Sample records for ma volcanic localities

  1. Volcanism at 1.45 Ma within the Yellowstone Volcanic Field, United States (United States)

    Rivera, Tiffany A.; Furlong, Ryan; Vincent, Jaime; Gardiner, Stephanie; Jicha, Brian R.; Schmitz, Mark D.; Lippert, Peter C.


    Rhyolitic volcanism in the Yellowstone Volcanic Field has spanned over two million years and consisted of both explosive caldera-forming eruptions and smaller effusive flows and domes. Effusive eruptions have been documented preceding and following caldera-forming eruptions, however the temporal and petrogenetic relationships of these magmas to the caldera-forming eruptions are relatively unknown. Here we present new 40Ar/39Ar dates for four small-volume eruptions located on the western rim of the second-cycle caldera, the source of the 1.300 ± 0.001 Ma Mesa Falls Tuff. We supplement our new eruption ages with whole rock major and trace element chemistry, Pb isotopic ratios of feldspar, and paleomagnetic and rock magnetic analyses. Eruption ages for the effusive Green Canyon Flow (1.299 ± 0.002 Ma) and Moonshine Mountain Dome (1.302 ± 0.003 Ma) are in close temporal proximity to the eruption age of the Mesa Falls Tuff. In contrast, our results indicate a period of volcanism at ca 1.45 Ma within the Yellowstone Volcanic Field, including the eruption of the Bishop Mountain Flow (1.458 ± 0.002 Ma) and Tuff of Lyle Spring (1.450 ± 0.003 Ma). These high-silica rhyolites are chemically and isotopically distinct from the Mesa Falls Tuff and related 1.3 Ma effusive eruptions. The 40Ar/39Ar data from the Tuff of Lyle Spring demonstrate significant antecrystic inheritance, prevalent within the upper welded ash-flow tuff matrix, and minimal within individual pumice. Antecrysts are up to 20 kyr older than the eruption, with subpopulations of grains occurring every few thousand years. We interpret these results as an indicator for the timing of magmatic pulses into a growing magmatic system that would ultimately erupt the Tuff of Lyle Spring, and which we more broadly interpret as the tempo of crustal accumulation associated with bimodal magmatism. We propose a system whereby chemically, isotopically, and temporally distinct, isolated small-volume magma batches are

  2. Local and remote infrasound from explosive volcanism (United States)

    Matoza, R. S.; Fee, D.; LE Pichon, A.


    Explosive volcanic eruptions can inject large volumes of ash into heavily travelled air corridors and thus pose a significant societal and economic hazard. In remote volcanic regions, satellite data are sometimes the only technology available to observe volcanic eruptions and constrain ash-release parameters for aviation safety. Infrasound (acoustic waves ~0.01-20 Hz) data fill this critical observational gap, providing ground-based data for remote volcanic eruptions. Explosive volcanic eruptions are among the most powerful sources of infrasound observed on earth, with recordings routinely made at ranges of hundreds to thousands of kilometers. Advances in infrasound technology and the efficient propagation of infrasound in the atmosphere therefore greatly enhance our ability to monitor volcanoes in remote regions such as the North Pacific Ocean. Infrasound data can be exploited to detect, locate, and provide detailed chronologies of the timing of explosive volcanic eruptions for use in ash transport and dispersal models. We highlight results from case studies of multiple eruptions recorded by the International Monitoring System and dedicated regional infrasound networks (2008 Kasatochi, Alaska, USA; 2008 Okmok, Alaska, USA; 2009 Sarychev Peak, Kuriles, Russian Federation; 2010 Eyjafjallajökull, Icleand) and show how infrasound is currently used in volcano monitoring. We also present progress towards characterizing and modeling the variability in source mechanisms of infrasound from explosive eruptions using dedicated local infrasound field deployments at volcanoes Karymsky, Russian Federation and Sakurajima, Japan.

  3. Problems in the K-Ar dating of Quaternary volcanic rocks younger than 1 Ma

    International Nuclear Information System (INIS)

    Takaoka, Nobuo


    The assumption that the 40 Ar/ 36 Ar ratio of Ar trapped in volcanic rocks at eruption is atmospheric often gives a large systematic error in the K-Ar dating of Quaternary volcanic rocks younger than 1 Ma. There are two possible sources of error, the existence of excess Ar and mass-fractionated, initial Ar. The major source of excess Ar is supposed to be magma. The 40 Ar/ 36 Ar ratio for magmatic Ar in the North-East Japan arc is tentatively estimated to be 340±10 from measurements of Ar in large phenocrysts separated from Quaternary volcanic rocks. Separation of phenocrysts is the most effective to decrease the systematic error caused by excess Ar. The mass-fractionation of initial Ar should give the 38 Ar/ 36 Ar ratio which was changed from the atmospheric ratio. This can be checked by determining the 38 Ar/ 36 Ar ratio in samples. Since the systematic error caused by the mass-fractionated, initial Ar increases greatly with the increasing atmospheric Ar correction, it is important to correct the result for the mass-fractionation. Correction formulae are given. The error sources other than those mentioned above are uncertainty in the blank correction and instabilities in the sensitivity of spectrometer and the Ar isotopic ratio measurement. In order to increase accuracy of the K-Ar age obtained, to check the systematic errors by measuring samples together with standard samples is of great importance in the K-Ar dating of very young volcanic rocks. (author)

  4. Ma

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    Ingrid Berthon-Moine


    Full Text Available Ma (2009 is a single channel video of a mother and child walking together side by side, holding hands. The title is reminiscent of the affectionate nickname for a mother, 'Ma', but also a concealed way to convey maternal ambivalence. Maternal ambivalence is the result of the tension between the idealisation of motherhood and women’s lived experience of mothering. The maternal struggle finds its source in the difficulty of identifying with the ideological representation of the mother. This image still conveys an idealistic and nostalgic, patriarchal image of maternal love bounded by culture and history.

  5. Meteorological Controls on Local and Regional Volcanic Ash Dispersal. (United States)

    Poulidis, Alexandros P; Phillips, Jeremy C; Renfrew, Ian A; Barclay, Jenni; Hogg, Andrew; Jenkins, Susanna F; Robertson, Richard; Pyle, David M


    Volcanic ash has the capacity to impact human health, livestock, crops and infrastructure, including international air traffic. For recent major eruptions, information on the volcanic ash plume has been combined with relatively coarse-resolution meteorological model output to provide simulations of regional ash dispersal, with reasonable success on the scale of hundreds of kilometres. However, to predict and mitigate these impacts locally, significant improvements in modelling capability are required. Here, we present results from a dynamic meteorological-ash-dispersion model configured with sufficient resolution to represent local topographic and convectively-forced flows. We focus on an archetypal volcanic setting, Soufrière, St Vincent, and use the exceptional historical records of the 1902 and 1979 eruptions to challenge our simulations. We find that the evolution and characteristics of ash deposition on St Vincent and nearby islands can be accurately simulated when the wind shear associated with the trade wind inversion and topographically-forced flows are represented. The wind shear plays a primary role and topographic flows a secondary role on ash distribution on local to regional scales. We propose a new explanation for the downwind ash deposition maxima, commonly observed in volcanic eruptions, as resulting from the detailed forcing of mesoscale meteorology on the ash plume.

  6. Local to global: a collaborative approach to volcanic risk assessment (United States)

    Calder, Eliza; Loughlin, Sue; Barsotti, Sara; Bonadonna, Costanza; Jenkins, Susanna


    -economic conditions tending to influence longer term well-being and recovery. The volcanological community includes almost 100 Volcano Observatories worldwide, the official institutions responsible for monitoring volcanoes. They may be dedicated institutions, or operate from national institutions (geological surveys, universities, met agencies). They have a key role in early warning, forecasting and long term hazard assessment (often in the form of volcanic hazards maps). The complexity of volcanic systems means that once unrest begins there are multiple potential eruptive outcomes and short term forecasts can change rapidly. This local knowledge of individual volcanoes underpins hazard and risk assessments developed at national, regional and global scales. Combining this local expertise with the knowledge of the international research community (including interdisciplinary perspectives) creates a powerful partnership. A collaborative approach is therefore needed to develop effective volcanic risk assessments at regional to global scale. The World Organisation of Volcano Observatories is a Commission of IAVCEI, alongside other Commissions such as 'Hazard and Risk' (with an active working group on volcanic hazards maps) and the 'Cities and Volcanoes' Commission. The Global Volcano Model network is a collaborative initiative developing hazards and risk information at national to global scales, underpinned by local expertise. Partners include IAVCEI, Smithsonian Institution, International Volcanic Health Hazard Network, VHub and other initiatives and institutions.

  7. Local seismic hazard assessment in explosive volcanic settings by 3D numerical analyses (United States)

    Razzano, Roberto; Pagliaroli, Alessandro; Moscatelli, Massimiliano; Gaudiosi, Iolanda; Avalle, Alessandra; Giallini, Silvia; Marcini, Marco; Polpetta, Federica; Simionato, Maurizio; Sirianni, Pietro; Sottili, Gianluca; Vignaroli, Gianluca; Bellanova, Jessica; Calamita, Giuseppe; Perrone, Angela; Piscitelli, Sabatino


    This work deals with the assessment of local seismic response in the explosive volcanic settings by reconstructing the subsoil model of the Stracciacappa maar (Sabatini Volcanic District, central Italy), whose pyroclastic succession records eruptive phases ended about 0.09 Ma ago. Heterogeneous characteristics of the Stracciacappa maar (stratification, structural setting, lithotypes, and thickness variation of depositional units) make it an ideal case history for understanding mechanisms and processes leading to modifications of amplitude-frequency-duration of seismic waves generated at earthquake sources and propagating through volcanic settings. New geological map and cross sections, constrained with recently acquired geotechnical and geophysical data, illustrate the complex geometric relationships among different depositional units forming the maar. A composite interfingering between internal lacustrine sediments and epiclastic debris, sourced from the rim, fills the crater floor; a 45 meters thick continuous coring borehole was drilled in the maar with sampling of undisturbed samples. Electrical Resistivity Tomography surveys and 2D passive seismic arrays were also carried out for constraining the geological model and the velocity profile of the S-waves, respectively. Single station noise measurements were collected in order to define natural amplification frequencies. Finally, the nonlinear cyclic soil behaviour was investigated through simple shear tests on the undisturbed samples. The collected dataset was used to define the subsoil model for 3D finite difference site response numerical analyses by using FLAC 3D software (ITASCA). Moreover, 1D and 2D numerical analyses were carried out for comparison purposes. Two different scenarios were selected as input motions: a moderate magnitude (volcanic event) and a high magnitude (tectonic event). Both earthquake scenarios revealed significant ground motion amplification (up to 15 in terms of spectral acceleration

  8. Origin of the ca. 50 Ma Linzizong shoshonitic volcanic rocks in the eastern Gangdese arc, southern Tibet (United States)

    Liu, An-Lin; Wang, Qing; Zhu, Di-Cheng; Zhao, Zhi-Dan; Liu, Sheng-Ao; Wang, Rui; Dai, Jin-Gen; Zheng, Yuan-Chuan; Zhang, Liang-Liang


    The origin of the Eocene shoshonitic rocks within the upper part of the extensive Linzizong volcanic succession (i.e., the Pana Formation) in the Gangdese arc, southern Tibet remains unclear, inhibiting the detailed investigations on the crust-mantle interaction and mantle dynamics that operate the generation of the coeval magmatic flare-up in the arc. We report mineral composition, zircon U-Pb age and zircon Hf isotope, whole-rock element and Sr-Nd-Hf isotope data for the Pana Formation volcanic rocks from Pangduo, eastern Gangdese arc in southern Tibet. The Pana volcanic rocks from Pangduo include basalts, basaltic andesites, and dacites. SIMS and LA-ICPMS zircon U-Pb dating indicates that the Pangduo dacites were erupted at 50 ± 1 Ma, representing the volcanic equivalent of the coeval Gangdese Batholith that define a magmatic flare-up at 51 ± 1 Ma. The Pangduo volcanic rocks are exclusively shoshonitic, differing from typical subduction-related calc-alkaline volcanic rocks. The basalts have positive whole-rock ƐNd(t) (+1.7) and ƐHf(t) (+3.8) with high Zr abundances (121-169 ppm) and Zr/Y ratios (4.3-5.2), most likely derived from the partial melting of an enriched garnet-bearing lithospheric mantle that was metasomatized by subduction-related components with input from asthenosphere. Compared to the basalts, similar trace elemental patterns and decreased whole-rock ƐNd(t) (-3.5 to -3.3) and ƐHf(t) (-2.5 to -1.6) of the basaltic andesites can be attributed to the input of the ancient basement-derived material of the central Lhasa subterrane into the basaltic magmas. The coherent whole-rock Sr-Nd-Hf isotopic compositions ((87Sr/86Sr)i = 0.7064-0.7069, ƐNd(t) = -6.0 to -5.2, ƐHf(t) = -5.6 to -5.0) and varying zircon ƐHf(t) (-6.0 to +4.1) of the dacites can be interpreted by the partial melting of a hybrid lower crust source (juvenile and ancient lower crust) with incorporation of basement-derived components. Calculations of zircon-Ti temperature and whole

  9. Origin Of Black Shale (Marl) Formation Aided By Continuous Volcanism For 10Ma Including Oceanic Anoxic Event, OAE2 (93-93.5 Ma) In The Eagle Ford Formation In South Texas (United States)

    Chakrabarty, P.; Basu, A. R.


    We report LA-ICPMS U-Pb ages and Hf isotopes of zircons, petrography, major and trace elements and X-ray diffraction (XRD) analyses of whole rock black shales(marls) from volcanic subsurface as well as surface exposure ash beds of the Eagle Ford and Boquillas Formations in South Texas. Zircons from the middle part of the 300ft long Eagle Ford cores yield ages of 93.2±1.66 Ma, 94.13±1.25 Ma and 93.7±1.9 Ma. These ages are consistent with the Cenomanian-Turonian (C-T) age of deposition in three contiguous cores with spatial separation of 140 miles. An approximate 10Ma duration of deposition of volcanic ash and marl, at a rate of 28ft/Ma for the Eagle Ford is suggested from the 85.76 to 95.5 Ma ages. These ages are from the Eagle Ford ash beds, below the Austin Chalk and above the Buda Limestone and cover the Oceanic Anoxic Event 2 at the C-T boundary. Zircons from 7 ash beds in the surface exposures of the Boquillas Formation near Del Rio, yield ages between 84.63 Ma - 90.91 Ma, implying younger than C-T boundary ages for these samples. The mineralogy, major and trace elements of the ash beds suggest their source from nearby arc-derived calc-alkaline volcanism. The ɛHf(T) of the analyzed ash bed zircons yield values between 0 - +8 averaging at +3.5, clearly indicating a mantle component in the host magmas of the zircons. This initial range of ɛHf(T) is similar to arc-volcanism signatures such as the Quaternary andesitic volcanism in Central Mexico. Petrographic analyses of marls away from the visible tuff layer contain phenocrysts of biotite, alkali feldspar and andesitic rock fragments. The whole rock marl with high concentration of some transition metals (V, Zn, Ni, Pb, Mo) and relatively higher MgO and TiO2 contents indicate contemporaneous arc volcanic activity at the time of marl deposition. XRD of subsurface Eagle Ford bulk marl samples from different depths in 4 cores, show volcanogenic clays, such as montmorillonite, vermiculite, dickite and halloysite

  10. Volcanic tremor and local earthquakes at Copahue volcanic complex, Southern Andes, Argentina (United States)

    Ibáñez, J. M.; Del Pezzo, E.; Bengoa, C.; Caselli, A.; Badi, G.; Almendros, J.


    In the present paper we describe the results of a seismic field survey carried out at Copahue Volcano, Southern Andes, Argentina, using a small-aperture, dense seismic antenna. Copahue Volcano is an active volcano that exhibited a few phreatic eruptions in the last 20 years. The aim of this experiment was to record and classify the background seismic activity of this volcanic area, and locate the sources of local earthquakes and volcanic tremor. Data consist of several volcano-tectonic (VT) earthquakes, and many samples of back-ground seismic noise. We use both ordinary spectral, and multi-spectral techniques to measure the spectral content, and an array technique [Zero Lag Cross Correlation technique] to measure the back-azimuth and apparent slowness of the signals propagating across the array. We locate VT earthquakes using a procedure based on the estimate of slowness vector components and S-P time. VT events are located mainly along the border of the Caviahue caldera lake, positioned at the South-East of Copahue volcano, in a depth interval of 1-3 km below the surface. The background noise shows the presence of many transients with high correlation among the array stations in the frequency band centered at 2.5 Hz. These transients are superimposed to an uncorrelated background seismic signal. Array solutions for these transients show a predominant slowness vector pointing to the exploited geothermal field of "Las Maquinitas" and "Copahue Village", located about 6 km north of the array site. We interpret this coherent signal as a tremor generated by the activity of the geothermal field.

  11. Asthenospheric counterflows beneath the moving lithosphere of Central and East Asia in the past 90 Ma: volcanic and tomographic evidence (United States)

    Rasskazov, Sergei; Chuvashova, Irina; Kozhevnikov, Vladimir


    Asthenospheric counterflows, accompanied motions of the lithosphere in Central and East Asia, are defined on basis of spatial-temporal activity of mantle sources [Rasskazov et al., 2012; Rasskazov, Chuvashova, 2013; Chuvashova, Rasskazov, 2014] and the tomographic model of the Rayleigh wave group velocities [Kozhevnikov et al., 2014]. The opposite fluxes are defined relative to centers of convective instability (low-velocity anomalies), expressed by thinning of the mantle transition layer under Southwestern Gobi (44 °N, 95 °E) and Northern Baikal (52 °N, 108 °E). Cretaceous-Paleogene volcanic fields in Southern Gobi are shifted eastwards relative to the former anomaly over 600 km with the opposite sub-lithospheric flux at depths of 150-300 km. Likewise, the Late Tertiary Vitim volcanic field is shifted relative to the latter anomaly over 100-200 km. We suggest that the Gobi and Baikal asthenospheric counterflows contributed to the rollback mechanism of downgoing slab material from the Pacific under the eastern margin of Asia in the Cretaceous-Paleogene and Early-Middle Miocene. The east-west Gobi reverse flux, caused by differential block motions in front of the Indo-Asian convergence, resulted in the oblique Honshu-Korean flexure of the Pacific slab that propagated beneath the continental margin, while the Japan Sea was quickly opening at about 15 Ma. The Baikal N60°W reverse flux, originated due to oncoming traffic between Eurasia and the Pacific plate, entailed the formation of the Baikal Rift Zone and direct Hokkaido Amur slab flexure [Rasskazov et al., 2004]. The study is supported by the Russian Foundation for Basic Research (Grant 14-05-31328). References Chuvashova I.S., Rasskazov S.V. Magmatic sources in the mantle of the evolving Earth. Irkutsk: Publishing House of the Irkutsk State University, 2014. 310 p. (in Russian) Kozhevnikov V.M., Seredkina A.I., Solovei O.A. 3D mantle structure of Central Asia from Rayleigh wave group velocity dispersion

  12. Transition of neogene arc volcanism in central-western Hokkaido, viewed from K-Ar ages, style of volcanic activity, and bulk rock chemistry

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    Hirose, Wataru; Iwasaki, Miyuki; Nakagawa, Mitsuhiro [Hokkaido Univ., Sapporo (Japan)


    Spatial and temporal variations in late Cenozoic volcanism of southwestern Hokkaido at the northern end of NE-Japan arc have been clarified by 261 K-Ar and 76 FT ages including 49 newly determined K-Ar ages, volcanic stratigraphy, physical volcanology and whole-rock geochemistry. Arc volcanism characterized by rocks with low-Ti and Nb, and by across-arc increase in K{sub 2}O content in these rocks has continued at least since 12 Ma. Based on volcanic stratigraphy, physical volcanology and whole-rock geochemistry, volcanism after 12 Ma can be subdivided into 4 stages, 12-5, 5-1.7, and 1.7-0 Ma. The volcanism from 12 Ma to 5 Ma extended northward widely compared with distribution of Quaternary arc volcanism (1.7-0 Ma). This suggests that the arc trench junction between Kuril and NE-Japan arc's trenches was located about 100 km northward from the present position. Since around 5 Ma until 1.7 Ma, different type of volcanism under local extension field, characterized by a group of monogenetic volcanoes of alkali basalt and shield volcanoes of calc-alkaline andesite, had occurred at northern end of the volcanic region (Takikawa-Mashike region). During and after this volcanism, the northern edge of arc volcanism in the area has migrated southward. This suggests that the trench junction has migrated about 100 km southward since {approx}5 Ma. The quaternary arc volcanism (1.7-0 Ma) has been restricted at the southern part of the region. The volcanism since 12 Ma might be influenced by oblique subduction of Pacific plate beneath Kuril arc, resulting in the formation of local back arc basin at the junction and to southward migration of the trench junction. (author)

  13. A Conceptual Model of Future Volcanism at Medicine Lake Volcano, California - With an Emphasis on Understanding Local Volcanic Hazards (United States)

    Molisee, D. D.; Germa, A.; Charbonnier, S. J.; Connor, C.


    Medicine Lake Volcano (MLV) is most voluminous of all the Cascade Volcanoes ( 600 km3), and has the highest eruption frequency after Mount St. Helens. Detailed mapping by USGS colleagues has shown that during the last 500,000 years MLV erupted >200 lava flows ranging from basalt to rhyolite, produced at least one ash-flow tuff, one caldera forming event, and at least 17 scoria cones. Underlying these units are 23 additional volcanic units that are considered to be pre-MLV in age. Despite the very high likelihood of future eruptions, fewer than 60 of 250 mapped volcanic units (MLV and pre-MLV) have been dated reliably. A robust set of eruptive ages is key to understanding the history of the MLV system and to forecasting the future behavior of the volcano. The goals of this study are to 1) obtain additional radiometric ages from stratigraphically strategic units; 2) recalculate recurrence rate of eruptions based on an augmented set of radiometric dates; and 3) use lava flow, PDC, ash fall-out, and lahar computational simulation models to assess the potential effects of discrete volcanic hazards locally and regionally. We identify undated target units (units in key stratigraphic positions to provide maximum chronological insight) and obtain field samples for radiometric dating (40Ar/39Ar and K/Ar) and petrology. Stratigraphic and radiometric data are then used together in the Volcano Event Age Model (VEAM) to identify changes in the rate and type of volcanic eruptions through time, with statistical uncertainty. These newly obtained datasets will be added to published data to build a conceptual model of volcanic hazards at MLV. Alternative conceptual models, for example, may be that the rate of MLV lava flow eruptions are nonstationary in time and/or space and/or volume. We explore the consequences of these alternative models on forecasting future eruptions. As different styles of activity have different impacts, we estimate these potential effects using simulation

  14. ∼1400 Ma alkali metasomatic event in the sericite deposits and basal Aravalli volcanic rocks of Udaipur region, Rajasthan

    International Nuclear Information System (INIS)

    Padmakumari, V.M.; Sreenivas, B.; Srinivasan, R.; Gopalan, K.; Roy, A.B.


    Paleosols are residual soil profiles of the geological past. They throw light on the climatic conditions prevalent during their formation. Constraining their age is of importance for deciphering the paleoclimatic history of a region. A suite of K-rich spilitic volcanic rocks immediately overlying the paleosol near Nagaria have been analysed

  15. International Collaboration on Building Local Technical Capacities for Monitoring Volcanic Activity at Pacaya Volcano, Guatemala. (United States)

    Escobar-Wolf, R. P.; Chigna, G.; Morales, H.; Waite, G. P.; Oommen, T.; Lechner, H. N.


    Pacaya volcano is a frequently active and potentially dangerous volcano situated in the Guatemalan volcanic arc. It is also a National Park and a major touristic attraction, constituting an important economic resource for local municipality and the nearby communities. Recent eruptions have caused fatalities and extensive damage to nearby communities, highlighting the need for risk management and loss reduction from the volcanic activity. Volcanic monitoring at Pacaya is done by the Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hidrologia (INSIVUMEH), instrumentally through one short period seismic station, and visually by the Parque Nacional Volcan de Pacaya y Laguna de Calderas (PNVPLC) personnel. We carry out a project to increase the local technical capacities for monitoring volcanic activity at Pacaya. Funding for the project comes from the Society of Exploration Geophysicists through the Geoscientists Without Borders program. Three seismic and continuous GPS stations will be installed at locations within 5 km from the main vent at Pacaya, and one webcam will aid in the visual monitoring tasks. Local educational and outreach components of the project include technical workshops on data monitoring use, and short thesis projects with the San Carlos University in Guatemala. A small permanent exhibit at the PNVPLC museum or visitor center, focusing on the volcano's history, hazards and resources, will also be established as part of the project. The strategy to involve a diverse group of local collaborators in Guatemala aims to increase the chances for long term sustainability of the project, and relies not only on transferring technology but also the "know-how" to make that technology useful. Although not a primary research project, it builds on a relationship of years of joint research projects at Pacaya between the participants, and could be a model of how to increase the broader impacts of such long term collaboration partnerships.

  16. Local stresses, dyke arrest and surface deformation in volcanic edificesand rift zones

    Directory of Open Access Journals (Sweden)

    L. S. Brenner


    Full Text Available Field studies indicate that nearly all eruptions in volcanic edifices and rift zones are supplied with magma through fractures (dykes that are opened by magmatic overpressure. While (inferred dyke injections are frequent during unrest periods, volcanic eruptions are, in comparison, infrequent, suggesting that most dykes become arrested at certain depths in the crust, in agreement with field studies. The frequency of dyke arrest can be partly explained by the numerical models presented here which indicate that volcanic edifices and rift zones consisting of rocks of contrasting mechanical properties, such as soft pyroclastic layers and stiff lava flows, commonly develop local stress fields that encourage dyke arrest. During unrest, surface deformation studies are routinely used to infer the geometries of arrested dykes, and some models (using homogeneous, isotropic half-spaces infer large grabens to be induced by such dykes. Our results, however, show that the dyke-tip tensile stresses are normally much greater than the induced surface stresses, making it difficult to explain how a dyke can induce surface stresses in excess of the tensile (or shear strength while the same strength is not exceeded at the (arrested dyke tip. Also, arrested dyke tips in eroded or active rift zones are normally not associated with dyke-induced grabens or normal faults, and some dykes arrested within a few metres of the surface do not generate faults or grabens. The numerical models show that abrupt changes in Young's moduli(stiffnesses, layers with relatively high dyke-normal compressive stresses (stress barriers, and weak horizontal contacts may make the dyke-induced surface tensile stresses too small for significant fault or graben formation to occur in rift zones or volcanic edifices. Also, these small surface stresses may have no simple relation to the dyke geometry or the depth to its tip. Thus, for a layered crust with weak contacts, straightforward

  17. Post-Laramide and pre-Basin and Range deformation and implications for Paleogene (55-25 Ma) volcanism in central Mexico: A geological basis for a volcano-tectonic stress model (United States)

    Tristán-González, Margarito; Aguirre-Díaz, Gerardo J.; Labarthe-Hernández, Guillermo; Torres-Hernández, José Ramón; Bellon, Hervé


    At central-eastern Mexico, in the Mesa Central province, there are several ranges that were formed after the K/T Laramide compression but before the Basin and Range peak extensional episodes at middle-late Oligocene. Two important volcano-tectonic events happened during this time interval, 1) uplift of crustal blocks exhuming the Triassic-Jurassic metamorphic sequence and formation of basins that were filled with red beds and volcanic sequences, and 2) normal faulting and tilting to the NE of these blocks and fanglomerate filling of graben and half-graben structures. The first event, from late Paleocene to early Eocene, was related to NNE and NNW oriented dextral strike-slip faults. These faults were combined with NW-SE en echelon faulting in these blocks through which plutonism and volcanism occurred. The second event lasted from early Oligocene to early Miocene and coincided with Basin and Range extension. Intense volcanic activity occurred synchronously with the newly-formed or reactivated old fault systems, producing thick sequences of silicic pyroclastic rocks and large domes. Volcano-tectonic peaks occurred in three main episodes during the middle-late Oligocene in this part of Mexico, at about 32-30 Ma, 30-28 Ma, and 26-25 Ma. The objectives of this work is to summarize the volcano-tectonic events that occurred after the end of the Laramide orogeny and before the peak episodes of Basin and Range faulting and Sierra Madre Occidental Oligocene volcanism, and to discuss the influence of these events on the following Oligocene-Miocene volcano-tectonic peak episodes that formed the voluminous silicic volcanism in the Mesa Central, and hence, in the Sierra Madre Occidental. A model based upon geological observations summarizes the volcanic-tectonic evolution of this part of Mexico from the late Paleocene to the Early Miocene.

  18. Tectono-volcanic control of fissure type vents for the 28 Ma Panalillo ignimbrite in the Villa de Reyes Graben, San Luis PotosI, Mexico

    International Nuclear Information System (INIS)

    Tristan-Gonzalez, Margarito; Labarthe-Hernandez, Guillermo; Aguillon-Robles, Alfredo; Aguirre-DIaz, Gerardo J


    The volcano-tectonic events at the Villa de Reyes Graben (VRG), in the southern Sierra Madre Occidental, Mexico, include 1) a regional NNE fault system developed before 32 Ma, 2) this pre-32 Ma faulting controlled the emplacement of 31.5 Ma dacitic domes, 3) NE faulting at 28 Ma that displaced the 31.5 Ma dacitic domes and formed the VRG, as well as the oblique grabens of Bledos and Enramadas oriented NW, 4) emplacement of Panalillo ignimbrite at 28 Ma filling the VRG and erupting from fissures related to the oblique grabens, and eruption of Placa basalt apparently also from fault-controlled vents.

  19. Tectono-volcanic control of fissure type vents for the 28 Ma Panalillo ignimbrite in the Villa de Reyes Graben, San Luis PotosI, Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Tristan-Gonzalez, Margarito; Labarthe-Hernandez, Guillermo; Aguillon-Robles, Alfredo [Instituto de Geologia/DES IngenierIa, UASLP, Av. Dr. Manuel Nava 5, Zona Universitaria, C.P. 78240, San Luis PotosI, S.L.P. (Mexico); Aguirre-DIaz, Gerardo J [Centro de Geociencias, Universidad Nacional Autonoma de Mexico, Campus Juriquilla, Queretaro, 76230 (Mexico)], E-mail:, E-mail:


    The volcano-tectonic events at the Villa de Reyes Graben (VRG), in the southern Sierra Madre Occidental, Mexico, include 1) a regional NNE fault system developed before 32 Ma, 2) this pre-32 Ma faulting controlled the emplacement of 31.5 Ma dacitic domes, 3) NE faulting at 28 Ma that displaced the 31.5 Ma dacitic domes and formed the VRG, as well as the oblique grabens of Bledos and Enramadas oriented NW, 4) emplacement of Panalillo ignimbrite at 28 Ma filling the VRG and erupting from fissures related to the oblique grabens, and eruption of Placa basalt apparently also from fault-controlled vents.

  20. The Ngorongoro Volcanic Highland and its relationships to volcanic deposits at Olduvai Gorge and East African Rift volcanism. (United States)

    Mollel, Godwin F; Swisher, Carl C


    The Ngorongoro Volcanic Highland (NVH), situated adjacent and to the east of Olduvai Gorge in northern Tanzania, is the source of the immense quantities of lava, ignimbrite, air fall ash, and volcaniclastic debris that occur interbedded in the Plio-Pleistocene sedimentary deposits in the Laetoli and Olduvai areas. These volcanics have proven crucial to unraveling stratigraphic correlations, the age of these successions, the archaeological and paleontological remains, as well as the source materials from which the bulk of the stone tools were manufactured. The NVH towers some 2,000 m above the Olduvai and Laetoli landscapes, affecting local climate, run-off, and providing varying elevation - climate controlled ecosystem, habitats, and riparian corridors extending into the Olduvai and Laetoli lowlands. The NVH also plays a crucial role in addressing the genesis and history of East African Rift (EAR) magmatism in northern Tanzania. In this contribution, we provide age and petrochemical compositions of the major NVH centers: Lemagurut, basalt to benmorite, 2.4-2.2 Ma; Satiman, tephrite to phonolite, 4.6-3.5 Ma; Oldeani, basalt to trachyandesite, 1.6-1.5 Ma; Ngorongoro, basalt to rhyolite, 2.3-2.0 Ma; Olmoti, basalt to trachyte, 2.0-1.8 Ma; Embagai, nephelinite to phonolite, 1.2-0.6 Ma; and Engelosin, phonolite, 3-2.7 Ma. We then discuss how these correlate in time and composition with volcanics preserved at Olduvai Gorge. Finally, we place this into context with our current understanding as to the eruptive history of the NVH and relationship to East African Rift volcanism. Copyright © 2011 Elsevier Ltd. All rights reserved.

  1. New Particle Formation (NPF) within the volcanic plume of Piton de la Fournaise at Maïdo observatory (21.1° S 55.4° E), on La Réunion Island. (United States)

    Foucart, Brice; Sellegri, Karine; Tulet, Pierre


    Volcanic emissions can have a significant effect on the environment, and may impact climate through the injection of gases and aerosols in the upper troposphere where they have a long residence time and an impact on clouds formation [Makkonen et al., 2012]. The Piton de La Fournaise volcano on La Réunion Island erupted four times in 2015 [Peltier et al., 2016] and volcanic particles were ejected in the atmosphere both as primary particles rapidly deposited due to their large size and secondary particles mainly derived from oxidation of sulphur dioxide. In this study, we focus on this secondary process of forming new aerosol particles (NPF). Sulphuric acid (H2SO4), resulting from SO2 oxidation in the presence of light, is known to be the major precursor to nucleation events [kulmala et al., 2004 and Kerminen et al., 2010]. During the April 2007 eruption of Piton de la Fournaise, Tulet and Villeneuve [2010] estimated by OMI and CALIOP space sensors analysis a total SO2 release of 230 kt, among of which 60 kt that have been transformed into H2SO4 supposing NPF processes. However, the nucleation phenomenon has rarely been directly observed in volcanic environments [Kulmala et al., 2004] except for Mauna Loa volcano on Hawaii [Weber et al., 1995] and for Eyjafjallajokull plume caught at the Puy de Dôme station [Boulon et al., 2011]. Within the STRAP project (Synergie Trans-disciplinaire pour Répondre aux Aléas de Panache Volcanique), a multidisciplinary tracking of a volcanic gas and aerosol plume that has been conducted by Tulet et al. [2016] through a strong collaboration between volcanologists and meteorologists. Part of the measurements were performed at Maïdo observatory (21.1° S 55.4° E) which is located at 40 km from the volcano but which has been reached several times by the volcanic plume, each time accompanied by a NPF event. A statistical analysis of the influence of the plume presence on the NPF frequency, intensity and new particles growth rates is

  2. SDSS IV MaNGA: the global and local stellar mass assemby histories of galaxies (United States)

    Ibarra-Medel, Héctor J.; Sánchez, Sebastián F.; Avila-Reese, Vladimir; Hernández-Toledo, Héctor M.; González, J. Jesús; Drory, Niv; Bundy, Kevin; Bizyaev, Dmitry; Cano-Díaz, Mariana; Malanushenko, Elena; Pan, Kaike; Roman-Lopes, Alexandre; Thomas, Daniel


    Using the fossil record method implemented through Pipe3D, we reconstruct the global and radial stellar mass growth histories (MGHs) of a large sample of galaxies, ranging from dwarf to giant objects, from the Mapping Nearby Galaxies at the Apache Point Observatory (MaNGA) survey. We confirm that the main driver of the global MGHs is mass, with more massive galaxies assembling earlier (downsizing), though for a given mass, the global MGHs segregate by colour, specific star formation rate and morphological type. From the inferred radial mean MGHs, we find that at fractions of assembled mass larger than ˜80 per cent, the innermost regions formed stars, on average, in the inside-out mode. At earlier epochs, when the age estimation of the method becomes poor, the MGHs seem to be spatially homogeneous or even in the outside-in mode, especially for the red/quiescent/early-type galaxies. The innermost MGHs are, in general, less scattered around the mean than the outermost MGHs. For dwarf and low-mass galaxies, we do not find evidence of an outside-in formation mode; instead, their radial MGHs are very diverse most of the time, with periods of outside-in and inside-out modes (or strong radial migration), suggesting this is an episodic star formation history. Blue/star-forming/late-type galaxies present, on average, a significantly more pronounced inside-out formation mode than red/quiescent/early-type galaxies, independently of mass. We discuss our results in the light of the processes of galaxy formation, quenching and radial migration. We also discuss the uncertainties and biases of the fossil record method and how these could affect our results.

  3. Do galaxy global relationships emerge from local ones? The SDSS IV MaNGA surface mass density-metallicity relation (United States)

    Barrera-Ballesteros, Jorge K.; Heckman, Timothy M.; Zhu, Guangtun B.; Zakamska, Nadia L.; Sánchez, Sebastian F.; Law, David; Wake, David; Green, Jenny E.; Bizyaev, Dmitry; Oravetz, Daniel; Simmons, Audrey; Malanushenko, Elena; Pan, Kaike; Roman Lopes, Alexandre; Lane, Richard R.


    We present the stellar surface mass density versus gas metallicity (Σ*-Z) relation for more than 500 000 spatially resolved star-forming resolution elements (spaxels) from a sample of 653 disc galaxies included in the SDSS IV MaNGA survey. We find a tight relation between these local properties, with higher metallicities as the surface density increases. This relation extends over three orders of magnitude in the surface mass density and a factor of 4 in metallicity. We show that this local relationship can simultaneously reproduce two well-known properties of disc galaxies: their global mass-metallicity relationship and their radial metallicity gradients. We also find that the Σ*-Z relation is largely independent of the galaxy's total stellar mass and specific star formation rate (sSFR), except at low stellar mass and high sSFR. These results suggest that in the present-day universe local properties play a key role in determining the gas-phase metallicity in typical disc galaxies.

  4. Magnetostratigraphy and 39Ar/40Ar studies of the Lana'i Long Volcanic Sequence (ca. 1.606+/-0.063 Ma), Hawaii, USA (United States)

    Herrero-Bervera, E.; Jicha, B.; Valet, J.


    Previous published work on Lanai indicated that the volcano was formed mainly during the Matuyama Chron (Herrero-Bervera et al., 2000). In order to constrain further the timing of the active phases of the Lanai volcano, we conducted a paleomagnetic and rock magnetic study involving a ~500-m vertical thick sequence of lava flows that were erupted between 0.76+/-0.66 Ma and 1.6+/-0.09 Ma according to previous K/Ar and 40Ar/39Ar dating (Leonhardt et al., 2009). Low-field susceptibility versus temperature (k-T) and SIRM experiments performed on a dozen flows indicate that magnetite dominates the remanent magnetization (575°C). In a few cases, a low-temperature mineral phase (300-400°C) could reflect the presence of titanomagnetite with low Ti content, but the presence of maghemite or pyrrhotite cannot be completely excluded. Additional investigations are in progress on this matter. All specimens were step-wise demagnetized by alternating fields from 5 to 100 mT. Companion specimens from the same samples were demagnetized at 15 temperature steps. The demagnetization diagrams obtained with each technique showed a stable direction of remanence. In all cases, the characteristic (ChRM) component was clearly defined from at least seven successive directions isolated during step-wise demagnetization. The succession of the mean directions calculated for each lava flow reveals the existence of at least one polarity interval. Based on radiometric dates, they were assigned to the Gilsa, "excursion" (1.606+/-0.063 Ma). Thus, the present results, along with the radiometric ages of the lavas, indicate that the tholeiitic flows that formed the Lanai volcano were erupted over a short time period, and only during the Matuyama Chron (0.780-2.58 Ma). No eruptions have occurred during the Brunhes Chron (0.78 Ma) as previously indicated from K-Ar data on lavas in the Maunalei Gulch. The excursional VGPs from the onset of the Gilsa excursion recorded on Lanai are situated near the

  5. Mapping local singularities using magnetic data to investigate the volcanic rocks of the Qikou depression, Dagang oilfield, eastern China

    Directory of Open Access Journals (Sweden)

    G. Chen


    Full Text Available The spatial structural characteristics of geological anomaly, including singularity and self-similarity, can be analysed using fractal or multifractal modelling. Here we apply the multifractal methods to potential fields to demonstrate that singularities can characterise geological bodies, including rock density and magnetic susceptibility. In addition to enhancing weak gravity and magnetic anomalies with respect to either strong or weak background levels, the local singularity index (α ≈ 2 can be used to delineate the edges of geological bodies. Two models were established to evaluate the effectiveness of mapping singularities for extracting weak anomalies and delineating edges of buried geological bodies. The Qikou depression of the Dagang oilfield in eastern China has been chosen as a study area for demonstrating the extraction of weak anomalies of volcanic rocks, using the singularity mapping technique to analyse complex magnetic anomalies caused by complex geological background. The results have shown that the singularities of magnetic data mapped in the paper are associated with buried volcanic rocks, which have been verified by both drilling and seismic survey, and the S–N and E–W faults in the region. The targets delineated for deeply seated faults and volcanic rocks in the Qikou depression should be further investigated for the potential application in undiscovered oil and gas reservoirs exploration.

  6. SDSS IV MaNGA - metallicity and nitrogen abundance gradients in local galaxies (United States)

    Belfiore, Francesco; Maiolino, Roberto; Tremonti, Christy; Sánchez, Sebastian F.; Bundy, Kevin; Bershady, Matthew; Westfall, Kyle; Lin, Lihwai; Drory, Niv; Boquien, Médéric; Thomas, Daniel; Brinkmann, Jonathan


    We study the gas phase metallicity (O/H) and nitrogen abundance gradients traced by star-forming regions in a representative sample of 550 nearby galaxies in the stellar mass range 109-1011.5 M⊙ with resolved spectroscopic data from the Sloan Digital Sky Survey IV Mapping Nearby Galaxies at Apache Point Observatory survey. Using strong-line ratio diagnostics (R23 and O3N2 for metallicity and N2O2 for N/O) and referencing to the effective (half-light) radius (Re), we find that the metallicity gradient steepens with stellar mass, lying roughly flat among galaxies with log (M⋆/M⊙) = 9.0 but exhibiting slopes as steep as -0.14 dex R_e^{-1} at log (M⋆/M⊙) = 10.5 (using R23, but equivalent results are obtained using O3N2). At higher masses, these slopes remain typical in the outer regions of our sample (R > 1.5Re), but a flattening is observed in the central regions (R 2.0Re), we detect a mild flattening of the metallicity gradient in stacked profiles, although with low significance. The N/O ratio gradient provides complementary constraints on the average chemical enrichment history. Unlike the oxygen abundance, the average N/O profiles do not flatten out in the central regions of massive galaxies. The metallicity and N/O profiles both depart significantly from an exponential form, suggesting a disconnect between chemical enrichment and stellar mass surface density on local scales. In the context of inside-out growth of discs, our findings suggest that central regions of massive galaxies today have evolved to an equilibrium metallicity, while the nitrogen abundance continues to increase as a consequence of delayed secondary nucleosynthetic production.

  7. Petrographic and geochemical data for Cenozoic volcanic rocks of the Bodie Hills, California and Nevada (United States)

    du Bray, Edward A.; John, David A.; Box, Stephen E.; Vikre, Peter G.; Fleck, Robert J.; Cousens, Brian L.


    Petrographic and geochemical data for Cenozoic volcanic rocks of the Bodie Hills, California and Nevada // // This report presents petrographic and geochemical data for samples collected during investigations of Tertiary volcanism in the Bodie Hills of California and Nevada. Igneous rocks in the area are principally 15–6 Ma subduction-related volcanic rocks of the Bodie Hills volcanic field but also include 3.9–0.1 Ma rocks of the bimodal, post-subduction Aurora volcanic field. Limited petrographic results for local basement rocks, including Mesozoic granitoid rocks and their metamorphic host rocks, are also included in the compilation. The petrographic data include visual estimates of phenocryst abundances as well as other diagnostic petrographic criteria. The geochemical data include whole-rock major oxide and trace element data, as well as limited whole-rock isotopic data.

  8. Localization of Volcanic Activity: Topographic Effects on Dike Propagation, Eruption and COnduit Formation

    Energy Technology Data Exchange (ETDEWEB)

    E.S. Gaffney; B. Damjanac


    Magma flow in a dike rising in a crack whose strike runs from a highland or a ridge to an adjacent lowland has been modeled to determine the effect of topography on the flow. It is found that there is a distinct tendency for the flow to be diverted away from the highland end of the strike toward the lowland. Separation of the geometric effect of the topography from its effect on lateral confining stresses on the crack indicates that both contribute to the effect but that the effect of stress is less important. Although this analysis explains a tendency for volcanic eruptions to occur in low lands, it does not preclude eruptions on highlands. The particular configuration modeled mimics topography around the proposed nuclear waste repository at Yucca Mountain, Nevada, so that the results may indicate some reduction in the volcanic hazard to the site.

  9. Localization of Volcanic Activity: Topographic Effects on Dike Propagation, Eruption and Conduit Formation

    International Nuclear Information System (INIS)

    E.S. Gaffney; B. Damjanac


    Magma flow in a dike rising in a crack whose strike runs from a highland or a ridge to an adjacent lowland has been modeled to determine the effect of topography on the flow. It is found that there is a distinct tendency for the flow to be diverted away from the highland end of the strike toward the lowland. Separation of the geometric effect of the topography from its effect on lateral confining stresses on the crack indicates that both contribute to the effect but that the effect of stress is less important. Although this analysis explains a tendency for volcanic eruptions to occur in low lands, it does not preclude eruptions on highlands. The particular configuration modeled mimics topography around the proposed nuclear waste repository at Yucca Mountain, Nevada, so that the results may indicate some reduction in the volcanic hazard to the site

  10. Paraná flood basalt volcanism primarily limited to 1 Myr beginning at 135 Ma: New 40Ar/39Ar ages for rocks from Rio Grande do Sul, and critical evaluation of published radiometric data (United States)

    Baksi, Ajoy K.


    40Ar/39Ar step heating analyses were carried out on seven rocks (five basalts, an andesite and a rhyolite) from the southern Paraná Province ( 28°S-30°S); they yield plateau/isochron ages of 135-134 Ma, in good agreement with published step heating data on rocks from the same area. Critical review of laser spot isochron ages for rocks from the Province, ranging from 140 to 130 Ma, are shown to be unreliable estimates of crystallization ages, as the rocks were substantially altered; step heating results on three of these rocks thought to yield good plateau ages, are shown to be incorrect, as a result of a technicality in dating procedures followed. U-Pb ages on zircon and baddeleyite separated from a variety of rock types ( 30°S-23°S) fall in the range 135 to 134 Ma. All reliable 40Ar/39Ar and U-Pb ages indicate volcanism was sharply focused, initiated at 135 Ma, and 1 Myr in duration; no variation of age with either latitude or longitude is noted, Scrutiny of published 40Ar/39Ar ages on the Florianopolis dykes shows they cannot be used as reliable crystallization ages. U-Pb work shows that this dyke swarm was formed coevally with the main part of the Parana province. Most of the published 40Ar/39Ar ages on the Ponta Grossa dyke swarm are unreliable; a few ages appear reliable and suggest the magmatic event in this area, may have postdated the main Paraná pulse by 1-2 Myr. A single 40Ar/39Ar age from a high-Nb basalt in the southernmost part ( 34°S) of the Paraná at 135 Ma, highlights the need for further radiometric work on other areas of this flood basalt province. The Paraná Province postdates the time of the Jurassic-Cretaceous bound­ary by 10 Myr.

  11. K-Ar age data and geochemistry of the Kiwitahi Volcanics, western Hauraki Rift, North Island, New Zealand

    Energy Technology Data Exchange (ETDEWEB)

    Black, P M [Department of Geology, Auckland University, Auckland (New Zealand); Briggs, R M [Department of Earth Sciences, Waikato University, Hamilton (New Zealand); Itaya, T [Hiruzen Research Institute, Okayama University of Science, Okayama (Japan); Dewes, E R [Department of Earth Sciences, Waikato University, Hamilton (New Zealand); Dunbar, H M [Department of Earth Sciences, Waikato University, Hamilton (New Zealand); Kawasaki, K [Hiruzen Research Institute, Okayama University of Science, Okayama (Japan); Kuschel, E [Department of Geology, Auckland University, Auckland (New Zealand); Smith, I E.M. [Department of Geology, Auckland University, Auckland (New Zealand)


    The Kiwitahi Volcanics of late Miocene age crop out in a number of localities situated along the western side of the Hauraki Rift in northern North Island, New Zealand. They extend from Waiheke Island in the north to Te Tapui in the south. From 19 new K-Ar ages presented here and geochemical data from volcanics at each locality, it is suggested that the Kiwitahi Volcanics should be informally subdivided into five groups: (1) an oldest group of agglomerates and volcanic breccias at northeastern Waiheke, containing pyroxene and hornblende andesites with an age range of 14.4-16.02 Ma; (2) a volcanic centre at Stony Batter (6.85-8.34 Ma) comprised of olivine basaltic andesites which should be assigned to the geochemically and temporally similar Ti Point Volcanics; (3) a group including the andesitic breccias at Ness Valley and the volcanic centres of Miranda (pyroxene basaltic andesite, pyroxene and hornblende andesite, hornblende dacite) and Pukekamaka (hornblende andesites), all within the age range 10.22-12.96 Ma; (4) a separate group at Tahuna (6.36-6.80 Ma) consisting of pyroxene basaltic andesites and pyroxene andesites; and (5) a southern group of Maungatapu, Ruru, Maungakawa, and Te Tapui (5.52-6.23 Ma), forming eroded cones of olivine basaltic andesites, pyroxene basaltic andesites, and pyroxene andesites. The Kiwitahi Volcanics of late Miocene age crop out in a number of localities situated along the western side of the Hauraki Rift in northern North Island, New Zealand. They extend from Waiheke Island in the north to Te Tapui in the south. From 19 new K-Ar ages presented here and geochemical data from volcanics at each locality, it is suggested that the Kiwitahi Volcanics should be informally subdivided into five groups: (1) an oldest group of agglomerates and volcanic breccias at northeastern Waiheke, containing pyroxene and hornblende andesites with an age range of 14.4-16.02 Ma; (2) a volcanic centre at Stony Batter (6.85-8.34 Ma) comprised of olivine

  12. K-Ar age data and geochemistry of the Kiwitahi Volcanics, western Hauraki Rift, North Island, New Zealand

    International Nuclear Information System (INIS)

    Black, P.M.; Briggs, R.M.; Itaya, T.; Dewes, E.R.; Dunbar, H.M.; Kawasaki, K.; Kuschel, E.; Smith, I.E.M.


    The Kiwitahi Volcanics of late Miocene age crop out in a number of localities situated along the western side of the Hauraki Rift in northern North Island, New Zealand. They extend from Waiheke Island in the north to Te Tapui in the south. From 19 new K-Ar ages presented here and geochemical data from volcanics at each locality, it is suggested that the Kiwitahi Volcanics should be informally subdivided into five groups: (1) an oldest group of agglomerates and volcanic breccias at northeastern Waiheke, containing pyroxene and hornblende andesites with an age range of 14.4-16.02 Ma; (2) a volcanic centre at Stony Batter (6.85-8.34 Ma) comprised of olivine basaltic andesites which should be assigned to the geochemically and temporally similar Ti Point Volcanics; (3) a group including the andesitic breccias at Ness Valley and the volcanic centres of Miranda (pyroxene basaltic andesite, pyroxene and hornblende andesite, hornblende dacite) and Pukekamaka (hornblende andesites), all within the age range 10.22-12.96 Ma; (4) a separate group at Tahuna (6.36-6.80 Ma) consisting of pyroxene basaltic andesites and pyroxene andesites; and (5) a southern group of Maungatapu, Ruru, Maungakawa, and Te Tapui (5.52-6.23 Ma), forming eroded cones of olivine basaltic andesites, pyroxene basaltic andesites, and pyroxene andesites. The Kiwitahi Volcanics of late Miocene age crop out in a number of localities situated along the western side of the Hauraki Rift in northern North Island, New Zealand. They extend from Waiheke Island in the north to Te Tapui in the south. From 19 new K-Ar ages presented here and geochemical data from volcanics at each locality, it is suggested that the Kiwitahi Volcanics should be informally subdivided into five groups: (1) an oldest group of agglomerates and volcanic breccias at northeastern Waiheke, containing pyroxene and hornblende andesites with an age range of 14.4-16.02 Ma; (2) a volcanic centre at Stony Batter (6.85-8.34 Ma) comprised of olivine

  13. Zhigang Ma

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science. Zhigang Ma. Articles written in Bulletin of Materials Science. Volume 35 Issue 4 August 2012 pp 575-578. Degradation and miscibility of poly(DL-lactic acid)/poly(glycolic acid) composite films: Effect of poly(DL-lactic-co-glycolic acid) · Zhigang Ma Na Zhao Chengdong Xiong.

  14. Localized rejuvenation of a crystal mush recorded in zircon temporal and compositional variation at the Lassen Volcanic Center, northern California.

    Directory of Open Access Journals (Sweden)

    Erik W Klemetti

    Full Text Available Zircon ages and trace element compositions from recent silicic eruptions in the Lassen Volcanic Center (LVC allow for an evaluation of the timing and conditions of rejuvenation (reheating and mobilization of crystals within the LVC magmatic system. The LVC is the southernmost active Cascade volcano and, prior to the 1980 eruption of Mount St. Helens, was the site of the only eruption in the Cascade arc during the last century. The three most recent silicic eruptions from the LVC were very small to moderate-sized lava flows and domes of dacite (1915 and 27 ka eruptions of Lassen Peak and rhyodacite (1.1 ka eruption of Chaos Crags. These eruptions produced mixed and mingled lavas that contain a diverse crystal cargo, including zircon. 238U-230Th model ages from interior and surface analyses of zircon reveal ages from ∼17 ka to secular equilibrium (>350 ka, with most zircon crystallizing during a period between ∼60-200 ka. These data support a model for localized rejuvenation of crystal mush beneath the LVC. This crystal mush evidently is the remnant of magmatism that ended ∼190 ka. Most zircon are thought to have been captured from "cold storage" in the crystal mush (670-725°C, Hf >10,000 ppm, Eu/Eu* 0.25-0.4 locally remobilized by intrusion of mafic magma. A smaller population of zircon (>730°C, Hf 0.4 grew in, and are captured from, rejuvenation zones. These data suggest the dominant method to produce eruptible melt within the LVC is small-scale, local rejuvenation of the crystal mush accompanied by magma mixing and mingling. Based on zircon stability, the time required to heat, erupt and then cool to background conditions is relatively short, lasting a maximum of 10 s-1000 s years. Rejuvenation events in the LVC are ephemeral and permit eruption within an otherwise waning and cooling magmatic body.

  15. SDSS-IV MaNGA: What Shapes the Distribution of Metals in Galaxies? Exploring the Roles of the Local Gas Fraction and Escape Velocity (United States)

    Barrera-Ballesteros, J. K.; Heckman, T.; Sánchez, S. F.; Zakamska, N. L.; Cleary, J.; Zhu, G.; Brinkmann, J.; Drory, N.; THE MaNGA TEAM


    We determine the local metallicity of the ionized gas for more than 9.2 × 105 star-forming regions (spaxels) located in 1023 nearby galaxies included in the Sloan Digital Sky Survey-IV MaNGA integral field spectroscopy unit survey. We use the dust extinction derived from the Balmer decrement and the stellar template fitting in each spaxel to estimate the local gas and stellar mass densities, respectively. We also use the measured rotation curves to determine the local escape velocity (V esc). We then analyze the relationships between the local metallicity and both the local gas fraction (μ) and V esc. We find that metallicity decreases with both increasing μ and decreasing V esc. By examining the residuals in these relations we show that the gas fraction plays a more primary role in the local chemical enrichment than does V esc. We show that the gas-regulator model of chemical evolution provides a reasonable explanation of the metallicity on local scales. The best-fit parameters for this model are consistent with the metal loss caused by momentum-driven galactic outflows. We also argue that both the gas fraction and the local escape velocity are connected to the local stellar surface density, which in turn is a tracer of the epoch at which the dominant local stellar population formed.

  16. Geophysical expression of caldera related volcanism, structures and mineralization in the McDermitt volcanic field (United States)

    Rytuba, J. J.; Blakely, R. J.; Moring, B.; Miller, R.


    The High Rock, Lake Owyhee, and McDermitt volcanic fields, consisting of regionally extensive ash flow tuffs and associated calderas, developed in NW Nevada and SE Oregon following eruption of the ca. 16.7 Ma Steens flood basalt. The first ash flow, the Tuff of Oregon Canyon, erupted from the McDermitt volcanic field at 16.5Ma. It is chemically zoned from peralkaline rhyolite to dacite with trace element ratios that distinguish it from other ash flow tuffs. The source caldera, based on tuff distribution, thickness, and size of lithic fragments, is in the area in which the McDermitt caldera (16.3 Ma) subsequently formed. Gravity and magnetic anomalies are associated with some but not all of the calderas. The White Horse caldera (15.6 Ma), the youngest caldera in the McDermitt volcanic field has the best geophysical expression, with both aeromagnetic and gravity lows coinciding with the caldera. Detailed aeromagnetic and gravity surveys of the McDermitt caldera, combined with geology and radiometric surveys, provides insight into the complexities of caldera collapse, resurgence, post collapse volcanism, and hydrothermal mineralization. The McDermitt caldera is among the most mineralized calderas in the world, whereas other calderas in these three Mid Miocene volcanic fields do not contain important hydrothermal ore deposits, despite having similar age and chemistry. The McDermitt caldera is host to Hg, U, and Li deposits and potentially significant resources of Ga, Sb, and REE. The geophysical data indicate that post-caldera collapse intrusions were important in formation of the hydrothermal systems. An aeromagnetic low along the E caldera margin reflects an intrusion at a depth of 2 km associated with the near-surface McDermitt-hot-spring-type Hg-Sb deposit, and the deeper level, high-sulfidation Ga-REE occurrence. The Li deposits on the W side of the caldera are associated with a series of low amplitude, small diameter aeromagnetic anomalies that form a continuous

  17. New Paleomagnetic Data from Upper Permian and Lower Triassic Volcanic Sequences from Hua Binh, Quynh Nhai, and Thuan Chau Localities, Northwest Veitnam and Their Bearing on the Accretion History of Southeast Asia (United States)

    Geissman, J. W.; Chi, C. T.


    New paleomagnetic data from Upper Permian to Lower Triassic volcanic rocks sampled in NW Vietnam provide more quantitative constraints on the paleogeographic setting of crustal elements that comprise the Song Da Terrane, east of the Song Ma suture, between the South China block (SCB) and north Indochina. These include results from 12 sites (125 samples) from basalts of the Vien Nam Formation, exposed at Hoa Binh Dam; eight sites (74 samples) from basalts of the Cam Thuy Formation near Thuan Chau; and 19 sites (198 samples) from andesites and basalts of the Vien Nam Formation near Quynh Nhai. The collection is limited by the quality of exposures and quantity of independent flows. Most sites yield interpretable magnetizations in progressive demagnetization, and the response implies that characteristic remanent magnetization (ChRM) components are carried by low-titanium magnetite or hematite, or a combination of both; these are isolated from secondary components. Rock magnetic data and petrography support the retention of an early-acquired thermoremanent magnetization in most sites. The Vien Nam Formation mafic volcanic rocks yield a grand mean, in geographic coordinates, of D=33.8o, I=-28.4o ( a95 = 9.5o, k =30.3, N=9 accepted sites), and a pole position at Lat=41.1N, Long=239.8E and a paleolatitude at ~15o S during the Late Permian to Early Triassic. Permian basalts of the Cam Thuy Formation provide a grand mean, corrected for structural tilt, of D=216.1o, I=+10.5o, a95=8.9o, k=107.8, and N= 4, with a pole position at Lat=45.6N, Long=226.8E. Volcanic rocks at the Quynh Nhai locality likely yield the most robust paleofield determination, as the data set is of dual polarity and passes a reversal test. The tilt corrected grand mean (normal polarity) is D=48.3o, I=-10.0o, a95=8.0o, k=27.7, N = 13, and this in turn yields an inferred paleomagnetic pole at Lat=35.7N, Long=217.4E, and a paleolatitude of 5.1oS for the late Permian. Compared with the Late Permian

  18. Adole, MA

    African Journals Online (AJOL)

    Adole, MA. Vol 4, No 1 (2011) - Articles Effects of Groundnut Husk Ash-blended Cement on Chemical Resistance of Concrete Abstract PDF. ISSN: 1596-6035. AJOL African Journals Online. HOW TO USE AJOL... for Researchers · for Librarians · for Authors · FAQ's · More about AJOL · AJOL's Partners · Terms and ...

  19. Oral delivery of [D-Leu-4]-OB3 and MA-[D-Leu-4]-OB3, synthetic peptide leptin mimetics: Immunofluorescent localization in the mouse hypothalamus. (United States)

    Anderson, Brian M; Jacobson, Lauren; Novakovic, Zachary M; Grasso, Patricia


    This study describes the localization of [D-Leu-4]-OB3 and MA-[D-Leu-4]-OB3, synthetic peptide leptin mimetics, in the hypothalamus of Swiss Webster and C57BL/6J wild-type mice, leptin-deficient ob/ob mice, and leptin-resistant diet-induced obese (DIO) mice. The mice were given [D-Leu-4]-OB3 or MA-[D-Leu-4]-OB3 in 0.3% dodecyl maltoside by oral gavage. Once peak serum concentrations were reached, the mice received a lethal dose of pentobarbital and were subjected to intracardiac perfusion fixation. The brains were excised, post-fixed in paraformaldehyde, and cryo-protected in sucrose. Free-floating frozen coronal sections were cut at 25-µm and processed for imaging by immunofluorescence microscopy. In all four strains of mice, dense staining was concentrated in the area of the median eminence, at the base and/or along the inner wall of the third ventricle, and in the brain parenchyma at the level of the arcuate nucleus. These results indicate that [D-Leu-4]-OB3 and MA-[D-Leu-4]-OB3 cross the blood-brain barrier and concentrate in an area of the hypothalamus known to regulate energy balance and glucose homeostasis. Most noteworthy is the localization of [D-Leu-4]-OB3 immunoreactivity within the hypothalamus of DIO mice via a conduit that is closed to leptin in this rodent model, and in most cases of human obesity. Together with our previous studies describing the effects of [D-Leu-4]-OB3 and MA-[D-Leu-4]-OB3 on energy balance, glucose regulation, and signal transduction pathway activation, these findings are consistent with a central mechanism of action for these synthetic peptide leptin mimetics, and suggest their potential usefulness in the management of leptin-resistant obesity and type 2 diabetes in humans. Copyright © 2017 Elsevier B.V. All rights reserved.

  20. Timing of the volcanism of the southern Kivu province: Implications for the evolution of the western branch of the East African rift system

    International Nuclear Information System (INIS)

    Pasteels, P.


    New K-Ar datings of a large rock sampling from the South Kivu volcanic province (Zaire, Rwanda, Burundi) are reported. No ages older than 10 Ma have been obtained. This result contrasts with older assumptions and puts severe constraints on the relations between volcanism and rift evolution. From 10 to 7.5 Ma tholeiitic volcanism predominates corresponding to an episode of fissural eruptions; from 7.5 to 5 Ma alkali basalts and their differentiates are mainly erupted in localized rifts. A culmination of activity occurs between 6.0 and 5.5 Ma ago. Pleistocene alkalic volcanism is restricted to localized areas. The transition from tholeiites to alkali-basaltic volcanism dated around 7.5 Ma would correspond to a major rifting phase which corresponds with the initiation of Lake Kivu Basin formation. The distribution of tholeiitic rocks in the central part of the rift, and predominantly alkalic rocks along the western active border fault, strengthens the idea that the former are associated with tension, the latter with vertical, possibly also strike-slip movements. Volcanism in the Western Rift is restricted to areas where tension occurs in a zone which is located between two zones of strike-slip. In the South Kivu area normal faults intersect strike-slip faults and this seems to have determined the location of volcanic activity. Magma formation is considered to be related with shear heating combined with adiabatic decompression in ascending diapirs. This implies heating at the lithosphere-asthenosphere boundary as a result of extension. Generation of tholeiitic or alkalic magmas is connected with the variable ascent velocity of mantle diapirs or with variable shear heating along the shear zone. Changes in both magma composition and intensity of volcanic activity with time are considered to be related to major phases of rift evolution. (orig.)

  1. Geologic Map of the Bodie Hills Volcanic Field, California and Nevada: Anatomy of Miocene Cascade Arc Magmatism in the Western Great Basin (United States)

    John, D. A.; du Bray, E. A.; Blakely, R. J.; Box, S.; Fleck, R. J.; Vikre, P. G.; Rytuba, J. J.; Moring, B. C.


    The Bodie Hills Volcanic Field (BHVF) is a >700 km2, long-lived (~9 Ma) but episodic, Miocene eruptive center in the southern part of the ancestral Cascade magmatic arc. A 1:50,000-scale geologic map based on extensive new mapping, combined with 40Ar/39Ar dates, geochemical data, and detailed gravity and aeromagnetic surveys, defines late Miocene magmatic and hydrothermal evolution of the BHVF and contrasts the subduction-related BHVF with the overlying, post-subduction, bimodal Plio-Pleistocene Aurora Volcanic Field (AVF). Important features of the BHVF include: Eruptions occurred during 3 major eruptive stages: dominantly trachyandesite stratovolcanoes (~14.7 to 12.9 Ma), mixed silicic trachyandesite, dacite, and rhyolite (~11.3 to 9.6 Ma), and dominantly silicic trachyandesite to dacite domes (~9.2 to 8.0 Ma). Small rhyolite domes were emplaced at ~6 Ma. Trachyandesitic stratovolcanoes with extensive debris flow aprons form the outer part of BHVF, whereas silicic trachyandesite to rhyolite domes are more centrally located. Geophysical data suggest that many BHVF volcanoes have shallow plutonic roots that extend to depths ≥1-2 km below the surface, and much of the Bodie Hills may be underlain by low density plutons presumably related to BHVF volcanism. BHVF rocks contain ~50 to 78% SiO2 (though few rocks have Bodie Hills at ~10 Ma, but the composition and eruptive style of volcanism continued unchanged for 2 Ma. However, kinematic data for veins and faults in mining districts suggest a change in the stress field from transtensional to extensional approximately coincident with cessation of subduction. The Bodie Hills are flanked to the east, north, and west by sedimentary basins that began to form in the late Miocene (locally >11 Ma). Fine to coarse sedimentary deposits within the BHVF include stream deposits in channels that cut across the hills and were partly filled by ~9.4 Ma Eureka Valley Tuff erupted 20 km to the northwest. Shallow dips and preservation of

  2. Origin of seamount volcanism in northeast Indian Ocean with emphasis on Christmas Island (United States)

    Taneja, R.; O'Neill, C.; Rushmer, T. A.; Jourdan, F.; Blichert-Toft, J.; Turner, S.; Lackie, M. A.


    The Northeast Indian Ocean has been a central point of research in the recent past due to its intraplate geophysical and geochemical characteristics. It is dominated by sub-aerial volcanic islands and submerged guyots and two islands, namely, Cocos (Keeling) Island and Christmas Island. Christmas Island, the focus of this study, consists of limestone and mafic intraplate volcanics. The origin of most of the features in northeast Indian Ocean is not fully understood. Christmas Island has experienced multiple stages of intraplate volcanic activity as previously established by 40Ar/39Ar radioisotopic analyses of basalts from the island (Hoernl et al., 2011). Here, we present new 40Ar/39Ar ages where the rock samples from Waterfall Spring (WS), Ethel Beach (EB) & Dolly Beach (DB) on the east coast of the island yielded plateau and mini-plateau ages of 37.75±0.77 Ma, 37.10±0.66 Ma and 43.37±0.45 Ma respectively, whereas a sample from Flying Fish Cove (FFC) in the north of the island yielded a minimum age of 38.6±0.5 Ma. All these units are part of the Lower Volcanics Series. The samples from the west coast (Winifred Beach, WB) are younger with an age of 4.32 ± 0.17 Ma, and are part of the Upper Volcanic Series. This confirms two stages of volcanism at the island with a gap of around 38 Ma. The 40Ar/39Ar radioisotopic ages were overlayed on Gplates and seismic tomography models to determine its paleo motion. The present position of the island is 10.5°S, 105.5°E. During Eocene its reconstructed position was 30°S latitude. Seismic tomography models have highlighted a low velocity zone beneath the island during Eocene. Geochemically, the two volcanic suites (Upper & Lower) are mostly similar in their major and trace element composition. The majority of localities (WS, EB, and WB) are basanites; where as that from Dolly Beach is basaltic. The Dale's (west coast), are trachyte and appear evolved with high SiO2. They also have low Ba and Sr ~25ppm, whereas those from

  3. Volcanic hazards to airports (United States)

    Guffanti, M.; Mayberry, G.C.; Casadevall, T.J.; Wunderman, R.


    Volcanic activity has caused significant hazards to numerous airports worldwide, with local to far-ranging effects on travelers and commerce. Analysis of a new compilation of incidents of airports impacted by volcanic activity from 1944 through 2006 reveals that, at a minimum, 101 airports in 28 countries were affected on 171 occasions by eruptions at 46 volcanoes. Since 1980, five airports per year on average have been affected by volcanic activity, which indicates that volcanic hazards to airports are not rare on a worldwide basis. The main hazard to airports is ashfall, with accumulations of only a few millimeters sufficient to force temporary closures of some airports. A substantial portion of incidents has been caused by ash in airspace in the vicinity of airports, without accumulation of ash on the ground. On a few occasions, airports have been impacted by hazards other than ash (pyroclastic flow, lava flow, gas emission, and phreatic explosion). Several airports have been affected repeatedly by volcanic hazards. Four airports have been affected the most often and likely will continue to be among the most vulnerable owing to continued nearby volcanic activity: Fontanarossa International Airport in Catania, Italy; Ted Stevens Anchorage International Airport in Alaska, USA; Mariscal Sucre International Airport in Quito, Ecuador; and Tokua Airport in Kokopo, Papua New Guinea. The USA has the most airports affected by volcanic activity (17) on the most occasions (33) and hosts the second highest number of volcanoes that have caused the disruptions (5, after Indonesia with 7). One-fifth of the affected airports are within 30 km of the source volcanoes, approximately half are located within 150 km of the source volcanoes, and about three-quarters are within 300 km; nearly one-fifth are located more than 500 km away from the source volcanoes. The volcanoes that have caused the most impacts are Soufriere Hills on the island of Montserrat in the British West Indies

  4. New Age and Geochemical Data From Seamounts in the Canary and Madeira Volcanic Provinces: A Contribution to the "Great Plume Debate" (United States)

    Geldmacher, J.; Hoernle, K.; van den Bogaard, P.; Duggen, S.; Werner, R.


    The role of hotspots (mantle plumes) in the formation of intraplate volcanic island and seamount groups is being increasingly questioned, in particular concerning the abundant and somewhat irregularly distributed island and seamount volcanoes off the coast of northwest Africa. However, new 40Ar/39Ar ages and Sr-Nd-Pb isotope geochemistry of volcanic rocks from two seamounts northeast of the Canary Islands and two northeast of the Madeira Islands provide new support for the plume hypothesis. The oldest ages of shield stage volcanism from seamounts and islands northeast of the Canary and Madeira Islands confirm progressions of increasing age to the northeast for both island/seamount chains consistent with northeast directed plate motion. Calculated angular velocities for the average movement of the African plate in both regions gave similar values of about 0.45\\deg plus/minus 0.05\\deg/Ma around a rotation pole located north of the Azores Islands. Furthermore, the curvature of the chains clearly deviates from the E-W orientation of fracture zones in the East Atlantic. A local control of surface volcanism by lithospheric zones of weakness, however, is likely for some E-W elongated seamounts and islands. The isotope geochemistry additionally confirms that the two volcanic provinces are derived from distinct sources, consistent with distinct mantle plumes having formed both volcanic groups. Conventional hotspot models, however, cannot easily explain the wide distribution of seamounts in the Canary region and the long history of volcanic activity at single volcanic centers (e.g. Dacia seamount, 47-4 Ma; Selvagen Islands, 30-3 Ma). A possible explanation could involve interaction of a Canary mantle plume with small-scale upper mantle processes such as edge driven convection at the edge of the NW African craton (e.g. King and Ritsema, 2000, Science 290, 1137-1140).

  5. The Campi Flegrei Blind Test: Evaluating the Imaging Capability of Local Earthquake Tomography in a Volcanic Area

    Directory of Open Access Journals (Sweden)

    E. Priolo


    Full Text Available During the 1982–1984 bradyseismic crises in the Campi Flegrei area (Italy, the University of Wisconsin deployed a network of seismological stations to record local earthquakes. In order to analyse the potential of the recorded data in terms of tomographic imaging, a blind test was recently set up and carried out in the framework of a research project. A model representing a hypothetical 3D structure of the area containing the Campi Flegrei caldera was also set up, and a synthetic dataset of time arrivals was in turn computed. The synthetic dataset consists of several thousand P- and S-time arrivals, computed at about fourteen stations. The tomographic inversion was performed by four independent teams using different methods. The teams had no knowledge of either the input velocity model or the earthquake hypocenters used to create the synthetic dataset. The results obtained by the different groups were compared and analysed in light of the true model. This work provides a thorough analysis of the earthquake tomography potential of the dataset recording the seismic activity at Campi Flegrei in the 1982–1984 period. It shows that all the tested earthquake tomography methods provide reliable low-resolution images of the background velocity field of the Campi Flegrei area, but with some differences. However, none of them succeeds in detecting the hypothetical structure details (i.e. with a size smaller than about 1.5–2 km, such as a magmatic chamber 4 km deep and especially the smaller, isolated bodies, which represent possible magmatic chimneys and intrusions.

  6. Neogene Tiporco Volcanic Complex, San Luis, Argentina: An explosive event in a regional transpressive - local transtensive setting in the pampean flat slab (United States)

    Ibañes, Oscar Damián; Sruoga, Patricia; Japas, María Silvia; Urbina, y. Nilda Esther


    The Neogene Tiporco Volcanic Complex (TVC) is located in the Sierras Pampeanas of San Luis, Argentina, at the southeast of the Pampean flat-slab segment. Based on the comprehensive study of lithofacies and structures, the reconstruction of the volcanic architecture has been carried out. The TVC has been modeled in three subsequent stages: 1) initial updoming, 2) ignimbritic eruptive activity and 3) lava dome emplacement. Interplay of magma injection and transtensional tectonic deformation has been invoked to reproduce TVC evolution.

  7. Zooming into local active galactic nuclei: the power of combining SDSS-IV MaNGA with higher resolution integral field unit observations (United States)

    Wylezalek, Dominika; Schnorr Müller, Allan; Zakamska, Nadia L.; Storchi-Bergmann, Thaisa; Greene, Jenny E.; Müller-Sánchez, Francisco; Kelly, Michael; Liu, Guilin; Law, David R.; Barrera-Ballesteros, Jorge K.; Riffel, Rogemar A.; Thomas, Daniel


    Ionized gas outflows driven by active galactic nuclei (AGN) are ubiquitous in high-luminosity AGN with outflow speeds apparently correlated with the total bolometric luminosity of the AGN. This empirical relation and theoretical work suggest that in the range Lbol ˜ 1043-45 erg s-1 there must exist a threshold luminosity above which the AGN becomes powerful enough to launch winds that will be able to escape the galaxy potential. In this paper, we present pilot observations of two AGN in this transitional range that were taken with the Gemini North Multi-Object Spectrograph integral field unit (IFU). Both sources have also previously been observed within the Sloan Digital Sky Survey-IV (SDSS) Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey. While the MaNGA IFU maps probe the gas fields on galaxy-wide scales and show that some regions are dominated by AGN ionization, the new Gemini IFU data zoom into the centre with four times better spatial resolution. In the object with the lower Lbol we find evidence of a young or stalled biconical AGN-driven outflow where none was obvious at the MaNGA resolution. In the object with the higher Lbol we trace the large-scale biconical outflow into the nuclear region and connect the outflow from small to large scales. These observations suggest that AGN luminosity and galaxy potential are crucial in shaping wind launching and propagation in low-luminosity AGN. The transition from small and young outflows to galaxy-wide feedback can only be understood by combining large-scale IFU data that trace the galaxy velocity field with higher resolution, small-scale IFU maps.

  8. Volcanic risk

    International Nuclear Information System (INIS)

    Rancon, J.P.; Baubron, J.C.


    This project follows the previous multi-disciplinary studies carried out by the French Bureau de Recherches Geologiques et Minieres (BRGM) on the two active volcanoes of the French lesser Antilles: Mt Pelee (Martinique) and Soufriere (Guadeloupe) for which geological maps and volcanic risk studies have been achieved. The research program comprises 5 parts: the study of pyroclastic deposits from recent eruptions of the two volcanoes for a better characterization of their eruptive phenomenology and a better definition of crisis scenarios; the study of deposits and structures of active volcanoes from Central America and the study of eruptive dynamics of andesite volcanoes for a transposition to Antilles' volcanoes; the starting of a methodological multi-disciplinary research (volcanology, geography, sociology...) on the volcanic risk analysis and on the management of a future crisis; and finally, the development of geochemical survey techniques (radon, CO 2 , H 2 O) on active volcanoes of Costa-Rica and Europe (Fournaise, Furnas, Etna) and their application to the Soufriere. (J.S.). 9 refs., 3 figs


    Energy Technology Data Exchange (ETDEWEB)

    Perry, F. V.; Crowe, G. A.; Valentine, G. A.; Bowker, L. M.


    This report synthesizes the results of volcanism studies conducted by scientists at the Los Alamos National Laboratory and collaborating institutions on behalf of the Department of Energy's Yucca Mountain Project. Chapter 1 introduces the volcanism issue for the Yucca Mountain site and provides the reader with an overview of the organization, content, and significant conclusions of this report. The hazard of future basaltic volcanism is the primary topic of concern including both events that intersect a potential repository and events that occur near or within the waste isolation system of a repository. Future volcanic events cannot be predicted with certainty but instead are estimated using formal methods of probabilistic volcanic hazard assessment (PVHA). Chapter 2 describes the volcanic history of the Yucca Mountain region (YMR) and emphasizes the Pliocene and Quaternary volcanic record, the interval of primary concern for volcanic risk assessment. The distribution, eruptive history, and geochronology of Plio-Quaternary basalt centers are described by individual center emphasizing the younger postcaldera basalt (<5 Ma). The Lathrop Wells volcanic center is described in detail because it is the youngest basalt center in the YMR. The age of the Lathrop Wells center is now confidently determined to be about 75 thousand years old. Chapter 3 describes the tectonic setting of the YMR and presents and assesses the significance of multiple alternative tectonic models. The distribution of Pliocene and Quaternary basaltic volcanic centers is evaluated with respect to tectonic models for detachment, caldera, regional and local rifting, and the Walker Lane structural zone. Geophysical data are described for the YMR and are used as an aid to understand the distribution of past basaltic volcanic centers and possible future magmatic processes. Chapter 4 discusses the petrologic and geochemical features of basaltic volcanism in the YMR, the southern Great Basin and the

  10. Neogene volcanism in Gutai Mts. (Eastern Carpathains: a review

    Directory of Open Access Journals (Sweden)

    Marinel Kovacs


    Full Text Available Two types of volcanism developed in Gutâi Mts. (inner volcanic chain of Eastern Carpathians: a felsic, extensional/“back-arc” type and an intermediate, arc type. The felsic volcanism of explosive origin, consisting of caldera-related rhyolitic ignimbrites and resedimented volcaniclastics, had taken place during Early-Middle Badenian and Early Sarmatian. The intermediate volcanism, consisting of extrusive (effusive and explosive and intrusive activity, had developed during Sarmatian and Pannonian (13.4-7.0 Ma. It is represented by typical calc-alkaline series, from basalts to rhyolites. Lava flows of basaltic andesites and andesites are predominant, often emplaced in subaqueous environment. Extrusive domes, mainly composed of dacites, are associated to the andesitic volcanic structures. The intermediate volcanism, consisting of extrusive (effusive and explosive and intrusive activity, had developed during Sarmatian and Pannonian (13.4-7.0 Ma. It is represented by typical calc-alkaline series, from basalts to rhyolites. Lava flows of basaltic andesites and andesites are predominant, often emplaced in subaqueous environment. Extrusive domes, mainly composed of dacites, are associated to the andesitic volcanic structures. The geochemical study on the volcanic rocks shows the calc-alkaline character of both felsic and intermediate volcanism and typical subduction zones geochemical signatures for the intermediate one. The felsic volcanism shows affinities with subduction-related rocks as well. The main petrogenetic process in Gutâi Mts. was crustal assimilation, strongly constrained by trace element and isotope geochemistry.

  11. Prácticas culinarias y (reconocimiento de la diversidad local de verduras silvestres en el Colectivo Mujeres y Maíz de Teopisca, Chiapas, México

    Directory of Open Access Journals (Sweden)

    Celina Guadalupe Solís Becerra


    Full Text Available Se analizan los saberes y acciones relacionados con la diversidad local de verduras silvestres, reconocida por las integrantes del Colectivo Mujeres y Maíz de Teopisca, Chiapas, México, a partir de sus prácticas culinarias. Se documentaron trece especies de verduras silvestres mayormente presentes en traspatios y 33 recetas culinarias con incorporación de tales especies. Se destaca la importancia de las verduras silvestres, la gastronomía local, el trabajo cotidiano y la vida campesina, con los cuales se enriquece la relación que las mujeres del colectivo y sus familias tienen con la biodiversidad local a través de su cultura alimentaria.

  12. Structural control on arc volcanism: The Caviahue Copahue complex, Central to Patagonian Andes transition (38°S) (United States)

    Melnick, Daniel; Folguera, Andrés; Ramos, Victor A.


    This paper describes the volcanostratigraphy, structure, and tectonic implications of an arc volcanic complex in an oblique subduction setting: the Caviahue caldera Copahue volcano (CAC) of the Andean margin. The CAC is located in a first-order morphotectonic transitional zone, between the low and narrow Patagonian and the high and broad Central Andes. The evolution of the CAC started at approximately 4-3 Ma with the opening of the 20 × 15 km Caviahue pull-apart caldera; Las Mellizas volcano formed inside the caldera and collapsed at approximately 2.6 Ma; and the Copahue volcano evolved in three stages: (1) 1.2-0.7 Ma formed the approximately 1 km thick andesitic edifice, (2) 0.7-0.01 Ma erupted andesitic-dacitic subglacial pillow lavas, and (3) 0.01-0 Ma erupted basaltic-andesites and pyroclastic flows from fissures, aligned cones, and summit craters. Magma ascent has occurred along planes perpendicular to the least principal horizontal stress, whereas hydrothermal activity and hot springs also occur along parallel planes. At a regional scale, Quaternary volcanism concentrates along the NE-trending, 90 km long Callaqui-Copahue-Mandolegüe lineament, the longest of the southern volcanic zone, which is here interpreted as an inherited crustal-scale transfer zone from a Miocene rift basin. At a local scale within the CAC, effusions are controlled by local structures that formed at the intersection of regional fault systems. The Central to Patagonian Andes transition occurs at the Callaqui-Copahue-Mandolegüe lineament, which decouples active deformation from the intra-arc strike-slip Liquiñe-Ofqui fault zone to the south and the backarc Copahue-Antiñir thrust system.

  13. Basaltic volcanic episodes of the Yucca Mountain region

    International Nuclear Information System (INIS)

    Crowe, B.M.


    The purpose of this paper is to summarize briefly the distribution and geologic characteristics of basaltic volcanism in the Yucca Mountain region during the last 10--12 Ma. This interval largely postdates the major period of silicic volcanism and coincides with and postdates the timing of major extensional faulting in the region. Field and geochronologic data for the basaltic rocks define two distinct episodes. The patterns in the volume and spatial distribution of these basaltic volcanic episodes in the central and southern part of the SNVF are used as a basis for forecasting potential future volcanic activity in vicinity of Yucca Mountain. 33 refs., 2 figs

  14. Multivariate Analysis, Mass Balance Techniques, and Statistical Tests as Tools in Igneous Petrology: Application to the Sierra de las Cruces Volcanic Range (Mexican Volcanic Belt) (United States)

    Velasco-Tapia, Fernando


    Magmatic processes have usually been identified and evaluated using qualitative or semiquantitative geochemical or isotopic tools based on a restricted number of variables. However, a more complete and quantitative view could be reached applying multivariate analysis, mass balance techniques, and statistical tests. As an example, in this work a statistical and quantitative scheme is applied to analyze the geochemical features for the Sierra de las Cruces (SC) volcanic range (Mexican Volcanic Belt). In this locality, the volcanic activity (3.7 to 0.5 Ma) was dominantly dacitic, but the presence of spheroidal andesitic enclaves and/or diverse disequilibrium features in majority of lavas confirms the operation of magma mixing/mingling. New discriminant-function-based multidimensional diagrams were used to discriminate tectonic setting. Statistical tests of discordancy and significance were applied to evaluate the influence of the subducting Cocos plate, which seems to be rather negligible for the SC magmas in relation to several major and trace elements. A cluster analysis following Ward's linkage rule was carried out to classify the SC volcanic rocks geochemical groups. Finally, two mass-balance schemes were applied for the quantitative evaluation of the proportion of the end-member components (dacitic and andesitic magmas) in the comingled lavas (binary mixtures). PMID:24737994

  15. Multivariate Analysis, Mass Balance Techniques, and Statistical Tests as Tools in Igneous Petrology: Application to the Sierra de las Cruces Volcanic Range (Mexican Volcanic Belt

    Directory of Open Access Journals (Sweden)

    Fernando Velasco-Tapia


    Full Text Available Magmatic processes have usually been identified and evaluated using qualitative or semiquantitative geochemical or isotopic tools based on a restricted number of variables. However, a more complete and quantitative view could be reached applying multivariate analysis, mass balance techniques, and statistical tests. As an example, in this work a statistical and quantitative scheme is applied to analyze the geochemical features for the Sierra de las Cruces (SC volcanic range (Mexican Volcanic Belt. In this locality, the volcanic activity (3.7 to 0.5 Ma was dominantly dacitic, but the presence of spheroidal andesitic enclaves and/or diverse disequilibrium features in majority of lavas confirms the operation of magma mixing/mingling. New discriminant-function-based multidimensional diagrams were used to discriminate tectonic setting. Statistical tests of discordancy and significance were applied to evaluate the influence of the subducting Cocos plate, which seems to be rather negligible for the SC magmas in relation to several major and trace elements. A cluster analysis following Ward’s linkage rule was carried out to classify the SC volcanic rocks geochemical groups. Finally, two mass-balance schemes were applied for the quantitative evaluation of the proportion of the end-member components (dacitic and andesitic magmas in the comingled lavas (binary mixtures.

  16. The Middlesex Fells Volcanic Complex: A Revised Tectonic Model based on Geochronology, Geochemistry, and Field Data (United States)

    Hampton, R.


    The Boston Bay area is composed of several terranes originating on the paleocontinent of Avalonia, an arc terrane that accreted onto the continent of Laurentia during the Devonian. Included in these terranes is the Middlesex Fells Volcanic Complex, a bimodal complex composed of both intrusive and extrusive igneous rocks. Initial studies suggested that this volcanic complex formed during a rift event as the Avalonian continent separated from its parent continent 700-900 Ma. New geochemical and geochronological data and field relationships observed in this study establishes a new tectonic model. U-Pb laser ablation zircon data on four samples from different units within the complex reveal that the complex erupted 600 Ma. ICP-MS geochemical analysis of the metabasalt member of the complex yield a trace element signature enriched in Rb, Pb, and Sr and depleted in Th, indicating a subduction component to the melt and interpreted as an eruption into a back-arc basin. The felsic units similarly have an arc related signature when plotted on trace element spider diagrams and tectonic discrimination diagrams. Combined with the field relationships, including an erosional unconformity, stratigraphic and intrusional relationships and large faults from episodic extension events, this data suggests that the Middlesex Fells Volcanic Complex was erupted as part of the arc-sequence of Avalonia and as part of the formation of a back-arc basin well after Avalonia separated from its parent continent. This model presents a significantly younger eruption scenario for the Middlesex Fells Volcanics than previously hypothesized and may be used to study and compare to other volcanics from Avalon terranes in localities such as Newfoundland and the greater Boston area.

  17. Volcanic features of Io

    International Nuclear Information System (INIS)

    Carr, M.H.; Masursky, H.; Strom, R.G.; Terrile, R.J.


    The volcanic features of Io as detected during the Voyager mission are discussed. The volcanic activity is apparently higher than on any other body in the Solar System. Its volcanic landforms are compared with features on Earth to indicate the type of volcanism present on Io. (U.K.)

  18. Thermal and mass implications of magmatic evolution in the Lassen volcanic region, California, and minimum constraints on basalt influx to the lower crust (United States)

    Guffanti, M.; Clynne, M.A.; Muffler, L.J.P.


    We have analyzed the heat and mass demands of a petrologic model of basaltdriven magmatic evolution in which variously fractionated mafic magmas mix with silicic partial melts of the lower crust. We have formulated steady state heat budgets for two volcanically distinct areas in the Lassen region: the large, late Quaternary, intermediate to silicic Lassen volcanic center and the nearby, coeval, less evolved Caribou volcanic field. At Caribou volcanic field, heat provided by cooling and fractional crystallization of 52 km3 of basalt is more than sufficient to produce 10 km3 of rhyolitic melt by partial melting of lower crust. Net heat added by basalt intrusion at Caribou volcanic field is equivalent to an increase in lower crustal heat flow of ???7 mW m-2, indicating that the field is not a major crustal thermal anomaly. Addition of cumulates from fractionation is offset by removal of erupted partial melts. A minimum basalt influx of 0.3 km3 (km2 Ma)-1 is needed to supply Caribou volcanic field. Our methodology does not fully account for an influx of basalt that remains in the crust as derivative intrusives. On the basis of comparison to deep heat flow, the input of basalt could be ???3 to 7 times the amount we calculate. At Lassen volcanic center, at least 203 km3 of mantle-derived basalt is needed to produce 141 km3 of partial melt and drive the volcanic system. Partial melting mobilizes lower crustal material, augmenting the magmatic volume available for eruption at Lassen volcanic center; thus the erupted volume of 215 km3 exceeds the calculated basalt input of 203 km3. The minimum basalt input of 1.6 km3 (km2 Ma)-1 is >5 times the minimum influx to the Caribou volcanic field. Basalt influx high enough to sustain considerable partial melting, coupled with locally high extension rate, is a crucial factor in development of Lassen volcanic center; in contrast. Caribou volcanic field has failed to develop into a large silicic center primarily because basalt supply

  19. Producción de rastrojo y grano de variedades locales de maíz en condiciones de temporal en los valles altos de Libres-Serdán, Puebla, México

    Directory of Open Access Journals (Sweden)

    Faviola Muñoz-Tlahuiz


    Full Text Available El rastrojo de maíz es un subproducto importante para la alimentación de varias especies pecuarias en unidades de producción bajo condiciones de temporal de los valles altos de México. En estas zonas se carece de variedades que produzcan en suficiencia grano y rastrojo (variedades de doble propósito; por lo que en el presente estudio se evaluó la producción de rastrojo y grano de variedades locales de maíz en los valles altos de Puebla y Tlaxcala, México. Se colectó semilla en las regiones Libres-Mazapiltepec-Huamantla (L-M-H y Serdán-Tlachichuca-Guadalupe Victoria (S-T- GV. Para cada región se evaluaron 144 variedades, incluyendo cuatro testigos comerciales, en dos localidades bajo un diseño látice simple 12x12 con dos repeticiones. Se midió rendimiento de rastrojo, producción de hoja y tallo, altura de planta y de mazorca, días a floración femenina, y rendimiento de grano. En cada experimento se realizó un análisis de varianza y por cada región un análisis combinado además de un análisis de correlación canónica. En cada región se encontró una diversidad amplia para rendimiento de rastrojo y grano (P<0.01 que fue desde bajo hasta alto rendimiento. Se detectaron algunas variedades locales que para ambas características fueron sobresalientes (P<0.05. Los testigos comerciales ensayados tuvieron menores rendimientos de grano y rastrojo que las variedades locales sobresalientes.

  20. Unzen volcanic rocks as heat source of geothermal activity

    Energy Technology Data Exchange (ETDEWEB)

    Hayashi, Masao; Sugiyama, Hiromi


    Only a few radiometric ages have been reported so far for the Unzen volcanic rocks. In this connection, in order to clarify the relation between volcanism and geothermal activity, fission track ages of zircon seperated from the Unzen volcanic rocks in western Kyushu have been dated. Since all the rocks are thought to be young, the external surface re-etch method was adopted. The results are that the age and standard error of the basal volcaniclastic rocks of the Tatsuishi formation are 0.28 +- 0.05 Ma and 0.25 +- 0.05 Ma. The next oldest Takadake lavas range from 0.26 to 0.20 Ma. The Kusenbudake lavas fall in a narrow range from 0.19 to 0.17 Ma. The latest Fugendake lavas are younger than 0.07 Ma.In conclusion, the most promising site for geothermal power generation is the Unzen hot spring field because of its very high temperature. After that, comes the Obama hot spring field because of the considerable high temperature chemically estimated. In addition, the northwestern area of the Unzen volcanic region will be promising for electric power generation in spite of no geothermal manifestations, since its volcanos are younger than 0.2 Ma. (14 figs, 14 tabs, 22 refs)

  1. Age, geochemical affinity and geodynamic setting of granitoids and felsic volcanics in the basement of Wrangel Island (United States)

    Luchitskaya, Marina; Moiseev, Artem; Sokolov, Sergey; Tuchkova, Marianna; Sergeev, Sergey


    Granitoids and basic rocks of Wrangel Island are the components of Precambrian metamorphic basement, exposed in the anticlinorium in the central part of the island and named as Wrangel complex (Kameneva, 1970; Ageev, 1979; Til'man et al., 1964, 1970; Ganelin, 1989; Kos'ko et al., 1993, 2003). The latter is composed of volcanic, volcaniclastic and clastic rocks metamorphosed in greenshist to locally lower amphibolite facies (Kos'ko et al., 2003; Cecile et al., 1991). Obtained earlier datings of granitoids and basic rocks from Wrangel complex display a wide scatter: 609-700 Ma, U-Pb zircon (Cecile et al., 1991; Kos'ko et al., 1993); 590 Ma, Pb-Pb zircon; 574, 575 Ma, K-Ar whole rock; 475 Ma, Rb-Sr muscovite (Kos'ko et al., 2003). Our previous U-Pb SHRIMP datings indicate the episode of granitoid activity in 681-707 Ma (Luchitskaya et al., 2014). Here we present new results from zircon SIMS and LA-ICP-MS U-Pb dating and geochemical data for granites and felsic volcanics of Wrangel complex. Granites of Wrangel complex in the area of Khishchnikov River form small tabular bodies less than 30 meters in thickness. They range from slightly recrystallized muscovite granites to gneissic and mylonitic ones. Felsic and basic volcanics are exposed in the central part of Wrangel Island (rivers Neizvestnaya and Krasnyy Flag). Their interrelations are unknown and earlier they were considered as single bymodal assemblage of C1 sequence (Kos'ko et. al., 1993, 2003). Samples were collected in the area of Pervaya Mountain, visible thickness of volcanics ~100 meters. Basalts are overlain by conglomerates with detrite zircons no younger than 550 Ma (Moiseev et al., 2009, 2015). Wheited mean ages of zircons from muscovite granites and mylonitic ones are 592.9±6.7 Ma (n=10) and 692.9±5.0 Ma (n=30); in two samples we suppose the age of crystallization ~700 Ma. Wheited mean ages of zircons from felsic volcanics are 594.4±7.1 Ma (n=10) and 598.6±7.5 Ma (n=10). Granites and felsic

  2. Comment on "Geochemistry of the Early Miocene volcanic succession of Northland, New Zealand, and implications for the evolution of subduction in the Southwest Pacific" by M.A. Booden, I.E.M. Smith, P.M. Black and J.L. Mauk

    NARCIS (Netherlands)

    Schellart, W. P.


    In a recent paper Booden et al. (2011) present new geochemical and petrological data of Early Miocene volcanics from the Northland region (Northland volcanic belt) in New Zealand, and interpret these data to support a particular regional tectonic model. This tectonic model involves Early Miocene

  3. Ejection age of volcano rocks and trend of volcanic activity

    Energy Technology Data Exchange (ETDEWEB)

    Sakaguchi, Keiichi


    This report is II-7 of an interim report on research and development of the Sunshine Project for 1986. This report considers on the trend of volcanic activities in the South of Kyushu area. K-Ar age measurement was newly made and reported. Age values obtained were 1.09 plus minus 0.21 Ma for Nagaoyama andesite, 1.33 plus minus 0.18 Ma for Nozato andesite, and 0.3 plus minus 0.1 Ma for Imuta volcanos. Including these age values, from the age values and their distribution of the volcanic rocks in the South Kyushu district, the following three districts were selected to represent the volcanic activities since the Pliocene Epoch. As these districts are mutually overwrapped, verification at these overwrapped districts are necessary. (4 figs, 1 tab, 12 refs)

  4. Unexpected HIMU-type late-stage volcanism on the Walvis Ridge (United States)

    Homrighausen, S.; Hoernle, K.; Geldmacher, J.; Wartho, J.-A.; Hauff, F.; Portnyagin, M.; Werner, R.; van den Bogaard, P.; Garbe-Schönberg, D.


    Volcanic activity at many oceanic volcanoes, ridges and plateaus often reawakens after hiatuses of up to several million years. Compared to the earlier magmatic phases, this late-stage (rejuvenated/post-erosional) volcanism is commonly characterized by a distinct geochemical composition. Late-stage volcanism raises two hitherto unanswered questions: Why does volcanism restart after an extended hiatus and what is the origin of this volcanism? Here we present the first 40Ar/39Ar age and comprehensive trace element and Sr-Nd-Pb-Hf isotopic data from seamounts located on and adjacent to the Walvis Ridge in the South Atlantic ocean basin. The Walvis Ridge is the oldest submarine part of the Tristan-Gough hotspot track and is famous as the original type locality for the enriched mantle one (EM I) end member. Consistent with the bathymetric data, the age data indicates that most of these seamounts are 20-40 Myr younger than the underlying or nearby Walvis Ridge basement. The trace element and isotope data reveal a distinct compositional range from the EM I-type basement. The composition of the seamounts extend from the St. Helena HIMU (high time-integrated 238U/204Pb mantle with radiogenic Pb isotope ratios) end member to an enriched (E) Mid-Ocean-Ridge Basalt (MORB) type composition, reflecting a two-component mixing trend on all isotope diagrams. The EMORB end member could have been generated through mixing of Walvis Ridge EM I with normal (N) MORB source mantle, reflecting interaction of Tristan-Gough (EM I-type) plume melts with the upper mantle. The long volcanic quiescence and the HIMU-like geochemical signature of the seamounts are unusual for classical hotspot related late-stage volcanism, indicating that these seamounts are not related to the Tristan-Gough hotspot volcanism. Two volcanic arrays in southwestern Africa (Gibeon-Dicker Willem and Western Cape province) display similar ages to the late-stage Walvis seamounts and also have HIMU-like compositions

  5. The upper lithostratigraphic unit of ANDRILL AND-2A core (Southern McMurdo Sound, Antarctica): local Pleistocene volcanic sources, paleoenvironmental implications and subsidence in the southern Victoria Land Basin (United States)

    Del Carlo, P.; Panter, K. S.; Bassett, K. N.; Bracciali, L.; di Vincenzo, G.; Rocchi, S.


    We report results from the study of the uppermost 37 meters of the Southern McMurdo Sound (SMS) AND-2A drillcore, corresponding to the lithostratigraphic unit 1 (LSU 1), the most volcanogenic unit within the core. Nearly all of LSU 1 consists of volcanic breccia and sandstone that is a mixture of near primary volcanic material dominated by lava and vitric clasts with minor exotic material derived from distal basement sources. Lava clasts and glass are mafic and range from strongly alkaline (basanite, tephrite) to moderately alkaline (alkali basalt, hawaiite) compositions that are similar to nearby land deposits. 40Ar-39Ar laser step-heating analyses on groundmass separated from lava clasts yield Pleistocene ages (692±38 and 793±63, ±2σ internal errors). Volcanoes of the Dailey Island group, located ~13 km SW of the drillsite, are a possible source for the volcanic materials based on their close proximity, similar composition and age. A basanite lava flow on Juergens Island yields a comparable Pleistocene age of 775±22 ka. Yet there is evidence to suggest that the volcanic source is much closer to the drillsite and that the sediments were deposited in much shallower water relative to the present-day water depth of 384 mbsl. Evidence for local volcanic activity is based in part on the common occurrence of delicate vitriclasts (e.g. glass shards and Pele’s hair) and a minimally reworked ~2 meter thick monomict breccia that is interpreted to have formed by autobrecciating lava. In addition, conical-shaped seamounts and high frequency magnetic anomalies encompass the drillsite and extend south including the volcanoes of the Dailey Islands. Sedimentary features and structures indicate shallow water sedimentation for the whole of LSU 1. Rippled asymmetric cross-laminated sands and hummocky cross-stratification occur intermittently throughout LSU 1 and indicate water depths shallower than 100 meters. The occurrence of ooliths and layers containing siderite and Fe

  6. A new model for the development of the active Afar volcanic margin (United States)

    Pik, Raphaël; Stab, Martin; Bellahsen, Nicolas; Leroy, Sylvie


    Volcanic passive margins, that represent more than the three quarters of continental margins worldwide, are privileged witnesses of the lithospheric extension processes thatform new oceanic basins. They are characterized by voluminous amounts of underplated, intruded and extruded magmas, under the form of massive lavas prisms (seaward-dipping reflectors, or SDR) during the course of thinning and stretching of the lithosphere, that eventually form the ocean-continent transition. The origin and mechanisms of formation of these objects are still largely debated today. We have focussed our attention in the last few years on the Afar volcanic province which represents an active analogue of such volcanic margins. We explored the structural and temporal relationships that exist between the development of the major thinning and stretching structures and the magmatic production in Central Afar. Conjugate precise fieldwork analysis along with lavas geochronology allowed us to revisit the timing and style of the rift formation, since the early syn-rift period of time in the W-Afar marginal area to present days. Extension is primarily accommodated over a wide area at the surface since the very initial periods of extension (~ 25 Ma) following the emplacement of Oligocene CFBs. We propose in our reconstruction of central Afar margin history that extension has been associated with important volumes of underplated mafic material that compensate crustal thinning. This has been facilitated by major crustal-scale detachments that help localize the thinning and underplating at depth. In line with this 'magmatic wide-rift' mode of extension, we demonstrate that episodic extension steps alternate with more protracted magmatic phases. The production of syn-rift massive flood basalts (~ 4 Ma) occurs after early thinning of both the crust and the lithosphere, which suggests that SDR formation, is controlled by previous tectonic event. We determined how the melting regime evolved in

  7. Recurrent Early Cretaceous, Indo-Madagascar (89-86 Ma) and Deccan (66 Ma) alkaline magmatism in the Sarnu-Dandali complex, Rajasthan: 40Ar/39Ar age evidence and geodynamic significance (United States)

    Sheth, Hetu; Pande, Kanchan; Vijayan, Anjali; Sharma, Kamal Kant; Cucciniello, Ciro


    The Sarnu-Dandali alkaline complex in Rajasthan, northwestern India, is considered to represent early, pre-flood basalt magmatism in the Deccan Traps province, based on a single 40Ar/39Ar age of 68.57 Ma. Rhyolites found in the complex are considered to be 750 Ma Malani basement. Our new 40Ar/39Ar ages of 88.9-86.8 Ma (for syenites, nephelinite, phonolite and rhyolite) and 66.3 ± 0.4 Ma (2σ, melanephelinite) provide clear evidence that whereas the complex has Deccan-age (66 Ma) components, it is dominantly an older (by 20 million years) alkaline complex, with rhyolites included. Basalt is also known to underlie the Early Cretaceous Sarnu Sandstone. Sarnu-Dandali is thus a periodically rejuvenated alkaline igneous centre, active twice in the Late Cretaceous and also earlier. Many such centres with recurrent continental alkaline magmatism (sometimes over hundreds of millions of years) are known worldwide. The 88.9-86.8 Ma 40Ar/39Ar ages for Sarnu-Dandali rocks fully overlap with those for the Indo-Madagascar flood basalt province formed during continental breakup between India (plus Seychelles) and Madagascar. Recent 40Ar/39Ar work on the Mundwara alkaline complex in Rajasthan, 120 km southeast of Sarnu-Dandali, has also shown polychronous emplacement (over ≥ 45 million years), and 84-80 Ma ages obtained from Mundwara also arguably represent post-breakup stages of the Indo-Madagascar flood basalt volcanism. Remnants of the Indo-Madagascar province are known from several localities in southern India but hitherto unknown from northwestern India 2000 km away. Additional equivalents buried under the vast Deccan Traps are highly likely.

  8. Volcanic signals in oceans

    KAUST Repository

    Stenchikov, Georgiy L.; Delworth, Thomas L.; Ramaswamy, V.; Stouffer, Ronald J.; Wittenberg, Andrew; Zeng, Fanrong


    Sulfate aerosols resulting from strong volcanic explosions last for 2–3 years in the lower stratosphere. Therefore it was traditionally believed that volcanic impacts produce mainly short-term, transient climate perturbations. However, the ocean

  9. A Study of the Dětaň Locality (Oligocene, Doupovské hory Mts. Volcanic Complex, Czech Republic): Collection of Field Data and Starting Points for Interpretation

    Czech Academy of Sciences Publication Activity Database

    Mikuláš, Radek; Fejfar, O.; Ulrych, Jaromír; Žigová, Anna; Kadlecová, Eva; Cajz, Vladimír


    Roč. 15, - (2003), s. 91-97 ISSN 1210-9606. [Hibsch 2002 Symposium. Teplá near Třebenice, Ústí nad Labem, Mariánské Lázně, 03.06.2002-08.06.2002] R&D Projects: GA ČR GA205/00/1000 Institutional research plan: CEZ:AV0Z3013912 Keywords : volcanic lastic rocks * Oligocene * Doupovské hory Mts. Subject RIV: DB - Geology ; Mineralogy

  10. Change with time in extrusion and chemical composition of volcanic rock in geothermal areas in central Kyushu

    Energy Technology Data Exchange (ETDEWEB)

    Kamata, Hiroki


    Changes with time in extrusion and chemical composition of volcanic rocks in central Kyushu are studied to provide basic data required for evaluation of geothermal resources. Distribution of volcanic rocks in successive 1Ma (10/sup 6/ year) periods and the average thickness of volcanic rock layers in each period are determined, from which the volume of volcanic rocks in each 1Ma period is calculated. Results indicate that volcanos in central Kyushu extruded about 3,000 km/sup 3//Ma of volcanic rocks during the early periods (about 5Ma), followed by a series of declining periods up to the present. Comparison of volcanic extrusive rocks of each 1Ma period shows that lava of hornblende andesite and pyroxenic andesite has been extruded in great quantities in every period. Chemical composition is studied based on diagrams showing changes in SiO/sub 2/ content. The K/sub 2/O content is relatively high in most volcanos younger than 1.6Ma, compared to those older than 1.6Ma. the K/sub 2/O content in extruded rocks has been high during the latest 0.4Ma in the Aso volcanic area, unlike other island arc conjunction areas. (4 figs, 5 tabs, 28 refs)

  11. Geochemical and geochronological constrains on the Chiang Khong volcanic rocks (northwestern Thailand) and its tectonic implications (United States)

    Qian, Xin; Feng, Qinglai; Chonglakmani, Chongpan; Monjai, Denchok


    Volcanic rocks in northwestern Thailand exposed dominantly in the Chiang Khong area, are commonly considered to be genetically linked to the tectonic evolution of the Paleo-Tethyan Ocean. The volcanic rocks consist mainly of andesitic to rhyolitic rocks and are traditionally mapped as Permian-Triassic sequences. Our zircon U-Pb geochronological results show that two andesitic samples (TL-1-B and TL-31-B), are representative of the Doi Yao volcanic zone, and give a mean weighted age of 241.2±4.6 Ma and 241.7±2.9 Ma, respectively. The rhyolitic sample (TL-32-B1) from the Doi Khun Ta Khuan volcanic zone erupted at 238.3±3.8 Ma. Such ages indicate that Chiang Khong volcanic rocks erputed during the early Middle Triassic period. Seven samples from the Doi Yao and Doi Khun Ta Khuan zones exhibit an affinity to arc volcanics. Three rhyolitic samples from the Chiang Khong area have a geochemical affinity to both arc and syn-collisional volcanic rocks. The Chiang Khong arc volcanic rocks can be geochemically compared with those in the Lampang area in northern Thailand, also consistent with those in Jinghong area of southwestern Yunnan. This indicates that the Chiang Rai arc-volcanic zone might northwardly link to the Lancangjiang volcanic zone in southwestern China.

  12. Sr isotope geochemistry of voluminous acidic pyroclastics erupted at 1-3 Ma in Northeast Japan

    International Nuclear Information System (INIS)

    Shirahase, Teruo; Tamanyu, Shiro; Togashi, Shigeko


    Sr isotope ratios are analyzed for voluminous acidic pyroclastics erupted at 1 - 3 Ma in five areas on the volcanic front of Northeast Japan. The initial values of 87 Sr/ 86 Sr ratios range from 0.7040 to 0.7055. There is no significant difference in ratios between 1 - 3 Ma acidic pyroclastics and 0 - 1 Ma andesitic volcanics in each area in spite of differences in age and in mean SiO 2 content. On the other hand, the ratios in both of 1 - 3 Ma and 0 - 1 Ma volcanics vary along arc in the same manner. The changes of Sr and Rb contents in each area are consistent with systematic changes by fractional crystallization. The low 87 Sr/ 86 Sr ratios and chemistry suggest that 1 - 3 Ma acidic pyroclastics of Northeast Japan formed by a high degree of fractional crystallization from basic magma which is common in genesis with young andesitic volcanism. The mechanisms of the formation of the basic magma and the character of mantle source in each area have not changed for the past 3 Ma. Degrees of fractional crystallization changed with changes of the tectonic condition of shallow magma chamber from a weak horizontal compression stress field to a strong one. (author)

  13. Identification and characterization of novel NuMA isoforms

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Jin, E-mail: [Key Laboratory for Cell Proliferation and Regulation of the Ministry of Education, Beijing Normal University, Beijing (China); Xu, Zhe [Department of Clinical Laboratory Diagnosis, Beijing Tiantan Hospital, Capital Medical University, Beijing (China); Core Laboratory for Clinical Medical Research, Beijing Tiantan Hospital, Capital Medical University, Beijing (China); He, Dacheng [Key Laboratory for Cell Proliferation and Regulation of the Ministry of Education, Beijing Normal University, Beijing (China); Lu, Guanting, E-mail: [Beijing DnaLead Science and Technology Co., LTD, Beijing (China)


    Highlights: • Seven NuMA isoforms generated by alternative splicing were categorized into 3 groups: long, middle and short. • Both exons 15 and 16 in long NuMA were “hotspot” for alternative splicing. • Lower expression of short NuMA was observed in cancer cells compared with nonneoplastic controls. • Distinct localization pattern of short isoforms indicated different function from that of long and middle NuMA. - Abstract: The large nuclear mitotic apparatus (NuMA) has been investigated for over 30 years with functions related to the formation and maintenance of mitotic spindle poles during mitosis. However, the existence and functions of NuMA isoforms generated by alternative splicing remains unclear. In the present work, we show that at least seven NuMA isoforms (categorized into long, middle and short groups) generated by alternative splicing from a common NuMA mRNA precursor were discovered in HeLa cells and these isoforms differ mainly at the carboxyl terminus and the coiled-coil domains. Two “hotspot” exons with molecular mass of 3366-nt and 42-nt tend to be spliced during alternative splicing in long and middle groups. Furthermore, full-length coding sequences of long and middle NuMA obtained by using fusion PCR were constructed into GFP-tagged vector to illustrate their cellular localization. Long NuMA mainly localized in the nucleus with absence from nucleoli during interphase and translocated to the spindle poles in mitosis. Middle NuMA displayed the similar cell cycle-dependent distribution pattern as long NuMA. However, expression of NuMA short isoforms revealed a distinct subcellular localization. Short NuMA were present in the cytosol during the whole cycle, without colocalization with mitotic apparatus. These results have allowed us tentatively to explore a new research direction for NuMA’s various functions.

  14. Volcanic-plutonic connections and metal fertility of highly evolved magma systems: A case study from the Herberton Sn-W-Mo Mineral Field, Queensland, Australia (United States)

    Cheng, Yanbo; Spandler, Carl; Chang, Zhaoshan; Clarke, Gavin


    Understanding the connection between the highly evolved intrusive and extrusive systems is essential to explore the evolution of high silicic magma systems, which plays an important role in discussions of planetary differentiation, the growth of continents, crustal evolution, and the formation of highly evolved magma associated Sn-W-Mo mineral systems. To discern differences between "fertile" and "non-fertile" igneous rocks associated with Sn-W-Mo mineralization and reveal the genetic links between coeval intrusive and extrusive rocks, we integrate whole rock geochemistry, geochronology and Hf isotope signatures of igneous zircons from contemporaneous plutonic and volcanic rocks from the world-class Herberton Mineral Field of Queensland, Australia. The 310-300 Ma intrusive rocks and associated intra-plutonic W-Mo mineralization formed from relatively oxidized magmas after moderate degrees of crystal fractionation. The geochemical and isotopic features of the coeval volcanic succession are best reconciled utilizing the widely-accepted volcanic-plutonic connection model, whereby the volcanic rocks represent fractionated derivatives of the intrusive rocks. Older intrusions emplaced at 335-315 Ma formed from relatively low fO2 magmas that fractionated extensively to produce highly evolved granites that host Sn mineralization. Coeval volcanic rocks of this suite are compositionally less evolved than the intrusive rocks, thereby requiring a different model to link these plutonic-volcanic sequences. In this case, we propose that the most fractionated magmas were not lost to volcanism, but instead were effectively retained at the plutonic level, which allowed further localized build-up of volatiles and lithophile metals in the plutonic environment. This disconnection to the volcanism and degassing may be a crucial step for forming granite-hosted Sn mineralization. The transition between these two igneous regimes in Herberton region over a ∼30 m.y. period is attributed to

  15. Petrogenesis of volcanic rocks that host the world-class Agsbnd Pb Navidad District, North Patagonian Massif: Comparison with the Jurassic Chon Aike Volcanic Province of Patagonia, Argentina (United States)

    Bouhier, Verónica E.; Franchini, Marta B.; Caffe, Pablo J.; Maydagán, Laura; Rapela, Carlos W.; Paolini, Marcelo


    We present the first study of the volcanic rocks of the Cañadón Asfalto Formation that host the Navidad world-class Ag + Pb epithermal district located in the North Patagonian Massif, Patagonia, Argentina. These volcanic and sedimentary rocks were deposited in a lacustrine environment during an extensional tectonic regime associated with the breakup of Gondwana and represent the mafic to intermediate counterparts of the mainly silicic Jurassic Chon Aike Volcanic Province. Lava flows surrounded by autobrecciated carapace were extruded in subaerial conditions, whereas hyaloclastite and peperite facies suggest contemporaneous subaqueous volcanism and sedimentation. LA-ICPMS Usbnd Pb ages of zircon crystals from the volcanic units yielded Middle Jurassic ages of 173.9 ± 1.9 Ma and 170.8 ± 3 Ma. In the Navidad district, volcanic rocks of the Cañadón Asfalto Formation show arc-like signatures including high-K basaltic-andesite to high-K dacite compositions, Rb, Ba and Th enrichment relative to the less mobile HFS elements (Nb, Ta), enrichment in light rare earth elements (LREE), Ysbnd Ti depletion, and high Zr contents. These characteristics could be explained by assimilation of crustal rocks in the Jurassic magmas, which is also supported by the presence of zircon xenocrysts with Permian and Middle-Upper Triassic ages (281.3 Ma, 246.5, 218.1, and 201.3 Ma) and quartz xenocrysts recognized in these volcanic units. Furthermore, Sr and Nd isotope compositions suggest a contribution of crustal components in these Middle Jurassic magmas. High-K basaltic andesite has initial 87Sr/86Sr ratios of 0.70416-0.70658 and ξNd(t) values of -5.3 and -4. High-K dacite and andesite have initial 87Sr/86Sr compositions of 0.70584-0.70601 and ξNd(t) values of -4,1 and -3,2. The range of Pb isotope values (206Pb/204Pb = 18.28-18.37, 207Pb/204Pb = 15.61-15.62, and 208Pb/204Pb = 38.26-38.43) of Navidad volcanic rocks and ore minerals suggest mixing Pb sources with contributions of

  16. Stratigraphical sequence and geochronology of the volcanic rock series in caifang basin, south jiangxi

    International Nuclear Information System (INIS)

    Xu Xunsheng; Wu Jianhua


    The late Mesozoic volcanic rocks in Jiangxi constitute two volcanic belts: the northern is Xiajiang-Guangfeng volcanic belt, the volcanic rocks series belong to one volcano cycle and named Wuyi group which is subdivided into three formations (Shuangfengling formation, Ehuling formation and Shixi formation); the southern is Sannan-Xunwu volcanic belt, the volcanic rocks series in Caifang basin which locates on Sannan-Xunwu volcanic belt also belong to only one volcano cycle. It can be subdivided into two lithology and lithofacies units (upper and lower): the lower unit consists of sedimentary rocks and associated with a subordinate amount of volcanic rocks, it belongs to erupt-deposit facies which is the product of early volcanic stage; the upper unit is mostly composed of volcanic rocks, it belongs to erupt facies that is the volcanic eruption product. SHRIMP zircon U-Pb age of rhyolite? which locates at the top of the upper unit is 130.79 ± 0.73) Ma. According to the new International Stratigraphic Chart, the boundary of Jurassic and Cretaceous is (145.4 ± 4.0) Ma, so the age shows that the geologic period of Caifang volcanic rocks series is early Early Cretaceous epoch. On the basis of lithological correlation, lithofacies and stratigraphic horizon analysis, the volcanic rock series in Caifang basin fall under Wuyi group, and the lower unit could be incorporated into Shuangfengling formation, the upper unit could be incorporated into Ehuling formation. The subdivision of sequence and the determination of geochronology of the volcanic rock series in Caifang basin provide some references for the study of the late Mesozoic volcanic rocks series of the Sannan-Xunwu volcanic belt. (authors)

  17. Volcanic stratigraphy: A review (United States)

    Martí, Joan; Groppelli, Gianluca; Brum da Silveira, Antonio


    Volcanic stratigraphy is a fundamental component of geological mapping in volcanic areas as it yields the basic criteria and essential data for identifying the spatial and temporal relationships between volcanic products and intra/inter-eruptive processes (earth-surface, tectonic and climatic), which in turn provides greater understanding of the geological evolution of a region. Establishing precise stratigraphic relationships in volcanic successions is not only essential for understanding the past behaviour of volcanoes and for predicting how they might behave in the future, but is also critical for establishing guidelines for exploring economic and energy resources associated with volcanic systems or for reconstructing the evolution of sedimentary basins in which volcanism has played a significant role. Like classical stratigraphy, volcanic stratigraphy should also be defined using a systematic methodology that can provide an organised and comprehensive description of the temporal and spatial evolution of volcanic terrain. This review explores different methods employed in studies of volcanic stratigraphy, examines four case studies that use differing stratigraphic approaches, and recommends methods for using systematic volcanic stratigraphy based on the application of the concepts of traditional stratigraphy but adapted to the needs of volcanological environment.

  18. Mount Etna-Iblean volcanism caused by rollback-induced upper mantle upwelling around the Ionian slab edge : An alternative to the plume model

    NARCIS (Netherlands)

    Schellart, W. P.

    Volcanism in Sicily (Italy) at Mount Etna (0.5 Ma to present) and the Iblean Plateau (ca. 7.0-1.1 Ma) remains enigmatic, because it is located in close proximity to, but is laterally offset from, the Calabrian subduction zone. Previous work suggests that the volcanism results from a plume or from

  19. Ma(d)skulinitet

    DEFF Research Database (Denmark)

    Leer, Jonatan

    Når tv-kokke som Jamie Oliver, Gordon Ramsay og brødrene Price toner frem på skærmen, laver de ikke kun mad. De mixer også maskulinitet. For når en mand laver mad, laver maden også manden. Det mener postdoc Jonatan Leer, der i Ma(ds)kulinitet. Kønskamp i tv-køkkenet præsenterer, hvordan og hvorfor...

  20. Volcanic crisis in

    Directory of Open Access Journals (Sweden)

    Mgs. Víctor Manuel Pérez Martínez


    Full Text Available The article is the result of an investigation which is focussed on some deontological aspects of the scientificjournalism. In the first place it gives a theoretical vision about science, journalism, internet and including some reflectionsabout the deontological principles in handling the information about science and technology. This focus is useful as it formsthe base of an investigation where we deal with the information about a possible ”volcanic crisis” in El Teide during the years2004-2005 done by the digital newspaper” El Dïa” a canarian newspaper from Tenerife. The work required the revision of theinformation which was published and a followed analysis of its context. It was used the digital version with the purpose ofvisualizing the news which was published. It was also compared with a printed version, with local cover but divulged theinformation to the public who was most affected by this particular news. The results give rise to some questions regardinghow the information is given to a topic which is of local interest as well as national and international interest due to therepercussions in the social, economical and tourist field (the tourist field is the main industrial sector in Tenerife by receivingthis type of news.

  1. Records of Triassic volcanism in Pangean Great Lakes, and implications for reconstructing the distal effects of Large Igneous Provinces (United States)

    Whiteside, J. H.; Percival, L.; Kinney, S.; Olsen, P. E.; Mather, T. A.; Philpotts, A.


    Documentation of the precise timing of volcanic eruptions in sedimentary records is key for linking volcanic activity to both historical and geological episodes of environmental change. Deposition of tuffs in sediments, and sedimentary enrichment of trace metals linked to igneous processes, are both commonly used for such correlations. In particular, sedimentary mercury (Hg) enrichments have been used as a marker for volcanic activity from Large Igneous Provinces (LIPs) to support their link to episodes of major climate change and mass extinction in the geological record. However, linking such enrichments to a specific eruption or eruption products is often challenging or impossible. In this study, the mercury records from two exactly contemporaneous latest Triassic-earliest Jurassic rift lakes are presented. Both sedimentary records feature igneous units proposed to be related to the later (Early Jurassic) stages of volcanism of the Central Atlantic Magmatic Province (CAMP). These CAMP units include a small tuff unit identified by thin-section petrology and identified at 10 localities over a distance of over 200 km, and a major CAMP basalt flow overlying this tuff (and dated at 200.916±0.064 Ma) which is also known across multiple sedimentary basins in both North America and Morocco and is thought to have been emplaced about 120 kyr after the tuff. A potential stratigraphic correlation between Hg enrichments and the igneous units is considered, and compared to the established records of mercury enrichments from the latest Triassic that are thought to be coeval with the earlier stages of CAMP volcanism. Investigating the Hg records of sedimentary successions containing tuffs and basalt units is an important step for demonstrating whether the mercury emissions from specific individual volcanic eruptions in the deep past can be identified in the geological record, and are thus important tools for interpreting the causes of associated past geological events, such as

  2. Timing and compositional evolution of Late Pleistocene to Holocene volcanism within the Harrat Rahat volcanic field, Kingdom of Saudi Arabia (United States)

    Stelten, M. E.; Downs, D. T.; Dietterich, H. R.


    Harrat Rahat is one of the largest ( 20,000 km2) of 15 active Cenozoic volcanic fields that stretch 3,000 km along the western Arabian Peninsula from Yemen to Syria. The Harrat Rahat volcanic field is 310 km long (N-S) by 75 km wide (E-W), and is dominated by alkalic basalts with minor hawaiite, mugearite, benmoreite, and trachyte eruptives. The timing of volcanism within greater Harrat Rahat is poorly constrained, but field relations and geochronology indicate that northern Harrat Rahat hosted the most recent eruptions. To better constrain the timing and compositional evolution of Harrat Rahat during this recent phase, we present 743 geochemical analyses, 144 40Ar/39Ar ages, and 9 36Cl exposure ages for volcanic strata from northernmost Harrat Rahat. These data demonstrate that volcanism has been ongoing from at least 1.2 Ma to the present, with the most recent eruption known from historical accounts at 1256 CE. Basalt has erupted persistently from 1.2 Ma to the present, but more evolved volcanism has been episodic. Benmoreite erupted at 1.1 Ma and between 550 to 400 ka. Trachytic volcanism has only occurred over the past 150 ka, with the most recent eruption at 5 ka. Aside from the well-documented basaltic eruption at 1256 CE, prior workers interpreted 6 additional basaltic eruptions during the Holocene. However, our 36Cl exposure ages demonstrate that these erupted between 60 to 13 ka. Interestingly, in the northern part of our field area, where the spatial density of volcanic vents is low, young volcanism (<150 ka) is dominated by basaltic eruptions. Conversely, young volcanism in the southern part of our field area, where volcanic vent density is high, is dominated by trachyte. This observation is consistent with a process wherein the time-integrated effects of basaltic influx into the crust in the south produced a mafic intrusive complex, through which younger basaltic magmas cannot ascend. Instead, these magmas stall and produce trachyte, likely through

  3. 129I in volcanic fluids: Testing for the presence of marine sediments in the Central American volcanic arc

    International Nuclear Information System (INIS)

    Snyder, Glen; Fehn, Udo


    The long half-life and the geochemical behavior of the 129 I system suggest that this cosmogenic radioisotope can contribute significantly to the understanding of processes associated with subduction zones and volcanic arc systems. Because iodine is not incorporated into igneous rocks, the age-signal associated with 129 I permits the determination of the origin of volatiles within arc volcanic systems. We report here results of a study to test the application of 129 I in fluids collected from hotsprings, crater lakes, fumaroles and geothermal wells from the Central American volcanic arc. Both the Momotombo geothermal field in Nicaragua and the Miravalles geothermal field in Costa Rica show 129 I/I ratios consistent with magmatic contributions from subducted marine pelagic sediments (minimum iodine ages of 25-30 Ma). In addition, several wells provide iodine isotopic ratios indicative of an older end-member, presumably located in the shallow crust (minimum iodine age = 65 Ma)

  4. Volcanism on Io (United States)

    Davies, Ashley Gerard


    Preface; Introduction; Part I. Io, 1610 to 1995: Galileo to Galileo: 1. Io, 1610-1979; 2. Between Voyager and Galileo: 1979-95; 3. Galileo at Io; Part II. Planetary Volcanism: Evolution and Composition: 4. Io and Earth: formation, evolution, and interior structure; 5. Magmas and volatiles; Part III. Observing and Modeling Volcanic Activity: 6. Observations: thermal remote sensing of volcanic activity; 7. Models of effusive eruption processes; 8. Thermal evolution of volcanic eruptions; Part IV. Galileo at Io: the Volcanic Bestiary: 9. The view from Galileo; 10. The lava lake at Pele; 11. Pillan and Tvashtar: lava fountains and flows; 12. Prometheus and Amirani: Effusive activity and insulated flows; 13. Loki Patera: Io's powerhouse; 14. Other volcanoes and eruptions; Part V. Volcanism on Io: The Global View: 15. Geomorphology: paterae, shields, flows and mountains; 16. Volcanic plumes; 17. Hot spots; Part VI. Io after Galileo: 18. Volcanism on Io: a post-Galileo view; 19. The future of Io observations; Appendix 1; Appendix 2; References; Index.

  5. Fission-track ages of Neogene and Quaternary volcanic ashes in south of Osaka, Japan

    International Nuclear Information System (INIS)

    Yokoyama, Takuo; Nakagawa, Yonosuke; Danhara, Tohru.


    A calculation method is proposed for the fission-track ages of zircon crystals in volcanic material. In this method, it is checked whether the spontaneous fission-track number of respective zircon crystals follows the Poisson distribution. If it does, the age is calculated by population method with all crystals, and if not, only with those crystals following the Poisson distribution, eliminating abnormal crystals. Extraneous zircon crystals are thus excluded and crystals with spontaneous fission-track number zero are not ignored. The following ages were obtained: Tamateyama volcanic ash in the Nijo group, 14.0 +- 0.6 Ma; pink volcanic ash in the Osaka group, 1.0 +- 0.2 Ma; Matsuo volcanic ash in the Ko-Osaka group, 1.5 +- 0.4 Ma; pumice volcanic ash in the Ko-Osaka group, 2.3 +- 0.4 Ma; Asashiro volcanic ash in the Ko-Osaka group, 2.9 +- 0.6 Ma. (Mori, K.)

  6. Central San Juan caldera cluster: Regional volcanic framework (United States)

    Lipman, Peter W.


    Eruption of at least 8800 km3 of dacitic-rhyolitic magma as 9 major ash-slow sheets (individually 150-5000 km3) was accompanied by recurrent caldera subsidence between 28.3 and about 26.5 Ma in the central San Juan Mountains, Colorado. Voluminous andesitic-decitic lavas and breccias were erupted from central volcanoes prior to the ash-flow eruptions, and similar lava eruptions continued within and adjacent to the calderas during the period of explosive volcanism, making the central San Juan caldera cluster an exceptional site for study of caldera-related volcanic processes. Exposed calderas vary in size from 10 to 75 km in maximum diameter, the largest calderas being associated with the most voluminous eruptions. After collapse of the giant La Garita caldera during eruption if the Fish Canyon Tuff at 17.6 Ma, seven additional explosive eruptions and calderas formed inside the La Garita depression within about 1 m.y. Because of the nested geometry, maximum loci of recurrently overlapping collapse events are inferred to have subsided as much as 10-17 km, far deeper than the roof of the composite subvolcanic batholith defined by gravity data, which represents solidified caldera-related magma bodies. Erosional dissection to depths of as much as 1.5 km, although insufficient to reach the subvolcanic batholith, has exposed diverse features of intracaldera ash-flow tuff and interleaved caldera-collapse landslide deposits that accumulated to multikilometer thickness within concurrently subsiding caldera structures. The calderas display a variety of postcollapse resurgent uplift structures, and caldera-forming events produced complex fault geometries that localized late mineralization, including the epithermal base- and precious-metal veins of the well-known Creede mining district. Most of the central San Juan calderas have been deeply eroded, and their identification is dependent on detailed geologic mapping. In contrast, the primary volcanic morphology of the

  7. Volcanic signals in oceans

    KAUST Repository

    Stenchikov, Georgiy L.


    Sulfate aerosols resulting from strong volcanic explosions last for 2–3 years in the lower stratosphere. Therefore it was traditionally believed that volcanic impacts produce mainly short-term, transient climate perturbations. However, the ocean integrates volcanic radiative cooling and responds over a wide range of time scales. The associated processes, especially ocean heat uptake, play a key role in ongoing climate change. However, they are not well constrained by observations, and attempts to simulate them in current climate models used for climate predictions yield a range of uncertainty. Volcanic impacts on the ocean provide an independent means of assessing these processes. This study focuses on quantification of the seasonal to multidecadal time scale response of the ocean to explosive volcanism. It employs the coupled climate model CM2.1, developed recently at the National Oceanic and Atmospheric Administration\\'s Geophysical Fluid Dynamics Laboratory, to simulate the response to the 1991 Pinatubo and the 1815 Tambora eruptions, which were the largest in the 20th and 19th centuries, respectively. The simulated climate perturbations compare well with available observations for the Pinatubo period. The stronger Tambora forcing produces responses with higher signal-to-noise ratio. Volcanic cooling tends to strengthen the Atlantic meridional overturning circulation. Sea ice extent appears to be sensitive to volcanic forcing, especially during the warm season. Because of the extremely long relaxation time of ocean subsurface temperature and sea level, the perturbations caused by the Tambora eruption could have lasted well into the 20th century.

  8. Holocene volcanic geology, volcanic hazard, and risk on Taveuni, Fiji

    International Nuclear Information System (INIS)

    Cronin, S.J.; Neall, V.E.


    The Holocene volcanic geology of Taveuni has been mapped in order to produce a volcanic hazard and risk assessment for the island. Taveuni is the third-largest island of the Fiji group and home to 14,500 people. At least cubic km 2.7 of olivine-alkali-basalt magma was erupted from over 100 events throughout the Holocene. Vents are concentrated along a northeast-striking rift zone that is parallel to other regional structural trends. There is an overall trend of younging southward along the rift. Holocene lavas and tephras are grouped within six newly defined eruptive periods, established on a basis of radiocarbon dating. Within these periods, 14 tephra layers, useful as local marker horizons, are recognised. At least 58% of Holocene eruptions produced lava flows, while almost all produced some tephra. Individual eruption event volumes ranged between 0.001 and cubic km 0.20 (dense rock equivalent). Many eruptions involved at least some phases of phreatic and/or phreato-magmatic activity, although dominant hydrovolcanic activity was limited to only a few events. A volcanic hazard map is presented, based on the Holocene geology map and statistical analyses of eruption recurrence. The highest levels of ground-based and near-vent hazards are concentrated along the southern portion of the island's rift axis, with the paths of initial lava flows predicted from present topography. Tephra fall hazards are based on eruption parameters interpreted from mapped Holocene tephra layers. Hawaiian explosive-style eruptions appear to be a dominant eruptive process, with prevailing low-level (<3 km) southeasterly winds dispersing most tephra to the northwestern quadrant. Vulnerable elements (population centres, infrastructure, and economy) on Taveuni have been considered in deriving a volcanic risk assessment for the island. A number of infrastructural and subdivision developments are either under way or planned for the island, driven by its highly fertile soils and availability of

  9. Volcanic Rocks and Features (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Volcanoes have contributed significantly to the formation of the surface of our planet. Volcanism produced the crust we live on and most of the air we breathe. The...

  10. Martian volcanism: A review

    International Nuclear Information System (INIS)

    Carr, M.H.


    Martian volcanism is reviewed. It is emphasized that lava plains constitute the major type of effusive flow, and can be differentiated by morphologic characteristics. Shield volcanoes, domes, and patera constitute the major constructional landforms, and recent work has suggested that explosive activity and resulting pyroclastic deposits may have been involved with formation of some of the small shields. Analysis of morphology, presumed composition, and spectroscopic data all indicate that Martian volcanism was dominantly basaltic in composition


    Directory of Open Access Journals (Sweden)

    George Pararas-Carayannis


    Full Text Available Earthquakes, volcanic eruptions, volcanic island flank failures and underwater slides have generated numerous destructive tsunamis in the Caribbean region. Convergent, compressional and collisional tectonic activity caused primarily from the eastward movement of the Caribbean Plate in relation to the North American, Atlantic and South American Plates, is responsible for zones of subduction in the region, the formation of island arcs and the evolution of particular volcanic centers on the overlying plate. The inter-plate tectonic interaction and deformation along these marginal boundaries result in moderate seismic and volcanic events that can generate tsunamis by a number of different mechanisms. The active geo-dynamic processes have created the Lesser Antilles, an arc of small islands with volcanoes characterized by both effusive and explosive activity. Eruption mechanisms of these Caribbean volcanoes are complex and often anomalous. Collapses of lava domes often precede major eruptions, which may vary in intensity from Strombolian to Plinian. Locally catastrophic, short-period tsunami-like waves can be generated directly by lateral, direct or channelized volcanic blast episodes, or in combination with collateral air pressure perturbations, nuéss ardentes, pyroclastic flows, lahars, or cascading debris avalanches. Submarine volcanic caldera collapses can also generate locally destructive tsunami waves. Volcanoes in the Eastern Caribbean Region have unstable flanks. Destructive local tsunamis may be generated from aerial and submarine volcanic edifice mass edifice flank failures, which may be triggered by volcanic episodes, lava dome collapses, or simply by gravitational instabilities. The present report evaluates volcanic mechanisms, resulting flank failure processes and their potential for tsunami generation. More specifically, the report evaluates recent volcanic eruption mechanisms of the Soufriere Hills volcano on Montserrat, of Mt. Pel

  12. Defining the Tristan-Gough Hotspot: High-Resolution 40Ar/39Ar Dating of Volcanism at Tristan da Cunha (United States)

    Schnur, S.; Koppers, A. A. P.


    Explaining the spatial distribution of intra-plate volcanism is an important geologic problem. The Walvis Ridge is a uniquely-shaped hotspot trail in the South Atlantic that is not fully explained by the prevailing mantle plume paradigm. About halfway through its 130 Myr history, Walvis shows a morphological shift from a continuous ridge to a diffuse region of guyots arranged in two volcanic tracks. Recent volcanism at both Tristan da Cunha and Gough Island suggests these tracks are produced by two hotspots sourced from a single plume. However, the islands are located more than 400 km apart, which does not conform to our understanding of plumes as narrow, semi-stationary upwellings. It remains unclear which of the two islands better represents the current plume position. New ages from previously unstudied seamounts show that Tristan is younger than surrounding volcanism, whereas Gough appears to fit the local age progression (Schnur et al. 2014). Modern radiometric ages suggest the main island of Tristan may have been active for up to 1.3 ± 0.2 Myr (O'Connor and le Roex 1992). However, the seemingly older Inaccessible, Nightingale and Middle islands have yet to be reliably dated and could be up to 18 ± 4 Ma based on K-Ar ages (Miller in Baker et al. 1964). In order to confidently delineate the duration of volcanism at Tristan, we present the results of 29 new 40Ar/39Ar step-heating experiments on biotite, hornblende, plagioclase and groundmass separates from rocks collected on Inaccessible, Nightingale and Middle islands. Our results show that volcanism on all three islands is young, in most cases interpretations of plume dynamics. These results also show that magma was being supplied simultaneously to both Tristan and Gough over recent geologic time. Two possible explanations for this are that (1) there is a broad plume underlying the area, with focus points at Tristan and Gough or (2) hotspot magma is being focused at Tristan due to the nearby fracture zone

  13. Millennium Ecosystem Assessment: MA Ecosystems (United States)

    National Aeronautics and Space Administration — The Millennium Ecosystem Assessment: MA Ecosystems provides data and information on the extent and classification of ecosystems circa 2000, including coastal,...

  14. Millennium Ecosystem Assessment: MA Biodiversity (United States)

    National Aeronautics and Space Administration — The Millennium Ecosystem Assessment: MA Biodiversity provides data and information on amphibians, disease agents (extent and distribution of infectious and parasitic...

  15. Miocene volcanism in the Oaş-Gutâi Volcanic Zone, Eastern Carpathians, Romania: Relationship to geodynamic processes in the Transcarpathian Basin (United States)

    Kovacs, Marinel; Seghedi, Ioan; Yamamoto, Masatsugu; Fülöp, Alexandrina; Pécskay, Zoltán; Jurje, Maria


    We present the first comprehensive study of Miocene volcanic rocks of the Oaş-Gutâi Volcanic Zone (OGVZ), Romania, which are exposed in the eastern Transcarpathian Basin (TB), within the Eastern Alpine-Western Carpathian-Northern Pannonian (ALCAPA) block. Collision between the ALCAPA block and Europe at 18-16 Ma produced the Carpathian fold-and-thrust belt. This was followed by clockwise rotation and an extensional regime forming core complexes of the separated TB fragment. Based on petrographic and geochemical data, including Srsbnd Nd isotopic compositions and Ksbnd Ar ages, we distinguish three types of volcanic activity in the OGVZ: (1) early Miocene felsic volcanism that produced caldera-related ignimbrites in the Gutâi Mountains (15.4-14.8 Ma); (2) widespread middle-late Miocene intermediate/andesitic volcanism (13.4-7.0 Ma); and (3) minor late Miocene andesitic/rhyolitic volcanism comprising the Oraşu Nou rhyolitic volcano and several andesitic-dacitic domes in the Oaş Mountains (11.3-9.5 Ma). We show that magma evolution in the OGVZ was controlled by assimilation-fractional crystallization and magma-mixing processes within an interconnected multi-level crustal magmatic reservoir. The evolution of volcanic activity within the OGVZ was controlled by the geodynamics of the Transcarpathian Basin. The early felsic and late intermediate Miocene magmas were emplaced in a post-collisional setting and were derived from a mantle source region that was modified by subduction components (dominantly sediment melts) and lower crust. The style of volcanism within the eastern TB system exhibits spatial variations, with andesitic composite volcanoes (Gutâi Mountains) observed at the margins, and isolated andesitic-rhyolitic monogenetic volcanoes (Oaş Mountains) in the center of the basin.

  16. Petrology and geochronology of metamorphosed volcanic rocks and a middle Cretaceous volcanic neck in the east-central Sierra Nevada, California. (United States)

    Kistler, R.W.; Swanson, S.E.


    Metamorphosed Mesozoic volcanic rocks from the E-central Sierra Nevada range in composition from basalt to rhyolite and have ages, based on whole rock Rb-Sr and U-Pb zircon dating, of about 237- 224, 185, 163, 134, and 100Ma. The major plutons of the batholith in this area are of Triassic (215-200Ma) and Cretaceous (94-80Ma) ages. Initial 87Sr/86Sr values for the metamorphosed volcanic rocks of the area are in the range from 0.7042 to 0.7058 and are generally different from the values for the surrounding batholithic rocks (0.7056-0.7066). A circular, zoned granitic pluton, with an outcrop area of 2.5km2, similar in appearance to a ring dike complex, was apparently a conduit for some or possibly all of the middle-Cretaceous metamorphosed volcanic rocks exposed about 5km to the S in the western part of the Ritter Range. Samples from the metamorphosed volcanic rocks and the pluton yield a Rb/Sr whole rock isochron age of 99.9+ or -2.2Ma with an intitial 87Sr/86Sr of 0.7048+ or -0.00001. Major element variation diagrams of the pluton and volcanic rocks define coincident compositional trends. The ages of volcanic events relative to the ages of the major intrusive epochs and the major element and isotopic compositions of the volcanic rocks relative to the major plutons indicate that the volcanic rocks are not simply or directly related to the major plutons in the Sierra Nevada. -from Authors

  17. Pucarilla-Cerro Tipillas volcanic complex: the oldest recognized caldera in the southeastern portion of central volcanic zone of Central Andes?

    Energy Technology Data Exchange (ETDEWEB)

    Guzman, Silvina; Petrinovic, Ivan [CONICET -IBIGEO. Museo de Cs. Naturales, Universidad de Salta, Mendoza 2 (4400), Salta (Argentina)], E-mail:


    We recognize the most eastern and oldest collapse caldera structure in the southern portion of the Central Volcanic Zone of the Andes. A description of Middle-Upper Miocene successions related to explosive- effusive events is presented. The location of this centre close to Cerro Galn Caldera attests a recurrence in the volcanism between 12 and 2 Ma in this portion of the Altiplano - Puna Plateau.

  18. Discovery and utilization of sorghum genes (Ma5/Ma6) (United States)

    Mullet, John E; Rooney, William L; Klein, Patricia E; Morishige, Daryl; Murphy, Rebecca; Brady, Jeff A


    Methods and composition for the production of non-flowering or late flowering sorghum hybrid. For example, in certain aspects methods for use of molecular markers that constitute the Ma5/Ma6 pathway to modulate photoperiod sensitivity are described. The invention allows the production of plants having improved productivity and biomass generation.

  19. The K-Ar ages and their stratigraphic interpretation of the Cheju Island volcanics, Korea

    International Nuclear Information System (INIS)

    Tamanyu, Shiroh


    K-Ar datings were performed on the 5 volcanic rock samples of the Cheju Island Korea. The results of these datings are as follows. Hallasan trachyte; 0.07±0.01 Ma, Paeknoktam Hawaiite; 0.47±0.07 Ma, Hallasan Hawaiite; 0.52±0.03 Ma, Sogwip'o Hawaiite; 0.55±0.04 Ma, P'yosonri Alkali Basalt; 0.31±0.04 Ma. Among them, only Paeknoktam Hawaiite seems to be grown older by the excess Argon. But, all other ages can be interpreted respectively as the essential ages of their eruptions. Based on these newly obtained age data and previously reported age data, the volcanism of this island can be roughly divided into three stages as follows. I stage; early Pleistocene basic-intermediate volcanism. II stage; middle Pleistocene basic volcanism. III stage; late Pleistocene-Holocene basic-intermediate volcanism. And also, the age of Sogwip'o Formation which is famous of bearing the index molluscan fossil; Turritella saishuensis Yokoyama, must be correlated to early Pleistocene. (author)

  20. Volcanic air pollution hazards in Hawaii (United States)

    Elias, Tamar; Sutton, A. Jeff


    Noxious sulfur dioxide gas and other air pollutants emitted from Kīlauea Volcano on the Island of Hawai‘i react with oxygen, atmospheric moisture, and sunlight to produce volcanic smog (vog) and acid rain. Vog can negatively affect human health and agriculture, and acid rain can contaminate household water supplies by leaching metals from building and plumbing materials in rooftop rainwater-catchment systems. U.S. Geological Survey scientists, along with health professionals and local government officials are working together to better understand volcanic air pollution and to enhance public awareness of this hazard.

  1. Late Cretaceous sub-volcanic structure in the continental shelf off Portugal and its implications on tectonics and seismicity (United States)

    Neres, Marta; Terrinha, Pedro; Custódio, Susana; Noiva, João; Brito, Pedro; Santos, Joana; Carrilho, Fernando


    Long-lasting and widespread alkaline magmatism is recognized in the west Portuguese margin. Offshore, several volcanic seamounts punctuate the Tore-Madeira Rise and the Estremadura Spur, with known ages between 80 and 100 Ma. Onshore, the major events are the Monchique (69-73 Ma), Sines (75-77 Ma) and Sintra (75-82 Ma) plutons - whose location (aligned along 200 km) and age discrepancy inspired some geodynamic models for Iberia during the Cretaceous - and the Lisbon Volcanic Complex (90-100 Ma). Structural links between them have been proposed but no direct evidence was yet found for it. In this work we present new magnetic data from recent marine magnetic surveys (ROCHEL and MINEPLAT project) conducted off the west Portuguese coast on the continental shelf and slope. A total area of about 3000 km2 between Sintra and Sines was surveyed with line spacing of 1 mile. Very high-resolution multi-channel seismic profiles were simultaneously acquired with the magnetics covering an area of 400 km2 off Sines. Two main primary outcomes arise from these data. On one hand, higher-resolution mapping in regions where magnetic anomalies were already known allows a better understanding of the buried sub-volcanic system. On the other hand, previously unknown NNW-SSE aligned magnetic anomalies were identified along the coast off Sines, possibly corresponding to buried Late Cretaceous alkaline magmatic intrusives. The presence of magmatic bodies was up to now unknown in this region, and these findings reignite the discussion about a structural link connecting the three main on land intrusive complexes, Sintra, Sines and Monchique. In addition to the structural control of the magmatic complexes, seismicity is also an issue as a cluster of seismicity coincident with the Monchique complex has long been known. Smaller clusters coincide with the magnetic anomalies mapped during the ROCHEL and MINEPLAT surveys, as well. We interpret these results in the light of the tectono-magmatism of

  2. Magmatic evolution of Panama Canal volcanic rocks: A record of arc processes and tectonic change.

    Directory of Open Access Journals (Sweden)

    David W Farris

    Full Text Available Volcanic rocks along the Panama Canal present a world-class opportunity to examine the relationship between arc magmatism, tectonic forcing, wet and dry magmas, and volcanic structures. Major and trace element geochemistry of Canal volcanic rocks indicate a significant petrologic transition at 21-25 Ma. Oligocene Bas Obispo Fm. rocks have large negative Nb-Ta anomalies, low HREE, fluid mobile element enrichments, a THI of 0.88, and a H2Ocalc of >3 wt. %. In contrast, the Miocene Pedro Miguel and Late Basalt Fm. exhibit reduced Nb-Ta anomalies, flattened REE curves, depleted fluid mobile elements, a THI of 1.45, a H2Ocalc of <1 wt. %, and plot in mid-ocean ridge/back-arc basin fields. Geochemical modeling of Miocene rocks indicates 0.5-0.1 kbar crystallization depths of hot (1100-1190°C magmas in which most compositional diversity can be explained by fractional crystallization (F = 0.5. However, the most silicic lavas (Las Cascadas Fm. require an additional mechanism, and assimilation-fractional-crystallization can reproduce observed compositions at reasonable melt fractions. The Canal volcanic rocks, therefore, change from hydrous basaltic pyroclastic deposits typical of mantle-wedge-derived magmas, to hot, dry bi-modal magmatism at the Oligocene-Miocene boundary. We suggest the primary reason for the change is onset of arc perpendicular extension localized to central Panama. High-resolution mapping along the Panama Canal has revealed a sequence of inward dipping maar-diatreme pyroclastic pipes, large basaltic sills, and bedded silicic ignimbrites and tuff deposits. These volcanic bodies intrude into the sedimentary Canal Basin and are cut by normal and subsequently strike-slip faults. Such pyroclastic pipes and basaltic sills are most common in extensional arc and large igneous province environments. Overall, the change in volcanic edifice form and geochemistry are related to onset of arc perpendicular extension, and are consistent with the

  3. Magmatic evolution of Panama Canal volcanic rocks: A record of arc processes and tectonic change (United States)

    Cardona, Agustin; Montes, Camilo; Foster, David; Jaramillo, Carlos


    Volcanic rocks along the Panama Canal present a world-class opportunity to examine the relationship between arc magmatism, tectonic forcing, wet and dry magmas, and volcanic structures. Major and trace element geochemistry of Canal volcanic rocks indicate a significant petrologic transition at 21–25 Ma. Oligocene Bas Obispo Fm. rocks have large negative Nb-Ta anomalies, low HREE, fluid mobile element enrichments, a THI of 0.88, and a H2Ocalc of >3 wt. %. In contrast, the Miocene Pedro Miguel and Late Basalt Fm. exhibit reduced Nb-Ta anomalies, flattened REE curves, depleted fluid mobile elements, a THI of 1.45, a H2Ocalc of arc basin fields. Geochemical modeling of Miocene rocks indicates 0.5–0.1 kbar crystallization depths of hot (1100–1190°C) magmas in which most compositional diversity can be explained by fractional crystallization (F = 0.5). However, the most silicic lavas (Las Cascadas Fm.) require an additional mechanism, and assimilation-fractional-crystallization can reproduce observed compositions at reasonable melt fractions. The Canal volcanic rocks, therefore, change from hydrous basaltic pyroclastic deposits typical of mantle-wedge-derived magmas, to hot, dry bi-modal magmatism at the Oligocene-Miocene boundary. We suggest the primary reason for the change is onset of arc perpendicular extension localized to central Panama. High-resolution mapping along the Panama Canal has revealed a sequence of inward dipping maar-diatreme pyroclastic pipes, large basaltic sills, and bedded silicic ignimbrites and tuff deposits. These volcanic bodies intrude into the sedimentary Canal Basin and are cut by normal and subsequently strike-slip faults. Such pyroclastic pipes and basaltic sills are most common in extensional arc and large igneous province environments. Overall, the change in volcanic edifice form and geochemistry are related to onset of arc perpendicular extension, and are consistent with the idea that Panama arc crust fractured during collision

  4. Geology and zircon fission track ages of volcanic rocks in the western part of Hoshino gold area, Fukuoka Prefecture, Japan

    Energy Technology Data Exchange (ETDEWEB)

    Belhadi, Ahmed; Himeno, Osamu; Watanabe, Koichiro; Izawa, Eiji [Kyushu Univ., Fukuoka (Japan). Faculty of Engineering


    The Hoshino gold area is located in the western part of the Hohi volcanic zone, northern Kyushu. Volcanic rocks in this area vary from andesitic rocks in the north to dacite and rhyolite in the South. The basement is constituted by metamorphic rocks of pre-Cretaceous age. The volcanic rocks of Pliocene age were subdivided into eight volcanic units. Seven fission track ages of zircons from five volcanic units have been determined, using the external detector method. The age data obtained, combined with some previously reported ages, show that two main volcanic activities have occurred in the area. The first volcanic activity took place around 4.3 Ma, and resulted into the deposition of the Hoshino Andesite and the Ikenoyama Conglomerate. The second main volcanism started around 3.5 Ma, and was characterized by the eruption of the Shakadake Andesite and the Reiganji Andesite at the early stage, then, by more acidic rocks of the Takeyama Andesite, the Hyugami Dacite and the Kuroki Rhyolite at the later stage. The main volcanism in the area ceased around 2.6 Ma. (author)

  5. New geologic evidence for additional 16.5-15.5 Ma silicic calderas in northwest Nevada related to initial impingement of the Yellowstone hot spot

    International Nuclear Information System (INIS)

    Coble, Matthew A; Mahood, Gail A


    Three silicic calderas have been newly identified in northwest Nevada west of McDermitt caldera. This volcanism is interpreted to have formed during a short interval at 16.5-15.5 Ma, during the waning stage of Steens flood basalt volcanism after the initial impingement of the Yellowstone hot spot. New mapping demonstrates that the area affected by this mid-Miocene silicic volcanism is significantly larger than previously appreciated in the western U.S.

  6. New geologic evidence for additional 16.5-15.5 Ma silicic calderas in northwest Nevada related to initial impingement of the Yellowstone hot spot

    Energy Technology Data Exchange (ETDEWEB)

    Coble, Matthew A; Mahood, Gail A [Department Geological and Environmental Sciences, 450 Serra Mall, Bldg 320, Stanford University, Stanford, CA 94305-3115 (United States)


    Three silicic calderas have been newly identified in northwest Nevada west of McDermitt caldera. This volcanism is interpreted to have formed during a short interval at 16.5-15.5 Ma, during the waning stage of Steens flood basalt volcanism after the initial impingement of the Yellowstone hot spot. New mapping demonstrates that the area affected by this mid-Miocene silicic volcanism is significantly larger than previously appreciated in the western U.S.

  7. 40Ar/39Ar ages of the post-collision volcanic rocks and their geological significance in Yangyingxiang area, south Tibet

    International Nuclear Information System (INIS)

    Zhou Su; Mo Xuanxue; Zhao Zhidan; Zhang Shuangquan; Guo Tieying; Qiu Ruizhao


    Ten new 40 Ar/ 39 Ar age determination of mineral separates have been carried out to date volcanic rocks of Yangyingxiang in the eastern part of the Gangdese, Tibet. The age range of Sanidine and biotite in the five volcanic rock samples from the Yangyingxiang is 10.68 ± 0.05 - 11.42 ± 0.09 Ma. These results, combining with the previously published data, confirmed that Neogene post-collision volcanic rocks in the Gangdese widely occurred and their ages were getting younger eastwards. These volcanic rocks are different from those in Pana Formation of Linzizhong group (52.9 ± 2 Ma) outside Yangyingxiang geothermal field. (authors)

  8. Ma-rc-h

    Indian Academy of Sciences (India)

    Stone has been used in building construction in India since ancient times since it is durable and locally available. There are huge numbers of stone buildings in the country, ranging from rural houses to royal palaces and temples. In a typical rural stone house, there are thick stone masonry walls (thickness ranges from 600 ...

  9. Stratigraphy and eruption age of the volcanic rocks in the west of Miyanoharu area, Kumamoto Prefecture

    International Nuclear Information System (INIS)

    Kamata, Hiroki


    The detailed stratigraphic survey, K-Ar age determinations and NRM measurements of the volcanic rocks in the west of Miyanoharu area revealed the volcanic history as follows: Hornblende andesite lava with plagioclase megacryst (Yoshinomoto lava) erupted during 2.8 - 2.5 Ma (Gauss normal epoch), accompanied by small amount of pyroclastic materials. After this eruption, Kamitarumizu hypersthene-augite andesite lava (1.7 - 1.3 Ma; reversed), Yabakei pyroclastic flow (0.99 Ma; Jaramillo normal event), Yamakogawa biotite rhyolite lava (0.9 Ma; reversed) and Daikanbo hypersthene-augite andesite lava (0.8 Ma; normal) erupted successively prior to the Aso-1 pyroclastic flow (0.3 - 0.4 Ma). Both the K-Ar ages and NRM data are consistent with the stratigraphic sequence (Fig. 2), which suggests that the activity of andesite and rhyolite is intercalated with each other during Pleistocene in the studied area. The compiled radiometric age data in the central-north Kyushu show that the age of volcanic activity that has previously been inferred as middle Miocene is of Pliocene, and its distribution is limited within the quadrilateral (60 km x 40 km) where the pre-Tertiary basement rocks are absent. The distribution of volcanic rocks is historically zonated such that the rocks of older age up to 5 Ma develop toward the outer rim of the quadrilateral, which coincides with the 0 mgal contour bordering the large low Bouguer anomaly. These facts suggest that the volcanic activity is remarkably relevant to the subsidence of this area, where the volcano-tectonic depression has been formed after 5 Ma to the present, and filled with lavas and pyroclastic materials with scarce sedimentary rocks in the tension stress field during Plio-Pleistocene age. (Kubozono, M.)

  10. Heterogeneity in Subducting Slab Influences Fluid Properties, Plate Coupling and Volcanism: Hikurangi Subduction Zone, New Zealand (United States)

    Eberhart-Phillips, D. M.; Reyners, M.; Bannister, S. C.


    Seismicity distribution and 3-D models of P- and S-attenuation (1/Q) in the Hikurangi subduction zone, in the North Island of New Zealand, show large variation along-arc in the fluid properties of the subducting slab. Volcanism is also non-uniform, with extremely productive rhyolitic volcanism localized to the central Taupo Volcanic zone, and subduction without volcanism in the southern North Island. Plate coupling varies with heterogeneous slip deficit in the northern section, low slip deficit in the central section, and high slip deficit (strong coupling) in the south. Heterogeneous initial hydration and varied dehydration history both are inferred to play roles. The Hikurangi Plateau (large igneous province) has been subducted beneath New Zealand twice - firstly at ca. 105-100 Ma during north-south convergence with Gondwana, and currently during east-west convergence between the Pacific and Australian plates along the Hikurangi subduction zone. It has an uneven downdip edge which has produced spatially and temporally localized stalls in subduction rate. The mantle wedge under the rhyolitic section has a very low Q feature centred at 50-125 km depth, which directly overlies a 150-km long zone of dense seismicity. This seismicity occurs below a sharp transition in the downdip extent of the Hikurangi Plateau, where difficulty subducting the buoyant plateau would have created a zone of increased faulting and hydration that spent a longer time in the outer-rise yielding zone, compared with areas to the north and south. At shallow depths this section has unusually high fracture permeability from the two episodes of bending, but it did not experience dehydration during Gondwana subduction. This central section at plate interface depths less than 50-km has low Q in the slab crust, showing that it is extremely fluid rich, and it exhibits weak plate coupling with both deep and shallow slow-slip events. In contrast in the southern section, where there is a large deficit in

  11. Thermal vesiculation during volcanic eruptions. (United States)

    Lavallée, Yan; Dingwell, Donald B; Johnson, Jeffrey B; Cimarelli, Corrado; Hornby, Adrian J; Kendrick, Jackie E; von Aulock, Felix W; Kennedy, Ben M; Andrews, Benjamin J; Wadsworth, Fabian B; Rhodes, Emma; Chigna, Gustavo


    Terrestrial volcanic eruptions are the consequence of magmas ascending to the surface of the Earth. This ascent is driven by buoyancy forces, which are enhanced by bubble nucleation and growth (vesiculation) that reduce the density of magma. The development of vesicularity also greatly reduces the 'strength' of magma, a material parameter controlling fragmentation and thus the explosive potential of the liquid rock. The development of vesicularity in magmas has until now been viewed (both thermodynamically and kinetically) in terms of the pressure dependence of the solubility of water in the magma, and its role in driving gas saturation, exsolution and expansion during decompression. In contrast, the possible effects of the well documented negative temperature dependence of solubility of water in magma has largely been ignored. Recently, petrological constraints have demonstrated that considerable heating of magma may indeed be a common result of the latent heat of crystallization as well as viscous and frictional heating in areas of strain localization. Here we present field and experimental observations of magma vesiculation and fragmentation resulting from heating (rather than decompression). Textural analysis of volcanic ash from Santiaguito volcano in Guatemala reveals the presence of chemically heterogeneous filaments hosting micrometre-scale vesicles. The textures mirror those developed by disequilibrium melting induced via rapid heating during fault friction experiments, demonstrating that friction can generate sufficient heat to induce melting and vesiculation of hydrated silicic magma. Consideration of the experimentally determined temperature and pressure dependence of water solubility in magma reveals that, for many ascent paths, exsolution may be more efficiently achieved by heating than by decompression. We conclude that the thermal path experienced by magma during ascent strongly controls degassing, vesiculation, magma strength and the effusive

  12. local

    Directory of Open Access Journals (Sweden)

    Abílio Amiguinho


    Full Text Available The process of socio-educational territorialisation in rural contexts is the topic of this text. The theme corresponds to a challenge to address it having as main axis of discussion either the problem of social exclusion or that of local development. The reasons to locate the discussion in this last field of analysis are discussed in the first part of the text. Theoretical and political reasons are there articulated because the question is about projects whose intentions and practices call for the political both in the theoretical debate and in the choices that anticipate intervention. From research conducted for several years, I use contributions that aim at discuss and enlighten how school can be a potential locus of local development. Its identification and recognition as local institution (either because of those that work and live in it or because of those that act in the surrounding context are crucial steps to progressively constitute school as a partner for development. The promotion of the local values and roots, the reconstruction of socio-personal and local identities, the production of sociabilities and the equation and solution of shared problems were the dimensions of a socio-educative intervention, markedly globalising. This scenario, as it is argued, was also, intentionally, one of transformation and of deliberate change of school and of the administration of the educative territoires.

  13. Volcanic sulfur dioxide index and volcanic explosivity index inferred from eruptive volume of volcanoes in Jeju Island, Korea: application to volcanic hazard mitigation (United States)

    Ko, Bokyun; Yun, Sung-Hyo


    Jeju Island located in the southwestern part of Korea Peninsula is a volcanic island composed of lavaflows, pyroclasts, and around 450 monogenetic volcanoes. The volcanic activity of the island commenced with phreatomagmatic eruptions under subaqueous condition ca. 1.8-2.0 Ma and lasted until ca. 1,000 year BP. For evaluating volcanic activity of the most recently erupted volcanoes with reported age, volcanic explosivity index (VEI) and volcanic sulfur dioxide index (VSI) of three volcanoes (Ilchulbong tuff cone, Songaksan tuff ring, and Biyangdo scoria cone) are inferred from their eruptive volumes. The quantity of eruptive materials such as tuff, lavaflow, scoria, and so on, is calculated using a model developed in Auckland Volcanic Field which has similar volcanic setting to the island. The eruptive volumes of them are 11,911,534 m3, 24,987,557 m3, and 9,652,025 m3, which correspond to VEI of 3, 3, and 2, respectively. According to the correlation between VEI and VSI, the average quantity of SO2 emission during an eruption with VEI of 3 is 2-8 × 103 kiloton considering that the island was formed under intraplate tectonic setting. Jeju Island was regarded as an extinct volcano, however, several studies have recently reported some volcanic eruption ages within 10,000 year BP owing to the development in age dating technique. Thus, the island is a dormant volcano potentially implying high probability to erupt again in the future. The volcanoes might have explosive eruptions (vulcanian to plinian) with the possibility that SO2 emitted by the eruption reaches stratosphere causing climate change due to backscattering incoming solar radiation, increase in cloud reflectivity, etc. Consequently, recommencement of volcanic eruption in the island is able to result in serious volcanic hazard and this study provides fundamental and important data for volcanic hazard mitigation of East Asia as well as the island. ACKNOWLEDGMENTS: This research was supported by a grant [MPSS

  14. Volcanism Studies: Final Report for the Yucca Mountain Project

    Energy Technology Data Exchange (ETDEWEB)

    Bruce M. Crowe; Frank V. Perry; Greg A. Valentine; Lynn M. Bowker


    This report synthesizes the results of volcanism studies conducted by scientists at the Los Alamos National Laboratory and collaborating institutions on behalf of the Department of Energy's Yucca Mountain Project. An assessment of the risk of future volcanic activity is one of many site characterization studies that must be completed to evaluate the Yucca Mountain site for potential long-term storage of high-level radioactive waste. The presence of several basaltic volcanic centers in the Yucca Mountain region of Pliocene and Quaternary age indicates that there is a finite risk of a future volcanic event occurring during the 10,000-year isolation period of a potential repository. Chapter 1 introduces the volcanism issue for the Yucca Mountain site and provides the reader with an overview of the organization, content, and significant conclusions of this report. The risk of future basaltic volcanism is the primary topic of concern including both events that intersect a potential repository and events that occur near or within the waste isolation system of a repository. Future volcanic events cannot be predicted with certainty but instead are estimated using formal methods of probabilistic volcanic hazard assessment (PVHA). Chapter 2 describes the volcanic history of the Yucca Mountain region (YMR) and emphasizes the Pliocene and Quaternary volcanic record, the interval of primary concern for volcanic risk assessment. The distribution, eruptive history, and geochronology of Plio-Quaternary basalt centers are described by individual center emphasizing the younger postcaldera basalt (<5 Ma). The Lathrop Wells volcanic center is described in detail because it is the youngest basalt center in the YMR. The age of the Lathrop Wells center is now confidently determined to be about 75 thousand years old. Chapter 3 describes the tectonic setting of the YMR and presents and assesses the significance of multiple alternative tectonic models. The Crater Flat volcanic zone is

  15. Indirect Climatic Effects of Major Volcanic Eruptions (United States)

    Hofmann, D. J.


    The direct effects on climate, related to atmospheric emissions to the atmosphere following major volcanic eruptions, are well-known although the sparseness of such eruptions make detailed study on the range of such variations difficult. In general terms, infrared absorption by volcanic emissions to the stratosphere result in local heating early in the event when gaseous sulfur compounds exist. This early period is followed by gas to particle conversion, on a time scale of 1-2 months, promoting the formation of sulfuric acid-water droplets. Coagulation and droplet growth result in the "volcanic stratospheric aerosol layer" which is related to the predominant direct climatic effect of large eruptions, the cooling of the troposphere by backscattering of solar visible radiation to space with a recovery time scale of 1-2 years. In this paper we will discuss some of the less-known "indirect" effects of the volcanic stratospheric aerosol on climate. We label them indirect as they act on climate through intermediary atmospheric constituents. The intermediaries in the volcanic indirect climatic effect are generally atmospheric greenhouse gases or other atmospheric gases and conditions which affect greenhouse gases. For example, cooling of the troposphere following major eruptions reduces the growth rate of atmospheric carbon dioxide related to respiration by the terrestrial biosphere. In addition, redirection of part of the direct solar beam into diffuse radiation by the volcanic stratospheric aerosol stimulates plant photosynthesis, further reducing the carbon dioxide growth rate. The growth rate of the second-most important atmospheric greenhouse gas, methane, is also affected by volcanic emissions. Volcanic stratospheric aerosol particles provide surface area which catalyzes heterogeneous chemical reactions thus stimulating removal of stratospheric ozone, also a greenhouse gas. Although major droughts usually related to ENSO events have opposite effects on carbon

  16. Millennium Ecosystem Assessment: MA Population (United States)

    National Aeronautics and Space Administration — The Millennium Ecosystem Assessment: MA Population data sets provide baseline population information as one of the drivers of ecosystem change. The data helped in...

  17. Modeling volcanic ash dispersal

    CERN Multimedia

    CERN. Geneva


    The assessment of volcanic fallout hazard is an important scientific, economic, and political issue, especially in densely populated areas. From a scientific point of view, considerable progress has been made during the last two decades through the use of increasingly powerful computational models and capabilities. Nowadays, models are used to quantify hazard...

  18. Recurrence Rate and Magma Effusion Rate for the Latest Volcanism on Arsia Mons, Mars (United States)

    Richardson, Jacob A.; Wilson, James A.; Connor, Charles B.; Bleacher, Jacob E.; Kiyosugi, Koji


    Magmatism and volcanism have evolved the Martian lithosphere, surface, and climate throughout the history of Mars. Constraining the rates of magma generation and timing of volcanism on the surface clarifies the ways in which magma and volcanic activity have shaped these Martian systems. The ages of lava flows on other planets are often estimated using impact crater counts, assuming that the number and size-distribution of impact craters per unit area reflect the time the lava flow has been on the surface and exposed to potential impacts. Here we show that impact crater age model uncertainty is reduced by adding stratigraphic information observed at locations where neighboring lavas abut each other, and demonstrate the significance of this reduction in age uncertainty for understanding the history of a volcanic field comprising 29 vents in the 110-kilometer-diameter caldera of Arsia Mons, Mars. Each vent within this caldera produced lava flows several to tens of kilometers in length; these vents are likely among the youngest on Mars, since no impact craters in their lava flows are larger than 1 kilometer in diameter. First, we modeled the age of each vent with impact crater counts performed on their corresponding lava flows and found very large age uncertainties for the ages of individual vents, often spanning the estimated age for the entire volcanic field. The age model derived from impact crater counts alone is broad and unimodal, with estimated peak activity in the field around 130Ma (megaannum, 1 million years). Next we applied our volcano event age model (VEAM), which uses a directed graph of stratigraphic relationships and random sampling of the impact crater age determinations to create alternative age models. Monte Carlo simulation was used to create 10,000 possible vent age sets. The recurrence rate of volcanism is calculated for each possible age set, and these rates are combined to calculate the median recurrence rate of all simulations. Applying this

  19. MaNGA: Mapping Nearby Galaxies at Apache Point Observatory (United States)

    Weijmans, A.-M.; MaNGA Team


    MaNGA (Mapping Nearby Galaxies at APO) is a galaxy integral-field spectroscopic survey within the fourth generation Sloan Digital Sky Survey (SDSS-IV). It will be mapping the composition and kinematics of gas and stars in 10,000 nearby galaxies, using 17 differently sized fiber bundles. MaNGA's goal is to provide new insights in galaxy formation and evolution, and to deliver a local benchmark for current and future high-redshift studies.

  20. K-Ar chronological study of the quaternary volcanic activity in Shin-etsu Highland

    International Nuclear Information System (INIS)

    Kaneko, Takayuki; Shimizu, Satoshi; Itaya, Tetsumaru.


    In order to clarify the temporal and spatial patterns in arc volcanism, 55 K-Ar ages of volcanic rocks from 17 volcanoes in Shin-etsu Highland, central Japan were determined. In addition, life spans, volume of erupted materials and eruption rates of each volcano were estimated. Graphical analysis demonstrates that volume of ejecta varies proportionately with both life span and eruption rate, and that there is no significant correlation between eruption rate and distance from the volcanic front. The life span of each volcano in this Highland is less than 0.6 m.y. In the central Shiga and southern Asama area, the volcanism started at 1 Ma and is still active. However the former had a peak in the activity at around 0.5 Ma, while the latter is apparently most intense at present. Northern Kenashi area has the volcanism without peak in 1.7 - 0.2 Ma, though the activity within a volcanic cluster or chain in central Japan lasts generally for 1 m.y. or less with a peak. (author)

  1. Volcanic ash in ancient Maya ceramics of the limestone lowlands: implications for prehistoric volcanic activity in the Guatemala highlands (United States)

    Ford, Anabel; Rose, William I.


    In the spirit of collaborative research, Glicken and Ford embarked on the problem of identifying the source of volcanic ash used as temper in prehistoric Maya ceramics. Verification of the presence of glass shards and associated volcanic mineralogy in thin sections of Maya ceramics was straightforward and pointed to the Guatemala Highland volcanic chain. Considering seasonal wind rose patterns, target volcanoes include those from the area west of and including Guatemala City. Joint field research conducted in 1983 by Glicken and Ford in the limestone lowlands of Belize and neighboring Guatemala, 300 km north of the volcanic zone and 150 km from the nearest identified ash deposits, was unsuccessful in discovering local volcanic ash deposits. The abundance of the ash in common Maya ceramic vessels coupled with the difficulties of long-distance procurement without draft animals lead Glicken to suggest that ashfall into the lowlands would most parsimoniously explain prehistoric procurement; it literally dropped into their hands. A major archaeological problem with this explanation is that the use of volcanic ash occurring over several centuries of the Late Classic Period (ca. 600-900 AD). To accept the ashfall hypothesis for ancient Maya volcanic ash procurement, one would have to demonstrate a long span of consistent volcanic activity in the Guatemala Highlands for the last half of the first millennium AD. Should this be documented through careful petrographic, microprobe and tephrachronological studies, a number of related archaeological phenomena would be explained. In addition, the proposed model of volcanic activity has implications for understanding volcanism and potential volcanic hazards in Central America over a significantly longer time span than the historic period. These avenues are explored and a call for further collaborative research of this interdisciplinary problem is extended in this paper.

  2. Nd and Sr isotopes and K-Ar ages of the Ulreungdo alkali volcanic rocks in the East Sea, South Korea

    International Nuclear Information System (INIS)

    Kim Kyuhan; Jang Sunkyung; Tanaka, Tsuyoshi; Nagao, Keisuke


    Temporal geochemical and isotopical variations in the Ulreundgo alkali volcanic rocks provide important constraints on the origin and evolution of the volcanic rocks in relation to backarc basin tectonism. We determined the K-Ar ages, major and trace element contents, and Nd and Sr isotopic rations of the alkali volcanic rocks. The activities of Ulreungdo volcanoes can be divided, on the basis of radiometric ages and field occurrences, into five stages, though their activities range from 1.4 Ma to 0.01 Ma with short volcanic hiatus (ca. 0.05-0.3 Ma). The Nd-Sr isotopic data for Ulreungdo volcanic rocks enable us to conclude that: (1) the source materials of Ulreungdo volcanics are isotopically heterogeneous in composition, which is explained by the mixing of mantle derived magma and continental crustal source rocks. There is no systematic isotopic variations with eruption stages. Particularly, some volcanic rocks of stage 2 and 3 have extremely wide initial 87 Sr/ 86 Sr isotopic variations ranging from 0.7038 to 0.7092, which are influenced by seawater alterations; (2) the Ulreungdo volcanic rocks show EMI characteristic, while volcanic rocks from the Jejudo, Yeong-il and Jeon-gok areas have slightly depleted mantle source characteristics; (3) the trachyandesite of the latest eruption stage was originated from the mantle source materials which differ from other stages. A schematic isotopic evolution model for alkali basaltic magma is presented in the Ulreungdo volcanic island of the backarc basin of Japanese island arc system. (author)

  3. The Online GVP/USGS Weekly Volcanic Activity Report: Providing Timely Information About Worldwide Volcanism (United States)

    Mayberry, G. C.; Guffanti, M. C.; Luhr, J. F.; Venzke, E. A.; Wunderman, R. L.


    over 60 volcanoes, with an average of 10 volcanoes discussed each week. Notable volcanic activity during November 2000-November 2001 included an eruption beginning on 6 February at Nyamuragira in the Democratic Republic of the Congo; it issued low-viscosity lava flows that traveled towards inhabited towns, and also produced ash clouds that adversely effected the health of residents and livestock near the volcano. Eruptions at Mayon in the Philippines on 24 June and 25 July caused local authorities to raise the alert to the highest level, close area airports, and evacuate thousands of residents near the volcano. Most recently a large flank eruption at Etna in Italy began on 17 July and gained worldwide attention as extensive lava flows threatened a small town and a tourist complex. While the information found in the Weekly Volcanic Activity Report, ranging from large eruptions to small precursory events, is of interest to the general public, it has also proven to be a valuable resource to volcano observatory staff, universities, researchers, secondary schools, and the aviation community.

  4. Obsidian hydration dating of volcanic events (United States)

    Friedman, I.; Obradovich, J.


    Obsidian hydration dating of volcanic events had been compared with ages of the same events determined by the 14C and KAr methods at several localities. The localities, ranging in age from 1200 to over 1 million yr, include Newberry Craters, Oregon; Coso Hot Springs, California; Salton Sea, California; Yellowstone National Park, Wyoming; and Mineral Range, Utah. In most cases the agreement is quite good. A number of factors including volcanic glass composition and exposuretemperature history must be known in order to relate hydration thickness to age. The effect of composition can be determined from chemical analysis or the refractive index of the glass. Exposure-temperature history requires a number of considerations enumerated in this paper. ?? 1981.

  5. First results of the Piton de la Fournaise STRAP 2015 experiment: multidisciplinary tracking of a volcanic gas and aerosol plume (United States)

    Tulet, Pierre; Di Muro, Andréa; Colomb, Aurélie; Denjean, Cyrielle; Duflot, Valentin; Arellano, Santiago; Foucart, Brice; Brioude, Jérome; Sellegri, Karine; Peltier, Aline; Aiuppa, Alessandro; Barthe, Christelle; Bhugwant, Chatrapatty; Bielli, Soline; Boissier, Patrice; Boudoire, Guillaume; Bourrianne, Thierry; Brunet, Christophe; Burnet, Fréderic; Cammas, Jean-Pierre; Gabarrot, Franck; Galle, Bo; Giudice, Gaetano; Guadagno, Christian; Jeamblu, Fréderic; Kowalski, Philippe; Leclair de Bellevue, Jimmy; Marquestaut, Nicolas; Mékies, Dominique; Metzger, Jean-Marc; Pianezze, Joris; Portafaix, Thierry; Sciare, Jean; Tournigand, Arnaud; Villeneuve, Nicolas


    The STRAP (Synergie Transdisciplinaire pour Répondre aux Aléas liés aux Panaches volcaniques) campaign was conducted over the entire year of 2015 to investigate the volcanic plumes of Piton de La Fournaise (La Réunion, France). For the first time, measurements at the local (near the vent) and at the regional scales were conducted around the island. The STRAP 2015 campaign has become possible thanks to strong cross-disciplinary collaboration between volcanologists and meteorologists. The main observations during four eruptive periods (85 days) are summarised. They include the estimates of SO2, CO2 and H2O emissions, the altitude of the plume at the vent and over different areas of La Réunion Island, the evolution of the SO2 concentration, the aerosol size distribution and the aerosol extinction profile. A climatology of the volcanic plume dispersion is also reported. Simulations and measurements show that the plumes formed by weak eruptions have a stronger interaction with the surface of the island. Strong SO2 mixing ratio and particle concentrations above 1000 ppb and 50 000 cm-3 respectively are frequently measured over a distance of 20 km from Piton de la Fournaise. The measured aerosol size distribution shows the predominance of small particles in the volcanic plume. Several cases of strong nucleation of sulfuric acid have been observed within the plume and at the distal site of the Maïdo observatory. The STRAP 2015 campaign provides a unique set of multi-disciplinary data that can now be used by modellers to improve the numerical parameterisations of the physical and chemical evolution of the volcanic plumes.

  6. Backprojection of volcanic tremor (United States)

    Haney, Matthew M.


    Backprojection has become a powerful tool for imaging the rupture process of global earthquakes. We demonstrate the ability of backprojection to illuminate and track volcanic sources as well. We apply the method to the seismic network from Okmok Volcano, Alaska, at the time of an escalation in tremor during the 2008 eruption. Although we are able to focus the wavefield close to the location of the active cone, the network array response lacks sufficient resolution to reveal kilometer-scale changes in tremor location. By deconvolving the response in successive backprojection images, we enhance resolution and find that the tremor source moved toward an intracaldera lake prior to its escalation. The increased tremor therefore resulted from magma-water interaction, in agreement with the overall phreatomagmatic character of the eruption. Imaging of eruption tremor shows that time reversal methods, such as backprojection, can provide new insights into the temporal evolution of volcanic sources.

  7. Cell cycle-dependent SUMO-1 conjugation to nuclear mitotic apparatus protein (NuMA)

    Energy Technology Data Exchange (ETDEWEB)

    Seo, Jae Sung; Kim, Ha Na; Kim, Sun-Jick; Bang, Jiyoung; Kim, Eun-A; Sung, Ki Sa [Department of Biological Sciences, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Yoon, Hyun-Joo [TissueGene Inc. 9605 Medical Center Dr., Rockville, MD 20850 (United States); Yoo, Hae Yong [Department of Health Sciences and Technology, Samsung Advanced Institute for Health Sciences and Technology, Samsung Medical Center, Sungkyunkwan University, Seoul 135-710 (Korea, Republic of); Choi, Cheol Yong, E-mail: [Department of Biological Sciences, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)


    Highlights: •NuMA is modified by SUMO-1 in a cell cycle-dependent manner. •NuMA lysine 1766 is the primary target site for SUMOylation. •SUMOylation-deficient NuMA induces multiple spindle poles during mitosis. •SUMOylated NuMA induces microtubule bundling. -- Abstract: Covalent conjugation of proteins with small ubiquitin-like modifier 1 (SUMO-1) plays a critical role in a variety of cellular functions including cell cycle control, replication, and transcriptional regulation. Nuclear mitotic apparatus protein (NuMA) localizes to spindle poles during mitosis, and is an essential component in the formation and maintenance of mitotic spindle poles. Here we show that NuMA is a target for covalent conjugation to SUMO-1. We find that the lysine 1766 residue is the primary NuMA acceptor site for SUMO-1 conjugation. Interestingly, SUMO modification of endogenous NuMA occurs at the entry into mitosis and this modification is reversed after exiting from mitosis. Knockdown of Ubc9 or forced expression of SENP1 results in impairment of the localization of NuMA to mitotic spindle poles during mitosis. The SUMOylation-deficient NuMA mutant is defective in microtubule bundling, and multiple spindles are induced during mitosis. The mitosis-dependent dynamic SUMO-1 modification of NuMA might contribute to NuMA-mediated formation and maintenance of mitotic spindle poles during mitosis.

  8. Volcanic eruptions on Io (United States)

    Strom, R. G.; Schneider, N. M.; Terrile, R. J.; Hansen, C.; Cook, A. F.


    Nine eruption plumes which were observed during the Voyager 1 encounter with Io are discussed. During the Voyager 2 encounter, four months later, eight of the eruptions were still active although the largest became inactive sometime between the two encounters. Plumes range in height from 60 to over 300 km with corresponding ejection velocities of 0.5 to 1.0 km/s and plume sources are located on several plains and consist of fissures or calderas. The shape and brightness distribution together with the pattern of the surface deposition on a plume 3 is simulated by a ballistic model with a constant ejection velocity of 0.5 km/s and ejection angles which vary from 0-55 deg. The distribution of active and recent eruptions is concentrated in the equatorial regions and indicates that volcanic activity is more frequent and intense in the equatorial regions than in the polar regions. Due to the geologic setting of certain plume sources and large reservoirs of volatiles required for the active eruptions, it is concluded that sulfur volcanism rather than silicate volcanism is the most likely driving mechanism for the eruption plumes.

  9. Scaling of X pinches from 1 MA to 6 MA

    International Nuclear Information System (INIS)

    Bland, Simon Nicholas; McBride, Ryan D.; Wenger, David Franklin; Sinars, Daniel Brian; Chittenden, Jeremy Paul; Pikuz, Sergei A.; Harding, Eric; Jennings, Christopher A.; Ampleford, David J.; Yu, Edmund P.; Cuneo, Michael Edward; Shelkovenko, Tatiana A.; Hansen, Stephanie B.


    This final report for Project 117863 summarizes progress made toward understanding how X-pinch load designs scale to high currents. The X-pinch load geometry was conceived in 1982 as a method to study the formation and properties of bright x-ray spots in z-pinch plasmas. X-pinch plasmas driven by 0.2 MA currents were found to have source sizes of 1 micron, temperatures >1 keV, lifetimes of 10-100 ps, and densities >0.1 times solid density. These conditions are believed to result from the direct magnetic compression of matter. Physical models that capture the behavior of 0.2 MA X pinches predict more extreme parameters at currents >1 MA. This project developed load designs for up to 6 MA on the SATURN facility and attempted to measure the resulting plasma parameters. Source sizes of 5-8 microns were observed in some cases along with evidence for high temperatures (several keV) and short time durations (<500 ps).

  10. New potassium-argon basalt data in relation to the Pliocene Bluff Downs Local Fauna, northern Australia

    International Nuclear Information System (INIS)

    Mackness, B.S.


    A new radiometric date of 3.6 Ma for the basalt overlying fossiliferous units of the Allingham Formation, provides a minimum age for the Bluff Downs Local Fauna. Ground studies and interpretation of aerial photography has clarified the volcanic history of the area and a new basalt flow has been identified and named. Although the age of the capping basalt permits a younger age for the Bluff Downs Local Fauna than originally described, the stratigraphy, combined with the interpreted stage of evolution of the fauna, still supports an Early Pliocene age for the site. Copyright (2000) Geological Society of Australia

  11. The onset of the volcanism in the Ciomadul Volcanic Dome Complex (Eastern Carpathians): Eruption chronology and magma type variation (United States)

    Molnár, Kata; Harangi, Szabolcs; Lukács, Réka; Dunkl, István; Schmitt, Axel K.; Kiss, Balázs; Garamhegyi, Tamás; Seghedi, Ioan


    Combined zircon U-Th-Pb and (U-Th)/He dating was applied to refine the eruption chronology of the last 2 Myr for the andesitic and dacitic Pilişca volcano and Ciomadul Volcanic Dome Complex (CVDC), the youngest volcanic area of the Carpathian-Pannonian region, located in the southernmost Harghita, eastern-central Europe. The proposed eruption ages, which are supported also by the youngest zircon crystallization ages, are much younger than the previously determined K/Ar ages. By dating every known eruption center in the CVDC, repose times between eruptive events were also accurately determined. Eruption of the andesite at Murgul Mare (1865 ± 87 ka) and dacite of the Pilişca volcanic complex (1640 ± 37 ka) terminated an earlier pulse of volcanic activity within the southernmost Harghita region, west of the Olt valley. This was followed by the onset of the volcanism in the CVDC, which occurred after several 100s kyr of eruptive quiescence. At ca. 1 Ma a significant change in the composition of erupted magma occurred from medium-K calc-alkaline compositions to high-K dacitic (Baba-Laposa dome at 942 ± 65 ka) and shoshonitic magmas (Malnaş and Bixad domes; 964 ± 46 ka and 907 ± 66 ka, respectively). Noteworthy, eruptions of magmas with distinct chemical compositions occurred within a restricted area, a few km from one another. These oldest lava domes of the CVDC form a NNE-SSW striking tectonic lineament along the Olt valley. Following a brief (ca. 100 kyr) hiatus, extrusion of high-K andesitic magma continued at Dealul Mare (842 ± 53 ka). After another ca. 200 kyr period of quiescence two high-K dacitic lava domes extruded (Puturosul: 642 ± 44 ka and Balvanyos: 583 ± 30 ka). The Turnul Apor lava extrusion occurred after a ca. 200 kyr repose time (at 344 ± 33 ka), whereas formation of the Haramul Mic lava dome (154 ± 16 ka) represents the onset of the development of the prominent Ciomadul volcano. The accurate determination of eruption dates shows that the

  12. Garnet pyroxenite from Nilgiri Block, southern India: Vestiges of a Neoarchean volcanic arc (United States)

    Samuel, Vinod O.; Kwon, Sanghoon; Santosh, M.; Sajeev, K.


    Southern peninsular India preserves records of Late Neoarchean-Early Paleoproterozoic continental building and cratonization. A transect from the Paleoarchean Dharwar Craton to the Neoarchean arc magmatic complex in the Nilgiri Block across the intervening Moyar Suture Zone reveals an arc-accretionary complex composed of banded iron formation (BIF), amphibolite, metatuff, garnet-kyanite schist, metagabbro, pyroxenite and charnockite. Here we investigate the petrology, geochronology and petrogenesis of the pyroxenite and garnet-clinopyroxenite. The pyroxenite is mainly composed of orthopyroxene and clinopyroxene with local domains/pockets enriched in a clinopyroxene-garnet assemblage. Thermobarometric calculations and phase equilibria modeling suggest that the orthopyroxene- and clinopyroxene-rich domains formed at 900-1000 °C, 1-1.2 GPa whereas the garnet- and clinopyroxene-rich domains record higher pressure of about 1.8-2 GPa at similar temperature conditions (900-1000 °C). Zircon U-Pb SHRIMP dating show weighted mean 207Pb-206Pb age of 2532 ± 22 Ma, with metamorphic overgrowth at 2520 ± 27 Ma and 2478 ± 27 Ma. We propose a tectonic model involving decoupling and break-off of the oceanic plate along the southern flanks of the Dharwar Craton, which initiated oceanic plate subduction. Slab melting eventually built the Nilgiri volcanic arc on top of the over-riding plate along the flanks of the Dharwar Craton. Our study supports an active plate tectonic regime at the end of the Archean Era, aiding in the growth of paleo-continents and their assembly into stable cratons.

  13. The Banana Fruit SINA Ubiquitin Ligase MaSINA1 Regulates the Stability of MaICE1 to be Negatively Involved in Cold Stress Response. (United States)

    Fan, Zhong-Qi; Chen, Jian-Ye; Kuang, Jian-Fei; Lu, Wang-Jin; Shan, Wei


    The regulation of ICE1 protein stability is important to ensure effective cold stress response, and is extensively studied in Arabidopsis . Currently, how ICE1 stability in fruits under cold stress is controlled remains largely unknown. Here, we reported the possible involvement of a SEVEN IN ABSENTIA (SINA) ubiquitin ligase MaSINA1 from banana fruit in affecting MaICE1 stability. MaSINA1 was identified based on a yeast two-hybrid screening using MaICE1 as bait. Further yeast two-hybrid, pull-down, bimolecular fluorescence complementation (BiFC) and co-immunoprecipitation (CoIP) assays confirmed that MaSINA1 interacted with MaICE1. The expression of MaSINA1 was repressed by cold stress. Subcellular localization analysis in tobacco leaves showed that MaSINA1 was localized predominantly in the nucleus. In vitro ubiquitination assay showed that MaSINA1 possessed E3 ubiquitin ligase activity. More importantly, in vitro and semi- in vivo experiments indicated that MaSINA1 can ubiquitinate MaICE1 for the 26S proteasome-dependent degradation, and therefore suppressed the transcriptional activation of MaICE1 to MaNAC1, an important regulator of cold stress response of banana fruit. Collectively, our data reveal a mechanism in banana fruit for control of the stability of ICE1 and for the negative regulation of cold stress response by a SINA E3 ligase via the ubiquitin proteasome system.

  14. Shield Through Rejuvenated Stage Volcanism On Kauai and Niihau, Hawaii (United States)

    Cousens, B.; Clague, D. A.


    Kauai and Niihau are the northwesternmost large islands in the Hawaiian chain and consist of shield, rare postshield, and abundant rejuvenated stage lavas. We present new geochronological, geochemical and isotopic data for all phases of volcanic activity on the adjacent islands. K-Ar ages show Niihau shield volcanism occurred from 6.3-4.4 Ma, and K-Ar and new Ar-Ar ages for postshield volcanism range from 5.4-4.7 Ma. Kauai shield volcanism (K-Ar) overlaps with shield volcanism on Niihau. A new Ar-Ar age for a Kauai postshield dike is 4.4 Ma, older than previously-dated postshield lavas (3.95-3.58 Ma). New Ar-Ar ages show that Kauai rejuvenated stage volcanism began prior to 3.42 Ma (Izuka & Sherrod, 2011), compared to ~2.3 Ma on Niihau. Tholeiitic shield lavas from Kauai vary only slightly in trace element chemistry but have variable isotopic compositions. Subtle trends in some trace element and isotopic ratios between Napali Member shield lavas from the east and west side of Kauai support the two-shield hypothesis of Holcomb et al. (1997). Shield lavas from Niihau are chemically similar to those on Kauai, although Niihau tholeiites extend to higher 143Nd/144Nd ratios. Onland and submarine postshield rocks from Niihau are slightly more alkaline and LREE-enriched compared to shield lavas, but postshield rocks from Kauai are more chemically evolved, more LREE-enriched, and have more depleted Sr and Nd isotopic signatures than Kauai tholeiites. Postshield rocks on Kauai overlap in apparent age with lavas that are chemically like later rejuvenated stage lavas, suggesting either interfingering of the chemically distinct lavas or problems with the K-Ar ages. Rejuvenated stage lavas from the two islands differ dramatically; Kauai lavas are alkaline, LREE-enriched, and have even more depleted Sr and Nd isotopic compositions than postshield lavas, whereas Niihau lavas are only mildly alkaline, have lower REE abundances than postshield basalts, but isotopically are like

  15. Lidar detection of carbon dioxide in volcanic plumes (United States)

    Fiorani, Luca; Santoro, Simone; Parracino, Stefano; Maio, Giovanni; Del Franco, Mario; Aiuppa, Alessandro


    Volcanic gases give information on magmatic processes. In particular, anomalous releases of carbon dioxide precede volcanic eruptions. Up to now, this gas has been measured in volcanic plumes with conventional measurements that imply the severe risks of local sampling and can last many hours. For these reasons and for the great advantages of laser sensing, the thorough development of volcanic lidar has been undertaken at the Diagnostics and Metrology Laboratory (UTAPRAD-DIM) of the Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA). In fact, lidar profiling allows one to scan remotely volcanic plumes in a fast and continuous way, and with high spatial and temporal resolution. Two differential absorption lidar instruments will be presented in this paper: BILLI (BrIdge voLcanic LIdar), based on injection seeded Nd:YAG laser, double grating dye laser, difference frequency mixing (DFM) and optical parametric amplifier (OPA), and VULLI (VULcamed Lidar), based on injection seeded Nd:YAG laser and optical parametric oscillator (OPO). The first one is funded by the ERC (European Research Council) project BRIDGE and the second one by the ERDF (European Regional Development Fund) project VULCAMED. While VULLI has not yet been tested in a volcanic site, BILLI scanned the gas emitted by Pozzuoli Solfatara (Campi Flegrei volcanic area, Naples, Italy) during a field campaign carried out from 13 to 17 October 2014. Carbon dioxide concentration maps were retrieved remotely in few minutes in the crater area. Lidar measurements were in good agreement with well-established techniques, based on different operating principles. To our knowledge, it is the first time that carbon dioxide in a volcanic plume is retrieved by lidar, representing the first direct measurement of this kind ever performed on an active volcano and showing the high potential of laser remote sensing in geophysical research.

  16. U-Pb zircon age for a volcanic suite in the Rankin Inlet Group, Rankin Inlet map area, District of Keewatin, Northwest Territories

    Energy Technology Data Exchange (ETDEWEB)

    Tella, S; Roddick, J C; VanBreemen, O [Geological Survey of Canada, Ottawa, ON (Canada)


    U-Pb zircon analyses from a felsic band within dominantly mafic volcanics of the Rankin Inlet Group yields a U-Pb upper concordia intercept age of 2663 {+-} 3 Ma. These supracrustals at Rankin Inlet appear to be 15-20 Ma younger than volcanics of the Kaminak Group in the Tavani area, 70 km to the southwest. The 2.68-2.66 Ga volcanism in the Tavani and Rankin Inlet areas coincided with the last stage of the main phase of magmatism in the Slave Structural Province. (author). 16 refs., 1 tab., 3 figs.

  17. U-Pb zircon age for a volcanic suite in the Rankin Inlet Group, Rankin Inlet map area, District of Keewatin, Northwest Territories

    International Nuclear Information System (INIS)

    Tella, S.; Roddick, J.C.; VanBreemen, O.


    U-Pb zircon analyses from a felsic band within dominantly mafic volcanics of the Rankin Inlet Group yields a U-Pb upper concordia intercept age of 2663 ± 3 Ma. These supracrustals at Rankin Inlet appear to be 15-20 Ma younger than volcanics of the Kaminak Group in the Tavani area, 70 km to the southwest. The 2.68-2.66 Ga volcanism in the Tavani and Rankin Inlet areas coincided with the last stage of the main phase of magmatism in the Slave Structural Province. (author). 16 refs., 1 tab., 3 figs

  18. Silicic magmatism associated with Late Cretaceousrifting in the Arctic Basin – petrogenesis of the Kap Kane sequence, the Kap Washington Group volcanics, North Greenland

    DEFF Research Database (Denmark)

    Þórarinsson, Sigurjón Böðvar; Holm, Paul Martin; Duprat, Helene Inga


    The bimodal, Late Cretaceous–Palaeocene (71–61 Ma) Kap Washington Group volcanic sequence on the north coast of Greenland was erupted in a continental rift setting during the opening of the Arctic Ocean. On Kap Kane ca. 70 Ma silicic lavas and ignimbrites dominate over mildly alkaline basalts...

  19. A field trip guide to the petrology of Quaternary volcanism on the Yellowstone Plateau (United States)

    Vazquez, Jorge A.; Stelten, Mark; Bindeman, Ilya N.; Cooper, Kari


    The Yellowstone Plateau is one of the largest manifestations of silicic volcanism on Earth, and marks the youngest focus of magmatism associated with the Yellowstone Hot Spot. The earliest products of Yellowstone Hot Spot volcanism are from ~17 million years ago, but may be as old as ~32 Ma, and include contemporaneous eruption of voluminous mafic and silicic magmas, which are mostly located in the region of northwestern Nevada and southeastern Oregon. Since 17 Ma, the main locus of Yellowstone Hot Spot volcanism has migrated northeastward producing numerous silicic caldera complexes that generally remain active for ~2–4 million years, with the present-day focus being the Yellowstone Plateau. Northeastward migration of volcanism associated with the Yellowstone Hot Spot resulted in the formation of the Snake River Plain, a low relief physiographic feature extending ~750 kilometers from northern Nevada to eastern Idaho. Most of the silicic volcanic centers along the Snake River Plain have been inundated by younger basalt volcanism, but many of their ignimbrites and lava flows are exposed in the extended regions at the margins of the Snake River Plain. 

  20. K-Ar ages of the Neogene volcanic rocks from the Oshamambe district, southwestern Hokkaido

    International Nuclear Information System (INIS)

    Kubo, Kazuya; Shibata, Ken; Ishida, Masao


    Oshamanbe district is on the northern extension of the so-called green tuff district in northeastern Japan, and the sedimentary rocks in a sea area and volcanic rocks from Miocene to Pleistocene widely distribute. The authors carried out the geological survey of this district, and published the results as the geological features in Oshamanbe district. The volcanic rocks distributing in this district range from andesite to dacite and rhyolite. Their lithofacies are mostly volcanic breccia and tuff breccia, accompanied by lava and dikes. This time, the measurement of the age of these volcanic rocks was carried out, and the stratigraphical table made by the authors was investigated. It is considered that those age values offer important information for determining the age of the Setana formation. The outline of the geological features, the samples for the measurement, the method of measurement of Ar isotopic ratio and K, and the results of measurement are reported. As the results, 4.38 - 4.47 Ma were obtained for Garogawa volcanic rocks, and 2.59 Ma for Shamanbesan volcanic rocks. The period of sedimentation of the Setana formation was from the latter period of Pliocene to pleistocene. (Kako, I.)

  1. Geophysical evidence for widespread reversely magnetised pyroclastics in the western Taupo Volcanic Zone (New Zealand)

    International Nuclear Information System (INIS)

    Soengkono, S.; Hochstein, M.P.; Smith, I.E.M.; Itaya, T.


    Low-altitude aeromagnetic data show that negative residual anomalies are widespread over the western Taupo Volcanic Zone, New Zealand. Paleomagnetic study of eight rhyolitic ignimbrite units and two lava flows which are exposed in this area, together with new K-Ar dates of four of the ignimbrite units, indicate that the two lava units and seven of the ignimbrite units were erupted during the Matuyama geomagnetic epoch (>0.73 Ma B.P.) and suggest that rhyolitic volcanism in the western Taupo Volcanic Zone began as early as 1.6 Ma B.P. These results provide the basis for an interpretation of our aeromagnetic data which confirms the hypothesis that the magnetic anomalies observed in the western Taupo Volcanic Zone are caused by widespread, thick, reversely magnetised pyroclastic and lava flows. Magnetic modelling also allows thickness estimates of the younger, normally magnetised cover rocks which reach a maximum thickness of the order of 0.5 km in the Mangakino area. The magnetic structure of these volcanic rocks defines approximately the lateral extent of the Mangakino Volcanic Centre. (author). 41 refs., 2 figs., 3 tabs

  2. Volcanic risk; Risque volcanique

    Energy Technology Data Exchange (ETDEWEB)

    Rancon, J.P.; Baubron, J.C.


    This project follows the previous multi-disciplinary studies carried out by the French Bureau de Recherches Geologiques et Minieres (BRGM) on the two active volcanoes of the French lesser Antilles: Mt Pelee (Martinique) and Soufriere (Guadeloupe) for which geological maps and volcanic risk studies have been achieved. The research program comprises 5 parts: the study of pyroclastic deposits from recent eruptions of the two volcanoes for a better characterization of their eruptive phenomenology and a better definition of crisis scenarios; the study of deposits and structures of active volcanoes from Central America and the study of eruptive dynamics of andesite volcanoes for a transposition to Antilles` volcanoes; the starting of a methodological multi-disciplinary research (volcanology, geography, sociology...) on the volcanic risk analysis and on the management of a future crisis; and finally, the development of geochemical survey techniques (radon, CO{sub 2}, H{sub 2}O) on active volcanoes of Costa-Rica and Europe (Fournaise, Furnas, Etna) and their application to the Soufriere. (J.S.). 9 refs., 3 figs.

  3. Volcanic Eruptions and Climate (United States)

    LeGrande, Allegra N.; Anchukaitis, Kevin J.


    Volcanic eruptions represent some of the most climatically important and societally disruptive short-term events in human history. Large eruptions inject ash, dust, sulfurous gases (e.g. SO2, H2S), halogens (e.g. Hcl and Hbr), and water vapor into the Earth's atmosphere. Sulfurous emissions principally interact with the climate by converting into sulfate aerosols that reduce incoming solar radiation, warming the stratosphere and altering ozone creation, reducing global mean surface temperature, and suppressing the hydrological cycle. In this issue, we focus on the history, processes, and consequences of these large eruptions that inject enough material into the stratosphere to significantly affect the climate system. In terms of the changes wrought on the energy balance of the Earth System, these transient events can temporarily have a radiative forcing magnitude larger than the range of solar, greenhouse gas, and land use variability over the last millennium. In simulations as well as modern and paleoclimate observations, volcanic eruptions cause large inter-annual to decadal-scale changes in climate. Active debates persist concerning their role in longer-term (multi-decadal to centennial) modification of the Earth System, however.

  4. Anti-Ma2 antibody related paraneoplastic limbic/brain stem encephalitis associated with breast cancer expressing Ma1, Ma2, and Ma3 mRNAs. (United States)

    Sahashi, K; Sakai, K; Mano, K; Hirose, G


    A 69 year old woman presented with cognitive impairment and supranuclear gaze palsy caused by paraneoplastic limbic/brain stem encephalitis associated with atypical medullary breast carcinoma. The cerebrospinal fluid from the patient harboured an anti-neuronal cell antibody against Ma2 antigen, but not against Ma1 or Ma3 antigen. Despite the antibody being restricted to the Ma2 antigen, the patient's cancer tissue expressed Ma1, Ma2, and Ma3 mRNAs. These results, and the expression of Ma2 mRNA in an atypical medullar breast carcinoma in another patient without paraneoplastic encephalitis, indicate that the induction of anti-Ma2 antibody depends on host immunoreponsiveness and not on the presence of the antigen itself in the cancer.

  5. Convective removal of the Tibetan Plateau mantle lithosphere by 26 Ma (United States)

    Lu, Haijian; Tian, Xiaobo; Yun, Kun; Li, Haibing


    During the late Oligocene-early Miocene there were several major geological events in and around the Tibetan Plateau (TP). First, crustal shortening deformation ceased completely within the TP before 25 Ma and instead adakitic rocks and potassic-ultrapotassic volcanics were emplaced in the Lhasa terrane since 26-25 Ma. Several recent paleoelevation reconstructions suggest an Oligocene-early Miocene uplift of 1500-3000 m for the Qiangtang (QT) and Songpan-Ganzi (SG) terranes, although the exact timing is unclear. As a possible response to this uplift, significant desertification occurred in the vicinity of the TP at 26-22 Ma, and convergence between India and Eurasia slowed considerably at 26-20 Ma. Subsequently, E-W extension was initiated no later than 18 Ma in the Lhasa and QT terranes. In contrast, the tectonic deformation around the TP was dominated by radial expansion of shortening deformation since 25-22 Ma. The plateau-wide near-synchroneity of these events calls for an internally consistent model which can be best described as convective removal of the lower mantle lithosphere. Geophysical and petrochemical evidence further confirms that this extensive removal occurred beneath the QT and SG terranes. The present review concludes that, other than plate boundary stress, the internal stress within the TP lithosphere could have contributed to rapid wholesale uplift and a series of concomitant tectonic events, accompanied by major aridification, since 26 Ma.

  6. BaMa / Raivo Juurak

    Index Scriptorium Estoniae

    Juurak, Raivo, 1949-


    Eesti ülikoolide üleminekust 3+2 süsteemile. Lühend BaMa on tulnud kasutusele seoses Euroopa ülikoolide õppekavade reformimisega ning tähistab õppekava, kus esimese astme läbimise järel omandatakse bakalaureuse- ja teise järel magistrikraad. Õppekavade tüüpidest Eesti ja Euroopa Liidu kõrgkoolides ning Bologna deklaratsioonist

  7. Multiple episodes of hydrothermal activity and epithermal mineralization in the southwestern Nevada volcanic field and their relations to magmatic activity, volcanism and regional extension

    International Nuclear Information System (INIS)

    Weiss, S.I.; Noble, D.C.; Jackson, M.C.


    Volcanic rocks of middle Miocene age and underlying pre-Mesozoic sedimentary rocks host widely distributed zones of hydrothermal alteration and epithermal precious metal, fluorite and mercury deposits within and peripheral to major volcanic and intrusive centers of the southwestern Nevada volcanic field (SWNVF) in southern Nevada, near the southwestern margin of the Great Basin of the western United States. Radiometric ages indicate that episodes of hydrothermal activity mainly coincided with and closely followed major magmatic pulses during the development of the field and together spanned more than 4.5 m.y. Rocks of the SWNVF consist largely of rhyolitic ash-flow sheets and intercalated silicic lava domes, flows and near-vent pyroclastic deposits erupted between 15.2 and 10 Ma from vent areas in the vicinity of the Timber Mountain calderas, and between about 9.5 and 7 Ma from the outlying Black Mountain and Stonewall Mountain centers. Three magmatic stages can be recognized: the main magmatic stage, Mountain magmatic stage (11.7 to 10.0 Ma), and the late magmatic stage (9.4 to 7.5 Ma)

  8. Isotopic dating of the post-Alpine Neogene volcanism in the Betic Cordilleras, southern Spain

    Energy Technology Data Exchange (ETDEWEB)

    Nobel, F A; Rondeel, H E [Amsterdam Univ. (Netherlands). Geologisch Inst.; Andriessen, P A.M.; Hebeda, E H; Priem, H N.A. [Laboratorium voor Isotopen-Geologie, Amsterdam (Netherlands)


    The post-Alpine lamproitic volcanism in the Prebetic of the External Zone of the Betic Cordilleras of southern Spain is dated at 7.6-7.2 Ma by the K-Ar data from two richterites, two sanidines, a phlogopite and a whole-rock, and the fission-track analysis of an apatite. Biotite from a lava of the rhyolitic-dacitic suite in the post-orogenic Vera basin of the Internal Zone produces the same age. Phlogopite from a lamproitic (veritic) subvolcanic body in the Vera basin yields an age of about 8.6 Ma; as lavas belonging to the veritic suite reportedly overlie Late Messinian sediments, pointing to an age of less than about 5 Ma, this type of volcanism in the Vera basin must have been active over several million years.

  9. Age and petrogenetic constraints on the Lower Glassy Ignimbrite of the Mount Somers Volcanic Group, New Zealand

    DEFF Research Database (Denmark)

    van der Meer, Quinten; Waight, Tod Earle; Whitehouse, Martin


    The Mount Somers Volcanic Group (MSVG) forms a large (~18000 km2) calc-alkaline volcanic complex on New Zealand’s Eastern Province. U-Pb SIMS spot ages on zircon from the lower glassy ignimbrite in Rakaia Gorge reveal a bimodal distribution of 99.0 ± 0.5 and 96.3 ± 0.5 Ma (2σ). These ages...

  10. Friction in volcanic environments (United States)

    Kendrick, Jackie E.; Lavallée, Yan


    Volcanic landscapes are amongst the most dynamic on Earth and, as such, are particularly susceptible to failure and frictional processes. In rocks, damage accumulation is frequently accompanied by the release of seismic energy, which has been shown to accelerate in the approach to failure on both a field and laboratory scale. The point at which failure occurs is highly dependent upon strain-rate, which also dictates the slip-zone properties that pertain beyond failure, in scenarios such as sector collapse and pyroclastic flows as well as the ascent of viscous magma. High-velocity rotary shear (HVR) experiments have provided new opportunities to overcome the grand challenge of understanding faulting processes during volcanic phenomena. Work on granular ash material demonstrates that at ambient temperatures, ash gouge behaves according to Byerlee's rule at low slip velocities, but is slip-weakening, becoming increasingly lubricating as slip ensues. In absence of ash along a slip plane, rock-rock friction induces cataclasis and heating which, if sufficient, may induce melting (producing pseudotachylyte) and importantly, vesiculation. The viscosity of the melt, so generated, controls the subsequent lubrication or resistance to slip along the fault plane thanks to non-Newtonian suspension rheology. The shear-thinning behaviour and viscoelasticity of frictional melts yield a tendency for extremely unstable slip, and occurrence of frictional melt fragmentation. This velocity-dependence acts as an important feedback mechanism on the slip plane, in addition to the bulk composition, mineralogy and glass content of the magma, that all influence frictional behaviour. During sector collapse events and in pyroclastic density currents it is the frictional properties of the rocks and ash that, in-part, control the run-out distance and associated risk. In addition, friction plays an important role in the eruption of viscous magmas: In the conduit, the rheology of magma is integral

  11. 42 CFR 495.202 - Identification of qualifying MA organizations, MA-EPs and MA-affiliated eligible hospitals. (United States)


    ... qualifying MA-affiliated eligible hospitals under the MA EHR incentive program are required to identify...-EPs and MA-affiliated eligible hospitals. 495.202 Section 495.202 Public Health CENTERS FOR MEDICARE... STANDARDS FOR THE ELECTRONIC HEALTH RECORD TECHNOLOGY INCENTIVE PROGRAM Requirements Specific to Medicare...

  12. Geology and petrology of the Woods Mountains Volcanic Center, southeastern California: Implications for the genesis of peralkaline rhyolite ash flow tuffs (United States)

    McCurry, Michael


    The Woods Mountains Volcanic Center is a middle Miocene silicic caldera complex located at the transition from the northern to the southern Basin and Range provinces of the western United States. It consists of a trachyte-trachydacite-rhyolite-peralkaline rhyolite association of lava flows, domes, plugs, pyroclastic rocks, and epiclastic breccia. Volcanism began at about 16.4 Ma, near the end of a local resurgence of felsic to intermediate magmatism and associated crustal extension. Numerous metaluminous high-K trachyte, trachydacite, and rhyolite lava flows, domes, and pyroclastic deposits accumulated from vents scattered over an area of 200 km2 forming a broad volcanic field with an initial volume of about 10 km3. At 15.8 Ma, about 80 km3 of metaluminous to mildly peralkaline high-K rhyolite ash flows were erupted from vents in the western part of fhe field in three closely spaced pulses, resulting in the formation of a trap door caldera 10 km in diameter. The ash flows formed the Wild Horse Mesa Tuff, a compositionally zoned ash flow sheet that originally covered an area of about 600 km2 to a maximum thickness of at least 320 m. High-K trachyte pumice lapilli, some of which are intimately banded with rhyolite, were produced late in the two later eruptions, Intracaldera volcanism from widely distributed vents rapidly filled the caldera with about 10 km3 of high-K, mildly peralkaline, high-silica rhyolite lava flows and pyroclastic deposits. These are interlayered with breccia derived from the caldera scarp. They are intruded by numerous compositionally similar plugs, some of which structurally uplifted and fractured the center of the caldera. The center evolved above a high-K trachyte magma chamber about 10 km in diameter that had developed and differentiated within the upper crust at about 15.8 Ma. Petrological, geochemical, and geophysical data are consistent with the idea that a cap of peralkaline rhyolite magma formed within the trachyte chamber as a result

  13. Geology and geochronology of the Tana Basin, Ethiopia: LIP volcanism, super eruptions and Eocene-Oligocene environmental change (United States)

    Prave, A. R.; Bates, C. R.; Donaldson, C. H.; Toland, H.; Condon, D. J.; Mark, D.; Raub, T. D.


    New geological and geochronological data define four episodes of volcanism for the Lake Tana region in the northern Ethiopian portion of the Afro-Arabian Large Igneous Province (LIP): pre-31 Ma flood basalt that yielded a single 40Ar/39Ar age of 34.05 ± 0.54 / 0.56 Ma; thick and extensive felsic ignimbrites and rhyolites (minimum volume of 2- 3 ×103 km3) erupted between 31.108 ± 0.020 / 0.041 Ma and 30.844 ± 0.027 / 0.046 Ma (U-Pb CA-ID-TIMS zircon ages); mafic volcanism bracketed by 40Ar/39Ar ages of 28.90 ± 0.12 / 0.14 Ma and 23.75 ± 0.02 / 0.04 Ma; and localised scoraceous basalt with an 40Ar/39Ar age of 0.033 ± 0.005 / 0.005 Ma. The felsic volcanism was the product of super eruptions that created a 60-80 km diameter caldera marked by km-scale caldera-collapse fault blocks and a steep-sided basin filled with a minimum of 180 m of sediment and the present-day Lake Tana. These new data enable mapping, with a finer resolution than previously possible, Afro-Arabian LIP volcanism onto the timeline of the Eocene-Oligocene transition and show that neither the mafic nor silicic volcanism coincides directly with perturbations in the geochemical records that span that transition. Our results reinforce the view that it is not the development of a LIP alone but its rate of effusion that contributes to inducing global-scale environmental change.

  14. Volcanic passive margins: another way to break up continents. (United States)

    Geoffroy, L; Burov, E B; Werner, P


    Two major types of passive margins are recognized, i.e. volcanic and non-volcanic, without proposing distinctive mechanisms for their formation. Volcanic passive margins are associated with the extrusion and intrusion of large volumes of magma, predominantly mafic, and represent distinctive features of Larges Igneous Provinces, in which regional fissural volcanism predates localized syn-magmatic break-up of the lithosphere. In contrast with non-volcanic margins, continentward-dipping detachment faults accommodate crustal necking at both conjugate volcanic margins. These faults root on a two-layer deformed ductile crust that appears to be partly of igneous nature. This lower crust is exhumed up to the bottom of the syn-extension extrusives at the outer parts of the margin. Our numerical modelling suggests that strengthening of deep continental crust during early magmatic stages provokes a divergent flow of the ductile lithosphere away from a central continental block, which becomes thinner with time due to the flow-induced mechanical erosion acting at its base. Crustal-scale faults dipping continentward are rooted over this flowing material, thus isolating micro-continents within the future oceanic domain. Pure-shear type deformation affects the bulk lithosphere at VPMs until continental breakup, and the geometry of the margin is closely related to the dynamics of an active and melting mantle.

  15. Strontium isotopic ratios of Tertiary volcanic rocks of northeastern Honshu, Japan: implication for the spreading of the Japan Sea

    International Nuclear Information System (INIS)

    Kurasawa, Hajime; Konda, Tadashi.


    Strontium isotopic ratios of sixty-seven Tertiary volcanic rocks from the northeastern Honshu, Japan, were determined for the purpose of examining the genesis among the volcanic rocks. Two distince suites of volcanic rocks occur in the northeastern Honshu; the rocks older than 16 Ma (Monzen-Daijima Stege) of predominantly intermediate composition and the rocks younger than 16 Ma (Nishikurosawa-Funakawa Stege) with bimodal suite of mafic and felsic composition. Initial values of 87 Sr/ 86 Sr in the Teriary volcanic rocks from the northeastern Honshu, lie in the range from 0.7033 to 0.7068. High ( 87 Sr/ 86 Sr) I ratios are observed for the rocks older than 16 Ma from the Japan Sea side (H zone). It is noteworthy that the rocks younger than 16 Ma show significantly lower ( 87 Sr/ 86 Sr) I ratios in the Dewa Hill, Japan Sea coast and North Akita areas in the northeastern Honshu (L zone). The rocks younger than 16 Ma from the L zone can also be interpreted as having been originated as a mantle-diapir associated with the spreading of the Japan Sea basin. If the basaltic magma was formed from the diapir, the 87 Sr/ 86 Sr ratio would be close to the range from 0.7033 to 0.7037 as the low-Sr isotopic ratio zone (L zone) in the northeastern Honshu, Japan. (author)

  16. The Snake River Plain Volcanic Province: Insights from Project Hotspot (United States)

    Shervais, J. W.; Potter, K. E.; Hanan, B. B.; Jean, M. M.; Duncan, R. A.; Champion, D. E.; Vetter, S.; Glen, J. M. G.; Christiansen, E. H.; Miggins, D. P.; Nielson, D. L.


    The Snake River Plain (SRP) Volcanic Province is the best modern example of a time-transgressive hotspot track beneath continental crust. The SRP began 17 Ma with massive eruptions of Columbia River basalt and rhyolite. After 12 Ma volcanism progressed towards Yellowstone, with early rhyolite overlain by basalts that may exceed 2 km thick. The early rhyolites are anorogenic with dry phenocryst assemblages and eruption temperatures up to 950C. Tholeiitic basalts have major and trace element compositions similar to ocean island basalts (OIB). Project Hotspot cored three deep holes in the central and western Snake River Plain: Kimama (mostly basalt), Kimberly (mostly rhyolite), and Mountain Home (lake sediments and basaslt). The Kimberly core documents rhyolite ash flows up to 700 m thick, possibly filling a caldera or sag. Chemical stratigraphy in Kimama and other basalt cores document fractional crystallization in relatively shallow magma chambers with episodic magma recharge. Age-depth relations in the Kimama core suggest accumulation rates of roughly 305 m/Ma. Surface and subsurface basalt flows show systematic variations in Sr-Nd-Pb isotopes with distance from Yellowstone interpreted to reflect changes in the proportion of plume source and the underlying heterogeneous cratonic lithosphere, which varies in age, composition, and thickness from west to east. Sr-Nd-Pb isotopes suggest <5% lithospheric input into a system dominated by OIB-like plume-derived basalts. A major flare-up of basaltic volcanism occurred 75-780 ka throughout the entire SRP, from Yellowstone in the east to Boise in the west. The youngest western SRP basalts are transitional alkali basalts that range in age from circa 900 ka to 2 ka, with trace element and isotopic compositions similar to the plume component of Hawaiian basalts. These observations suggest that ancient SCLM was replaced by plume mantle after the North America passed over the hotspot in the western SRP, which triggered renewed

  17. Intense acidic volcanism at the Cretaceous-Tertiary boundary

    International Nuclear Information System (INIS)

    Javoy, M.; Courtillot, V.


    A 87 Sr/ 86 Sr spike in seawater strontium with amplitude 2 x 10 -4 and duration of order 2 Ma is superimposed on longer-term variations at the Cretaceous-Tertiary boundary. The anomaly has been attributed to increased continental runoff due either to meteorite impact-related acid rain or sea-level regression. We speculate here that the spike could have resulted from intense, explosive acid volcanism preceding the development of the Deccan traps. A good model, both in tectonic position and geochemical characteristics, for these as yet elusive acidic products is provided by granites in the Seychelles Islands and particularly Mahe. (orig.)

  18. Closer look at lunar volcanism

    International Nuclear Information System (INIS)

    Vaniman, D.T.; Heiken, G.; Taylor, G.J.


    Although the American Apollo and Soviet Luna missions concentrated on mare basalt samples, major questions remain about lunar volcanism. Lunar field work will be indispensable for resolving the scientific questions about ages, compositions, and eruption processes of lunar volcanism. From a utilitarian standpoint, a better knowledge of lunar volcanism will also yield profitable returns in lunar base construction (e.g., exploitation of rille or lava-tube structures) and in access to materials such as volatile elements, pure glass, or ilmenite for lunar industry

  19. Large-scale volcanism associated with coronae on Venus (United States)

    Roberts, K. Magee; Head, James W.


    The formation and evolution of coronae on Venus are thought to be the result of mantle upwellings against the crust and lithosphere and subsequent gravitational relaxation. A variety of other features on Venus have been linked to processes associated with mantle upwelling, including shield volcanoes on large regional rises such as Beta, Atla and Western Eistla Regiones and extensive flow fields such as Mylitta and Kaiwan Fluctus near the Lada Terra/Lavinia Planitia boundary. Of these features, coronae appear to possess the smallest amounts of associated volcanism, although volcanism associated with coronae has only been qualitatively examined. An initial survey of coronae based on recent Magellan data indicated that only 9 percent of all coronae are associated with substantial amounts of volcanism, including interior calderas or edifices greater than 50 km in diameter and extensive, exterior radial flow fields. Sixty-eight percent of all coronae were found to have lesser amounts of volcanism, including interior flooding and associated volcanic domes and small shields; the remaining coronae were considered deficient in associated volcanism. It is possible that coronae are related to mantle plumes or diapirs that are lower in volume or in partial melt than those associated with the large shields or flow fields. Regional tectonics or variations in local crustal and thermal structure may also be significant in determining the amount of volcanism produced from an upwelling. It is also possible that flow fields associated with some coronae are sheet-like in nature and may not be readily identified. If coronae are associated with volcanic flow fields, then they may be a significant contributor to plains formation on Venus, as they number over 300 and are widely distributed across the planet. As a continuation of our analysis of large-scale volcanism on Venus, we have reexamined the known population of coronae and assessed quantitatively the scale of volcanism associated

  20. Petrogenesis and tectonic implication of the Late Triassic post-collisional volcanic rocks in Chiang Khong, NW Thailand (United States)

    Qian, Xin; Wang, Yuejun; Feng, Qinglai; Zi, Jian-Wei; Zhang, Yuzhi; Chonglakmani, Chongpan


    The volcanic rocks exposed within the Chiang Khong-Lampang-Tak igneous zone in NW Thailand provide important constraints on the tectonic evolution of the eastern Paleotethys ocean. An andesite sample from the Chiang Khong area yields a zircon U-Pb age of 229 ± 4 Ma, significantly younger than the continental-arc and syn-collisional volcanic rocks (ca. 238-241 Ma). The Chiang Khong volcanic rocks are characterized by low MgO (1.71-6.72 wt.%) and high Al2O3 (15.03-17.76 wt.%). They are enriched in LILEs and LREEs and depleted in HFSEs, and have 87Sr/86Sr (i) ratios of 0.7050-0.7065, εNd (t) of - 0.32 to - 1.92, zircon εHf (t) and δ18O values of 3.5 to - 11.7 and 4.30-9.80 ‰, respectively. The geochemical data for the volcanic rocks are consistent with an origin from the enriched lithospheric mantle that had been modified by slab-derived fluid and recycled sediments. Based on available geochronological and geochemical evidences, we propose that the Late Triassic Chiang Khong volcanic rocks are equivalent to the contemporaneous volcanic rocks in the Lancangjiang igneous zone in SW China. The formation of these volcanic rocks was possibly related to the upwelling of the asthenospheric mantle during the Late Triassic, shortly after slab detachment, which induced the melting of the metasomatized mantle wedge.

  1. The volcanism of the western part of the Los Frailes Meseta (Bolivia): a representative example of the Andean volcanism since the Upper Oligocene

    International Nuclear Information System (INIS)

    Leroy, L.; Jimenez, N.


    The Los Frailes Meseta (Bolivia) is one of the large tertiary ignimbritic fields of the inner volcanic arc from Central Andes (Central Volcanic Zone. CVZ), in contact zone between the Altiplano to the west and the Eastern Cordillera to the east. Field observations and mineralogical and geochemical studies (major and trace elements) lead to distinguish two types of volcanism in the western border to the Meseta. During the Middle Miocene and Pliocene, the volcanic activity can be subdivided into three pyroclastic emission cycles, the Larco, Coroma and Pliocene ignimbrites, the first two being separated by the Quechua 2 orogeny. All these ignimbrites are very similar and correspond to peraluminous rhyolites to rhyodacites. In the studies area, the Coroma cycle is the only one where an ignimbrite-less evolved resurgent dome association can be observed. Beside these ignimbrites, isolated small lava flows and domes overlay and/or intrude all the other formations. They are meta-aluminous lavas with a shoshonitic affinity. A quaternary age can be attributed to his second volcanism. These two volcanic types are well-known in the CVZ and are related to the different deformation stages, either compressional or extensional, which occur alternately in the Cordillera since 26 Ma. (authors). 61 refs., 12 figs., 3 tabs

  2. Slab dehydration in Cascadia and its relationship to volcanism, seismicity, and non-volcanic tremor (United States)

    Delph, J. R.; Levander, A.; Niu, F.


    The characteristics of subduction beneath the Pacific Northwest (Cascadia) are variable along strike, leading to the segmentation of Cascadia into 3 general zones: Klamath, Siletzia, and Wrangelia. These zones show marked differences in tremor density, earthquake density, seismicity rates, and the locus and amount of volcanism in the subduction-related volcanic arc. To better understand what controls these variations, we have constructed a 3D shear-wave velocity model of the upper 80 km along the Cascadia margin from the joint inversion of CCP-derived receiver functions and ambient noise surface wave data using 900 temporary and permanent broadband seismic stations. With this model, we can investigate variations in the seismic structure of the downgoing oceanic lithosphere and overlying mantle wedge, the character of the crust-mantle transition beneath the volcanic arc, and local to regional variations in crustal structure. From these results, we infer the presence and distribution of fluids released from the subducting slab and how they affect the seismic structure of the overriding lithosphere. In the Klamath and Wrangelia zones, high seismicity rates in the subducting plate and high tremor density correlate with low shear velocities in the overriding plate's forearc and relatively little arc volcanism. While the cause of tremor is debated, intermediate depth earthquakes are generally thought to be due to metamorphic dehydration reactions resulting from the dewatering of the downgoing slab. Thus, the seismic characteristics of these zones combined with rather sparse arc volcanism may indicate that the slab has largely dewatered by the time it reaches sub-arc depths. Some of the water released during earthquakes (and possibly tremor) may percolate into the overriding plate, leading to slow seismic velocities in the forearc. In contrast, Siletzia shows relatively low seismicity rates and tremor density, with relatively higher shear velocities in the forearc

  3. Anti-Ma and anti-Ma2-associated paraneoplastic neurological syndromes. (United States)

    Ortega Suero, G; Sola-Valls, N; Escudero, D; Saiz, A; Graus, F

    Analyse the clinical profile, associated tumour types, and response to treatment of paraneoplastic neurological syndromes associated with antibodies against Ma proteins. A retrospective study of patients with antibodies against Ma proteins identified in a neuroimmunology laboratory of reference. Of the 32 patients identified, 20 showed reactivity against Ma2 only (anti-Ma2 antibodies), 11 against Ma1 and Ma2 (anti-Ma antibodies), and 1 with reactivity against Ma1 only (anti-Ma1 antibodies). The most common clinical presentations were limbic encephalopathy, diencephalic dysfunction, or brainstem encephalopathy, frequently appearing as a combination of these features. Three patients had isolated cerebellar dysfunction with anti-Ma antibodies, and 2 exhibited peripheral nervous system syndrome with anti-Ma2 antibodies. Testicular tumours were the most common neoplasms (40%) in the anti-Ma2 cases. In the group associated with anti-Ma1 antibodies, the most common were lung tumours (36%), followed by testicular tumours. All idiopathic cases were reactive to Ma2. The clinical outcome was significantly better in the anti-Ma2 group. The patient with anti-Ma1 presented with limbic encephalitis and brainstem dysfunction associated with lymphoepithelioma of the bladder. Specifically determining the different reactivities of anti-Ma protein antibodies in order to differentiate between Ma1 and Ma2 antibodies is important because anti-Ma2-associated paraneoplastic syndromes have a better outcome. Lastly, this study is the first to confirm that there may be cases that react exclusively to antibodies against Ma1. Copyright © 2016 Sociedad Española de Neurología. Publicado por Elsevier España, S.L.U. All rights reserved.

  4. Volcanic ash impacts on critical infrastructure (United States)

    Wilson, Thomas M.; Stewart, Carol; Sword-Daniels, Victoria; Leonard, Graham S.; Johnston, David M.; Cole, Jim W.; Wardman, Johnny; Wilson, Grant; Barnard, Scott T.


    Volcanic eruptions can produce a wide range of hazards. Although phenomena such as pyroclastic flows and surges, sector collapses, lahars and ballistic blocks are the most destructive and dangerous, volcanic ash is by far the most widely distributed eruption product. Although ash falls rarely endanger human life directly, threats to public health and disruption to critical infrastructure services, aviation and primary production can lead to significant societal impacts. Even relatively small eruptions can cause widespread disruption, damage and economic loss. Volcanic eruptions are, in general, infrequent and somewhat exotic occurrences, and consequently in many parts of the world, the management of critical infrastructure during volcanic crises can be improved with greater knowledge of the likely impacts. This article presents an overview of volcanic ash impacts on critical infrastructure, other than aviation and fuel supply, illustrated by findings from impact assessment reconnaissance trips carried out to a wide range of locations worldwide by our international research group and local collaborators. ‘Critical infrastructure’ includes those assets, frequently taken for granted, which are essential for the functioning of a society and economy. Electricity networks are very vulnerable to disruption from volcanic ash falls. This is particularly the case when fine ash is erupted because it has a greater tendency to adhere to line and substation insulators, where it can cause flashover (unintended electrical discharge) which can in turn cause widespread and disruptive outages. Weather conditions are a major determinant of flashover risk. Dry ash is not conductive, and heavy rain will wash ash from insulators, but light rain/mist will mobilise readily-soluble salts on the surface of the ash grains and lower the ash layer’s resistivity. Wet ash is also heavier than dry ash, increasing the risk of line breakage or tower/pole collapse. Particular issues for water

  5. Magnetic properties of frictional volcanic materials (United States)

    Kendrick, Jackie E.; Lavallée, Yan; Biggin, Andrew; Ferk, Annika; Leonhardt, Roman


    magnetisation (ARM), as expected for a thermal origin, the remanence of volcanic pseudotachylyte has been found to be comparable to an isothermal remanent magnetisation (IRM). Thus, the pseudotachylyte has experienced a strong magnetic field that overwrote the previous thermoremanent magnetisation of the magma, such as the strong local electric current that occurs in faults (e.g. Ferré et al., 2005). Additionally, the pseudotachylyte seems more often to comprise of uniaxial non-interacting single-domain particles compared to pseudo-single in the host, and to have a single Curie temperature whereas the host more commonly exhibits multiple phases. Differences in rock-magnetic parameters between the pseudotachylyte and host are significant, but not as high as those observed in granites by Nakamura et al. (2002) or Ferré et al. (2005), probably because granitic host rocks do not already carry a strong and stable remanence as do these extrusive volcanic rocks. The application of rock-magnetic tests in volcanology will undoubtedly continue to be a "go-to" tool for identification of pseudotachylytes, which are increasingly being recognised to play an important role in dome-building eruptions. Refs: Ferré, E.C., Zechmeister, M.S., Geissman, J.W., MathanaSekaran, N. and Kocak, K., 2005. The origin of high magnetic remanence in fault pseudotachylites: Theoretical considerations and implication for coseismic electrical currents. Tectonophysics, 402(1-4): 125-139. Nakamura, N., Hirose, T. and Borradaile, G.J., 2002. Laboratory verification of submicron magnetite production in pseudotachylytes: relevance for paleointensity studies. . Earth and Planetary Science Letters, 201(1): 13-18.

  6. New 40Ar / 39Ar age and geochemical data from seamounts in the Canary and Madeira volcanic provinces: Support for the mantle plume hypothesis (United States)

    Geldmacher, J.; Hoernle, K.; Bogaard, P. v. d.; Duggen, S.; Werner, R.


    The role of mantle plumes in the formation of intraplate volcanic islands and seamount chains is being increasingly questioned. Particular examples are the abundant and somewhat irregularly distributed island and seamount volcanoes off the coast of northwest Africa. New 40Ar / 39Ar ages and Sr-Nd-Pb isotope geochemistry of volcanic rocks from seamounts northeast of the Madeira Islands (Seine and Unicorn) and northeast of the Canary Islands (Dacia and Anika), however, provide support for the plume hypothesis. The oldest ages of shield stage volcanism from Canary and Madeira volcanic provinces confirm progressions of increasing age to the northeast. Average volcanic age progression of ∼1.2 cm/a is consistent with rotation of the African plate at an angular velocity of ∼0.20° ± 0.05 /Ma around a common Euler pole at approximately 56° N, 45° W computed for the period of 0-35 Ma. A Euler pole at 35° N, 45° W is calculated for the time interval of 35-64 Ma. The isotope geochemistry further confirms that the Madeira and Canary provinces are derived from different sources, consistent with distinct plumes having formed each volcanic group. Conventional hotspot models, however, cannot easily explain the up to 40 m.y. long volcanic history at single volcanic centers, long gaps in volcanic activity, and the irregular distribution of islands and seamounts in the Canary province. A possible explanation could involve interaction of the Canary mantle plume with small-scale upper mantle processes such as edge-driven convection. Juxtaposition of plume and non-plume volcanism could also account for observed inconsistencies of the classical hotspot concept in other volcanic areas.

  7. 33 CFR 80.135 - Hull, MA to Race Point, MA. (United States)


    ... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Hull, MA to Race Point, MA. 80... INTERNATIONAL NAVIGATION RULES COLREGS DEMARCATION LINES Atlantic Coast § 80.135 Hull, MA to Race Point, MA. (a... the east coast of Massachusetts from the easternmost radio tower at Hull, charted in approximate...

  8. Volcanology: Volcanic bipolar disorder explained (United States)

    Jellinek, Mark


    Eruptions come in a range of magnitudes. Numerical simulations and laboratory experiments show that rare, giant super-eruptions and smaller, more frequent events reflect a transition in the essential driving forces for volcanism.

  9. Lidar sounding of volcanic plumes (United States)

    Fiorani, Luca; Aiuppa, Alessandro; Angelini, Federico; Borelli, Rodolfo; Del Franco, Mario; Murra, Daniele; Pistilli, Marco; Puiu, Adriana; Santoro, Simone


    Accurate knowledge of gas composition in volcanic plumes has high scientific and societal value. On the one hand, it gives information on the geophysical processes taking place inside volcanos; on the other hand, it provides alert on possible eruptions. For this reasons, it has been suggested to monitor volcanic plumes by lidar. In particular, one of the aims of the FP7 ERC project BRIDGE is the measurement of CO2 concentration in volcanic gases by differential absorption lidar. This is a very challenging task due to the harsh environment, the narrowness and weakness of the CO2 absorption lines and the difficulty to procure a suitable laser source. This paper, after a review on remote sensing of volcanic plumes, reports on the current progress of the lidar system.

  10. Structural control of monogenetic volcanism in the Garrotxa volcanic field (Northeastern Spain) from gravity and self-potential measurements (United States)

    Barde-Cabusson, S.; Gottsmann, J.; Martí, J.; Bolós, X.; Camacho, A. G.; Geyer, A.; Planagumà, Ll.; Ronchin, E.; Sánchez, A.


    We report new geophysical observations on the distribution of subsurface structures associated with monogenetic volcanism in the Garrotxa volcanic field (Northern Spain). As part of the Catalan Volcanic Zone, this Quaternary volcanic field is associated with the European rifts system. It contains the most recent and best preserved volcanic edifices of the Catalan Volcanic Zone with 38 monogenetic volcanoes identified in the Garrotxa Natural Park. We conducted new gravimetric and self-potential surveys to enhance our understanding of the relationship between the local geology and the spatial distribution of the monogenetic volcanoes. The main finding of this study is that the central part of the volcanic field is dominated by a broad negative Bouguer anomaly of around -0.5 mGal, within which a series of gravity minima are found with amplitudes of up to -2.3 mGal. Inverse modelling of the Bouguer data suggests that surficial low-density material dominates the volcanic field, most likely associated with effusive and explosive surface deposits. In contrast, an arcuate cluster of gravity minima to the NW of the Croscat volcano, the youngest volcano of this zone, is modelled by vertically extended low-density bodies, which we interpret as a complex ensemble of fault damage zones and the roots of young scoria cones. A ground-water infiltration zone identified by a self-potential anomaly is associated with a steep horizontal Bouguer gravity gradient and interpreted as a fault zone and/or magmatic fissure, which fed the most recent volcanic activity in the Garrotxa. Gravimetric and self-potential data are well correlated and indicate a control on the locations of scoria cones by NNE-SSW and NNW-SSE striking tectonic features, which intersect the main structural boundaries of the study area to the north and south. Our interpretation of the data is that faults facilitated magma ascent to the surface. Our findings have major implications for understanding the relationship

  11. Time-related variation of volatile contents of Western Ghats volcanic formations, Deccan, India (United States)

    Marzoli, Andrea; Callegaro, Sara; Baker, Don R.; De Min, Angelo; Renne, Paul R.


    Deccan volcanism in India covered more than 1 million square km and reached a maximum thickness of about 3 km, as presently preserved in the Western Ghats volcanic lava piles. Volcanic activity started at about 66.4 Ma (Jawhar formation) and ended at about 65.5 Ma (Mahabaleshwar unit; Renne et al., 2015). Deccan volcanism straddled the Cretaceous-Paleogene boundary (ca. 66.0 Ma) and possibly contributed to the end-Cretaceous mass extinction event through emission of gases such as SO2, CO2, Cl, F that may have triggered global climate changes. Severe pollution by volcanic gases is supported by the high S and Cl contents (up to 1400 and up to 900 ppm, respectively; Self et al., 2008) measured in a few olivine- and plagioclase-hosted melt inclusions from the Jawhar, Neral, and Thakurvadi Formations (early lava flows, ca. 66.3-66.4 ± 0.1 Ma; Renne et al., 2015) and by magmatic S contents (up to 1800 ppm; Callegaro et al., 2014) calculated from S measurements in clinopyroxenes from the Mahabaleshwar unit (ca. 65.5 ± 0.1; Schoene et al., 2015). Here, we present new analyses of S, Cl, and F, obtained by ion-probe and synchrotron light micro-fluorescence analyses on clinopyroxenes and plagioclase phenocrysts from ?al? lava flow units of the Western Ghats. The volatile contents of the host magmas have been calculated from recently published clinopyroxene/basalt partition coefficients. These new data will describe the time-related variation of volatile elements hosted and eventually emitted by Deccan lavas and shed light on their environmental impact. References: Callegaro S. et al. (2014). Geology 42, 895-898. Renne P.R. et al. (2015). Science 350, 76-78. Schoene B. et al. (2015). Science 347, 192-184. Self S. et al. (2008). Science 319, 1654-1657.

  12. Volcanic eruption plumes on Io

    International Nuclear Information System (INIS)

    Strom, R.G.; Terrile, R.J.; Masursky, H.; Hansen, C.


    The detection of an umbrella-shaped plume extending about 280 km above the bright limb of Io was one of the most important discoveries made during the Voyager 1 encounter with the jovian system. This discovery proves that Io is volcanically active at present, and the number and magnitude of these eruptions indicate that Io is the most volcanically active body so far discovered in the Solar System. Preliminary analyses of these eruptive plumes are presented. (U.K.)

  13. Volcanic hazards and aviation safety (United States)

    Casadevall, Thomas J.; Thompson, Theodore B.; Ewert, John W.; ,


    An aeronautical chart was developed to determine the relative proximity of volcanoes or ash clouds to the airports and flight corridors that may be affected by volcanic debris. The map aims to inform and increase awareness about the close spatial relationship between volcanoes and aviation operations. It shows the locations of the active volcanoes together with selected aeronautical navigation aids and great-circle routes. The map mitigates the threat that volcanic hazards pose to aircraft and improves aviation safety.

  14. Late Cenozoic Samtskhe-Javakheti Volcanic Highland, Georgia:The Result of Mantle Plumes Activity (United States)

    Okrostsvaridze, Avtandil


    Late Cenozoic Samtskhe-Javakheti continental volcanic highland (1500-2500 m a.s.l) is located in the SW part of the Lesser Caucasus. In Georgia the highland occupies more than 4500 km2, however its large part spreads towards the South over the territories of Turkey and Armenia. One can point out three stages of magmatic activity in this volcanic highland: 1. Early Pliocene activity (5.2-2.8 Ma; zircons U-Pb age) - when a large part of the highland was built up. It is formed from volcanic lava-breccias of andesite-dacitic composition, pyroclastic rocks and andesite-basalt lava flow. The evidences of this structure are: a large volume of volcanic material (>1500 km3); big thickness (700-1100 m in average), large-scale of lava flows (length 35 km, width 2.5-3.5 km, thickness 30-80 m), big thickness of volcanic ash horizons (300 cm at some places) and big size of volcanic breccias (diameter >1 m). Based on this data we assume that a source of this structure was a supervolcano (Okrostsvaridze et al., 2016); 2. Early Pleistocene activity (2.4 -1.6 Ma; zircons U-Pb age) - when continental flood basalts of 100-300 m thickness were formed. The flow is fully crystalline, coarse-grained, which mainly consist of olivine and basic labradorite. There 143Nd/144Nd parameter varies in the range of +0.41703 - +0.52304, and 87Sr/88Sr - from 0.7034 to 0.7039; 3. Late Pleistocene activity (0.35-0.021 Ma; zircons U-Pb age) - when intraplate Abul-Samsari linear volcanic ridge of andesite composition was formed stretching to the S-N direction for 40 km with the 8-12 km width and contains more than 20 volcanic edifices. To the South of the Abul-Samsari ridge the oldest (0.35-0.30 Ma; zircons U-Pb age) volcano Didi Abuli (3305 m a.s.l.) is located. To the North ages of volcano edifices gradually increase. Farther North the youngest volcano Tavkvetili (0.021-0. 030 Ma) is located (2583 m a.s.l.). One can see from this description that the Abul-Samsari ridge has all signs characterizing

  15. Deuterium values from volcanic glass: A paleoelevation proxy for Oregon's Cascade Range (United States)

    Carlson, T. B.; Bershaw, J. T.


    Hydrated volcanic glass has been used as a proxy to constrain Cenozoic paleoclimate across many of the world's mountain ranges. However, there are concerns that volcanic glass may not preserve the isotopic composition of syndepositional meteoric water. The Cascades are an excellent location to study the validity of hydrated volcanic glass as a paleoenvironmental proxy for several reasons. Moisture is derived from a single oceanic source and falls as orographic precipitation in the Cascades, leading to a characteristic altitude effect, or inverse relationship between elevation and the isotopic composition of meteoric water (δD). In addition, past studies have inferred uplift of the Cascades and an increase in the rain shadow effect since the Eocene through independent methods such as changing fossil assemblages, and other isotopic proxies including carbonates and fossil teeth. In this study, δD values of two hydrated tuff samples are compared: one prior to ( 29 Ma) and one following ( 5 Ma) the onset of High Cascade volcanism. The isotopic composition of these samples are interpreted in the context of modern water across the range to understand the potential of volcanic glass as a proxy for paleoelevation in the Pacific Northwest.

  16. Geochronological constraints on Cretaceous-Paleocene volcanism in South Westland, New Zealand

    International Nuclear Information System (INIS)

    Phillips, C.J.; Cooper, A.F.; Palin, J.M.; Nathan, S.


    Cretaceous and Paleocene sedimentation in South Westland, New Zealand, is recorded in the Otumotu Formation, Tauperikaka Coal Measures, Whakapohai Sandstone, Arnott Basalt, Buttress Conglomerate, and Tokakoriri Formation, originally named and mapped by Nathan in 1977. Within this stratigraphic sequence, the name Buttress Conglomerate was used to describe volcanic conglomerates at Porphyry and Buttress Points that contained rounded clasts of plagioclasephyric intermediate volcanic rocks. Stratigraphically, the volcanic conglomerate at Porphyry Point forms sharp contacts with the underlying Arnott Basalt (Haumurian) and overlying Tokakoriri Formation (Teurian). The volcanic conglomerate at Buttress Point, however, is entirely fault-bounded. Clasts from each unit were collected and U-Pb zircon dated using the TIMS and ELA-ICP-MS methods. A trachyandesite clast collected at Buttress Point gives an age of 96.9 ± 1.6 Ma, whereas a rhyolite clast collected at Porphyry Point gives an age of 61.4 ± 0.8 Ma. Petrological, geochemical, and stratigraphic data suggest that erosion of the clasts closely followed volcanism, and that these ages accurately reflect the depositional ages of the conglomerates. Conglomerates at Porphyry and Buttress Points have been formally renamed the Porphyry Point Member of the Tokakoriri Formation and the Buttress Point Conglomerate, respectively. (author). 49 refs., 7 figs., 4 tabs

  17. Obama vu de ma banlieue.

    Directory of Open Access Journals (Sweden)

    Olga Stanislawska


    Full Text Available Une petite brocante est organisée tous les jeudis sur une place proche de la Basilique de Saint-Denis. On y vend des livres, des bibelots, des bijoux fantaisies et des masques africains. L’un des vendeurs a visiblement décidé de bénéficier de l’effet Obama. J’ai pris la photo de ma fenêtre, située au dessus de ce marché. J’ai adoré ce stand, mais ce n’est qu’une fois sur l’écran de mon ordinateur que j’ai vu les petites images Banania... ! Si j’avais su, je serais ...

  18. Correlations between silicic volcanic rocks of the St Mary's Islands (southwestern India) and eastern Madagascar

    DEFF Research Database (Denmark)

    Melluso, Leone; Sheth, Hetu C.; Mahoney, John J.


    The St Mary's, Islands (southwestern India) expose silicic volcanic and sub-volcanic rocks (rhyolites and granophyric dacites) emplaced contemporaneously with the Cretaceous igneous province of Madagascar, roughly 88-90 Ma ago. I he St Mary's Islands rocks have phenocrysts of plagioclase...... and isotopic Compositions very close to those of rhyolites exposed between Vatomandry Ilaka and Mananjary in eastern Madagascar, and are distinctly different from rhyolites front other sectors of the Madagascan province. We therefore postulate that the St Mary's and the Vatomandry-Ilaka Mananjary silicic rock...

  19. /sup 40/Ar//sup 39/Ar and K-Ar dating of altered glassy volcanic rocks: the Dabi Volcanics, P. N. G

    Energy Technology Data Exchange (ETDEWEB)

    Walker, D.A. (Australian National Univ., Canberra. Dept. of Geology); McDougall, I. (Australian National Univ., Canberra. Research School of Earth Sciences)


    K-Ar and /sup 40/Ar//sup 39/Ar ages have been determined for altered submarine tholeiitic and boninite (high-Mg andesite) lavas from the Dabi Volcanics, Cape Vogel Peninsula, Papua New Guinea. /sup 40/Ar//sup 39/Ar whole rock total fusion and plateau ages identify a Late Paleocene age for the tholeiitic lavas (58.9 +- 1.1 Ma), and also for the boninitic lavas (58.8 +- 0.8 Ma). Apparent K-Ar ages for the same samples range from 27.2 +- 0.7 to 63.9 +- 4.5 Ma, and young K-Ar ages for glassy boninites are probably due to variable radiogenic /sup 40/Ar(/sup 40/Ar*) loss. These new ages effectively reconcile previously ambiguous age data for the Dabi Volcanics, and indicate contemporaneous tholeiitic and boninitic volcanism occurring in southeast PNG during the Late Paleocene. Smectites, developed as alteration products after glass in oceanic lavas commonly do not retain /sup 39/Ar during or subsequent to irradiation, but in some cases may contain /sup 40/Ar*. The results are discussed.

  20. 40Ar/39Ar and K-Ar dating of altered glassy volcanic rocks: the Dabi Volcanics, P.N.G

    International Nuclear Information System (INIS)

    Walker, D.A.; McDougall, I.


    K-Ar and 40 Ar/ 39 Ar ages have been determined for altered submarine tholeiitic and boninite (high-Mg andesite) lavas from the Dabi Volcanics, Cape Vogel Peninsula, Papua New Guinea. 40 Ar/ 39 Ar whole rock total fusion and plateau ages identify a Late Paleocene age for the tholeiitic lavas (58.9 +- 1.1 Ma), and also for the boninitic lavas (58.8 +- 0.8 Ma). Apparent K-Ar ages for the same samples range from 27.2 +- 0.7 to 63.9 +- 4.5 Ma, and young K-Ar ages for glassy boninites are probably due to variable radiogenic 40 Ar( 40 Ar*) loss. These new ages effectively reconcile previously ambiguous age data for the Dabi Volcanics, and indicate contemporaneous tholeiitic and boninitic volcanism occurring in southeast PNG during the Late Paleocene. Smectites, developed as alteration products after glass in oceanic lavas commonly do not retain 39 Ar during or subsequent to irradiation, but in some cases may contain 40 Ar*. The results are discussed. (author)

  1. Petrography and geochemistry of lithic fragments in ignimbrites from the Mangakino Volcanic Centre : implications for the composition of the subvolcanic crust in western Taupo Volcanic Zone, New Zealand

    International Nuclear Information System (INIS)

    Krippner, S.J.P.; Briggs, R.M.; Wilson, C.J.N.; Cole, J.W.


    The Mangakino Volcanic Centre is the westernmost and oldest rhyolitic caldera volcano in the Taupo Volcanic Zone, North Island, New Zealand. The largest eruptions from Mangakino occurred in two periods of caldera-forming activity during the 1.68-1.53 Ma (Period I), and 1.21-0.95 Ma (Period IIA), producing several voluminous widespread welded and nonwelded ignimbrites and minor fall deposits. Other activity from Mangakino generated fall deposits and rhyolitic lava domes. Lithic fragments are common in all Mangakino ignimbrites (1-10 modal %), and consist of diverse lithologies including: rhyolite, dacite, andesite, and basaltic andesite lava, welded ignimbrite, tuff, volcanic breccia, biotite granite, granodiorite porphyry, siltstone, sandstone, greywacke, metagreywacke, metaconglomerate, biotite and hornblende-biotite schist. Lithic populations in Period I ignimbrites are dominated by andesite lavas, suggesting that there was a pre-existing andesite volcano in the Mangakino area, geochemically distinct from Titiraupenga and Pureora, the nearest roughly contemporaneous andesitic volcanoes. Later ignimbrites that erupted during Period IIA, contain predominantly rhyolitic lava lithics, implying that significant dome building activity occurred at Mangakino, which represented greater volumes of rhyolitic lava than previously described from the area. Petrographic, geochemical, and geophysical (density and magnetic susceptibility) data measured from the lithic fragments are used to propose a model for the shallow crust below Mangakino Volcanic Centre. This model postulates eruptions through a basement of Mesozoic biotite schists overlain by metagreywackes, a thin cover of Tertiary sandstones and siltsones, and an overlying volcanic succession of andesite, dacite and rhyolite lavas, welded ignimbrites, and lacustrine sediments. Ignimbrite eruptions incorporated comagmatic biotite granite fragments from the crystallised margins of the silicic magma chambers, and effectively

  2. MaGa, a web-based collaborative database for gas emissions: a tool to improve the knowledge on Earth degassing (United States)

    Frigeri, A.; Cardellini, C.; Chiodini, G.; Frondini, F.; Bagnato, E.; Aiuppa, A.; Fischer, T. P.; Lehnert, K. A.


    The study of the main pathways of carbon flux from the deep Earth requires the analysis of a large quantity and variety of data on volcanic and non-volcanic gas emissions. Hence, there is need for common frameworks to aggregate available data and insert new observations. Since 2010 we have been developing the Mapping Gas emissions (MaGa) web-based database to collect data on carbon degassing form volcanic and non-volcanic environments. MaGa uses an Object-relational model, translating the experience of field surveyors into the database schema. The current web interface of MaGa allows users to browse the data in tabular format or by browsing an interactive web-map. Enabled users can insert information as measurement methods, instrument details as well as the actual values collected in the field. Measurements found in the literature can be inserted as well as direct field observations made by human-operated instruments. Currently the database includes fluxes and gas compositions from active craters degassing, diffuse soil degassing and fumaroles both from dormant volcanoes and open-vent volcanoes from literature survey and data about non-volcanic emission of the Italian territory. Currently, MaGa holds more than 1000 volcanic plume degassing fluxes, data from 30 sites of diffuse soil degassing from italian volcanoes, and about 60 measurements from fumarolic and non volcanic emission sites. For each gas emission site, the MaGa holds data, pictures, descriptions on gas sampling, analysis and measurement methods, together with bibliographic references and contacts to researchers having experience on each site. From 2012, MaGa developments started to be focused towards the framework of the Deep Earth Carbon Degassing research initiative of the Deep Carbon Observatory. Whithin the DECADE initiative, there are others data systems, as EarthChem and the Smithsonian Institution's Global Volcanism Program. An interoperable interaction between the DECADE data systems is being

  3. Groundwater characteristics and problems in volcanic rock terrains

    International Nuclear Information System (INIS)

    Custodio, E.


    Volcanic rock formations, each with their own particular hydrogeological characteristics, occur in circumstances that cover a multiplicity of situations. These range from permeable porous rock formations to permeable fissured formations and include all types of intermediate situation between the two. The type of volcanism, distance from the source of emission, age, alteration processes and tectonics are all factors which determine their behaviour. Volcanic formations usually constitute a single aquifer system, even though this may be very heterogeneous and may locally be separated into clearly defined subunits. At times, formations may be hundreds of metres thick and are fairly permeable almost throughout. As a rule, volcanic material does not yield directly soluble salts to the water that flows through it. Mineralization of the water is due to the concentration of rainfall and the hydrolysis of silicates as a result of CO 2 being absorbed from the atmosphere and the ground, or as a result of volcanism itself. Cationic grouping is usually closely correlated to that of the rock formation in which the chemical composition is formed. Most environmental isotope and radioisotope techniques may be used, and at times are of unquestionable value. However, the existence of evaporation in the soil with possible isotopic fractionation, the effects of marked relief, the dilution of dissolved carbon by volcanic carbon and isotopic exchange brought about by volcanic carbon, etc., should be taken into account before valid conclusions are drawn. The paper uses examples taken from existing studies, mainly those being carried out in the Canary Islands (Spain). (author). 98 refs, 18 figs, 4 tabs

  4. Transition of magma genesis estimated by change of chemical composition of Izu-bonin arc volcanism associated with spreading of Shikoku Basin (United States)

    Haraguchi, S.; Ishii, T.


    Arc volcanism in the Izu-Ogasawara arc is separated into first and latter term at the separate of Shikoku Basin. Middle to late Eocene early arc volcanism formed a vast terrane of boninites and island arc tholeiites that is unlike active arc systems. A following modern-style arc volcanism was active during the Oligocene, along which intense tholeiitic and calc-alkaline volcanism continued until 29Ma, before spreading of the back- arc basin. The recent arc volcanism in the Izu-Ogasawara arc have started in the middle Miocene, and it is assumed that arc volcanism were decline during spreading of back-arc basin. In the northern Kyushu-Palau Ridge, submarine bottom materials were dredged during the KT95-9 and KT97-8 cruise by the R/V Tansei-maru, Ocean Research Institute, university of Tokyo, and basaltic to andesitic volcanic rocks were recovered during both cruise except for Komahashi-Daini Seamount where recovered acidic plutonic rocks. Komahashi-Daini Seamount tonalite show 37.5Ma of K-Ar dating, and this age indicates early stage of normal arc volcanism. These volcanic rocks are mainly cpx basalt to andesite. Two pyroxene basalt and andesite are only found from Miyazaki Seamount, northern end of the Kyushu-Palau Ridge. Volcanic rocks show different characteristics from first term volcanism in the Izu-Ogasawara forearc rise and recent arc volcanism. The most characteristic is high content of incompatible elements, that is, these volcanics show two to three times content of incompatible elements to Komahashi-Daini Seamount tonalite and former normal arc volcanism in the Izu outer arc (ODP Leg126), and higher content than recent Izu arc volcanism. This characteristic is similar to some volcanics at the ODP Leg59 Site448 in the central Kyushu- Palau Ridge. Site448 volcanic rocks show 32-33Ma of Ar-Ar ages, which considered beginning of activity of Parece Vela Basin. It is considered that the dredged volcanic rocks are uppermost part of volcanism before spreading of

  5. Nd and Sr isotopes and K-Ar ages of the Ulreungdo alkali volcanic rocks in the East Sea, South Korea

    Energy Technology Data Exchange (ETDEWEB)

    Kim Kyuhan; Jang Sunkyung [Ewha Womans Univ., Seoul (Korea); Tanaka, Tsuyoshi; Nagao, Keisuke


    Temporal geochemical and isotopical variations in the Ulreundgo alkali volcanic rocks provide important constraints on the origin and evolution of the volcanic rocks in relation to backarc basin tectonism. We determined the K-Ar ages, major and trace element contents, and Nd and Sr isotopic rations of the alkali volcanic rocks. The activities of Ulreungdo volcanoes can be divided, on the basis of radiometric ages and field occurrences, into five stages, though their activities range from 1.4 Ma to 0.01 Ma with short volcanic hiatus (ca. 0.05-0.3 Ma). The Nd-Sr isotopic data for Ulreungdo volcanic rocks enable us to conclude that: (1) the source materials of Ulreungdo volcanics are isotopically heterogeneous in composition, which is explained by the mixing of mantle derived magma and continental crustal source rocks. There is no systematic isotopic variations with eruption stages. Particularly, some volcanic rocks of stage 2 and 3 have extremely wide initial {sup 87}Sr/{sup 86}Sr isotopic variations ranging from 0.7038 to 0.7092, which are influenced by seawater alterations; (2) the Ulreungdo volcanic rocks show EMI characteristic, while volcanic rocks from the Jejudo, Yeong-il and Jeon-gok areas have slightly depleted mantle source characteristics; (3) the trachyandesite of the latest eruption stage was originated from the mantle source materials which differ from other stages. A schematic isotopic evolution model for alkali basaltic magma is presented in the Ulreungdo volcanic island of the backarc basin of Japanese island arc system. (author)

  6. Climatic impact of volcanic eruptions (United States)

    Rampino, Michael R.


    Studies have attempted to 'isolate' the volcanic signal in noisy temperature data. This assumes that it is possible to isolate a distinct volcanic signal in a record that may have a combination of forcings (ENSO, solar variability, random fluctuations, volcanism) that all interact. The key to discovering the greatest effects of volcanoes on short-term climate may be to concentrate on temperatures in regions where the effects of aerosol clouds may be amplified by perturbed atmospheric circulation patterns. This is especially true in subpolar and midlatitude areas affected by changes in the position of the polar front. Such climatic perturbation can be detected in proxy evidence such as decrease in tree-ring widths and frost rings, changes in the treeline, weather anomalies, severity of sea-ice in polar and subpolar regions, and poor grain yields and crop failures. In low latitudes, sudden temperature drops were correlated with the passage overhead of the volcanic dust cloud (Stothers, 1984). For some eruptions, such as Tambora, 1815, these kinds of proxy and anectdotal information were summarized in great detail in a number of papers and books (e.g., Post, 1978; Stothers, 1984; Stommel and Stommel, 1986; C. R. Harrington, in press). These studies lead to the general conclusion that regional effects on climate, sometimes quite severe, may be the major impact of large historical volcanic aerosol clouds.

  7. Rate of volcanism on Venus

    International Nuclear Information System (INIS)

    Fegley, B. Jr.; Prinn, R.G.


    The maintenance of the global H 2 SO 4 clouds on Venus requires volcanism to replenish the atmospheric SO 2 which is continually being removed from the atmosphere by reaction with calcium minerals on the surface of Venus. The first laboratory measurements of the rate of one such reaction, between SO 2 and calcite (CaCO 3 ) to form anhydrite (CaSO 4 ), are reported. If the rate of this reaction is representative of the SO 2 reaction rate at the Venus surface, then we estimate that all SO 2 in the Venus atmosphere (and thus the H 2 SO 4 clouds) will be removed in 1.9 million years unless the lost SO 2 is replenished by volcanism. The required rate of volcanism ranges from about 0.4 to about 11 cu km of magma erupted per year, depending on the assumed sulfur content of the erupted material. If this material has the same composition as the Venus surface at the Venera 13, 14 and Vega 2 landing sites, then the required rate of volcanism is about 1 cu km per year. This independent geochemically estimated rate can be used to determine if either (or neither) of the two discordant (2 cu km/year vs. 200 to 300 cu km/year) geophysically estimated rates is correct. The geochemically estimated rate also suggests that Venus is less volcanically active than the Earth

  8. Volcanic Eruptions in Kamchatka (United States)


    [figure removed for brevity, see original site] [figure removed for brevity, see original site] Sheveluch Stratovolcano Click on the image for full resolution TIFF Klyuchevskoy Stratovolcano Click on the image for full resolution TIFF One of the most volcanically active regions of the world is the Kamchatka Peninsula in eastern Siberia, Russia. It is not uncommon for several volcanoes to be erupting at the same time. On April 26, 2007, the Advanced Spaceborne Thermal Emission and Reflection Radioneter (ASTER) on NASA's Terra spacecraft captured these images of the Klyuchevskoy and Sheveluch stratovolcanoes, erupting simultaneously, and 80 kilometers (50 miles) apart. Over Klyuchevskoy, the thermal infrared data (overlaid in red) indicates that two open-channel lava flows are descending the northwest flank of the volcano. Also visible is an ash-and-water plume extending to the east. Sheveluch volcano is partially cloud-covered. The hot flows highlighted in red come from a lava dome at the summit. They are avalanches of material from the dome, and pyroclastic 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

  9. K-Ar ages of the Nyuto-Takakura volcanic products, southern part of the Sengan geothermal area, northeast Japan

    International Nuclear Information System (INIS)

    Suto, Shigeru; Uto, Kozo; Uchiumi, Shigeru


    The K-Ar age determination of the volcanic rocks from the Nyuto-Takakura volcano group, northeast Japan, was carried out. Nyuto-Takakura volcanoes are situated in the southern part of the Sengan geothermal area. And the Young Volcanic Rocks in the area were already divided into the Early stage volcanics (erupted in Matsuyama reversed epoch or more older epoch) and the Later stage volcanics (erupted in Brunhes normal epoch) by accumulated paleomagnetic and K-Ar age data. The results in this study are as follows; Nyuto Volcano: 0.63±0.06, 0.36±0.07 Ma, Sasamoriyama Volcano: 0.09±0.07, 0.3±0.3 Ma, Marumori Lava Dome: 0.4±0.3, 0.31±0.12 Ma, Mikadoyama Lava Dome: <1 Ma, Takakurayama-Kotakakurayama volcano: 1.4±0.5, 1.0±0.4, <0.4 Ma. The determinated ages are concordant with the volcanic stratigraphy and the paleomagnetic data. Nyuto Volcano, Sasamoriyama Volcano, Marumori Lava Dome, Mikadoyama Lava Dome and upper part of the Takakurayama-Kotakakurayama Volcano are interpreted to be erupted in Brunhes normal epoch. The volcanic rocks from the lower part of the Takakurayama-Kotakakurayama volcano show normal magnetic polarity, so they are interpreted to be erupted in Jaramillo normal polarity event. The Early stage volcanics and the Later stage volcanics in the studied area are tend to be distributed in the central part and the outer part of the area, respectively. But the determinated ages in this study show that there is no simple migration of the eruption center of the volcanic rocks from the central part to the peripheral part. There is no geothermal manifestation or alteration area around the Sasamoriyama Volcano and the Marumori Lava Dome, which are the youngest volcanoes in the studied area. So it is concluded that there is no direct correlation between the eruption age of the nearest volcano and the geothermal activity. (author)

  10. Effects of heat-flow and hydrothermal fluids from volcanic intrusions on authigenic mineralization in sandstone formations

    Directory of Open Access Journals (Sweden)

    Wolela Ahmed


    Full Text Available Volcanic intrusions and hydrothermal activity have modified the diagenetic minerals. In the Ulster Basin, UK, most of the authigenic mineralization in the Permo-Triassic sandstones pre-dated tertiary volcanic intrusions. The hydrothermal fluids and heat-flow from the volcanic intrusions did not affect quartz and feldspar overgrowths. However, clay mineral-transformation, illite-smectite to illite and chlorite was documented near the volcanic intrusions. Abundant actinolite, illite, chlorite, albite and laumontite cementation of the sand grains were also documented near the volcanic intrusions. The abundance of these cementing minerals decreases away from the volcanic intrusions.In the Hartford Basin, USA, the emplacement of the volcanic intrusions took place simultaneous with sedimentation. The heat-flow from the volcanic intrusions and hydrothermal activity related to the volcanics modified the texture of authigenic minerals. Microcrystalline mosaic albite and quartz developed rather than overgrowths and crystals near the intrusions. Chlorite clumps and masses were also documented with microcrystalline mosaic albite and quartz. These features are localized near the basaltic intrusions. Laumontite is also documented near the volcanic intrusions. The reservoir characteristics of the studied sandstone formations are highly affected by the volcanic and hydrothermal fluids in the Hartford and the Ulster Basin. The porosity dropped from 27.4 to zero percent and permeability from 1350 mD to 1 mD.

  11. Metallogenetic regularity exploration model and prospecting potential of the mesocenozoic volcanic type uranium deposit in the east of south China

    International Nuclear Information System (INIS)

    Wang Yusheng; Li Wenjun


    During the Meso-Cenozoic era, the crust in the east of South China experienced an evolutional process of compression-relaxed extension-local disintegration, correspondingly, three periods of volcanic activity were developed, forming initial volcanic cycle, principal volcanic cycle and caldera volcanic cycle. The caldera volcanic cycle was expressed as a 'bimodal type' rock suite, indicating the entering of the region into an evolutional stage of new embryonic refitting. The volcanic type uranium deposit is characterized by ore-formation during caldera volcanic cycle, ore control by the mobile belt of caldera volcanic cycle and double superposition and concentration, and it can be summarized as a new unconformity-related type uranium deposit of caldera volcanic series, which is divided into three morphological types: body type, layer type and vein type and relevant exploration models are proposed. The new unconformity-related type uranium deposits of the caldera volcanic series in the east of South China have a great prospecting potential. The tectonomagmatic complex area of the caldera volcanic cycle developed on the granite basement is the favourable target area in searching for large uranium deposits from now on

  12. Geologic field-trip guide to the volcanic and hydrothermal landscape of the Yellowstone Plateau (United States)

    Morgan Morzel, Lisa Ann; Shanks, W. C. Pat; Lowenstern, Jacob B.; Farrell, Jamie M.; Robinson, Joel E.


    Yellowstone National Park, a nearly 9,000 km2 (~3,468 mi2) area, was preserved in 1872 as the world’s first national park for its unique, extraordinary, and magnificent natural features. Rimmed by a crescent of older mountainous terrain, Yellowstone National Park has at its core the Quaternary Yellowstone Plateau, an undulating landscape shaped by forces of late Cenozoic explosive and effusive volcanism, on-going tectonism, glaciation, and hydrothermal activity. The Yellowstone Caldera is the centerpiece of the Yellowstone Plateau. The Yellowstone Plateau lies at the most northeastern front of the 17-Ma Yellowstone hot spot track, one of the few places on Earth where time-transgressive processes on continental crust can be observed in the volcanic and tectonic (faulting and uplift) record at the rate and direction predicted by plate motion. Over six days, this field trip presents an intensive overview into volcanism, tectonism, and hydrothermal activity on the Yellowstone Plateau (fig. 1). Field stops are linked directly to conceptual models related to monitoring of the various volcanic, geochemical, hydrothermal, and tectonic aspects of the greater Yellowstone system. Recent interest in young and possible future volcanism at Yellowstone as well as new discoveries and synthesis of previous studies, (for example, tomographic, deformation, gas, aeromagnetic, bathymetric, and seismic surveys), provide a framework in which to discuss volcanic, hydrothermal, and seismic activity in this dynamic region.

  13. The Riscos Bayos Ignimbrites of the Caviahue-Copahue volcanic caldera complex, southern Andes, Argentina (United States)

    Colvin, A.; Merrill, M.; Demoor, M.; Goss, A.; Varekamp, J. C.


    The Caviahue-Copahue volcanic complex (38 S, 70 W) is located on the eastern margin of the active arc in the southern Andes, Argentina. Volcán Copahue, an active stratovolcano which hosts an active hydrothermal system, sits on the southwestern rim of the elliptical Caviahue megacaldera (17 x 15 km). The caldera wall sequences are up to 0.6 km thick and consist of lavas with 51 -69 percent SiO2 and 0.2 - 5 percent MgO as well as breccias, dikes, sills, domes and minor ignimbrites. Andesitic lava flows also occur within the caldera, and are overlain by a chaotic complex of silicic lava and intracaldera pyroclastic flow deposits. The eastern wall sequence is capped by several extracaldera ignimbrites (Riscos Bayos formation) of about 50 m maximum thickness which extend 30 km east-southeast of the caldera. Young back-arc alkali basalt scoria cones occur east of the Caviahue-Copahue volcanic complex. The eruption of the Riscos Bayos formation at about 1.1 Ma (12 km cubed) may be related to the Caviahue caldera formation, though the Riscos Bayos account for only about 7 percent of the caldera volume. The Riscos Bayos consists of three lithic-bearing flow units: a grey basal flow, a tan middle flow and a bright-white, highly indurated uppermost flow. The basal unit consists of white and grey pumice fragments, black scoria clasts, black obsidian clasts (which give it the grey color), and accidental volcanic lithics set in a matrix of ash and crystals. The middle unit is composed of large mauve pumice fragments and accidental lithics set in a fine tan ash groundmass. The uppermost unit is composed of small pink and white pumice fragments set in a matrix of fine white ash. These pumices carry quartz and biotite crystals, whereas the lower two units are orthopyroxene-bearing trachy-dacites. The Caviahue-Copahue magmas all bear arc signatures, but possibly some magma mixing between the andesitic arc magmas and basaltic back-arc magmas may have occurred. The evolved top layer

  14. The SHRIMP zircon U-Pb dating of felsic volcanic rocks and its geological significance from yutian group in southern jiangxi

    International Nuclear Information System (INIS)

    Ji Chunyu; Wu Jianhua


    Past researches have showed that the Rb-Sr isochron ages of felsic end member for r hyolite-basalt b imodal volcanic rocks of Yutian Group in the Changpu and Longnan Basin in Southern Jiangxi Province are 175 ∼ 148 Ma, not only does its amplitude change more significantly, but it does not match with the Rb-Sr isochron ages (179 ∼ 173 Ma) of basic end member. As a result, I choose a method of zircon U-Pb dating with a higher accuracy, to obtain the rhyolite in the bottom of bimodal volcanic rocks in the Changpu Basin and the dacite in the top of of bimodal volcanic rocks in the Longnan Basin, whose zircon SHIRMP U-Pb age are respectively (195.2 ± 2.8) Ma and (191 ± 1.7) Ma. What's more, they are both almost the same in the error limit. It shows that the bimodal volcanic rocks in these both two basins are the product of the same session of magma movement. Simultaneously, it explains they form in a flash during the eruption intervals. According to the the newest International Stratigraphic Chart (Gradsrein et al. , 2004), in terms of geological age, the bimodal volcanic rocks in Changpu Basin and Longnan Basin, belonging to the early Early Jurassic. The zircon SHIRMP U-Pb age are distinctly older than the whole-rock Rb-Sr isochron age, it is probably because of the deviation of the dating method for the wholerock Rb-Sr isochron age. The zircon SHIRMP U-Pb age of bimodal volcanic rocks are 191 ∼ 195 Ma in Southern Jiangxi Province, which indicates that there had been an extensional environment. And after the bimodal volcanic activity, The zircon SHIRMP U-Pb age of felsic volcanic rocks are 145 ∼ 130 Ma. Both of the ages shows a as long as 45 Ma quiet period between 190 Ma and 145 Ma. It is unreasonable possible to interpreted by the single pattern of pacific plate subducting to eurasian plate. (authors)

  15. Properties of volcanic soils in cold climate conditions (United States)

    Kuznetsova, Elena


    Layers of volcanic ash and the Andosol soils derived from them may play an important role in preserving snow and ice as well as developing permafrost conditions in the immediate vicinity of volcanoes of high elevation or those situated at high latitudes, and land areas, often distant from volcanic activity that are either prone to permafrost or covered by snow and ice, but are affected by the deposition of subaerial ash. The special properties of volcanic ash that are responsible are critically reviewed particularly in relation to recent research in Kamchatka in the Far East of Russia. Of particular importance are the thermal properties and the unfrozen water contents of ash layers and the rate at which the weathering of volcanic glass takes place. Volcanic glass is the most easily weathered component of volcanic ejecta (Shoji et al., 1993; Kimble et al., 2000). There are many specific environmental conditions, including paleoclimate and present-day climate, the composition of volcanic tephra and glaciation history, which cause the differences in weathering and development of volcanic ash soils (Zehetner et al., 2003). The preservation of in situ, unweathered, and unaltered surficial ash-fall deposits in the cold regions has important implications for paleoclimate and glacial history. Ash-fall deposits, which trap and preserve the soils, sediments, and landforms on which they fall, can be used to resolve local climate conditions (temperature and moisture) at the ash site during ash-fall deposition. The preservation of detailed sedimentary features (e.g. bedding in the ash, sharpness of stratigraphic contacts) can tell us about their post-depositional history, whether they have been redeposited by wind or water, or overridden by glaciers (Marchant et al., 1996). Weathering of volcanic glass results in the development of amorphous clay minerals (e.g. allophane, opal, palagonite) but this takes place much slower in cold than under warmer climate conditions. Only few

  16. Volcanic eruptions and solar activity (United States)

    Stothers, Richard B.


    The historical record of large volcanic eruptions from 1500 to 1980 is subjected to detailed time series analysis. In two weak but probably statistically significant periodicities of about 11 and 80 yr, the frequency of volcanic eruptions increases (decreases) slightly around the times of solar minimum (maximum). Time series analysis of the volcanogenic acidities in a deep ice core from Greenland reveals several very long periods ranging from about 80 to about 350 yr which are similar to the very slow solar cycles previously detected in auroral and C-14 records. Solar flares may cause changes in atmospheric circulation patterns that abruptly alter the earth's spin. The resulting jolt probably triggers small earthquakes which affect volcanism.

  17. The Lathrop Wells volcanic center

    International Nuclear Information System (INIS)

    Crowe, B.; Morley, R.


    The Lathrop Wells volcanic center is located 20 km south of the potential Yucca Mountain site, at the south end of the Yucca Mountain range. This paper discusses a detailed Study Plan which was prepared describing planned geochronology and field studies to assess the chronology of the Lathrop Wells volcanic center and other Quaternary volcanic centers in the region. A paper was published discussing the geomorphic and soil evidence for a late Pleistocene or Holoceno age for the main cone of the center. The purpose of this paper was to expose the ideas concerning the age of the Lathrop Wells center to scientific scrutiny. Additionally, field evidence was described suggesting the Lathrop Wells center may have formed from multiple eruptive events with significant intervals of no activity between events. This interpretation breaks with established convention in the volcanological literature that small volume basalt centers are monogenetic

  18. Gold-silver mining districts, alteration zones, and paleolandforms in the Miocene Bodie Hills Volcanic Field, California and Nevada (United States)

    Vikre, Peter G.; John, David A.; du Bray, Edward A.; Fleck, Robert J.


    The Bodie Hills is a ~40 by ~30 kilometer volcanic field that straddles the California-Nevada state boundary between Mono Lake and the East Walker River. Three precious metal mining districts and nine alteration zones are delineated in Tertiary-Quaternary volcanic and Mesozoic granitic and metamorphic rocks that comprise the volcanic field. Cumulative production from the mining districts, Bodie, Aurora, and Masonic, is 3.4 million ounces of gold and 28 million ounces of silver. Small amounts of mercury were produced from the Potato Peak, Paramount-Bald Peak, and Cinnabar Canyon-US 395 alteration zones; a native sulfur resource in the Cinnabar Canyon-US 395 alteration zone has been identified by drilling. There are no known mineral resources in the other six alteration zones, Red Wash-East Walker River, East Brawley Peak, Sawtooth Ridge, Aurora Canyon, Four Corners, and Spring Peak. The mining districts and alteration zones formed between 13.4 and 8.1 Ma in predominantly ~15–9 Ma volcanic rocks of the Bodie Hills volcanic field. Ages of hydrothermal minerals in the districts and zones are the same as, or somewhat younger than, the ages of volcanic host rocks.

  19. Linking Volcanism and Gas Release from the North East Atlantic Volcanic Province to the PETM: Challenges and Updates (United States)

    Svensen, H.; Jones, M. T.; Jerram, D. A.; Planke, S.; Kjoberg, S.; Schmid, D. W.; Iyer, K.; Tegner, C.


    The main phase of the development of the North East Atlantic Volcanic Province took place about 56 Ma and coincides with the Paleocene Eocene Thermal Maximum (PETM). The volcanic activity was characterized by voluminous flood basalts, large plutonic complexes, sub-marine eruptions, widespread tephra deposition, and emplacement of sills and dikes along the continental margins of Norway, Greenland, Ireland, and the UK. Here we review the style and tempo of volcanism during this important period of Earth's history and discuss the sources and volumes of the carbon gases emitted to the ocean and atmosphere. Moreover, we present new data and models from 1) West Greenland showing the impact on sill intrusions on gas generation from heated Cretaceous mudstones, 2) a 3D seismic survey of gas release structures offshore Norway, and 3) Paleocene-Eocene tephra layers from Svalbard and Denmark. Gas migrated out of the contact aureoles by either explosive venting or by slower seepage towards the seafloor as demonstrated by 3D seismic data. Some of the gas was permanently trapped (dry gas and CO2-rich gas) in the source rocks and aureoles. Combined with high-precision zircon ages and a time model for the PETM, our approach may give robust fluxes that can explain both the onset and the body of the PETM.

  20. Inside the volcanic boiler room: knowledge exchange among stakeholders of volcanic unrest (United States)

    Gottsmann, Joachim; Christie, Ryerson; Bretton, Richard


    The knowledge of the causative links between subsurface processes, resulting monitoring signals and imminent eruption is incomplete. As a consequence, hazard assessment and risk mitigation strategies are subject to uncertainty. Discussion of unrest and pre-eruptive scenarios with uncertain outcomes are central during the discourse between a variety of stakeholders in volcanic unrest including scientists, emergency managers, policy makers and the public. Drawing from research within the EC FP7 VUELCO project, we argue that knowledge exchange amongst the different stakeholders of volcanic unrest evolves along three dimensions: 1) the identification of knowledge holders (including local communities) and their needs and expectations, 2) vehicles of communication and 3) trust. In preparing products that feed into risk assessment and management, scientists need to ensure that their deliverables are timely, accurate, clear, understandable and cater to the expectations of emergency managers. The means and content of communication amongst stakeholders need to be defined and adhered to. Finally, efficient and effective interaction between stakeholders is ideally based on mutual trust between those that generate knowledge and those that receive knowledge. For scientists, this entails contextualising volcanic hazard and risk in the framework of environmental and social values. Periods of volcanic quiescence are ideally suited to test established protocols of engagement between stakeholders in preparation for crises situations. The different roles of stakeholders and associated rules of engagement can be scrutinised and reviewed in antecessum rather than ad-hoc during a crisis situation to avoid issues related to distrust, loss of credibility and overall poor risk management. We will discuss these themes drawing from exploitation of research results from Mexico and Ecuador.

  1. Hydrothermal uranium vein deposits in Marysvale volcanic field, Utah

    International Nuclear Information System (INIS)

    Rasmussen, J.D.; Cunningham, C.G.; Steven, T.A.; Rye, R.O.; Romberger, S.B.


    Hydrothermal uranium veins are exposed over a 300 m (980 ft) vertical range in mines of the Central Mining area, near Marysvale, Utah. They cut 23 Ma quartz monzonite, 21 Ma granite, and 19 Ma rhyolite ash-flow tuff. The veins formed 18-19 Ma, in an area 1 km (0.6 mi) across, above the center of a composite magma chamber at least 12 x 6 km across that fed a sequence of 21-14 Ma hypabyssal granitic stocks, and rhyolitic lava flows, ash-flow tuffs, and volcanic domes. Intrusive pressure uplifted and fractured the roof; molybdenite-bearing, uranium-rich glassy dikes were intruded; and a breccia pipe and uranium-bearing veins were formed. The veins appear to have been deposited near the surface above a concealed rhyolite stock, where they filled high-angle fault zones and flat-lying to concave-downward pull-apart fractures. Low pH and fO 2 hydrothermal fluids at temperatures near 200 0 C (392 0 F) permeated the fractured rocks; these fluids were rich in fluorine and potassium, and contained uranium as uranous-fluoride complexes. Fluid-wall rock interaction increased fluid pH, causing precipitation of uranium minerals. At the deepest exposed levels, wall rocks were altered to kaolinite and sericite, and uraninite, coffinite, jordisite, fluorite, molybdenite, quartz, and pyrite (with delta 34 S near zero per mil) were deposited. The fluids were progressively oxidized higher in the system; iron in the wall rocks was oxidized to hematite, and sooty uraninite and umohoite were deposited

  2. Recurrence models of volcanic events: Applications to volcanic risk assessment

    International Nuclear Information System (INIS)

    Crowe, B.M.; Picard, R.; Valentine, G.; Perry, F.V.


    An assessment of the risk of future volcanism has been conducted for isolation of high-level radioactive waste at the potential Yucca Mountain site in southern Nevada. Risk used in this context refers to a combined assessment of the probability and consequences of future volcanic activity. Past studies established bounds on the probability of magmatic disruption of a repository. These bounds were revised as additional data were gathered from site characterization studies. The probability of direct intersection of a potential repository located in an eight km 2 area of Yucca Mountain by ascending basalt magma was bounded by the range of 10 -8 to 10 -10 yr -1 2 . The consequences of magmatic disruption of a repository were estimated in previous studies to be limited. The exact releases from such an event are dependent on the strike of an intruding basalt dike relative to the repository geometry, the timing of the basaltic event relative to the age of the radioactive waste and the mechanisms of release and dispersal of the waste radionuclides in the accessible environment. The combined low probability of repository disruption and the limited releases associated with this event established the basis for the judgement that the risk of future volcanism was relatively low. It was reasoned that that risk of future volcanism was not likely to result in disqualification of the potential Yucca Mountain site

  3. Age progressive volcanism opposite Nazca plate motion: Insights from seamounts on the northeastern margin of the Galapagos Platform (United States)

    Sinton, Christopher W.; Hauff, Folkmar; Hoernle, Kaj; Werner, Reinhard


    We present new geochemical and 40Ar/39Ar analyses from seven seamounts located off the northeastern margin of the shallow Galápagos Platform. Initial volcanism at 5.2 Ma created a small island (Pico) over the current location of the hotspot with geochemically enriched lavas. There is no further record of magmatism in the study area until 3.8 to 2.5 Ma, during which four roughly conical volcanoes (Sunray, Grande, Fitzroy, and Beagle) formed through eruption of lavas derived from a depleted mantle source. Sunray, Fitzroy, and Grande were islands that existed for 3 m.y. ending with the submergence of Fitzroy at 0.5 Ma. The youngest seamounts, Largo and Iguana, do not appear to have been subaerial and were active at 1.3 Ma and 0.5 Ma, respectively, with the style of edifice changing from the previous large cones to E-W elongate, composite structures. The progression of magmatism suggests that Pico erupted near 91.5°W near the location of the Galápagos plume while the others formed well east of the plume center. If the locations of initial volcanism are calculated using the eastward velocity of the Nazca plate, there appears to be a progression of younger volcanism toward the east, opposite what would be expected from a fixed mantle plume source. The rate that initial volcanism moves eastward is close to the plate velocity. A combination of higher temperature and geochemical enrichment of the thickened lithosphere of the Galápagos platform could have provided a viscosity gradient at the boundary between the thick lithosphere and the thinner oceanic lithosphere to the northeast. As this boundary moved eastward with the Nazca plate, it progressively triggered shear-driven mantle upwelling and volcanism.

  4. The Volcanism Ontology (VO): a model of the volcanic system (United States)

    Myer, J.; Babaie, H. A.


    We have modeled a part of the complex material and process entities and properties of the volcanic system in the Volcanism Ontology (VO) applying several top-level ontologies such as Basic Formal Ontology (BFO), SWEET, and Ontology of Physics for Biology (OPB) within a single framework. The continuant concepts in BFO describe features with instances that persist as wholes through time and have qualities (attributes) that may change (e.g., state, composition, and location). In VO, the continuants include lava, volcanic rock, and volcano. The occurrent concepts in BFO include processes, their temporal boundaries, and the spatio-temporal regions within which they occur. In VO, these include eruption (process), the onset of pyroclastic flow (temporal boundary), and the space and time span of the crystallization of lava in a lava tube (spatio-temporal region). These processes can be of physical (e.g., debris flow, crystallization, injection), atmospheric (e.g., vapor emission, ash particles blocking solar radiation), hydrological (e.g., diffusion of water vapor, hot spring), thermal (e.g., cooling of lava) and other types. The properties (predicates) relate continuants to other continuants, occurrents to continuants, and occurrents to occurrents. The ontology also models other concepts such as laboratory and field procedures by volcanologists, sampling by sensors, and the type of instruments applied in monitoring volcanic activity. When deployed on the web, VO will be used to explicitly and formally annotate data and information collected by volcanologists based on domain knowledge. This will enable the integration of global volcanic data and improve the interoperability of software that deal with such data.

  5. Diffuse Carbon Dioxide Degassing Monitoring at Santa Ana-Izalco-Coatepeque Volcanic System, El Salvador, Central America (United States)

    Olmos, R.; Barahona, F.; Cartagena, R.; Soriano, T.; Salazar, J.; Hernandez, P.; Perez, N.; Notsu, K.; Lopez, D.


    Santa Ana volcanic complex (0.22 Ma), located 40 Km west of San Salvador, comprises Santa Ana, Izalco, and Cerro Verde stratovolcanoes, the Coatepeque collapse caldera, as well as several cinder cones and explosion craters. Most recent activity has occurred at Izalco (1966) and Santa Ana which shows a permanent acidic crater lake with an intense fumarolic activity. In addition, Santa Ana exhibits a SO2-rich rising plume though no local seismicity has been reported. Weak fumarolic activity is also present at two locations within the Santa Ana volcanic complex: the summit crater of Izalco and Cerro Pacho at Coatepeque caldera. Other important structural features of this volcanic complex are two fault/fissure systems running NNW-SSE that can be identified by the alignment of the stratovolcanoes and numerous cinder cones and explosion craters. In January 2001, a 7.6 magnitude earthquake occurred about 150 Km SE of Santa Ana volcano. A soil gas and CO2 efflux survey was performed to evaluate the impact of this seismic event upon the diffuse degassing rates in Santa Ana volcanic complex in March 2001. A total of 450 soil gas and diffuse CO2 efflux measurements were carried out covering an area of 209.5 Km2. CO2 efflux ranged from non-detectable values to 293 gm-2d-1, with a median of 8.9 gm-2d-1 and an upper quartile of 5.2 gm-2d-1. The CO2 efflux spatial distribution reveals the existence of areas with CO2 efflux higher than 60 gm-2d-1 associated to the fault/fissure systems of NNW-SSE orientation. One of these areas, Cerro Pacho, was selected for the continuous monitoring of diffuse CO2 efflux in late May 2001. Secular variations of diffuse CO2 efflux ranged from 27.4 to 329 gm-2d-1 with a median of 130 gm-2d-1 and a quartile range of 59.3 gm-2d-1. An increasing trend of 43 gm-2d-1 was observed between May and August 2001 overlapped to high-frequency minor fluctuations related to meteorological variables' changes. However, a larger observation time-span is needed to

  6. Late Miocene marine tephra beds : recorders of rhyolitic volcanism in North Island, New Zealand

    International Nuclear Information System (INIS)

    Shane, P.; Black, T.; Eggins, S.; Westgate, J.


    A deep-sea sequence of 72 rhyolitic tephra beds, now exposed at Mahia Peninsula in the Hawke's Bay region of the east coast, North Island, New Zealand, provides a record of Late Miocene volcanism of the Coromandel Volcanic Zone (CVZ): the precursor to large-scale explosive volcanism of the Quaternary Taupo Volcanic Zone (TVZ). The geochemical signature of the glasses in the Miocene tephra has been protected from hydrothermal alteration and prolonged subaerial exposure that have affected proximal CVZ deposits. The tephra beds are primarily eruption-driven sediment gravity flows that have been emplaced into a trench-slope basin, some 300 km from active volcanoes. Their occurrence is consistent with long-distance fluvial transport followed by a point-source discharge into the deep-sea environment, and has no implications for the paleogeographic location of the basins relative to the volcanic arc. The tephra beds are calc-alkaline rhyolites with SiO 2 contents in the range 72-78 wt% (recalculated on a volatile-free basis), and are broadly similar to glassy rocks of the CVZ. Their major oxide, trace element, and REE compositions are indistinguishable from glasses of TVZ rhyolites. The trace element and REE compositional variability in the Late Miocene tephra beds, which were erupted over an estimated duration of c. 0.5-2.4 m.y. is no greater than that of large silicic eruptives of the last 350 ka, and is suggestive of a long-lived source and/or similar magmatic processes. However, the individual tephra beds are products of discrete homogeneous magma batches. New fission track ages of the Miocene tephra beds suggest the main period of volcaniclastic deposition occurred in the interval c. 9-7 Ma. This corresponds well with the initiation of rhyolitic volcanism in the CVZ at c. 10 Ma, and a major period of caldera formation that took place to c. 7 Ma. The ages suggest a sediment accumulation rate of between 0.23 and 1.2 m/ka (av. 0.4 m/ka), and a frequency of eruption of

  7. Candidate constructional volcanic edifices on Mercury


    Wright, J.; Rothery, D. A.; Balme, M. R.; Conway, S. J.


    [Introduction] Studies using MESSENGER data suggest that Mercury’s crust is predominantly a product of effusive volcanism that occurred in the first billion years following the planet’s formation. Despite this planet-wide effusive volcanism, no constructional volcanic edifices, characterized by a topographic rise, have hitherto been robustly identified on Mercury, whereas constructional volcanoes are common on other planetary bodies in the solar system with volcanic histories. Here, we descri...

  8. A 3D model of crustal magnetization at the Pinacate Volcanic Field, NW Sonora, Mexico (United States)

    García-Abdeslem, Juan; Calmus, Thierry


    The Pinacate Volcanic Field (PVF) is located near the western border of the southern Basin and Range province, in the State of Sonora NW Mexico, and within the Gulf of California Extensional Province. This volcanic field contains the shield volcano Santa Clara, which mainly consists of basaltic to trachytic volcanic rocks, and reaches an altitude of 1200 m. The PVF disrupts a series of discontinuous ranges of low topographic relief aligned in a NW direction, which consist mainly of Proterozoic metamorphic rocks and Proterozoic through Paleogene granitoids. The PVF covers an area of approximately 60 by 55 km, and includes more than 400 well-preserved cinder cones and vents and eight maar craters. It was active from about 1.7 Ma until about 13 ka. We have used the ages and magnetic polarities of the volcanic rocks, along with mapped magnetic anomalies and their inverse modeling to determine that the Pinacate Volcanic Field was formed during two volcanic episodes. The oldest one built the Santa Clara shield volcano of basaltic and trachytic composition, and occurred during the geomagnetic Matuyama Chron of reverse polarity, which also includes the normal polarity Jaramillo and Olduvai Subchrons, thus imprinting both normal and reverse magnetization in the volcanic products. The younger Pinacate series of basaltic composition represents monogenetic volcanic activity that extends all around the PVF and occurred during the subsequent geomagnetic Brunhes Chron of normal polarity. Magnetic anomalies toward the north of the Santa Clara volcano are the most intense in the PVF, and their inverse modeling indicates the presence of a large subsurface body magnetized in the present direction of the geomagnetic field. This suggests that the magma chambers at depth cooled below the Curie temperature during the Brunhes Chron.

  9. Late Cretaceous (ca. 95 Ma) magnesian andesites in the Biluoco area, southern Qiangtang subterrane, central Tibet: Petrogenetic and tectonic implications (United States)

    He, Haiyang; Li, Yalin; Wang, Chengshan; Zhou, Aorigele; Qian, Xinyu; Zhang, Jiawei; Du, Lintao; Bi, Wenjun


    The tectonic evolutionary history of the Lhasa and Qiangtang collision zones remains hotly debated because of the lack of pivotal magmatic records in the southern Qiangtang subterrane, central Tibet. We present zircon U-Pb dating, whole-rock major and trace-element geochemical analyses, and Sr-Nd isotopic data for the newly discovered Biluoco volcanic rocks from the southern Qiangtang subterrane, central Tibet. Zircon U-Pb dating reveals that the Biluoco volcanic rocks were crystallized at ca. 95 Ma. The samples are characterized by low SiO2 (50.26-54.53 wt%), high Cr (109.7-125.92 ppm) and Ni (57.4-71.58 ppm), and a high Mg# value (39-56), which plot in the magnesian andesites field on the rock classification diagram. They display highly fractionated rare earth element patterns with light rare earth element enrichment ([La/Yb]N = 21.04-25.24), high Sr/Y (63.97-78.79) and no negative Eu anomalies (Eu/Eu* = 0.98-1.04). The Biluoco volcanic rocks are depleted in Nb, Ta and Ti and enriched in Ba, Th, U and Pb. Moreover, the eight samples of Biluoco volcanic rocks display constant (87Sr/86Sr)i ratios (0.70514-0.70527), a positive εNd(t) value (2.16-2.68) and younger Nd model ages (0.56-0.62 Ga). These geochemical signatures indicate that the Biluoco volcanic rocks were most likely derived from partial melting of the mantle wedge peridotite metasomatized by melts of subducted slab and sediment in the subducted slab, invoked by asthenospheric upwelling resulting from the slab break-off of the northward subduction of the Bangong-Nujiang oceanic lithosphere. Identification of ca. 95 Ma Biluoco magnesian andesites suggests they were a delayed response of slab break-off of the northward subduction of the Bangong-Nujiang oceanic lithosphere at ca. 100 Ma.

  10. Interaction between climate, volcanism, and isostatic rebound in Southeast Alaska during the last deglaciation (United States)

    Praetorius, Summer; Mix, Alan; Jensen, Britta; Froese, Duane; Milne, Glenn A.; Wolhowe, Matthew; Addison, Jason A.; Prahl, Fred


    Observations of enhanced volcanic frequency during the last deglaciation have led to the hypothesis that ice unloading in glaciated volcanic terrains can promote volcanism through decompression melting in the shallow mantle or a reduction in crustal magma storage time. However, a direct link between regional climate change, isostatic adjustment, and the initiation of volcanism remains to be demonstrated due to the difficulty of obtaining high-resolution well-dated records that capture short-term climate and volcanic variability traced to a particular source region. Here we present an exceptionally resolved record of 19 tephra layers paired with foraminiferal oxygen isotopes and alkenone paleotemperatures from marine sediment cores along the Southeast Alaska margin spanning the last deglacial transition. Major element compositions of the tephras indicate a predominant source from the nearby Mt. Edgecumbe Volcanic Field (MEVF). We constrain the timing of this regional eruptive sequence to 14.6–13.1 ka. The sudden increase in volcanic activity from the MEVF coincides with the onset of Bølling–Allerød interstadial warmth, the disappearance of ice-rafted detritus, and rapid vertical land motion associated with modeled regional isostatic rebound in response to glacier retreat. These data support the hypothesis that regional deglaciation can rapidly trigger volcanic activity. Rapid sea surface temperature fluctuations and an increase in local salinity (i.e., δ18Osw) variability are associated with the interval of intense volcanic activity, consistent with a two-way interaction between climate and volcanism in which rapid volcanic response to ice unloading may in turn enhance short-term melting of the glaciers, plausibly via albedo effects on glacier ablation zones.

  11. Disruptive event analysis: volcanism and igneous intrusion

    International Nuclear Information System (INIS)

    Crowe, B.M.


    Three basic topics are addressed for the disruptive event analysis: first, the range of disruptive consequences of a radioactive waste repository by volcanic activity; second, the possible reduction of the risk of disruption by volcanic activity through selective siting of a repository; and third, the quantification of the probability of repository disruption by volcanic activity

  12. U–Pb geochronology and geochemistry of late Palaeozoic volcanism in Sardinia (southern Variscides

    Directory of Open Access Journals (Sweden)

    L. Gaggero


    Full Text Available The latest Carboniferous to lower Permian volcanism of the southern Variscides in Sardinia developed in a regional continental transpressive and subsequent transtensile tectonic regime. Volcanism produced a wide range of intermediate–silicic magmas including medium- to high-K calc-alkaline andesites, dacites, and rhyolites. A thick late Palaeozoic succession is well exposed in the four most representative Sardinian continental basins (Nurra, Perdasdefogu, Escalaplano, and Seui–Seulo, and contains substantial stratigraphic, geochemical, and geochronological evidence of the area's complex geological evolution from the latest Carboniferous to the beginning of the Triassic. Based on major and trace element data and LA-ICP-MS U–Pb zircon dating, it is possible to reconstruct the timing of post-Variscan volcanism. This volcanism records active tectonism between the latest Carboniferous and Permian, and post-dates the unroofing and erosion of nappes in this segment of the southern Variscides. In particular, igneous zircon grains from calc-alkaline silicic volcanic rocks yielded ages between 299 ± 1 and 288 ± 3 Ma, thereby constraining the development of continental strike-slip faulting from south (Escalaplano Basin to north (Nurra Basin. Notably, andesites emplaced in medium-grade metamorphic basement (Mt. Cobingius, Ogliastra show a cluster of older ages at 332 ± 12 Ma. Despite the large uncertainty, this age constrains the onset of igneous activity in the mid-crust. These new radiometric ages constitute: (1 a consistent dataset for different volcanic events; (2 a precise chronostratigraphic constraint which fits well with the biostratigraphic data and (3 insights into the plate reorganization between Laurussia and Gondwana during the late Palaeozoic evolution of the Variscan chain.

  13. K-Ar ages for the Yahazudake volcanic rocks from southwest Kyushu, Japan; Kyushu nanseibu yahazudake kazanganrui no K-Ar nendai

    Energy Technology Data Exchange (ETDEWEB)

    Yokose, H.; Kikuchi, W. [Kumamoto Univ. (Japan)] Nagao, K. [Okayama Univ. (Japan)264000] Kodama, K. [Kochi Univ. (Japan)


    Many volcanic rocks, seemed to be erupted during the period from the Pliocene epoch to the Pleistocene epoch, are distributed abounding in Kyushu, Japan. In this study, K-Ar ages determination about the 4 samples which represents the Hisatsu volcanic rocks distributed around Yahazudake and rhyolite distributed in Gesujima placed in the southernmost extremity of Amakusa Shimojima, was conducted. And consideration of time/space distribution of the Hisatsu volcanic rocks upon collecting the data which were reported until now and the data obtained by the present K-Ar age determination, was done. In the result of the present measurement, the absolute age of the Hisatsu volcanic rocks distributed around Minamata-shi became clear. I was clarified that Yahazudake volcanic rocks consisted of andesite, which is comparatively lacking in potassium, were formed during about 100 thousand years from 1.98 to 2.08 Ma, and Ontake volcanic rocks which exists for the bottom erupted at about 2.15 Ma. And, the age value of 2.89 Ma was obtained from Ushibuka rhyolite distributed in Gesujima. 35 refs., 4 figs., 3 tabs.

  14. Improving global detection of volcanic eruptions using the Ozone Monitoring Instrument (OMI

    Directory of Open Access Journals (Sweden)

    V. J. B. Flower


    Full Text Available Volcanic eruptions pose an ever-present threat to human populations around the globe, but many active volcanoes remain poorly monitored. In regions where ground-based monitoring is present the effects of volcanic eruptions can be moderated through observational alerts to both local populations and service providers, such as air traffic control. However, in regions where volcano monitoring is limited satellite-based remote sensing provides a global data source that can be utilised to provide near-real-time identification of volcanic activity. This paper details a volcanic plume detection method capable of identifying smaller eruptions than is currently feasible, which could potentially be incorporated into automated volcanic alert systems. This method utilises daily, global observations of sulfur dioxide (SO2 by the Ozone Monitoring Instrument (OMI on NASA's Aura satellite. Following identification and classification of known volcanic eruptions in 2005–2009, the OMI SO2 data, analysed using a logistic regression analysis, permitted the correct classification of volcanic events with an overall accuracy of over 80 %. Accurate volcanic plume identification was possible when lower-tropospheric SO2 loading exceeded ∼ 400 t. The accuracy and minimal user input requirements of the developed procedure provide a basis for incorporation into automated SO2 alert systems.

  15. A Volcanic Hydrogen Habitable Zone

    International Nuclear Information System (INIS)

    Ramirez, Ramses M.; Kaltenegger, Lisa


    The classical habitable zone (HZ) is the circular region around a star in which liquid water could exist on the surface of a rocky planet. The outer edge of the traditional N_2–CO_2–H_2O HZ extends out to nearly ∼1.7 au in our solar system, beyond which condensation and scattering by CO_2 outstrips its greenhouse capacity. Here, we show that volcanic outgassing of atmospheric H_2 can extend the outer edge of the HZ to ∼2.4 au in our solar system. This wider volcanic-hydrogen HZ (N_2–CO_2–H_2O–H_2) can be sustained as long as volcanic H_2 output offsets its escape from the top of the atmosphere. We use a single-column radiative-convective climate model to compute the HZ limits of this volcanic hydrogen HZ for hydrogen concentrations between 1% and 50%, assuming diffusion-limited atmospheric escape. At a hydrogen concentration of 50%, the effective stellar flux required to support the outer edge decreases by ∼35%–60% for M–A stars. The corresponding orbital distances increase by ∼30%–60%. The inner edge of this HZ only moves out ∼0.1%–4% relative to the classical HZ because H_2 warming is reduced in dense H_2O atmospheres. The atmospheric scale heights of such volcanic H_2 atmospheres near the outer edge of the HZ also increase, facilitating remote detection of atmospheric signatures.

  16. A Volcanic Hydrogen Habitable Zone

    Energy Technology Data Exchange (ETDEWEB)

    Ramirez, Ramses M.; Kaltenegger, Lisa, E-mail: [Carl Sagan Institute, Cornell University, Ithaca, NY (United States)


    The classical habitable zone (HZ) is the circular region around a star in which liquid water could exist on the surface of a rocky planet. The outer edge of the traditional N{sub 2}–CO{sub 2}–H{sub 2}O HZ extends out to nearly ∼1.7 au in our solar system, beyond which condensation and scattering by CO{sub 2} outstrips its greenhouse capacity. Here, we show that volcanic outgassing of atmospheric H{sub 2} can extend the outer edge of the HZ to ∼2.4 au in our solar system. This wider volcanic-hydrogen HZ (N{sub 2}–CO{sub 2}–H{sub 2}O–H{sub 2}) can be sustained as long as volcanic H{sub 2} output offsets its escape from the top of the atmosphere. We use a single-column radiative-convective climate model to compute the HZ limits of this volcanic hydrogen HZ for hydrogen concentrations between 1% and 50%, assuming diffusion-limited atmospheric escape. At a hydrogen concentration of 50%, the effective stellar flux required to support the outer edge decreases by ∼35%–60% for M–A stars. The corresponding orbital distances increase by ∼30%–60%. The inner edge of this HZ only moves out ∼0.1%–4% relative to the classical HZ because H{sub 2} warming is reduced in dense H{sub 2}O atmospheres. The atmospheric scale heights of such volcanic H{sub 2} atmospheres near the outer edge of the HZ also increase, facilitating remote detection of atmospheric signatures.

  17. 50-Ma Initiation of Hawaiian-Emperor Bend Records Major Change in Pacific Plate Motion (United States)

    Sharp, Warren D.; Clague, David A.


    The Hawaiian-Emperor bend has played a prominent yet controversial role in deciphering past Pacific plate motions and the tempo of plate motion change. New ages for volcanoes of the central and southern Emperor chain define large changes in volcanic migration rate with little associated change in the chain's trend, which suggests that the bend did not form by slowing of the Hawaiian hot spot. Initiation of the bend near Kimmei seamount about 50 million years ago (MA) was coincident with realignment of Pacific spreading centers and early magmatism in western Pacific arcs, consistent with formation of the bend by changed Pacific plate motion.

  18. Magmatism and Eurekan deformation in the High Arctic Large Igneous Province: 40Ar–39Ar age of Kap Washington Group volcanics, North Greenland

    DEFF Research Database (Denmark)

    Tegner, Christian; Storey, Michael; Holm, Paul Martin


    The High Arctic Large Igneous Province is unusual on two counts: first, magmatism was prolonged and has been suggested to include an initial tholeiitic phase (130–80 Ma) and a second alkaline phase (85–60 Ma); second, it was subsequently deformed during the Eurekan Orogeny. New 40Ar–39Ar dating...... of alkaline volcanics from Kap Kane, part of the Kap Washington Group volcanics at the northern tip of Greenland, provides an emplacement age of 71.2±0.5 Ma obtained from amphibole in lapilli tuffs, and a thermal resetting age of 49–47 Ma obtained in feldspar and whole-rocks from trachyte flows. Patch...... in the Labrador Sea and the Baffin Bay, and to eastwards displacement of Greenland relative to North America. The alkaline suite, therefore, may be unrelated to the main tholeiitic phase of the High Arctic Large Igneous Province. The subsequent initiation of continental rifting and ensuing seafloor spreading...

  19. MaGnET: Malaria Genome Exploration Tool. (United States)

    Sharman, Joanna L; Gerloff, Dietlind L


    The Malaria Genome Exploration Tool (MaGnET) is a software tool enabling intuitive 'exploration-style' visualization of functional genomics data relating to the malaria parasite, Plasmodium falciparum. MaGnET provides innovative integrated graphic displays for different datasets, including genomic location of genes, mRNA expression data, protein-protein interactions and more. Any selection of genes to explore made by the user is easily carried over between the different viewers for different datasets, and can be changed interactively at any point (without returning to a search). Free online use (Java Web Start) or download (Java application archive and MySQL database; requires local MySQL installation) at or Supplementary data are available at Bioinformatics online.

  20. Eruptive and environmental processes recorded by diatoms in volcanically-dispersed lake sediments from the Taupo Volcanic Zone, New Zealand (United States)

    Harper, Margaret A.; Pledger, Shirley A.; Smith, Euan G. C.; Van Eaton, Alexa; Wilson, Colin J. N.


    Late Pleistocene diatomaceous sediment was widely dispersed along with volcanic ash (tephra) across and beyond New Zealand by the 25.4 ka Oruanui supereruption from Taupo volcano. We present a detailed analysis of the diatom populations in the Oruanui tephra and the newly discovered floras in two other eruptions from the same volcano: the 28.6 ka Okaia and 1.8 ka Taupo eruptions. For comparison, the diatoms were also examined in Late Pleistocene and Holocene lake sediments from the Taupo Volcanic Zone (TVZ). Our study demonstrates how these microfossils provide insights into the lake history of the TVZ since the Last Glacial Maximum. Morphometric analysis of Aulacoseira valve dimensions provides a useful quantitative tool to distinguish environmental and eruptive processes within and between individual tephras. The Oruanui and Okaia diatom species and valve dimensions are highly consistent with a shared volcanic source, paleolake and eruption style (involving large-scale magma-water interaction). They are distinct from lacustrine sediments sourced elsewhere in the TVZ. Correspondence analysis shows that small, intact samples of erupted lake sediment (i.e., lithic clasts in ignimbrite) contain heterogeneous diatom populations, reflecting local variability in species composition of the paleolake and its shallowly-buried sediments. Our analysis also shows a dramatic post-Oruanui supereruption decline in Cyclostephanos novaezelandiae, which likely reflects a combination of (1) reorganisation of the watershed in the aftermath of the eruption, and (2) overall climate warming following the Last Glacial Maximum. This decline is reflected in substantially lower proportions of C. novaezelandiae in the 1.8 ka Taupo eruption deposits, and even fewer in post-1.8 ka sediments from modern (Holocene) Lake Taupo. Our analysis highlights how the excellent preservation of siliceous microfossils in volcanic tephra may fingerprint the volcanic source region and retain a valuable record

  1. Enhancing MA transmutation by irradiation of (MA, Zr)Hx in FBR blanket region - 5383

    International Nuclear Information System (INIS)

    Konashi, K.; Ikeda, K.; Itoh, K.; Hirai, M.; Koyama, T.; Kurosaki, K.


    Minor actinide (MA) hydride is proposed as transmutation target in sodium-cooled mixed oxide fuelled fast reactor. Preliminarily calculations have been done to check the transmutation efficiency of MA hydride targets. Three different types of MA target, MA-Zr alloy, (MA, Zr)O 2 and (MA, Zr)H x , have been compared on MA transmutation rate. The targets are assumed to be loaded around an active core in a 280 MWe sodium-cooled reactor; 54 MA target assemblies are respectively arranged in a row in the radial blanket zone. They are supposed to be irradiated for one year and then be cooled for 60 days. The transmuted mass has been evaluated by three-dimensional diffusion calculation to be 25, 15, 61 kg/EFPY for the alloy, the oxide and the hydride respectively, where production of MA in the active core is taken into account. The transmutation mass by (MA, Zr)H x is much larger than those by the other types of targets, while the core characteristics remain sound by locating MA targets outside of the active core. On top of that, two kinds of (MA, Zr)O 2 targets which are combined with ZrH x (x=1.7) pins have been calculated. Major Research/Development items are selected to establish the MA hydride transmutation method by reviewing technologies applicable to the transmutation system. The practical use of the MA hydride transmutation method is not far ahead technically, since this method can be developed by the extension of existing technologies. (authors)

  2. Paleoproterozoic andesitic volcanism in the southern Amazonian craton (northern Brazil); lithofacies analysis and geodynamic setting (United States)

    Roverato, Matteo; Juliani, Caetano; Capra, Lucia; Dias Fernandes, Carlos Marcelo


    Precambrian volcanism played an important role in geological evolution and formation of new crust. Most of the literature on Precambrian volcanic rocks describes settings belonging to subaqueous volcanic systems. This is likely because subaerial volcanic rocks in Proterozoic and Archean volcano-sedimentary succession are poorly preserved due to erosive/weathering processes. The late Paleoproterozoic Sobreiro Formation (SF) here described, seems to be one of the rare exceptions to the rule and deserves particular attention. SF represents the subaerial expression of an andesitic magmatism that, linked with the upper felsic Santa Rosa F., composes the Uatumã Group. Uatumã Group is an extensive magmatic event located in the Xingú region, southwestern of Pará state, Amazonian Craton (northern Brazil). The Sobreiro volcanism is thought to be related to an ocean-continent convergent margin. It is characterized by ~1880 Ma well-preserved calc-alkaline basaltic/andesitic to andesitic lava flows, pyroclastic rocks and associated reworked successions. The superb preservation of its rock-textures allowed us to describe in detail a large variety of volcaniclastic deposits. We divided them into primary and secondary, depending if they result from a direct volcanic activity (pyroclastic) or reworked processes. Our study reinforces the importance of ancient volcanic arcs and rocks contribution to the terrestrial volcaniclastic sedimentation and evolution of plate tectonics. The volcanic activity that produced pyroclastic rocks influenced the amount of detritus shed into sedimentary basins and played a major role in the control of sedimentary dispersal patterns. This study aims to provide, for the first time, an analysis of the physical volcanic processes for the subaerial SF, based in field observation, lithofacies analysis, thin section petrography and less geochemical data. The modern volcanological approach here used can serve as a model about the evolution of Precambrian

  3. The Western Arabian intracontinental volcanic fields as a potential UNESCO World Heritage site (United States)

    Németh, Károly; Moufti, Mohammed R.


    UNESCO promotes conservation of the geological and geomoprhological heritage through promotion of protection of these sites and development of educational programs under the umbrella of geoparks among the most globally significant ones labelled as UNESCO Global Geoparks. UNESCO also maintains a call to list those natural sites that provide universal outstanding values to demonstrate geological features or their relevance to our understanding the evolution of Earth. Volcanoes currently got a surge in nomination to be UNESCO World Heritage sites. Volcanic fields in the contrary fell in a grey area of nominations as they represents the most common manifestation of volcanism on Earth hence they are difficult to view as having outstanding universal values. A nearly 2500-km long 300-km wide region of dispersed volcanoes located in the Western Arabian Penninsula mostly in the Kingdom of Saudi Arabia form a near-continuous location that carries universal outstanding value as one of the most representative manifestation of dispersed intracontinental volcanism on Earth to be nominated as an UNESCO World Heritage site. The volcanic fields formed in the last 20 Ma along the Red Sea as group of simple basaltic to more mature and long-lived basalt to trachyte-to-rhyolite volcanic fields each carries high geoheritage values. While these volcanic fields are dominated by scoria and spatter cones and transitional lava fields, there are phreatomagmatic volcanoes among them such as maars and tuff rings. Phreatomagmatism is more evident in association with small volcanic edifices that were fed by primitive magmas, while phreatomagmatic influences during the course of a larger volume eruption are also known in association with the silicic eruptive centres in the harrats of Rahat, Kishb and Khaybar. Three of the volcanic fields are clearly bimodal and host small-volume relatively short-lived lava domes and associated block-and-ash fans providing a unique volcanic landscape commonly not

  4. Ma olin Saddami poeg / Latif Jahija

    Index Scriptorium Estoniae

    Jahija, Latif


    Järg Jan/21.,28. lk. 7,5. L. Jahija sensatsiooniline raamat "Ma olin Saddami poeg", milles ta pajatab kuidas ta a. 1987-1991 oli Iraagi presidendi vanema poja teisik. Lühikokkuvõte sellest jutustusest

  5. High-resolution 40Ar/39Ar geochronology of volcanic rocks from the Siebengebirge (Central Germany)—Implications for eruption timescales and petrogenetic evolution of intraplate volcanic fields (United States)

    Przybyla, Thomas; Pfänder, Jörg A.; Münker, Carsten; Kolb, Melanie; Becker, Maike; Hamacher, Uli


    A key parameter in understanding mantle dynamics beneath continents is the temporal evolution of intraplate volcanism in response to lithospheric thinning and asthenospheric uplift. To contribute to a better understanding of how intraplate volcanic fields evolve through time, we present a high precision 40Ar/39Ar age dataset for volcanic rocks from the Siebengebirge volcanic field (SVF) from central Germany, one of the best studied and compositionally most diverse intraplate volcanic fields of the Cenozoic Central European Volcanic Province (CEVP). Petrological and geochemical investigations suggest that the formation of the different rock types that occur in the SVF can be explained by a combination of assimilation and fractional crystallisation processes, starting from at least two different parental magmas with different levels of silica saturation (alkali basaltic and basanitic), and originating from different mantle sources. These evolved along two differentiation trends to latites and trachytes, and to tephrites and tephriphonolites, respectively. In contrast to their petrogenesis, the temporal evolution of the different SVF suites is poorly constrained. Previous K/Ar ages suggested a time of formation between about 28 and 19 Ma for the mafic rocks, and of about 27 to 24 Ma for the differentiated rocks. Our results confirm at high precision that the differentiated lithologies of both alkaline suites (40Ar/39Ar ages from 25.3 ± 0.2 Ma to 25.9 ± 0.3 Ma) erupted contemporaneously within a very short time period of 0.6 Ma, whereas the eruption of mafic rocks (basanites) lasted at least 8 Ma (40Ar/39Ar ages from 22.2 ± 0.2 Ma to 29.5 ± 0.3 Ma). This implies that felsic magmatism in the central SVF was likely a single event, possibly triggered by an intense phase of rifting, and that ongoing melting and eruption of mostly undifferentiated mafic lavas dominate the > 8 Ma long magmatic history of this region. Among the mafic lavas, most basanites and tephrites

  6. SHRIMP zircon U-Pb age and its significances of volcanic rocks from banshi basin in south jiangxi province

    International Nuclear Information System (INIS)

    Wang Baofeng; Wu Jianhua


    SHRIMP zircon U-Pb dating is applied to geochronological study for tuff of original Jilongzhang formation and rhyolite of original Banshi formation in Banshi basin, located in the Sannan (Longnan, Dingnan, Quannan) -Xunwu volcanic rocks belts in the south of Jiangxi. The result shows that zircon SHRIMP U-Pb age of the tuff is (142.5 ± 1.3) Ma and the age of the rhyolite is (131.4 ± 1.3) Ma. According to the latest international stratigraphic chart, the boundary between Jurassic and Cretaceous is (145.4 ± 4.0) Ma. So original Jilongzhang Formation and original Banshi Formation in Banshi basin were formed during early Early Cretaceous. The volcanic series in Banshi basin belongs to only one volcanic cycle. The features of the rock associations consistent with Wuyi group on the Xiajiang-Guangfeng volcanic rocks belts in the north of Jiangxi, so original Jilongzhang formation falls under E'huling formation and original Banshi formation falls under Shixi formation. (authors)

  7. FuSuMaTech workshop

    CERN Multimedia

    Olofsson, Simon


    The goal of the FuSuMaTecH IP workshop, organised at CERN Ideaquare 19-20 April, was to educate superconductivity and magnet experts about intellectual property. About 30 participants from multiple institutes and companies worked together in this two day interactive program which was facilitated by CERN Knowledge Transfer. Great progress was made in shaping the FuSuMaTech industrial demonstrator projects as well as the R&D&I subjects.

  8. [Ma2 antibody and multiple mononeuropathies]. (United States)

    Ayrignac, X; Castelnovo, G; Landrault, E; Fayolle, H; Pers, Y-M; Honnorat, J; Campello, C; Figarella-Branger, D; Labauge, P


    Anti-Ma2 antibodies belong to a family of onconeuronal antibodies that target proteins expressed in brain, testis and several tumors. Previously observed in patients presenting with limbic encephalitis, they seem to be associated with several other paraneoplastic syndromes. We report the case of a 73-year-old woman presenting sensory and motor neuropathy associated with non-small-cell lung cancer who had Ma2-antibodies.

  9. Seismic and volcanic risk in the Azores: reasons to stay in endangered places


    Arroz, Ana Margarida Moura; Palos, Ana Cristina Pires; Rego, Isabel Estrela


    SRA 2008 Annual Meeting "Risk Analysis: The Science and the Art", Boston, Massachusetts, Sunday, 7 December 2008 to Wednesday, 10 December 2008. Earthquakes and volcanic eruptions have been regular phenomena throughout the Azores' six centuries of history. In spite of the knowledge already gathered by local historians and Earth sciences researchers, there are no scientific data on the socio-cultural dimensions of volcanic and seismic risks. A study – TOPOI METUS. Social cosmographies of d...

  10. Spatio-volumetric hazard estimation in the Auckland volcanic field (United States)

    Bebbington, Mark S.


    The idea of a volcanic field `boundary' is prevalent in the literature, but ill-defined at best. We use the elliptically constrained vents in the Auckland Volcanic Field to examine how spatial intensity models can be tested to assess whether they are consistent with such features. A means of modifying the anisotropic Gaussian kernel density estimate to reflect the existence of a `hard' boundary is then suggested, and the result shown to reproduce the observed elliptical distribution. A new idea, that of a spatio-volumetric model, is introduced as being more relevant to hazard in a monogenetic volcanic field than the spatiotemporal hazard model due to the low temporal rates in volcanic fields. Significant dependencies between the locations and erupted volumes of the observed centres are deduced, and expressed in the form of a spatially-varying probability density. In the future, larger volumes are to be expected in the `gaps' between existing centres, with the location of the greatest forecast volume lying in the shipping channel between Rangitoto and Castor Bay. The results argue for tectonic control over location and magmatic control over erupted volume. The spatio-volumetric model is consistent with the hypothesis of a flat elliptical area in the mantle where tensional stresses, related to the local tectonics and geology, allow decompressional melting.

  11. Can rain cause volcanic eruptions? (United States)

    Mastin, Larry G.


    Volcanic eruptions are renowned for their violence and destructive power. This power comes ultimately from the heat and pressure of molten rock and its contained gases. Therefore we rarely consider the possibility that meteoric phenomena, like rainfall, could promote or inhibit their occurrence. Yet from time to time observers have suggested that weather may affect volcanic activity. In the late 1800's, for example, one of the first geologists to visit the island of Hawaii, J.D. Dana, speculated that rainfall influenced the occurrence of eruptions there. In the early 1900's, volcanologists suggested that some eruptions from Mount Lassen, Calif., were caused by the infiltration of snowmelt into the volcano's hot summit. Most such associations have not been provable because of lack of information; others have been dismissed after careful evaluation of the evidence.

  12. Source mechanisms of volcanic tsunamis. (United States)

    Paris, Raphaël


    Volcanic tsunamis are generated by a variety of mechanisms, including volcano-tectonic earthquakes, slope instabilities, pyroclastic flows, underwater explosions, shock waves and caldera collapse. In this review, we focus on the lessons that can be learnt from past events and address the influence of parameters such as volume flux of mass flows, explosion energy or duration of caldera collapse on tsunami generation. The diversity of waves in terms of amplitude, period, form, dispersion, etc. poses difficulties for integration and harmonization of sources to be used for numerical models and probabilistic tsunami hazard maps. In many cases, monitoring and warning of volcanic tsunamis remain challenging (further technical and scientific developments being necessary) and must be coupled with policies of population preparedness. © 2015 The Author(s).

  13. Quantitative physical models of volcanic phenomena for hazards assessment of critical infrastructures (United States)

    Costa, Antonio


    Volcanic hazards may have destructive effects on economy, transport, and natural environments at both local and regional scale. Hazardous phenomena include pyroclastic density currents, tephra fall, gas emissions, lava flows, debris flows and avalanches, and lahars. Volcanic hazards assessment is based on available information to characterize potential volcanic sources in the region of interest and to determine whether specific volcanic phenomena might reach a given site. Volcanic hazards assessment is focussed on estimating the distances that volcanic phenomena could travel from potential sources and their intensity at the considered site. Epistemic and aleatory uncertainties strongly affect the resulting hazards assessment. Within the context of critical infrastructures, volcanic eruptions are rare natural events that can create severe hazards. In addition to being rare events, evidence of many past volcanic eruptions is poorly preserved in the geologic record. The models used for describing the impact of volcanic phenomena generally represent a range of model complexities, from simplified physics based conceptual models to highly coupled thermo fluid dynamical approaches. Modelling approaches represent a hierarchy of complexity, which reflects increasing requirements for well characterized data in order to produce a broader range of output information. In selecting models for the hazard analysis related to a specific phenomenon, questions that need to be answered by the models must be carefully considered. Independently of the model, the final hazards assessment strongly depends on input derived from detailed volcanological investigations, such as mapping and stratigraphic correlations. For each phenomenon, an overview of currently available approaches for the evaluation of future hazards will be presented with the aim to provide a foundation for future work in developing an international consensus on volcanic hazards assessment methods.

  14. Volcanic hazards in Central America (United States)

    Rose, William I.; Bluth, Gregg J.S.; Carr, Michael J.; Ewert, John W.; Patino, Lina C.; Vallance, James W.


    This volume is a sampling of current scientific work about volcanoes in Central America with specific application to hazards. The papers reflect a variety of international and interdisciplinary collaborations and employ new methods. The book will be of interest to a broad cross section of scientists, especially volcanologists. The volume also will interest students who aspire to work in the field of volcano hazards mitigation or who may want to work in one of Earth’s most volcanically active areas.

  15. The East Australian, Tasmantid, and Lord Howe Volcanic Chains: Possible mechanisms behind a trio of hotspot trails (United States)

    Kalnins, L. M.; Cohen, B. E.; Fitton, J. G.; Mark, D. F.; Richards, F. D.; Barfod, D. N.


    The east Australian and Tasman Sea region is home to a unique example of intraplate volcanism: three long-lived, sub-parallel volcanic chains spaced only about 500 km apart. Here we present new 40Ar/39Ar results from the centre chain, the Tasmantid Seamounts, and show that the chain is strongly age-progressive, with an excellent correspondence to the age of the continental East Australian Volcanic Chain to the west and to the more limited ages available for the Lord Howe Seamount Chain to the east. Results from the Louisiade Plateau at the northern end of the Tasmantid chain suggest that it is composed of basalts of the correct age to be a large igneous province formed by the impact of the Tasmantid plume head reaching the lithosphere. This record of relative movement between the plate and the magma source over the last 55 Ma shows two clear deflections from the overall linear trend, one at 26--23 Ma, also observed in the continental chain and linked with the Ontong-Java Plateau jamming the South Melanesian subduction zone, and another at 50--43 Ma, beyond the end of the continental record and contemporaneous with the Hawaiian-Emperor bend. How does such a unique trio of volcanic chains form? The clear age progression, long lifespan, and tie to the Louisiade Plateau are classic indicators of deep-seated plumes, but it is difficult to explain how three separate plumes could remain stable for over 30 Ma when separated by little more than the radii of the plume conduits. Here we examine alternative possible explanations for this volcanic pattern, including small plumes rising from a single deep-seated plume pooling at the 660 km discontinuity, a single plume splitting around a subducting slab fragment, and small-scale convection triggered by topography on the lithosphere-asthenosphere boundary.

  16. Geological and 40Ar/39Ar age constraints on late-stage Deccan rhyolitic volcanism, inter-volcanic sedimentation, and the Panvel flexure from the Dongri area, Mumbai (United States)

    Sheth, Hetu C.; Pande, Kanchan


    Post-K-Pg Boundary Deccan magmatism is well known from the Mumbai area in the Panvel flexure zone. Represented by the Salsette Subgroup, it shows characters atypical of much of the Deccan Traps, including rhyolite lavas and tuffs, mafic tuffs and breccias, spilitic pillow basalts, and "intertrappean" sedimentary or volcanosedimentary deposits, with mafic intrusions as well as trachyte intrusions containing basaltic enclaves. The intertrappean deposits have been interpreted as formed in shallow marine or lagoonal environments in small fault-bounded basins due to syn-volcanic subsidence. We report a previously unknown sedimentary deposit underlying the Dongri rhyolite flow from the upper part of the Salsette Subgroup, with a westerly tectonic dip due to the Panvel flexure. We have obtained concordant 40Ar/39Ar ages of 62.6 ± 0.6 Ma (2σ) and 62.9 ± 0.2 Ma (2σ) for samples taken from two separate outcrops of this rhyolite. The results are significant in showing that (i) Danian inter-volcanic sedimentary deposits formed throughout Mumbai, (ii) the rock units are consistent with the stratigraphy postulated earlier for Mumbai, (iii) shale fragments known in some Dongri tuffs were likely derived from the sedimentary deposit under the Dongri rhyolite, (iv) the total duration of extrusive and intrusive Deccan magmatism was at least 8-9 million years, and (v) Panvel flexure formed, or continued to form, after 63 Ma, possibly even 62 Ma, and could not have formed by 65-64 Ma as concluded in a recent study.

  17. Volcanic deformation in the Andes (United States)

    Riddick, S.; Fournier, T.; Pritchard, M.


    We present the results from an InSAR survey of volcanic activity in South America. We use data from the Japanese Space Agency's ALOS L-band radar satellite from 2006-2009. The L-band instrument provides better coherence in densely vegetated regions, compared to the shorter wave length C-band data. The survey reveals volcano related deformation in regions, north, central and southern, of the Andes volcanic arc. Since observations are limited to the austral summer, comprehensive coverage of all volcanoes is not possible. Yet, our combined observations reveal volcanic/hydrothermal deformation at Lonquimay, Llaima, Laguna del Maule, and Chaitén volcanoes, extend deformation measurements at Copahue, and illustrate temporal complexity to the previously described deformation at Cerro Hudson and Cordón Caulle. No precursory deformation is apparent before the large Chaitén eruption (VEI_5) of 2 May 2008, (at least before 16 April) suggesting rapid magma movement from depth at this long dormant volcano. Subsidence at Ticsani Volcano occurred coincident with an earthquake swarm in the same region.

  18. Volcanic mercury in Pinus canariensis (United States)

    Rodríguez Martín, José Antonio; Nanos, Nikos; Miranda, José Carlos; Carbonell, Gregoria; Gil, Luis


    Mercury (Hg) is a toxic element that is emitted to the atmosphere by both human activities and natural processes. Volcanic emissions are considered a natural source of mercury in the environment. In some cases, tree ring records taken close to volcanoes and their relation to volcanic activity over time are contradictory. In 1949, the Hoyo Negro volcano (La Palma-Canary Islands) produced significant pyroclastic flows that damaged the nearby stand of Pinus canariensis. Recently, 60 years after the eruption, we assessed mercury concentrations in the stem of a pine which survived volcano formation, located at a distance of 50 m from the crater. We show that Hg content in a wound caused by pyroclastic impacts (22.3 μg kg-1) is an order of magnitude higher than the Hg concentrations measured in the xylem before and after the eruption (2.3 μg kg-1). Thus, mercury emissions originating from the eruption remained only as a mark—in pyroclastic wounds—and can be considered a sporadic and very high mercury input that did not affect the overall Hg input in the xylem. In addition, mercury contents recorded in the phloem (9.5 μg kg-1) and bark (6.0 μg kg-1) suggest that mercury shifts towards non-living tissues of the pine, an aspect that can be related to detoxification in volcanism-adapted species.

  19. Source mechanism of volcanic tremor

    Energy Technology Data Exchange (ETDEWEB)

    Ferrick, M.G.; Qamar, A.; St. Lawrence, W.F.


    Low-frequency (<10 Hz) volcanic earthquakes originate at a wide range of depths and occur before, during, and after magmatic eruptions. The characteristics of these earthquakes suggest that they are not typical tectonic events. Physically analogous processes occur in hydraulic fracturing of rock formations, low-frequency icequakes in temperate glaciers, and autoresonance in hydroelectric power stations. We propose that unsteady fluid flow in volcanic conduits is the common source mechanism of low-frequency volcanic earthquakes (tremor). The fluid dynamic source mechanism explains low-frequency earthquakes of arbitrary duration, magnitude, and depth of origin, as unsteady flow is independent of physical properties of the fluid and conduit. Fluid transients occur in both low-viscosity gases and high-viscosity liquids. A fluid transient analysis can be formulated as generally as is warranted by knowledge of the composition and physical properties of the fluid, material properties, geometry and roughness of the conduit, and boundary conditions. To demonstrate the analytical potential of the fluid dynamic theory, we consider a single-phase fluid, a melt of Mount Hood andesite at 1250/sup 0/C, in which significant pressure and velocity variations occur only in the longitudinal direction. Further simplification of the conservation of mass and momentum equations presents an eigenvalue problem that is solved to determine the natural frequencies and associated damping of flow and pressure oscillations.

  20. Volcanic mercury in Pinus canariensis. (United States)

    Rodríguez Martín, José Antonio; Nanos, Nikos; Miranda, José Carlos; Carbonell, Gregoria; Gil, Luis


    Mercury (Hg) is a toxic element that is emitted to the atmosphere by both human activities and natural processes. Volcanic emissions are considered a natural source of mercury in the environment. In some cases, tree ring records taken close to volcanoes and their relation to volcanic activity over time are contradictory. In 1949, the Hoyo Negro volcano (La Palma-Canary Islands) produced significant pyroclastic flows that damaged the nearby stand of Pinus canariensis. Recently, 60 years after the eruption, we assessed mercury concentrations in the stem of a pine which survived volcano formation, located at a distance of 50 m from the crater. We show that Hg content in a wound caused by pyroclastic impacts (22.3 μg kg(-1)) is an order of magnitude higher than the Hg concentrations measured in the xylem before and after the eruption (2.3 μg kg(-1)). Thus, mercury emissions originating from the eruption remained only as a mark-in pyroclastic wounds-and can be considered a sporadic and very high mercury input that did not affect the overall Hg input in the xylem. In addition, mercury contents recorded in the phloem (9.5 μg kg(-1)) and bark (6.0 μg kg(-1)) suggest that mercury shifts towards non-living tissues of the pine, an aspect that can be related to detoxification in volcanism-adapted species.

  1. Evolution of volcanically-induced palaeoenvironmental changes leading to the onset of OAE1a (early Aptian, Cretaceous) (United States)

    Keller, Christina E.; Hochuli, Peter A.; Giorgioni, Martino; Garcia, Therese I.; Bernasconi, Stefano M.; Weissert, Helmut


    During the Cretaceous, several major volcanic events occurred that initiated climate warming, altered marine circulation and increased marine productivity, which in turn often resulted in the widespread black shale deposits of the Oceanic Anoxic Events (OAE). In the sediments underlying the early Aptian OAE1a black shales, a prominent negative carbon isotope excursion is recorded. Its origin had long been controversial (e.g. Arthur, 2000; Jahren et al., 2001) before recent studies attributed it to the Ontong Java volcanism (Méhay et al., 2009; Tejada et al., 2009). Therefore the negative C-isotope excursion covers the interval between the time, when volcanic activity became important enough to be recorded in the C-isotope composition of the oceans to the onset of widespread anoxic conditions (OAE1a). We chose this interval at the locality of Pusiano (N-Italy) to study the effect of a volcanically-induced increase in pCO2 on the marine palaeoenvironment and to observe the evolving palaeoenvironmental conditions that finally led to OAE1a. The Pusiano section (Maiolica Formation) was deposited at the southern continental margin of the alpine Tethys Ocean and has been bio- and magnetostratigraphically dated by Channell et al. (1995). We selected 18 samples from 12 black shale horizons for palynofacies analyses. Palynofacies assemblages consist of several types of particulate organic matter, providing information on the origin of the organic matter (terrestrial/marine) and conditions during deposition (oxic/anoxic). We then linked the palynofacies results to high-resolution inorganic and organic C-isotope values and total organic carbon content measurements. The pelagic Pusiano section consists of repeated limestone-black shale couplets, which are interpreted to be the result of changes in oxygenation of bottom waters. Towards the end of the negative C-isotope excursion we observe enhanced preservation of the fragile amorphous organic matter resulting in increased

  2. Shock Deformation and Volcanism across the Cretaceous - Transition. (United States)

    Huffman, Alan Royce


    The cause of the Cretaceous-Tertiary (K/T) transition remains one of the most controversial scientific topics in the geosciences. Geological and geophysical evidence associated with the K/T boundary have been used to argue that the extinctions were caused by meteor impact or volcanism. The goal of this study was to assess the viability of a volcanic model for the K/T transition. Comparison of natural and experimentally-shocked quartz and feldspar using optical and transmission electron microscopy (TEM) revealed that the optical and statistical character of shock-induced microstructures in volcanic rocks are different from both classic impact microstructures, and from the Raton K/T samples. A series of 31 high-explosive (HE) shock-recovery experiments at pressures to 25 GPa and temperatures to 750^circC were completed on samples of granite and quartzite. TEM and optical microscopy reveal that pre-shock temperature and pulse duration have a first-order effect on the development of shock-induced microstructures in quartz and feldspar. Application of the experimental results to natural shock-induced microstructures indicates that the volcanic microstructures are probably produced at elevated temperatures and shock pressures that do not exceed 15 GPa. The results also suggest that the Raton K/T deposits were produced at pressures below about 25 GPa. Analysis of samples from the K/T transition at DSDP Site 527 and correlations between biostratigraphy, isotopes, and the data from this study suggest that the decline in marine productivity over an extended period of time may be due to climate changes induced by basaltic volcanism. The eruption of the Deccan Traps is a viable mechanism for the K/T extinctions, and the correlation of flood basalts with every major biotic crisis in the last 250 Ma supports the link between these two phenomena. Eruption of flood basalts enriched in F, Cl, CO_2 , and SO_2, could disrupt the terrestrial ecosystem, and could produce effects

  3. Disruptive event analysis: volcanism and igneous intrusion

    International Nuclear Information System (INIS)

    Crowe, B.M.


    An evaluation is made of the disruptive effects of volcanic activity with respect to long term isolation of radioactive waste through deep geologic storage. Three major questions are considered. First, what is the range of disruption effects of a radioactive waste repository by volcanic activity. Second, is it possible, by selective siting of a repository, to reduce the risk of disruption by future volcanic activity. And third, can the probability of repository disruption by volcanic activity be quantified. The main variables involved in the evaluation of the consequences of repository disruption by volcanic activity are the geometry of the magma-repository intersection (partly controlled by depth of burial) and the nature of volcanism. Potential radionuclide dispersal by volcanic transport within the biosphere ranges in distance from several kilometers to global. Risk from the most catastrophic types of eruptions can be reduced by careful site selection to maximize lag time prior to the onset of activity. Certain areas or volcanic provinces within the western United States have been sites of significant volcanism and should be avoided as potential sites for a radioactive waste repository. Examples of projection of future sites of active volcanism are discussed for three areas of the western United States. Probability calculations require two types of data: a numerical rate or frequency of volcanic activity and a numerical evaluation of the areal extent of volcanic disruption for a designated region. The former is clearly beyond the current state of art in volcanology. The latter can be approximated with a reasonable degree of satisfaction. In this report, simplified probability calculations are attempted for areas of past volcanic activity

  4. Anti Ma2-associated myeloradiculopathy: expanding the phenotype of anti-Ma2 associated paraneoplastic syndromes


    Murphy, Sinead M; Khan, Usman; Alifrangis, Constantine; Hazell, Steven; Hrouda, David; Blake, Julian; Ball, Joanna; Gabriel, Carolyn; Markarian, Pierre; Rees, Jeremy; Karim, Abid; Seckl, Michael J; Lunn, Michael P; Reilly, Mary M


    Anti-Ma2 associated paraneoplastic syndrome usually presents as limbic encephalitis in association with testicular tumours.1, 2 Only four patients have been reported with involvement outside the CNS, two of whom also had limbic or brainstem encephalitis.2, 3 We report a man with anti- Ma2 associated myeloradiculopathy and previous testicular cancer whose neurological syndrome stabilised and anti-Ma2 titres fell following orchidectomy of a microscopically normal testis.

  5. Origin of metaluminous and alkaline volcanic rocks of the Latir volcanic field, northern Rio Grande rift, New Mexico (United States)

    Johnson, C.M.; Lipman, P.W.


    Volcanic rocks of the Latir volcanic field evolved in an open system by crystal fractionation, magma mixing, and crustal assimilation. Early high-SiO2 rhyolites (28.5 Ma) fractionated from intermediate compositionmagmas that did not reach the surface. Most precaldera lavas have intermediate-compositions, from olivine basaltic-andesite (53% SiO2) to quartz latite (67% SiO2). The precaldera intermediate-composition lavas have anomalously high Ni and MgO contents and reversely zoned hornblende and augite phenocrysts, indicating mixing between primitive basalts and fractionated magmas. Isotopic data indicate that all of the intermediate-composition rocks studied contain large crustal components, although xenocrysts are found only in one unit. Inception of alkaline magmatism (alkalic dacite to high-SiO2 peralkaline rhyolite) correlates with, initiation of regional extension approximately 26 Ma ago. The Questa caldera formed 26.5 Ma ago upon eruption of the >500 km3 high-SiO2 peralkaline Amalia Tuff. Phenocryst compositions preserved in the cogenetic peralkaline granite suggest that the Amalia Tuff magma initially formed from a trace element-enriched, high-alkali metaluminous magma; isotopic data suggest that the parental magmas contain a large crustal component. Degassing of water- and halogen-rich alkali basalts may have provided sufficient volatile transport of alkalis and other elements into the overlying silicic magma chamber to drive the Amalia Tuff magma to peralkaline compositions. Trace element variations within the Amalia Tuff itself may be explained solely by 75% crystal fractionation of the observed phenocrysts. Crystal settling, however, is inconsistent with mineralogical variations in the tuff, and crystallization is thought to have occurred at a level below that tapped by the eruption. Spatially associated Miocene (15-11 Ma) lavas did not assimilate large amounts of crust or mix with primitive basaltic magmas. Both mixing and crustal assimilation processes

  6. The Volcanic Myths of the Red Sea - Temporal Relationship Between Magmatism and Rifting (United States)

    Stockli, D. F.; Bosworth, W.


    The Cenozoic Red Sea is one of the premier examples of continental rifting and active break-up. It has been cited as an example for both prototypical volcanic, pure shear rift systems with limited crustal stretching as well as magma-poor simple-shear rifting and highly asymmetric rift margins characterized by low-angle normal faults. In light of voluminous Oligocene continental flood basalts in the Afar/Ethiopian region, the Red Sea has often been viewed as a typical volcanic rift, despite evidence for asymmetric extension and hyperextended crust (Zabargad Island). An in-depth analysis of the timing, spatial distribution, and nature of Red Sea volcanism and its relationship to late Cenozoic extensional faulting should shed light on some of the misconceptions. The Eocene appearance of the East African super-plume was not accompanied by any recognized significant extensional faulting or rift-basin formation. The first phase of volcanism more closely associated with the Red Sea occurred in northern Ethiopia and western Yemen at 31-30 Ma and was synchronous with the onset of continental extension in the Gulf of Aden. Early Oligocene volcanism has also been documented in southern and central Saudi Arabia and southern Sudan. However, this voluminous Oligocene volcanism entirely predates Red Sea extensional faulting and rift formation. Marking the onset of Red Sea rifting, widespread, spatially synchronous intrusion of basaltic dikes occurred at 24-21 Ma along the entire Red Sea-Gulf of Suez rift and continuing into northern Egypt. While the initiation of lithospheric extension in the central and northern and central Red Sea and Gulf of Suez was accompanied by only sparse basaltic volcanism and possible underplating, the main phase of rifting in the Miocene Red Sea/Gulf of Suez completely lacks any significant rift-related volcanism, suggesting plate-boundary forces probably drove overall separation of Arabia from Africa. During progressive rifting, there is also no

  7. Miocene magmatism in the Bodie Hills volcanic field, California and Nevada: A long-lived eruptive center in the southern segment of the ancestral Cascades arc (United States)

    John, David A.; du Bray, Edward A.; Blakely, Richard J.; Fleck, Robert J.; Vikre, Peter; Box, Stephen E.; Moring, Barry C.


    The Middle to Late Miocene Bodie Hills volcanic field is a >700 km2, long-lived (∼9 Ma) but episodic eruptive center in the southern segment of the ancestral Cascades arc north of Mono Lake (California, U.S.). It consists of ∼20 major eruptive units, including 4 trachyandesite stratovolcanoes emplaced along the margins of the field, and numerous, more centrally located silicic trachyandesite to rhyolite flow dome complexes. Bodie Hills volcanism was episodic with two peak periods of eruptive activity: an early period ca. 14.7–12.9 Ma that mostly formed trachyandesite stratovolcanoes and a later period between ca. 9.2 and 8.0 Ma dominated by large trachyandesite-dacite dome fields. A final period of small silicic dome emplacement occurred ca. 6 Ma. Aeromagnetic and gravity data suggest that many of the Miocene volcanoes have shallow plutonic roots that extend to depths ≥1–2 km below the surface, and much of the Bodie Hills may be underlain by low-density plutons presumably related to Miocene volcanism.Compositions of Bodie Hills volcanic rocks vary from ∼50 to 78 wt% SiO2, although rocks with Bodie Hills rocks are porphyritic, commonly containing 15–35 vol% phenocrysts of plagioclase, pyroxene, and hornblende ± biotite. The oldest eruptive units have the most mafic compositions, but volcanic rocks oscillated between mafic and intermediate to felsic compositions through time. Following a 2 Ma hiatus in volcanism, postsubduction rocks of the ca. 3.6–0.1 Ma, bimodal, high-K Aurora volcanic field erupted unconformably onto rocks of the Miocene Bodie Hills volcanic field.At the latitude of the Bodie Hills, subduction of the Farallon plate is inferred to have ended ca. 10 Ma, evolving to a transform plate margin. However, volcanism in the region continued until 8 Ma without an apparent change in rock composition or style of eruption. Equidimensional, polygenetic volcanoes and the absence of dike swarms suggest a low differential horizontal stress regime

  8. Detecting Volcanic Ash Plumes with GNSS Signals (United States)

    Rainville, N.; Larson, K. M.; Palo, S. E.; Mattia, M.; Rossi, M.; Coltelli, M.; Roesler, C.; Fee, D.


    Global Navigation Satellite Systems (GNSS) receivers are commonly placed near volcanic sites to measure ground deformation. In addition to the carrier phase data used to measure ground position, these receivers also record Signal to Noise ratio (SNR) data. Larson (2013) showed that attenuations in SNR data strongly correlate with ash emissions at a series of eruptions of Redoubt Volcano. This finding has been confirmed at eruptions for Tongariro, Mt Etna, Mt Shindake, and Sakurajima. In each of these detections, very expensive geodetic quality GNSS receivers were used. If low-cost GNSS instruments could be used instead, a networked array could be deployed and optimized for plume detection and tomography. The outputs of this sensor array could then be used by both local volcanic observatories and Volcano Ash Advisory Centers. Here we will describe progress in developing such an array. The sensors we are working with are intended for navigation use, and thus lack the supporting power and communications equipment necessary for a networked system. Reliably providing those features is major challenge for the overall sensor design. We have built prototypes of our Volcano Ash Plume Receiver (VAPR), with solar panels, lithium-ion batteries and onboard data storage for preliminary testing. We will present results of our field tests of both receivers and antennas. A second critical need for our array is a reliable detection algorithm. We have tested our algorithm on data from recent eruptions and have incorporated the noise characteristics of the low-cost GNSS receiver. We have also developed a simulation capability so that the receivers can be deployed to optimize vent crossing GNSS signals.

  9. Widespread Neogene and Quaternary Volcanism on Central Kerguelen Plateau, Southern Indian Ocean (United States)

    Duncan, R. A.; Falloon, T.; Quilty, P. G.; Coffin, M. F.


    We report new age determinations and compositions for rocks from 18 dredge hauls collected from eight submarine areas across Central Kerguelen Plateau (CKP). Sea knolls and volcanic fields with multiple small cones were targeted over a 125,000 km2 region that includes Heard and McDonald islands. Large early Miocene (16-22 Ma) sea knolls rise from the western margin of the CKP and are part of a NNW-SSE line of volcanic centers that lie between Îles Kerguelen and Heard and McDonald islands. A second group of large sea knolls is aligned E-W across the center of this region. We see evidence of much younger activity (5 Ma to present) in volcanic fields to the north of, and up to 300 km NE of Heard Island. Compositions include basanite, basalt, and trachybasalt, that are broadly similar to plateau lava flows from nearby Ocean Drilling Program (ODP) Site 1138, lower Miocene lavas at Îles Kerguelen, dredged rocks from the early Miocene sea knolls, and Big Ben lavas from Heard Island. Geochemical data indicate decreasing fractions of mantle source melting with time. The western line of sea knolls has been related to hotspot activity now underlying the Heard Island area. In view of the now recognized much larger area of young volcanic activity, we propose that a broad region of CKP became volcanically active in Neogene time due to incubation of plume material at the base of the relatively stationary overlying plateau. The presence of pre-existing crustal faults promotes access for melts from the Heard mantle plume to rise to the surface.

  10. Volcanism in slab tear faults is larger than in island-arcs and back-arcs. (United States)

    Cocchi, Luca; Passaro, Salvatore; Tontini, Fabio Caratori; Ventura, Guido


    Subduction-transform edge propagators are lithospheric tears bounding slabs and back-arc basins. The volcanism at these edges is enigmatic because it is lacking comprehensive geological and geophysical data. Here we present bathymetric, potential-field data, and direct observations of the seafloor on the 90 km long Palinuro volcanic chain overlapping the E-W striking tear of the roll-backing Ionian slab in Southern Tyrrhenian Sea. The volcanic chain includes arc-type central volcanoes and fissural, spreading-type centers emplaced along second-order shears. The volume of the volcanic chain is larger than that of the neighbor island-arc edifices and back-arc spreading center. Such large volume of magma is associated to an upwelling of the isotherms due to mantle melts upraising from the rear of the slab along the tear fault. The subduction-transform edge volcanism focuses localized spreading processes and its magnitude is underestimated. This volcanism characterizes the subduction settings associated to volcanic arcs and back-arc spreading centers.

  11. A heat pipe mechanism for volcanism and tectonics on Venus

    International Nuclear Information System (INIS)

    Turcotte, D.L.


    A heat pipe mechanism is proposed for the transport of heat through the lithosphere on Venus. This mechanism allows the crust and lithosphere on Venus to be greater than 150 km thick. A thick crust and thick lithosphere can explain the high observed topography and large associated gravity anomalies. For a 150-km-thick lithosphere the required volcanic flux on Venus is 200 km 3 /yr; this is compared with a flux of 17 km 3 /yr associated with the formation of the oceanic crust on Earth. A thick basaltic crust on Venus is expected to transform to eclogite at a depth of 60 to 80 km; the dense eclogite would contribute the lithospheric delamination that returns the crust to the interior of the planet completing the heat pipe cycle. Topography and the associated gravity anomalies can be explained by Airy compensation of the thick crust. The principal observation that is contrary to this hypothesis is the mean age of the surface that is inferred from crater statistics; the minimum mean age is about 130 Ma, and this implies an upper limit of 2 km 3 /yr for the surface volcanic flux. If the heat pipe mechanism was applicable on Earth in the Archean, it would provide the thick lithosphere implied by isotopic data from diamonds

  12. Volcanic unrest and hazard communication in Long Valley Volcanic Region, California (United States)

    Hill, David P.; Mangan, Margaret T.; McNutt, Stephen R.


    The onset of volcanic unrest in Long Valley Caldera, California, in 1980 and the subsequent fluctuations in unrest levels through May 2016 illustrate: (1) the evolving relations between scientists monitoring the unrest and studying the underlying tectonic/magmatic processes and their implications for geologic hazards, and (2) the challenges in communicating the significance of the hazards to the public and civil authorities in a mountain resort setting. Circumstances special to this case include (1) the sensitivity of an isolated resort area to media hype of potential high-impact volcanic and earthquake hazards and its impact on potential recreational visitors and the local economy, (2) a small permanent population (~8000), which facilitates face-to-face communication between scientists monitoring the hazard, civil authorities, and the public, and (3) the relatively frequent turnover of people in positions of civil authority, which requires a continuing education effort on the nature of caldera unrest and related hazards. Because of delays associated with communication protocols between the State and Federal governments during the onset of unrest, local civil authorities and the public first learned that the U.S. Geological Survey was about to release a notice of potential volcanic hazards associated with earthquake activity and 25-cm uplift of the resurgent dome in the center of the caldera through an article in the Los Angeles Times published in May 1982. The immediate reaction was outrage and denial. Gradual acceptance that the hazard was real required over a decade of frequent meetings between scientists and civil authorities together with public presentations underscored by frequently felt earthquakes and the onset of magmatic CO2 emissions in 1990 following a 11-month long earthquake swarm beneath Mammoth Mountain on the southwest rim of the caldera. Four fatalities, one on 24 May 1998 and three on 6 April 2006, underscored the hazard posed by the CO2

  13. Volcanic hazards and public response (United States)

    Peterson, Donald W.


    Although scientific understanding of volcanoes is advancing, eruptions continue to take a substantial toll of life and property. Some of these losses could be reduced by better advance preparation, more effective flow of information between scientists and public officials, and better understanding of volcanic behavior by all segments of the public. The greatest losses generally occur at volcanoes that erupt infrequently where people are not accustomed to dealing with them. Scientists sometimes tend to feel that the blame for poor decisions in emergency management lies chiefly with officials or journalists because of their failure to understand the threat. However, the underlying problem embraces a set of more complex issues comprising three pervasive factors. The first factor is the volcano: signals given by restless volcanoes are often ambiguous and difficult to interpret, especially at long-quiescent volcanoes. The second factor is people: people confront hazardous volcanoes in widely divergent ways, and many have difficulty in dealing with the uncertainties inherent in volcanic unrest. The third factor is the scientists: volcanologists correctly place their highest priority on monitoring and hazard assessment, but they sometimes fail to explain clearly their conclusions to responsible officials and the public, which may lead to inadequate public response. Of all groups in society, volcanologists have the clearest understanding of the hazards and vagaries of volcanic activity; they thereby assume an ethical obligation to convey effectively their knowledge to benefit all of society. If society resists, their obligation nevertheless remains. They must use the same ingenuity and creativity in dealing with information for the public that they use in solving scientific problems. When this falls short, even excellent scientific results may be nullified.

  14. M&A information technology best practices

    CERN Document Server

    Roehl-Anderson, Janice M


    Add value to your organization via the mergers & acquisitions IT function  As part of Deloitte Consulting, one of the largest mergers and acquisitions (M&A) consulting practice in the world, author Janice Roehl-Anderson reveals in M&A Information Technology Best Practices how companies can effectively and efficiently address the IT aspects of mergers, acquisitions, and divestitures. Filled with best practices for implementing and maintaining systems, this book helps financial and technology executives in every field to add value to their mergers, acquisitions, and/or divestitures via the IT

  15. MaRIE Undulator & XFEL Systems

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, Dinh Cong [Los Alamos National Laboratory; Marksteiner, Quinn R. [Los Alamos National Laboratory; Anisimov, Petr Mikhaylovich [Los Alamos National Laboratory; Buechler, Cynthia Eileen [Los Alamos National Laboratory


    The 22 slides in this presentation treat the subject under the following headings: MaRIE XFEL Performance Parameters, Input Electron Beam Parameters, Undulator Design, Genesis Simulations, Risks, and Summary It is concluded that time-dependent Genesis simulations show the MaRIE XFEL can deliver the number of photons within the required bandwidth, provided a number of assumptions are met; the highest risks are associated with the electron beam driving the XFEL undulator; and risks associated with the undulator and/or distributed seeding technique may be evaluated or retired by performing early validation experiments.

  16. Satellite-based detection of volcanic sulphur dioxide from recent eruptions in Central and South America

    Directory of Open Access Journals (Sweden)

    D. Loyola


    Full Text Available Volcanic eruptions can emit large amounts of rock fragments and fine particles (ash into the atmosphere, as well as several gases, including sulphur dioxide (SO2. These ejecta and emissions are a major natural hazard, not only to the local population, but also to the infrastructure in the vicinity of volcanoes and to aviation. Here, we describe a methodology to retrieve quantitative information about volcanic SO2 plumes from satellite-borne measurements in the UV/Visible spectral range. The combination of a satellite-based SO2 detection scheme and a state-of-the-art 3D trajectory model enables us to confirm the volcanic origin of trace gas signals and to estimate the plume height and the effective emission height. This is demonstrated by case-studies for four selected volcanic eruptions in South and Central America, using the GOME, SCIAMACHY and GOME-2 instruments.

  17. Birth of two volcanic islands in the southern Red Sea

    KAUST Repository

    Xu, Wenbin


    Submarine eruptions that lead to the formation of new volcanic islands are rare and far from being fully understood; only a few such eruptions have been witnessed since Surtsey Island emerged to the south of Iceland in the 1960s. Here we report on two new volcanic islands that were formed in the Zubair archipelago of the southern Red Sea in 2011–2013. Using high-resolution optical satellite images, we find that the new islands grew rapidly during their initial eruptive phases and that coastal erosion significantly modified their shapes within months. Satellite radar data indicate that two north–south-oriented dykes, much longer than the small islands might suggest, fed the eruptions. These events occurred contemporaneously with several local earthquake swarms of the type that typically accompany magma intrusions. Earthquake activity has been affecting the southern Red Sea for decades, suggesting the presence of a magmatically active zone that has previously escaped notice.


    International Nuclear Information System (INIS)

    F.V. Perry


    Basaltic volcanism poses a potential hazard to the proposed Yucca Mountain nuclear waste repository because multiple episodes of basaltic volcanism have occurred in the Yucca Mountain region (YMR) in the past 11 Ma. Intervals between eruptive episodes average about 1 Ma. Three episodes have occurred in the Quaternary at approximately 1.1 Ma (5 volcanoes), 350 ka (2 volcanoes), and 80 ka (1 volcano). Because Yucca Mountain lies within the Basin and Range Province, a significant portion of the pre-Quaternary volcanic history of the YMR may be buried in alluvial-filled basins. An exceptionally high-resolution aeromagnetic survey and subsequent drilling program sponsored by the U.S. Department of Energy (DOE) began in 2004 and is gathering data that will enhance understanding of the temporal and spatial patterns of Pliocene and Miocene volcanism in the region (Figure 1). DOE has convened a ten-member expert panel of earth scientists that will use the information gathered to update probabilistic volcanic hazard estimates originally obtained by expert elicitation in 1996. Yucca Mountain is a series of north-trending ridges of eastward-tilted fault blocks that are bounded by north to northeast-trending normal faults. Topographic basins filled with up to 500 m of alluvium surround it to the east, south and west. In the past several decades, nearly 50 holes have been drilled in these basins, mainly for Yucca Mountain Project Site Characterization and the Nye County Early Warning Drilling Program. Several of these drill holes have penetrated relatively deeply buried (300-400 m) Miocene basalt; a Pliocene basalt dated at 3.8 Ma was encountered at a relatively shallow depth (100 m) in the northern Amargosa Desert (Anomaly B in Figure 1). The current drilling program is the first to specifically target and characterize buried basalt. Based on the new aeromagnetic survey and previous air and ground magnetic surveys (Connor et al. 2000; O'Leary et al. 2002), at least eight drill

  19. New K-Ar ages of volcanic rocks and associated mineralization in Canada Honda district, San Luis, Argentina

    International Nuclear Information System (INIS)

    Urbina, N.E.; Oggier, F.P


    New K-Ar ages in the Late Tertiary gold-bearing volcanic belt of the Sierras Pampeanas of San Luis, Argentina are presented. At Canada Honda district, an age of 8.49±0.2 Ma yielded by Cerro del Valle andesite indicates that the dome emplacement postdates the Diente Verde eruptive event. An even younger age of 7.3±0.2 Ma was obtained for illite from hydrothermal alteration at La Reynela mineralization which is hosted by Cerro del Valle andesite (au)

  20. Volcanism and associated hazards: the Andean perspective (United States)

    Tilling, R. I.


    Andean volcanism occurs within the Andean Volcanic Arc (AVA), which is the product of subduction of the Nazca Plate and Antarctica Plates beneath the South America Plate. The AVA is Earth's longest but discontinuous continental-margin volcanic arc, which consists of four distinct segments: Northern Volcanic Zone, Central Volcanic Zone, Southern Volcanic Zone, and Austral Volcanic Zone. These segments are separated by volcanically inactive gaps that are inferred to indicate regions where the dips of the subducting plates are too shallow to favor the magma generation needed to sustain volcanism. The Andes host more volcanoes that have been active during the Holocene (past 10 000 years) than any other volcanic region in the world, as well as giant caldera systems that have produced 6 of the 47 largest explosive eruptions (so-called "super eruptions") recognized worldwide that have occurred from the Ordovician to the Pleistocene. The Andean region's most powerful historical explosive eruption occurred in 1600 at Huaynaputina Volcano (Peru). The impacts of this event, whose eruptive volume exceeded 11 km3, were widespread, with distal ashfall reported at distances >1000 km away. Despite the huge size of the Huaynaputina eruption, human fatalities from hazardous processes (pyroclastic flows, ashfalls, volcanogenic earthquakes, and lahars) were comparatively small owing to the low population density at the time. In contrast, lahars generated by a much smaller eruption (Colombia) killed about 25 000 people - the worst volcanic disaster in the Andean region as well as the second worst in the world in the 20th century. The Ruiz tragedy has been attributed largely to ineffective communications of hazards information and indecisiveness by government officials, rather than any major deficiencies in scientific data. Ruiz's disastrous outcome, however, together with responses to subsequent hazardous eruptions in Chile, Colombia, Ecuador, and Peru has spurred significant

  1. Electrostatic phenomena in volcanic eruptions

    Energy Technology Data Exchange (ETDEWEB)

    Lane, S J; James, M R; Gilbert, J S, E-mail: [Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ (United Kingdom)


    Electrostatic phenomena have long been associated with the explosive eruption of volcanoes. Lightning generated in volcanic plumes is a spectacular atmospheric electrical event that requires development of large potential gradients over distances of up to kilometres. This process begins as hydrated liquid rock (magma) ascends towards Earth's surface. Pressure reduction causes water supersaturation in the magma and the development of bubbles of supercritical water, where deeper than c. 1000 m, and water vapour at shallower depths that drives flow expansion. The generation of high strain rates in the expanding bubbly magma can cause it to fracture in a brittle manner, as deformation relaxation timescales are exceeded. The brittle fracture provides the initial charge separation mechanism, known as fractoemission. The resulting mixture of charged silicate particles and ions evolves over time, generating macro-scale potential gradients in the atmosphere and driving processes such as particle aggregation. For the silicate particles, aggregation driven by electrostatic effects is most significant for particles smaller than c. 100 {mu}m. Aggregation acts to change the effective aerodynamic behaviour of silicate particles, thus altering the sedimentation rates of particles from volcanic plumes from the atmosphere. The presence of liquid phases also promotes aggregation processes and lightning.

  2. Fabrication technology for ODS Alloy MA957

    International Nuclear Information System (INIS)

    ML Hamilton; DS Gelles; RJ Lobsinger; MM Paxton; WF Brown


    A successful fabrication schedule has been developed at Carpenter Technology Corporation for the production of MA957 fuel and blanket cladding. Difficulties with gun drilling, plug drawing and recrystallization were overcome to produce a pilot lot of tubing. This report documents the fabrication efforts of two qualified vendors and the support studies performed at WHC to develop the fabrication-schedule

  3. Salatoimikud : ma tahan uskuda / Mart Rummo

    Index Scriptorium Estoniae

    Rummo, Mart


    USA sarjale "The X-Files" põhinev teine järjefilm "Salatoimikud: Ma tahan uskuda" ("The X-Files: I Want to Believe") : režissöör Chris Carter : peaosades David Duchovny, Gillian Anderson : Ameerika Ühendriigid - Kanada 2008

  4. Cenozoic volcanic rocks of Saudi Arabia (United States)

    Coleman, R.G.; Gregory, R.T.; Brown, G.F.


    The Cenozoic volcanic rocks of Saudi Arabia cover about 90,000 km2, one of the largest areas of alkali olivine basalt in the world. These volcanic rocks are in 13 separate fields near the eastern coast of the Red Sea and in the western Arabian Peninsula highlands from Syria southward to the Yemen Arab Republic.

  5. The structural architecture of the Los Humeros volcanic complex and geothermal field, Trans-Mexican Volcanic Belt, Central Mexico (United States)

    Norini, Gianluca; Groppelli, Gianluca; Sulpizio, Roberto; Carrasco Núñez, Gerardo; Davila Harris, Pablo


    the structural features of the studied area. The integration of these structural data with available stratigraphy, geological maps and well logs is used to propose a new model of the caldera and geothermal field. As a result of our study, we interpret the Xaltipan and Zaragoza calderas mainly as trap-door structures. These calderas affected a cone-shaped volcanic sequence, formed mainly by effusive products emitted in the pre-caldera forming phase and now hosting the geothermal reservoir (11-1.5 Ma). The main ring faults of the two calderas are buried and sealed by widespread post-calderas volcanic products, and for this reason probably do not have enough secondary permeability to be main channels for hydrothermal fluid circulation. Active, fast-moving subvertical faults have been identified inside the Zaragoza caldera depression. These structures affect recent post-caldera pyroclastic deposits and probably are related both to active resurgence inside the caldera and to regional faults NW-SE striking. The presence of active faults generating high secondary permeability is the most important structural element shaping the geothermal reservoir. Future plans of expansion of the geothermal field should focus on these active faults, considering their geometry at depth and the whole structural architecture of the Los Humeros volcanic complex.

  6. Quaternary basaltic volcanism in the Payenia volcanic province, Argentina

    DEFF Research Database (Denmark)

    Søager, Nina

    primitive basalts and trachybasalts but also more evolved samples from the retroarc region and the larger volcanoes Payún Matrú and Payún Liso are presented. The samples cover a broad range of compositions from intraplate lavas similar to ocean island basalts to arc andesites. A common feature found...... are isotopically similar to the Andean Southern Volcanic Zone arc rocks and their mantle source possibly resembled the source of South Atlantic N-MORB prior to addition of fluids and melts from the subduction channel. However, it must have been more enriched than the estimates of depleted upper mantle from...... the lithosphere is thinnest and possibly in areas of elevated mantle temperatures. The pyroxenite melts formed at deeper levels react with the surrounding peridotite and thereby changes composition leading to eruption of melts which experienced variable degrees of melt-peridotite interaction. This can presumably...

  7. Stratigraphy, age and correlation of middle Pleistocene silicic tephras in the Auckland region, New Zealand : a prolific distal record of Taupo Volcanic Zone volcanism

    International Nuclear Information System (INIS)

    Alloway, B.V.; Westgate, J.; Pillans, B.; Pearce, N.; Newnham, R.; Byrami, M.; Aarburg, S.


    Coastal sections in the Auckland region reveal highly carbonaceous and/or highly weathered clay-dominated cover-bed successions with numerous discrete distal volcanic ash (tephra) layers, fluvially reworked siliciclastic (tephric) deposits, and two widely distributed pyroclastic density current (PDC) deposits generated from explosive silicic volcanism within the Taupo Volcanic Zone (TVZ). The younger of the two PDC deposits (informally named Waiuku tephra) is glass-isothermal plateau fission-track (ITPFT) dated at 1.00 ± 0.03 Ma and occurs in a normal polarity interval interpreted as the Jaramillo Subchron. Waiuku tephra is correlated with Unit E sourced from the Mangakino Volcanic Centre of the TVZ. Waiuku tephra can be subdivided into two distinctive units enabling unequivocal field correlation: a lower stratified unit (dominantly pyroclastic surge with fall component) and an upper massive to weakly stratified unit (pyroclastic flow). At many sites in south Auckland, Waiuku tephra retains basal 'surge-like' beds (<1.4 m thickness). This provides clear evidence for primary emplacement and is an exceptional feature considering the c. 200 km this PDC has travelled from its TVZ source area. However, at many other Auckland sites, Waiuku tephra displays transitional sedimentary characteristics indicating lateral transformation from hot, gas-supported flow/surge into water-supported mass flow and hyperconcentrated flow (HCF) deposits. The older PDC deposit is dated at 1.21 ± 0.09 Ma, is enveloped by tephras that are ITPFT-dated at 1.14 ± 0.06 Ma (above) and 1.21 ± 0.06 Ma (below), respectively, and occurs below a short normal polarity interval (Cobb Mountain Subchron) at c. 1.19 Ma. This PDC deposit, correlated with Ongatiti Ignimbrite sourced from the Mangakino Volcanic Centre of TVZ, has laterally transformed from a gas-supported, fine-grained pyroclastic flow deposit at Oruarangi, Port Waikato, into a water-supported volcaniclastic mass flow deposit farther north

  8. Rb-Sr and Ar-Ar systematics of Malani volcanic rocks of southwest Rajasthan: evidence for a younger post-crystallization thermal event

    International Nuclear Information System (INIS)

    Rathore, S.S.; Srivastava, R.K.


    A new Rb-Sr age of 779 ± 10 Ma has been obtained for a suite of andesite-dacite-rhyolite from the Malani igneous province of southwestern Rajasthan, dated earlier at 745 ± 10 Ma by Crawford and Compston (1970). The associated basalts may be slightly younger than the felsic volcanics and have a mantle source. The felsic volcanics on the other hand were most probably derived by fractional crystallization of a crustal magma. 40 Ar- 39 Ar systematics of three samples viz., a basalt, a dacite and a rhyolite show disturbed age spectra indicating a thermal event around 500-550 Ma ago. This secondary thermal event is quite wide-spread and possibly related to the Pan-African thermo-tectonic episode observed in the Himalayas and south India. (author). 38 refs., 5 figs., 2 tabs

  9. Timing of Late Cretaceous Gulf Coast volcanism and chronostratigraphic constraints on deposition of the Ripley Formation from a newly recognized bentonite bed, Pontotoc County, Mississippi (United States)

    Vitale, E. J.; Gifford, J.; Platt, B. F.


    The Upper Cretaceous Ripley Formation is present throughout the Mississippi (MS) Embayment and contains local bentonite lenses related to regional volcanism. The Pontotoc bentonite is such a lens located near the town of Pontotoc, MS, that was strip-mined and has not been accessible since reclamation of the land. Recent investigations in Pontotoc County south of the Pontotoc bentonite site resulted in the discovery of a previously unknown bentonite bed. Litho- and biostratigraphy indicate that the bentonite is younger than known volcanism from MS. The purposes of the present investigation are 1) to test whether the new bentonite bed is correlative to the Pontotoc bentonite & 2) to recover volcanogenic zircons for U-Pb dating to better constrain timing of volcanism and chronostratigraphy of the Ripley Fm. Outcrops in an active sand pit in the field area expose 2.5 m of fine sand, and an upper gradational contact with an overlying 2.5 m of sandy clay, containing the bentonite bed. Two trenches were excavated through the outcrop, and in each trench a stratigraphic section was measured and bulk samples collected for zircons. Sampling began in the lower bounding sand and continued upsection in 1 m intervals, corresponding to the gradational contact with the bentonite, and 2 locations within the bentonite. The Ripley Fm. consists of 73 m of fossiliferous clay, sand, and calcareous sand beds. Recent stratigraphic revisions of the lateral facies in MS recognize a lower transitional clay facies, a limestone, marl, and calcareous sand facies, a sandy upper Ripley facies, and the formally named Chiwapa Sandstone Member. Ammonite biostratigraphy places the contact between the Chiwapa and the overlying Owl Creek/Prairie Bluff at 68.5 Ma. Unlike the mined area north of Pontotoc where the bentonite is within the Chiwapa, the bed here is directly above the Chiwapa section and its upper contact represents the Ripley Fm. / Owl Creek Fm. contact. Where the bentonite is present, it

  10. The Lanzarote Geodynamic Laboratory: new capabilities for monitoring of volcanic activity at Canary Islands (United States)

    Arnoso, J.; Vélez, E. J.; Soler, V.; Montesinos, F. G.; Benavent, M.


    The volcanic island of Lanzarote is located at the northeastern end of the Canary Islands. Together with Fuerteventura Island, Lanzarote constitutes the emergent part of the East Canary Ridge, which presents a NNE-SSW volcanic alignment. Last eruptive events took place in 1824 and during the period 1730-1736, which is the largest to occur in the archipelago and throw out about 1.3 km3 of volcanic materials. The Lanzarote Geodynamic Laboratory (LGL) was created in 1986 with the idea of making Lanzarote as a natural laboratory to carry out studies in order to acquire more knowledge about its origin, present status and evolution (Vieira et al., 1991; 2006). The LGL has a multidisciplinary scientific purpose and, among others, various objectives are devoted to investigate mass distribution in the Earth system and surface displacements associated to volcanic and/or seismic activity in the island. The influence of LGL is extended throughout the whole geographical area of Lanzarote, including small islands located at the north. The laboratory has 3 observing modules distributed along the island according to its infrastructure and scientific objectives, where more than 70 sensors are recording continuously gravity variations, ground deformations, sea level, seismic activity, meteorological parameters, etc. All these observations are supplemented by periodic measurement of geodetic and geophysical networks that allow us to make studies at local, insular and regional scales. The application of geodetic and geophysical techniques to identify geodynamic signals related to volcanic processes is then a permanent research activity of the laboratory. Nowadays, this fact becomes more interesting due to the ongoing volcanic eruption that is taking place in other island of the Canary Archipelago, El Hierro, since past July 2011. That is, the multidisciplinary research carry on up to now at the LGL allow us to apply multiparameter observations of different kinds of volcanic

  11. Timing and Duration of Volcanism in the North Atlantic Igneous Province: Implications for Geodynamics and Links to the Iceland Hotspot

    DEFF Research Database (Denmark)

    Storey, M.; Duncan, R. A.; Tegner, Christian


    estimates of erupted magmas and their cumulates to calculate melt production rates for the early Tertiary flood basalts of East Greenland and the Faeroes Islands. The lavas lie at opposite ends of the Greenland-Iceland-Faeroes Ridge, the postulated Iceland hotspot track, and record volcanic activity leading...... of plate separation. The upper part of this crust comprises seismically imaged, seaward-dipping, subaerially erupted lavas. By  50 Ma, eruption rates had diminished drastically and volcanic activity had narrowed to a much restricted portion of the East Greenland margin, at the western end of the Greenland......We combine new and published 40Ar/39Ar age determinations from incremental heating experiments on whole rocks and mineral separates to assess the timing, duration and distribution of volcanic activity during construction of the North Atlantic Igneous Province. We use these ages together with volume...

  12. Geomorphological Approach for Regional Zoning In The Merapi Volcanic Area

    Directory of Open Access Journals (Sweden)

    Langgeng Wahyu Santosa


    Full Text Available Geomorphologial approach can be used as the basic for identifying and analyzing the natural resources potentials, especially in volcanic landscape. Based on its geomorphology, Merapi volcanic landscape can be divided into 5 morphological units, i.e.: volcanic cone, volcanic slope, volcanic foot, volcanic foot plain, and fluvio-volcanic plain. Each of these morphological units has specific characteristic and natural resources potential. Based on the condition of geomorphology, the regional zoning can be compiled to support the land use planning and to maintain the conservation of environmental function in the Merapi Volcanic area.

  13. Small volcanic eruptions and the stratospheric sulfate aerosol burden (United States)

    Pyle, David M.


    -based hyperspectral infrared measurements: application to the Eyjafjallajökull 2010 eruption J. Geophys. Res. 117 D00U16 Wiart P and Oppenheimer C 2005 Large magnitude silicic volcanism in north Afar: the Nabro volcanic range and Ma'alalta volcano Bull. Volcanol. 67 99-115

  14. Large Volcanic Rises on Venus (United States)

    Smrekar, Suzanne E.; Kiefer, Walter S.; Stofan, Ellen R.


    Large volcanic rises on Venus have been interpreted as hotspots, or the surface manifestation of mantle upwelling, on the basis of their broad topographic rises, abundant volcanism, and large positive gravity anomalies. Hotspots offer an important opportunity to study the behavior of the lithosphere in response to mantle forces. In addition to the four previously known hotspots, Atla, Bell, Beta, and western Eistla Regiones, five new probable hotspots, Dione, central Eistla, eastern Eistla, Imdr, and Themis, have been identified in the Magellan radar, gravity and topography data. These nine regions exhibit a wider range of volcano-tectonic characteristics than previously recognized for venusian hotspots, and have been classified as rift-dominated (Atla, Beta), coronae-dominated (central and eastern Eistla, Themis), or volcano-dominated (Bell, Dione, western Eistla, Imdr). The apparent depths of compensation for these regions ranges from 65 to 260 km. New estimates of the elastic thickness, using the 90 deg and order spherical harmonic field, are 15-40 km at Bell Regio, and 25 km at western Eistla Regio. Phillips et al. find a value of 30 km at Atla Regio. Numerous models of lithospheric and mantle behavior have been proposed to interpret the gravity and topography signature of the hotspots, with most studies focusing on Atla or Beta Regiones. Convective models with Earth-like parameters result in estimates of the thickness of the thermal lithosphere of approximately 100 km. Models of stagnant lid convection or thermal thinning infer the thickness of the thermal lithosphere to be 300 km or more. Without additional constraints, any of the model fits are equally valid. The thinner thermal lithosphere estimates are most consistent with the volcanic and tectonic characteristics of the hotspots. Estimates of the thermal gradient based on estimates of the elastic thickness also support a relatively thin lithosphere (Phillips et al.). The advantage of larger estimates of

  15. Geologic structure and volcanic history of the Yanaizu-Nishiyama (Okuaizu) geothermal field, Northeast Japan

    Energy Technology Data Exchange (ETDEWEB)

    Mizugaki, Keiko [Geological Survey of Japan, Geothermal Research Dept., Higashi Tsukuba (Japan)


    The Yanaizu-Nishiyama geothermal field, also known as Okuaizu, supports a 65 MWe geothermal power station. It is located in the western part of Fukushima Prefecture, northeast Japan. This field is characterised by rhyolitic volcanism of about 0.3-0.2 Ma that formed Sunagohara volcano. Drillcore geology indicates that volcanism began with a caldera-forming eruption in the center of this field, creating a 2-km-diameter funnel-shaped caldera. Subsequently, a fault-bounded block including this caldera subsided to form a 5-km-wide lake that accumulated lake sediments. Post-caldera volcanism formed lava domes and intrusions within the lake, and deposited ash-flow tuffs in and around the lake. The hydrothermal system of this field is strongly controlled by subvertical faults that have no relation to the volcanism. The principal production zone occurs at a depth of 1.0-2.6 km within fractured Neogene formations along two northwest-trending faults to the southeast of the caldera. These faults also formed fracture zones in the lake sediments, but there was no apparent offset of the sediments. Stratigraphic studies suggest that post-caldera activities of Sunagohara volcano have migrated southeastward to the present high-temperature zone. The source magma of Sunagohara volcano may contribute to the thermal potential of this field. (Author)

  16. Neogene seismites and seismic volcanic rocks in the Linqu area, Shandong Province, E China

    Directory of Open Access Journals (Sweden)

    Tian H.S.


    Full Text Available The Yishu Fault Zone runs through the centre of Shandong Province (E China; it is a deep-seated large fault system that still is active. Two volcanic faulted basins (the Shanwang and Linqu Basins in the Linqu area, west of the fault zone, are exposed to rifting, which process is accompanied by a series of tectonic and volcanic earthquakes with a magnitude of 5-8. Lacustrine sediments in the basins were affected by these earthquakes so that seismites with a variety of soft-sediment deformation structures originated. The seismites form part of the Shanwang Formation of the Linqu Group. Semi-consolidated fluvial conglomerates became deformed in a brittle way; these seismites are present at the base of the Yaoshan Formation. Intense earthquakes triggered by volcanic activity left their traces in the form of seismic volcanic rocks associated with liquefied-sand veins in the basalt/sand intercalations at the base of the Yaoshan Formation. These palaeo-earthquake records are dated around 14-10 Ma; they are responses to the intense tectonic extension and the basin rifting in this area and even the activity of the Yishu Fault Zone in the Himalayan tectonic cycle.

  17. The Chahnaly low sulfidation epithermal gold deposit, western Makran volcanic arc, southeastern Iran (United States)

    Sholeh, Ali; Rastad, Ebrahim; Huston, David L.; Gemmell, J. Bruce; Taylor, Ryan D.


    The Chahnaly low-sulfidation epithermal Au deposit and nearby Au prospects are located northwest of the intermittently active Bazman stratovolcano on the western end of the Makran volcanic arc, which formed as the result of subduction of the remnant Neo-Tethyan oceanic crust beneath the Lut block. The arc hosts the Siah Jangal epithermal and Kharestan porphyry prospects, near Taftan volcano, as well as the Saindak Cu-Au porphyry deposit and world-class Reko Diq Cu-Au porphyry deposit, near Koh-i-Sultan volcano to the east-northeast in Pakistan. The host rocks for the Chahnaly deposit include early Miocene andesite and andesitic volcaniclastic rocks that are intruded by younger dacitic domes. Unaltered late Miocene dacitic ignimbrites overlie these rocks. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) U-Pb zircon geochronology data yield ages between 21.8 and 9.9 Ma for the acidic-intermediate regional volcanism. The most recent volcanic activity of the Bazman stratovolcano involved extrusion of an olivine basalt during Pliocene to Quaternary times. Interpretation of geochemical data indicate that the volcanic rocks are synsubduction and calc-alkaline to subalkaline. The lack of a significant negative Eu anomaly, a listric-shaped rare earth element pattern, and moderate La/Yb ratios of host suites indicate a high water content of the source magma.

  18. Upper pliocene-lower pleistocene 40Ar/39Ar ages of Pudahuel ignimbrite (Diamante-Maipo volcanic complex), Central Chile (33.50S)

    International Nuclear Information System (INIS)

    Wall, R.M.; Lara, L.E.; Perez de Arce, C


    The Pudahuel Ignimbrite (Wall et al., 1996) is a characteristic pyroclastic flow deposit placed in the Central Depression, within the Maipo, Mapocho and Cachapoal valleys and, in the eastern side of the Andes, at Yaucha and Papagayos rivers as well (Harrington, 1989; Guerstein, 1993). Close to Santiago, Pudahuel Ignimbrite reaches 40 m in thickness (Dragicevic, 1962) which decreces up to 5 m 60 km to the west. The deposit is compounded by ash and lapilli size pumice within a cineritic matrix with shards, crystals and pumice fragments. Facies of both, laminar and turbulent flow regime can be distinguished, the latter prevailing near topographic barriers and on river plain floors. There, traction structures like cross-bedding and important amount of litic clasts are characteristic. Pumices are rhyolitic in composition (ca. 75% SiO 2 ; Stern et al., 1984; Guerstein, 1993) and have few 0.5-2 mm long biotite crystals. Two 40 Ar/ 39 Ar step-heating experiments on biotite from pumices of two localities, Maipu (Santiago) and Bollenar (Melipilla), show plateau ages of 2.3±0.3 Ma (RW-371) and 2.2±0.3 Ma (RW-1009). In both cases, the first step of the experiment indicates loss of Ar from the cristal rims wich was removed for the plateau calculus only in the second case. For the RW-371 sample an inverse isocrone age of 1.4±0.8 Ma (MSWD: 0.98) was obtained. Previously, the Pudahuel Ignimbrite was dated by Stern et al. (1984) in ca. 450 ka using zircon fission-tracks. Although inconsistent with our new ages, these pleistocene age seemed coherent with the discovery of an Antifer (deer) bone by Tavera (1978) within the ignimbrite close to Santiago. Nevertheless, as was apointed by Tavera (1978) himself, the Antifer genus is recognized in Argentina in the Pliocene-Quaternary interval and make possible a review of the well known 'pleistocene' mammal vertebrate associations in Chile. Another consequence of the new possible pliocene ages is that, since the ignimbrite does not show

  19. Metallogenic hydrothermal solution system of post volcanic magma in Xiangshan ore field

    International Nuclear Information System (INIS)

    Xu Hengli; Shao Fei; Zou Maoqin


    This paper has systematically described uranium metallogenic characteristics of Xiangshan ore field.Sources of metallogenic materials are discussed in different temporal and spatial scale. Combining with background analysis of metallogenic tectonic-magmatic-geodynamics, formation and evolution of metallogenic hydrothermal solution system in Xiangshan volcanic basin are studied. Metallogenic hydrothermal solution system in Xiangshan ore field is considered as the objective product of systematic evolution of hydrothermal solution in post volcanic magma constrained by regional tectonic environment. In time scale, metallogenic hydrothermal solution system developed for about 50 Ma, but its active spaces varied in different time domains. So temporal and spatial distribution of uranium mineralization is constrained. Further exploration for the ore field is also suggested in this paper. (authors)

  20. Dinasour extinction and volcanic activity (United States)

    Gledhill, J. A.

    There is at present some controversy about the reason for the mass extinction of dinosaurs and other forms of life at the end of the Cretaceous. A suggestion by Alvarez et al. [1980] that this was due to the collision of the earth with a meteorite 10 km or so in diameter has excited considerable interest [Silver and Schultz, 1982] and also some criticism [Stanley, 1984]. A recent publication [Wood, 1984] describing the catastrophic effects of a relatively minor lava flow in Iceland suggests that intense volcanic activity could have played a large part in the extinctions. In this letter it is pointed out that the Deccan lava flows in India took place in the appropriate time and may well have been of sufficient magnitude to be a major factor in the Cretaceous-Tertiary (C-T) boundary catastrophe.

  1. Mass and Reliability System (MaRS) (United States)

    Barnes, Sarah


    The Safety and Mission Assurance (S&MA) Directorate is responsible for mitigating risk, providing system safety, and lowering risk for space programs from ground to space. The S&MA is divided into 4 divisions: The Space Exploration Division (NC), the International Space Station Division (NE), the Safety & Test Operations Division (NS), and the Quality and Flight Equipment Division (NT). The interns, myself and Arun Aruljothi, will be working with the Risk & Reliability Analysis Branch under the NC Division's. The mission of this division is to identify, characterize, diminish, and communicate risk by implementing an efficient and effective assurance model. The team utilizes Reliability and Maintainability (R&M) and Probabilistic Risk Assessment (PRA) to ensure decisions concerning risks are informed, vehicles are safe and reliable, and program/project requirements are realistic and realized. This project pertains to the Orion mission, so it is geared toward a long duration Human Space Flight Program(s). For space missions, payload is a critical concept; balancing what hardware can be replaced by components verse by Orbital Replacement Units (ORU) or subassemblies is key. For this effort a database was created that combines mass and reliability data, called Mass and Reliability System or MaRS. The U.S. International Space Station (ISS) components are used as reference parts in the MaRS database. Using ISS components as a platform is beneficial because of the historical context and the environment similarities to a space flight mission. MaRS uses a combination of systems: International Space Station PART for failure data, Vehicle Master Database (VMDB) for ORU & components, Maintenance & Analysis Data Set (MADS) for operation hours and other pertinent data, & Hardware History Retrieval System (HHRS) for unit weights. MaRS is populated using a Visual Basic Application. Once populated, the excel spreadsheet is comprised of information on ISS components including

  2. Diffuse volcanic emissions of carbon dioxide from Vulcano Island, Italy. (United States)

    Baubron, J C; Allard, P; Toutain, J P


    RECENT investigations on Mount Etna (Sicily)(1-3) have revealed that volcanoes may release abundant carbon dioxide not only from their active craters, but also from their flanks, as diffuse soil emanations. Here we present analyses of soil gases and air in water wells on Vulcano Island which provide further evidence of such lateral degassing. Nearly pure carbon dioxide, enriched in helium and radon, escapes from the slopes of the Fossa active cone, adding a total output of 30 tonnes per day to the fumarolic crater discharge ( 180 tonnes CO(2) per day). This emanation has similar He/CO(2) and (13)C/(12)C ratios to those of the crater fumaroles (300%ndash;500 degrees C) and therefore a similar volcanic origin. Gases rich in carbon dioxide also escape at sea level along the isthmus between the Fossa and Vulcanello volcanic cones, but their depletion in both He and (13)C suggests a distinct source. Diffuse volcanic gas emanations, once their genetic link with central fumarole degassing has been demonstrated, can be used for continuous volcano monitoring, at safe distances from active craters. Such monitoring has been initiated at Vulcano, where soil and well emanations of nearly pure CO(2) themselves represent a threat to the local population.

  3. Volcanic risk perception in the Campi Flegrei area (United States)

    Ricci, T.; Barberi, F.; Davis, M. S.; Isaia, R.; Nave, R.


    enough information about the possible effects of an eruption. In addition, residents' sense of community was significantly positively correlated with both confidence in local authorities and Civil Protection as well as residents' feelings of self efficacy regarding their ability to protect themselves from a potential eruption. These results indicate that most residents of Campi Flegrei, while aware of the volcanic threat posed by Vesuvio, are not familiar with more local volcanic hazards in their area. This, coupled with little knowledge about the Emergency Plan and the very low level of information residents have about the effects of a possible eruption, suggests that authorities, in collaboration with the scientific community, should direct their efforts to better educate and inform the population about volcanic hazards and the Emergency Plan, and that such efforts could be facilitated by trying to encourage stronger community bonds.

  4. The unzipping of Africa and South America; New insights from the Etendeka and younger volcanic events along the Angola/Namibia margin. (United States)

    Jerram, D. A.


    The volcanic margin along Angola is relatively poorly constrained. This study uses new petrographic, geochronological and geochemical observations on a new sample set collected along the margin to help understand the various types and relative timings of volcanic events along the margin. This new study has identified 3 main volcanic events that occur at ~100Ma (Sumbe event 1), 90-92Ma (Serra de Neve (SDN)-Elefantes event 2) and 80-81Ma (Namibe event 3), with the oldest event in the north of the margin and younging southwards. This is contrasting with the main Etendeka pulse in Namibia at around 130 Ma. There is a marked variety of igneous rocks along the margin with a grouping of evolved alkaline rocks in the central SDN-Elefantes section, basic submarine volcanics in the north, and basanite eruptions in the southern section. There is some overlap with geochemical types along the margin. The Sumbe event contains predominantly submarine volcanics and shallow Intrusions. SDN-Elefantes rocks have a mixed type but with a distinctive feldspar rich evolved alkali suite of rocks (nepheline syenites and variations around this composition) which occur as lava flows and shallow intrusions as well as making up the core of the SDN complex. The SDN complex itself is analogous in size to the main volcanic centres in Namibia (such as Messum, Brandberg etc.) and suggests that large volcanic feeding centres are still active along the margin as young as 90ma. These in turn will form large volcano-topographic features. In the south the Ponta Negra and Canico sites mainly contain basanites in the form of lava flows, invasive flows and shallow intrusions. At Canico one intrusive plug was sampled with a similar composition to the evolved SDN-Elefantes suite. In all three events it is clear that the volcanic systems have interacted with the sedimentary systems, in some cases dynamically, in others with regional implications for volcano-tectonic uplift. Specific thanks is given for

  5. MaGate Simulator: A Simulation Environment for a Decentralized Grid Scheduler (United States)

    Huang, Ye; Brocco, Amos; Courant, Michele; Hirsbrunner, Beat; Kuonen, Pierre

    This paper presents a simulator for of a decentralized modular grid scheduler named MaGate. MaGate’s design emphasizes scheduler interoperability by providing intelligent scheduling serving the grid community as a whole. Each MaGate scheduler instance is able to deal with dynamic scheduling conditions, with continuously arriving grid jobs. Received jobs are either allocated on local resources, or delegated to other MaGates for remote execution. The proposed MaGate simulator is based on GridSim toolkit and Alea simulator, and abstracts the features and behaviors of complex fundamental grid elements, such as grid jobs, grid resources, and grid users. Simulation of scheduling tasks is supported by a grid network overlay simulator executing distributed ant-based swarm intelligence algorithms to provide services such as group communication and resource discovery. For evaluation, a comparison of behaviors of different collaborative policies among a community of MaGates is provided. Results support the use of the proposed approach as a functional ready grid scheduler simulator.

  6. Correlating The Star Formation Histories Of MaNGA Galaxies With Their Past AGN Activity (United States)

    Gonzalez Ortiz, Andrea


    We investigate active galactic nuclei (AGN) as a primary mechanism affecting star formation in MaNGA galaxies. Using the Pipe3D code, we modeled the stellar population from MaNGA spectra and derived the star formation histories of 53 AGN host galaxies. We seek to compare the star formation histories of the host galaxies of AGN with the ages of their radio lobes to better understand the role of AGN feedback in the star formation histories of MaNGA galaxies. MaNGA (Mapping Nearby Galaxies at APO) is one of the three core programs in the fourth generation Sloan Digital Sky Survey(SDSS). MaNGA will investigate the internal kinematics of nearly 10,000 local galaxies through dithered observations using fiber integral field units (IFUs) that vary in diameter from 12" (19 fibers) to 32" (127 fibers). In this poster, we present initial results on the star formation histories of MaNGA AGN host galaxies. This work was supported by the SDSS Research Experience for Undergraduates program, which is funded by a grant from Sloan Foundation to the Astrophysical Research Consortium.

  7. Petrography of the Paleogene Volcanic Rocks of the Sierra Maestra, Southeastern Cuba (United States)

    Bemis, V. L.


    This study is a petrographic analysis of over 200 specimens of the Paleogene volcanic rocks of the Sierra Maestra (Southerneastern Cuba), a key structure in the framework of the northern Caribbean plate boundary evolution. The purpose of this study is to understand the eruptive processes and the depositional environments. The volcanic sequence in the lower part of the Sierra Maestra begins with highly porphyritic pillow lavas, topped by massive tuffs and autoclastic flows. The presence of broken phenocrystals, palagonitic glass and hyaloclastites in this section of the sequence suggests that the prevalent mode of eruption was explosive. The absence of welding in the tuffs suggests that the rocks were emplaced in a deep submarine environment. Coherent flows, much less common than the massive tuffs, show evidence of autoclastic fracturing, also indicating low temperature-submarine environments. These observations support the hypothesis that the Sierra Maestra sequence may be neither part of the Great Antilles Arc of the Mesozoic nor any other fully developed volcanic arc, rather a 250 km long, submarine eruptive system of dikes, flows and sills, most likely a back-arc structure. The volcanic rocks of the upper sequence are all very fine grained, reworked volcaniclastic materials, often with the structures of distal turbidities, in mode and texture similar to those drilled on the Cayman Rise. This study suggests that the Sierra Maestra most likely records volcanism of diverse sources: a local older submarine source, and one or more distal younger sources, identifiable with the pan-Caribbean volcanic events of the Tertiary.

  8. Status of volcanic hazard studies for the Nevada Nuclear Waste Storage Investigations

    International Nuclear Information System (INIS)

    Crowe, B.M.; Vaniman, D.T.; Carr, W.J.


    Volcanism studies of the Nevada Test Site (NTS) region are concerned with hazards of future volcanism with respect to underground disposal of high-level radioactive waste. The hazards of silicic volcanism are judged to be negligible; hazards of basaltic volcanism are judged through research approaches combining hazard appraisal and risk assessment. The NTS region is cut obliquely by a N-NE trending belt of volcanism. This belt developed about 8 Myr ago following cessation of silicic volcanism and contemporaneous with migration of basaltic activity toward the southwest margin of the Great Basin. Two types of fields are present in the belt: (1) large-volume, long-lived basalt and local rhyolite fields with numerous eruptive centers and (2) small-volume fields formed by scattered basaltic scoria cones. Late Cenozoic basalts of the NTS region belong to the second field type. Monogenetic basalt centers of this region were formed mostly by Strombolian eruptions; Surtseyean activity has been recognized at three centers. Geochemically, the basalts of the NTS region are classified as straddle A-type basalts of the alkalic suite. Petrological studies indicate a volumetric dominance of evolved hawaiite magmas. Trace- and rare-earth-element abundances of younger basalt ( - 8 to 10 - 10 as calculated for a 1-yr period. Potential disruptive and dispersal effects of magmatic penetration of a repository are controlled primarily by the geometry of basalt feeder systems, the mechanism of waste incorporation in magma, and Strombolian eruption processes

  9. Volcanic risk perception of young people in the urban areas of Vesuvius: Comparisons with other volcanic areas and implications for emergency management (United States)

    Carlino, S.; Somma, R.; Mayberry, G.C.


    More than 600 000 people are exposed to volcanic risk in the urban areas near the volcano, Vesuvius, and may need to be evacuated if there is renewed volcanic activity. The success of a future evacuation will strongly depend on the level of risk perception and preparedness of the at-risk communities during the current period of quiescence. The volcanic risk perception and preparedness of young people is of particular importance because hazard education programs in schools have been shown to increase the clarity of risk perception and students often share their knowledge with their parents. In order to evaluate young people's risk perception and preparedness for a volcanic crisis, a multiple choice questionnaire was distributed to 400 high-school students in three municipalities located close to the volcano. The overall results suggest that despite a 60-year period of quiescence at Vesuvius, the interviewed students have an accurate perception of the level of volcanic risk. On the other hand, the respondents demonstrate a clear lack of understanding of volcanic processes and their related hazards. Also, the interviewed students show high levels of fear, poor perceived ability to protect themselves from the effects of a future eruption, and insufficient knowledge of the National Emergency Plan for Vesuvian Area (NEPVA). The latter result suggests that in comparison with volcanic crises in other regions, during a future eruption of Vesuvius, there may not be enough time to educate the large number of people living near the volcano about how to appropriately respond. The inadequate risk education and preparedness of respondents implies that a strong effort is needed to improve communication strategies in order to facilitate successful evacuations. Therefore, it is important to take advantage of the present period of quiescence at Vesuvius to improve the accuracy of risk perception of youth in local communities. ?? 2008.

  10. Model for Analysis of the Energy Demand (MAED) users' manual for version MAED-1

    International Nuclear Information System (INIS)


    This manual is organized in two major parts. The first part includes eight main sections describing how to use the MAED-1 computer program and the second one consists of five appendices giving some additional information about the program. Concerning the main sections of the manual, Section 1 gives a summary description and some background information about the MAED-1 model. Section 2 extends the description of the MAED-1 model in more detail. Section 3 introduces some concepts, mainly related to the computer requirements imposed by the program, that are used throughout this document. Sections 4 to 7 describe how to execute each of the various programs (or modules) of the MAED-1 package. The description for each module shows the user how to prepare the control and data cards needed to execute the module and how to interpret the printed output produced. Section 8 recapitulates about the use of MAED-1 for carrying out energy and electricity planning studies, describes the several phases normally involved in this type of study and provides the user with practical hints about the most important aspects that need to be verified at each phase while executing the various MAED modules

  11. Depleted arc volcanism in the Alboran Sea and shoshonitic volcanism in Morocco: geochemical and isotopic constraints on Neogene tectonic processes (United States)

    Gill, R. C. O.; Aparicio, A.; El Azzouzi, M.; Hernandez, J.; Thirlwall, M. F.; Bourgois, J.; Marriner, G. F.


    arising from convective thinning of over-thickened lithosphere. Our data support recent models in which subsidence is caused by westward rollback of an eastward-dipping subduction zone beneath the westernmost Mediterranean. Moreover, severance of the lithosphere at the edges of the rolling-back slab provides opportunities for locally melting lithospheric mantle, providing a possible explanation for the shoshonitic volcanism seen in northern Morocco and more sporadically in SE Spain.

  12. Cinéma en France

    Directory of Open Access Journals (Sweden)

    Michel VIGOUROUX


    Full Text Available Le cinéma est l’objet de bases de données exhaustives sur les équipements et les fréquentations. Les données sur les salles permettent d’identifier le phénomène de concentration de propriété et d’exploitation. La perspective dynamique peut être observée sur 45 ans. À l’échelle régionale, on peut apprécier le dynamisme du cinéma en haute montagne alpine et la différence de réseaux sur le territoire (France de l’Ouest.

  13. Search for possible relationship between volcanic ash particles and thunderstorm lightning activity (United States)

    Várai, A.; Vincze, M.; Lichtenberger, J.; Jánosi, I. M.


    Explosive volcanic eruptions that eject columns of ash from the crater often generate lightning discharges strong enough to be remotely located by very low frequency radio waves. A fraction of volcanic ash particles can stay and disperse long enough to have an effect on weather phenomena days later such as thunderstorms and lightnings. In this work we report on lightning activity analysis over Europe following two recent series of volcanic eruptions in order to identify possible correlations between ash release and subsequent thunderstorm flash frequency. Our attempts gave negative results which can be related to the fact that we have limited information on local atmospheric variables of high enough resolution, however lightning frequency is apparently determined by very local circumstances.

  14. Search for possible relationship between volcanic ash particles and thunderstorm lightning activity

    International Nuclear Information System (INIS)

    Várai, A; Vincze, M; Jánosi, I M; Lichtenberger, J


    Explosive volcanic eruptions that eject columns of ash from the crater often generate lightning discharges strong enough to be remotely located by very low frequency radio waves. A fraction of volcanic ash particles can stay and disperse long enough to have an effect on weather phenomena days later such as thunderstorms and lightnings. In this work we report on lightning activity analysis over Europe following two recent series of volcanic eruptions in order to identify possible correlations between ash release and subsequent thunderstorm flash frequency. Our attempts gave negative results which can be related to the fact that we have limited information on local atmospheric variables of high enough resolution, however lightning frequency is apparently determined by very local circumstances.

  15. New chronological and geochemical constraints on the genesis and geological evolution of Ponza and Palmarola Volcanic Islands (Tyrrhenian Sea, Italy) (United States)

    Cadoux, Anita; Pinti, Daniele L.; Aznar, Cyril; Chiesa, Sergio; Gillot, Pierre-Yves


    A new geochronological and geochemical study of the volcanic rocks of the Ponza and Palmarola Islands, Pontine Archipelago, has been carried out. This archipelago is located along the boundary between the Italian continental shelf and the opening Tyrrhenian basin. It is a key area to study volcanism related to the opening of the Tyrrhenian Sea. Ponza is the oldest felsic magmatic manifestation in the central Tyrrhenian area. Previous studies suggested that Ponza volcanic activity began before 5 Ma. Twenty-five new K-Ar ages constrain the volcanic activity (rhyolitic hyaloclastites and dykes) to the last 4.2 Ma, with two episodes of quiescence between 3.7 and 3.2 Ma and between 2.9 and 1.0 Ma. A new volcanic episode dated at 3.2-2.9 Ma has been identified on the central and southern Ponza, with emplacement of pyroclastic units. At 1.0 Ma, a trachytic episode ended the volcanic activity. The near island of Palmarola exhibits rhyolitic hyaloclastites and domes dated between 1.6 and 1.5 Ma, indicating that the island was entirely built during the Early Pleistocene in a short span of time of ca. 120 ka. Although only 6-8 km apart, the two islands display significantly different geochemical signatures. Ponza rhyolites show major and trace element compositions representative of orogenic magmas of subduction/collision zones: high-K calc-alkaline and metaluminous rhyolites (Agpaitic Index [AI] and Alumina Saturation Index [ASI] 3), and Nb-Ta negative anomalies. In Palmarola, the orogenic character is also present, but much less marked than in Ponza: rhyolites have a peralkaline character (AI>1), lower LILE/HFSE (Th/Ta=11-15), low LREE/HFSE ratios (La/Nb=1-2) close to those of anorogenic lavas, and the Nb-Ta negative anomalies are almost absent. Y/Nb ratios indicate different magmatic sources, one similar to island-arc or active continental margin basalts for Ponza rhyolites, and the others probably involving an OIB type component for Palmarola rhyolites and Ponza trachytes

  16. Microcap M&A: An Exploratory Study

    Directory of Open Access Journals (Sweden)

    Keith Turpie


    Full Text Available A substantial body of accounting and finance literature has been devoted to the study of Mergers and Acquisitions (M&As dominated by discussions relating to the gains and losses that accrue from transactions involving large public companies. This paper makes a unique contribution to the literature by investigating the M&A experience of microcap businesses. Transactions involving microcap M&A are substantially different to those involving large companies on a number of dimensions. This paper explores the determinants of microcap M&A success and pitfalls and problems from an integration perspective. Due to the paucity of research in the area an exploratory research design is employed, conducting interviews with five CEOs of companies that had each managed multiple transactions. We find microcap M&As are successful when measured against identified goals but generally take longer and cost more than expected. Further, culture and communication are key issues in determining success/failure. We also find the in-house management of integration aspects is problematic for these businesses and suggest this warrants further study.

  17. Development of a risk assessment tool for volcanic urban environments: RiskScape and the Auckland Volcanic Field, New Zealand (United States)

    Deligne, N. I.; Leonard, G.; King, A.; Wilson, G.; Wilson, T.; Lindsay, J. M.


    Auckland city, home to a third of New Zealand's population, is situated on top of the Auckland Volcanic Field (AVF), which last erupted roughly 500 years ago. Since 2008, the Determining Volcanic Risk in Auckland (DEVORA) program has investigated the geologic context of the AVF, improved timing constraints of past eruptions, explored possible tempo-spatial-volume eruption trends, and identified likely styles and hazards of future eruptions. DEVORA is now moving into development of risk and societal models for Auckland. The volcanic module of RiskScape, a multi-hazard risk assessment tool developed by Crown Research Institutes GNS Science and NIWA, will be expanded and used to model risk and impact to the built environment and population caused by a future AVF eruption. RiskScape models casualties, damage and disruption caused by various hazards, the resulting reduced functionality of assets, and associated clean up costs. A strength of RiskScape is that the effect of various mitigation strategies can be explored by strengthening asset attributes and examining resulting changes in the output risk evaluation. We present our framework for building a volcano hazard exposure module for RiskScape along with our approach for assessing asset vulnerability through the development of fragility functions. We also present the framework for engagement with regional Auckland stakeholders, including representatives of local and regional governments and utility companies, to identify complementary needs to ensure that final risk products are relevant and useable by end users.

  18. Volcanic Plume Measurements with UAV (Invited) (United States)

    Shinohara, H.; Kaneko, T.; Ohminato, T.


    Volatiles in magmas are the driving force of volcanic eruptions and quantification of volcanic gas flux and composition is important for the volcano monitoring. Recently we developed a portable gas sensor system (Multi-GAS) to quantify the volcanic gas composition by measuring volcanic plumes and obtained volcanic gas compositions of actively degassing volcanoes. As the Multi-GAS measures variation of volcanic gas component concentrations in the pumped air (volcanic plume), we need to bring the apparatus into the volcanic plume. Commonly the observer brings the apparatus to the summit crater by himself but such measurements are not possible under conditions of high risk of volcanic eruption or difficulty to approach the summit due to topography etc. In order to overcome these difficulties, volcanic plume measurements were performed by using manned and unmanned aerial vehicles. The volcanic plume measurements by manned aerial vehicles, however, are also not possible under high risk of eruption. The strict regulation against the modification of the aircraft, such as installing sampling pipes, also causes difficulty due to the high cost. Application of the UAVs for the volcanic plume measurements has a big advantage to avoid these problems. The Multi-GAS consists of IR-CO2 and H2O gas analyzer, SO2-H2O chemical sensors and H2 semiconductor sensor and the total weight ranges 3-6 kg including batteries. The necessary conditions of the UAV for the volcanic plumes measurements with the Multi-GAS are the payloads larger than 3 kg, maximum altitude larger than the plume height and installation of the sampling pipe without contamination of the exhaust gases, as the exhaust gases contain high concentrations of H2, SO2 and CO2. Up to now, three different types of UAVs were applied for the measurements; Kite-plane (Sky Remote) at Miyakejima operated by JMA, Unmanned airplane (Air Photo Service) at Shinomoedake, Kirishima volcano, and Unmanned helicopter (Yamaha) at Sakurajima

  19. K-Ar Geochronology and isotopic composition of the late oligocene- early miocene Ancud volcanic complex, Chiloe

    International Nuclear Information System (INIS)

    Munoz B, Jorge; Duhart O, Paul; Farmer, G. Lang; Stern, Charles R


    The Ancud Volcanic Complex (Gally and Sanchez , 1960) forms a portion of the Mid-Tertiary Coastal Magmatic Belt which outcrops in the area of northern Chiloe island. Main exposures occur at Ancud, Punta Polocue, Punihuil, Pumillahue, Tetas de Teguaco and Bahia Cocotue. The Ancud Volcanic Complex consists of basaltic to basaltic andesites lava flows and volcanic necks and rhyolitic pyroclastic flows and vitric domes. Previous studies indicate a Late Oligocene-Early Miocene age (Garcia et al., 1988; Stern and Vergara, 1992; Munoz et al., 2000). The Ancud Volcanic Complex covers and intrudes Palaeozoic-Triassic metamorphic rocks and is partially covered by an early to middle Miocene marine sedimentary sequence known as Lacui Formation (Valenzuela, 1982) and by Pleistocene glacial deposits (Heusser, 1990). At Punihuil locality, lava flows are interbedded with the lower part of the marine sedimentary sequence, which includes significant amounts of redeposited pyroclastic components. Locally, the presence of hyaloclastic breccias suggests interaction of magma with marine water (au)

  20. Examining spectral variations in localized lunar dark mantle deposits (United States)

    Jawin, Erica; Besse, Sebastien; Gaddis, Lisa R.; Sunshine, Jessica; Head, James W.; Mazrouei, Sara


    The localized lunar dark mantle deposits (DMDs) in Alphonsus, J. Herschel, and Oppenheimer craters were analyzed using visible-near-infrared spectroscopy data from the Moon Mineralogy Mapper. Spectra of these localized DMDs were analyzed for compositional and mineralogical variations within the deposits and were compared with nearby mare basalt units. Spectra of the three localized DMDs exhibited mafic absorption features indicating iron-rich compositions, although the DMDs were spectrally distinct from nearby mare basalts. All of the DMDs contained spectral signatures of glassy materials, suggesting the presence of volcanic glass in varying concentrations across the individual deposits. In addition, the albedo and spectral signatures were variable within the Alphonsus and Oppenheimer crater DMDs, suggesting variable deposit thickness and/or variations in the amount of mixing with the local substrate. Two previously unidentified localized DMDs were discovered to the northeast of Oppenheimer crater. The identification of high concentrations of volcanic glass in multiple localized DMDs in different locations suggests that the distribution of volcanic glass across the lunar surface is much more widespread than has been previously documented. The presence of volcanic glass implies an explosive, vulcanian eruption style for localized DMDs, as this allows volcanic glass to rapidly quench, inhibiting crystallization, compared to the larger hawaiian-style eruptions typical of regional DMD emplacement where black beads indicate a higher degree of crystallization. Improved understanding of the local and global distributions of volcanic glass in lunar DMDs will further constrain lunar degassing and compositional evolution throughout lunar volcanic history.

  1. Monitoring Persistent Volcanic Emissions from Sulphur Springs, Saint Lucia: A Community Approach to Disaster Risk Reduction (United States)

    Joseph, E. P.; Beckles, D. M.; Cox, L.; Jackson, V. B.; Alexander, D.


    Volcanic and geothermal emissions are known natural sources of volatiles to the atmosphere. Volcanogenic air pollutants known to cause the most serious impact are carbon dioxide (CO2), sulphur dioxide (SO2), hydrogen chloride (HCl) and hydrogen fluoride (HF). Some studies into the potential for volcanic emissions to produce chronic diseases in humans indicate that areas of major concern include respiratory problems, particularly silicosis (Allen et al. 2000; Baxter et al. 1999; Buist et al. 1986), psychological stress (Shore et al. 1986), and chemical impacts of gas or ash (Giammanco et al. 1998). Sulphur Springs Park in Saint Lucia has a very high recreational value with >200,000 visitors annually, while the nearby town of Soufrière has >8,400 residents. Residents and visitors have raised concerns about the volcanic emissions and its health effects. As part of the volcanic surveillance programme undertaken by the UWI, Seismic Research Centre (SRC) in Saint Lucia, a new monitoring network has been established for quantifying the ambient SO2 in air, to which staff and visitors at the volcanic park are exposed to. The implementation and continued operation of this network has involved the training of local personnel in the active field sampling and analytical techniques required for the assessment of ambient SO2 concentrations, using a low cost monitor as well as commercial passive samplers. This approach recognizes that environmental hazards are a usual part of life and productive livelihoods, and to minimize post-disaster response and recovery it is beneficial to promote preparedness and mitigation, which is best achieved at the local level with community involvement. It is also intended that the volcanic emissions monitoring network could be used as a method to establish and maintain community-based initiatives that would also be helpful when volcanic threat manifests.

  2. The timing and origin of pre- and post-caldera volcanism associated with the Mesa Falls Tuff, Yellowstone Plateau volcanic field (United States)

    Stelten, Mark E.; Champion, Duane E.; Kuntz, Mel A.


    We present new sanidine 40Ar/39Ar ages and paleomagnetic data for pre- and post-caldera rhyolites from the second volcanic cycle of the Yellowstone Plateau volcanic field, which culminated in the caldera-forming eruption of the Mesa Falls Tuff at ca. 1.3 Ma. These data allow for a detailed reconstruction of the eruptive history of the second volcanic cycle and provide new insights into the petrogenesis of rhyolite domes and flows erupted during this time period. 40Ar/39Ar age data for the biotite-bearing Bishop Mountain flow demonstrate that it erupted approximately 150 kyr prior to the Mesa Falls Tuff. Integrating 40Ar/39Ar ages and paleomagnetic data for the post-caldera Island Park rhyolite domes suggests that these five crystal-rich rhyolites erupted over a centuries-long time interval at 1.2905 ± 0.0020 Ma (2σ). The biotite-bearing Moonshine Mountain rhyolite dome was originally thought to be the downfaulted vent dome for the pre-caldera Bishop Mountain flow due to their similar petrographic and oxygen isotope characteristics, but new 40Ar/39Ar dating suggest that it erupted near contemporaneously with the Island Park rhyolite domes at 1.2931 ± 0.0018 Ma (2σ) and is a post-caldera eruption. Despite their similar eruption ages, the Island Park rhyolite domes and the Moonshine Mountain dome are chemically and petrographically distinct and are not derived from the same source. Integrating these new data with field relations and existing geochemical data, we present a petrogenetic model for the formation of the post-Mesa Falls Tuff rhyolites. Renewed influx of basaltic and/or silicic recharge magma into the crust at 1.2905 ± 0.0020 Ma led to [1] the formation of the Island Park rhyolite domes from the source region that earlier produced the Mesa Falls Tuff and [2] the formation of Moonshine Mountain dome from the source region that earlier produced the biotite-bearing Bishop Mountain flow. These magmas were stored in the crust for less than a few thousand

  3. A Proposed Community Network For Monitoring Volcanic Emissions In Saint Lucia, Lesser Antilles (United States)

    Joseph, E. P.; Beckles, D. M.; Robertson, R. E.; Latchman, J. L.; Edwards, S.


    Systematic geochemical monitoring of volcanic systems in the English-speaking islands of the Lesser Antilles was initiated by the UWI Seismic Research Centre (SRC) in 2000, as part of its volcanic surveillance programme for the English-speaking islands of the Lesser Antilles. This programme provided the first time-series observations used for the purpose of volcano monitoring in Dominica and Saint Lucia, permitted the characterization of the geothermal fluids associated with them, and established baseline studies for understanding of the hydrothermal systems during periods of quiescence (Joseph et al., 2011; Joseph et al., 2013). As part of efforts to improve and expand the capacity of SRC to provide volcanic surveillance through its geothermal monitoring programme, it is necessary to develop economically sustainable options for the monitoring of volcanic emissions/pollutants. Towards this effort we intend to work in collaboration with local authorities in Saint Lucia, to develop a monitoring network for quantifying the background exposure levels of ambient concentrations of volcanic pollutants, SO2 in air and As in waters (as health significant marker elements in the geothermal emissions) that would serve as a model for the emissions monitoring network for other volcanic islands. This programme would facilitate the building of local capacity and training to monitor the hazardous exposure, through the application and transfer of a regionally available low-cost and low-technology SO2 measurement/detection system in Saint Lucia. Existing monitoring technologies to inform evidence based health practices are too costly for small island Caribbean states, and no government policies or health services measures currently exist to address/mitigate these influences. Gases, aerosols and toxic elements from eruptive and non-eruptive volcanic activity are known to adversely affect human health and the environment (Baxter, 2000; Zhang et al., 2008). Investigations into the

  4. The change of magma chamber depth in and around the Baekdu Volcanic area from late Cenozoic (United States)

    Lee, S. H.; Oh, C. W.; Lee, Y. S.; Lee, S. G.; Liu, J.


    The Baekdu Volcano is a 2750m high stratovolcanic cone resting on a basaltic shield and plateau and locates on the North Korea-China border. Its volcanic history can be divided into four stages (from the oldest to the youngest): (i) preshield plateau-forming eruptions, (ii) basalt shield formation, (iii) construction of a trachytic composite cone, and (iv) explosive ignimbrite forming eruptions. In the First stage, a fissure eruption produced basalts from the Oligocene to the Miocene (28-13 Ma) forming preshield plateau. Fissure and central eruptions occurred together during the shield-forming eruptions (4.21-1.70 Ma). In the third stage, the trachytic composite volcano formed during the Pleistocene (0.61-0.09 Ma). In this stage, magma changed to an acidic melt. The latest stage has been characterized by explosive ignimbrite-forming eruptions during the Holocene. The composite volcanic part consists of the Xiaobaishan, Lower, Middle and Upper Trachytes with rhyolites. The whole rock and clinopyroxene in basalts, trachytic and rhyolite, are analyzed to study the depth of magma chambers under the Baekdu Volcano. From the rhyolite, 9.8-12.7kbar is obtained for the depth of magma chamber. 3.7-4.1, 8.9-10.5 and 8.7 kbar are obtained from the middle, lower and Xiaobaishan trachytes. From the first and second stage basalts, 16.9-17.0 kbar and 14-14.4kbar are obtained respectively. The first stage basalt give extrusive age of 11.98 Ma whereas 1.12 and 1.09 Ma are obtained from the feldspar and groundmass in the second stage basalt. The Xiaobaishan trachyte and rhyolite give 0.25 and 0.21 Ma whereas the Middle trachyte gives 0.07-0.06 Ma. These data indicate that the magma chambers of the first and second stage basalts were located in the mantle and the magma chamber for the second stage basalt may have been underplated below continental crust. The Xiaobisan trachyte and rhyolite originated from the magma chamber in the depth of ca. 30-40 km and the Middle trachyte

  5. Volcanic Ash Advisory Database, 1983-2003 (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Volcanic ash is a significant hazard to aviation and can also affect global climate patterns. To ensure safe navigation and monitor possible climatic impact, the...

  6. Age of the Auckland Volcanic Field

    International Nuclear Information System (INIS)

    Lindsay, J.; Leonard, G.S.


    In 2008 a multi-disciplinary research programme was launched, a GNS Science-University of Auckland collaboration with the aim of DEtermining VOlcanic Risk in Auckland (DEVORA). A major aspiration of DEVORA is development of a probabilistic hazard model for the Auckland Volcanic Field (AVF). This will be achieved by investigating past eruption magnitude-frequency relationships and comparing these with similar data from analogous volcanic fields. A key data set underpinning this is an age database for the AVF. To this end a comprehensive dating campaign is planned as part of DEVORA. This report, Age of the Auckland Volcanic Field, is a synthesis of all currently available age data for the AVF. It represents one of several reports carried out as part of the 'synthesis' phase of DEVORA, whereby existing data from all previous work is collated and summarised, so that gaps in current knowledge can be identified and addressed. (author). 60 refs., 7 figs., 31 tabs.

  7. Volcanic eruptions are cooling the earth

    International Nuclear Information System (INIS)

    Groenaas, Sigbjoern


    The article discusses how volcanic eruptions may influence the climate. The environmental impacts both on the earth surface and the atmosphere are surveyed. Some major eruptions in modern times are mentioned

  8. Stochastic Modeling of Past Volcanic Crises (United States)

    Woo, Gordon


    The statistical foundation of disaster risk analysis is past experience. From a scientific perspective, history is just one realization of what might have happened, given the randomness and chaotic dynamics of Nature. Stochastic analysis of the past is an exploratory exercise in counterfactual history, considering alternative possible scenarios. In particular, the dynamic perturbations that might have transitioned a volcano from an unrest to an eruptive state need to be considered. The stochastic modeling of past volcanic crises leads to estimates of eruption probability that can illuminate historical volcanic crisis decisions. It can also inform future economic risk management decisions in regions where there has been some volcanic unrest, but no actual eruption for at least hundreds of years. Furthermore, the availability of a library of past eruption probabilities would provide benchmark support for estimates of eruption probability in future volcanic crises.

  9. Mercury enrichment indicates volcanic triggering of the Valanginian environmental change (United States)

    Charbonnier, Guillaume; Morales, Chloé; Duchamp-Alphonse, Stéphanie; Westermann, Stéphane; Adatte, Thierry; Föllmi, Karl


    The Valanginian stage (Early Cretaceous, ˜137-132 Ma) recorded an episode of pronounced palaeoenvironmental change, which is marked by a globally recorded positive δ13C excursion of 1.5 to 2‰ amplitude, also known as the "Weissert event or episode". Its onset near the early/late Valanginian boundary (B. campylotoxus-S. verrucosum ammonite Zones) coincides with a phase of warmer climate conditions associated with enhanced humidity, major changes in the evolution of marine plankton, and the drowning of tropical and subtropical marine shallow-water carbonate ecosystems. The globally recorded excursion indicates important transformations in the carbon cycle, which have tentatively been associated with Paraná-Etendeka large igneous province (LIP) volcanic activity. Incertainties in existing age models preclude, however, its positive identification as a trigger of Valanginian environmental change. Since very recently, mercury (Hg) chemostratigraphy offers the possibly to evaluate the role of LIP activity during major palaeoenvironmental perturbations. In this study we investigate the distribution of Hg contents in four Valanginian reference sections located in pelagic and hemipelagic environments in the Central Tethyan Realm (Lombardian Basin, Breggia section), the northern Tethyan margin (Vocontian Basin, Orpierre and Angles sections), and the narrow seaway connecting the Tethyan and Boreal Oceans (Polish Basin, Wawal core). All records show an enrichment in Hg concentrations at or near the onset of the Weissert Episode, with maximal values of 70.5 ppb at Angles, 59.5 ppb at Orpierre, 69.9 ppb at Wawal, and 17.0 ppb at Breggia. The persistence of the Hg anomaly in Hg/TOC and Hg/phyllosilicate ratios shows that organic-matter scavenging and/or adsorbtion onto clay minerals only played a limited role.We propose that volcanic outgassing was the primary source of the Hg enrichment and conclude that an important magmatic pulse triggered the Valanginian environmental

  10. U-Pb zircon geochronology of Late Devonian to Early Carboniferous extension-related silicic volcanism in the northern New England Fold Belt

    International Nuclear Information System (INIS)

    Bryan, S.E.; Holcombe, R.J.; Fielding, C.R.; Allen, C.M.


    Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) analysis of zircons confirm a Late Devonian to Early Carboniferous age (ca 360-350 Ma) for silicic volcanic rocks of the Campwyn Volcanics and Yarrol terrane of the northern New England Fold Belt (Queensland). These rocks are coeval with silicic volcanism recorded elsewhere in the fold belt at this time (Connors Arch, Drummond Basin). The new U-Pb zircon ages, in combination with those from previous studies, show that silicic magmatism was both widespread across the northern New England Fold Belt (>250 000 km 2 and >500 km inboard of plate margin) and protracted, occurring over a period of -15 million years. Zircon inheritance is commonplace in the Late Devonian - Early Carboniferous volcanics, reflecting anatectic melting and considerable reworking of continental crust. Inherited zircon components range from ca 370 to ca 2050 Ma, with Middle Devonian (385-370 Ma) zircons being common to almost all dated units. Precambrian zircon components record either Precambrian crystalline crust or sedimentary accumulations that were present above or within the zone of magma formation This contrasts with a lack of significant zircon inheritance in younger Permo-Carboniferous igneous rocks intruded through,and emplaced on top of, the Devonian-Carboniferous successions. The inheritance data and location of these volcanic rocks at the eastern margins of the northern New England Fold Belt, coupled with Sr-Nd, Pb isotopic data and depleted mantle model ages for Late Palaeozoic and Mesozoic magmatism, imply that Precambrian mafic and felsic crustal materials (potentially as old as 2050 Ma), or at the very least Lower Palaeozoic rocks derived from the reworking of Precambrian rocks, comprise basement to the eastern parts of the fold belt. This crustal basement architecture may be a relict from the Late Proterozoic breakup of the Rodinian supercontinent. Copyright (2004) Geological Society of Australia

  11. Imaging volcanic CO2 and SO2 (United States)

    Gabrieli, A.; Wright, R.; Lucey, P. G.; Porter, J. N.


    Detecting and quantifying volcanic carbon dioxide (CO2) and sulfur dioxide (SO2) emissions is of relevance to volcanologists. Changes in the amount and composition of gases that volcanoes emit are related to subsurface magma movements and the probability of eruptions. Volcanic gases and related acidic aerosols are also an important atmospheric pollution source that create environmental health hazards for people, animals, plants, and infrastructures. For these reasons, it is important to measure emissions from volcanic plumes during both day and night. We present image measurements of the volcanic plume at Kīlauea volcano, HI, and flux derivation, using a newly developed 8-14 um hyperspectral imaging spectrometer, the Thermal Hyperspectral Imager (THI). THI is capable of acquiring images of the scene it views from which spectra can be derived from each pixel. Each spectrum contains 50 wavelength samples between 8 and 14 um where CO2 and SO2 volcanic gases have diagnostic absorption/emission features respectively at 8.6 and 14 um. Plume radiance measurements were carried out both during the day and the night by using both the lava lake in the Halema'uma'u crater as a hot source and the sky as a cold background to detect respectively the spectral signatures of volcanic CO2 and SO2 gases. CO2 and SO2 path-concentrations were then obtained from the spectral radiance measurements using a new Partial Least Squares Regression (PLSR)-based inversion algorithm, which was developed as part of this project. Volcanic emission fluxes were determined by combining the path measurements with wind observations, derived directly from the images. Several hours long time-series of volcanic emission fluxes will be presented and the SO2 conversion rates into aerosols will be discussed. The new imaging and inversion technique, discussed here, are novel allowing for continuous CO2 and SO2 plume mapping during both day and night.

  12. 5 Ma of plume source evolution in the Niihau - Kauai - North Arch magmas, Hawaii (United States)

    Beguelin, P.; Bizimis, M.; McIntosh, E. C.; Cousens, B.; Clague, D. A.


    The Hawaiian islands of Kauai, Niihau and Kaula form a 200 km wide platform across the plume track and record the longest activity record of Hawaiian volcanism ( > 5Ma) [1]. We present new Hf and high precision Pb (MC-ICP-MS with Tl addition) isotope data on 56 previously characterized [2] shield, post-shield and rejuvenated stage lavas from Kauai and Niihau, and on rejuvenated lavas from the North Arch volcanic field, 250 km NE of Kauai. These samples cover nearly the full eruptive history of Kauai and Niihau, and complete an across-plume transect of rejuvenated volcanism, along with published Kaula values [3]. In Nd-Hf-Sr-Pb isotope spaces [2], shield and post-shield lavas from Kauai and Niihau partially overlap the Koolau shield lavas (KSDP, Oahu [4]). Rejuvenated lavas from Kauai and Niihau show a 3 ɛNd units variability and overlap North Arch at a common depleted composition at ɛNd 9 and ɛHf 14. Kauai rejuvenated lavas in part overlap shield and post-shield lavas in Nd-Hf, but extend to lower ɛHf values for a given 87Sr/86Sr and ɛNd. In contrast Niihau rejuvenated lavas have higher ɛHf for a given ɛNd and 87Sr/86Sr compared to all Hawaiian shield lavas. The Niihau data cannot be explained by contribution of a proximal shield stage plume source (e.g. Niihau or Kauai). Instead it is consistent with mixing between a depleted mantle source and an enriched component with high Nd/Hf, Sr/Hf ratios, akin to a carbonatite with low ɛHf and ɛNd, and with their trace element systematics [5] . ICP-MS Pb isotope data for rejuvenated lavas from Kaula, Niihau, Kauai, and North Arch form three distinct arrays, confirming heterogeneity in the rejuvenated source. Our data is consistent with the presence of an enriched, Koolau-like component in the source of shield, post-shield and rejuvenated volcanism in Kauai and Niihau. The rejuvenated sources are heterogeneous across the plume, with the most isotopically depleted values seen in the distal North Arch volcanic field

  13. Lava and Life: New investigations into the Carson Volcanics, lower Kimberley Basin, north Western Australia (United States)

    Orth, Karin; Phillips, Chris; Hollis, Julie


    The Carson Volcanics are the only volcanic unit in the Paleoproterozoic Kimberley Basin and are part of a poorly studied Large Igneous Province (LIP) that was active at 1790 Ma. New work focussing on this LIP in 2012 and 2013 involved helicopter-supported traverses and sampling of the Carson Volcanics in remote areas near Kalumburu in far north Western Australia's Kimberley region. The succession is widespread and flat lying to gently dipping. It consists of three to six basalt units with intercalated sandstone and siltstone. The basalts are 20-40 m thick, but can be traced up to 60 km along strike. The basalt can be massive or amygdaloidal and commonly display polygonal to subhorizontal and rare vertical columnar jointing. Features of the basalt include ropy lava tops and basal pipe vesicles consistent with pahoehoe lavas. The intercalated cross-bedded quartzofeldspathic sandstone and siltstone vary in thickness up to 40 m and can be traced up to 40 km along strike. Peperite is common and indicates interaction between wet, unconsolidated sediment and hot lava. Stromatolitic chert at the top of the formation represents the oldest life found within the Kimberley region. Mud cracks evident in the sedimentary rocks, and stromatolites suggest an emergent broad tidal flat environment. The volcanics were extruded onto a wide marginal margin setting subject to frequent flooding events. Thickening of the volcanic succession south and the palaeocurrents in the underlying King Leopold Sandstone and the overlying Warton Sandstone suggest that this shelf sloped to the south. The type of basalt and the basalt morphology indicate a low slope gradient of about 1°.

  14. Paleomagnetic results from Tertiary volcanic strata and intrusions, Absaroka Volcanic Supergroup, Yellowstone National Park and vicinity: Contributions to the North American apparent polar wander path (United States)

    Harlan, S.S.; Morgan, L.A.


    We report paleomagnetic and rock magnetic data from volcanic, volcaniclastic, and intrusive rocks of the 55-44Ma Absaroka Volcanic Supergroup (AVS) exposed along the northeastern margin of Yellowstone National Park and adjacent areas. Demagnetization behavior and rock magnetic experiments indicate that the remanence in most samples is carried by low-Ti titanomagnetite, although high-coercivity phases are present in oxidized basalt flows. Paleomagnetic demagnetization and rock magnetic characteristics, the presence of normal and reverse polarity sites, consistency with previous results, and positive conglomerate tests suggest that the observed remanences are primary thermoremanent magnetizations of Eocene age (c. 50Ma). An in situ grand-mean for 22 individual site- or cooling-unit means from this study that yield acceptable data combined with published data from Independence volcano yields a declination of 347.6?? and inclination of 59.2?? (k=21.8, ??95=6.8??) and a positive reversal test. Averaging 21 virtual geomagnetic poles (VGPs) that are well-grouped yields a mean at 137.1??E, 82.5??N (K=17.6, A95=7.8??), similar to results previously obtained from published studies from the AVS. Combining the VGPs from our study with published data yields a combined AVS pole at 146.3??E, 83.1??N (K=13.5, A95=6.2??, N=42 VGPs). Both poles are indistinguishable from c. 50Ma cratonic and synthetic reference poles for North America, and demonstrate the relative stability of this part of the Cordillera with respect to the craton. ?? 2009 Elsevier B.V.

  15. Source and Extent of Volcanic Ashes at the Permian-Triassic Boundary in South China and Its implications (United States)

    Wang, M.; Zhong, Y. T.; Hou, Y. L.; He, B.


    Highly correlated with the Permian-Triassic Boundary (PTB) Mass Extinction in stratigraphic section, volcanic ashes around the P-T Boundary in South China have been suggested to be a likely cause of the PTB Mass Extinction. So the nature, source and extent of these volcanic ashes have great significance in figuring out the cause of the PTB Mass Extinction. In this study, we attempt to constrain the source and extent of the PTB volcanic ashes in South China by studying pyroclastic sedimentary rocks and the spatial distribution of tuffs and ashes in South China. The detrital zircons of tuffaceous sandstones from Penglaitan section yield an age spectrum peaked at 252Ma, with ɛHf(t) values varying from -20 to -5 ,and have Nb/Hf, Th/Nb and Hf/Th ratios similar to those from arc/orogenic-related settings. Coarse tuffaceous sandstones imply that their source is in limited distance. Those pyroclastic sedimentary rocks in Penglaitan are well correlated with the PTB volcanic ashes in Meishan GSSP section in stratigraphy. In the spatial distribution, pyroclastic sedimentary rocks and tuffs distribute only in southwest of South China, while finer volcanic ashes are mainly in the northern part. This spatial distribution suggests the source of tuffs and ashes was to the south or southwest of South China. Former studies especially that of Permian-Triassic magmatism in Hainan Island have supported the existence of a continental arc related to the subduction and closure of Palaeo-Tethys on the southwestern margin of South China during Permian to early Triassic. It is suggested that the PTB ashes possibly derived from this Paleo-Tethys continental arc. The fact that volcanic ashes haven't been reported or found in PTB stratum in North China or Northwest China implies a limited extent of the volcanism, which thus is too small to cause the PTB mass extinction.

  16. SCHeMA open and modular in situ sensing solution (United States)

    Tercier-Waeber, Marie Louise; Novellino, Antonio


    Marine environments are highly vulnerable and influenced by a wide diversity of anthropogenic and natural substances and organisms that may have adverse effects on the ecosystem equilibrium, on living resources and, ultimately, on human health. Identification of relevant types of hazards at the appropriate temporal and spatial scale is crucial to detect their sources and origin, to understand the processes governing their magnitude and distribution, and to ultimately evaluate and manage their risks and consequences preventing economic losses. This can be addressed only by the development of innovative, compact, rugged, automated, sensor networks allowing long-term monitoring. Development of such tools is a challenging task as it requires many analytical and technical innovations. The FP7-OCEAN 2013-SCHeMA project aims to contribute to meet this challenge by providing an open and modular sensing solution for autonomous in situ high resolution mapping of a range of anthropogenic and natural chemical compounds (trace metals, nutrients, anthropogenic organic compounds, toxic algae species and toxins, species relevant to the carbon cycle). To achieve this, SCHeMA activities focus on the development of : 1) an array of miniature sensor probes taking advantage of various innovative solutions, namely: (polymer-based) gel-integrated sensors; solid state ion-selective membrane sensors coupled to an on-line desalination module; mid-infrared optical sensors; optochemical multichannel devices; enOcean technology; 2) dedicated hardware, firmware and software components allowing their plug-and-play integration, localization as well as wireless bidirectional communication via advanced OGC-SWE wired/wireless dedicated interfaces; 3) a web-based front-end system compatible with EU standard requirements and principles (INSPIRE, GEO/GEOSS) and configured to insure easy interoperability with national, regional and local marine observation systems. This lecture will present examples of

  17. Maïs beperkt nitraatverlies van gras

    NARCIS (Netherlands)

    Verloop, J.; Boumans, L.


    Maïs staat bekend als een gewas dat veel nitraat naar het grondwater lekt. Maar maïs heeft ook goeie kanten. Nieuw in dit rijtje is dat maïs, in vruchtwisseling met gras, ook het nitraatverlies van grasland beperkt. Dit blijkt uit de metingen van het RIVM op De Marke.

  18. A "embolada" em Macunaíma

    Directory of Open Access Journals (Sweden)

    Raimunda B. Batista


    Full Text Available Os intelectuais do modernismo brasileiro tiveram como preocupação a redefinição da cultura brasileira tomando como ponto de partida a cultura popular e o folclore brasileiros. Em Macunaíma, Mário de Andrade aproveita os mais variados elementos da cultura popular, dando-lhes uma configuração erudita. Entre esses elementos destacamos o aproveitamento da embolada que, enquanto modo de cantar, possui uma forte estrutura poética, podendo ser aproveitada na prosa de ficção, conservando o seu ritmo e forma.

  19. Lithology and temperature: How key mantle variables control rift volcanism (United States)

    Shorttle, O.; Hoggard, M.; Matthews, S.; Maclennan, J.


    Continental rifting is often associated with extensive magmatic activity, emplacing millions of cubic kilometres of basalt and triggering environmental change. The lasting geological record of this volcanic catastrophism are the large igneous provinces found at the margins of many continents and abrupt extinctions in the fossil record, most strikingly that found at the Permo-Triassic boundary. Rather than being considered purely a passive plate tectonic phenomenon, these episodes are frequently explained by the involvement of mantle plumes, upwellings of mantle rock made buoyant by their high temperatures. However, there has been debate over the relative role of the mantle's temperature and composition in generating the large volumes of magma involved in rift and intra-plate volcanism, and even when the mantle is inferred to be hot, this has been variously attributed to mantle plumes or continental insulation effects. To help resolve these uncertainties we have combined geochemical, geophysical and modelling results in a two stage approach: Firstly, we have investigated how mantle composition and temperature contribute to melting beneath Iceland, the present day manifestation of the mantle plume implicated in the 54Ma break up of the North Atlantic. By considering both the igneous crustal production on Iceland and the chemistry of its basalts we have been able to place stringent constraints on the viable temperature and lithology of the Icelandic mantle. Although a >100°C excess temperature is required to generate Iceland's thick igneous crust, geochemistry also indicates that pyroxenite comprises 10% of its source. Therefore, the dynamics of rifting on Iceland are modulated both by thermal and compositional mantle anomalies. Secondly, we have performed a global assessment of the mantle's post break-up thermal history to determine the amplitude and longevity of continental insulation in driving excess volcanism. Using seismically constrained igneous crustal

  20. The Origin of Widespread Long-lived Volcanism Across the Galapagos Volcanic Province (United States)

    O'Connor, J. M.; Stoffers, P.; Wijbrans, J. R.; Worthington, T. J.


    40Ar/39Ar ages for rocks dredged (SO144 PAGANINI expedition) and drilled (DSDP) from the Galapagos Volcanic Province (Cocos, Carnegie, Coiba and Malpelo aseismic ridges and associated seamounts) show evidence of 1) increasing age with distance from the Galapagos Archipelago, 2) long-lived episodic volcanism at many locations, and 3) broad overlapping regions of coeval volcanism. The widespread nature of synchronous volcanism across the Galapagos Volcanic Province (GVP) suggests a correspondingly large Galapagos hotspot melting anomaly (O'Connor et al., 2004). Development of the GVP via Cocos and Nazca plate migration and divergence over this broad melting anomaly would explain continued multiple phases of volcanism over millions of years following the initial onset of hotspot volcanism. The question arising from these observations is whether long-lived GVP episodic volcanism is equivalent to `rejuvenescent' or a `post-erosional' phase of volcanism that occurs hundreds of thousands or million years after the main shield-building phase documented on many mid-plate seamount chains, most notably along the Hawaiian-Emperor Seamount Chain? Thus, investigating the process responsible for long-lived episodic GVP volcanism provides the opportunity to evaluate this little understood process of rejuvenation in a physical setting very different to the Hawaiian-Emperor Chain (i.e. on/near spreading axis versus mid-plate). We consider here timing and geochemical information to test the various geodynamic models proposed to explain the origin of GVP hotspot volcanism, especially the possibility of rejuvenated phases that erupt long after initial shield-building.

  1. K-Ar ages, paleomagnetism, and geochemistry of the South Auckland volcanic field, North Island, New Zealand

    International Nuclear Information System (INIS)

    Briggs, R.M.; Okada, T.; Itaya, T.; Shibuya, H.; Smith, I.E.M.


    The South Auckland volcanic field is one of the Pliocene-Quaternary intraplate basaltic fields in northern North Island. It consists of at least 97 monogenetic volcanic centres covering an area of c. 300 km 2 , 38 km south of Auckland. Fifty-nine of the volcanic centres are characterised by mainly magmatic or effusive activity that constructed scoria cones and lava flows, while 38 are mainly phreatomagmatic or explosive that produced tuff rings and maars. Rock types consist of basanites, hawaiites, nepheline hawaiites, transitional basalts, and ol-tholeiitic basalts, with relatively minor amounts of nephelinites, alkali basalts, Q-tholeiitic basalts, and nepheline mugearites. Forty-three new K-Ar ages are presented, which range from 0.51 to 1.59 Ma, and show two peaks of activity at 0.6 and 1.3 Ma. Paleomagnetic determinations at 26 selected sites agree well with the paleomagnetic reversal time scale and support the K-Ar age data. Age data from each of the volcanic fields of Okete, Ngatutura, South Auckland, and Auckland, which constitute the Auckland intraplate basaltic province, show that they have developed within a time span of 0.3-1.1 Ma. After activity ceased in any particular field, a new field then developed 35-38 km to the north. These consistent time/space patterns indicate the possibility of a mantle source migrating northwards at c. 5 cm/yr. There is no correlation of rock composition with time, which is consistent with observations in the Northland intraplate province, but is not consistent with the formerly invoked rising diapir model. (author). 30 refs., 8 figs., 3 tabs

  2. Paleomagnetism of the Neoproterozoic Mount Harper Volcanic Complex, Canada (United States)

    Eyster, A. E.; Macdonald, F. A.; O'Connell, R. J.


    Paleomagnetism can be used to identify apparent polar wander, which involves contributions from plate tectonics and true polar wander. True polar wander events have been suggested to have played an important role throughout Earth's history. The Neoproterozoic Mount Harper Volcanic Complex (MHVC) provides paleomagnetic data that bears on this issue. The MHVC is located in the southern Ogilvie Mountains in the Yukon Territory, on the north-west corner of the Laurentian craton. The MHVC involves up to 1200 m of basaltic and andesitic flows. The MHVC reflects the propagating rifting event involved in the breakup of the supercontinent Rodinia. The MHVC is well dated with an age of 717.43± 0.14Ma from the top (Macdonald et al., Science, 2010). Below the MHVC are alluvial fan conglomerate and sandstone from Proterozoic normal faulting. Above the MHVC is a glacial diamictite dated to 716.47± 0.24 Ma and related to Snowball Earth glaciation (Macdonald et al., Science, 2010). Both block and core samples were collected from different members of the MHVC for paleomagnetic study. Included in the sampling were several stratigraphic sections. Alternating field and thermal stepwise demagnetization methods were used to analyze specimens. Magnetic components were determined using principal component analysis and Fisher statistical procedures were used to calculate mean directions. The stratigraphically sampled basalt flows yielded two components. One was a common secondary overprint, and the other was a high stability component which yielded two different directions. One pole is the same as the accepted Neoproterozoic Laurentian grand mean pole and the other is ˜50 degrees away from this grand mean pole. Several possible interpretations are explored- tectonic rotation, true polar wander or the presence of a non-dipolar geomagnetic field.

  3. Molecular and clinical diversity in paraneoplastic immunity to Ma proteins. (United States)

    Rosenfeld, M R; Eichen, J G; Wade, D F; Posner, J B; Dalmau, J


    Antibodies to Ma1 and Ma2 proteins identify a paraneoplastic disorder that affects the limbic system, brain stem, and cerebellum. Preliminary studies suggested the existence of other Ma proteins and different patterns of immune response associated with distinct neurologic symptoms and cancers. In this study, our aim was to isolate the full-length sequence of Ma2 and new family members, identify the major autoantigen of the disorder, and extend the dinical-immunological analysis to 29 patients. Sera from selected patients were used to probe a brainstem cDNA library and isolate the entire Ma2 gene and a new family member, Ma3. Ma3 mRNA is ubiquitously expressed in brain, testis, and several systemic tissues. The variable cellular expression of Ma proteins and analysis of protein motifs suggest that these proteins play roles in the biogenesis of mRNA. Immunoblot studies identify Ma2 as the major autoantigen with unique epitopes recognized by all patients' sera. Eighteen patients had antibodies limited to Ma2: they developed limbic, hypothalamic, and brainstem encephalitis, and 78% had germ-cell tumors of the testis. Eleven patients had antibodies to Ma2 and additional antibodies to Ma1 and/or Ma3; they usually developed additional cerebellar symptoms and more intense brainstem dysfunction, and 82% of these patients had tumors other than germ-cell neoplasms. Overall, 17 of 24 patients (71%) with brain magnetic resonance imaging studies had abnormalities within or outside the temporal lobes, some as contrast-enhancing nodular lesions. A remarkable finding of immunity to Ma proteins is that neurologic symptoms may improve or resolve. This improvement segregated to a group of patients with antibodies limited to Ma2.

  4. Quaternary volcanism, tectonics, and sedimentation in the Idaho National Engineering Laboratory area

    Energy Technology Data Exchange (ETDEWEB)

    Hackett, W.R.; Smith, R.P.


    In this article, we discuss the regional context and describe localities for a two-day field excursion in the vicinity of the Idaho National Engineering Laboratory (INEL). We address several geologic themes: (1) Late Cenozoic, bimodal volcanism of the Eastern Snake River Plain (ESRP), (2) the regional tectonics and structural geology of the Basin and Range province to the northwest of the ESRP, (3) fluvial, lacustrine, and aeolian sedimentation in the INEL area, and (4) the influence of Quaternary volcanism and tectonics on sedimentation near the INEL.

  5. Quaternary volcanism, tectonics, and sedimentation in the Idaho National Engineering Laboratory area

    Energy Technology Data Exchange (ETDEWEB)

    Hackett, W.R.; Smith, R.P.


    In this article, we discuss the regional context and describe localities for a two-day field excursion in the vicinity of the Idaho National Engineering Laboratory (INEL). We address several geologic themes: (1) Late Cenozoic, bimodal volcanism of the Eastern Snake River Plain (ESRP), (2) the regional tectonics and structural geology of the Basin and Range province to the northwest of the ESRP, (3) fluvial, lacustrine, and aeolian sedimentation in the INEL area, and (4) the influence of Quaternary volcanism and tectonics on sedimentation near the INEL.

  6. Ma Ying-jeou’s Presidential Discourse

    Directory of Open Access Journals (Sweden)

    Jonathan Sullivan


    Full Text Available Despite the substantial advances made in cross-Strait relations during Ma Ying-jeou’s (Ma Yingjiu first term, the ROC president’s rhetoric varied considerably as he grappled with the difficult reality of implementing campaign and inauguration pledges to establish better relations with China while striving to maintain national respect and sovereignty. In this article, we put forward a framework for measuring, analysing and explaining this variation in President Ma’s first-term discourse. Analysing a very large number of Ma’s speeches, addresses, etc., we provide empirical assessments of how the content of Ma’s public pronouncements has developed over time, how his rhetoric varies according to the strategic context and timing of a speech, and how his discourse compares to that of his predecessor, Chen Shui-bian (Chen Shuibian. In addressing these questions, the article contributes a quantitative perspective to existing work on political discourse in Taiwan and to the growing methodological and applied literature on how to systematically analyse Chinese political text.

  7. The questa magmatic system: Petrologic, chemical and isotopic variations in cogenetic volcanic and plutonic rocks of the latir volcanic field and associated intrusives, northern New Mexico

    International Nuclear Information System (INIS)

    Johnson, C.M.


    Field, chemical and isotopic data demonstrate that nearly all igneous rocks at Questa resulted from interactions between mantle-derived parental magmas and the crust. Strontium, neodymium and lead isotope ratios of early andesites to rhyolites (28 to 26 Ma) indicate that these magmas assimilated > 25% lower crust. Injection of basaltic magmas extensively modified the strontium and neodymium but not the lead isotope compositions of the lower crust. Eruption of comendite magmas and the peralkaline Amalia Tuff 26 Ma is correlated with inception of regional extension. Lead isotope ratios identify different sources for the metaluminous granites and the peralkaline rocks. 26 Ma metaluminous granite to granodiorite intrusions have chemical and isotopic compositions to those of the precaldera intermediate-composition rocks, and are interpreted as representing the solidified equivalents of the precaldera magmatic episode. However, both conventional and ion-microprobe isotopic data prohibit significant assimilation of crustal rocks at the level of exposure, suggesting that the plutons were emplaced a relatively crystal-rich mushes which did not have sufficient heat to assimilate country rocks. This suggest that in some cases plutonic rocks are better than volcanic rocks in representing the isotopic compositions of their source regions, because the assimilation potential of crystal-rich magmas is significantly less than that of largely liquid magmas

  8. Volcanism on differentiated asteroids (Invited) (United States)

    Wilson, L.


    after passing through optically dense fire fountains. At low eruption rates and high volatile contents many clasts cooled to form spatter or cinder deposits, but at high eruption rates and low volatile contents most clasts landed hot and coalesced into lava ponds to feed lava flows. Lava flow thickness varies with surface slope, acceleration due to gravity, and lava yield strength induced by cooling. Low gravity on asteroids caused flows to be relatively thick which reduced the effects of cooling, and many flows probably attained lengths of tens of km and stopped as a result of cessation of magma supply from the reservoir rather than cooling. On most asteroids larger than 100 km radius experiencing more than ~30% mantle melting, the erupted volcanic deposits will have buried the original chondritic surface layers of the asteroid to such great depths that they were melted, or at least heavily thermally metamorphosed, leaving no present-day meteoritical evidence of their prior existence. Tidal stresses from close encounters between asteroids and proto-planets may have very briefly increased melting and melt migration speeds in asteroid interiors but only gross structural disruption would have greatly have changed volcanic histories.

  9. Rb-Sr geochronology from Barro Alto Complex, Goias: metamorphism evidence of high degree and continental collision around 1300 Ma ago in Central Brazil

    International Nuclear Information System (INIS)

    Fuck, R.A.; Neves, B.B.B.; Cordani, U.G.; Kawashita, K.


    Rb-Sr geochronologic investigation carried out on rocks from the Barro Alto Complex, Goias, yielded iso chronic ages of 1266 +- 17 Ma, for felsic rocks from the granulite belt and 1330 +- 67 Ma, for gneisses belonging to the Juscelandia Sequence. Rb-Sr isotope measurements suggest that Barro Alto rocks have undergone an important metamorphic event during middle Proterozoic times, around 1300 Ma ago. During that event, volcanic and sedimentary rocks of Juscelandia Sequence, as well as the underlying gabbros-anorthosite layered complex, underwent deformation and recrystallization under amphibolite facies conditions. Deformation and metamorphism took place during the collision of two continental blocks, which resulted in a southeastward directed thrust complex, allowing the exposure of granulite slices from the middle-lower crust of the overthrusted block. (author)

  10. Volcanic Supersites as cross-disciplinary laboratories (United States)

    Provenzale, Antonello; Beierkuhnlein, Carl; Giamberini, Mariasilvia; Pennisi, Maddalena; Puglisi, Giuseppe


    Volcanic Supersites, defined in the frame of the GEO-GSNL Initiative, are usually considered mainly for their geohazard and geological characteristics. However, volcanoes are extremely challenging areas from many other points of view, including environmental and climatic properties, ecosystems, hydrology, soil properties and biogeochemical cycling. Possibly, volcanoes are closer to early Earth conditions than most other types of environment. During FP7, EC effectively fostered the implementation of the European volcano Supersites (Mt. Etna, Campi Flegrei/Vesuvius and Iceland) through the MED-SUV and FUTUREVOLC projects. Currently, the large H2020 project ECOPOTENTIAL (2015-2019, 47 partners, contributes to GEO/GEOSS and to the GEO ECO Initiative, and it is devoted to making best use of remote sensing and in situ data to improve future ecosystem benefits, focusing on a network of Protected Areas of international relevance. In ECOPOTENTIAL, remote sensing and in situ data are collected, processed and used for a better understanding of the ecosystem dynamics, analysing and modelling the effects of global changes on ecosystem functions and services, over an array of different ecosystem types, including mountain, marine, coastal, arid and semi-arid ecosystems, and also areas of volcanic origin such as the Canary and La Reunion Islands. Here, we propose to extend the network of the ECOPOTENTIAL project to include active Volcanic Supersites, such as Mount Etna and other volcanic Protected Areas, and we discuss how they can be included in the framework of the ECOPOTENTIAL workflow. A coordinated and cross-disciplinary set of studies at these sites should include geological, biological, ecological, biogeochemical, climatic and biogeographical aspects, as well as their relationship with the antropogenic impact on the environment, and aim at the global analysis of the volcanic Earth Critical Zone - namely, the upper layer of the Earth

  11. The issue of trust and its influence on risk communication during a volcanic crisis (United States)

    Haynes, Katharine; Barclay, Jenni; Pidgeon, Nick


    This paper investigates trust in the scientists, government authorities and wider risk management team during the ongoing volcanic crisis in Montserrat, WI. Identifying the most trusted communicator and how trust in information can be enhanced are considered important for improving the efficacy of volcanic risk communication. Qualitative interviews, participant observations and a quantitative survey were utilised to investigate the views and attitudes of the public, authorities and scientists. Trust was found to be dynamic, influenced by political factors made more complex by the colonial nature of Montserrat’s governance and the changing level of volcanic activity. The scientists were viewed by the authorities as a highly trusted expert source of volcanic information. Mistrust among some of the local authorities towards the scientists and British Governor was founded in the uncertainty of the volcanic situation and influenced by differences in levels of acceptable risk and suspicions about integrity (e.g. as a consequence of employment by the British Government). The public viewed friends and relatives as the most trusted source for volcanic information. High trust in this source allowed competing messages to reinforce beliefs of lower risk than were officially being described. The scientists were the second most trusted group by the public and considered significantly more competent, reliable, caring, fair and open than the authorities. The world press was the least trusted, preceded closely by the British Governor’s Office and Montserratian Government officials. These results tally well with other empirical findings suggesting that government ministers and departments are typically distrusted as sources of risk-related information. These findings have implications for risk communication on Montserrat and other volcanic crises. The importance and potential effectiveness of scientists as communicators, because of, and despite, the existence of political

  12. Geochemical constraints on the link between volcanism and plutonism at the Yunshan caldera complex, SE China (United States)

    Yan, Lili; He, Zhenyu; Beier, Christoph; Klemd, Reiner


    The Yunshan caldera complex is part of a larger scale, ca. 2000-km-long volcanic-plutonic complex belt in the coastal region of SE China. The volcanic rocks in the caldera complex are characterized by high-silica peraluminous and peralkaline rhyolites associated with an intracaldera porphyritic quartz monzonite pluton. In this study, we present zircon U-Pb, Hf and stable O isotopes along with geochemical data of both volcanic and plutonic rocks to evaluate the potential petrogenetic link between volcanism and plutonism in the Yunshan caldera complex. SHRIMP zircon U-Pb geochronology of both volcanic and plutonic rocks yields almost identical ages ranging from 95.6 to 93.1 Ma. The peraluminous and peralkaline rhyolites show negative anomalies of Sr, P, Ti and Ba and to a lesser extent negative Nb and Ta anomalies, along with positive Rb anomalies and `seagull-like' rare earth element (REE) patterns with negative Eu anomalies and low (La/Yb)N ratios. The intracaldera porphyritic quartz monzonite displays minor negative Rb, Nb, Ta, Sr, P and Ti anomalies and a positive Ba anomaly with REE patterns characterized by relatively high (La/Yb)N ratios and lack significant Eu anomalies. The peraluminous and peralkaline rhyolites and the porphyritic quartz monzonite exhibit consistent ɛ Nd( t) of - 3.7 to - 2.2 and display zircon ɛ Hf( t) values of - 2.1 to 3.7. They further have similar, mantle-like, zircon oxygen isotopic compositions (δ18OVSMOW mainly = 4.63 to 5.76‰). We interpret these observations to be in agreement with a crystal mush model in which the parental magma of the volcanic and plutonic rocks of the Yunshan caldera complex was likely produced by interaction of asthenosphere melts with subduction-influenced enriched mantle wedge. The peralkaline rhyolites are interpreted to represent the most differentiated magma that has subsequently experienced significant fluid-melt interactions, whereas the porphyritic quartz monzonite may be representative of the

  13. Volcanic Alert System (VAS) developed during the (2011-2013) El Hierro (Canary Islands) volcanic process (United States)

    Ortiz, Ramon; Berrocoso, Manuel; Marrero, Jose Manuel; Fernandez-Ros, Alberto; Prates, Gonçalo; De la Cruz-Reyna, Servando; Garcia, Alicia


    In volcanic areas with long repose periods (as El Hierro), recently installed monitoring networks offer no instrumental record of past eruptions nor experience in handling a volcanic crisis. Both conditions, uncertainty and inexperience, contribute to make the communication of hazard more difficult. In fact, in the initial phases of the unrest at El Hierro, the perception of volcanic risk was somewhat distorted, as even relatively low volcanic hazards caused a high political impact. The need of a Volcanic Alert System became then evident. In general, the Volcanic Alert System is comprised of the monitoring network, the software tools for the analysis of the observables, the management of the Volcanic Activity Level, and the assessment of the threat. The Volcanic Alert System presented here places special emphasis on phenomena associated to moderate eruptions, as well as on volcano-tectonic earthquakes and landslides, which in some cases, as in El Hierro, may be more destructive than an eruption itself. As part of the Volcanic Alert System, we introduce here the Volcanic Activity Level which continuously applies a routine analysis of monitoring data (particularly seismic and deformation data) to detect data trend changes or monitoring network failures. The data trend changes are quantified according to the Failure Forecast Method (FFM). When data changes and/or malfunctions are detected, by an automated watchdog, warnings are automatically issued to the Monitoring Scientific Team. Changes in the data patterns are then translated by the Monitoring Scientific Team into a simple Volcanic Activity Level, that is easy to use and understand by the scientists and technicians in charge for the technical management of the unrest. The main feature of the Volcanic Activity Level is its objectivity, as it does not depend on expert opinions, which are left to the Scientific Committee, and its capabilities for early detection of precursors. As a consequence of the El Hierro

  14. Volcanic sequence in Late Triassic – Jurassic siliciclastic and evaporitic rocks from Galeana, NE Mexico

    International Nuclear Information System (INIS)

    Cruz-Gómez, E.M.; Velasco-Tapia, F.; Ramírez-Fernández, J.A.; Jenchen, U.; Rodríguez-Saavedra, P.; Rodríguez-Díaz, A.A.; Iriondo, A.


    In northeastern Mexico, volcanic rocks interbedded with Late Triassic–Jurassic siliciclastic and evaporitic strata have been linked to magmatic arcs developed in the Pangea western margin during its initial phase of fragmentation. This work provides new petrographic and geochemical data for volcanism included in the El Alamar and Minas Viejas formations outcropping in the Galeana region. Andesitic dykes and sills (n= 10) in the El Alamar redbeds show SiO2= 47.5–59.1% and MgO= 1.2–4.2%, as well as a geochemical affinity to island arc magmas. This work represents the first report of this tectonic setting in the region. Geological and petrographic evidence suggest that this arc system likely developed after ~220 and before ~193Ma. Trachy-andesitic and rhyodacitic domes (n= 20) associated with the Minas Viejas gypsum-carbonates sequence show SiO2= 61.8–82.7% and MgO= 0.1–4.0% with a tectonic affinity to continental arc. A rhyodacite sample from this region has been dated by U-Pb in zircon, yielding an age of 149.4 ± 1.2Ma (n= 21), being the youngest age related to this arc. Finally, we propose a threestep model to explain the tectonic evolution from Late Triassic island arc to Jurassic continental arc system in the northeastern Mexico.

  15. Volcanic sequence in Late Triassic – Jurassic siliciclastic and evaporitic rocks from Galeana, NE Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Cruz-Gómez, E.M.; Velasco-Tapia, F.; Ramírez-Fernández, J.A.; Jenchen, U.; Rodríguez-Saavedra, P.; Rodríguez-Díaz, A.A.; Iriondo, A.


    In northeastern Mexico, volcanic rocks interbedded with Late Triassic–Jurassic siliciclastic and evaporitic strata have been linked to magmatic arcs developed in the Pangea western margin during its initial phase of fragmentation. This work provides new petrographic and geochemical data for volcanism included in the El Alamar and Minas Viejas formations outcropping in the Galeana region. Andesitic dykes and sills (n= 10) in the El Alamar redbeds show SiO2= 47.5–59.1% and MgO= 1.2–4.2%, as well as a geochemical affinity to island arc magmas. This work represents the first report of this tectonic setting in the region. Geological and petrographic evidence suggest that this arc system likely developed after ~220 and before ~193Ma. Trachy-andesitic and rhyodacitic domes (n= 20) associated with the Minas Viejas gypsum-carbonates sequence show SiO2= 61.8–82.7% and MgO= 0.1–4.0% with a tectonic affinity to continental arc. A rhyodacite sample from this region has been dated by U-Pb in zircon, yielding an age of 149.4 ± 1.2Ma (n= 21), being the youngest age related to this arc. Finally, we propose a threestep model to explain the tectonic evolution from Late Triassic island arc to Jurassic continental arc system in the northeastern Mexico.

  16. The correlation between geomagnetic field reversals, Hawaiian volcanism, and the motion of the Pacific plate

    Directory of Open Access Journals (Sweden)

    W. Dong


    Full Text Available The correlation between geomagnetic field reversals and volcanism is investigated, according to the speculated consequence on volcanoes of the transient electric currents in the geodynamo, through Joule's heating, before and after every reversal event. We evaluate the temporal variation during the last ~ 70 Ma both of the magma emplacement rate Q(t from the Hawaii hot spot, and of the speed v(t of the Pacific plate, by means of the observed volumes of islands and seamounts along the Hawaii/Emperor Seamounts chain, and their respective radiometric datings. Results confirm expectations. A justification of the volcanic crises that lead to the generation of the large igneous provinces during the last ~ 250 Ma also emerged. We describe in detail the complex pattern of the timings of the different effects. Joule's power is generally responsible for ~ 75-80% of magmatism, and friction power only for ~ 20-25%; but, on some occasions almost ~ 100% is fuelled by friction alone. The visco-elastic coupling between lithosphere and asthenosphere results ~ 96% viscous, and ~ 4% elastic.

  17. Collision-induced post-plateau volcanism: Evidence from a seamount on Ontong Java Plateau (United States)

    Hanyu, Takeshi; Tejada, Maria Luisa G.; Shimizu, Kenji; Ishizuka, Osamu; Fujii, Toshiyuki; Kimura, Jun-Ichi; Chang, Qing; Senda, Ryoko; Miyazaki, Takashi; Hirahara, Yuka; Vaglarov, Bogdan S.; Goto, Kosuke T.; Ishikawa, Akira


    Many seamounts on the Ontong Java Plateau (OJP) occur near the Stewart Arch, a topographic high that extends parallel to the North Solomon Trench along the southern margins of the plateau. Despite the thick sediment cover, several volcanic cones with strong acoustic reflection were discovered on the submarine flank of the Nuugurigia Seamount. From such volcanic cones, basalts were successfully sampled by dredging. Radiometric dating of basalts and ferromanganese encrustation indicate eruption age of 20-25 Ma, significantly younger than the 122 Ma main OJP plateau and post-plateau basalts. The age range coincides with the collision of the OJP with the Solomon Arc. The Nuugurigia basalts geochemically differ from any other rocks sampled on the OJP so far. They are alkali basalts with elevated Sr, low Zr and Hf, and Enriched Mantle-I (EMI)-like isotopic composition. Parental magmas of these alkali basalts may have formed by small-degree melting of peridotitic mantle impregnated with recycled pyroxenite material having enriched geochemical composition in the OJP's mantle root. We conclude that small-volume alkali basalts from the enriched mantle root migrated through faults or fractures caused by the collision along the Stewart Arch to form the seamount. Our results suggest that the collision of the OJP with the Solomon arc played an important role in the origin of similar post-plateau seamounts along the Stewart Arch.

  18. Resident perception of volcanic hazards and evacuation procedures

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    D. K. Bird


    Full Text Available Katla volcano, located beneath the Mýrdalsjökull ice cap in southern Iceland, is capable of producing catastrophic jökulhlaup. The Icelandic Civil Protection (ICP, in conjunction with scientists, local police and emergency managers, developed mitigation strategies for possible jökulhlaup produced during future Katla eruptions. These strategies were tested during a full-scale evacuation exercise in March 2006. A positive public response during a volcanic crisis not only depends upon the public's knowledge of the evacuation plan but also their knowledge and perception of the possible hazards. To improve the effectiveness of residents' compliance with warning and evacuation messages it is important that emergency management officials understand how the public interpret their situation in relation to volcanic hazards and their potential response during a crisis and apply this information to the ongoing development of risk mitigation strategies. We adopted a mixed methods approach in order to gain a broad understanding of residents' knowledge and perception of the Katla volcano in general, jökulhlaup hazards specifically and the regional emergency evacuation plan. This entailed field observations during the major evacuation exercise, interviews with key emergency management officials and questionnaire survey interviews with local residents. Our survey shows that despite living within the hazard zone, many residents do not perceive that their homes could be affected by a jökulhlaup, and many participants who perceive that their homes are safe, stated that they would not evacuate if an evacuation warning was issued. Alarmingly, most participants did not receive an evacuation message during the exercise. However, the majority of participants who took part in the exercise were positive about its implementation. This assessment of resident knowledge and perception of volcanic hazards and the evacuation plan is the first of its kind in

  19. Assessing qualitative long-term volcanic hazards at Lanzarote Island (Canary Islands) (United States)

    Becerril, Laura; Martí, Joan; Bartolini, Stefania; Geyer, Adelina


    Conducting long-term hazard assessment in active volcanic areas is of primary importance for land-use planning and defining emergency plans able to be applied in case of a crisis. A definition of scenario hazard maps helps to mitigate the consequences of future eruptions by anticipating the events that may occur. Lanzarote is an active volcanic island that has hosted the largest (> 1.5 km3 DRE) and longest (6 years) eruption, the Timanfaya eruption (1730-1736), on the Canary Islands in historical times (last 600 years). This eruption brought severe economic losses and forced local people to migrate. In spite of all these facts, no comprehensive hazard assessment or hazard maps have been developed for the island. In this work, we present an integrated long-term volcanic hazard evaluation using a systematic methodology that includes spatial analysis and simulations of the most probable eruptive scenarios.

  20. Assessing qualitative long-term volcanic hazards at Lanzarote Island (Canary Islands

    Directory of Open Access Journals (Sweden)

    L. Becerril


    Full Text Available Conducting long-term hazard assessment in active volcanic areas is of primary importance for land-use planning and defining emergency plans able to be applied in case of a crisis. A definition of scenario hazard maps helps to mitigate the consequences of future eruptions by anticipating the events that may occur. Lanzarote is an active volcanic island that has hosted the largest (>  1.5 km3 DRE and longest (6 years eruption, the Timanfaya eruption (1730–1736, on the Canary Islands in historical times (last 600 years. This eruption brought severe economic losses and forced local people to migrate. In spite of all these facts, no comprehensive hazard assessment or hazard maps have been developed for the island. In this work, we present an integrated long-term volcanic hazard evaluation using a systematic methodology that includes spatial analysis and simulations of the most probable eruptive scenarios.

  1. Is there a geochemical link between volcanic and plutonic rocks in the Organ Mountains caldera? (United States)

    Memeti, V.; Davidson, J.


    Results from separate volcanic and plutonic studies have led to inconsistent conclusions regarding the origins and thus links between volcanic and plutonic systems in continental arcs and the magmatic processes and time scales responsible for their compositional variations. Some have suggested that there is a geochemical and geochronological disconnect between volcanic and plutonic rocks and hence have questioned the existence of magma mush columns beneath active volcanoes. Investigating contemporary volcanic and plutonic rocks that are spatially connected is thus critical in exploring these issues. The ca. 36 Ma Organ Mountains caldera in New Mexico, USA, represents such a system exposing contemporaneous volcanic and plutonic rocks juxtaposed at the surface due to tilting during extensional tectonics along the Rio Grande Rift. Detailed geologic and structural mapping [1] and 40Ar/39Ar ages of both volcanics and plutons [2] demonstrate the spatial and temporal connection of both rock types with active magmatism over >2.5 myr. Three caldera-forming ignimbrites erupted within 600 kyr [2] from this system with a total erupted volume of 500-1,000 km3 as well as less voluminous pre- and post-caldera trachyte and andesite lavas. The ignimbrite sequence ranges from a crystal-poor, high-SiO2 rhyolite at the base to a more crystal-rich, low-SiO2 rhyolite at the top. Compositional zoning with quartz-monzonite at the base grading to syenite and alaskite at the top is also found in the Organ Needle pluton, the main intrusion, which is interpreted to be the source for the ignimbrites [1]. Other contemporaneous and slightly younger plutons have dioritic to leucogranitic compositions. We examined both volcanic and plutonic rocks with petrography and their textural variations with color cathodoluminescence, and used whole rock element and Sr, Nd and Pb isotope geochemistry to constrain magma compositions and origins. Electron microprobe analyses on feldspars have been completed to

  2. SDSS-IV MaNGA: Probing the Kinematic Morphology–Density Relation of Early-type Galaxies with MaNGA (United States)

    Greene, J. E.; Leauthaud, A.; Emsellem, E.; Goddard, D.; Ge, J.; Andrews, B. H.; Brinkman, J.; Brownstein, J. R.; Greco, J.; Law, D.; Lin, Y.-T.; Masters, K. L.; Merrifield, M.; More, S.; Okabe, N.; Schneider, D. P.; Thomas, D.; Wake, D. A.; Yan, R.; Drory, N.


    The “kinematic” morphology–density relation for early-type galaxies posits that those galaxies with low angular momentum are preferentially found in the highest-density regions of the universe. We use a large sample of galaxy groups with halo masses {10}12.5MaNGA) survey to examine whether there is a correlation between local environment and rotational support that is independent of stellar mass. We find no compelling evidence for a relationship between the angular momentum content of early-type galaxies and either local overdensity or radial position within the group at fixed stellar mass.

  3. Ages of plains volcanism on Mars (United States)

    Hauber, Ernst; Jagert, Felix; Broz, Petr


    Plain-style volcanism [1] is widespread in the Tharsis and Elysium volcanic provinces on Mars, [2,3]. Detailed images and topographic data reveal the morphology and topography of clusters of low shields and associated lava flows. The landforms of plains volcanism on Mars have all well-known terrestrial analogues in basaltic volcanic regions, such as Hawaii, Iceland, and in particular the Snake River Plains [4]. The very gentle flank slopes (J. (1981) Icarus, 45, 586-601. [3] Hodges C.A. and Moore H.J. (1994) Atlas of volcanic features on Mars: USGS Prof. Paper 1534, 194 p. [4] Hauber E. et al. (2009) J. Volcanol. Geotherm. Res. 185, 69-95. [5] Wilson L. et al. (2009) J. Volcanol. Geotherm. Res. 185, 28-46. [6] Vaucher, J. et al. (2009) Icarus 204, 418-442. [7] Baratoux D. et al. (2009) J. Volcanol. Geotherm. Res. 185, 47-68. [8] Bleacher J.E. et al. (2009) J. Volcanol. Geotherm. Res. 185, 96-102. [9] Ivanov B.A. (2001) Space Sci. Rev. 96, 87-104. [10] Hartmann W.H. and Neukum G. (2001) Space Sci. Rev. 96, 165-194 [11] Kneissl T. et al. (2010) LPS XVI, submitted. [12] Michael, G.G. and Neukum G. (2010) Earth Planet. Sci. Lett., in press. . [13] Malin M.C. et al. (2007) JGR 112, E05S04, doi: 10.1029/2006JE002808.

  4. Paleogene volcanism in Central Afghanistan: Possible far-field effect of the India-Eurasia collision (United States)

    Motuza, Gediminas; Šliaupa, Saulius


    A volcanic-sedimentary succession of Paleogene age is exposed in isolated patches at the southern margin of the Tajik block in the Ghor province of Central Afghanistan. The volcanic rocks range from basalts and andesites to dacites, including adakites. They are intercalated with sedimentary rocks deposited in shallow marine environments, dated biostratigraphically as Paleocene-Eocene. This age corresponds to the age of the Asyābēd andesites located in the western Ghor province estimated by the 40Ar/39Ar method as 54 Ma. The magmatism post-dates the Cimmerian collision between the Tajik block (including the Band-e-Bayan block) and the Farah Rod block located to the south. While the investigated volcanic rocks apparently bear geochemical signatures typical to an active continental margin environment, it is presumed that the magmatism was related to rifting processes most likely initiated by far-field tectonics caused by the terminal collision of the Indian plate with Eurasia (Najman et al., 2017). This event led to the dextral movement of the Farah Rod block, particularly along Hari Rod (Herat) fault system, resulting in the development of a transtensional regime in the proximal southern margin of the Tajik block and giving rise to a rift basin where marine sediments were interbedded with pillow lavas intruded by sheeted dyke series.

  5. Change management in bank M&A

    Directory of Open Access Journals (Sweden)

    Kontić Ljiljana


    Full Text Available This paper examines the issues of change management in merger and acquisitions (M&As using the mixed method research approach. The research setting consisted of a foreign bank that operates in Serbia. The main aim of this study is to examine willingness for change in bank M&A. The qualitative data about the bank were sourced from publicly available information about the bank. The standardized questionnaire is used to assess bank's willingness for change. Based on managers structure, the representative sample of middle managers has been interviewed in this study. The research findings revealed possible practical implementation of the questionnaire in the Serbian banking sector. The results revealed that changes in bank should be led top down. The findings add to the existing literature on success factors in cross-border mergers and acquisitions. The study limitation are suggested.

  6. Active Volcanic Eruptions on Io (United States)


    Six views of the volcanic plume named Prometheus, as seen against Io's disk and near the bright limb (edge) of the satellite by the SSI camera on the Galileo spacecraft during its second (G2) orbit of Jupiter. North is to the top of each frame. To the south-southeast of Prometheus is another bright spot that appears to be an active plume erupting from a feature named Culann Patera. Prometheus was active 17 years ago during both Voyager flybys, but no activity was detected by Voyager at Culann. Both of these plumes were seen to glow in the dark in an eclipse image acquired by the imaging camera during Galileo's first (G1) orbit, and hot spots at these locations were detected by Galileo's Near-Infrared Mapping Spectrometer.The plumes are thought to be driven by heating sulfur dioxide in Io's subsurface into an expanding fluid or 'geyser'. The long-lived nature of these eruptions requires that a substantial supply of sulfur dioxide must be available in Io's subsurface, similar to groundwater. Sulfur dioxide gas condenses into small particles of 'snow' in the expanding plume, and the small particles scatter light and appear bright at short wavelengths. The images shown here were acquired through the shortest-wavelength filter (violet) of the Galileo camera. Prometheus is about 300 km wide and 75 km high and Culann is about 150 km wide and less than 50 km high. The images were acquired on September 4, 1996 at a range of 2,000,000 km (20 km/pixel resolution). Prometheus is named after the Greek fire god and Culann is named after the Celtic smith god.The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL Background information and educational context for the images can

  7. Evidence in Variscan Corsica of a brief and voluminous Late Carboniferous to Early Permian volcanic-plutonic event contemporaneous with a high-temperature/low-pressure metamorphic peak in the lower crust

    International Nuclear Information System (INIS)

    Rossi, Philippe; Cocherie, Alain; Fanning, C. Mark


    The U2 group of plutonic rocks constituting the main exposed part of the Corsica-Sardinia batholith (CSB) was emplaced from 308 to 275 Ma (the early Visean U1 group of Mg-K intrusions is not considered here). Field evidence earlier established volcanic-plutonic relationships in the U2 group of calc-alkaline intrusions of the CSB, though detailed chronological data were still lacking. Large outcrops of U2 volcanic formations are restricted to the less eroded zone north-west of the Porto-Ponte Leccia line in Corsica, but volcanic and volcano-sedimentary formations were widely eroded elsewhere since Permian times. They probably covered most of the batholith before the Miocene, as testified by the volcanic nature of the pebbles that form much of the Early Miocene conglomerates of eastern Corsica. U-Pb zircon dating (SHRIMP) was used for deciphering the chronology and duration of different volcanic pulses and for better estimating the time overlap between plutonic and volcanic rock emplacement in the CSB. The obtained ages fit well with field data, showing that most of the U2 and U3 volcanic formations were emplaced within a brief time span of roughly 15 m.y., from 293 to 278 Ma, coeval with most U2 monzo-granodiorites and leuco-monzo-granites (295-280 Ma), alkaline U3 complexes (about 288 Ma), and mafic-ultramafic tholeiitic complexes (295-275 Ma). The same chronological link between deep-seated magma chambers and eruptions was identified in the Pyrenees. These results correlate with U-Pb zircon dating of HT-LP granulites from the Variscan deep crust exhumed along the 'European' margin of the thinned Tethys margin in Corsica and Calabria. Here, the peak of the low-pressure/high-temperature metamorphism was dated at about 285-280 Ma. Our results throw light on the condition of magma production during the orogenic collapse in the southern Variscan realm. While juvenile tholeiitic basaltic magma was produced by the melting of spinel mantle lithosphere, all

  8. Geochemical and geophysical monitoring activities in Campo de Calatrava Volcanic Field (Spain) (United States)

    Luengo-Oroz, Natividad; Villasante-Marcos, Víctor; López-Díaz, Rubén; Calvo, Marta; Albert, Helena; Domínguez Cerdeña, Itahiza


    The Campo de Calatrava Volcanic Field (CCVF) or Spanish Central Volcanic Zone is located in central continental Spain (Ciudad Real province) and covers about 5000 km2. It includes around 240 eruptive centers, mainly monogenetic basaltic cones but also explosive maar structures. According to K-Ar geochronology, its main activity phase occurred during Pliocene and Pleistocene epochs (between 5 and 1.7 Ma) and involved alkaline to ultraalkaline magmas, although an older ultrapotassic phase is dated around 8.7-6.4 Ma. However, some recent works have proposed Holocene ages for some of the volcanic products, opening the possibility of considering the CCVF "active" according to international standards. Responding to this situation, the Instituto Geográfico Nacional (IGN) has initiated geochemical and geophysical monitoring activities in the CCVF. Here, we describe these ongoing efforts and we report results about groundwater geochemistry at several natural highly-gaseous springs in the area (hervideros), as well as soil temperature, CO2 diffuse flux from the soil and electrical self-potential data mapped on a small degassing structure called La Sima. In order to analyze microseismicity or any seismic anomaly in the CCVF, a seismic station has also been installed close to this degassing structure. Physicochemical parameters (temperature, pH, Eh and electric conductivity) were measured in situ in four springs and samples were taken in order to analyze major ions and trace elements. Total composition of dissolved gases and helium isotopic ratios were also determined. To complete soil temperature, self-potential and gas prospections performed in La Sima, soil gases were sampled at the bottom of the structure at a depth of 20 cm. Analysis of the total gas composition found 957400 ppm of CO2. Low values of O2 and N2 were also detected (5600 and 24800 ppm respectively).

  9. Vestiges of the proto-Caribbean seaway: Origin of the San Souci Volcanic Group, Trinidad (United States)

    Neill, Iain; Kerr, Andrew C.; Chamberlain, Kevin R.; Schmitt, Axel K.; Urbani, Franco; Hastie, Alan R.; Pindell, James L.; Barry, Tiffany L.; Millar, Ian L.


    Outcrops of volcanic-hypabyssal rocks in Trinidad document the opening of the proto-Caribbean seaway during Jurassic-Cretaceous break-up of the Americas. The San Souci Group on the northern coast of Trinidad comprises the San Souci Volcanic Formation (SSVF) and passive margin sediments of the ~ 130-125 Ma Toco Formation. The Group was trapped at the leading edge of the Pacific-derived Caribbean Plate during the Cretaceous-Palaeogene, colliding with the para-autochthonous margin of Trinidad during the Oligocene-Miocene. In-situ U-Pb ion probe dating of micro-zircons from a mafic volcanic breccia reveal the SSVF crystallised at 135.0 ± 7.3 Ma. The age of the SSVF is within error of the age of the Toco Formation. Assuming a conformable contact, geodynamic models indicate a likely origin for the SSVF on the passive margin close to the northern tip of South America. Immobile element and Nd-Hf radiogenic isotope signatures of the mafic rocks indicate the SSVF was formed by ≪10% partial melting of a heterogeneous spinel peridotite source with no subduction or continental lithospheric mantle component. Felsic breccias within the SSVF are more enriched in incompatible elements, with isotope signatures that are less radiogenic than the mafic rocks of the SSVF. The felsic rocks may be derived from re-melting of mafic crust. Although geochemical comparisons are drawn here with proto-Caribbean igneous outcrops in Venezuela and elsewhere in the Caribbean more work is needed to elucidate the development of the proto-Caribbean seaway and its rifted margins. In particular, ion probe dating of micro-zircons may yield valuable insights into magmatism and metamorphism in the Caribbean, and in altered basaltic terranes more generally.

  10. Isotope dates and strontium isotopic ratios for plutonic and volcanic rocks in the Quesnel Trough and Nicola Belt, south central British Columbia

    International Nuclear Information System (INIS)

    Preto, V.A.; McMillan, W.J.; Armstrong, R.L.


    Four distinct events of the southern Intermontane Belt are represented in new K-Ar and Rb-Sr dates. The first and regionally most important event is sharply defined by new K-Ar dates between 200 and 209 Ma for the Thuya, Wildhorse, Iron Mask, and Allison batholiths and a 205 +- 10 Ma Rb-Sr isochron for the Guichon Creek batholith. All these plutons were emplaced approximately at the change from Triassic to Jurassic time. The related and slightly older Nicola volcanic rocks are altered by addition of more radiogenic sedimentary Sr (Carnian Nicola limestone having 87 Sr/ 86 Sr=0.7075+- 1) and do not give an isochron date. The Coldwater stock is anomalously old (K-Ar dates range from 215-267 Ma). The Mid- to late Jurassic igneous event is indicated by a 141 Ma K-Ar date for the Mount Martley batholith. Mid-Cretaceous volcanic rocks of the Kingsvale Group give a Rb-Sr isochron date of 112 +- 10 Ma and are postdated by the crosscutting and slightly younger Summers Creek stock (100 Ma by K-Ar). The final event straddles the Cretaceous-Tertiary boundary with the Nicola batholith emplaced about 60 Ma ago (K-Ar) and the Rey Lake stock perhaps slightly earlier (69 Ma by K-Ar). Initial 87 Sr/ 86 Sr ratios range from 0.7025-0.7046 with a mean and mode near 0.7037 which is within the range of modern circum-Pacific volcanoes. Initial ratios of 0.7034 +- 1 for the Guichon Creek batholith, 0.7035 +- 1 for the Iron Mask batholith 70435 +-10 for the Thuya batholith, and 0.70379 +- 4 for the Kingsvale volcanic rocks are the most precisely determined. The Coldwater stock is anomalously low at 0.7025. For the other plutonic bodies only scattered or single analyses are available. The Nicola volcanic rocks appear to have once been similar in initial ratio the the Guichon Creek batholith but their calculated initial ratios now scatter from 0.7034-0.7073. (auth)


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    Donghai Zhang


    Full Text Available We report a paleomagnetic investigation on Permian volcanic rocks in the middle-east Inner Mongolia, NE China, aiming to puzzle out the timing and position of the final closure of the eastern Paleo-Asian ocean (PAO and further to better understand tectonic evolution of the Central Asian Orogenic Belt (CAOB. Two pre-folding characteristic components are isolated from the Sanmianjing and Elitu formations (~283–266 Ma in the northern margin of the North China block (NMNCB and the Dashizhai Formation (~280 Ma in the Songliao-Xilinhot block (SXB, respectively.

  12. National volcanic ash operations plan for aviation (United States)

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    The National Aviation Weather Program Strategic Plan (1997) and the National Aviation Weather Initiatives (1999) both identified volcanic ash as a high-priority informational need to aviation services. The risk to aviation from airborne volcanic ash is known and includes degraded engine performance (including flameout), loss of visibility, failure of critical navigational and operational instruments, and, in the worse case, loss of life. The immediate costs for aircraft encountering a dense plume are potentially major—damages up to $80 million have occurred to a single aircraft. Aircraft encountering less dense volcanic ash clouds can incur longer-term costs due to increased maintenance of engines and external surfaces. The overall goal, as stated in the Initiatives, is to eliminate encounters with ash that could degrade the in-flight safety of aircrews and passengers and cause damage to the aircraft. This goal can be accomplished by improving the ability to detect, track, and forecast hazardous ash clouds and to provide adequate warnings to the aviation community on the present and future location of the cloud. To reach this goal, the National Aviation Weather Program established three objectives: (1) prevention of accidental encounters with hazardous clouds; (2) reduction of air traffic delays, diversions, or evasive actions when hazardous clouds are present; and (3) the development of a single, worldwide standard for exchange of information on airborne hazardous materials. To that end, over the last several years, based on numerous documents (including an OFCMsponsored comprehensive study on aviation training and an update of Aviation Weather Programs/Projects), user forums, and two International Conferences on Volcanic Ash and Aviation Safety (1992 and 2004), the Working Group for Volcanic Ash (WG/VA), under the OFCM-sponsored Committee for Aviation Services and Research, developed the National Volcanic Ash Operations Plan for Aviation and Support of the

  13. Reconsideration of evolutionary model of the Hawaiian-type volcano: 40Ar/39Ar ages for lavas from deep interior of Oahu Island and alkali basalts from the North Arch volcanic field (United States)

    Uto, K.; Ishizuka, O.; Garcia, M. O.; Clague, D. A.; Naka, J.


    Growth history of Hawaiian-type volcanoes is typified into four stages: pre-shield, shield-forming, post-shield and rejuvinated. Duration of volcanism from pre-shield to post-shield stage is considered to be at most two million years, and is followed by the rejuvinated-stage after the dormance of one to two million years. There are, however, considerable amount of volcanic products hidden beneath the surface, and the above model may not be real due to the limited observation. US-Japan joint research on Hawaiian volcanism using ROV {\\KAIKO} and submersible {\\SHINKAI6500} of JAMSTEC has revealed many unknown volcanic processes of Hawaii. We challenge the well-established growth model of Hawaiian volcanoes from 40Ar/39Ar dating on rocks collected from the deep root of the submarine cliff of Oahu Island and from the widespread lava field off the coast of Oahu. Northern slope of Oahu Island is a deeply dissected steep wall from the ridge 1,000 m above the sea level to 3,000 m beneath the sea level. We expected to discover the deeper part of volcanic products forming Oahu Island. We obtained 6 40Ar/39Ar ages for tholeiitic lavas collected from 3,000 m to 2,600 m below the sea level. Ages are 5.7 and 6 Ma for two samples from the depth of 2,800 - 3,000 m, 4 Ma for a sample from 2,630 m, 3 Ma for a rock dredged between 2,500 and 2,800m, and 2.2 Ma for a sample from 2,602 m. Ages between 2.2 and 4 Ma are compatible with existing ages on subaerial shield-forming lavas on Koolau and Waianae volcano on Oahu, but ages of 5.7 and 6 Ma are about two million years older. Duplicate analyses gave concordant results and isochron ages have atmospheric 40Ar/36Ar initials. We, therefore, consider that these ages represent eruptive ages of samples. Current results suggest that tholeiitic volcanism forming Oahu Island continued almost 4 million years, which is far longer than ever considered. Considering the 8.7 cm/y of plate velocity, volcanism continued while Oahu Island moved 350 km

  14. Venus - Volcanic features in Atla Region (United States)


    This Magellan image from the Atla region of Venus shows several types of volcanic features and superimposed surface fractures. The area in the image is approximately 350 kilometers (217 miles) across, centered at 9 degrees south latitude, 199 degrees east longitude. Lava flows emanating from circular pits or linear fissures form flower-shaped patterns in several areas. A collapse depression approximately 20 kilometers by 10 kilometers (12 by 6 miles) near the center of the image is drained by a lava channel approximately 40 kilometers (25 miles) long. Numerous surface fractures and graben (linear valleys) criss-cross the volcanic deposits in north to northeast trends. The fractures are not buried by the lavas, indicating that the tectonic activity post-dates most of the volcanic activity.

  15. Ozone depletion following future volcanic eruptions (United States)

    Eric Klobas, J.; Wilmouth, David M.; Weisenstein, Debra K.; Anderson, James G.; Salawitch, Ross J.


    While explosive volcanic eruptions cause ozone loss in the current atmosphere due to an enhancement in the availability of reactive chlorine following the stratospheric injection of sulfur, future eruptions are expected to increase total column ozone as halogen loading approaches preindustrial levels. The timing of this shift in the impact of major volcanic eruptions on the thickness of the ozone layer is poorly known. Modeling four possible climate futures, we show that scenarios with the smallest increase in greenhouse gas concentrations lead to the greatest risk to ozone from heterogeneous chemical processing following future eruptions. We also show that the presence in the stratosphere of bromine from natural, very short-lived biogenic compounds is critically important for determining whether future eruptions will lead to ozone depletion. If volcanic eruptions inject hydrogen halides into the stratosphere, an effect not considered in current ozone assessments, potentially profound reductions in column ozone would result.

  16. Geochemistry of volcanic series of Aragats province

    International Nuclear Information System (INIS)

    Meliksetyan, Kh.B.


    In this contribution we discuss geochemical and isotope characteristics of volcanism of the Aragats volcanic province and possible petrogenetical models of magma generation in collision zone of Armenian highland. We talk about combination of some specific features of collision related volcanism such as dry and high temperature conditions of magma generation, that demonstrate some similarities to intraplate-like petrogenesis and presence of mantle source enriched by earlier subductions, indicative to island-arc type magma generation models. Based on comprehensive analysis of isotope and geochemical data and some published models of magma generation beneath Aragats we lead to a petrogenetic model of origin of Aragats system to be a result of magma mixture between mantle originated mafic magma with felsic, adakite-type magmas

  17. Zircon U-Pb geochronology, Sm-Nd and Pb-Pb isotope systematics of Ediacaran post-collisional high-silica Acampamento Velho volcanism at the Tupanci area, NW of the Sul-Rio-Grandense Shield, Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Sommer, Carlos Augusto; Leitzke, Felipe Padilha; Lima, Evandro Fernandes de; Barreto, Carla Joana Santos; Matté, Vinicius; Philipp, Ruy Paulo; Conceição, Rommulo Vieira, E-mail:, E-mail:, E-mail:, E-mail: [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil). Instituto de Geociências; Lafon, Jean Michel, E-mail: [Universidade Federal do Pará (UFPA), Belém, PA (Brazil). Laboratório de Geologia Isotópica; Basei, Miguel Ângelo Stipp, E-mail: [Universidade de São Paulo (CPGeo/IGc/USP), São Paulo, SP (Brazil)


    We present new U-Pb zircon ages and Sm-Nd-Pb isotopic data for volcanic and hypabyssal acid rocks from the northernmost exposure of the Acampamento Velho Formation in the NW portion of the Sul-Rio-Grandense Shield, Brazil. The first volcanic episode, grouped in the high-Ti rhyolites from the Tupanci hill, shows age of 579 ± 5.6 Ma, which is in agreement with the post-collisional Acampamento Velho Formation volcanism in the Bom Jardim Group of the Camaquã Basin. A poorly constrained age of 558+/- 39Ma was obtained for rhyolites from the low-Ti group at the Picados Hill, which may indicate a younger acid volcanism, or a greater time span for the volcanism of the Acampamento Velho Formation in southernmost Brazil. Regarding magmatic sources, Sm/Nd isotopic data coupled to Pb isotopes and a review of trace element geochemistry indicate different amounts of Paleoproterozoic (Dom Feliciano, Pinheiro Machado Suite) to Neoproterozoic (Rio Vacacaí terrane) lower crust melting. Our data, coupled with literature data, contribute to a better understanding of the stratigraphic evolution for the Neoproterozoic post-collisional volcanic successions of the Camaquã Basin in the Sul-Rio-Grandense Shield. (author)

  18. Tropical Volcanic Soils From Flores Island, Indonesia

    Directory of Open Access Journals (Sweden)



    Full Text Available Soils that are developed intropical region with volcanic parent materials have many unique properties, and high potential for agricultural use.The purpose of this study is to characterize the soils developed on volcanic materials from Flores Island, Indonesia,and to examine if the soils meet the requirements for andic soil properties. Selected five soils profiles developed fromandesitic volcanic materials from Flores Island were studied to determine their properties. They were compared intheir physical, chemical and mineralogical characteristics according to their parent material, and climatic characteristicdifferent. The soils were developed under humid tropical climate with ustic to udic soil moisture regimes withdifferent annual rainfall. The soils developed from volcanic ash parent materials in Flores Island showed differentproperties compared to the soils derived from volcanic tuff, even though they were developed from the sameintermediary volcanic materials. The silica contents, clay mineralogy and sand fractions, were shown as the differences.The different in climatic conditions developed similar properties such as deep solum, dark color, medium texture, andvery friable soil consistency. The soils have high organic materials, slightly acid to acid, low to medium cationexchange capacity (CEC. The soils in western region have higher clay content and showing more developed than ofthe eastern region. All the profiles meet the requirements for andic soil properties, and classified as Andisols order.The composition of sand mineral was dominated by hornblende, augite, and hypersthenes with high weatherablemineral reserves, while the clay fraction was dominated by disordered kaolinite, and hydrated halloysite. The soilswere classified into subgroup as Thaptic Hapludands, Typic Hapludands, and Dystric Haplustands

  19. Zircon U-Pb chronology, geochemistry and Sr-Nd-Pb isotopic compositions of the Volcanic Rocks in the Elashan area, NW China: petrogenesis and tectonic implications (United States)

    Zhou, H.; Wei, J.; Shi, W.; Li, P.; Chen, M.; Zhao, X.


    Elashan area is located in the intersection of the East Kunlun Orogenic Belt (EKOB) and the West Qinling Orogenic (WQOB). We present petrology, zircon U-Pb ages, whole-rock geochemistry and Sr-Nd-Pb isotopic compositions from the andesite and felsic volcanic rocks (rhyolite and rhyolitic tuffs) in Elashan group volcanic rock. The LA-ICP-MS zircon U-Pb age data indicate that the volcanic rocks are emplaced at 250 247 Ma. The volcanic rocks have high -K and aluminum - peraluminous characteristics, A/CNK = 1.07 1.82, δ ranges from 1.56 2.95, the main body is calc-alkaline rock. They are enriched in large ion lithophile elements (LILEs) and light rare earth elements (LREEs) and depleted in some high field strength elements (HFSEs, e.g., Nb, Ta, P and Ti), while having a flat heavy REE (HREEs) pattern. The ∑REE values of 178.68 to 298.11 ppm, average 230.50 ppm. The LREE/HREE values of 4.39 to 11.78 ppm, average 6.77 ppm. REE fractionation is obvious, REE distribution curve was right smooth, and have slightly negative Eu anomalies (Eu/Eu*=0.44-0.80, average 0.60), which as similar to the island arc volcanic rocks. The volcanic rocks have initial 87Sr/86Sr ratios of 0.71028-0.71232, ɛNd(t) values of -6.7 to -7.6, with T2DM-Nd ranging from 1561 to 1640 Ma. Pb isotopic composition (206 Pb / 204 Pb)t = 18.055 18.330, (207 Pb / 204 Pb)t = 15.586 15.618, (208 Pb / 204 Pb)t = 37.677 38.332. Geochemical and Sr-Nd-Pb isotopes indicates that Elashan group volcanic magma derived mainly from the lower crust. Elashan group volcanic rocks is the productive East Kunlun block and West Qinling block collision, which makes the thicken crust caused partial melting in the study area. The source rocks is probably from metamorphic sandstone of Bayankala. But with Y-Nb and Rb-(Y+Nb), R1-R2 and Rb/10-Hf-Ta*3 diagrams showing that intermediate-acid rocks mainly formed in volcanic arc-collision environment, probably the collision event is short , therefore rocks retain the original island

  20. The geological record of life 3500 Ma ago: Coping with the rigors of a young earth during late accretion (United States)

    Lowe, Donald R.


    Thin cherty sedimentary layers within the volcanic portions of the 3,500 to 3,300 Ma-old Onverwacht and Fig Tree Groups, Barberton Greenstone belt, South Africa, and Warrawoona Group, eastern Pilbara Block, Western Australia, contain an abundant record of early Archean life. Five principal types of organic and probably biogenic remains and or structures can be identifed: stromatolites, stromatolite detritus, carbonaceous laminite or flat stromalite, carbonaceous detrital particles, and microfossils. Early Archean stromatolites were reported from both the Barberton and eastern Pilbara greenstone belts. Systematic studies are lacking, but two main morphological types of stromatolites appear to be represented by these occurrences. Morphology of the stromalites is described. Preserved early Archean stromatolites and carbonaceous matter appear to reflect communities of photosynthetic cyanobacteria inhabiting shallow, probably marine environments developed over the surfaces of low-relief, rapidly subsiding, simatic volcanic platforms. The overall environmental and tectonic conditions were those that probably prevailed at Earth's surface since the simatic crust and oceans formed sometime before 3,800 Ma. Recent studies also suggest that these early Archean sequences contain layers of debris formed by large-body impacts on early Earth. If so, then these early bacterial communities had developed strategies for coping with the disruptive effects of possibly globe-encircling high-temperature impact vapor clouds, dust blankets, and impact-generated tsunamis. It is probable that these early Archean biogenic materials represent organic communities that evolved long before the beginning of the preserved geological record and were well adapted to the rigors of life on a young, volcanically active Earth during late bombardment. These conditions may have had parallels on Mars during its early evolution.

  1. The transcriptional regulatory network mediated by banana (Musa acuminata) dehydration-responsive element binding (MaDREB) transcription factors in fruit ripening. (United States)

    Kuang, Jian-Fei; Chen, Jian-Ye; Liu, Xun-Cheng; Han, Yan-Chao; Xiao, Yun-Yi; Shan, Wei; Tang, Yang; Wu, Ke-Qiang; He, Jun-Xian; Lu, Wang-Jin


    Fruit ripening is a complex, genetically programmed process involving the action of critical transcription factors (TFs). Despite the established significance of dehydration-responsive element binding (DREB) TFs in plant abiotic stress responses, the involvement of DREBs in fruit ripening is yet to be determined. Here, we identified four genes encoding ripening-regulated DREB TFs in banana (Musa acuminata), MaDREB1, MaDREB2, MaDREB3, and MaDREB4, and demonstrated that they play regulatory roles in fruit ripening. We showed that MaDREB1-MaDREB4 are nucleus-localized, induced by ethylene and encompass transcriptional activation activities. We performed a genome-wide chromatin immunoprecipitation and high-throughput sequencing (ChIP-Seq) experiment for MaDREB2 and identified 697 genomic regions as potential targets of MaDREB2. MaDREB2 binds to hundreds of loci with diverse functions and its binding sites are distributed in the promoter regions proximal to the transcriptional start site (TSS). Most of the MaDREB2-binding targets contain the conserved (A/G)CC(G/C)AC motif and MaDREB2 appears to directly regulate the expression of a number of genes involved in fruit ripening. In combination with transcriptome profiling (RNA sequencing) data, our results indicate that MaDREB2 may serve as both transcriptional activator and repressor during banana fruit ripening. In conclusion, our study suggests a hierarchical regulatory model of fruit ripening in banana and that the MaDREB TFs may act as transcriptional regulators in the regulatory network. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

  2. The Quaternary history of effusive volcanism of the Nevado de Toluca area, Central Mexico (United States)

    Torres-Orozco, R.; Arce, J. L.; Layer, P. W.; Benowitz, J. A.


    Andesite and dacite lava flows and domes, and intermediate-mafic cones from the Nevado de Toluca area were classified into five groups using field data and 40Ar/39Ar geochronology constraints. Thirty-four lava units of diverse mineralogy and whole-rock major-element geochemistry, distributed between the groups, were identified. These effusive products were produced between ∼1.5 and ∼0.05 Ma, indicating a mid-Pleistocene older-age for Nevado de Toluca volcano, coexisting with explosive products that suggest a complex history for this volcano. A ∼0.96 Ma pyroclastic deposit attests for the co-existence of effusive and explosive episodes in the mid-Pleistocene history. Nevado de Toluca initiated as a composite volcano with multiple vents until ∼1.0 Ma, when the activity began to centralize in an area close to the present-day crater. The modern main edifice reached its maximum height at ca. 50 ka after bulky, spiny domes erupted in the current summit of the crater. Distribution and geochemical behavior in major elements of lavas indicate a co-magmatic relationship between different andesite and dacite domes and flows, although unrelated to the magmatism of the monogenetic volcanism. Mafic-intermediate magma likely replenished the system at Nevado de Toluca since ca. ∼1.0 Ma and contributed to the eruption of new domes, cones, as well as effusive-explosive activity. Altogether, field and laboratory data suggest that a large volume of magma was ejected around 1 Ma in and around the Nevado de Toluca.

  3. Tellurium in active volcanic environments: Preliminary results (United States)

    Milazzo, Silvia; Calabrese, Sergio; D'Alessandro, Walter; Brusca, Lorenzo; Bellomo, Sergio; Parello, Francesco


    Tellurium is a toxic metalloid and, according to the Goldschmidt classification, a chalcophile element. In the last years its commercial importance has considerably increased because of its wide use in solar cells, thermoelectric and electronic devices of the last generation. Despite such large use, scientific knowledge about volcanogenic tellurium is very poor. Few previous authors report result of tellurium concentrations in volcanic plume, among with other trace metals. They recognize this element as volatile, concluding that volcanic gases and sulfur deposits are usually enriched with tellurium. Here, we present some results on tellurium concentrations in volcanic emissions (plume, fumaroles, ash leachates) and in environmental matrices (soils and plants) affected by volcanic emissions and/or deposition. Samples were collected at Etna and Vulcano (Italy), Turrialba (Costa Rica), Miyakejima, Aso, Asama (Japan), Mutnovsky (Kamchatka) at the crater rims by using common filtration techniques for aerosols (polytetrafluoroethylene filters). Filters were both eluted with Millipore water and acid microwave digested, and analyzed by inductively coupled plasma mass spectrometry (ICP-MS). Volcanic ashes emitted during explosive events on Etna and Copahue (Argentina) were analyzed for tellurium bulk composition and after leaching experiments to evaluate the soluble fraction of tellurium. Soils and leaves of vegetation were also sampled close to active volcanic vents (Etna, Vulcano, Nisyros, Nyiragongo, Turrialba, Gorely and Masaya) and investigated for tellurium contents. Preliminary results showed very high enrichments of tellurium in volcanic emissions comparing with other volatile elements like mercury, arsenic, thallium and bismuth. This suggests a primary transport in the volatile phase, probably in gaseous form (as also suggested by recent studies) and/or as soluble salts (halides and/or sulfates) adsorbed on the surface of particulate particles and ashes. First

  4. Volcanic Eruptions and Climate: Outstanding Research Issues (United States)

    Robock, Alan


    Large volcanic eruptions inject sulfur gases into the stratosphere, which convert to sulfate aerosols with an e-folding residence time of about one year. The radiative and chemical effects of this aerosol cloud produce responses in the climate system. Based on observations after major eruptions of the past and experiments with numerical models of the climate system, we understand much about their climatic impact, but there are also a number of unanswered questions. Volcanic eruptions produce global cooling, and are an important natural cause of interannual, interdecadal, and even centennial-scale climate change. One of the most interesting volcanic effects is the "winter warming" of Northern Hemisphere continents following major tropical eruptions. During the winter in the Northern Hemisphere following every large tropical eruption of the past century, surface air temperatures over North America, Europe, and East Asia were warmer than normal, while they were colder over Greenland and the Middle East. This pattern and the coincident atmospheric circulation correspond to the positive phase of the Arctic Oscillation. While this response is observed after recent major eruptions, most state-of-the-art climate models have trouble simulating winter warming. Why? High latitude eruptions in the Northern Hemisphere, while also producing global cooling, do not have the same impact on atmospheric dynamics. Both tropical and high latitude eruptions can weaken the Indian and African summer monsoon, and the effects can be seen in past records of flow in the Nile and Niger Rivers. Since the Mt. Pinatubo eruption in the Philippines in 1991, there have been no large eruptions that affected climate, but the cumulative effects of small eruptions over the past decade have had a small effect on global temperature trends. Some important outstanding research questions include: How much seasonal, annual, and decadal predictability is possible following a large volcanic eruption? Do

  5. Winter warming from large volcanic eruptions (United States)

    Robock, Alan; Mao, Jianping


    An examination of the Northern Hemisphere winter surface temperature patterns after the 12 largest volcanic eruptions from 1883-1992 shows warming over Eurasia and North America and cooling over the Middle East which are significant at the 95-percent level. This pattern is found in the first winter after tropical eruptions, in the first or second winter after midlatitude eruptions, and in the second winter after high latitude eruptions. The effects are independent of the hemisphere of the volcanoes. An enhanced zonal wind driven by heating of the tropical stratosphere by the volcanic aerosols is responsible for the regions of warming, while the cooling is caused by blocking of incoming sunlight.

  6. Post 4 Ma initiation of normal faulting in southern Tibet. Constraints from the Kung Co half graben (United States)

    Mahéo, G.; Leloup, P. H.; Valli, F.; Lacassin, R.; Arnaud, N.; Paquette, J.-L.; Fernandez, A.; Haibing, L.; Farley, K. A.; Tapponnier, P.


    The timing of E-W extension of the Tibetan plateau provides a test of mechanical models of the geodynamic evolution of the India-Asia convergence zone. In this work we focus on the Kung Co half graben (Southern Tibet, China), bounded by an active N-S normal fault with a minimum vertical offset of 1600 m. To estimate the onset of normal faulting we combined high and medium temperature (U-Pb, Ar/Ar) and low temperature ((U-Th)/He) thermochronometry of the Kung Co pluton, a two-mica granite of the northern Himalayan granitic belt that outcrop in the footwall of the fault. Biotite and muscovite Ar/Ar ages , are close from each other [˜ 16 Ma ± 0.2 (Ms) and ˜ 15 ± 0.4 Ma (Bt)], which is typical of fast cooling. The zircon and apatite (U-Th)/He ages range from 11.3 to 9.6 Ma and 9.9 to 3.7 Ma respectively. These He ages are indicative of (1) fast initial cooling, from 11.3 to ˜ 9 Ma, gradually decreasing with time and (2) a high geothermal gradient (˜ 400 °C/km), close to the surface at ˜ 10 Ma. The Kung Co pluton was emplaced at about 22 Ma (U-Pb on zircon) at less than 10 km depth and 520-545 °C. Subsequent to its shallow emplacement, the pluton underwent fast thermal re-equilibration ending around 7.5 Ma, followed by a period of slow cooling caused either by the end of the thermal re-equilibration or by very slow exhumation (0.02-0.03 mm/yr) from ˜ 7.5 Ma to at least 4 Ma. In either case the data suggest that the exhumation rate increased after 4 Ma. We infer this increase to be related to the initiation of the Kung Co normal fault. A critical examination of previously published data show that most ˜ N-S Tibetan normal faults may have formed less than 5 Ma ago rather than in the Miocene as assumed by several authors. Such a young age implies that E-W extension is not related to the Neogene South Tibetan magmatism (25 to 8 Ma). Consequently, models relating E-W extension to magmatism, such as convective removal of the lower lithosphere, may be inappropriate

  7. Seychelles alkaline suite records the culmination of Deccan Traps continental flood volcanism (United States)

    Owen-Smith, T. M.; Ashwal, L. D.; Torsvik, T. H.; Ganerød, M.; Nebel, O.; Webb, S. J.; Werner, S. C.


    Silhouette and North Islands in the Seychelles represent an alkaline plutonic-volcanic complex, dated at 63 to 63.5 Ma by U-Pb zircon and 40Ar/39Ar methods. This magmatism coincides with the final stages of the cataclysmic Deccan Traps continental flood volcanism in India (67 to 63 Ma), and thus a causal link has been suggested. Recent reconstructions have placed the Seychelles islands adjacent to the Laxmi Ridge and at the western margin of the Réunion mantle plume at the time of formation of the complex. Here we present geochemical evidence in support of the notion that the Seychelles alkaline magmatism was initiated by the peripheral activity of the Réunion mantle plume and is thus part of the Deccan magmatic event. Positive εNd (0.59 to 3.76) and εHf (0.82 to 6.79) and initial Sr of 0.703507 to 0.705643 at 65 Ma indicate derivation of the Seychelles alkaline magmas from a Réunion-like mantle source with an additional minor enriched component, suggesting entrainment of sub-continental lithospheric mantle. The similarity in trace element composition between the Seychelles suite and Deccan alkaline felsic and mafic rocks provides additional evidence for a common mantle source for the Seychelles and Deccan magmatism. Furthermore, we demonstrate the role of fractional crystallisation in the evolution of the alkaline suite. Modelling using major elements suggests that fractional crystallisation and varying degrees of accumulation of olivine, plagioclase, ilmenite, clinopyroxene, alkali feldspar and apatite can describe the spectrum of rock types, from gabbro, through syenite, to granite.

  8. 80 Million Years of Prolonged and Localized Fluid flow on Shatsky Rise (United States)

    Vermillion, K. B.; Koppers, A.; Heaton, D. E.; Harris, R. N.


    Shatsky Rise is a large igneous province (LIP) in the northwest Pacific Ocean, which formed at an unstable ridge-ridge-ridge (RRR) triple junction at the Jurassic-Cretaceous boundary. High resolution 40Ar/39Ar incremental heating analyses of samples from TAMU and Ori Massif, the two largest volcanic features on Shatsky Rise, yield mixing ages between fresh plagioclase and sericite alteration phases. Mixing ages range from several million years younger to 75 Myr younger than the eruption ages of 147 (TAMU Massif) and 140 Ma (Ori Massif). Sericitic alteration in plagioclase from IODP (Integrated Ocean Drilling Program) Expedition 324 Holes U1347A, U1349A, U1350A and U1346A on TAMU, Ori and Shirshov Massifs suggests pervasive fluid flow throughout Shatsky Rise in the first million years after eruption. Sericitic alteration in plagioclase from ODP (Ocean Drilling Program) Hole 1231B on the flanks of the TAMU Massif also suggests fluid flow. However, localized and very late stage fluid flow is found in the deepest highly altered pillow basalt sequence (Unit IV) of IODP Hole U1350A, where sericitic plagioclase samples is dated to be 65.8, 70.2 and 82.1 Ma. Since the sericite 40Ar/39Ar ages obtained are a mixture between fresh plagioclase and sericite alteration in the plagioclase, we estimate the true age of alteration, using the Verati and Jourdan (Geological Society, London, 2015) mixing model, showing that in IODP Hole U1350A (140 Ma eruption age) the sericite formed around 127 Ma or much later between 85 and 60 Ma. Thermal modeling suggests that throughout Shatsky Rise sustained fluid flow may occur and could be responsible for sericite alteration up to approximately 22 Myr after eruption. During this initial Shatsky Rise cool down phase, the natural geothermal gradient remains high enough to form sericite at temperatures of 100-215 °C. However, the same model shows that the conductive geothermal gradient alone does not sustain enough heat to form sericite 80 Myr

  9. Compter mes jours : recherche explorant l'espace entre ma pratique artistique et ma pratique comptable


    Picard, Julie


    Cette recherche propose d’investiguer l’espace entre ma pratique artistique et ma pratique comptable à travers une approche qui déploie des activités de recherches théoriques sur l’art, des activités de recherches théoriques en comptabilité, la réalisation d’un protocole de création en atelier, et la prestation d’une conférence. L’approche flexible, multifocale et exploratoire adoptée se situe en affinité avec Intermedia, développé par Dick Higgins. Partant de ces deux figures type d’oppositi...

  10. Paleomagnetic constraints on early collisional deformation along the eastern margin of the Qiantang terrane (Tibetan plateau) at 50 and 37 Ma. (United States)

    Roperch, Pierrick; Dupont-Nivet, Guillaume; Guillot, Stéphane; Goussin, Fanny; Huang, Wentao; Replumaz, Anne; Yang, Zhang; Guo, Zhaojie; Song, Bowen


    Ongoing controversies on the timing and latitude of the India-Asia collision with associated formation of the Tibetan plateau have major implications on geodynamic, climatic and biotic models. Rock paleomagnetic inclinations and declinations enable in principle to quantify respectively paleolatitudes and tectonic rotations. However, shallow paleomagnetic inclinations observed for most of the Cenozoic rocks across the active belts of Central Asia have been controversially interpreted as resulting from non dipolar geomagnetic fields, inclination flattening in the sedimentary data or large scale continental deformation. In addition tectonic rotations from the Eastern margin of Tibet may result from extrusion or dextral shear associated with implication on the early collision. We present new paleomagnetic results from two Cenozoic basins of the Eastern part of the Qiantang block characterized by two short-lived volcanic fields at 37-38Ma (Nangqian area) and 49-51Ma (Xialaxiu area). In the Xialaxiu area, we sampled the volcanic field near the town of Xialaxiu and red beds filling the Sangalaxiu basin 10 to 20km farther north. Results from the red beds after tilt correction (D=328.3°, I=34.3°, α95=7.6°) confirm the result (D=322.0°, I=32.3°, α95=9.5°) previously obtained by Cogne et al., (1999) but the age and nature of the characteristic magnetization are uncertain. The mean direction calculated from 21 sites in volcanic rocks provides a more reliable paleofield (D=11.9°, I=41.6°, α95=8.0°). Comparison with the expected direction for stable Eurasia suggest no rotation but significant post 50 Ma shortening north of the Qiantang block in agreement with results from the Lhasa terrane at the same age (56-47 Ma) (van Hinsbergen et al., 2012). In the Nangqian basin, paleomagnetic sites have been collected in red beds sediments, sills and dikes intruding the red bed sequence and in extrusive volcanic rocks mainly found on top of the sedimentary sequence. A well

  11. Evidences for a volcanic province in the Central Indian Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Iyer, S.D.; Sudhakar, M.

    Based on various lines of evidence such as the widespread occurrence of basalts, pumice, volcanic glass shards and their transformational products (zeolites, palagonites, and smectite-rich sediments), we suggest the presence of a volcanic province...

  12. Reconsidering Volcanic Ocean Island Hydrology: Recent Geophysical and Drilling Results (United States)

    Thomas, D. M.; Pierce, H. A.; Lautze, N. C.


    Recent results of geophysical surveys and exploratory drilling in Hawaii have suggested that Hawaii's hydrogeology may be more complex than has been generally recognized. Instead of a more-or-less homogeneous pile of highly permeable eruptive basalts that are intermittently punctuated by volcanic dikes confined to calderas and rift zones, we are finding that dike compartmentalization is occurring outside of recognized rift zones, leading to significantly higher volumes of stored groundwater within the island. Analysis of recent geophysical surveys have shown local water table elevations that are substantially higher than can be accounted for by the high hydraulic conductivities of Hawaiian basalts. Recent diamond wireline drilling results have also shown that sub-horizontal variations in permeability, associated with significant changes in eruptive character (e.g. explosive vs effusive activity) are acting as significant perching and confining bodies over significant aerial extents and suggest that these features also contribute to increased storage of recharge. Not only is storage much higher than previously assumed, these features appear to impact subsurface groundwater flow in ways that are not accounted for in traditional methods of computing sustainable yields for near shore aquifers: where buried confining formations extend to depths well below sea level, higher elevation recharge is being intercepted and diverted to deep submarine groundwater discharge well below depths that are typically investigated or quantified. We will provide a summary of the recent geophysical survey results along with a revised conceptual model for groundwater circulation within volcanic ocean islands.

  13. Microgravity change as a precursor to volcanic activity (United States)

    Rymer, Hazel


    In recent decades, systematic microgravity studies over some 20 active volcanoes in Central America, Iceland, Italy, Japan, Papua New Guinea and the USA have provided valuable data on sub-surface mass redistribution associated with volcanic activity. Concurrent data on ground deformation are essential to the unambiguous interpretation of gravity changes. In some instances, gravity and elevation vary along the free-air or Bouguer gradients, implying that there has been no sub-surface mass or density change, respectively. Where there are residual gravity changes after correction for elevation changes, magma movements in sub-surface chambers, feeder systems, vents and fissures (dykes) or water table variations are proposed. Although detailed interpretations depend on local circumstances and the calculations depend on source geometry, in general, the smallest residual gravity changes are associated with eruptions from volatile-poor basaltic vents and at extensional rift zones, whereas the highest residual values occur at explosive, subduction-related stratocones built from volatile-rich andesitic magma. The most intriguing, yet difficult, data to interpret derive from large-volume, infrequently erupting volcanic systems where caldera unrest is now becoming well documented and the ultimate hazards are most severe. Mass increases during inflation followed by limited mass loss during subsequent deflation typify these structures.

  14. Investigating the Deep Seismic Structure of Volcan de Colima, Mexico (United States)

    Gardine, M. D.; Reyes, T. D.; West, M. E.


    We present early-stage results from a novel seismic investigation at Volcan de Colima. The project is a collaboration between the Observatorio Vulcanologico de la Universidad de Colima and the University of Alaska Fairbanks. In January 2006, twenty broadband seismometers were deployed in a wide-aperture array around the volcano as part of the IRIS/PASSCAL-supported Colima Volcano Deep Seismic Experiment (CODEX). They are scheduled to be in the field for eighteen months. Data from the first several months of the deployment have been used to characterize both the regional seismicity and the seismicity of the volcano, as recorded by the temporary array. Colima volcano has an unusually well-distributed suite of earthquakes on the local, regional and teleseismic scale. Data recorded close to the edifice provide an opportunity to explore the daily explosive activity exhibited by the volcano. The diversity of regional and teleseismic earthquake source regions make Colima an ideal place to probe the deep magmatic structure of a prodigous volcanic center. Results will be interpreted in the context of pre-existing petrologic models to address the relative role of crust and mantle in governing the evolution of an andesitic arc volcano.

  15. Volcanic gas impacts on vegetation at Turrialba Volcano, Costa Rica (United States)

    Teasdale, R.; Jenkins, M.; Pushnik, J.; Houpis, J. L.; Brown, D. L.


    Turrialba volcano is an active composite stratovolcano that is located approximately 40 km east of San Jose, Costa Rica. Seismic activity and degassing have increased since 2005, and gas compositions reflect further increased activity since 2007 peaking in January 2010 with a phreatic eruption. Gas fumes dispersed by trade winds toward the west, northwest, and southwest flanks of Turrialba volcano have caused significant vegetation kill zones, in areas important to local agriculture, including dairy pastures and potato fields, wildlife and human populations. In addition to extensive vegetative degradation is the potential for soil and water contamination and soil erosion. Summit fumarole temperatures have been measured over 200 degrees C and gas emissions are dominated by SO2; gas and vapor plumes reach up to 2 km (fumaroles and gases are measured regularly by OVSICORI-UNA). A recent network of passive air sampling, monitoring of water temperatures of hydrothermal systems, and soil pH measurements coupled with measurement of the physiological status of surrounding plants using gas exchange and fluorescence measurements to: (1) identify physiological correlations between leaf-level gas exchange and chlorophyll fluorescence measurements of plants under long term stress induced by the volcanic gas emissions, and (2) use measurements in tandem with remotely sensed reflectance-derived fluorescence ratio indices to track natural photo inhibition caused by volcanic gas emissions, for use in monitoring plant stress and photosynthetic function. Results may prove helpful in developing potential land management strategies to maintain the biological health of the area.

  16. Regulation of Banana Phytoene Synthase (MaPSY) Expression, Characterization and Their Modulation under Various Abiotic Stress Conditions (United States)

    Kaur, Navneet; Pandey, Ashutosh; Shivani; Kumar, Prateek; Pandey, Pankaj; Kesarwani, Atul K.; Mantri, Shrikant S.; Awasthi, Praveen; Tiwari, Siddharth


    Phytoene synthase (PSY) is a key regulatory enzyme of carotenoid biosynthesis pathway in plants. The present study examines the role of PSY in carotenogenesis and stress management in banana. Germplasm screening of 10 Indian cultivars showed that Nendran (3011.94 μg/100 g dry weight) and Rasthali (105.35 μg/100 g dry weight) contained the highest and lowest amounts of β-carotene, respectively in ripe fruit-pulp. Nendran ripe pulp also showed significantly higher antioxidant activity as compared to Rasthali. Meta-analysis of three banana PSY genes (MaPSY1, MaPSY2, and MaPSY3) was performed to identify their structural features, subcellular, and chromosomal localization in banana genome. The distinct expression patterns of MaPSY1, MaPSY2, and MaPSY3 genes were observed in various tissues, and fruit developmental stages of these two contrasting cultivars, suggesting differential regulation of the banana PSY genes. A positive correlation was observed between the expression of MaPSY1 and β-carotene accumulation in the ripe fruit-peel and pulp of Nendran. The presence of stress responsive cis-regulatory motifs in promoter region of MaPSY genes were correlated with the expression pattern during various stress (abscisic acid, methyl jasmonate, salicylic acid and dark) treatments. The positive modulation of MaPSY1 noticed under abiotic stresses suggested its role in plant physiological functions and defense response. The amino acid sequence analysis of the PSY proteins in contrasting cultivars revealed that all PSY comprises conserved domains related to enzyme activity. Bacterial complementation assay has validated the functional activity of six PSY proteins and among them PSY1 of Nendran (Nen-PSY1) gave the highest activity. These data provide new insights into the regulation of PSY expression in banana by developmental and stress related signals that can be explored in the banana improvement programs. PMID:28421096

  17. The geochemistry and tectonic setting of late Cretaceous Caribbean and Colombian volcanism (United States)

    Kerr, Andrew C.; Tarney, John; Marriner, Giselle F.; Nivia, Alvaro; Klaver, Gerard Th.; Saunders, Andrew D.


    Late Cretaceous mafic volcanic sequences in Western Colombia and in the southern Caribbean have a striking coherence in their chemistry and compositional range which suggests they are part of the same magmatic province. The chemical characteristics of the majority of the mafic lavas are totally unlike those of island arc or marginal basin basalts, so the sequences cannot represent accreted arc terranes. On the other hand their trace element characteristics closely resemble those of Icelandic/Reykjanes Ridge basalts that represent an oceanic plateau formed by extensive decompression melting of an uprising deep mantle plume. The occurrence of komatiites on Gorgona and high-MgO picritic lavas in S.E. Colombia and on Curaçao, representing high temperature melts of the plume tail, confirms this analogy. Likewise, late stage rhyolites within the Colombian mafic volcanics may well be the equivalent of the extensive silicic magmas on Iceland and at Galapagos, possibly formed by remelting of the deep parts of the overthickened basaltic crust above the plume head. These volcanics, plus others around the Caribbean, including the floor of the Central Caribbean, probably all represent part of an oceanic plateau that formed rapidly at the Galapagos hotspot at 88 Ma, and that was too hot and buoyant to subduct beneath the margin of S. America as it migrated westwards with the opening of the South Atlantic, and so was imbricated along the continental margin. Minor arc-like volcanics, tonalites and hornblende leucogabbro veins may represent the products of subduction-flip of normal ocean crust against the buoyant plateau, or hydrous melts developed during imbrication/obduction.

  18. Timing and composition of continental volcanism at Harrat Hutaymah, western Saudi Arabia (United States)

    Duncan, Robert A.; Kent, Adam J R; Thornber, Carl; Schliedler, Tyler D; Al-Amri, Abdullah M


    Harrat Hutaymah is an alkali basalt volcanic field in north-central Saudi Arabia, at the eastern margin of a large Neogene continental, intraplate magmatic province. Lava flow, tephra and spatter cone compositions in the field include alkali olivine basalts and basanites. These compositions contrast with the predominantly tholeiitic, fissure-fed basalts found along the eastern margin of the Red Sea. The Hutaymah lava flows were erupted through Proterozoic arc-associated plutonic and meta-sedimentary rocks of the Arabian shield, and commonly contain a range of sub-continental lithospheric xenoliths, although the lavas themselves show little indication of crustal contamination. Previous radiometric dating of this volcanic field (a single published K–Ar age; 1.8 Ma) is suspiciously old given the field measurement of normal magnetic polarity only (i.e. Brunhes interval, ≤ 780 Ka). We report new age determinations on 14 lava flows by the 40Ar–39Ar laser step heating method, all younger than ~ 850 Ka, to better constrain the time frame of volcanism, and major, trace and rare earth element compositions to describe the chemical variation of volcanic activity at Harrat Hutaymah. Crystal fractionation was dominated by olivine ± clinopyroxene at a range of upper mantle and crustal pressures. Rapid ascent and eruption of magma is indicated by the array of lower crustal and lithospheric xenoliths observed in lava flows and tephra. Modeling suggests 1–7% melting of an enriched asthenospheric mantle source occurred beneath Harrat Hutaymah under a relatively thick lithospheric cap (60–80 km).

  19. Possible Late Pleistocene volcanic activity on Nightingale Island, South Atlantic Ocean, based on geoelectrical resistivity measurements, sediment corings and 14C dating

    DEFF Research Database (Denmark)

    Bjørk, Anders Anker; Björck, Svante; Cronholm, Anders


    . The irregular shapes of the basins and the lack of clear erosional features indicate that they are not eruption craters and were not formed by erosion. Instead, we regard them as morphological depressions formed between ridges of trachytic lava flows and domes at a late stage of the formation of the volcanic...... edifice. The onset of sedimentation within these basins appears to have occurred between 24 and 37 ka with the highest situated wetland yielding the highest ages. These ages are very young compared to the timing of the main phase of the formation of the island, implying volcanic activity on the island......Tristan da Cunha is a volcanic island group situated in the central South Atlantic. The oldest of these islands, Nightingale Island, has an age of about 18Ma. In the interior of the island, there are several wetlands situated in topographic depressions. The ages of these basins have been unknown...

  20. 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

  1. Geochemical, petrographic and physical characterizations and associated alterations of the volcanic rocks of the Romanesque San Nicola Church (Ottana, central Sardinia, Italy) (United States)

    Columbu, Stefano; Palomba, Marcella; Sitzia, Fabio


    In this research, the volcanic rocks belonging to the Sardinia Oligo-Miocene volcanic cycle (32 - 11 Ma) and building up the structure of the San Nicola church, one of the most representative churches of the Romanesque architecture, were studied. These stones were widely used in medieval architecture for the excellent workability, but they present some disadvantages, since they are greatly affected by alteration phenomena. The main objectives of this research are i) to focus the mineral, chemical and petrographic compositions of the San Nicola stones, ii) the chemical and physical alteration processes affecting these materials, and iii) to establish the exactly provenance of the volcanic rocks. Furthermore, a comparative study between the rocks from the ancient quarries and those forming the structure of the church was performed. In the ancient quarries, where presumably a more advanced alteration occurs due to the vertical alteration gradient, different facies of the same volcanic lithology, characterized by macroscopical evidences of chemical-physical degradation degree, were sampled. Petrographic, geochemical (both major elements that the traces) and physical-mechanical features of the collected samples were determined to highlight the compositional differences (density, porosity, water-absorption kinetics, mechanical resistance) as a function of the different alteration degree. Moreover, chemical-mineralogical analysis of the sample surfaces from the church, was performed, to highlight possible presence and nature of secondary newly-formed phases (e.g., salt efflorescence). Several methodologies were applied to carry out physical-chemical and petrographic analysis: X-Ray fluorescence (XRF) and Inductively Coupled Mass Spectrometry (ICP-MS), X-Ray Diffractometry (XRD) for chemical and mineral composition; Optical and Scanning Electron Microscopy (SEM) for textures, mineral assemblages and microstructures studies; He-picnometry, water-absorption and mechanical

  2. Changing the S and MA [Safety and Mission Assurance] Paradigm (United States)

    Malone, Roy W., Jr.


    Objectives: 1) Optimize S&MA organization to best facilitate Shuttle transition in 2010, successfully support Ares developmental responsibilities, and minimize the impacts of the gap between last Shuttle flight and start of Ares V Project. 2) Improve leveraging of critical skills and experience between Shuttle and Ares. 3) Split technical and supervisory functions to facilitate technical penetration. 4) Create Chief Safety and Mission Assurance Officer (CSO) stand-alone position for successfully implementation of S&MA Technical Authority. 5) Minimize disruption to customers. 6) Provide early involvement of S&MA leadership team and frequent/open communications with S&MA team members and steak-holders.

  3. Petrography, Geochemistry and Petrogenesis of Volcanic Rocks, NW Ghonabad, Iran

    Directory of Open Access Journals (Sweden)

    Sedigheh Zirjanizadeh


    .6mmin size. Trachyte is characterized by trachytic texture. Ninety percent of the rock consists of sanidine. In trachytes, 3 to 5% hornblende ( 0.3 mm is replaced by carbonates. Rhyolites contain quartz, plagioclase, sanidine, and biotite phenocrysts in a microcrystalline to glassy groundmass. Rhyodacitehas phenocrysts, some glomerophyric, consisting of quartz, 2 to 3% (0.1-0.5 mm, plagioclase 7 to 10% (0.2- 0.8 mm, hornblende 5% and biotite 1%. Up to 15% of sanidineis altered to clay minerals. Crystal tuff and lithic-crystal tuff are distributed overa large area. Using the Zr/TiO2 and Nb/Y diagram of Winchester and Fold (1977, samples are designated as rhyolite, dacite and sub-alkaline basalt. In the Co vs. Th diagram of Hastie et al. (2007, samples plot in the shoshonitic and high calc-alkaline, rhyolite, dacite and andesite-basalt fields. The REE patterns and trace element contents of the volcanic samples show: (1 LREE/HREE enrichment ((La/Yb N = 0.3 to 15.27, (2 Low negative Eu anomaly (ave.Eu*/Eu=0.2-0.85, (3 depletion in Ba, Sr, K2O, Zr and Ti (Lower continental crust-normalized spider diagram from Taylor and McLennan, 1985 and Chondrite-normalized diagram from Nakamura, 1974. Rhyolites show the most extreme negative Eu anomaly (Eu/Eu* = 0.2-0.3 compared with 0.65–0.85 for volcanic elsewhere and also show considerably differences in the contents of Rb,Sr,K,Ti,Zr,Hf,Ce. These differences are related to greater magmatic differentiation or derivation from the other sources. The Sr and Nd isotopic ratios of these volcanic rocks are: 87Sr/86Sr = 0.70699 to 0.71014 and 143Nd/144Nd =0.512144 to 0.512539. Assuming an age of 60 Ma, the initial 87Sr/86Sr ratios vary from 0.70671 to 0.71066 and initial 143Nd/144Nd values vary from 0.512098 0.51249 (εNdi = -9.1 to 0.51249 (εNdi = -1.4.In the εNdi versus (87Sr/86Sri diagram, the samples plot in the field typical of magmas that are of crustal origin or, at least, that underwent important processes of crustal assimilation

  4. Commercial helium reserves, continental rifting and volcanism (United States)

    Ballentine, C. J.; Barry, P. H.; Hillegonds, D.; Fontijn, K.; Bluett, J.; Abraham-James, T.; Danabalan, D.; Gluyas, J.; Brennwald, M. S.; Pluess, B.; Seneshens, D.; Sherwood Lollar, B.


    Helium has many industrial applications, but notably provides the unique cooling medium for superconducting magnets in medical MRI scanners and high energy beam lines. In 2013 the global supply chainfailed to meet demand causing significant concern - the `Liquid Helium Crisis' [1]. The 2017 closure of Quatar borders, a major helium supplier, is likely to further disrupt helium supply, and accentuates the urgent need to diversify supply. Helium is found in very few natural gas reservoirs that have focused 4He produced by the dispersed decay (a-particle) of U and Th in the crust. We show here, using the example of the Rukwa section of the Tanzanian East African Rift, how continental rifting and local volcanism provides the combination of processes required to generate helium reserves. The ancient continental crust provides the source of 4He. Rifting and associated magmatism provides the tectonic and thermal mechanism to mobilise deep fluid circulation, focusing flow to the near surface along major basement faults. Helium-rich springs in the Tanzanian Great Rift Valley were first identified in the 1950's[2]. The isotopic compositions and major element chemistry of the gases from springs and seeps are consistent with their release from the crystalline basement during rifting [3]. Within the Rukwa Rift Valley, helium seeps occur in the vicinity of trapping structures that have the potential to store significant reserves of helium [3]. Soil gas surveys over 6 prospective trapping structures (1m depth, n=1486) show helium anomalies in 5 out of the 6 at levels similar to those observed over a known helium-rich gas reservoir at 1200m depth (7% He - Harley Dome, Utah). Detailed macroseep gas compositions collected over two days (n=17) at one site allows us to distinguish shallow gas contributions and shows the deep gas to contain between 8-10% helium, significantly increasing resource estimates based on uncorrected values (1.8-4.2%)[2,3]. The remainder of the deep gas is

  5. Anti-Ma2-antibody-associated encephalitis: An atypical paraneoplastic neurologic syndrome

    Directory of Open Access Journals (Sweden)

    Bogna Targonska


    Full Text Available Paraneoplastic syndromes are a heterogeneous group of conditions affecting cancer patients, where the signs and symptoms are not owing to the local effects of the tumour but instead owing to humoral or immunologic effects. We describe an unusual presentation of a paraneoplastic neurologic syndrome presenting with predominant involvement of the hypothalamus and deep grey nuclei secondary to an anterior mediastinal germinoma and associated with anti-Ma2 antibody.

  6. Rapid uplift in Laguna del Maule volcanic field of the Andean Southern Volcanic Zone (Chile) measured by satellite radar interferometry (United States)

    Feigl, K.; Ali, T.; Singer, B. S.; Pesicek, J. D.; Thurber, C. H.; Jicha, B. R.; Lara, L. E.; Hildreth, E. W.; Fierstein, J.; Williams-Jones, G.; Unsworth, M. J.; Keranen, K. M.


    The Laguna del Maule (LdM) volcanic field of the Andean Southern Volcanic Zone extends over 500 square kilometers and comprises more than 130 individual vents. As described by Hildreth et al. (2010), the history has been defined from sixty-eight Ar/Ar and K-Ar dates. Silicic eruptions have occurred throughout the past 3.7 Ma, including welded ignimbrite associated with caldera formation at 950 ka, small rhyolitic eruptions between 336 and 38 ka, and a culminating ring of 36 post-glacial rhyodacite and rhyolite coulees and domes that encircle the lake. Dating of five post-glacial flows implies that these silicic eruptions occurred within the last 25 kyr. Field relations indicate that initial eruptions comprised modest volumes of mafic rhyodacite magma that were followed by larger volumes of high silica rhyolite. The post-glacial flare-up of silicic magmatism from vents distributed around the lake, is unprecedented in the history of this volcanic field. Using satellite radar interferometry (InSAR), Fournier et al. (2010) measured uplift at a rate of more than 180 mm/year between 2007 and 2008 in a round pattern centered on the west side of LdM. More recent InSAR observations suggest that rapid uplift has continued from 2008 through early 2011. In contrast, Fournier et al. found no measurable deformation in an interferogram spanning 2003 through 2004. In this study, we model the deformation field using the General Inversion of Phase Technique (GIPhT), as described by Feigl and Thurber (2009). Two different models fit the data. The first model assumes a sill at ~5 km depth has been inflating at a rate of more than 20 million cubic meters per year since 2007. The second model assumes that the water level in the lake dropped at a rate of 20 m/yr from January 2007 through February 2010, thus reducing the load on an elastic simulation of the crust. The rate of intrusion inferred from InSAR is an order of magnitude higher than the average rate derived from well-dated arc

  7. Geochemical and Petrologic Constraints on the Source of Eocene Volcanism at Mole Hill, Rockingham County, VA (United States)

    Johnson, E. A.; Beard, J. S.


    Mole Hill is an Eocene (48 Ma) basaltic volcanic neck located west of Harrisonburg, VA, and provides a unique opportunity to probe the mantle beneath the Shenandoah Valley. It lies on the northeastern edge of a swarm of alkaline-series volcanic plugs, dikes, and diatremes extending through Rockingham and Highland Counties, VA, and Pendleton County, WV. The Eocene volcanics are thought to have exploited extensive basement fracture systems originally formed during the Alleghenian Orogeny and subsequent rifting. The Eocene volcanism may have been triggered by reactivation of faults due to global shifts in relative plate motions (Southworth 1993, USGS Bull, B1839-I) but the source material and magmatic processes for the Eocene volcanism are largely unknown. Compositional and texture analyses of xenocrystic and groundmass clinopyroxene, olivine, and spinel were completed either at Virginia Tech on the Cameca SX-50 electron microprobe in the Dept of Geological Sciences, or in the Dept of Mineral Sciences, Smithsonian Institution, Washington, D.C using the JEOL JXA-8900R WD/EDS microanalyzer or the FEI NOVA nanoSEM600 FEG Variable Pressure Scanning Electron Microscope. Xenocrysts up to 2cm in diameter are distributed throughout the volcanic neck, with clinopyroxene >>spinel>olivine. The clinopyroxene and olivine xenocrysts show undulatory extinction in cross-polarized light and are found as individual crystals or as aggregates. Clinopyroxene xenocryst cores are high-Al, low-Cr augite ( ˜Wo44En46Fs10) with Mg# 78.5-85.9. The clinopyroxene xenocrysts have compositionally zoned rims 100-250 μm-wide containing abundant plagioclase inclusions and sparse melt inclusions in a sieve texture. The outer edges of xenocrysts approach the compositions of groundmass and microphenocryst clinopyroxenes ( ˜Wo47En38Fs15; Mg# 67.9-74.5). Olivine xenocrysts contain sulfide inclusions and Cr-rich spinel and have Mg-rich ( ˜Fo86-90) cores with more Fe- and Ca-rich rims (Fo70

  8. O azarado Macunaíma

    Directory of Open Access Journals (Sweden)

    Priscila Figueiredo

    Full Text Available Resumo Qual o sentido dos infortúnios sucessivos de Macunaíma, sobretudo nos capítulos finais, quando, de posse do amuleto da sorte, nem por isso esta lhe sobrevém, mas ao contrário segue-se um processo cada vez mais acelerado de degradação entrópica? Umas das finalidades do artigo é mostrar, por um lado, o caiporismo do personagem como repetição estrutural, desenvolvido no âmbito da "morfologia da história" captada pelo livro, e, por outro, como esse azar permanente funciona como significante mítico de um permanente desamparo. Nesse sentido, o personagem é compreendido como uma síntese das experiências do vasto setor da população brasileira que Caio Prado Jr. chamou de inorgânico. Tal interpretação tem consequências para pensar a inadvertida mimese do real operada pela obra e a relação com a noção de progresso aí sugerida.

  9. Improving volcanic ash forecasts with ensemble-based data assimilation

    NARCIS (Netherlands)

    Fu, Guangliang


    The 2010 Eyjafjallajökull volcano eruption had serious consequences to civil aviation. This has initiated a lot of research on volcanic ash forecasting in recent years. For forecasting the volcanic ash transport after eruption onset, a volcanic ash transport and diffusion model (VATDM) needs to be

  10. Volcanic Characteristics of Kueishantao in Northeast Taiwan and Their Implications

    Directory of Open Access Journals (Sweden)

    Ching-Lung Chiu


    Full Text Available Kueishantao (KST is a small offshore volcanic island located at the southernmost part of the Okinawa Trough. In this study, we conducted a detailed mapping incorporating the new high resolution LiDAR DTM laser scanning device to accurately construct a volcanic sequence. A new 1/5000 geological map was established. One primary volcanic cone, composed of layers of both lava flows and pyroclastic rocks constituted the major edifice of KST. The other minor volcanic cone, which consists of volcanic lapillis and blocks, is seated to the east of the main cone. The escarped and nearly straight coast in the southern part of the KST indicates that the volcano suffered a large post-volcanic edifice collapse erasing nearly one half of the volume of both volcanic cones. The increase in the abundance of the xenoliths of sedimentary rocks from the lower to the upper part of the volcanic sequence indicates that the formation of volcanic rocks of the KST involved an intensification of crustal contamination. The possibility of volcanic eruption can not be excluded in the future based on the present thermolu¬minescene age data of 7 ka. The associated eruptive ash fall and tsunami induced by the further collapse of the KST volcanic edifice might have great influence to the adjacent inland. Thus, long-term monitoring of volcanic activities around KST should be required for future hazard assessments.

  11. Apollo 15 mare volcanism: constraints and problems

    International Nuclear Information System (INIS)

    Delano, J.W.


    The Apollo 15 landing site contains more volcanics in the form of crystalline basalts and pristine glasses, which form the framework for all models dealing with the mantle beneath that site. Major issues on the petrology of the mare source regions beneath that portion of Mare Imbrium are summarized

  12. Monogenetic volcanism: personal views and discussion (United States)

    Németh, K.; Kereszturi, G.


    Monogenetic volcanism produces small-volume volcanoes with a wide range of eruptive styles, lithological features and geomorphic architectures. They are classified as spatter cones, scoria (or cinder) cones, tuff rings, maars (maar-diatremes) and tuff cones based on the magma/water ratio, dominant eruption styles and their typical surface morphotypes. The common interplay between internal, such as the physical-chemical characteristics of magma, and external parameters, such as groundwater flow, substrate characteristics or topography, plays an important role in creating small-volume volcanoes with diverse architectures, which can give the impression of complexity and of similarities to large-volume polygenetic volcanoes. In spite of this volcanic facies complexity, we defend the term "monogenetic volcano" and highlight the term's value, especially to express volcano morphotypes. This study defines a monogenetic volcano, a volcanic edifice with a small cumulative volume (typically ≤1 km3) that has been built up by one continuous, or many discontinuous, small eruptions fed from one or multiple magma batches. This definition provides a reasonable explanation of the recently recognized chemical diversities of this type of volcanism.

  13. Payenia volcanic province, southern Mendoza, Argentina

    DEFF Research Database (Denmark)

    Søager, Nina; Holm, Paul Martin; Llambias, Eduardo Jorge


    The Pleistocene to Holocene Payenia volcanic province is a backarc region of 60,000 km2 in Mendoza, Argentina, which is dominated by transitional to alkaline basalts and trachybasalts. We present major and trace element compositions of 139 rocks from this area of which the majority are basaltic...

  14. Monitoring and forecasting Etna volcanic plumes

    Directory of Open Access Journals (Sweden)

    S. Scollo


    Full Text Available In this paper we describe the results of a project ongoing at the Istituto Nazionale di Geofisica e Vulcanologia (INGV. The objective is to develop and implement a system for monitoring and forecasting volcanic plumes of Etna. Monitoring is based at present by multispectral infrared measurements from the Spin Enhanced Visible and Infrared Imager on board the Meteosat Second Generation geosynchronous satellite, visual and thermal cameras, and three radar disdrometers able to detect ash dispersal and fallout. Forecasting is performed by using automatic procedures for: i downloading weather forecast data from meteorological mesoscale models; ii running models of tephra dispersal, iii plotting hazard maps of volcanic ash dispersal and deposition for certain scenarios and, iv publishing the results on a web-site dedicated to the Italian Civil Protection. Simulations are based on eruptive scenarios obtained by analysing field data collected after the end of recent Etna eruptions. Forecasting is, hence, supported by plume observations carried out by the monitoring system. The system was tested on some explosive events occurred during 2006 and 2007 successfully. The potentiality use of monitoring and forecasting Etna volcanic plumes, in a way to prevent threats to aviation from volcanic ash, is finally discussed.

  15. X-ray microanalysis of volcanic ash

    International Nuclear Information System (INIS)

    Kearns, S L; Buse, B


    The 2010 eruption of Eyjafjallajökull volcano in Iceland demonstrated the disruptive nature of high-level volcanic ash emissions to the world's air traffic. The chemistry of volcanic material is complex and varied. Different eruptions yield both compositional and morphological variation. Equally a single eruption, such as that in Iceland will evolve over time and may potentially produce a range of volcanic products of varying composition and morphology. This variability offers the petrologist the opportunity to derive a tracer to the origins both spatially and temporally of a single particle by means of electron microbeam analysis. EPMA of volcanic ash is now an established technique for this type of analysis as used in tephrachronology. However, airborne paniculate material may, as in the case of Eyjafjallajökull, result in a particle size that is too small and too dispersed for preparation of standard EPMA mounts. Consequently SEM-EDS techniques are preferred for this type of quantitative analysis . Results of quantitative SEM-EDS analysis yield data with a larger precision error than EPMA yet sufficient to source the original eruption. Uncoated samples analyzed using variable pressure SEM yield slightly poorer results at modest pressures.

  16. Amazonian volcanism inside Valles Marineris on Mars

    Czech Academy of Sciences Publication Activity Database

    Brož, Petr; Hauber, E.; Wray, J. J.; Michael, G.


    Roč. 473, September (2017), s. 122-130 ISSN 0012-821X Institutional support: RVO:67985530 Keywords : Mars * Valles Marineris * volcanism * scoria cone * hydrothermal activity Subject RIV: DC - Siesmology, Volcanology, Earth Structure OBOR OECD: Volcanology Impact factor: 4.409, year: 2016

  17. The Elusive Evidence of Volcanic Lightning. (United States)

    Genareau, K; Gharghabi, P; Gafford, J; Mazzola, M


    Lightning strikes are known to morphologically alter and chemically reduce geologic formations and deposits, forming fulgurites. A similar process occurs as the result of volcanic lightning discharge, when airborne volcanic ash is transformed into lightning-induced volcanic spherules (LIVS). Here, we adapt the calculations used in previous studies of lightning-induced damage to infrastructure materials to determine the effects on pseudo-ash samples of simplified composition. Using laboratory high-current impulse experiments, this research shows that within the lightning discharge channel there is an ideal melting zone that represents roughly 10% or less of the total channel radius at which temperatures are sufficient to melt the ash, regardless of peak current. The melted ash is simultaneously expelled from the channel by the heated, expanding air, permitting particles to cool during atmospheric transport before coming to rest in ash fall deposits. The limited size of this ideal melting zone explains the low number of LIVS typically observed in volcanic ash despite the frequent occurrence of lightning during explosive eruptions.

  18. The structure environment, rock-magma system, mineral-forming series and pattern of volcanic mineral-forming of uranium deposit in southeast of China

    International Nuclear Information System (INIS)

    Yu Dagan


    The Volcanic uranium deposit of rock-magma belt-the Mid-Cz Volcano in the Southeast of China mainly formed around 120 ∼ 130 Ma and 90 ∼ 100 Ma Which is in harmony with the two rock magma activities of k within the region. The rock-magma system of this period formed around the turning period from pressure to tension in the continent margin of southeast China, which is mainly characterized by the appearance of A-type granite and alkaline, sub-alkaline rocks (trachyte, trachyandensite, trachybasalt, basic rock alkaline basalt). The uranium deposit is controlled by the base rift of dissection to the mantle, the volcanic basin is of the double characteristics of transversal rift valley basin (early period) ad tension rift valley basin (laster period). The leading role of the deep source is stressed in terms of internal-forming series of volcanic uranium deposits is considered to exist; and also in terms of internal-forming series of volcanic uranium deposits is considered to exist; and also in terms of mineral-forming patterns, the multi-pattern led by the deep-source is stressed, including the mineral-forming pattern of uranium deposit of continental thermos, repeated periphery mineral-forming pattern of uranium deposit and the mineral-forming pattern of uranium deposit of rising pole-like thermos. Ten suggestions are put forward to the next mineral-search according to the above thoughts

  19. Sources of Quaternary volcanism in the Itasy and Ankaratra volcanic fields, Madagascar (United States)

    Rasoazanamparany, C.; Widom, E.; Kuentz, D. C.; Raharimahefa, T.; Rakotondrazafy, F. M. A.; Rakotondravelo, K. M.


    We present new major and trace element and Sr, Nd, Pb and Os isotope data for Quaternary basaltic lavas and tephra from the Itasy and Ankaratra volcanic fields, representing the most recent volcanism in Madagascar. Mafic magmas from Itasy and Ankaratra exhibit significant inter- and intra-volcanic field geochemical heterogeneity. The Itasy eruptive products range in composition from foidite to phonotephrite whereas Ankaratra lavas range from basanite to trachybasalts. Trace element signatures of samples from both volcanic fields are very similar to those of ocean island basalts (OIB), with significant enrichment in Nb and Ta, depletion in Rb, Cs, and K, and relatively high Nb/U and Ce/Pb. However, the Itasy volcanic rocks show enrichment relative to those of Ankaratra in most incompatible elements, indicative of a more enriched source and/or lower degrees of partial melting. Significant inter- and intra-volcanic field heterogeneity is also observed in Sr, Nd, Pb and Os isotope signatures. The Itasy volcanic rocks generally have less radiogenic Sr and Nd isotopic ratios but more radiogenic Pb isotopic signatures than the Ankaratra volcanic field. Together, the Itasy and Ankaratra volcanic rocks form a well-defined negative correlation in Sr vs. Pb isotopes that could be attributed to lithospheric contamination or variable degrees of mixing between distinct mantle sources. However, the lack of correlation between isotopes and indices of crustal contamination (e.g. MgO and Nb/U) are inconsistent with shallow lithospheric contamination, and instead suggest mixing between compositionally distinct mantle sources. Furthermore, although Sr-Pb isotope systematics are apparently consistent with mixing between two different sources, distinct trends in Sr vs. Nd isotopes displayed by samples from Itasy and Ankaratra, respectively, argue for more complex source mixing involving three or more sources. The current data demonstrate that although the Itasy and Ankaratra volcanic

  20. Microphysical Properties of Alaskan Volcanic Ash (United States)

    Puthukkudy, A.; Espinosa, R.; Rocha Lima, A.; Remer, L.; Colarco, P. R.; Whelley, P.; Krotkov, N. A.; Young, K.; Dubovik, O.; Wallace, K.; Martins, J. V.


    Volcanic ash has the potential to cause a variety of severe problems for human health and the environment. Therefore, effective monitoring of the dispersion and fallout from volcanic ash clouds and characterization of the aerosol particle properties are essential. One way to acquire information from volcanic clouds is through satellite remote sensing: such images have greater coverage than ground-based observations and can present a "big picture" perspective. A challenge of remote sensing is that assumptions of certain properties of the target are often a pre-requisite for making accurate and quantitative retrievals. For example, detailed information about size distribution, sphericity, and optical properties of the constituent matter is needed or must be assumed. The same kind of information is also needed for atmospheric transport models to properly simulate the dispersion and fallout of volcanic ash. Presented here is a laboratory method to determine the microphysical and optical properties of volcanic ash samples collected from two Alaskan volcanoes with markedly different compositions. Our method uses a Polarized Imaging Nephelometer (PI-Neph) and a system that re-suspends the particles in an air flow. The PI-Neph measures angular light scattering and polarization of the re-suspended particles from 3o to 175o in scattering angle, with an angular resolution of 1o . Primary measurements include phase function and polarized phase function at three wavelengths (445nm, 532nm, and 661nm). Size distribution, sphericity, and complex refractive index are retrieved indirectly from the PI-Neph measurements using the GRASP (Generalized Retrieval of Aerosol and Surface Properties) inversion algorithm. We report the results of this method applied to samples from the Mt. Okmok (2008) and Mt. Katmai (1912) volcanic eruptions. To our knowledge, this is the first time direct measurements of phase matrix elements of ash from Mt. Okmok and Mt. Katmai have been reported. Retrieved

  1. Fluids in volcanic and geothermal systems (United States)

    Sigvaldason, Gudmundur E.

    Mineral buffers control the composition of most volatile components of magmas and dissolved species in geothermal fluids. The only element which occurs in significant quantities in volcanic and geothermal fluids and is not controlled by mineral buffers is chlorine. It is argued that in absence of marine influence, geothermal fluids reflect the chlorine content of associated magmatic fluids. The chlorine content of oceanic volcanic rocks has a positive correlation with elements, which are believed to indicate a heterogenous source region. Since the source is generally believed to be the Earth's mantle, the implication is that the mantle is heterogenous with regard to chlorine and other volatiles. Such heterogeneities would have important consequences for genesis and distribution of ore. All major magma types of the oceanic environment occur in Iceland. Their spatial distribution is closely related to a volcanotectonic pattern, suggesting crustal control. A geophysical model of crustal accretion in a rift zone is used in conjunction with classical petrology to predict geochemical processes in a rift zone crust. The model has two kinematic parameters-drift rate and subsidence rate-which combined describe trajectories of mass particles deposited on the surface. When considering in conjunction with thermal gradients of the rift zone a series of metamorphic reactions and chemical fractionation processes are bound to occur, eventually resulting in a layering of the oceanic crust. The physical parameters result in a derived variable, rift zone residence time, which depends on the width of a rift zone. Long residence times in a wide rift zone lead to multistage recycling of material. Other properties of the model, based on geometric arrangement of productive fissure swarms within a rift zone, explain off-rift volcanism as directly related to rift zone processes, either as plate trapped magmatic domains or a transgressive thermal anomaly into an older crust. Off

  2. WOVOdat: A New Tool for Managing and Accessing Data of Worldwide Volcanic Unrest (United States)

    Venezky, D. Y.; Malone, S. D.; Newhall, C. G.


    WOVOdat (World Organization of Volcano Observatories database of volcanic unrest) will for the first time bring together data of worldwide volcanic seismicity, ground deformation, fumarolic activity, and other changes within or adjacent to a volcanic system. Although a large body of data and experience has been built over the past century, currently, we have no means of accessing that collective experience for use during crises and for research. WOVOdat will be the central resource of a data management system; other components will include utilities for data input and archiving, structured data retrieval, and data mining; educational modules; and links to institutional databases such as IRIS (global seismicity), UNAVCO (global GPS coordinates and strain vectors), and Smithsonian's Global Volcanism Program (historical eruptions). Data will be geospatially and time-referenced, to provide four dimensional images of how volcanic systems respond to magma intrusion, regional strain, and other disturbances prior to and during eruption. As part of the design phase, a small WOVOdat team is currently collecting information from observatories about their data types, formats, and local data management. The database schema is being designed such that responses to common, yet complex, queries are rapid (e.g., where else has similar unrest occurred and what was the outcome?) while also allowing for more detailed research analysis of relationships between various parameters (e.g., what do temporal relations between long-period earthquakes, transient deformation, and spikes in gas emission tell us about the geometry and physical properties of magma and a volcanic edifice?). We are excited by the potential of WOVOdat, and we invite participation in its design and development. Next steps involve formalizing and testing the design, and, developing utilities for translating data of various formats into common formats. The large job of populating the database will follow, and eventually

  3. Quantifying Volcanic Emissions of Trace Elements to the Atmosphere: Ideas Based on Past Studies (United States)

    Rose, W. I.


    Extensive data exist from volcanological and geochemical studies about exotic elemental enrichments in volcanic emissions to the atmosphere but quantitative data are quite rare. Advanced, highly sensitive techniques of analysis are needed to detect low concentrations of some minor elements, especially during major eruptions. I will present data from studies done during low levels of activity (incrustations and silica tube sublimates at high temperature fumaroles, from SEM studies of particle samples collected in volcanic plumes and volcanic clouds, from geochemical analysis of volcanic gas condensates, from analysis of treated particle and gas filter packs) and a much smaller number that could reflect explosive activity (from fresh ashfall leachate geochemistry, and from thermodynamic codes modeling volatile emissions from magma). This data describes a highly variable pattern of elemental enrichments which are difficult to quantify, generalize and understand. Sampling in a routine way is difficult, and work in active craters has heightened our awareness of danger, which appropriately inhibits some sampling. There are numerous localized enrichments of minor elements that can be documented and others can be expected or inferred. There is a lack of systematic tools to measure minor element abundances in volcanic emissions. The careful combination of several methodologies listed above for the same volcanic vents can provide redundant data on multiple elements which could lead to overall quantification of minor element fluxes but there are challenging issues about detection. For quiescent plumes we can design combinations of measurements to quantify minor element emission rates. Doing a comparable methodology to succeed in measuring minor element fluxes for significant eruptions will require new strategies and/or ideas.

  4. Volcanic geology and geochemistry of Motuhora (Whale Island), Bay of Plenty, New Zealand

    International Nuclear Information System (INIS)

    Burt, R.M.; Cole, J.W.; Vroon, P.Z.


    Motuhora (Whale Island) lies c. 11 km offshore from Whakatane in the Bay of Plenty, New Zealand, and comprises tuffaceous marine sediments of the Camp Bay and Motuhora Formations separated by lavas, volcanic breccias, and slope-wash deposits of the Whale Volcanics. Whale Volcanics can be divided into East Dome, Central Dome Complex, and Pa Hill Dome. East Dome is a flow banded, chaotically jointed dacite that is probably extrusive. Central Dome comprises lava flows, and extensive volcanic breccias and tuffs which thicken into a local depression to the north of the central high, suggesting rapid growth and erosion of the dome. Pa Hill Dome is largely intrusive into Camp Bay Formation, although blocks of Pa Hill dacite in an upper slope-wash cobble bed suggest it was partially extrusive. The lavas are porphyritic with phenocrysts of plagioclase, orthopyroxene, and titanomagnetite with subordinate clinopyroxene and amphibole (particularly in Pa Hill Dome), and rare biotite. Rounded or broken and embayed quartz crystals are found in the Central Dome Complex and Pa Hill domes. Magmatic xenoliths are common in all lavas. Chemically the lavas are medium-K, calc-alkaline andesites and dacites, and show relative LILE enrichment and HFSE depletion typical of arc volcanics. Isotopically, samples tend to have more radiogenic Sr and less radiogenic Nd than volcanics from neighbouring White Island. It is likely that Motuhora lavas were formed by a multi-stage process involving partial melting of N-MORB-type mantle that had been fluxed by fluids rich in incompatible elements derived from the dehydrating downgoing slab and followed by crystal fractionation of the magma. As the magma rose through the lower continental crust it was contaminated, probably by Torlesse metasediment. Petrographic textures and mineral chemistry indicate that magma mixing, while in an upper crustal magma chamber, is the norm for Motuhora lavas. (author). 69 refs., 12 figs., 2 tabs

  5. Abstracts for the October 2012 meeting on Volcanism in the American Southwest, Flagstaff, Arizona (United States)

    Lowenstern, Jacob B.


    Though volcanic eruptions are comparatively rare in the American Southwest, the States of Arizona, Colorado, New Mexico, Nevada, and Utah host Holocene volcanic eruption deposits and are vulnerable to future volcanic activity. Compared with other parts of the western United States, comparatively little research has been focused on this area, and eruption probabilities are poorly constrained. Monitoring infrastructure consists of a variety of local seismic networks, and ”backbone“ geodetic networks with little integration. Emergency response planning for volcanic unrest has received little attention by either Federal or State agencies. On October 18–20, 2012, 90 people met at the U.S. Geological Survey campus in Flagstaff, Arizona, providing an opportunity for volcanologists, land managers, and emergency responders to meet, converse, and begin to plan protocols for any future activity. Geologists contributed data on recent findings of eruptive ages, eruption probabilities, and hazards extents (plume heights, ash dispersal). Geophysicists discussed evidence for magma intrusions from seismic, geodetic, and other geophysical techniques. Network operators publicized their recent work and the relevance of their equipment to volcanic regions. Land managers and emergency responders shared their experiences with emergency planning for earthquakes. The meeting was organized out of the recognition that little attention had been paid to planning for or mitigation of volcanic hazards in the American Southwest. Moreover, few geological meetings have hosted a session specifically devoted to this topic. This volume represents one official outcome of the meeting—a collection of abstracts related to talks and poster presentations shared during the first two days of the meeting. In addition, this report includes the meeting agenda as a record of the proceedings. One additional intended outcome will be greater discussion and coordination among emergency responders, geologists

  6. Pacific seamount volcanism in space and time (United States)

    Hillier, J. K.


    Seamounts constitute some of the most direct evidence about intraplate volcanism. As such, when seamounts formed and into which tectonic setting they erupted (i.e. on-ridge or off-ridge) are a useful reflection of how the properties of the lithosphere interact with magma generation in the fluid mantle beneath. Proportionately few seamounts are radiometrically dated however, and these tend to be recently active. In order to more representatively sample and better understand Pacific seamount volcanism this paper estimates the eruption ages (tvolc) of 2706 volcanoes via automated estimates of lithospheric strength. Lithospheric strength (GTRrel) is deduced from the ratio of gravity to topography above the summits of volcanoes, and is shown to correlate with seafloor age at the time of volcanic loading (Δt) at 61 sites where radiometric constraints upon Δt exist. A trend of fits data for these 61, and with seafloor age (tsf) known, can date the 2706 volcanoes; tvolc = tsf - Δt. Widespread recurrences of volcanism proximal to older features (e.g. the Cook-Austral alignment in French Polynesia) suggest that the lithosphere exerts a significant element of control upon the location of volcanism, and that magmatic throughput leaves the lithosphere more susceptible to the passage of future melts. Observations also prompt speculation that: the Tavara seamounts share morphological characteristics and isostatic compensation state with the Musicians, and probably formed similarly; the Easter Island chain may be a modern analogy to the Cross-Lines; a Musicians - South Hawaiian seamounts alignment may be deflecting the Hawaiian hotspot trace.

  7. Cooling Rates of Lunar Volcanic Glass Beads (United States)

    Hui, Hejiu; Hess, Kai-Uwe; Zhang, Youxue; Peslier, Anne; Lange, Rebecca; Dingwell, Donald; Neal, Clive


    It is widely accepted that the Apollo 15 green and Apollo 17 orange glass beads are of volcanic origin. The diffusion profiles of volatiles in these glass beads are believed to be due to degassing during eruption (Saal et al., 2008). The degree of degassing depends on the initial temperature and cooling rate. Therefore, the estimations of volatiles in parental magmas of lunar pyroclastic deposits depend on melt cooling rates. Furthermore, lunar glass beads may have cooled in volcanic environments on the moon. Therefore, the cooling rates may be used to assess the atmospheric condition in an early moon, when volcanic activities were common. The cooling rates of glasses can be inferred from direct heat capacity measurements on the glasses themselves (Wilding et al., 1995, 1996a,b). This method does not require knowledge of glass cooling environments and has been applied to calculate the cooling rates of natural silicate glasses formed in different terrestrial environments. We have carried out heat capacity measurements on hand-picked lunar glass beads using a Netzsch DSC 404C Pegasus differential scanning calorimeter at University of Munich. Our preliminary results suggest that the cooling rate of Apollo 17 orange glass beads may be 12 K/min, based on the correlation between temperature of the heat capacity curve peak in the glass transition range and glass cooling rate. The results imply that the parental magmas of lunar pyroclastic deposits may have contained more water initially than the early estimations (Saal et al., 2008), which used higher cooling rates, 60-180 K/min in the modeling. Furthermore, lunar volcanic glass beads could have been cooled in a hot gaseous medium released from volcanic eruptions, not during free flight. Therefore, our results may shed light on atmospheric condition in an early moon.

  8. Investigating the consequences of urban volcanism using a scenario approach I: Development and application of a hypothetical eruption in the Auckland Volcanic Field, New Zealand (United States)

    Deligne, Natalia I.; Fitzgerald, Rebecca H.; Blake, Daniel M.; Davies, Alistair J.; Hayes, Josh L.; Stewart, Carol; Wilson, Grant; Wilson, Thomas M.; Castelino, Renella; Kennedy, Ben M.; Muspratt, Scott; Woods, Richard


    What happens when a city has a volcanic eruption within its boundaries? To explore the consequences of this rare but potentially catastrophic combination, we develop a detailed multi-hazard scenario of an Auckland Volcanic Field (AVF) eruption; the AVF underlies New Zealand's largest city, Auckland. We start with an existing AVF unrest scenario sequence and develop it through a month-long hypothetical eruption based on geologic investigations of the AVF and historic similar eruptions from around the world. We devise a credible eruption sequence and include all volcanic hazards that could occur in an AVF eruption. In consultation with Civil Defence and Emergency Management staff, we create a series of evacuation maps for before, during, and after the hypothetical eruption sequence. Our result is a versatile scenario with many possible applications, developed further in companion papers that explore eruption consequences on transportation and water networks. However, here we illustrate one application: evaluating the consequences of an eruption on electricity service provision. In a collaborative approach between scientists and electricity service providers, we evaluate the impact of the hypothetical eruption to electricity generation, transmission, and distribution infrastructure. We then evaluate how the impacted network functions, accounting for network adaptations (e.g., diverting power away from evacuated areas), site access, and restoration factors. We present a series of regional maps showing areas with full service, rolling outages, and no power as a result of the eruption. This illustrative example demonstrates how a detailed scenario can be used to further understand the ramifications of urban volcanism on local and regional populations, and highlights the importance of looking beyond damage to explore the consequences of volcanism.

  9. The volcanism of the western part of the Los Frailes Meseta (Bolivia): a representative example of the Andean volcanism since the Upper Oligocene; Le volcanisme de la bordure occidentale de la Meseta de Los Frailes (Bolivie): un jalon representatif du volcanisme andin depuis l`Oligocene superieur

    Energy Technology Data Exchange (ETDEWEB)

    Leroy, L. [Nancy-1 Univ., 54 (France); Jimenez, N.


    The Los Frailes Meseta (Bolivia) is one of the large tertiary ignimbritic fields of the inner volcanic arc from Central Andes (Central Volcanic Zone. CVZ), in contact zone between the Altiplano to the west and the Eastern Cordillera to the east. Field observations and mineralogical and geochemical studies (major and trace elements) lead to distinguish two types of volcanism in the western border to the Meseta. During the Middle Miocene and Pliocene, the volcanic activity can be subdivided into three pyroclastic emission cycles, the Larco, Coroma and Pliocene ignimbrites, the first two being separated by the Quechua 2 orogeny. All these ignimbrites are very similar and correspond to peraluminous rhyolites to rhyodacites. In the studies area, the Coroma cycle is the only one where an ignimbrite-less evolved resurgent dome association can be observed. Beside these ignimbrites, isolated small lava flows and domes overlay and/or intrude all the other formations. They are meta-aluminous lavas with a shoshonitic affinity. A quaternary age can be attributed to his second volcanism. These two volcanic types are well-known in the CVZ and are related to the different deformation stages, either compressional or extensional, which occur alternately in the Cordillera since 26 Ma. (authors). 61 refs., 12 figs., 3 tabs.

  10. The Plio-Quaternary Volcanic Evolution of Gran Canaria Based on new Unspiked K-Ar ages and Magnetostratigraphy (United States)

    Guillou, H.; Carracedo, J.; Perez Torrado, F.


    The combined use of radioisotopic dating, magnetostratigraphy and field geology is a powerful tool to provide reliable chronological frameworks of volcanic edifices. This approach has been used to investigate the last two stages of the volcanic evolution of Gran Canaria. Fifty samples were dated using the unspiked K-Ar method and had their magnetic polarity measured both in the field and in laboratory. Ages were compared to their stratigraphic positions and magnetic polarities before accepting their validity. The unspiked K-Ar chronology constrains the timing of lateral collapses, eruption rates and the contemporaneity of different volcano-magmatic stages at Gran Canaria. Our new data set modifies significantly the previous chronological framework of Gran Canaria, especially between 4 and 2.8 Ma. Based on these new ages, we can bracket the age of the multiple lateral collapses of the Roque Nublo stratovolcano flanks between 3.5 and 3.1 Ma .This time interval corresponds to a main period of volcanic quiescence. Calculated eruptive rates during the stratovolcano edification are about 0.1 km3/kyr which is significantly lower than the published estimates. The dating also reveals that the two main last stages are not separated by a major time gap, but that the early stages of the rift forming eruption and the vanishing activity of the Roque Nublo strato-volcano were contemporaneous for at least 600 kyrs. These results support that our combined approach provides a rapid first-pass and reliable geochronology. Nevertheless, this chronology can be amplified and made more precise where necessary through detailed Ar-Ar incremental-heating methods. Samples which should be investigated using this method are the oldest and youngest K-Ar dated flows of each volcanic stage, and samples from stratigraphic sections that hold potential to study the behaviour of the earth's magnetic field during reversals (Gauss-Gilbert transition, Olduvai and Reunion events).

  11. The frequency of explosive volcanic eruptions in Southeast Asia. (United States)

    Whelley, Patrick L; Newhall, Christopher G; Bradley, Kyle E

    There are ~750 active and potentially active volcanoes in Southeast Asia. Ash from eruptions of volcanic explosivity index 3 (VEI 3) and smaller pose mostly local hazards while eruptions of VEI ≥ 4 could disrupt trade, travel, and daily life in large parts of the region. We classify Southeast Asian volcanoes into five groups, using their morphology and, where known, their eruptive history and degassing style. Because the eruptive histories of most volcanoes in Southeast Asia are poorly constrained, we assume that volcanoes with similar morphologies have had similar eruption histories. Eruption histories of well-studied examples of each morphologic class serve as proxy histories for understudied volcanoes in the class. From known and proxy eruptive histories, we estimate that decadal probabilities of VEI 4-8 eruptions in Southeast Asia are nearly 1.0, ~0.6, ~0.15, ~0.012, and ~0.001, respectively.

  12. MaROS: Information Management Service (United States)

    Allard, Daniel A.; Gladden, Roy E.; Wright, Jesse J.; Hy, Franklin H.; Rabideau, Gregg R.; Wallick, Michael N.


    This software is provided by the Mars Relay Operations Service (MaROS) task to a variety of Mars projects for the purpose of coordinating communications sessions between landed spacecraft assets and orbiting spacecraft assets at Mars. The Information Management Service centralizes a set of functions previously distributed across multiple spacecraft operations teams, and as such, greatly improves visibility into the end-to-end strategic coordination process. Most of the process revolves around the scheduling of communications sessions between the spacecraft during periods of time when a landed asset on Mars is geometrically visible by an orbiting spacecraft. These relay sessions are used to transfer data both to and from the landed asset via the orbiting asset on behalf of Earth-based spacecraft operators. This software component is an application process running as a Java virtual machine. The component provides all service interfaces via a Representational State Transfer (REST) protocol over https to external clients. There are two general interaction modes with the service: upload and download of data. For data upload, the service must execute logic specific to the upload data type and trigger any applicable calculations including pass delivery latencies and overflight conflicts. For data download, the software must retrieve and correlate requested information and deliver to the requesting client. The provision of this service enables several key advancements over legacy processes and systems. For one, this service represents the first time that end-to-end relay information is correlated into a single shared repository. The software also provides the first multimission latency calculator; previous latency calculations had been performed on a mission-by-mission basis.

  13. "Sel kevadel olen ma eriti ilus..." : [luuletused] / Triin Soomets

    Index Scriptorium Estoniae

    Soomets, Triin


    Sisu: "Sel kevadel olen ma eriti ilus..." ; "Tahaksin teha midagi tõelist; midagi suurt..." ; "veebruaris on keha nii valge et syda läheb pahaks..." ; "kõige kohutavamad lepingud..." ; "Igal loojangul kutsun sind ja igal koidikul tõukan su ära..." ; "need hakid..." ; "Põhja vajudes on viimane asi, mida ma näen, rohelised sähvatused..."

  14. Alumni careers : MA Comparative European Social Studies Zuyd University

    NARCIS (Netherlands)

    Albert Riga


    In the preparation of the celebration of the 10th anniversary of the MA CESS all alumni were invited to participate in an alumni survey. The purpose of the survey was to thoroughly investigate the professional activities of MA CESS alumni and the way they build an alumni community. Another reason

  15. How to use MAED with other IAEA models in ENPEP

    International Nuclear Information System (INIS)

    Maksijan, B.


    This paper provides an outlook of the energy situation in Croatia and describes the experience with the IAEA planning methodologies with focus on the MAED model. Furthermore, it suggests an approach to integrate the results of the MAED module of ENPEP with other modules (e.g. BALANCE) by means of commercial software (EXCEL Microsoft). (author). 2 figs, 3 tabs

  16. Large area imaging of forensic evidence with MA-XRF

    NARCIS (Netherlands)

    Langstraat, K.; Knijnenberg, A.; Edelman, G.; van de Merwe, L.; van Loon, A.; Dik, J.; van Asten, A.


    This study introduces the use of macroscopic X-ray fluorescence (MA-XRF) for the detection, classification and imaging of forensic traces over large object areas such as entire pieces of clothing and wall paneling. MA-XRF was sufficiently sensitive and selective to detect human biological traces

  17. Large area imaging of forensic evidence with MA-XRF

    NARCIS (Netherlands)

    Langstraat, Kirsten; Knijnenberg, Alwin; Edelman, Gerda; Van De Merwe, Linda; van Loon, A.; Dik, J.; van Asten, Arian C.


    This study introduces the use of macroscopic X-ray fluorescence (MA-XRF) for the detection, classification and imaging of forensic traces over large object areas such as entire pieces of clothing and wall paneling. MA-XRF was sufficiently sensitive and selective to detect human biological traces

  18. 42 CFR 422.2268 - Standards for MA organization marketing. (United States)


    ... 42 Public Health 3 2010-10-01 2010-10-01 false Standards for MA organization marketing. 422.2268 Section 422.2268 Public Health CENTERS FOR MEDICARE & MEDICAID SERVICES, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICARE PROGRAM MEDICARE ADVANTAGE PROGRAM Medicare Advantage Marketing Requirements § 422.2268 Standards for MA organizatio...

  19. 42 CFR 422.4 - Types of MA plans. (United States)


    ... availability, service area, and quality. (ii) Coordinated care plans may include mechanisms to control... requirements of sections 138 and 220 of the Internal Revenue Code. (3) MA private fee-for-service plan. An MA... Health CENTERS FOR MEDICARE & MEDICAID SERVICES, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED...

  20. How to use MAED with other IAEA models in ENPEP

    Energy Technology Data Exchange (ETDEWEB)

    Maksijan, B [Energy Sector, Ministry of Economic Affairs, Zagreb (Croatia)


    This paper provides an outlook of the energy situation in Croatia and describes the experience with the IAEA planning methodologies with focus on the MAED model. Furthermore, it suggests an approach to integrate the results of the MAED module of ENPEP with other modules (e.g. BALANCE) by means of commercial software (EXCEL Microsoft). (author). 2 figs, 3 tabs.

  1. Miocene shoshonite volcanism in Sardinia: Implications for magma sources and geodynamic evolution of the central-western Mediterranean (United States)

    Beccaluva, Luigi; Bianchini, Gianluca; Mameli, Paola; Natali, Claudio


    In this paper we document the existence of a Miocene shoshonite (SHO) volcanism in Northern Sardinia (Anglona). This occurrence completes the spectrum of orogenic magmas related to the subduction process which developed from the Eocene along the Palaeo-European continental margin, in concert with the opening of the Ligurian-Balearic back-arc basin and southeastward drift/rotation of the Sardinia-Corsica continental block. K-Ar ages show that the oldest volcanics of the area are calcalkaline (CA) basalts and andesites (~ 21 Ma), overlain by 19.7-18.4 Ma-old more potassic products such as high-potassium calcalkaline (HK-CA) and SHO lavas. CA, HK-CA and SHO suites include basalts and differentiated lavas of andesite and latite composition, respectively, that (according to the PELE software modelling) represent ~ 40-45% residual liquid fraction after shallow fractional crystallization. Application of the "Arc Magma Simulator" software suggests that the generation of primary melts of the distinct suites may occur at similar degrees of partial melting (5-8%) and melting pressures (2-2.2 GPa, ~ 60-70 km depth) in the mantle wedge. By contrast, the potassic character of parental melts of CA, HK-CA and SHO suites is controlled by 1) the amount of subducted continental components (possibly terrigenous sediments) and 2) the pressure (depth) at which these metasomatic agents are released from the slab. Results suggest that the slab depth beneath the volcanic district increased from ~ 80-100 to 100-120 km for CA and SHO magmas, respectively. Accordingly, the evolution from CA to SHO magmatism in the same plumbing system could be related to slab deepening and increase of the subduction angle of ~ 5-10° in the time span of 2-3 Ma. This tectono-magmatic scenario conforms to the major anticlockwise rotation (~ 30°) event of the Sardinia block (between 20.5 and 18 Ma). This geodynamic evolution preludes the development of the volcanism in the Apennine-Tyrrhenian domains, where the

  2. The (mis)Measurement of M&A Performance

    DEFF Research Database (Denmark)

    Meglio, Olimpia; Risberg, Annette


    This paper seeks to further the understanding of the variety of meanings M&A scholars attach to the label “M&A performance” by providing an alternative way to interpret the claimed inconsistency of M&A research findings. While many scholars contend that the problem stems from the multiplicity of M......&A performance measures, we believe the problem rests in trying to compare different measures as if they were measuring the same feature of the organization. Through our narrative review of empirical research we analyze factors shaping the M&A – as well as the organizational – performance measurement process....... The conclusion is that it is not possible to talk about M&A performance as if it was a universal construct....

  3. P-Wave Velocity Tomography from Local Earthquakes in Western Mexico (United States)

    Ochoa-Chávez, Juan A.; Escudero, Christian R.; Núñez-Cornú, Francisco J.; Bandy, William L.


    In western Mexico, the subduction of the Rivera and Cocos plates beneath the North America plate has deformed and fragmented the overriding plate, forming several structural rifts and crustal blocks. To obtain a reliable subsurface image of the continental crust and uppermost mantle in this complex area, we used P-wave arrivals of local earthquakes along with the Fast Marching Method tomography technique. We followed an inversion scheme consisting of (1) the use of a high-quality earthquake catalog and corrected phase picks, (2) the selection of earthquakes using a maximum location error threshold, (3) the estimation of an improved 1-D reference velocity model, and (4) the use of checkerboard testing to determine the optimum configuration of the velocity nodes and inversion parameters. Surprisingly, the tomography results show a very simple δVp distribution that can be described as being controlled by geologic structures formed during two stages of the separation of the Rivera and Cocos plates. The earlier period represents the initial stages of the separation of the Rivera and Cocos plates beneath western Mexico; the later period represents the more advanced stage of rifting where the Rivera and Cocos plates had separated sufficiently to allow melt to accumulate below the Colima Volcanic complex. During the earlier period (14 or 10-1.6 Ma), NE-SW-oriented structures/lineaments (such as the Southern Colima Rift) were formed as the two plates separated. During the second period (1.6 Ma to the present), the deformation is attributed to magma, generated within and above the tear zone between the Rivera and Cocos plates, rising beneath the region of the Colima Volcanic Complex. The rising magma fractured the overlying crust, forming a classic triple-rift junction geometry. This triple-rift system is confined to the mid- to lower crust perhaps indicating that this rifting process is still in an early stage. This fracturing, along with fluid circulation and associated

  4. Welcoming a monster to the world: Myths, oral tradition, and modern societal response to volcanic disasters (United States)

    Cashman, Katharine V.; Cronin, Shane J.


    have incorporated volcanoes into the lineage of tribes and individuals, thus good and bad outcomes from volcanism are part of long-term cycles of reciprocity and equilibrium that link modern Maori to their ancestors. In both regions, cosmologies and mythologies not only document the attempts of past cultures to recover from the impacts of volcanic disasters, but also provide a means by which following generations can understand, contextualize, and therefore recover from, future volcanic catastrophes. We further suggest that such local traditions can provide a valuable community education tool as well as an important means of aiding the psychosocial recovery of individuals and communities after volcanic disasters.

  5. The Timber Mountain magmato-thermal event: An intense widespread culmination of magmatic and hydrothermal activity at the southwestern Nevada volcanic field

    International Nuclear Information System (INIS)

    Jackson, M.R. Jr.


    Eruption of the Rainier Mesa and Ammonia Tanks Members Timber Mountain Tuff at about 11.5 and 11.3 Ma, respectively, resulted in formation of the timber Mountain (TM) caldera; new K-Ar ages show that volcanism within and around the TM caldera continued for about 1 m.y. after collapse. Some TM age magmatic activity took place west and southeast of the TM caldera in the Beatty -- Bullfrog Hills and Shoshone Mountain areas, suggesting that volcanic activity at the TM caldera was an intense expression of an areally extensive magmatic system active from about 11.5 to 10Ma. Epithermal Au-Ag, Hg and fluorite mineralization and hydrothermal alteration are found in both within and surrounding the Timber Mountain -- Oasis Valley caldera complex. New K-Ar ages date this hydrothermal activity between about 13 and 10 Ma, largely between about 11.5 and 10 Ma, suggesting a genetic relation of hydrothermal activity to the TM magmatic system

  6. The Timber Mountain magmato-thermal event: An intense widespread culmination of magmatic and hydrothermal activity at the southwestern Nevada volcanic field

    Energy Technology Data Exchange (ETDEWEB)

    Jackson, Jr., Mac Roy [Univ. of Nevada, Reno, NV (United States)


    Eruption of the Rainier Mesa and Ammonia Tanks Members Timber Mountain Tuff at about 11.5 and 11.3 Ma, respectively, resulted in formation of the timber Mountain (TM) caldera; new K-Ar ages show that volcanism within and around the TM caldera continued for about 1 m.y. after collapse. Some TM age magmatic activity took place west and southeast of the TM caldera in the Beatty -- Bullfrog Hills and Shoshone Mountain areas, suggesting that volcanic activity at the TM caldera was an intense expression of an areally extensive magmatic system active from about 11.5 to 10Ma. Epithermal Au-Ag, Hg and fluorite mineralization and hydrothermal alteration are found in both within and surrounding the Timber Mountain -- Oasis Valley caldera complex. New K-Ar ages date this hydrothermal activity between about 13 and 10 Ma, largely between about 11.5 and 10 Ma, suggesting a genetic relation of hydrothermal activity to the TM magmatic system.

  7. Conceptual model of volcanism and volcanic hazards of the region of Ararat valley, Armenia (United States)

    Meliksetian, Khachatur; Connor, Charles; Savov, Ivan; Connor, Laura; Navasardyan, Gevorg; Manucharyan, Davit; Ghukasyan, Yura; Gevorgyan, Hripsime


    Armenia and the adjacent volcanically active regions in Iran, Turkey and Georgia are located in the collision zone between the Arabian and Eurasian lithospheric plates. The majority of studies of regional collision related volcanism use the model proposed by Keskin, (2003) where volcanism is driven by Neo-Tethyan slab break-off. In Armenia, >500 Quaternary-Holocene volcanoes from the Gegham, Vardenis and Syunik volcanic fields are hosted within pull-apart structures formed by active faults and their segments (Karakhanyan et al., 2002), while tectonic position of the large in volume basalt-dacite Aragats volcano and periphery volcanic plateaus is different and its position away from major fault lines necessitates more complex volcano-tectonic setup. Our detailed volcanological, petrological and geochemical studies provide insight into the nature of such volcanic activity in the region of Ararat Valley. Most magmas, such as those erupted in Armenia are volatile-poor and erupt fairly hot. Here we report newly discovered tephra sequences in Ararat valley, that were erupted from historically active Ararat stratovolcano and provide evidence for explosive eruption of young, mid K2O calc-alkaline and volatile-rich (>4.6 wt% H2O; amph-bearing) magmas. Such young eruptions, in addition to the ignimbrite and lava flow hazards from Gegham and Aragats, present a threat to the >1.4 million people (~ ½ of the population of Armenia). We will report numerical simulations of potential volcanic hazards for the region of Ararat valley near Yerevan that will include including tephra fallout, lava flows and opening of new vents. Connor et al. (2012) J. Applied Volcanology 1:3, 1-19; Karakhanian et al. (2002), JVGR, 113, 319-344; Keskin, M. (2003) Geophys. Res. Lett. 30, 24, 8046.

  8. Volcanic Gases and Hot Spring Water to Evaluate the Volcanic Activity of the Mt. Baekdusan (United States)

    Yun, S. H.; Lee, S.; Chang, C.


    This study performed the analysis on the volcanic gases and hot spring waters from the Julong hot spring at Mt. Baekdu, also known as Changbaishan on the North Korea(DPRK)-China border, during the period from July 2015 to August 2016. Also, we confirmed the errors that HCO3- concentrations of hot spring waters in the previous study (Lee et al. 2014) and tried to improve the problem. Dissolved CO2 in hot spring waters was analyzed using gas chromatograph in Lee et al.(2014). Improving this, from 2015, we used TOC-IC to analysis dissolved CO2. Also, we analyzed the Na2CO3 standard solutions of different concentrations using GC, and confirmed the correlation between the analytical concentrations and the real concentrations. However, because the analytical results of the Julong hot spring water were in discord with the estimated values based on this correlation, we can't estimate the HCO3-concentrations of 2014 samples. During the period of study, CO2/CH4 ratios in volcanic gases are gradually decreased, and this can be interpreted in two different ways. The first interpretation is that the conditions inside the volcanic edifice are changing into more reduction condition, and carbon in volcanic gases become more favorable to distribute into CH4 or CO than CO2. The second interpretation is that the interaction between volcanic gases and water becomes greater than past, and the concentrations of CO2which have much higher solubility in water decreased, relatively. In general, the effect of scrubbing of volcanic gas is strengthened during the quiet periods of volcanic activity rather than active periods. Meanwhile, the analysis of hot spring waters was done on the anion of acidic gases species, the major cations, and some trace elements (As, Cd, Re).This work was funded by the Korea Meteorological Administration Research and Development Program under Grant KMIPA 2015-3060.

  9. [Effects of volcanic eruptions on human health in Iceland. Review]. (United States)

    Gudmundsson, Gunnar; Larsen, Guðrun


    Volcanic eruptions are common in Iceland and have caused health problems ever since the settlement of Iceland. Here we describe volcanic activity and the effects of volcanic gases and ash on human health in Iceland. Volcanic gases expelled during eruptions can be highly toxic for humans if their concentrations are high, irritating the mucus membranes of the eyes and upper respiratory tract at lower concentrations. They can also be very irritating to the skin. Volcanic ash is also irritating for the mucus membranes of the eyes and upper respiratory tract. The smalles particles of volcanic ash can reach the alveoli of the lungs. Described are four examples of volcanic eruptions that have affected the health of Icelanders. The eruption of Laki volcanic fissure in 1783-1784 is the volcanic eruption that has caused the highest mortality and had the greatest effects on the well-being of Icelanders. Despite multiple volcanic eruptions during the last decades in Iceland mortality has been low and effects on human health have been limited, although studies on longterm effects are lacking. Studies on the effects of the Eyjafjallajökul eruption in 2010 on human health showed increased physical and mental symptoms, especially in those having respiratory disorders. The Directorate of Health in Iceland and other services have responded promptly to recurrent volcanic eruptions over the last few years and given detailed instructions on how to minimize the effects on the public health. Key words: volcanic eruptions, Iceland, volcanic ash, volcanic gases, health effects, mortality. Correspondence: Gunnar Guðmundsson,

  10. U-Pb SHRIMP and Sm-Nd geochronology of the Silvania Volcanics and Jurubatuba Granite: juvenile paleoproterozoic crust in the basement of the Neo proterozoic Brasilia Belt, Goias, central Brazil

    International Nuclear Information System (INIS)

    Fischel, Danielle P.; Pimentel, Marcio M.; Fuck, Reinhardt A.; Armstrong, Richard


    U-Pb SHRIMP and Sm-Nd isotopic ages were determined for felsic meta volcanic rocks from the Silvania Sequence and Jurubatuba Granite in the central part of the Brasilia Belt. Zircon grains from a meta volcanic sample yielded 2115 ± 23 Ma and from the granite yielded 2089 ±14 Ma, interpreted as crystallization ages of these rocks. Six meta volcanic samples of the Silvania Sequence yielded a six-point whole-rock Sm-Nd isochron indicating a crystallization age of 2262 ±110 Ma and positive ε Nd (T) = +3.0 interpreted as a juvenile magmatic event. Nd isotopic analyses on samples from the Jurubatuba Granite have Paleoproterozoic T DM model ages between 2.30 and 2.42 Ga and ε Nd (T) values vary between -0.22 and -0.58. The oldest T DM value refers to a sedimentary xenolith in the granite. These results suggest crystallization ages of Silvania volcanics and Jurubatuba Granite are the first evidence of a ca. 2.14-2.08 juvenile magmatic event in the basement of the central part of the Brasilia Belt that implies the presence of arc/suture hidden in reworked basement of the Brasilia Belt. (author)

  11. U-Pb SHRIMP and Sm-Nd geochronology of the Silvania Volcanics and Jurubatuba Granite: juvenile paleoproterozoic crust in the basement of the Neo proterozoic Brasilia Belt, Goias, central Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Fischel, Danielle P.; Pimentel, Marcio M.; Fuck, Reinhardt A. [Brasilia Univ., DF (Brazil). Inst. de Geociencias; Armstrong, Richard [Australian National Univ., Canberra (Australia). Research School of Earth Sciences


    U-Pb SHRIMP and Sm-Nd isotopic ages were determined for felsic meta volcanic rocks from the Silvania Sequence and Jurubatuba Granite in the central part of the Brasilia Belt. Zircon grains from a meta volcanic sample yielded 2115 {+-} 23 Ma and from the granite yielded 2089 {+-}14 Ma, interpreted as crystallization ages of these rocks. Six meta volcanic samples of the Silvania Sequence yielded a six-point whole-rock Sm-Nd isochron indicating a crystallization age of 2262 {+-}110 Ma and positive {epsilon}{sub Nd} (T) = +3.0 interpreted as a juvenile magmatic event. Nd isotopic analyses on samples from the Jurubatuba Granite have Paleoproterozoic T{sub DM} model ages between 2.30 and 2.42 Ga and {epsilon}{sub Nd} (T) values vary between -0.22 and -0.58. The oldest T{sub DM} value refers to a sedimentary xenolith in the granite. These results suggest crystallization ages of Silvania volcanics and Jurubatuba Granite are the first evidence of a ca. 2.14-2.08 juvenile magmatic event in the basement of the central part of the Brasilia Belt that implies the presence of arc/suture hidden in reworked basement of the Brasilia Belt. (author)

  12. 77 FR 16849 - Notice of Realignment/Merger of Five Regional Audit Offices: Boston, MA Will Merge With New York... (United States)


    ... of Five Regional Audit Offices: Boston, MA Will Merge With New York, NY; and the Gulf Coast Region... result from the reorganization; (3) a discussion of the impact on the local economy; and (4) an estimate... Department (such as the establishment of new or combination of existing organization units within a field...

  13. Ma ma (2015. A reflection of the Spanish woman with breast cáncer

    Directory of Open Access Journals (Sweden)



    Full Text Available Ma ma (2015 is a Spanish drama film directed by Julio Medem and produced by Morena Films. This film tells the story of Magda’s life, whose character is interpreted by Penélope Cruz. After being diagnosed with a breast cancer, Magda, an unemployed teacher, will not know how to act nor how this disease will change her life. But little by little, she will bring into the surface all her vital energy. Breast cancer represents the most frequent type of cancer among women. Although the majority of the identified risk factors can be modified, the health systems focus on activities that let strengthen the primary prevention and activities of secondary and tertiary prevention. The early detection and the right treatment are essential to fight against this disease. The emotional process caused by the presence of cancer involves a mechanism of psychic reconstitution that allows the patient develop an answer to the organic, cognitive, social, and emotional challenges they have to deal with. This process is easier when they have a solid socio-family support network among other factors.

  14. Morotochoerus from Uganda (17.5 Ma and Kenyapotamus from Kenya (13-11 Ma: implications for hippopotamid origins

    Directory of Open Access Journals (Sweden)

    Pickford, M.


    Full Text Available The aim of this paper is to describe and interpret suiform teeth from Moroto, Uganda, and Ngorora, Kenya, which contribute to the debate about hippo-anthracothere-whale relationships. The early stages of hippopotamid evolution are relatively poorly known on account of the paucity of their fossil record older than 7 Ma. New specimens of Morotochoerus from Uganda reveal that it is not closely related to Hippopotamidae; the superficial resemblances of the cheek teeth to those of hippos represent convergences and not homologies. Restricted samples of Palaeopotamus ternani are available from the Middle Miocene of Kenya {Maboko, ca 16 Ma; Muruyur, ca 14.5 Ma; Fort Ternan, ca 13.7 Ma} while from the base of the late Miocene, Kenyapotamus coryndonae is known from Kenya {Ngerngerwa, ca 10.5-10 Ma; Nakali, ca 10.5 Ma; Samburu Hills, ca 9.5 Ma}, Ethiopia {Ch’orora, ca 10.5 Ma} and Tunisia {Beglia Formation ca 11-10 Ma}. The recovery of specimens of Kenyapotamus from the Ngorora Formation, Kenya, aged ca 11 Ma, is of interest because it includes well preserved teeth, including an m/3 in good condition. These specimens support the hypothesis that hippopotamids descended from palaeochoerids and not from anthracotheres.El objetivo de este trabajo es describir e interpretar los dientes suiformes de Moroto, Uganda, y Ngorora, Kenia, que contribuyen al debate sobre las relaciones hipo-anthracothere-whale. Las primeras etapas de la evolución de los hipopotámidos son relativamente poco conocidas a causa de la escasez de su registro fósil en edades superiors a los 7 Ma. Nuevos ejemplares de Morotochoerus en Uganda revelan que no están estrechamente relacionados con Hippopotamidae, las semejanzas superficiales de los dientes de la mandíbula con los de los hipopótamos representan convergencias y no homologías. Algunas muestras de Palaeopotamus ternani aparecen en el Medio Mioceno de Kenia {Maboko, ca 16 Ma; Muruyur, ca 14.5 Ma; Fort Ternan, ca 13.7 Ma

  15. Seismic and GPS constraints on the dynamics and kinematics of the Yellowstone volcanic field (United States)

    Smith, R. B.; Farrell, J.; Jordan, M.; Puskas, C.; Waite, G. P.


    The seismically and volcanically Yellowstone hotspot resulted from interaction of a mantle plume with the overriding North America plate. This feature and related processes have modified continental lithosphere producing the Yellowstone-Snake River Plain-Newberry silicic volcanic field (YSRPN) system, with its NE volcanically active Yellowstone volcanic field. The size and accessibility of the Yellowstone area has allowed a range of geophysical experiments including earthquake monitoring and seismic and GPS imaging of this system. Seismicity is dominated by small-magnitude normal- to oblique-slip faulting earthquake swarms with shallow focal depths, maximum of ~5 km, restricted by high temperatures and a weak elastic layer. There is developing evidence of non-double couple events. Outside the caldera, earthquakes are deeper, ~20 km, and capable of M 7+ earthquakes. We integrate the results from a multi-institution experiment that recorded data from 110 seismic stations and 180 GPS stations for 1999-2004. The tomographic images confirm the existence of a low Vp-body beneath the Yellowstone caldera at depths greater than 8 km, possibly representing hot, crystallizing magma. A key result of our study is a volume of anomalously low Vp and Vp/Vs in the northwestern part of the volcanic field at shallow depths of stress field inverted from seismic and GPS data is dominated by regional SW extension with superimposed volumetric expansion and uplift from local volcanic sources. Mantle tomography derived from integrated inversion of teleseismic and local earthquake data constrained by geoid, crustal structure, discontinuity structure reveals an upper-mantle low P and S velocity body extends from 80 km to ~250 km directly beneath Yellowstone and then continues to 650 km with unexpected westward tilt to the west at ~60° with a 1% to 2% melt. This geometry is consistent with the ascent of the buoyant magma entrained in eastward return-flow of the upper mantle. Some remaining

  16. [US Geological Survey research in radioactive waste disposal, fiscal year 1980:] Tectonics, seismicity, volcanism, and erosion rates in the southern Great Basin

    International Nuclear Information System (INIS)

    Carr, W.J.; Rogers, A.M.


    The objective is to assess the potential for faulting, damaging earthquakes, recurrence of volcanism, and local acceleration of erosion in parts of the southern Great Basin. The following approaches are being used: (1) investigating the rate, intensity, and distribution of faulting during approximately the last 25 m.y., with emphasis on the last 10 m.y.; (2) monitoring and interpreting present seismicity; (3) studying the history of volcanism; and (4) evaluating past rates of erosion and deposition. Progress is reported

  17. Glacial removal of late Cenozoic subglacially emplaced volcanic edifices by the West Antarctic ice sheet (United States)

    Behrendt, John C.; Blankenship, D.D.; Damaske, D.; Cooper, A. K.


    Local maxima of the horizontal gradient of pseudogravity from closely spaced aeromagnetic surveys over the Ross Sea, northwestern Ross Ice Shelf, and the West Antarctic ice sheet, reveal a linear magnetic rift fabric and numerous subcircular, high-amplitude anomalies. Geophysical data indicate two or three youthful volcanic edifices at widely separated areas beneath the sea and ice cover in the West Antarctic rift system. In contrast, we suggest glacial removal of edifices of volcanic sources of many more anomalies. Magnetic models, controlled by marine seismic reflection and radar ice-sounding data, allow us to infer that glacial removal of the associated late Cenozoic volcanic edifices (probably debris, comprising pillow breccias, and hyaloclastites) has occurred essentially concomitantly with their subglacial eruption. "Removal' of unconsolidated volcanic debris erupted beneath the ice is probably a more appropriate term than "erosion', given its fragmented, ice-contact origin. The exposed volcanoes may have been protected from erosion by the surrounding ice sheet because of more competent rock or high elevation above the ice sheet. -from Authors

  18. The mitigation of volcanic risk as opportunity for an ecological and resilient city

    Directory of Open Access Journals (Sweden)

    Giulio Zuccaro


    Full Text Available The paper outlines some of the results of SPeeD project, funded by EU, Campania Region and National Department of Civil Protection. The research is aimed at the definition of impact scenarios resulting from the eruption of Vesuvius and Campi Flegrei and the development of strategies to reduce the damage on the built environment. The issues related to the identification of technical solutions for mitigating the impact on buildings and infrastructure, to the socio-economic benefits arising from widespread interventions on the territory, as well as to the drafting of preparatory guidelines for the implementation of regional regulations and local building codes for volcanic risk-prone areas, have been developed at PLINIVS Study Centre of University of Naples Federico II. The methodological approach for the definition of appropriate technologies aimed at reducing the impact in relation to eruptive phenomena and construction types in the area is based on PLINIVS Volcanic Impact Simulation Model, a unique tool to define impact scenarios consequent to a volcanic eruption in the region, able to evaluate the cumulative effects given by the action of volcanic phenomena, such as earthquake, ash fall, pyroclastic flows and landslides. The study aims to demonstrate how the application of appropriate technologies for retrofit interventions or new constructions, aimed at reducing the vulnerability of building components, represents at the same time an opportunity to encourage a diffuse redevelopment of the territory driven by energy and environmental efficiency issues.

  19. Evolution of volcaniclastic apron during initiation of Cascade volcanism in southern Oregon

    Energy Technology Data Exchange (ETDEWEB)

    Bestland, E.A.


    The Oligocene Colestin Formation consists of volcaniclastic apron sequence that records the initiation of Cascade volcanism in the western Cascade Range of southern Oregon. The formation in the type area is largely confined to an east-west-trending graben approximately 8 km wide. This graben and other smaller grabens within it developed to the west of and perpendicular to the axis of the Oligocene Cascade arc. The apron, which fills and locally overflows the graben, consists of coalesced lobes of volcaniclastic and pyroclastic deposits and lesser amounts of lava flows. Abrupt lateral facies changes on a scale of tens to hundreds of meters were produced by the lobe style of deposition and contemporaneous basin faulting. Interstratified with the discontinuous apron sediments are marker units that consist of pyroclastic flows, paleosols, and lava-flow sequences. In the upper half of the formation, the apron can be subdivided into informal members (lobes and sequences of lobes), which can be mapped according to their composition and stratigraphic position. Each member formed during a distinct interval of volcanism. An epiclastic lobe in the upper part of the formation, containing debris-flow and hyperconcentrated flood-flow deposits, represents a period of effusive or mildly explosive andesitic and basaltic volcanism. This epiclastic lobe pinches out to the south under a member that consists of tuffaceous sandstones and interbedded welded and nonwelded pyroclastic flows. The pulselike style of apron growth was produced by the episodic shifting of volcanism along the arc.

  20. Lunar mare volcanism - Stratigraphy, eruption conditions, and the evolution of secondary crusts (United States)

    Head, James W., III; Wilson, Lionel


    Recent developments in the geological analysis of lunar mare volcanism are reviewed. Analysis of returned samples and photogeological and remote sensing studies shows that mare volcanism began prior to the end of heavy bombardment (the period of cryptomare formation), in pre-Nectarian times, and continued until the Copernical Period, the total duration approaching 3.5-4 Ga. Stratigraphic analysis shows that the flux was not constant, but peaked in early lunar history, during the Imbrian Period. Average volcanic output rate during this period was about 0.01 cu cm/a. Volcanic landforms indicate that many eruptions were of high volume and long duration. Some eruptions associated with sinuous rills may have lasted a year and emplaced 1000 cu km of lava, representing the equivalent in one year of about 70,000 yr at the average flux. The occurrence of farside maria within craters whose diameter is generally near to or less than the thickness of the crust may be accounted for by the difference between local and regional compensation.

  1. Sr, Nd and Pb isotope and geochemical data from the Quaternary Nevado de Toluca volcano, a source of recent adakitic magmatism, and the Tenango Volcanic Field, Mexico (United States)

    Martínez-Serrano, Raymundo G.; Schaaf, Peter; Solís-Pichardo, Gabriela; Hernández-Bernal, Ma. del Sol; Hernández-Treviño, Teodoro; Julio Morales-Contreras, Juan; Macías, José Luis


    Volcanic activity at Nevado de Toluca (NT) volcano began 2.6 Ma ago with the emission of andesitic lavas, but over the past 40 ka, eruptions have produced mainly lava flows and pyroclastic deposits of predominantly orthopyroxene-hornblende dacitic composition. In the nearby Tenango Volcanic Field (TVF) pyroclastic products and lava flows ranging in composition from basaltic andesite to andesite were erupted at most of 40 monogenetic volcanic centers and were coeval with the last stages of NT. All volcanic rocks in the study area are characterized by a calc-alkaline affinity that is consistent with a subduction setting. Relatively high concentrations of Sr (>460 ppm) coupled with low Y (45 km) that underlies the volcanoes of the study area, the geochemical and isotopic patterns of these rocks indicate low interaction with this crust. NT volcano was constructed at the intersection of three fault systems, and it seems that the Plio-Quaternary E-W system played an important role in the ascent and storage of magmas during the recent volcanic activity in the two regions. Chemical and textural features of orthopyroxene, amphibole and Fe-Ti oxides from NT suggest that crystallization of magmas occurred at polybaric conditions, confirming the rapid upwelling of magmas.

  2. Volcanic Origin of Alkali Halides on Io (United States)

    Schaefer, L.; Fegley, B., Jr.


    The recent observation of NaCl (gas) on Io confirms our earlier prediction that NaCl is produced volcanically. Here we extend our calculations by modeling thermochemical equilibrium of O, S, Li, Na, K, Rb, Cs, F, Cl, Br, and I as a function of temperature and pressure in a Pele-like volcanic gas with O/S/Na/Cl/K = 1.518/1/0.05/0.04/0.005 and CI chondritic ratios of the other (as yet unobserved) alkalis and halogens. For reference, the nominal temperature and pressure for Pele is 1760 plus or minus 210 K and 0.01 bars based on Galileo data and modeling.

  3. The scaling of experiments on volcanic systems

    Directory of Open Access Journals (Sweden)

    Olivier eMERLE


    Full Text Available In this article, the basic principles of the scaling procedure are first reviewed by a presentation of scale factors. Then, taking an idealized example of a brittle volcanic cone intruded by a viscous magma, the way to choose appropriate analogue materials for both the brittle and ductile parts of the cone is explained by the use of model ratios. Lines of similarity are described to show that an experiment simulates a range of physical processes instead of a unique natural case. The pi theorem is presented as an alternative scaling procedure and discussed through the same idealized example to make the comparison with the model ratio procedure. The appropriateness of the use of gelatin as analogue material for simulating dyke formation is investigated. Finally, the scaling of some particular experiments such as pyroclastic flows or volcanic explosions is briefly presented to show the diversity of scaling procedures in volcanology.

  4. Volcanic emission of radionuclides and magma dynamics

    International Nuclear Information System (INIS)

    Lambert, G.; Le Cloarec, M.F.; Ardouin, B.; Le Roulley, J.C.


    210 Pb, 210 Bi and 210 Po, the last decay products of the 238 U series, are highly enriched in volcanic plumes, relative to the magma composition. Moreover this enrichment varies over time and from volcano to volcano. A model is proposed to describe 8 years of measurements of Mt. Etna gaseous emissions. The lead and bismuth coefficients of partition between gaseous and condensated phases in the magma are determined by comparing their concentrations in lava flows and condensated volatiles. In the case of volatile radionuclides, an escaping time is calculated which appears to be related to the volcanic activity. Finally, it is shown that that magma which is degassing can already be partly degassed; it should be considered as a mixture of a few to 50% of deep non-degassed magma with a well degassed superficial magma cell. (orig.)

  5. Seasonal variations of volcanic eruption frequencies (United States)

    Stothers, Richard B.


    Do volcanic eruptions have a tendency to occur more frequently in the months of May and June? Some past evidence suggests that they do. The present study, based on the new eruption catalog of Simkin et al.(1981), investigates the monthly statistics of the largest eruptions, grouped according to explosive magnitude, geographical latitude, and year. At the 2-delta level, no month-to-month variations in eruption frequency are found to be statistically significant. Examination of previously published month-to-month variations suggests that they, too, are not statistically significant. It is concluded that volcanism, at least averaged over large portions of the globe, is probably not periodic on a seasonal or annual time scale.

  6. Alteration of submarine volcanic rocks in oxygenated Archean oceans (United States)

    Ohmoto, H.; Bevacqua, D.; Watanabe, Y.


    Most submarine volcanic rocks, including basalts in diverging plate boundaries and andesites/dacites in converging plate boundaries, have been altered by low-temperature seawater and/or hydrothermal fluids (up to ~400°C) under deep oceans; the hydrothermal fluids evolved from shallow/deep circulations of seawater through the underlying hot igneous rocks. Volcanogenic massive sulfide deposits (VMSDs) and banded iron formations (BIFs) were formed by mixing of submarine hydrothermal fluids with local seawater. Therefore, the behaviors of various elements, especially of redox-sensitive elements, in altered submarine volcanic rocks, VMSDs and BIFs can be used to decipher the chemical evolution of the oceans and atmosphere. We have investigated the mineralogy and geochemistry of >500 samples of basalts from a 260m-long drill core section of Hole #1 of the Archean Biosphere Drilling Project (ABDP #1) in the Pilbara Craton, Western Australia. The core section is comprised of ~160 m thick Marble Bar Chert/Jasper Unit (3.46 Ga) and underlying, inter-bedded, and overlying submarine basalts. Losses/gains of 65 elements were quantitatively evaluated on the basis of their concentration ratios against the least mobile elements (Ti, Zr and Nb). We have recognized that mineralogical and geochemical characteristics of many of these samples are essentially the same as those of hydrothermally-altered modern submarine basalts and also those of altered volcanic rocks that underlie Phanerozoic VMSDs. The similarities include, but are not restricted to: (1) the alteration mineralogy (chlorite ± sericite ± pyrophyllite ± carbonates ± hematite ± pyrite ± rutile); (2) the characteristics of whole-rock δ18O and δ34S values; (3) the ranges of depletion and enrichment of Si, Al, Mg, Ca, K, Na, Fe, Mn, and P; (4) the enrichment of Ba (as sulfate); (5) the increases in Fe3+/Fe2+ ratios; (6) the enrichment of U; (7) the depletion of Cr; and (8) the negative Ce anomalies. Literature data

  7. Coping with volcanic hazards; a global perspective (United States)

    Tilling, R.I.


    Compared to some other natural hazards-such as floods, storms, earthquakes, landslides- volcanic hazards strike infrequently. However, in populated areas , even very small eruptions can wreak havoc and cause widespread devastation. For example, the 13 November 1985 eruption of Nevado del Ruiz in Colombia ejected only about 3 percent of the volume of ash produced during the 18 May 1980 eruption of Mount St. Helens. Yet, the mudflows triggered by this tiny eruption killed more than 25,000 people.

  8. Feasibility study on volcanic power generation system

    Energy Technology Data Exchange (ETDEWEB)



    Investigations were carried out to determine the feasibility of volcanic power generation on Satsuma Io Island. Earthquakes were studied, as were the eruptions of subaerial and submarine hot springs. Hydrothermal rock alteration was studied and electrical surveys were made. General geophysical surveying was performed with thermocameras and radiation monitoring equipment. In particular, the Toyoba mine was studied, both with respect to its hot spring and its subsurface temperatures.

  9. K-Ar ages of basalts from the Higashi-Matsuura district, northwestern Kyushu, Japan and regional geochronology of the Cenozoic alkaline volcanic rocks in eastern Asia

    International Nuclear Information System (INIS)

    Nakamura, Eizo; Campbell, I.H.; McDougall, I.


    Seven new K-Ar age determinations are presented on whole rock samples from alkaline and tholeiitic basalts of the Higashi-Matsuura district, northwestern Kyushu, Japan. Ages obtained range from 2.92 ± 0.03 Ma to 3.01 ± 0.04 Ma; these ages are essentially identical within analytical errors and yield an average age of 2.98 ± 0.03 Ma (Late Pliocene). When combined on an isochron type diagram the six Higashi-Matsuura samples give an age of 3.00 ± 0.03 Ma with the composition of nonradiogenic 40 Ar/ 36 Ar = 294.2 ± 2.0. The excellent age agreement of samples with different K contents and petrographic characteristics provides strong evidence that the tholeiitic and alkaline basalts were erupted for an extremely short period in the Higashi-Matsuura district. A basalt from Ogawashima Island yields a K-Ar age of 3.58 ± 0.04 Ma. This study and previously reported data support the hypothesis that alkaline volcanic activity in southwestern Japan commenced some 10 Ma ago and continued intermittently until recent times. Systematic variations of age and distribution of Cenozoic alkaline basalts are recognized in northeastern China, Korea and southwestern Japan. It is suggested that these variations are related to the initiation of 'mantle plumes' resulting from convection in the mantle wedge caused or controlled by subduction of the Kula and Pacific plates. (author)

  10. Model for Analysis of Energy Demand (MAED-2). User's manual

    International Nuclear Information System (INIS)


    The IAEA has been supporting its Member States in the area of energy planning for sustainable development. Development and dissemination of appropriate methodologies and their computer codes are important parts of this support. This manual has been produced to facilitate the use of the MAED model: Model for Analysis of Energy Demand. The methodology of the MAED model was originally developed by. B. Chateau and B. Lapillonne of the Institute Economique et Juridique de l'Energie (IEJE) of the University of Grenoble, France, and was presented as the MEDEE model. Since then the MEDEE model has been developed and adopted to be appropriate for modelling of various energy demand system. The IAEA adopted MEDEE-2 model and incorporated important modifications to make it more suitable for application in the developing countries, and it was named as the MAED model. The first version of the MAED model was designed for the DOS based system, which was later on converted for the Windows system. This manual presents the latest version of the MAED model. The most prominent feature of this version is its flexibility for representing structure of energy consumption. The model now allows country-specific representations of energy consumption patterns using the MAED methodology. The user can now disaggregate energy consumption according to the needs and/or data availability in her/his country. As such, MAED has now become a powerful tool for modelling widely diverse energy consumption patterns. This manual presents the model in details and provides guidelines for its application

  11. Model for Analysis of Energy Demand (MAED-2)

    International Nuclear Information System (INIS)


    The IAEA has been supporting its Member States in the area of energy planning for sustainable development. Development and dissemination of appropriate methodologies and their computer codes are important parts of this support. This manual has been produced to facilitate the use of the MAED model: Model for Analysis of Energy Demand. The methodology of the MAED model was originally developed by. B. Chateau and B. Lapillonne of the Institute Economique et Juridique de l'Energie (IEJE) of the University of Grenoble, France, and was presented as the MEDEE model. Since then the MEDEE model has been developed and adopted to be appropriate for modelling of various energy demand system. The IAEA adopted MEDEE-2 model and incorporated important modifications to make it more suitable for application in the developing countries, and it was named as the MAED model. The first version of the MAED model was designed for the DOS based system, which was later on converted for the Windows system. This manual presents the latest version of the MAED model. The most prominent feature of this version is its flexibility for representing structure of energy consumption. The model now allows country-specific representations of energy consumption patterns using the MAED methodology. The user can now disaggregate energy consumption according to the needs and/or data availability in her/his country. As such, MAED has now become a powerful tool for modelling widely diverse energy consumption patterns. This manual presents the model in details and provides guidelines for its application

  12. Model for Analysis of Energy Demand (MAED-2). User's manual

    International Nuclear Information System (INIS)


    The IAEA has been supporting its Member States in the area of energy planning for sustainable development. Development and dissemination of appropriate methodologies and their computer codes are important parts of this support. This manual has been produced to facilitate the use of the MAED model: Model for Analysis of Energy Demand. The methodology of the MAED model was originally developed by. B. Chateau and B. Lapillonne of the Institute Economique et Juridique de l'Energie (IEJE) of the University of Grenoble, France, and was presented as the MEDEE model. Since then the MEDEE model has been developed and adopted to be appropriate for modelling of various energy demand system. The IAEA adopted MEDEE-2 model and incorporated important modifications to make it more suitable for application in the developing countries, and it was named as the MAED model. The first version of the MAED model was designed for the DOS based system, which was later on converted for the Windows system. This manual presents the latest version of the MAED model. The most prominent feature of this version is its flexibility for representing structure of energy consumption. The model now allows country-specific representations of energy consumption patterns using the MAED methodology. The user can now disaggregate energy consumption according to the needs and/or data availability in her/his country. As such, MAED has now become a powerful tool for modelling widely diverse energy consumption patterns. This manual presents the model in details and provides guidelines for its application

  13. Volcanic alert system (VAS) developed during the 2011-2014 El Hierro (Canary Islands) volcanic process (United States)

    García, Alicia; Berrocoso, Manuel; Marrero, José M.; Fernández-Ros, Alberto; Prates, Gonçalo; De la Cruz-Reyna, Servando; Ortiz, Ramón


    The 2011 volcanic unrest at El Hierro Island illustrated the need for a Volcanic Alert System (VAS) specifically designed for the management of volcanic crises developing after long repose periods. The VAS comprises the monitoring network, the software tools for analysis of the monitoring parameters, the Volcanic Activity Level (VAL) management, and the assessment of hazard. The VAS presented here focuses on phenomena related to moderate eruptions, and on potentially destructive volcano-tectonic earthquakes and landslides. We introduce a set of new data analysis tools, aimed to detect data trend changes, as well as spurious signals related to instrumental failure. When data-trend changes and/or malfunctions are detected, a watchdog is triggered, issuing a watch-out warning (WOW) to the Monitoring Scientific Team (MST). The changes in data patterns are then translated by the MST into a VAL that is easy to use and understand by scientists, technicians, and decision-makers. Although the VAS was designed specifically for the unrest episodes at El Hierro, the methodologies may prove useful at other volcanic systems.

  14. Geothermal and volcanism in west Java (United States)

    Setiawan, I.; Indarto, S.; Sudarsono; Fauzi I, A.; Yuliyanti, A.; Lintjewas, L.; Alkausar, A.; Jakah


    Indonesian active volcanoes extend from Sumatra, Jawa, Bali, Lombok, Flores, North Sulawesi, and Halmahera. The volcanic arc hosts 276 volcanoes with 29 GWe of geothermal resources. Considering a wide distribution of geothermal potency, geothermal research is very important to be carried out especially to tackle high energy demand in Indonesia as an alternative energy sources aside from fossil fuel. Geothermal potency associated with volcanoes-hosted in West Java can be found in the West Java segment of Sunda Arc that is parallel with the subduction. The subduction of Indo-Australian oceanic plate beneath the Eurasian continental plate results in various volcanic products in a wide range of geochemical and mineralogical characteristics. The geochemical and mineralogical characteristics of volcanic and magmatic rocks associated with geothermal systems are ill-defined. Comprehensive study of geochemical signatures, mineralogical properties, and isotopes analysis might lead to the understanding of how large geothermal fields are found in West Java compared to ones in Central and East Java. The result can also provoke some valuable impacts on Java tectonic evolution and can suggest the key information for geothermal exploration enhancement.

  15. Orbital rhythms, monsoons, and playa lake response, Olduvai basin, Equatorial East Africa at 1.85-1.75 Ma (United States)

    Ashley, G. M.


    Wet-dry cycles in low latitudes are generally attributed to changes in solar radiation related to the 21 kyr tempo of orbital precession. Stronger insolation drives stronger summer monsoon maxima that increase precipitation and in closed basins produce larger lakes. However, a Plio-Pleistocene record from a closed rift-platform basin near the equator suggests that the obliquity (41 kyr) signal is also present. The 1.85-1.75 Ma sedimentary record deposited in the Olduvai basin, 3oN, reveals clear evidence of periodic expansion and contraction of paleolake Olduvai. The closed basin was 50 km wide and infilled by volcaniclastic material from Ngorongoro volcanic complex in several depositional environments.. A saline-alkaline lake expanded up to 15 km in width and deposited Mg-smectitic claystones. The lake clays in the central basin vary in clay mineralogy and the number of calcite crystal horizons reflecting compositional changes in the lake water. Lake expansions are recorded at the margins where lake clays are intercollated with deltaic and ephemeral fluvial sands and with lake margin wetland deposits. Marine dust records, off both west and east Africa, suggest that the precession signal (21kyr) dominated the climate until 2.8 Ma and the obliquity signal (41kyr) from 2.8 to 0.9 Ma (deMenocal, 1995). In contrast, the stratigraphic sequence for playa lake expansion at Olduvai, that is constrained by the tephra chronology (1.85-1.75 Ma) and paleomagnetic record, documents the combined effects of both obliquity and precession cycles.

  16. The 40Ar/39Ar and U/Pb dating of young rhyolites in the Kos-Nisyros vo