alumina basalts contain high H 2O at depth [1] and to reveal any petrogenetically significant correlations between arc basalt compositions and H 2O contents. Total dissolved H 2O (combined molecular H 2O and OH groups) measured by ion microprobe in mafic glass inclusions from the 1974 eruption of Fuego, Guatemala, reaches 6.2 wt.%. Dissolved H 2O contents decrease in more evolved Fuego glasses. Correlations of H 2O with MgO, Na 2O, K 2O, S and Cl indicate that aqueous fluid exsolution during magma ascent forced crystallization and differentiation of residual liquids. Low-K 2O magnesian high-alumina basalt glass inclusions from the 3 ka eruption of Black Crater (Medicine Lake volcano, California) have low H 2O contents, near 0.2 wt.%, which are consistent with the MORB-like character of these and other primitive lavas of the Medicine Lake region. Basalt and basaltic andesite glass inclusions from Copco Cone and Goosenest volcano on the Cascade volcanic front north of Mt. Shasta have H 2O contents of up to 3.3 wt.%. The range of H 2O contents in Cascade mafic magmas is too large to have resulted solely from enrichment by crystallization and indicates the participation of an H 2O-rich component in magma generation or crustal-level modification. Whereas fluid-absent melting of amphibole-bearing peridotite can account for the H 2O in most mafic arc liquids, the very high H 2O/alkali ratios of the 1974 Fuego eruptives suggest that an aqueous fluid was involved in the generation of Fuego basalts.

  20. High-Ti type N-MORB parentage of basalts from the south Andaman ophiolite suite, India

    Indian Academy of Sciences (India)

    Rajesh K Srivastava; R Chandra; Anant Shastry


    A complete dismembered sequence of ophiolite is well exposed in the south Andaman region that mainly comprises ultramafic cumulates, serpentinite mafic plutonic and dyke rocks, pillow lava, radiolarian chert, and plagiogranite. Pillow lavas of basaltic composition occupy a major part of the Andaman ophiolite suite (AOS). These basalts are well exposed all along the east coast of southern part of the south AOS. Although these basalts are altered due to low-grade metamorphism and late hydrothermal processes, their igneous textures are still preserved. These basalts are mostly either aphyric or phyric in nature. Aphyric type exhibits intersertal or variolitic textures, whereas phyric variety shows porphyritic or sub-ophitic textures. The content of alkalies and silica classify these basalts as sub-alkaline basalts and alkaline basalts. A few samples show basaltic andesite, trachybasalt, or basanitic chemical composition. High-field strength element (HFSE) geochemistry suggests that studied basalt samples are probably derived from similar parental magmas. Al2O3/TiO2 and CaO/TiO2 ratios classify these basalts as high-Ti type basalt. On the basis of these ratios and many discriminant functions and diagrams, it is suggested that the studied basalts, associated with Andaman ophiolite suite, were derived from magma similar to N-MORB and emplaced in the mid-oceanic ridge tectonic setting.

  1. An Overview of Recent Observations on Lava-H2Ointeractions (United States)

    Edwards, B. R.


    Lava flows can be sensitive recorders of their environments of formation (e.g., pillow lava). However, while deposits formed during interactions between lava and frozen water are increasing critical for constraining paleoclimate reconstructions on Earth and Mars, those interactions are subtle and complex. Fortunately, recent observations made during eruptions (2010 Fimmvorduhals/Eyjafjallajokull, Iceland; 2012-13 Tolbachik, Russia; 2013 Veniaminof, Alaska), during large-scale experiments (Syracuse Lava Lab), and on ancient deposits are shedding new light on these complexities. To understand these observations, it is critical to constrain the nature (porosity, permeability, ability to deform) of the boundary between the lava and the substrate. When lava travels directly on top of non-permeable ice, meltwater is produced rapidly enough to significantly accelerate lava movement (e.g., 'hydroplaning' or 'Leidenfrost effect'). The lack of surface permeability also facilitates ingestion of steam into the base of the lava for several minutes on the scale of experiments (dm); anomalously large gas cavities are also present in modern and ancient lava flow deposits inferred to have formed in water/ice-rich environments. When lava is emplaced directly on snow, the permeability of the substrate controls meltwater accumulation, which can facilitate/hinder heat transfer but can also weaken the substrate. Finally, the presence of basal lava flow breccia ('a'a flows) or an earlier erupted tephra blanket at the lava-H2O boundary acts to significantly slow heat transfer. The speed of lava emplacement may also be important. The lavas emplaced during most of the eruptions above were not able to cover a large enough area to quickly generate significant volumes of meltwater. However, at the high discharge rates for the first few days of the Tolbachik eruption (~400 m3 s-1), effusion onto a less permeable surface (e.g., ice instead of snow) could generate significant volumes of meltwater.

  2. The microwave palaeointensity technique and its application to lava

    CERN Document Server

    Hill, M J


    application is required at each power step thus removing the need for accurate reproducibility of absorbed microwave power and also reducing experimental time. This method as well as a previous method developed for use with ceramic samples are described and discussed. The microwave palaeointensity technique has been used successfully in three palaeomagnetic studies (that include rock magnetic and directional analyses). These are a study of historic lava from Mt. Etna, Sicily, a detailed through the flow study of the 1960 Kilauea lava flow, Hawaii and a study of Tertiary Australian lava. Palaeointensity results are compared to observatory records and / or results of previous studies using conventional techniques. The research undertaken, described in this thesis, demonstrates that the microwave palaeointensity technique is a viable technique for use with lava. This enables greater confidence that any palaeointensity results obtained are not affected by sample alteration during experimentation. The suitability ...

  3. 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 e

  4. Observations of actively forming lava tubes and associated structures, Hawaii, part 2 (United States)

    Greeley, R.


    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.

  5. Climate-dependent sediment production: numerical modeling and field observations of variable grain size distributions from heterogeneous hillslope weathering of fractured basalt flows, Kohala Peninsula, Hawaii (United States)

    Murphy, B. P.; Johnson, J. P.


    We present a numerical model for hillslope sediment production that includes climate-dependent chemical weathering rates and bedrock fracture spacings, and predicts how grain size distributions vary with climate and hillslope erosion rate. Understanding sediment preparation, or the in situ reduction of fractured bedrock to coarse sediment by heterogeneous weathering on hillslopes, is critical to understanding the evolution of mountainous landscapes, as sediment supply rates and size distributions can strongly influence river incision rates. The majority of soil production models assume a homogenous substrate and uniform weathering front, and therefore do not track the size of rock fragments and corestones, which become the sediment supplied to channels by hillslope erosion. Our model is inspired by the Kohala Peninsula on the big island of Hawaii, which has a gradient of mean annual precipitation (MAP) spanning over an order of magnitude that has been shown to influence the weathering rates of the basalt. Previous geochemical studies have constrained climate-dependent weathering rates for local soil production. Using these inputs, we developed a kinetics-based numerical model for the chemical weathering of initially fractured basalt into soil and coarse sediment over 150ky. Following first-order reaction kinetics, chemical weathering in the model decreases exponentially with both depth below the surface and time. The model starts with a column of repeating basalt flows (typically 1 m thick), each with fracture spacing distributions consistent with thermal-mechanical cooling characteristics. Each individual fracture-bound block is assumed to weather from the surface inwards, similar in form to a weathering rind. Since the model is constructed of discrete blocks, larger blocks remain as unweathered corestones (the "sediment"), surrounded by weathered material. In addition to a MAP-dependent initial surface weathering rate and rate constant, climate is also reflected

  6. A multi-disciplinary study of deformation of the basaltic cover over fine-grained valley fills: a case study from Eastern Sardinia, Italy (United States)

    Deiana, Rita; Dieni, Iginio; Massari, Francesco; Perri, Maria Teresa; Rossi, Matteo; Brovelli, Alessandro


    The Pliocene to Early Pleistocene volcanic activity which generated the basaltic plateau of the Orosei-Dorgali area in Eastern Sardinia led to the disruption of the local hydrographic network by damming some tracts of the fluvial valleys incised in the granite basement. This resulted in the formation of lacustrine basins, whose fine-grained fills were partly interfingered and eventually covered by younger lava flows. In the SW part of the plateau, close to the Galtellì village, a number of unknown depressions, locally named "Paules," were formed. In order to reconstruct their subsurface structure, two electrical resistivity tomography surveys were carried out across these depressions. The geophysical results, which demonstrate the existence of a disrupted layered system, were used to build a numerical geomechanical model that suggest the depressions originated by local collapses of the basaltic cover due to the compaction of the underlying fine-grained valley fills.

  7. Dissolution of Olivine, Siderite, and Basalt at 80 Deg C in 0.1 M H2SO4 in a Flow Through Process: Insights into Acidic Weathering on Mars (United States)

    Golden, D. C.; Ming, D. W.; Hausrath, E. M.; Morris, R. V.; Niles, P. B.; Achilles, C. N.; Ross, D. K.; Cooper, B. L.; Gonzalex, C. P.; Mertzman, S. A.


    The occurrence of jarosite, other sulfates (e.g., Mg-and Ca-sulfates), and hematite along with silicic-lastic materials in outcrops of sedimentary materials at Meridiani Planum (MP) and detection of silica rich deposits in Gusev crater, Mars, are strong indicators of local acidic aqueous processes [1,2,3,4,5]. The formation of sediments at Meridiani Planum may have involved the evaporation of fluids derived from acid weathering of Martian basalts and subsequent diagenesis [6,7]. Also, our previous work on acid weathering of basaltic materials in a closed hydro-thermal system was focused on the mineralogy of the acid weathering products including the formation of jarosite and gray hematite spherules [8,9,10]. The object of this re-search is to extend our earlier qualitative work on acidic weathering of rocks to determine acidic dissolution rates of Mars analog basaltic materials at 80 C using a flow-thru reactor. We also characterized residual phases, including poorly crystalline or amorphous phases and precipitates, that remained after the treatments of olivine, siderite, and basalt which represent likely MP source rocks. This study is a stepping stone for a future simulation of the formation of MP rocks under a range of T and P.

  8. Petrology and Geochemistry of Jinlongdingzi Active Volcano—the Most Recent Basaltic Explosive Volcano at Longgang

    Institute of Scientific and Technical Information of China (English)

    樊祺诚; 随建立; 等


    The Jinlongdingzi active volcano erupted before 1600a,and it is the latest basaltic explosive volcano at Longgang Volcano.Its volcanic products include the Jinlongdingzi Volcanic cone(elevation 999.4m),the lava flow and the widely-spread volcanic pyroclastic sheet(sihai Pyroclastic Sheet),Jinlongdingzi volcanic rocks are trachybasalts with very similar REE patterns and incompatible element patterns,and their 87Sr/86Sr and 143Nd/144Nd ratios range from 0.704846 ot 0.704921 and from 0.512619 to 0.512646,respectively.It is revealed that the trachybasalt has the character of primary magma derived directly from mantle sources with very little evolution and crust contamination during its ascending.The younger mantle xenoliths demonstrate that the mantle source of the Jinlongdingzi Volcao is hydrous,with relatively low temperature.

  9. A high-resolution 40Ar/39Ar lava chronology and edifice construction history for Ruapehu volcano, New Zealand (United States)

    Conway, Chris E.; Leonard, Graham S.; Townsend, Dougal B.; Calvert, Andrew T.; Wilson, Colin J. N.; Gamble, John A.; Eaves, Shaun R.


    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

  10. Geology of the Mid-Miocene Rooster Comb Caldera and Lake Owyhee Volcanic Field, eastern Oregon: Silicic volcanism associated with Grande Ronde flood basalt (United States)

    Benson, Thomas R.; Mahood, Gail A.


    The Lake Owyhee Volcanic Field (LOVF) of eastern Oregon consists of rhyolitic caldera centers and lava fields contemporaneous with and spatially related to Mid-Miocene Columbia River flood basalt volcanism. Previous studies delineated two calderas in the southeastern part of LOVF near Owyhee Reservoir, the result of eruptions of two ignimbrites, the Tuff of Leslie Gulch and the Tuff of Spring Creek. Our new interpretation is that these two map units are differentially altered parts of a single ignimbrite produced in a major phreatomagmatic eruption at ~ 15.8 Ma. Areas previously mapped as Tuff of Spring Creek are locations where the ignimbrite contains abundant clinoptilolite ± mordenite, which made it susceptible to erosion. The resistant intracaldera Tuff of Leslie Gulch has an alteration assemblage of albite ± quartz, indicative of low-temperature hydrothermal alteration. Our new mapping of caldera lake sediments and pre- and post-caldera rhyolitic lavas and intrusions that are chemically similar to intracaldera Tuff of Leslie Gulch point to a single ~ 20 × 25 km caldera, which we name the Rooster Comb Caldera. Erosion of the resurgently uplifted southern half of the caldera created dramatic exposures of intracaldera Tuff of Leslie Gulch cut by post-caldera rhyolite dikes and intrusions that are the deeper-level equivalents of lava domes and flows that erupted into the caldera lake preserved in exposures to the northeast. The Rooster Comb Caldera has features in common with more southerly Mid-Miocene calderas of the McDermitt Volcanic Field and High Rock Caldera Complex, including formation in a basinal setting shortly after flood basalt eruptions ceased in the region, and forming on eruption of peralkaline ignimbrite. The volcanism at Rooster Comb Caldera postdates the main activity at McDermitt and High Rock, but, like it, begins ~ 300 ky after flood basalt volcanism begins in the area, and while flood basalts don't erupt through the silicic focus, are

  11. Overview of the 2012-13 basaltic fissure eruption of Tolbachik, Kamchatka, Russia (United States)

    Belousov, Alexander; Belousova, Marina; Edwards, Benjamin; Volynetz, Anna; Melnikov, Dmitry; Senyukov, Sergey


    On 27 November 2012 a short-lived swarm of shallow (cinder cone. While explosive activity was rather mild, initial discharge of lava was very high (up to 400 m3/s) and by the end of December 'a'a lava flows had travelled up to 17 km from the vent. SiO2 concentrations for the plagioclase-phyric lava were 54 wt.%, but then decreased to 52 wt.%. In January 2013 lava was transported through a system of lava tubes 1 km long and up to 5 m wide. From tube exit points it propagated in the form of channelized lava streams (velocities 1-3 m/s; discharge rates 30-50 m3/s); on lower slopes of the volcano it propagated mostly as 'a'a flows. Lava channels were frequently dammed by floating clinker and accretionary lava balls, which caused flooding of proximal areas by ropy/shelly/slabby pahoehoe lavas. Locally small volumes of lava were extruded through the upper surfaces and lateral levees of 'a'a lava to form very slowly inflating entrail pahoehoe lava lobes. Starting in mid-February the average intensity of the eruption gradually declined, with sporadic bursts in February and April. By May discharge rates of lava had decreased to approximately 15 m3/s and most of lava started to flow as entrail pahoehoe. By the beginning of June the volume of erupted products (dominantly lavas) reached 0.52km3. The effusion of lava continued until the end of August, when the lava lake in the crater of the active cinder cone became inactive. Weak strombolian outbursts from 1-3 small vents on the bottom of the crater continued until September 5, 2013. Total volume of the erupted products reached approximately 0.7 km3, which is ~0.3 km3 less than estimates for the total eruptive volume from the previous eruption at Tolbachik in 1975-76.

  12. Geologic Mapping and Paired Geochemical-Paleomagnetic Sampling of Reference Sections in the Grande Ronde Basalt: An Example from the Bingen Section, Columbia River Gorge, Washington (United States)

    Sawlan, M.; Hagstrum, J. T.; Wells, R. E.


    We have completed comprehensive geochemical (GC) and paleomagnetic (PM) sampling of individual lava flows from eight reference stratigraphic sections in the Grande Ronde Basalt (GRB), Columbia River Basalt Group [Hagstrum et al., 2009, GSA Ann. Mtg, Portland (abst); Hagstrum et al., 2010, AGU Fall Mtg, San Francisco (abst)]. These sections, distributed across the Columbia Plateau and eastern Columbia River Gorge, contain as many as 30 flows, are up to 670 m thick, span upper magneto-stratigraphic zones R2 and N2, and, in some locations, also contain one or more N1 flows. In concert with GC and PM sampling, we have carried out detailed geologic mapping of these sections, typically at a scale of 1:3,000 to 1:5,000, using GPS, digital imagery from the National Aerial Imagery Program (NAIP), and compilation in GIS. GRB member and informal unit names of Reidel et al. [1989, GSA Sp. Paper 239] generally have been adopted, although two new units are identified and named within the N2 zone. Notably, a distinctive PM direction for intercalated lavas of several lower N2 units indicates coeval eruption of compositionally distinct units; this result contrasts with the scenario of serial stratigraphic succession of GRB units proposed by Reidel et al. [1989]. Our objectives in the mapping include: Confirming the integrity of the stratigraphic sequences by documenting flow contacts and intraflow horizons (changes in joint patterns or vesicularity); assessing fault displacements; and, establishing precisely located samples in geologic context such that selected sites can be unambiguously reoccupied. A geologic map and GC-PM data for the Bingen section, along the north side of the Columbia River, are presented as an example of our GRB reference section mapping and sampling. One of our thicker sections (670 m) along which 30 flows are mapped, the Bingen section spans 7 km along WA State Hwy 14, from near the Hood River Bridge ESE to Locke Lake. This section cuts obliquely through a

  13. Thermal and Dynamic Properties of Volcanic Lava Inferred from Measurements on its Surface (United States)

    Ismail-Zadeh, A.; Korotkii, A.; Kovtunov, D.; Tsepelev, I.; Melnik, O. E.


    Modern remote sensing technologies allow for detecting the absolute temperature at the surface of volcanic lava, and the heat flow could be then inferred from the Stefan-Boltzmann law. Is it possible to use these surface thermal data to constrain the thermal and dynamic conditions inside the lava? We propose a quantitative approach to reconstruct temperature and velocity in the steady-state volcanic lava flow from thermal observations at its surface. This problem is reduced to a combination of the direct and inverse problems of mass- and heat transport. Namely, using known conditions at the lava surface we determine the missing condition at the bottom of lava (the inverse problem) and then search for the physical properties of lava - temperature and flow velocity - inside the lava (the direct problem). Assuming that the lava rheology and the thermal conductivity are temperature-dependent, we determine the flow characteristics in the model domain using an adjoint method. We show that in the case of smooth input data (observations) the lava temperature and the flow velocity can be reconstructed with a high accuracy. The noise imposed on the smooth input data results in a less accurate solution, but still acceptable below some noise level.

  14. From olivine nephelinite, basanite and basalt to peralkaline trachyphonolite and comendite in the Ankaratra volcanic complex, Madagascar: 40Ar/39Ar ages, phase compositions and bulk-rock geochemical and isotopic evolution (United States)

    Cucciniello, Ciro; Melluso, Leone; le Roex, Anton P.; Jourdan, Fred; Morra, Vincenzo; de'Gennaro, Roberto; Grifa, Celestino


    The Ankaratra volcanic field covers an area of 3800 km2 in central Madagascar and comprises of lava flows, lava domes, scoria cones, tuff rings and maars emplaced at different ages (Miocene to Recent). The volcanic products include ultramafic-mafic (olivine-leucite nephelinite, basanite, alkali basalt, hawaiite and tholeiitic basalt), intermediate (mugearite and benmoreite) and felsic rocks (trachyphonolite, quartz trachyte and rhyolite), the latter often peralkaline. The 40Ar/39Ar determinations for mafic lavas yield ages of 17.45 ± 0.12 Ma, 16.63 ± 0.08 Ma and 8.62 ± 0.09 Ma, indicating a prolonged magmatic activity. The mineralogical and geochemical variations suggest that the magmatic evolution of the alkali basalt-hawaiite-mugearite-benmoreite-trachyte series can be accounted for by removal of olivine, feldspars, clinopyroxene, Fe-Ti oxides and accessory phases, producing residual trachytic and trachyphonolitic compositions mineralogically very similar to those of other volcanic areas and tectonic settings. The Ankaratra olivine leucite nephelinites, basanites and tholeiitic basalts do not seem to be associated with significant amounts of evolved comagmatic rocks. The 87Sr/86Sr (0.70504-0.71012), 143Nd/144Nd (0.51259-0.51244) and 206Pb/204Pb (17.705-18.563) isotopic ratios of trachytes and comendite are consistent with open-system processes. However, other trachyphonolites have 143Nd/144Nd (0.51280), 206Pb/204Pb (18.648), 207Pb/204Pb (15.582) and 208Pb/204Pb (38.795) similar to those of mafic rocks, suggesting differentiation processes without appreciable interaction with crustal materials. The Ankaratra volcanism is to be directly linked to a broadly E-W-trending intracontinental extension. A large-scale thermal anomaly, associated with an anomalously hot source region, is not required to explain the Cenozoic magmatism of Madagascar.

  15. Lava lake level as a gauge of magma reservoir pressure and eruptive hazard (United States)

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


    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.

  16. Thermal anomaly at the Earth's surface associated with a lava tube (United States)

    Piombo, Antonello; Di Bari, Marco; Tallarico, Andrea; Dragoni, Michele


    Lava tubes are frequently encountered in volcanic areas. The formation of lava tubes has strong implications on the volcanic hazard during effusive eruptions. The thermal dissipation of lava flowing in a tube is reduced in respect to the lava flowing in an open channel so the lava may threaten areas that would not be reached by flows in open channels: for this reason it is important to detect the presence of lava tubes. In this work we propose a model to detect the presence and the characteristics of lava tubes by their thermal footprint at the surface. We model numerically the temperature distribution and the heat flow, both in the steady and the transient state, and we take into account the principal thermal effects due to the presence of an active lava tube, i.e. the conduction to the ground and the atmosphere, the convection and the radiation in the atmosphere. We assume that lava fluid is at high temperature, in motion inside a sloping tube under the gravity force. The thermal profile across the tube direction, in particular the width of the temperature curve, allows to evaluate the depth of the tube. The values of maximum temperature and of tube depth allow to estimate the area of the tube section. The shape of the temperature curve and its asymmetry can give information about the geometry of the tube. If we observe volcanic areas at different times by thermal cameras, we can detect anomalies and evaluate their causes during an eruption; in particular, we can evaluate whether they are due to active lava flows or not and what is their state. For lava tubes, we can connect thermal anomalies with lava tube position, characteristics and state.

  17. Nature and Significance of the High-Sr Aleutian Lavas (United States)

    Yogodzinski, G. M.; Arndt, S.; Turka, J. R.; Kelemen, P. B.; Vervoort, J. D.; Portnyagin, M.; Hoernle, K.


    Results of the Western Aleutian Volcano Expedition and German-Russian KALMAR cruises include the discovery of seafloor volcanism at the Ingenstrem Depression and at unnamed seamounts 300 km west of Buldir, the westernmost emergent volcano in the Aleutian arc. These discoveries indicate that the surface expression of active Aleutian volcanism goes below sea level just west of Buldir, but is otherwise continuous along the full length of the arc. Many lavas dredged from western Aleutian seamounts are basalts, geochemically similar to basalts from elsewhere in Aleutians and other arcs (La/Yb 4-8, Sr/Y700 ppm Sr), which are mostly plagioclase-hornblende andesites and dacites with low Y and middle-heavy rare-earth elements, fractionated trace element patterns (Sr/Y=50-200, La/Yb=9-25) and MORB-like isotopes (87Sr/86Sr 0.65) with 1250-1700 ppm Sr, 4-7 ppm Y, low abundances of all rare-earth elements (Laandesites from some emergent volcanoes in the western Aleutians, and mixing arrays indicate that it may be present in all Aleutian lavas (e.g., 87Sr/86Sr vs. La/Yb or Sr/Y); however, radiogenic Pb and Sr from subducted sediment renders the high-Sr endmember isotopically invisible in most central and eastern Aleutian lavas. The geochemistry of small monogenetic sea-floor volcanoes--especially those in the back-arc--may be the best opportunity to identify the high-Sr endmember in central and eastern Aleutian locations. The existence of primitive, high-silica lavas in the western Aleutians, where the subducting plate is probably unusually hot, may also provide key observations toward an improved understanding of high-Mg# andesites and dacites from other hot-slab locations, especially in the Cascades and Central Mexico. [1] Zimmer et al., 2010, J. Petrology, v. 51, p. 2411

  18. Volatiles and the tempo of flood basalt magmatism (United States)

    Black, Benjamin A.; Manga, Michael


    Individual flood basalt lavas often exceed 103 km3 in volume, and many such lavas erupt during emplacement of flood basalt provinces. The large volume of individual flood basalt lavas implies correspondingly large magma reservoirs within or at the base of the crust. To erupt, some fraction of this magma must become buoyant and overpressure must be sufficient to encourage failure and dike propagation. The overpressure associated with a new injection of magma is inversely proportional to the total reservoir volume, and as a large magma body heats the surrounding rocks thermally activated creep will relax isotropic overpressure more rapidly. Here, we examine the viability of buoyancy overpressure as a trigger for continental flood basalt eruptions. We employ a new one-dimensional model that combines volatile exsolution, bubble growth and rise, assimilation, and permeable fluid escape from Moho-depth and crustal chambers. We investigate the temporal evolution of degassing and the eruptibility of magmas using the Siberian Traps flood basalts as a test case. We suggest that the volatile inventory set during mantle melting and redistributed via bubble motion controls ascent of magma into and through the crust, thereby regulating the tempo of flood basalt magmatism. Volatile-rich melts from low degrees of partial melting of the mantle are buoyant and erupt to the surface with little staging or crustal interaction. Melts with moderate volatile budgets accumulate in large, mostly molten magma chambers at the Moho or in the lower crust. These large magma bodies may remain buoyant and poised to erupt-triggered by volatile-rich recharge or external stresses-for ∼106 yr. If and when such chambers fail, enormous volumes of magma can ascend into the upper crust, staging at shallow levels and initiating substantial assimilation that contributes to pulses of large-volume flood basalt eruption. Our model further predicts that the Siberian Traps may have released 1019-1020 g of CO2

  19. Stability of Basalt plus Anhydrite plus Calcite at HP-HT: Implications for Venus, the Earth and Mars (United States)

    Martin, A. M.; Righter, K.; Treiman, A. H.


    "Canali" observed at Venus surface by Magellan are evidence for very long melt flows, but their composition and origin remain uncertain. The hypothesis of water-rich flow is not reasonable regarding the temperature at Venus surface. The length of these channels could not be explained by a silicate melt composition but more likely, by a carbonate-sulfate melt which has a much lower viscosity (Kargel et al 1994). One hypothesis is that calcite CaCO3 and anhydrite CaSO4 which are alteration products of basalts melted during meteorite impacts. A famous example recorded on the Earth (Chicxulub) produced melt and gas rich in carbon and sulfur. Calcite and sulfate evaporites are also present on Mars surface, associated with basalts. An impact on these materials might release C- and S-rich melt or fluid. Another type of planetary phenomenon (affecting only the Earth) might provoke a high pressure destabilization of basalt+anhydrite+calcite. Very high contents of C and S are measured in some Earth s magmas, either dissolved or in the form of crystals (Luhr 2008). As shown by the high H content and high fO2 of primary igneous anhydrite-bearing lavas, the high S content in their source may be explained by subduction of an anhydrite-bearing oceanic crust, either directly (by melting followed by eruption) or indirectly (by release of S-rich melt or fluid that metasomatize the mantle) . Calcite is a major product of oceanic sedimentation and alteration of the crust. Therefore, sulfate- and calcite-rich material may be subducted to high pressures and high temperatures (HP-HT) and release S- and C-rich melts or fluids which could influence the composition of subduction zone lavas or gases. Both phenomena - meteorite impact and subduction - imply HP-HT conditions - although the P-T-time paths are different. Some HP experimental/theoretical studies have been performed on basalt/eclogite, calcite and anhydrite separately or on a combination of two. In this study we performed piston

  20. Flow in the shallow mantle in the westernmost Mediterranean: insights from xenoliths in Plio-Pleistocene alkali basalts from the eastern Betic Cordillera (SE Spain) (United States)

    Konc, Zoltán; Hidas, Károly; Garrido, Carlos J.; Tommasi, Andréa; Vauchez, Alain; Padrón Navarta, José Alberto; Marchesi, Claudio; Acosta-Vigil, Antonio; Szabó, Csaba; Varas-Reus, Maria Isabel


    Peridotite mantle xenoliths in Plio-Pleistocene alkali basalts of the eastern Betic Cordillera (Cartagena area, Murcia, SE Spain) provide a snapshot of the structure and composition of the lithospheric mantle at the northern limb of the Alpine Betic-Rif arched belt in the westernmost Mediterranean. The xenoliths are spinel and plagioclase lherzolite with minor harzburgite and wehrlite, displaying porphyroclastic to equigranular textures. Regardless of composition and texture, the Crystal Preferred Orientation (CPO) of olivine shows an axial-[100] pattern characterized by a strong alignment of [100]-axes near or parallel to the peridotite lineation and a girdle distribution of [010]-axes with a maximum normal to the peridotite foliation. This CPO pattern is consistent with ductile deformation accommodated by dislocation creep with dominant activation of the high temperature {0kl}[100] olivine slip system, indicative of deformation by simple shear or combinations of simple shear and pure shear with a transtensional component. Calculated seismic properties are characterized by fast propagation of P-waves and polarization of fast S-waves parallel to olivine [100]-axis, indicating the flow direction. SKS and Pn anisotropy in the eastern Betics can be explained by a lithospheric mantle peridotite with similar fabric to the one displayed by the studied mantle xenoliths. Considering the limited thickness of the mantle lithosphere in the Betics (40-80 km), the measured azimuths and delays of SKS waves in the eastern Betics are consistent with a steeply dipping mantle foliation and a subhorizontal lineation with ENE strike. This geometry of the lithospheric fabrics implies active or frozen mantle flow with a dominantly strike-slip component subparallel to the paleo-Iberian margin. Synkinematic overprinting of mineral assemblages from the garnet-spinel to the plagioclase facies demonstrates 36-40 km uplift continuously accommodated by ductile shear thinning of the

  1. Hydrothermal alteration and diagenesis of terrestrial lacustrine pillow basalts: Coordination of hyperspectral imaging with laboratory measurements (United States)

    Greenberger, Rebecca N; Mustard, John F; Cloutis, Edward A; Mann, Paul; Wilson, Janette H.; Flemming, Roberta L; Robertson, Kevin; Salvatore, Mark R; Edwards, Christopher


    We investigate an outcrop of ∼187 Ma lacustrine pillow basalts of the Talcott Formation exposed in Meriden, Connecticut, USA, focusing on coordinated analyses of one pillow lava to characterize the aqueous history of these basalts in the Hartford Basin. This work uses a suite of multidisciplinary measurements, including hyperspectral imaging, other spectroscopic techniques, and chemical and mineralogical analyses, from the microscopic scale up to the scale of an outcrop.

  2. Origin of the Grande Ronde Basalts, Columbia River Basalt Group (United States)

    Durand, S. R.; Sen, G.; Reidel, S. P.


    The Columbia River basalts are generally thought to have formed by plume melting. Takahashi et al. (1998) suggested that the near-aphyric Grande Ronde Basalts (GR), which comprise ~63% of the CRBG, are essentially primary melts formed by nearly complete fusion of eclogite source rock in the plume and that such melting took place ~2.0 GPa. Durand and Sen (2002) examined phenocrysts and whole rock analyses and concluded that all the basalts are non-primary and, more importantly, that they underwent significant "processing" in shallow crustal magma chambers which erased their higher pressure geochemical signal, thus casting doubt on the validity of the eclogitic plume melting model. Here we report the results of our efforts to simulate the higher pressure histories of GR basalts using COMAGMAT and MELTS software. Our intent was to evaluate (1) whether such melts could be derived from primary melts formed by partial melting of a peridotite source as an alternative to the eclogite model, or if bulk melting of eclogite is required; and (2) at what pressure such primary melts could have been in equilibrium with the mantle. We carried out both forward and inverse modeling. In the forward models we chose different starting melt compositions, all produced in laboratory experiments, from peridotite vs. eclogitic sources. Our starting melts were produced by 6-17% partial melting of the peridotite KLB-1 (Hirose and Kushiro, 1993) and 18-40% melting of eclogites (77SL-582; CRB72-31; Keshav et al., 2004; Takahashi et al., 1998) at 1-3.0 GPa. In a second model, our starting melt composition was the most primitive GR lava with 6.5 wt. % MgO. We extrapolated a linear regression through the GR data to 8 wt. % MgO. We then assumed that such a melt was only olivine-equilibrated, and incrementally added olivine while maintaining equilibrium between olivine and melt using a Kd of 0.3, until a melt in equilibrium with the mantle olivine (Fo89) was found. This composition was fractionated

  3. Late Permian basalts in the northwestern margin of the Emeishan Large Igneous Province: Implications for the origin of the Songpan-Ganzi terrane (United States)

    Li, Hongbo; Zhang, Zhaochong; Santosh, M.; LÜ, Linsu; Han, Liu; Liu, Wei; Cheng, Zhiguo


    SHRIMP zircon U-Pb ages, geochemical and Sr-Nd isotopic data are reported for two types of basalts (Type I and Type II) from a Permian volcanic-pyroclastic succession in the Tubagou section, Baoxing area along the southeastern margin of the Songpan-Ganzi terrane (SGT) in the Sichuan province of SW China. Zircons from the uppermost basaltic flows yield crystallization age of 257.3 ± 2.0 Ma, which may represent the time of culmination the basaltic eruption. Type I shows alkaline affinity with εNd(t) values of + 2.4 to + 2.9, and is characterized by oceanic island basalt (OIB)-type light rare earth element (LREE) and trace-element patterns. In contrast, Type II rocks are tholeiitic, and close to initial rift tholeiite (IRT)-like REE and trace element patterns, and are relatively depleted in highly incompatible elements with slightly negative Nb-Ta anomaly. The εNd(t) values of Type II are between + 1.8 to + 2.2. The geochemical characteristics suggest the Type I has not been significantly crustally contaminated, whereas Type II maybe have experienced minor crustal contamination. Clinopyroxene crystallization temperature is ~ 80-120°C higher than that of the normal asthenospheric mantle, implying anomalous thermal input from mantle source and a possible plume-head origin for the Tubagou lava. The geochemical and isotopic fes, reflecting progressive lithosphere thinning probably through plume-lithosphere interaction. The spatial and temporal coincidence between the Dashibao basalt eruptions, reflecting progressive lithosphere thinning probably through plume-lithosphere interaction. The spatial and temporal coincidence between the Dashibao basalt eruption and continental rifting suggest that continental break-up and the opening of an extensional basin was probably related to the Late Permian Emeishan plume, which triggered the breakup between the SGT and the Yangtze craton.

  4. Long term low latitude and high elevation cosmogenic 3He production rate inferred from a 107 ka-old lava flow in northern Chile; 22°S-3400 m a.s.l. (United States)

    Delunel, Romain; Blard, Pierre-Henri; Martin, Léo C. P.; Nomade, Sébastien; Schlunegger, Fritz


    Available geological calibration sites used to estimate the rate at which cosmogenic 3He is produced at the Earth's surface are mostly clustered in medium to high latitudes. Moreover, most of them have exposure histories shorter than tens of thousands of years. This lack of sites prevents a qualitative assessment of available production models used to convert cosmogenic 3He concentrations into exposure ages and/or denudation rates. It thus limits our ability to take into account the atmospheric, geomagnetic and solar modulation conditions that might have affected the production of cosmogenic nuclides in the past for longer exposure histories and in low latitude regions. We present the cosmogenic 3He production rate inferred from a new geological calibration site located in northern Chile. Five samples were collected on the surface of the largest and best-preserved lava flow of the San Pedro volcano (21.934°S-68.510°W-3390 m a.s.l.), which displays pristine crease-structure features. 40Ar/39Ar dating yields a reliable plateau age of 107 ± 12 ka for the eruption of this lava flow. Eight pyroxene aliquots separated from the surface samples yield a weighted average cosmogenic 3He concentration of 99.3 ± 1.2 Mat g-1 from which a local cosmogenic 3He production rate of 928 ± 101 at g-1 yr-1 is calculated. The local production rate is then scaled to a sea level high latitude (SLHL) reference position using different combinations of geographic spatialization schemes, atmosphere models and geomagnetic field reconstructions, yielding SLHL production rates between 103 ± 11 and 130 ± 14 at g-1 yr-1 consistent with the most recent estimates available from the literature. Finally, we use the same scaling frameworks to re-evaluate the mean global-scale cosmogenic 3He production rate in olivine and pyroxene minerals at 120 ± 16 at g-1 yr-1 from the compilation of previously published calibration datasets.

  5. Subduction-derived solute-rich fluid contributions to lavas of the Trans-Mexican Volcanic Belt (United States)

    LaGatta, A.; Goldstein, S. L.; Langmuir, C. H.; Martin, A.; Carrasco-Nunez, G.; Cai, Y.


    Comparison of the chemical and Sr-Nd-Pb isotope compositions of calcalkaline lavas of the Trans-Mexican Volcanic Belt (TMVB), with subducted sediments (DSDP Site 487) and East Pacific Rise (EPR) basalts, elucidates the effects of solute rich fluids from the subducted ocean crust and sediments on volcanic front lavas. DSDP Site 487 contains a lower unit of hydrothermally affected Mn-rich sediment, and an upper unit of terrigenous detritus. Both sediment types and the subducted EPR basalts have chemical and isotopic distinctions that can be traced to the TMVB lavas, despite the thick continental crust. All these subduction components contribute across the arc, and they contribute most of the Pb and Sr (~50-80%) in the calcalkaline lavas. However, there is an along-arc variation in their contributions. In the western TMVB (e.g. Colima) an aqueous rich melt from subducted EPR basalt predominates (characterized by high Pb/Ce and low Pb and Sr isotope ratios). The central and eastern TMVB (Toluca to Pico de Orizaba) also sees the influence of an aqueous rich melt mixture from the Mn-rich sediment (characterized by high Pb/Ce and high seawater-like Sr isotope ratios, and low Sr isotope ratios), along with increasing contributions eastward from terrigenous sediment (showing higher Pb isotope ratios). Crustal assimilation also becomes more important eastwards (especially in Pico de Orizaba), but never masks the subduction contributions. The Mexican subduction component shows the fluid-mobile (e.g. Sr and Pb) and immobile LILE elements (e.g. Th and La) moving together in their enrichment, suggesting the nature of this component is a solute rich fluid or hydrous silicate melt. Alkali basalts in the TMVB showing 'ocean island basalt-like' trace element patterns for most elements are another important end member for TMVB lavas. The calcalkaline lavas appear to be mixtures of components from the subduction package and the depleted melt-residues of these (high Nb) alkali basalts

  6. Isotopic and trace element geochemistry of alkalic-mafic-ultramafic-carbonatitic complexes and flood basalts in NE India: Origin in a heterogeneous Kerguelen plume (United States)

    Ghatak, Arundhuti; Basu, Asish R.


    The Archean East Indian cratonic margin was affected by the Kerguelen plume (KP) ˜117 Ma, causing flood-basalt eruptions of the Rajmahal-Bengal-Sylhet Traps (RBST). The RBST cover ˜one million km2 in and around the Bengal Basin as alkalic-ultrabasic intrusives in the west and Sikkim in the north, and Sylhet basalts and alkalic-carbonatitic-ultramafic complexes in the Shillong plateau - Mikir hills farther east of the Rajmahal-Bengal Traps. We provide new Nd-Sr-Pb-isotopic and trace element data on 21 unreported discrete lava flows of the Rajmahal Traps, 56 alkalic-carbonatitic-mafic-ultramafic rocks from four alkalic complexes, and three dikes from the Gondwana Bokaro coalfields, all belonging to the RBST. The data allow geochemical correlation of the RBST with some contemporaneous Kerguelen Plateau basalts and KP-related volcanics in the southern Indian Ocean. Specifically, the new data show similarity with previous data of Rajmahal group I-II basalts, Sylhet Traps, Bunbury basalts, and lavas from the southern Kerguelen Plateau, indicating a relatively primitive KP source, estimated as: ɛNd(I) = +2, 87Sr/86Sr(I) = 0.7046, with a nearly flat time-integrated rare earth element (REE) pattern. We model the origin of the uncontaminated RBST basalts by ˜18% batch melting with a 2× chondritic KP source in the spinel-peridotite stability depths of 60-70 km in the mantle. The new geochemical data similar to the Rajmahal group II basalts indicate a light REE enriched average source at ɛNd(I) = -5, 87Sr/86Sr(I) = 0.7069. Our geochemical modeling indicates these lavas assimilated granulites of the Eastern Ghats, reducing the thickness of the continental Indian lithosphere. Lack of an asthenospheric MORB component in the RBST province is indicated by various trace element ratios as well as the Nd-Sr isotopic ratios. Three alkalic complexes, Sung, Samchampi, and Barpung in NE India, and one in Sikkim to the north are of two groups: carbonatites, pyroxenites, lamproites

  7. Space-Time-Isotopic Trends of Snake River Plain Basalts (United States)

    Jean, M. M.; Hanan, B. B.; Shervais, J. W.


    The Snake River Plain (SRP) volcanic province is an 800 km track of basalt extending from the Owyhee Plateau to its current terminus, the Yellowstone Plateau. It is one of several late-Tertiary magmatic terranes that also include the Cascades magmatic arc, the Columbia River basalts, and the Oregon Plateau basalts; all of which are adjacent to the Basin and Range Province extensional system (Hughes and McCurry, 2002). This province represents the track of the Yellowstone plume and consists of basalt that is compositionally similar to ocean-island basalt. This basalt overlies a series of rhyolitic eruptive centers (overlapping caldera complexes, ignimbrites, and caldera-filling eruptions) that signal the arrival of the plume head (Christiansen, 2001) and herald the onset of plume-related rhyolitic and basaltic volcanism (Pierce et al., 2002). Observed within the SRP are two basalt types: the dominant low-K olivine tholeiites and less common high-K alkaline basalts. We report new Sr-, Nd-, and Pb-isotopic analyses of these two basalt types from all three SRP provinces: eastern, central, and western. Low-K tholeiites are enriched in 143Nd/144Nd and 86Sr/87Sr and forms a quasi-linear array in Pb-isotope space, along with Craters of the Moon and eastern SRP basalts. High-K lavas are found largely in the western plain, and have a uniquely different isotopic signature. They are depleted in 143Nd/144Nd and 86Sr/87Sr, relative to the low-K tholeiites, and plot closer to the BSE component of Zindler and Hart (1986). They also share the same Pb-isotopic space with high-K basalts from Smith Prairie (Boise River Group 2 of Vetter and Shervais, 1992). One low-K tholeiite - Eureka North, plots with these high alkali basalts. Mass balance models have demonstrated an increasing plume component from the Yellowstone caldera in the east to the craton edge in the west. The lavas analyzed in this study conform remarkably to this model. The mass fraction of plume component in western

  8. Radionuclide reactions with groundwater and basalts from Columbia River basalt formations

    Energy Technology Data Exchange (ETDEWEB)

    Barney, G.S.


    Chemical reactions of radionuclides with geologic materials found in Columbia River basalt formations were studied. The objective was to determine the ability of these formations to retard radionuclide migration from a radioactive waste repository located in deep basalt. Reactions that can influence migration are precipitation, ion-exchange, complexation, and oxidation-reduction. These reactions were studied by measuring the effects of groundwater composition and redox potential (Eh) on radionuclide sorption on fresh basalt surfaces, a naturally altered basalt, and a sample of secondary minerals associated with a Columbia River basalt flow. In addition, radionuclide sorption isotherms were measured for these materials and reaction kinetics were determined. The radionuclides studied were /sup 137/Cs, /sup 85/Sr, /sup 75/Se, /sup 95m/Tc, /sup 237/Np, /sup 241/Am, /sup 226/Ra and /sup 237/Pu. The Freundlich equation accurately describes the isotherms when precipitation of radionuclides does not occur. In general, sorption increased in the order: basalt < altered basalt < secondary minerals. This increase in sorption corresponds to increasing surface area and cation exchange capacity. The Eh of the system had a large effect on technetium, plutonium, and neptunium sorption. Technetium(VII), Pu(VI), and Np(V) are reduced to Tc(IV), Pu(IV), and Np(IV), respectively, under Eh conditions expected in deep basalt formations. The kinetics of radionuclide sorption and basalt-groundwater reactions were observed over a period of 18 weeks. Most sorption reactions stabilized after about four weeks. Groundwater composition changed the least in contact with altered basalt. Contact with secondary minerals greatly increased Ca, K, and Mg concentrations in the groundwater.

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

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    Nikhil R. Pawar


    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.

  10. Origin of Tertiary to Recent EM- and subduction-like chemical and isotopic signatures in Auca Mahuida region (37°-38°S) and other Patagonian plateau lavas (United States)

    Kay, Suzanne Mahlburg; Jones, Helen A.; Kay, Robert W.


    The alkaline volcanic rocks of the 1.8-0.9 Ma Auca Mahuida and post-mid-Pliocene Rio Colorado backarc volcanic fields east of the Andean Southern Volcanic Zone at ~37°-38°S have pronounced intraplate-like chemical signatures with some striking similarities to oceanic DM-EM1-like lavas of the south Atlantic Tristan da Cunha type. These backarc lavas are considered to have formed as a series of mantle batches typified by 4-7 % melting, with decompression melting initiating in a garnet-bearing mantle above a steepening subduction zone, and final equilibration occurring near the base of a ~65- to 70-km-thick lithosphere at temperatures of ~1,350-1,380 °C. Evolved Auca Mahuida mugearite to trachytic samples are best explained by crystal fractionation with limited mixing of partial melts of recently underplated basalts, in line with isotopic signatures that preclude significant radiogenic contamination in a preexisting refractory crust. Higher Ba/La and subtly higher La/Ta ratios than in nearby ~24-20 Ma primitive basalts or oceanic (OIB) lavas are attributed to the residual effects of slab fluids introduced during a shallow subduction episode recorded in the arc-like chemistry of the adjacent 7-4 Ma Chachahuén volcanic complex. Positive Sr, K and Ba spikes on mantle-normalized patterns of both primitive Auca Mahuida and ~24-20 Ma basalts, like those in EM-like OIB basalts, are attributed to mixing of continental lithosphere into the asthenosphere. In Patagonia, this mixing is suggested to have peaked as the South America continent accommodated to major late Oligocene plate convergence changes, as similar Sr, K and Ba spikes and DM-EM1 signatures are absent in ~50-30 Ma backarc lavas north of 51°S, and all of those south of 51°S. Introduction of an EM1-like component associated with lateral mantle flow of a Tristan da Cunha source is largely precluded by its Cretaceous age and distance to Patagonia.

  11. Glass and mineral chemistry of northern central Indian ridge basalts: Compositional diversity and petrogenetic significance

    Digital Repository Service at National Institute of Oceanography (India)

    Ray, Dwijesh; Banerjee, R.; Iyer, S.D.; Basavalingu, B.; Mukhopadhyay, S.

    seamount shows more fractionated characters (Mg: 0.56-0.57) compared to the outer ridge flank lava of the VT area (Mg: 0.63-0.65). This study concludes that present basalts experienced low-pressure crystallization at a relatively shallow depth...

  12. Robust 24 ± 6 ka 40Ar/39Ar age of a low-potassium tholeiitic basalt in the Lassen region of NE California (United States)

    Turrin, Brent D.; Muffler, L. J. Patrick; Clynne, Michael A.; Champion, Duane E.


    40Ar/39Ar ages on the Hat Creek Basalt (HCB) and stratigraphically related lava flows show that latest Pleistocene tholeiitic basalt with very low K2O can be dated reliably. The HCB underlies ∼ 15 ka glacial gravel and overlies four andesite and basaltic andesite lava flows that yield 40Ar/39Ar ages of 38 ± 7 ka (Cinder Butte; 1.65% K2O), 46 ± 7 ka (Sugarloaf Peak; 1.85% K2O), 67 ± 4 ka (Little Potato Butte; 1.42% K2O) and 77 ± 11 ka (Potato Butte; 1.62% K2O). Given these firm age brackets, we then dated the HCB directly. One sample (0.19% K2O) clearly failed the criteria for plateau-age interpretation, but the inverse isochron age of 26 ± 6 ka is seductively appealing. A second sample (0.17% K2O) yielded concordant plateau, integrated (total fusion), and inverse isochron ages of 26 ± 18, 30 ± 20 and 24 ± 6 ka, all within the time bracket determined by stratigraphic relations; the inverse isochron age of 24 ± 6 ka is preferred. As with all isotopically determined ages, confidence in the results is significantly enhanced when additional constraints imposed by other isotopic ages within a stratigraphic context are taken into account.

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


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


    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...

  14. Emplacement and erosive effects of the south Kasei Valles lava on Mars (United States)

    Dundas, Colin M.; Keszthelyi, Laszlo P.


    Although it has generally been accepted that the Martian outflow channels were carved by floods of water, observations of large channels on Venus and Mercury demonstrate that lava flows can cause substantial erosion. Recent observations of large lava flows within outflow channels on Mars have revived discussion of the hypothesis that the Martian channels are also produced by lava. An excellent example is found in south Kasei Valles (SKV), where the most recent major event was emplacement of a large lava flow. Calculations using high-resolution Digital Terrain Models (DTMs) demonstrate that this flow was locally turbulent, similar to a previously described flood lava flow in Athabasca Valles. The modeled peak local flux of approximately 106 m3 s−1 was approximately an order of magnitude lower than that in Athabasca, which may be due to distance from the vent. Fluxes close to 107 m3 s−1 are estimated in some reaches but these values are probably records of local surges caused by a dam-breach event within the flow. The SKV lava was locally erosive and likely caused significant (kilometer-scale) headwall retreat at several cataracts with tens to hundreds of meters of relief. However, in other places the net effect of the flow was unambiguously aggradational, and these are more representative of most of the flow. The larger outflow channels have lengths of thousands of kilometers and incision of a kilometer or more. Therefore, lava flows comparable to the SKV flow did not carve the major Martian outflow channels, although the SKV flow was among the largest and highest-flux lava flows known in the Solar System.

  15. Measurements of wind friction speeds over lava surfaces and assessment of sediment transport (United States)

    Greeley, Ronald; Iversen, James D.


    Wind velocity profiles were obtained over alluvial plains, lava flows, and a cinder cone in the Mojave Desert to determine the wind shear and the potential for particle transport. It was found that aerodynamic roughness for winds increases nearly a factor of 5 as flow crosses from the alluvium to the lava surface, resulting in wind shear that is 21 percent greater. Thus, wind erosion and sand flux may be substantially enhanced over the lava field. Moreover, wind flow turbulence is enhanced in the wake of the cinder cone, which also increases erosion and sediment transportation by the wind.

  16. Characteristics of well-logging response to lava flow units of the Lower Cretaceous basalts in Songliao Basin%松辽盆地营城组玄武岩流动单元测井响应特征

    Institute of Scientific and Technical Information of China (English)

    黄玉龙; 孙德有; 王璞珺; 曲立才



  17. High-Mg# andesitic lavas of the Shisheisky Complex, Northern Kamchatka: implications for primitive calc-alkaline magmatism (United States)

    Bryant, J. A.; Yogodzinski, G. M.; Churikova, T. G.


    Primitive arc magmatism and mantle wedge processes are investigated through a petrologic and geochemical study of high-Mg# (Mg/Mg + Fe > 0.65) basalts, basaltic andesites and andesites from the Kurile-Kamchatka subduction system. Primitive andesitic samples are from the Shisheisky Complex, a field of Quaternary-age, monogenetic cones located in the Aleutian-Kamchatka junction, north of Shiveluch Volcano, the northernmost active composite volcano in Kamchatka. The Shisheisky lavas have Mg# of 0.66-0.73 at intermediate SiO2 (54-58 wt%) with low CaO (3.0 wt%) and K2O (>1.0 wt%). Olivine phenocryst core compositions of Fo90 appear to be in equilibrium with whole-rock `melts', consistent with the sparsely phyric nature of the lavas. Compared to the Shisheisky andesites, primitive basalts from the region (Kuriles, Tolbachik, Kharchinsky) have higher CaO (>9.9 wt%) and CaO/Al2O3 (>0.60), and lower whole-rock Na2O (andesites. The absence of plagioclase phenocrysts from the primitive andesitic lavas contrasts the plagioclase-phyric basalts, indicating relatively high pre-eruptive water contents for the primitive andesitic magmas compared to basalts. Estimated temperature and water contents for primitive basaltic andesites and andesites are 984-1,143°C and 4-7 wt% H2O. For primitive basalts they are 1,149-1,227°C and 2 wt% H2O. Petrographic and mineral compositions suggest that the primitive andesitic lavas were liquids in equilibrium with mantle peridotite and were not produced by mixing between basalts and felsic crustal melts, contamination by xenocrystic olivine, or crystal fractionation of basalt. Key geochemical features of the Shisheisky primitive lavas (high Ni/MgO, Na2O, Ni/Yb and Mg# at intermediate SiO2) combined with the location of the volcanic field above the edge of the subducting Pacific Plate support a genetic model that involves melting of eclogite or pyroxenite at or near the surface of the subducting plate, followed by interaction of that melt with

  18. An ancient recipe for flood-basalt genesis. (United States)

    Jackson, Matthew G; Carlson, Richard W


    Large outpourings of basaltic lava have punctuated geological time, but the mechanisms responsible for the generation of such extraordinary volumes of melt are not well known. Recent geochemical evidence suggests that an early-formed reservoir may have survived in the Earth's mantle for about 4.5 billion years (ref. 2), and melts of this reservoir contributed to the flood basalt emplaced on Baffin Island about 60 million years ago. However, the volume of this ancient mantle domain and whether it has contributed to other flood basalts is not known. Here we show that basalts from the largest volcanic event in geologic history--the Ontong Java plateau--also exhibit the isotopic and trace element signatures proposed for the early-Earth reservoir. Together with the Ontong Java plateau, we suggest that six of the largest volcanic events that erupted in the past 250 million years derive from the oldest terrestrial mantle reservoir. The association of these large volcanic events with an ancient primitive mantle source suggests that its unique geochemical characteristics--it is both hotter (it has greater abundances of the radioactive heat-producing elements) and more fertile than depleted mantle reservoirs-may strongly affect the generation of flood basalts.

  19. Gabbroic xenoliths in alkaline lavas in the region of Sanganguey Volcano, Nayarit, Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Giosa, T.A.; Nelson, S.A.


    Gabbroic xenoliths occur in alkaline cinder cones and lava flows erupted from vents along five parallel lines trending through the calc-alkaline volcano, Sanganguey in the northwestern portion of the Mexican Volcanic Belt. The xenoliths consist of varying proportions of olivine, clinopyroxene, orthopyroxene, and plagioclase. The complete lack of hydrous phases indicates that the gabbros crystallized under conditions of low PH/sub 2/O. Many xenoliths show textures indicative of a cumulate origin and others exhibit recrystallization indicative of subsolidus reactions prior to incorporation in the host liquids. Reaction between xenolithic minerals and host liquids are also observed. The range of Mg numbers calculated for liquids that would have been in equilibrium with olivines in the xenoliths suggests that these olivines crystallized from magmas such as those represented by either calc-alkaline basaltic andesites and andesites or the more evolved alkalic rocks which occur throughout the area. Crystal fractionation models show that the xenoliths may be related to such magmas. The fact that xenoliths occur most commonly in the alkaline rocks suggests that alkaline magmas rise to the surface more rapidly than the more chemically evolved calc-alkaline and alkaline magmas. Alternatively the lack of xenoliths in the more evolved magmas produced by high level crystal fractionation may indicate that the xenoliths are derived from zones below that from which the differentiated magmas begin their final ascent to the surface.

  20. 塔里木溢流玄武岩的喷发特征%The eruption characteristics of the Tarim flood basalt

    Institute of Scientific and Technical Information of China (English)

    上官时迈; 田伟; 徐义刚; 关平; 潘路


    通过对柯坪地区二叠系野外火山岩露头剖面和英买力、哈拉哈塘井区二叠系火山岩钻井剖面的对比,将塔里木早二叠世溢流玄武岩划分为三个旋回,从老到新依次是:库普库兹满溢流玄武岩旋回(KP),长英质火山碎屑岩旋回(FP)和开派兹雷克溢流玄武岩旋回(KZ).KP旋回以巨厚溢流玄武岩夹凝灰岩为特征,在柯坪露头区和英买力井区均可划分出三层巨厚玄武质熔岩流,至哈拉哈塘井区减少为一层玄武岩流,但长英质火山碎屑岩和熔岩厚度增加.FP旋回在柯坪露头区自下而上包括空落相凝灰岩,熔结凝灰岩,再沉积火山碎屑岩和正常碎屑岩夹火山灰层,该层可与英买力及哈拉哈塘井区的凝灰岩层对比,表明在塔北存在一期面积广泛的长英质火山喷发.KZ旋回以溢流玄武岩为主,在开派兹雷克剖面识别出四期喷发共8层溢流玄武岩和一期安山质玄武岩,每期喷发之间夹少量碎屑岩,但未见长英质火山碎屑岩夹层,该特征与英买力和哈拉哈塘井区的火山层序组合不同,而与塔中溢流玄武岩类似.三个火山旋回的划分表明塔里木大火成岩省经历了“基性溢流玄武岩-酸性火山碎屑岩-基性溢流玄武岩”的演变过程,与Afro-Arabian溢流玄武岩省相似,可进行对比研究.%Integration of field investigation, regional stran'graphic comparison, remote sensing and image interpretation allow us to divide the Tarim Permian flood basalt province into three eruptive cycles listed by decreasing age: Kupukuziman flood basalt ( KP), Felsic pyroclastic rocks (FP), Kaipaizileike flood basalt ( KZ). KP features flood basalt and tuff; in the outcrop in Keping and Yingmaili areas, it can be differentiated into two units containing three thick layers of basaltic lava flows. These three layers decrease to one layer of basaltic lava flow in the Halahatang area; however, felsic pyroclastic rocks and lava layer thicknesses

  1. Near-Primary Oxidized Basalts from the Submarine Vanuatu Arc (United States)

    Gentes, Z.; Kelley, K. A.; Cottrell, E.; Arculus, R. J.


    Near-primary melt compositions (i.e., in equilibrium with >Fo89 olivine) are rare in arc systems. Yet, such melts provide essential views of mantle-derived melts, without further modification by fractional crystallization or other crustal processes, and reveal the diversity of melt compositions that exist in the arc mantle wedge. Here, we present new measurements of naturally glassy, near-primary olivine-hosted melt inclusions from one dredge of Evita seamount (SS07/2008 NLD-02) in the southern Vanuatu arc system. Two distinct basalt types were identified in hand sample upon collection, based on contrasting phenocryst assemblage (Type 1: 1% phenocrysts; Type 2: 15% phenocrysts). We selected melt inclusions from each type and determined major elements, S, and Cl by EMP, H2O and CO2 by FTIR, trace elements by LA-ICP-MS, and Fe3+/∑Fe ratios by XANES. Melt inclusions from both lava types show equilibrium with ≥Fo90 olivine, consistent with host olivine compositions, and thus are near-primary melt compositions that have escaped major modification since departing the mantle wedge. Both have similar maximum dissolved H2O (~2.3 wt.%), high Mg# (48-75), and are basalt to basaltic andesite (SiO2 49-55 wt.%). However, the two lava types have very different major and trace element compositions. Inclusions from Type 1 show relatively flat REE patterns and classic negative anomalies in Nb and Ta, and positive anomalies in Pb and Sr typical of normal arc basalts, and have Fe3+/∑Fe ratios similar to global arc basalts (~0.24). In contrast, melt inclusions from Type 2 exhibit steeply sloped REE patterns with strong depletions in the HREE that suggest garnet in the source lithology for these magmas, either in the subducting slab or the mantle wedge. Moreover, the Type 2 inclusions have high La/Yb (29.5-43) and Sr/Y (50-58), which are classically attributed to partial melting of the basaltic slab, although these inclusions are basaltic, not andesitic. Type 2 inclusions also

  2. Lava Eruption and Emplacement: Using Clues from Hawaii and Iceland to Probe the Lunar Past (United States)

    Needham, D. H.; Hamilton, C. W.; Bleacher, J. E.; Whelley, P. L.; Young, K. E.; Scheidt, S. P.; Richardson, J. A.; Sutton, S. S.


    We investigate the 2014/15 Holuhraun, Iceland and December 1974 Kilauea, Hawaii eruptions to improve understanding of relationships between eruption dynamics and final lava flow morphology. Insights are used to deduce the origin of Rima Bode on the Moon.

  3. A network of lava tubes as the origin of Labyrinthus Noctis and Valles Marineris on Mars (United States)

    Leone, Giovanni


    The role of lava tube networks and lava channels is reassessed as the primordial stage of the volcano-erosional processes that formed the Labyrinthus Noctis-Valles Marineris system instead of a tectonic origin. The combined use of CTX, CRISM, HiRISE imagery, and MOLA profiles has provided valuable insight in the evolution of pit chains into fossae first and then chasmata later due to mass wasting processes caused by the erosional effect of the lava flows that draped Valles Marineris and other outflow channels. Although a quantitative evaluation of eruption rates is difficult even with digital terrain models (DTMs) because of the mixing between new flows and paleoflows, a comparison with Elysium and other Tharsis outflow channels suggests that the availability of lava supply is correlated to their widths. The images of ubiquitous lava flows rather than sporadic light-toned deposits strengthen the role of lava over that of water in the erosional processes that formed Labyrinthus Noctis and carved Valles Marineris like many other outflow channel on Mars. The erosional evolution of the outflow channels shows an increasing trend of age and a decreasing trend of depth from the sources on Tharsis to the mouths at Chryse Planitia. This finding, coupled with the observation of lava flows mantling Chryse Planitia, may have profound implications for the water inventories thought to have filled the lowlands with an ocean.

  4. Petrology, geochemistry, and age of low-Ti mare-basalt meteorite Northeast Africa 003-A: A possible member of the Apollo 15 mare basaltic suite (United States)

    Haloda, Jakub; Týcová, Patricie; Korotev, Randy L.; Fernandes, Vera A.; Burgess, Ray; Thöni, Martin; Jelenc, Monika; Jakeš, Petr; Gabzdyl, Pavel; Košler, Jan


    C/h) suggest that the parent melt of NEA 003-A crystallized in the lower part of a lava flow containing cumulate olivine (˜10%) and was probably derived from more primitive picritic magma by fractional crystallization processes. Sm-Nd dating yields an age of 3.09 ± 0.06 Ga which corresponds to the period of lower Eratosthenian lunar volcanic activity, and the near-chondritic ɛNd value of -0.4 ± 0.3 indicates that the meteorite could be derived from a slightly enriched mantle source similar to the Apollo 15 green glasses. Ar-Ar step release results are inconsistent with Sm-Nd ages suggesting that NEA 003-A was exposed to one or more impact events. The most extensive event took place at 1.8 Ga and the shock intensity was likely between 28 and 45 GPa. The absence of solar Ar suggests that NEA 003-A has not been directly exposed at the lunar surface but the cosmic ray exposure age of 209 ± 6 Ma suggests that NEA 003-A resided in the upper regolith for part of its history.

  5. Deformation of poorly consolidated sediment during shallow emplacement of a basalt sill, Coso Range, California (United States)

    Duffield, W.A.; Bacon, C.R.; Delaney, P.T.


    A 150-m-long, wedge-shaped unit of folded and faulted marly siltstone crops out between undeformed sedimentary rocks on the north flank of the Coso Range, California. The several-meter-thick blunt end of this wedge abuts the north margin of a basaltic sill of comparable thickness. Chaotically deformed siltstone crops out locally at the margin of this sill, and at one locality breccia pipes about one meter in diameter crosscut the sill. The sill extends about 1 km south up the paleoslope, where it merges through continuous outcrop with a lava flow that in turn extends 1.4 km to a vent area marked by more than 100 m of agglutinate and scoria. Apparently, lava extruded at this vent flowed onto unconsolidated sediments, burrowed into them, and fed a sill at about 40 m depth within the sedimentary sequence. The sill initially propagated by wedging between sedimentary beds, but eventually began to push some beds ahead of itself, forming a remarkable train of folds in the process. The sediments apparently were wet at the time of sill emplacement, because hydrothermal alteration is common near the contact between the two rock types and because the breccia pipes that crosscut the sill apparently resulted from phreatic explosions of pore water heated at the base of the cooling sill. Comparison of deformation of the host material at the Coso locality with that reportedly caused by emplacement of sills elsewhere indicates that the character of deformation differs greatly among the various localities. The specific response of host material depends upon such parameters as initial properties of magma and host material, rate of sill growth and attendant rate of strain of host material, and depth of sill emplacement. Some properties may change considerably during an intrusive-deformational episode, thus complicating accurate reconstruction of such an event. ?? 1986 Springer-Verlag.

  6. Primitive off-rift basalts from Iceland and Jan Mayen

    DEFF Research Database (Denmark)

    Debaille, Vinciane; Trønnes, Reidar G.; Brandon, Alan D.


    and appear to be contaminated at a shallow level. The 187Os/188Os ratios in the remaining lavas with >30 ppt Os (n = 17) range between 0.12117 and 0.13324. These values are surprisingly low for oceanic island basalts and include some samples that are less than putative present-day primitive upper mantle (PUM...... with 187Os/188Os of 0.1296). These low 187Os/188Os preclude significant shallow-level contamination from oceanic crust. The 187Os/188Os ratios for Jan Mayen lavas are less than PUM, severely limiting the presence of any continental crust in their mantle source. A positive correlation between 143Nd/144Nd...... and 187Os/188Os ratios in Iceland and Jan Mayen lavas likely reflects the presence in their source of ancient subcontinental lithosphere that has undergone incompatible trace element enrichment that did not affect the Re-Os system. In addition, the Jan Mayen lava isotopic signature cannot be explained...

  7. Alteration in Hawaiian Drill Core: An analog for Martian basalts (United States)

    Calvin, W. M.; Fraeman, A.; Ehlmann, B. L.; Lautze, N. C.


    The Humu'ula Groundwater Research Project (HGRP) drilled their first continuously-cored hole in the saddle region of the big island of Hawaii in March of 2013. Temperatures at the bottom of the hole were unexpectedly high and reached over 100C. The core traverses various lava flows, representing the shield-building phase of the island and the lithology is dominantly basalt with varying amounts of plagioclase and olivine phenocrysts. Logging of the core noted that discontinuous alteration became prevalent starting at ~ 1 km depth. In May of 2015 we collected 780 infrared spectra of the core from depths of 0.97 to 1.76 km using our portable field spectrometer with a contact probe and field of view of 10 mm. Many of the spectra are unaltered, showing mafic mineralogy (augite or augite with olivine). Minerals from aqueous alteration include clinochlore, micaceous minerals likely mixed with other common phyllic alteration products, and three groups of spectral types associated with zeolites. This suite of minerals suggests alteration was initiated from higher temperature and moderate pH fluids. Based on the field reconnaissance spectroscopy, 25 sections were cut that represent the alteration diversity for thin section and subsequent detailed petrologic analyses. Eight of these sections were examined using the Ultra-Compact Imaging Spectrometer (UCIS) prototype instrument at the Jet Propulsion Laboratory. UCIS collects spectra at 80 μm / pixel and identifies the same alteration mineralogy as the bulk samples, but clearly shows that the alteration occurs in veins and vugs. Unaltered olivine and pyroxene phenocrysts occur in the groundmass adjacent to highly altered vugs, and are preserved throughout the section surveyed. Given the limited alteration and abundant preservation of olivine to depths of 1.5 km, the core may be representative of alteration in moderate pH environments on Mars, where unaltered basaltic materials occur in close proximity to alteration products

  8. Palaeointensities from Pliocene lava sequences in Iceland: emphasis on the problem of Arai plot with two linear segments (United States)

    Tanaka, Hidefumi; Yamamoto, Yuhji


    Palaeointensity experiments were carried out to a sample collection from two sections of basalt lava flow sequences of Pliocene age in north central Iceland (Chron C2An) to further refine the knowledge of the behaviour of the palaeomagnetic field. Selection of samples was mainly based on their stability of remanence to thermal demagnetization as well as good reversibility in variations of magnetic susceptibility and saturation magnetization with temperature, which would indicate the presence of magnetite as a product of deuteric oxidation of titanomagnetite. Among 167 lava flows from two sections, 44 flows were selected for the Königsberger-Thellier-Thellier experiment in vacuum. In spite of careful pre-selection of samples, an Arai plot with two linear segments, or a concave-up appearance, was often encountered during the experiments. This non-ideal behaviour was probably caused by an irreversible change in the domain state of the magnetic grains of the pseudo-single-domain (PSD) range. This is assumed because an ideal linear plot was obtained in the second run of the palaeointensity experiment in which a laboratory thermoremanence acquired after the final step of the first run was used as a natural remanence. This experiment was conducted on six selected samples, and no clear difference between the magnetic grains of the experimented and pristine sister samples was found by scanning electron microscope and hysteresis measurements, that is, no occurrence of notable chemical/mineralogical alteration, suggesting that no change in the grain size distribution had occurred. Hence, the two-segment Arai plot was not caused by the reversible multidomain/PSD effect in which the curvature of the Arai plot is dependent on the grain size. Considering that the irreversible change in domain state must have affected data points at not only high temperatures but also low temperatures, fv ≥ 0.5 was adopted as one of the acceptance criteria where fv is a vectorially defined

  9. Signatures of the source for the Emeishan flood basalts in the Ertan area: Pb isotope evidence

    Institute of Scientific and Technical Information of China (English)


    The Emeishan flood basalts can be divided into high-Ti (HT) basalt (Ti/Y>500) and low-Ti (LT) basalt (Ti/Y<500). Sr, Nd isotopic characteristics of the lavas indicate that the LT- and the HT-type magmas originated from distinct mantle sources and parental magmas. The LT-type magma was derived from a shallower lithospheric mantle, whereas the HT-type magma was derived from a deeper mantle source that may be possibly a mantle plume. However, few studies on the Emeishan flood basalts involved their Pb isotopes, especially the Ertan basalts. In this paper, the authors investigated basalt samples from the Ertan area in terms of Pb isotopes, in order to constrain the source of the Emeishan flood basalts. The ratios of 206Pb/204Pb (18.31-18.41), 207Pb/204Pb (15.55-15.56) and 208Pb/204Pb (38.81-38.94) are significantly higher than those of the depleted mantle, just lying between EM I and EM II. This indicates that the Emeishan HT basalts (in the Ertan area) are the result of mixing of EMI end-member and EMII end-member.

  10. Lava effusion rate definition and measurement--A review (United States)

    Calvari, Sonia; Dehn, Jonathan; Harris, A.


    Measurement of effusion rate is a primary objective for studies that model lava flow and magma system dynamics, as well as for monitoring efforts during on-going eruptions. However, its exact definition remains a source of confusion, and problems occur when comparing volume flux values that are averaged over different time periods or spatial scales, or measured using different approaches. Thus our aims are to: (1) define effusion rate terminology; and (2) assess the various measurement methods and their results. We first distinguish between instantaneous effusion rate, and time-averaged discharge rate. Eruption rate is next defined as the total volume of lava emplaced since the beginning of the eruption divided by the time since the eruption began. The ultimate extension of this is mean output rate, this being the final volume of erupted lava divided by total eruption duration. Whether these values are total values, i.e. the flux feeding all flow units across the entire flow field, or local, i.e. the flux feeding a single active unit within a flow field across which many units are active, also needs to be specified. No approach is without its problems, and all can have large error (up to ∼50%). However, good agreement between diverse approaches shows that reliable estimates can be made if each approach is applied carefully and takes into account the caveats we detail here. There are three important factors to consider and state when measuring, giving or using an effusion rate. First, the time-period over which the value was averaged; second, whether the measurement applies to the entire active flow field, or a single lava flow within that field; and third, the measurement technique and its accompanying assumptions.

  11. Topographic and Stochastic Influences on Pahoehoe Lava Lobe Emplacement (United States)

    Hamilton, Christopher W.; Glaze, Lori S.; James, Mike R.; Baloga, Stephen M.


    A detailed understanding of pahoehoe emplacement is necessary for developing accurate models of flow field development, assessing hazards, and interpreting the significance of lava morphology on Earth and other planetary surfaces. Active pahoehoe lobes on Kilauea Volcano, Hawaii, were examined on 21-26 February 2006 using oblique time-series stereo-photogrammetry and differential global positioning system (DGPS) measurements. During this time, the local discharge rate for peripheral lava lobes was generally constant at 0.0061 +/- 0.0019 m3/s, but the areal coverage rate of the lobes exhibited a periodic increase every 4.13 +/- 0.64 minutes. This periodicity is attributed to the time required for the pressure within the liquid lava core to exceed the cooling induced strength of its margins. The pahoehoe flow advanced through a series of down slope and cross-slope breakouts, which began as approximately 0.2 m-thick units (i.e., toes) that coalesced and inflated to become approximately meter-thick lobes. The lobes were thickest above the lowest points of the initial topography and above shallow to reverse facing slopes, defined relative to the local flow direction. The flow path was typically controlled by high-standing topography, with the zone directly adjacent to the final lobe margin having an average relief that was a few centimeters higher than the lava inundated region. This suggests that toe-scale topography can, at least temporarily, exert strong controls on pahoehoe flow paths by impeding the lateral spreading of the lobe. Observed cycles of enhanced areal spreading and inflated lobe morphology are also explored using a model that considers the statistical likelihood of sequential breakouts from active flow margins and the effects of topographic barriers.

  12. Village environs as source of nitrate contamination in groundwater: a case study in basaltic geo-environment in central India. (United States)

    Reddy, D V; Nagabhushanam, P; Peters, Edward


    Nitrate is one of the common contaminants in the present day groundwaters resulting from increased population associated with poor sanitary conditions in the habitat area and increased agricultural activity. The hydrochemical measurements on water samples from a virgin watershed, situated in the basaltic geo-environment, have become necessary as the groundwater is the only source of drinking water for the villagers of the area. High preferential recharge conditions prevail in the area due to fractures in the solid basaltic lava flows. Instead of dilution due to fresh recharge, the post-monsoon hydrochemical concentrations in the groundwater are observed to have increased probably due to fast migration of pollutants to the aquifer through preferential recharge. As a result, the deep aquifer waters are more contaminated with hazardous nitrate than the shallow waters. Further, the village environ wells are more polluted with nitrate than the agriculture areas which could be attributed to the unhygienic sanitary conditions and livestock waste dump pits in the villages. This study suggests proper management of the sewage system and creation of suitable dump yard for the livestock and household waste to minimize the level of nitrate pollution in the well waters of village environs.

  13. Extended correlation of the Paleogene Faroe Islands and East Greenland plateau basalts

    DEFF Research Database (Denmark)

    Søager, Nina; Holm, Paul Martin


    New analytical data are presented for 13 enriched high-Ti tholeiitic basalts from the top of the Faroese lava pile that was formed by the time of break-up of the North Atlantic  56-55  Ma ago and are located on the eastern continental margin of the Atlantic Ocean. The samples fall in three groups....../204Pb = 17.59-18.30 while the High-Ti3 group has 206Pb/204Pb = 18.88-19.12. The three Faroese lava groups can be correlated with the East Greenland syn-breakup basalt formations using their geochemistry, lava morphology and phenocryst contents. The High-Ti1 group correlates with the Milne Land......-Ti1 and Milne Land Formation lavas have a higher content of most incompatible elements compared to High-Ti2 and Geikie Plateau Formation. This is unexpected because the Zr/Nb ratio indicates that the High-Ti2 and Geikie Plateau Formation lavas are formed by lower degrees of melting. An explanation may...

  14. Surface Textures and Features Indicative of Endogenous Growth at the McCartys Flow Field, NM, as an Analog to Martian Volcanic Plains (United States)

    Bleacher, Jacob E.; Crumpler, L. S.; Garry, W. B.; Zimbelman, J. R.; Self, S.; Aubele, J. C.


    Basaltic lavas typically form channels or tubes, which are recognized on the Earth and Mars. Although largely unrecognized in the planetary community, terrestrial inflated sheet flows also display morphologies that share many commonalities with lava plains on Mars. The McCartys lava flow field is among the youngest (approx.3000 yrs) basaltic flows in the continental United States. The southwest sections of the flow displays smooth, flat-topped plateaus with irregularly shaped pits and hummocky inter-plateau units that form a polygonal surface. Plateaus are typically elongate in map view, up to 20 m high and display lineations within the glassy crust. Lineated surfaces occasionally display small < 1m diameter lava coils. Lineations are generally straight and parallel each other, sometimes for over 100 meters. The boundaries between plateaus and depressions are also lineated and tilted to angles sometimes approaching vertical. Plateau-parallel cracks, sometimes containing squeeze-ups, mark the boundary between tilted crust and plateau. Some plateau depressions display level floors with hummocky surfaces, while some are bowl shaped with floors covered in broken lava slabs. The lower walls of pits sometimes display lateral, sagged lava wedges. Infrequently, pit floors display the upper portion of a tumulus from an older flow. In some places the surface crust has been disrupted forming a slabby texture. Slabs are typically on the scale of a meter or less across and no less than 7-10 cm thick. The slabs preserve the lineated textures of the undisturbed plateau crust. It appears that this style of terrain represents the emplacement of an extensive sheet that experiences inflation episodes within preferred regions where lateral spreading of the sheet is inhibited, thereby forming plateaus. Rough surfaces represent inflation-related disruption of pahoehoe lava and not a a lava. Depressions are often the result of non-inflation and can be clearly identified by lateral

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

    Directory of Open Access Journals (Sweden)

    Kevin Allred


    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.

  16. Contrasting geochemistry and metamorphism of pillow basalts in metamorphic complexes from Aysén, S. Chile (United States)

    Hervé, F.; Aguirre, L.; Sepúlveda, V.; Morata, D.


    The geochemistry of pillow basalts from the Chonos Metamorphic Complex (CMC) and the Eastern Andes Metamorphic Complex of Aysén (EAMC) indicates contrasting tectonic environments for these basic lavas. They have E-MORB and continental alkaline affinities, respectively. The MORB-like basalts are metamorphosed in the pumpellyite-actinolite metamorphic facies, with mineral associations indicative of relatively high P/T metamorphism. The continental alkali basalts exhibit pumpellyite-chlorite assemblages developed in a low to intermediate P/T regime. These contrasting eruptive and metamorphic settings agree with recently established age differences between the complexes, and invalidate direct correlation between them.

  17. Sustaining persistent lava lakes: Observations from high-resolution gas measurements at Villarrica volcano, Chile (United States)

    Moussallam, Yves; Bani, Philipson; Curtis, Aaron; Barnie, Talfan; Moussallam, Manuel; Peters, Nial; Schipper, C. Ian; Aiuppa, Alessandro; Giudice, Gaetano; Amigo, Álvaro; Velasquez, Gabriela; Cardona, Carlos


    Active lava lakes - as the exposed upper part of magmatic columns - are prime locations to investigate the conduit flow processes operating at active, degassing volcanoes. Persistent lava lakes require a constant influx of heat to sustain a molten state at the Earth's surface. Several mechanisms have been proposed to explain how such heat transfer can operate efficiently. These models make contrasting predictions with respect to the flow dynamics in volcanic conduits and should result in dissimilar volatile emissions at the surface. Here we look at high-frequency SO2 fluxes, plume composition, thermal emissions and aerial video footage from the Villarrica lava lake in order to determine the mechanism sustaining its activity. We found that while fluctuations are apparent in all datasets, none shows a stable periodic behaviour. These observations suggest a continuous influx of volatiles and magma to the Villarrica lava lake. We suggest that ascending volatile-rich and descending degassed magmas are efficiently mixed within the volcanic conduit, resulting in no clear periodic oscillations in the plume composition and flux. We compare our findings to those of other lava lakes where equivalent gas emission time-series have been acquired, and suggest that gas flux, magma viscosity and conduit geometry are key parameters determining which flow mechanism operates in a given volcanic conduit. The range of conduit flow regimes inferred from the few studied lava lakes gives a glimpse of the potentially wide spectrum of conduit flow dynamics operating at active volcanoes.

  18. Insights into the dynamics of the Nyiragongo lava lake level (United States)

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


    Nyiragongo volcano, in North Kivu, Democratic Republic of Congo, is among the most active volcanoes in Africa and on Earth. Since the first European observations in the late 19th Century, its eruptive activity mostly concentrated into its main crater, with the presence of a persistent lava lake from at least 1928 to 1977 and since 2002. The size, shape and elevation of this lava lake have evolved through time, modifying the topography of the main crater. In January 1977 and 2002, the uppermost magmatic system of Nyiragongo, including the lava lake, was drained during flank eruptions. These flank events caused major disasters, mostly due to the exceptionally fast-moving lava flows and the presence of a dense population living at foot of this volcano. Despite a large scientific interest and societal concern, the study of the eruptive activity of Nyiragongo remains limited by climate and vegetation conditions that, most of the time, limit use of satellite remote sensing techniques, and recurrent armed conflicts in the Kivu region, which sometimes prevent field access to the main crater. Here we focus on the dynamics of the Nyiragongo lava lake level and its relationship with the volcanic plumbing system by describing the historical and recent lava lake activity and presenting new quantitative observations using close-range photogrammetry, a Stereographic Time-Lapse Camera (STLC) system and high-resolution satellite SAR and InSAR remote sensing. Results highlight that, contrary to the interpretation found in some recent publications, the lava lake drainages appear to be the consequence and not the cause of the 1977 and 2002 flank eruptions. Two types of short-term lava lake level variations are observed. The first one corresponds to cyclic metre-scale variations attributed to gas piston activity. The STLC data recorded in September 2011 show hour-scale gas piston cycles reaching up to 3.8 m, which are interpreted to be related to gas accumulation and release in the

  19. Joint inversion of 3-D seismic, gravimetric and magnetotelluric data for sub-basalt imaging in the Faroe-Shetland Basin (United States)

    Heincke, B.; Moorkamp, M.; Jegen, M.; Hobbs, R. W.


    collected along parallel lines by a shipborne gradiometer and the marine MT data set is composed of 41 stations that are distributed over the whole investigation area. Logging results from a borehole located in the central part of the investigation area enable us to derive parameter relationships between seismic velocities, resistivities and densities that are adequately describe the rock property behaviors of both the basaltic lava flows and sedimentary layers in this region. In addition, a 3-D reflection seismic survey covering the central part allows us to incorporate the top of basalt and other features as constraints in the joint inversions and to evaluate the quality of the final results. Literature: D. Colombo, M. Mantovani, S. Hallinan, M. Virgilio, 2008. Sub-basalt depth imaging using simultaneous joint inversion of seismic and electromagnetic (MT) data: a CRB field study. SEG Expanded Abstract, Las Vegas, USA, 2674-2678. M. Jordan, J. Ebbing, M. Brönner, J. Kamm , Z. Du, P. Eliasson, 2012. Joint Inversion for Improved Sub-salt and Sub-basalt Imaging with Application to the More Margin. EAGE Expanded Abstracts, Copenhagen, DK. M. Moorkamp, B. Heincke, M. Jegen, A.W.Roberts, R.W. Hobbs, 2011. A framework for 3-D joint inversion of MT, gravity and seismic refraction data. Geophysical Journal International, 184, 477-493.

  20. Formation processes of the 1909 Tarumai and the 1944 Usu lava domesin Hokkaido, Japan

    Directory of Open Access Journals (Sweden)

    I. Yokoyama


    Full Text Available The formation of the two particular lava domes in Hokkaido, Japan is described and interpreted mainly from geophysical viewpoints. The 1909 eruption of Tarumai volcano was not violent but produced a lava dome over four days. The growth rate of the dome is discussed under the assumption that the lava flow was viscous and plastic fluid during its effusion. By Hagen-Poiseuille?s Law, the length of the conduit of the lava dome is rather ambiguously determined as a function of viscosity of the magma and diameter of the conduit. The 1944 Usu dome extruded as a parasitic cone of Usu volcano, not in the crater, but in a flat cornfield at the foot of the volcano. From the beginning to the end for more than 17 months, seismometric and geodetic observations of the dome activity were carried out by several pioneering geophysicists. Utilizing their data, pseudo growth curves of the dome at each stage can be drawn. The lava ascended rather uniformly, causing uplift of the ground surface until half-solidified lava reached the surface six months after the deformation began. Thereafter, the lava dome added lateral displacements and finally achieved its onion structure. These two lava domes are of contrasting character, one is andesitic and formed quickly while the other is dacitic and formed slowly, but both of them behaved as viscous and plastic flows during effusion. It is concluded that both the lava domes formed by uplift of magma forced to flow through the conduits, analogous to squeezing toothpaste out of a tube.

  1. Evidence for extensive olivine-rich basalt bedrock outcrops in Ganges and Eos chasmas, Mars (United States)

    Edwards, C. S.; Christensen, P. R.; Hamilton, V. E.


    Several localized outcrops of olivine-enriched bedrock have been previously identified in the Ganges and Eos Chasma area on the eastern end of Valles Marineris with the Thermal Emission Imaging System multispectral images. These outcrops form a layer in the walls of Ganges Chasma and appear to be the remnants of a once continuous unit, which was mapped over ~100 km. In this study we further characterize the composition (forsterite content of ~0.68), olivine abundance (10 to >15%), thermal inertia (>600 JK-1 m-2 s-1/2, consistent with in-place rocky material), vertical dimension (~60 to ~220 m), extent (>1100 km laterally), volume (~9.9 × 104 km3), dip (~0.013°NE), and continuity of this layer utilizing Thermal Emission Spectrometer hyperspectral, Thermal Emission Imaging System multispectral, and Mars Orbiter Laser Altimeter elevation data. Morphologic data from high-resolution imagery display a relatively unmantled, rough, and pitted surface associated with the olivine-enriched material, consistent with thermal inertia data. Four possibilities for the origin of the olivine-enriched unit are (1) volcanism associated with tectonic rifting of the Valles Marineris system, (2) a volcaniclastic flow deposit, (3) an intrusive mafic sill, or (4) a discrete episode in Martian history during which flood lavas were erupted onto the surface. The most likely origin is an eruptive event consisting of compositionally uniform flood lavas originating from a primitive mantle source region, possibly associated with the initiation of Tharsis volcanism. This unit is one of the largest continuous compositional units found on Mars and is strikingly similar to other olivine-enriched deposits identified in previous studies where compositional, morphologic, and thermophysical similarities are observed. These similarities may indicate that there was a period in early Martian history, where compositionally uniform and extensive olivine-enriched flood basalts were erupted on the Martian

  2. Alteration of Crystalline and Glassy Basaltic Protolith by Seawater as Recorded by Drill Core and Drill Cutting Samples (United States)

    Fowler, A. P.; Zierenberg, R. A.; Schiffman, P.


    The major and trace element composition of hydrothermally altered basaltic drill core and drill cutting samples from the seawater recharged Reykjanes geothermal system in Iceland are compared to unaltered surface flows from the Reykjanes Peninsula compiled from the literature. Trace element characteristics of deep (>2000 m) core samples record bimodal compositions similar to trace element enriched and trace element depleted Reykjanes Ridge basalts. Drill cuttings (350-3000 m) overwhelmingly reflect the more common trace element enriched igneous precursor. Crystalline protoliths (dolerite dykes and pillow lava cores) are depleted in Cs, Rb, K, and Ba (± Pb and Th) relative to an unaltered equivalent, despite variations in the extent of alteration ranging from from minor chloritization with intact igneous precursor minerals through to extensive chloritization and uralitization. Glassy protoliths (dyke margins, pillow edges, and hyaloclastites) show similar depletions of Cs, Rb, K, and Ba, but also show selective depletions of the light rare earth elements (LREE) La, Ce, Pr, Nd and Eu due to extensive recrystallization to hydrothermal hornblende. Lower grade alteration shows less pronounced decoupling of LREE and is likely controlled by a combination of Cl complexation in the seawater-derived recharge fluid, moderated by anhydrite and epidote precipitation. These results suggest that alteration of glassy protolith in seawater-recharged systems is an important contribution to the consistently light rare earth and Eu enriched patterns observed in seafloor hydrothermal fluids from basaltic systems. An important conclusion of this study is that that drill cuttings samples are strongly biased toward unaltered rock and more resistant alteration minerals including epidote and quartz potentially resulting in misidentification of lithology and extent of alteration.

  3. What factors control superficial lava dome explosivity?