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Sample records for calderas utilizando intercambio

  1. Desarrollo de un nuevo tratamiento para la conservación de piedras con alto contenido en carbonatos utilizando la Tecnología de Resinas de Intercambio Iónico

    Directory of Open Access Journals (Sweden)

    Pérez-Alonso, M.

    2003-12-01

    de forma artificial del carbonato de calcio presente en piedras calcáreas en oxalato cálcico utilizando para ello la tecnología de intercambio iónico. La resina puesta en su forma oxalato debe ser puesta en contacto con la piedra mediante una solución conductora de iones, produciendo la formación de una microcapa cristalina de oxalato cálcico sobre la superficie de la piedra. Los resultados se han evaluado mediante espectroscopia FT-Raman. Los cristales formados inicialmente son CaC2O4 · 2H2O (weddellita que evoluciona parcialmente hacia la especie CaC2O4 · H2O (whewellita en función de las condiciones atmosféricas (humedad y temperatura.

  2. Reacciones de intercambio de carga

    Science.gov (United States)

    Errea, L. F.

    Se discute la validez de diversas metodologías y su aplicación al estudio de procesos de intercambio de carga electrónico entre iones y blancos atómicos y moleculares. Para energías de impacto entre 0.05 y 5 eV / amu se emplea el método cuántico de la Coordenada de Reacción Común (CRC). A mayores energías, se utiliza el método semiclásico iconal con un desarrollo de la función de onda dinámica en estados moleculares adiabáticos, modificados con un factor de traslación común (FTC). Estos estados pueden obtenerse con cálculos ab initio o empleando potenciales modelo. Cuando la ionización compite con la transferencia de carga, la inclusión de pseudoestados en estos desarrollos permite calcular simultáneamente las secciones eficaces de ambos procesos. Otra técnica utilizada es el método estadístico CTMC. En el tratamiento de colisiones ión-molécula (diatómica) contrastamos la aplicabilidad de distintos métodos, desde la llamada aproximación Franck-Condon hasta un desarrollo en estados vibrónicos, pasando por la aproximación súbita vibro-rotacional, obteniéndose secciones eficaces de captura electrónica total y a estados individuales, así como secciones de excitación vibracional a estados ligados y del continuo (disociación). En todos los casos es necesario calcular superficies de energía y los correspondientes acoplamientos dinámicos entre los estados. La aplicación de estos métodos permite determinar el grado de contaminación de los haces por estados metaestables en un experimento dado, el cambio en los resultados con diferentes isótopos, la importancia de procesos de doble captura, seguida de explosión culombiana, todo ello con precisión comparable a la de medidas experimentales, para sistemas de interés en distintos tipos de plasmas.

  3. Sociabilidad: Intercambio y transgresión

    OpenAIRE

    2004-01-01

    El autor presenta un análisis de las estructuras materiales y simbólicas desde las que se dice el intercambio y la transgresión, cuyo equilibrio funda la sociabilidad. Este se establece como un régimen nomológico de producción y pertenencia de sentido.

  4. intercambios lingüísticos

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    Liliana González Niño

    2005-01-01

    Full Text Available El presente artículo tiene por objetivo dar a conocer algunos avances de una investigación que se realiza en el marco de una experiencia pedagógica cuya finalidad es el intercambio de mensajes electrónicos entre estudiantes de la Licenciatura en Lenguas Modernas de la Pontificia Universidad Javeriana que aprenden el francés y estudiantes franceses de la universidad de Franche-Comté en Francia que aprenden el español. La implementación de un dispositivo de este tipo es un medio adecuado para que los estudiantes practicando la lengua de aprendizaje (francés – español mejoren su nivel de competencia comunicativa.

  5. PREFACE: Collapse Calderas Workshop

    Science.gov (United States)

    Gottsmann, Jo; Aguirre-Diaz, Gerardo

    2008-10-01

    Caldera-formation is one of the most awe-inspiring and powerful displays of nature's force. Resultant deposits may cover vast areas and significantly alter the immediate topography. Post-collapse activity may include resurgence, unrest, intra-caldera volcanism and potentially the start of a new magmatic cycle, perhaps eventually leading to renewed collapse. Since volcanoes and their eruptions are the surface manifestation of magmatic processes, calderas provide key insights into the generation and evolution of large-volume silicic magma bodies in the Earth's crust. Despite their potentially ferocious nature, calderas play a crucial role in modern society's life. Collapse calderas host essential economic deposits and supply power for many via the exploitation of geothermal reservoirs, and thus receive considerable scientific, economic and industrial attention. Calderas also attract millions of visitors world-wide with their spectacular scenic displays. To build on the outcomes of the 2005 calderas workshop in Tenerife (Spain) and to assess the most recent advances on caldera research, a follow-up meeting was proposed to be held in Mexico in 2008. This abstract volume presents contributions to the 2nd Calderas Workshop held at Hotel Misión La Muralla, Querétaro, Mexico, 19-25 October 2008. The title of the workshop `Reconstructing the evolution of collapse calderas: Magma storage, mobilisation and eruption' set the theme for five days of presentations and discussions, both at the venue as well as during visits to the surrounding calderas of Amealco, Amazcala and Huichapan. The multi-disciplinary workshop was attended by more than 40 scientist from North, Central and South America, Europe, Australia and Asia. Contributions covered five thematic topics: geology, geochemistry/petrology, structural analysis/modelling, geophysics, and hazards. The workshop was generously supported by the International Association of Volcanology and the Chemistry of The Earth's Interior

  6. Intercambio direccional en roseta – Suiza

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    Guisan, François

    1964-11-01

    Full Text Available This crossing, at Ecublens, Switzerland, involves five viaducts. The number of roads that the Lausanne-Berne motorway had to cross presented a difficult problem, since technical, aesthetic and economic questions had to be considered, all on a complex scale. As the soil was not suitable to support heavy structures, it was decided to build five viaducts, each providing a traffic route. Some of these viaducts cross each other at three levels. The viaducts consist of box girder sections, joined together to form continuous beams. The two central piles of each section are rigid, to withstand wind forces, and the others are hinged at the top and bottom. The sections are separated by dilatation joints, fitted with a metal attachment, which provides continuity for the pavement, and allows for a relative displacement of 16 cm. Some of the supports were placed on pile foundations, to overcome the weak bearing strength of the subsoil. One of the road sections did not have any rigid central supports, and this arrangement was chosen for aesthetic reasons.El intercambio direccional en roseta, de Ecublens (Suiza, está constituido por un conjunto de cinco viaductos. La multiplicidad de vías que debía salvar la autopista Lausana-Berna planteó un problema importante, ya que era preciso tener en cuenta factores de tipo técnico, en lo que respecta a las obras de fábrica; estéticos, en cuanto a armonía con el paisaje local, y económicos. Técnicamente, y teniendo en cuenta que las condiciones del terreno eran poco apropiadas para levantar obras pesadas, la solución adoptada consiste, en esencia, en cinco viaductos que constituyen otros tantos pasos, algunos de ellos intermedios, es decir, situados entre dos vías: una superior y otra inferior. Cada uno de los pasos se ha subdividido en varios tramos de viga cajón continua. Las dos pilas centrales de cada tramo son rígidas, para poder absorber los efectos del viento; las demás están articuladas en la

  7. Diseño de una caldera híbrida (energía solar y leña) para la obtención de aceite esencial de Hierba Luisa utilizando un concentrador Scheffler de 8 m2

    OpenAIRE

    Vidal Porta, Nicolás

    2014-01-01

    La presente tesis comprende el diseño de una caldera híbrida que utilice como fuente de energía la leña y la energía solar concentrada. Ésta deberá suministrar vapor a un equipo de destilación ya existente en las instalaciones del GRUPO de apoyo al sector rural de la Pontificia Universidad Católica del Perú. La caldera utilizará la potencia térmica entregada por un concentrador Scheffler de 8m2 de superficie también perteneciente al GRUPO de la PUCP que se encuentra en la localidad de Huyro, ...

  8. Burnout en profesores: Una perspectiva social del intercambio

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    WILMAR B. SCHAUFELI

    2005-01-01

    Full Text Available Se propone una perspectiva teórica sobre burnout en profesores, basada en principios de intercambio social. Se argumenta que el burnout se produce por una falta de reciprocidad; por un desajuste entre inversiones y resultados. Los profesores quemados se caracterizan por haber dado demasiado durante demasiado tiempo y por recibir demasiado poco a cambio. Según la teoría del intercambio social, la falta de reciprocidad podría desarrollarse a tres niveles: interpersonal (relación con estudiantes, a nivel de equipo (relaciones con compañeros, y a nivel organizacional (relación con la escuela. Estudios empíricos en profesores mostraron que el ajuste entre 'dar y recibir' se rompe, sobretodo en los niveles interpersonal y organizacional. Además, la falta de reciprocidad se asocia con distrés y conductas de abandono. Se observa un efecto genérico: cuando el equilibrio 'dar y recibir' se rompe se produce agotamiento emocional (síntoma corazón del burnout. Además, se observan efectos de las conductas de abandono específico para cada nivel de intercambio social: la falta de reciprocidad con los estudiantes provoca despersonalización (segunda dimensión del burnout; la falta de reciprocidad con los colegas acaba en conductas de abandono de los colegas; y la falta de reciprocidad con la escuela en abandono psicológico (reducido compromiso organizacional y conductual (absentismo por enfermedad de la escuela.

  9. Cuba. Intercambios socioculturales en el periodo aborigen con el Caribe

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    Alfredo Pérez Carratalá

    2010-07-01

    Full Text Available Se expresa la importancia que ha tenido el Caribe, no solo como componente físico-geográfico, sino también como área de intercambio de la biota, incluyendo los seres humanos. La ubicación geográfica del archipiélago cubano propició que fuera lugar de obligado paso o estancia de las comunidades aborígenes que habitaron el circumcaribe, en todos los períodos de desarrollo de los procesos migratorios en el área. En cuanto al intercambio sociocultural se entiende en sentido amplio del tema, es decir, lo tradicionalmente cultural, incluyendo las formas vivenciales de la cultura de los pueblos, donde lo cultural se convierte en vía y clave de realización de la intervención, donde los aspectos socioeconómicos en última instancia tienen un papel preponderante, por lo que comporta mucho más que la simple transferencia de materia prima y objetos.

  10. Nonstatistical dynamics on the caldera

    CERN Document Server

    Collins, Peter; Carpenter, Barry K; Ezra, Gregory S; Wiggins, Stephen

    2014-01-01

    We explore both classical and quantum dynamics of a model potential exhibiting a caldera: that is, a shallow potential well with two pairs of symmetry related index one saddles associated with entrance/exit channels. Classical trajectory simulations at several different energies confirm the existence of the `dynamical matching' phenomenon originally proposed by Carpenter, where the momentum direction associated with an incoming trajectory initiated at a high energy saddle point determines to a considerable extent the outcome of the reaction (passage through the diametrically opposing exit channel). By studying a `stretched' version of the caldera model, we have uncovered a generalized dynamical matching: bundles of trajectories can reflect off a hard potential wall so as to end up exiting predominantly through the transition state opposite the reflection point. We also investigate the effects of dissipation on the classical dynamics. In addition to classical trajectory studies, we examine the dynamics of quan...

  11. Nonstatistical dynamics on the caldera

    Energy Technology Data Exchange (ETDEWEB)

    Collins, Peter; Wiggins, Stephen, E-mail: stephen.wiggins@mac.com [School of Mathematics, University of Bristol, Bristol BS8 1TW (United Kingdom); Kramer, Zeb C., E-mail: zck3@cornell.edu; Ezra, Gregory S., E-mail: gse1@cornell.edu [Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853 (United States); Carpenter, Barry K., E-mail: CarpenterB1@cardiff.ac.uk [School of Chemistry, Cardiff University, Cardiff CF10 3AT (United Kingdom)

    2014-07-21

    We explore both classical and quantum dynamics of a model potential exhibiting a caldera: that is, a shallow potential well with two pairs of symmetry related index one saddles associated with entrance/exit channels. Classical trajectory simulations at several different energies confirm the existence of the “dynamical matching” phenomenon originally proposed by Carpenter, where the momentum direction associated with an incoming trajectory initiated at a high energy saddle point determines to a considerable extent the outcome of the reaction (passage through the diametrically opposing exit channel). By studying a “stretched” version of the caldera model, we have uncovered a generalized dynamical matching: bundles of trajectories can reflect off a hard potential wall so as to end up exiting predominantly through the transition state opposite the reflection point. We also investigate the effects of dissipation on the classical dynamics. In addition to classical trajectory studies, we examine the dynamics of quantum wave packets on the caldera potential (stretched and unstretched). These computations reveal a quantum mechanical analogue of the “dynamical matching” phenomenon, where the initial expectation value of the momentum direction for the wave packet determines the exit channel through which most of the probability density passes to product.

  12. Subsidence of ash-flow calderas: Relation to caldera size and magma-chamber geometry

    Science.gov (United States)

    Lipman, P.W.

    1997-01-01

    Diverse subsidence geometries and collapse processes for ash-flow calderas are inferred to reflect varying sizes, roof geometries, and depths of the source magma chambers, in combination with prior volcanic and regional tectonic influences. Based largely on a review of features at eroded pre-Quaternary calderas, a continuum of geometries and subsidence styles is inferred to exist, in both island-arc and continental settings, between small funnel calderas and larger plate (piston) subsidences bounded by arcuate faults. Within most ring-fault calderas, the subsided block is variably disrupted, due to differential movement during ash-flow eruptions and postcollapse magmatism, but highly chaotic piecemeal subsidence appears to be uncommon for large-diameter calderas. Small-scale downsag structures and accompanying extensional fractures develop along margins of most calderas during early stages of subsidence, but downsag is dominant only at calderas that have not subsided deeply. Calderas that are loci for multicyclic ash-flow eruption and subsidence cycles have the most complex internal structures. Large calderas have flared inner topographic walls due to landsliding of unstable slopes, and the resulting slide debris can constitute large proportions of caldera fill. Because the slide debris is concentrated near caldera walls, models from geophysical data can suggest a funnel geometry, even for large plate-subsidence calderas bounded by ring faults. Simple geometric models indicate that many large calderas have subsided 3-5 km, greater than the depth of most naturally exposed sections of intracaldera deposits. Many ring-fault platesubsidence calderas and intrusive ring complexes have been recognized in the western U.S., Japan, and elsewhere, but no well-documented examples of exposed eroded calderas have large-scale funnel geometry or chaotically disrupted caldera floors. Reported ignimbrite "shields" in the central Andes, where large-volume ash-flows are inferred to

  13. Las ganancias del comercio y el intercambio desigual en los modelos del comercio internacional

    OpenAIRE

    Francisco Martínez Soler; Andrei Martínez Finkelshtein

    2005-01-01

    Se examina el problema del intercambio desigual de trabajo entre países desarrollados y en desarrollo y su vinculación con las condiciones del comercio de beneficio mutuo. Para ello se utilizan los principales modelos teóricos del comercio internacional basado en las ventajas comparativas, y se amplía al caso de dos factores el concepto de relación de intercambio de trabajo derivada del comercio. Como resultado se concluye que el intercambio desigual es inherente al comercio entre países de d...

  14. Kuwae caldera (Vanuatu) and climate confusion

    Science.gov (United States)

    Nemeth, K.; Cronin, S. J.; White, J. D.

    2006-12-01

    A circular argument was developed and further propagated through a series of studies that link a major climate- modifying eruption in the 15th century with Kuwae caldera in Vanuatu (New Hebrides). Although the Kuwae submarine caldera structure is large (12x6 km) and comparable in size to other major calderas, our recent work reveals no evidence for high intensity eruptions that may have caused major climatic forcing at this time from this centre. Instead, the youngest volcanic strata, predominantly traceable on the adjacent islands including Tongoa, record a variety of small dacitic eruptions with locally restricted effects. The identified deposits are not more than 20 m thick within 2 km of the caldera, quickly pinch out, and do not overtop pre- caldera scoria cones that are only a few 10's of m higher. The wedge-like geometry of the pumice deposits on Tongoa, contained only in the low coastal areas appear to record multiple small-volume pyroclastic density currents. The depositional characteristics of the near-shoreline deposits, especially on neighbouring Laika Island are characteristic for shallow subaqueous deposition. The characteristics and dispersal of the preserved subaerial deposits imply eruptions were of small to moderate magnitude and intensity. An alternative possibility is that Kuwae caldera formed by a largely submarine eruption, in which a large, shallow magma body was erupted as underwater pyroclastic flows. This would reconcile a large-volume caldera with the absence of any evidence for a high-intensity eruption into the atmosphere. Partial escape to the atmosphere of some eruptive products from sites at the margins of the subsiding caldera could, in this scenario, have produced the small volume deposits from different source vents that are represented on the circum-caldera islands.

  15. Calderas and mineralization: volcanic geology and mineralization in the Chianti caldera complex, Trans-Pecos Texas

    Energy Technology Data Exchange (ETDEWEB)

    Duex, T.W.; Henry, C.D.

    1981-01-01

    This report describes preliminary results of an ongoing study of the volcanic stratigraphy, caldera activity, and known and potential mineralization of the Chinati Mountains area of Trans-Pecos Texas. Many ore deposits are spatially associated with calderas and other volcanic centers. A genetic relationship between calderas and base and precious metal mineralization has been proposed by some and denied by others. Steven and others have demonstrated that calderas provide an important setting for mineralization in the San Juan volcanic field of Colorado. Mineralization is not found in all calderas but is apparently restricted to calderas that had complex, postsubsidence igneous activity. A comparison of volcanic setting, volcanic history, caldera evolution, and evidence of mineralization in Trans-Pecos to those of the San Juan volcanic field, a major mineral producer, indicates that Trans-Pecos Texas also could be an important mineralized region. The Chianti caldera complex in Trans-Pecos Texas contains at least two calderas that have had considerable postsubsidence activity and that display large areas of hydrothermal alteration and mineralization. Abundant prospects in Trans-Pecos and numerous producing mines immediately south of the Trans-Pecos volcanic field in Mexico are additional evidence that ore-grade deposits could occur in Texas.

  16. Hydrothermal system of Long Valley caldera, California

    Energy Technology Data Exchange (ETDEWEB)

    Sorey, M.L.; Lewis, R.E.; Olmsted, F.H.

    1978-01-01

    The geologic and hydrologic setting of the hydrothermal system are described. The geochemical and thermal characteristics of the system are presented. A mathematical model of the Long Valley caldera is analyzed. (MHR)

  17. Origin of calderas: discriminating between collapses and explosions

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    Izumi Yokoyama

    2017-01-01

    Full Text Available Origins of calderas may differ according to their subsurface structure that may be characterized by high or low density deposits that may be observed as high or low gravity anomalies, respectively. In the Introduction, the pioneering work of Fouqué[1879] on Santorini caldera is referred to in relation to definition of calderas. First, our discussion is focused on four calderas that were seen forming during the period from 1815 (the Tambora eruption to 1991 (the Pinatubo eruption. Coincidently, these four calderas are all low-gravity-anomaly type. Their formation processes and subsurface structure are summarized by the existing data analyzed by various authors. These results are confirmed by results of drillings at some other calderas. Then, caldera formation of both types is discussed: High-gravity-anomaly-type calderas are expected to originate from subsidence of high-density ejecta into the summit magma reservoir. On the calderas of this type, the genetic eruptions believed to be accompanied by subsidences were not actually observed, and consequently three examples are mentioned only briefly. The low-gravity-anomaly-type calderas are discussed from standpoint of both the models of collapses and explosions. It is also emphasized that dynamic pressure ofexplosions is an important factor in the caldera formation, not only volume of the ejecta. To confirm the possibility that volcanic ejecta and edifices collapse into magma reservoirs, we discuss stress propagation from a depleted reservoir upward towards the Earth surface. Formation mechanisms of large calderas of this type are speculated; large calderas measuring about 20 km across may develop by successive merging of component calderas over a long period of times. A Kamchatka caldera under enlargement during the Holocene period is interpreted by successive merging of five component calderas.

  18. Content Analysis Schedule for Bilingual Education Programs: BICEP Intercambio de la Cultura.

    Science.gov (United States)

    Shore, Marietta Saravia; Nafus, Charles

    This content analysis schedule for BICEP Intercambio de la Cultura (San Bernardino, California), presents information on the history, funding, and scope of the project. Included are sociolinguistic process variables such as the native and dominant languages of students and their interaction. Information is provided on staff selection and the…

  19. Microearthquakes at Valles Caldera, New Mexico: Improved Detection and Location with Two Additional Caldera Stations

    Science.gov (United States)

    Roberts, P. M.; House, L. S.; Ten Cate, J. A.

    2015-12-01

    The Los Alamos Seismic Network (LASN) has operated for 43 years, providing data to locate more than 2,500 earthquakes in north-central New Mexico. Roughly 1-2 earthquakes are detected and located per month within about 150 km of Los Alamos, a total of over 900 from 1973 to present. LASN's primary purpose is to monitor seismicity close to the Los Alamos National Laboratory (LANL) for seismic hazards; monitoring seismicity associated with the nearby Valles Caldera is secondary. Until 2010 the network was focused on monitoring seismic hazards and comprised only 7 stations, all near LANL or in the nearby Jemez Mountains. Just one station—PER, installed in 1998—was close enough to Valles Caldera to be able to detect microearthquakes located in or near the caldera. An initial study of the data from station PER between 1998 and 2002 identified and located 13 events with magnitudes less than 0.5 using the single-station hodogram technique. Those events were all located south of the caldera within a few kilometers of PER. Recently, two new digital broadband stations were installed inside the caldera, one on a northeastern ring-fracture dome, station CDAB, and the other on a northwestern dome, station SAMT. Also, station PER was upgraded with digital broadband instrumentation. Thus, LASN now can detect and record microearthquakes as small as magnitude -1.5 near the caldera, and they can be located using multiple arrival times. Several recent events located near station SAMT on the caldera's ring fracture are the first that have been seen in that area. Additional events were recorded (by all three stations) and located in the area south of the caldera where the earlier hodogram-only events were located. These new multi-station event recordings allow a more quantitative assessment of the uncertainties in the initial single-station hodogram locations. Each event is located using multiple arrival times as well as the hodogram method at as many as three stations. Thus

  20. Obligaciones y relaciones de intercambio en el ámbito de la justicia penal

    Directory of Open Access Journals (Sweden)

    María José Sarrabayrouse Oliveira

    2009-02-01

    Full Text Available Trabajos clásicos de la antropología han reconocido a las relacionesde intercambio como producto de obligaciones constitutivas de lasrelaciones sociales. Contra aquello que podría observarse desde una miradasuperficial, las obligaciones, producto de las relaciones de intercambio, noatañen exclusivamente a las llamadas sociedades “primitivas” o propias dela antropología más tradicional, sino que se despliegan con toda su fuerza enespacios pertenecientes a las sociedades modernas en los que actúan comosostén de las relaciones sociales que allí se constituyen. A partir de esteplanteo inicial intentaré analizar un caso seleccionado que, en su calidad deextraordinario, permite entrever las relaciones que estructuran a la agenciajudicial.

  1. Intercambio virtual: Impacto en el desarrollo de las competencias lingüísticas e interculturales

    Directory of Open Access Journals (Sweden)

    Martha García Chamorro

    2009-01-01

    Full Text Available El desarrollo de competencias linguísticas e interculturales de los aprendices de una lengua extranjera es un objetivo central en la formación de ciudadanos del siglo XXI. Este artículo describe la experiencia de dos profesoras que realizaron un proyecto de intercambio virtual para incentivar el desarrollo de las competencias linguísticas e interculturales de dos grupos de estudiantes de países diferentes en idiomas y cultura. A través de la implementación de actividades de intercambio virtual se evidenció un desarrollo de estas competencias en los estudiantes participantes. Un componente crucial de esta experiencia fue la posibilidad de utilizar herramientas como el Skype y el WEBCt a través de las cuales los estudiantes pudieron trabajar con sus pares en la construcción de conocimiento.

  2. Buried caldera of mauna kea volcano, hawaii.

    Science.gov (United States)

    Porter, S C

    1972-03-31

    An elliptical caldera (2.1 by 2.8 kilometers) at the summit of Mauna Kea volcano is inferred to lie buried beneath hawaiite lava flows and pyroclastic cones at an altitude of approximately 3850 meters. Stratigraphic relationships indicate that hawaiite eruptions began before a pre-Wisconsin period of ice-cap glaciation and that the crest of the mountain attained its present altitude and gross form during a glaciation of probable Early Wisconsin age.

  3. California's restless giant: the Long Valley Caldera

    Science.gov (United States)

    Hill, David P.; Bailey, Roy A.; Hendley, James W.; Stauffer, Peter H.; Marcaida, Mae

    2014-01-01

    Scientists have monitored geologic unrest in the Long Valley, California, area since 1980. In that year, following a swarm of strong earthquakes, they discovered that the central part of the Long Valley Caldera had begun actively rising. Unrest in the area persists today. The U.S. Geological Survey (USGS) continues to provide the public and civil authorities with current information on the volcanic hazard at Long Valley and is prepared to give timely warnings of any impending eruption.

  4. Caldera rim collapse: A hidden volcanic hazard

    OpenAIRE

    Merle, Olivier; Michon, Laurent; Bachèlery, Patrick

    2008-01-01

    International audience; Following the emblematic flank collapse of Mount St Helens in 1981, numerous models of flank sliding have been proposed. These models have allowed to largely improve the understanding of mechanisms involved in such landslides, which represent a tremendous risk for populations living around volcanoes. In this article, a new mode of landslide formation, related to buried calderas, is described. The model emphasizes the paramount importance of the hidden ring fault that, ...

  5. Caldera processes and magma-hydrothermal systems continental scientific drilling program: thermal regimes, Valles caldera research, scientific and management plan

    Energy Technology Data Exchange (ETDEWEB)

    Goff, F.; Nielson, D.L. (eds.)

    1986-05-01

    Long-range core-drilling operations and initial scientific investigations are described for four sites in the Valles caldera, New Mexico. The plan concentrates on the period 1986 to 1993 and has six primary objectives: (1) study the origin, evolution, physical/chemical dynamics of the vapor-dominated portion of the Valles geothermal system; (2) investigate the characteristics of caldera fill and mechanisms of caldera collapse and resurgence; (3) determine the physical/chemical conditions in the heat transfer zone between crystallizing plutons and the hydrothermal system; (4) study the mechanism of ore deposition in the caldera environment; (5) develop and test high-temperature drilling techniques and logging tools; and (6) evaluate the geothermal resource within a large silicic caldera. Core holes VC-2a (500 m) and VC-2b (2000 m) are planned in the Sulphur Springs area; these core holes will probe the vapor-dominated zone, the underlying hot-water-dominated zone, the boiling interface and probable ore deposition between the two zones, and the deep structure and stratigraphy along the western part of the Valles caldera fracture zone and resurgent dome. Core hole VC-3 will involve reopening existing well Baca number12 and deepening it from 3.2 km (present total depth) to 5.5 km, this core hole will penetrate the deep-crystallized silicic pluton, investigate conductive heat transfer in that zone, and study the evolution of the central resurgent dome. Core hole VC-4 is designed to penetrate deep into the presumably thick caldera fill in eastern Valles caldera and examine the relationship between caldera formation, sedimentation, tectonics, and volcanism. Core hole VC-5 is to test structure, stratigraphy, and magmatic evolution of pre-Valles caldera rocks, their relations to Valles caldera, and the influences of regional structure on volcanism and caldera formation.

  6. Yellowstone and Long Valley - A Comparison of Two Restless Calderas

    Science.gov (United States)

    Hill, D. P.; Smith, R. B.

    2007-12-01

    Three large, silicic calderas in the conterminous United States have explosively erupted volumes > 300 km3 within in the last 2 million years -- Yellowstone caldera (Wyoming) Long Valley caldera (California) and the Vallez caldera (New Mexico) all located in extensional tectonic environments. All have shown varying levels of historic unrest. Pronounced unrest episodes at Yellowstone and Long Valley calderas over the past three decades stimulated extensive research on these two closely monitored calderas, and we explore some emerging similarities and differences. Yellowstone caldera is underlain by a long-lived (> 17 my) upper-mantle hot-spot that has fed a series of caldera-forming, extending to the southwest across southern Idaho to central Oregon including three caldera-forming eruptions from the Yellowstone caldera system in the last 2 my, the most recent at 600,000 ybp. It is marked by relatively low density and low seismic velocities extending to depths of at least 400 km and a regional topographic swell with elevations exceeding 2000 m. The extensive Yellowstone hydrothermal system has a thermal output of 5 GW. The most recent magmatic eruption dated at 70,000 ybp. By comparison, Long Valley caldera is underlain by a relatively modest "hot-spot", the locus of which appears to be influenced by a dilatational jog between the dextral Eastern California Shear Zone and the Walker Lane and westward delamination of the dense lithospheric root of the adjacent Sierra Nevada. The Long Valley system has fed multiple eruptions of over the past 4 my and a single caldera-forming eruption at 760,000 ybp. It is marked by a limited topographic swell but with the elevation of the caldera floor and adjacent basins comparable to the 2000-plus m elevation of the Yellowstone swell. Long Valley caldera hydrothermal system has a thermal output of 0.3 GW (including a 40 MW geothermal power plant). The most recent eruptions from the Long Valley Caldera- Mono Domes volcanic field

  7. The Chacana caldera complex in Ecuador

    Energy Technology Data Exchange (ETDEWEB)

    Hall, Minard L; Mothes, Patricia A [Instituto Geofisico, Escuela Politecnica Nacional, Quito (Ecuador)], E-mail: volcan_pete@yahoo.com

    2008-10-01

    The Chacana caldera, located immediately east of Quito, capital of Ecuador, forms the most-northern edifice of Ecuadoros rhyolite province. It is a 50X30 km Pleistocene structure that has remained active into historic times. Vitrophyres, welded tuffs, and ignimbrites of rhyolitic and dacitic composition constitute the outer flanks, meantime syngenetic breccias and tuffs, capped later by extensive dacite lava flows and basin sediments, filled the calderaos depression. A notable resurgence occurred that lifted quiet-water sediments to over 4000 m in elevation. The area has numerous hot springs, and little seismic activity.

  8. The Amazcala caldera, Queretaro, Mexico. Geology and geochronology

    Science.gov (United States)

    Aguirre-Díaz, Gerardo J.; López-Martínez, Margarita

    2001-11-01

    The Amazcala caldera is located 30 km NE of Querétaro City, near Amazcala, state of Querétaro. This caldera is the northernmost caldera within the central sector of the Mexican Volcanic Belt (MVB). It has a 11×14 km 2 elliptical shape, and was formed 7.3-6.6 Ma ago. All caldera products are rhyolites. The oldest caldera unit, the Ezequiel Montes pumice (EMP), is a widespread pumice fallout emplaced around 7.3 Ma ago. An isopach map of the EMP shows two dispersal axes, oriented to the SW and SE with respect to the caldera. The EMP is 5 m thick 40 km to the SW and 35 km to the SE of the caldera. An isopleth map of the EMP shows that pumice fragments increase in size toward the caldera, from 1 cm at 40 km to 25 cm near the caldera rim. The EMP is a regional stratigraphic marker. The Colón ignimbrite, dated at 7.3±0.5 Ma, is stratigraphically above the EMP. It consists of several ash-flow units interbedded with minor pumice fall lapilli and ash, with a minimum thickness of about 80 m at Colón. The caldera rim is occupied by several rhyolite lava domes and flows, some of which extend 10 km from the rim. These domes contain parts of fresh, aphyric obsidian. The last caldera event is an intracaldera rhyolitic dome near the NE rim at about 6.6 Ma. The dome is 4×2 km 2 and is elongated in the NE direction. The Amazcala caldera is 480 km from the Middle America Trench and represents the farthest inland caldera in the central sector of the MVB. Its age of 7.3-6.6 Ma indicates that it is the oldest caldera of the MVB so far reported. This confirms the general view that the volcanic activity of the MVB initiated at its northern margin, and then migrated southward in time.

  9. Elongate summit calderas as Neogene paleostress indicators in Antarctica

    Science.gov (United States)

    Paulsen, T.S.; Wilson, T.J.

    2007-01-01

    The orientations and ages of elongate summit calderas on major polygenetic volcanoes were compiled to document Miocene to Pleistocene Sh (minimum horizontal stress) directions on the western and northern flanks of the West Antarctic rift system. Miocene to Pleistocene summit calderas along the western Ross Sea show relatively consistent ENE long axis trends, which are at a high angle to the Transantarctic Mountain Front and parallel to the N77ºE Sh direction at Cape Roberts. The elongation directions of many Miocene to Pleistocene summit calderas in Marie Byrd Land parallel the alignment of polygenetic volcanoes in which they occur, except several Pleistocene calderas with consistent NNE to NE trends. The overall pattern of elongate calderas in Marie Byrd Land is probably due to a combination of structurally controlled orientations and regional stress fields in which Sh is oriented NNE to NE at a moderate to high angle to the trace of the West Antarctic rift system.

  10. Krakatau caldera deposits: revisited and verification by geophysical means

    Directory of Open Access Journals (Sweden)

    Izumi Yokoyama

    2014-10-01

    Full Text Available  One of the differences between volcanic craters and calderas is that the latter bottoms are flatways filled with caldera deposit with lower density in comparison to country rocks. The 1883 Krakatau eruption affords us important knowledge on caldera formation even if it was not observed with modern sophisticated instruments. First, volcanic activities of the Krakatau Islands before and after the 1883 eruption are reexamined: previous suppositions involving a caldera-forming eruption of the proto-Krakatau prior to 1883 proved to be unsupported by the bathymetric topographies and gravity anomalies on and around the Krakatau Islands. Then, Anak Krakatau is interpreted as a parasitic cone of the main Krakatau volcano. As supplementary knowledge to discussion of caldera deposits, the results of drillings at several calderas in Japan and Mexico are introduced. Mass deficiency of the caldera deposit at Krakatau caldera is estimated by the gravity anomaly observed there and converted to probable volume with suitable density. For quantitative examination of the subsurface structure beneath the Krakatau complex, spatial distributions of seismic S-wave attenuation and Vp/Vs ratios have been already studied by temporary seismological observations and their results have been published. The high ratios of Vp/Vs observed approximately at Krakatau caldera may be attributable to the caldera deposit that is low density and contain much water. As additional remarks, a zone having both the characters, S-wave attenuation and zones of relatively high Vp/Vs ratio, may be a probable magma reservoir centering at a depth of about 10 km.

  11. Caldera collapse at near-ridge seamounts: an experimental investigation

    Science.gov (United States)

    Coumans, Jason P.; Stix, John

    2016-10-01

    Collapse calderas are sub-circular volcanic depressions caused by subsidence of the magma reservoir roof during an eruption. Scaled physical models of caldera collapse using flat topography have been instrumental in investigating the spatial and temporal development of calderas, in particular, two distinctive sets of concentric ring faults, one reverse and one normal. More recent analog studies have investigated the effect of non-flat topography which alters the principle stress trajectories and resulting collapse structure. This work provides the basis for investigating how naturally scaled topographic loads may affect caldera collapse in relation to shallow magma reservoirs. The objective of this study is to understand how a near-ridge seamount affects caldera collapse from both a central and offset position as the seamount migrates above the magma reservoir as a result of plate motion. We utilize scaled analog models of caldera collapse in conjunction with three-dimensional (3D) laser scanning and digital particle image velocimetry (DPIV) to investigate caldera collapse dynamics at near-ridge seamounts. Experiments using a seamount cone positioned centrally above the magma reservoir result in (1) increased subsidence along the interior outward-dipping faults and (2) a preference to more symmetric collapse patterns as indicated by the subsidence profile and structure of the caldera relative to experiments with an offset cone. When the cone is offset, the collapse is asymmetric and trapdoor in nature, with the center of greatest subsidence displaced away from the region of largest topographic load. For these latter experiments, subsidence is focused where the roof is thinnest along an initial reverse fault, followed by a transition to an antithetic graben structure. The asymmetric collapse in the experiments results in a caldera with a tilted profile. Offset calderas at near-ridge seamounts are tilted towards the ridge axis, suggesting that they may have collapsed

  12. Geologic Map of the Valles Caldera, Jemez Mountains, New Mexico

    Science.gov (United States)

    Goff, F.; Gardner, J. N.; Reneau, S. L.; Kelley, S. A.; Kempter, K. A.; Lawrence, J. R.

    2011-12-01

    Valles caldera is famous as the type locality of large resurgent calderas (Smith and Bailey, 1968), the location of a classic 260-300 °C liquid-dominated geothermal system (Goff and Gardner, 1994), and the site of a long-lived late Pleistocene lake (Fawcett et al., 2011). We have published a detailed color geologic map of the Valles caldera and surrounding areas at 1:50,000 scale obtainable from New Mexico Bureau of Geology and Mineral Resources (geoinfo.nmt.edu/publications/maps/geologic/gm/79/). The new Valles map has been compiled from all or parts of nine 1:24,000 geologic maps completed between 2004 and 2008 (Bland, Cerro del Grant, Jarosa, Jemez Springs, Polvadera Peak, Redondo Peak, Seven Springs, Valle San Antonio, and Valle Toledo). Our map provides more detailed geology on the resurgent dome, caldera collapse breccias, post-caldera lava and tuff eruptions, intracaldera sedimentary and lacustrine deposits, and precaldera volcanic and sedimentary rocks than previous maps and incorporates recent stratigraphic revisions to the geology of the Jemez Mountains volcanic field. Three cross sections supported by surface geology, geophysical data and deep borehole logs (≤4500 m) show an updated view of the caldera interior, depict a modern interpretation of caldera collapse and resurgence, and provide caldera-wide subsurface isotherms (≤500 °C). A 30 page booklet included with the map contains extensive rock descriptions for 162 stratigraphic units and figures showing physiographic features, structural relations between Valles (1.25 Ma) and the earlier, comparably sized Toledo caldera (1.62 Ma), correlation charts of map units, and the distribution of pre- and post-caldera hydrothermal alteration styles, including recently documented zeolite-type alteration. Finally, the booklet includes a generalized model showing our interpretation of intracaldera structure and subjacent magma chambers, and relations of Valles to earlier Quaternary-Precambrian units.

  13. Intercambio intergeneracional: propuesta de Aprendizaje-Servicio en el aula de Educación Infantil

    OpenAIRE

    Nonell-Salvaña, Gloria

    2015-01-01

    Este Trabajo de Fin de Grado se centra en una propuesta de intervención basada en la metodología educativa del Aprendizaje-Servicio para el aula de cinco años del Segundo Ciclo de Educación Infantil. Se trata de una propuesta basada en el intercambio intergeneracional entre los alumnos y las personas mayores de una residencia cercana a la escuela. Para ello, se han diseñado dos bloques de actividades: el alumnado realizará cuatro talleres lúdicos para los abuelos y estos com...

  14. Intercambio local en el período ramésida

    OpenAIRE

    Zingarelli, Andrea Paula

    2015-01-01

    El estudio del intercambio interno en el período ramésida ha comenzado a ser abordado en los últimos años, como muestra la reciente publicación "Le commerce en Égypte ancienne", que reúne un conjunto de ponencias sobre el tema del comercio y revela el cambio de tendencia. La ausencia de investigaciones anteriores en esta temática obedeció no sólo a que los egiptólogos estaban en general más interesados en problemas de lingüística, arqueología,...

  15. El Estado Moderno y la sociedad de intercambio en la obra de Thomas Hobbes

    Directory of Open Access Journals (Sweden)

    Fernando Salazar Silva

    2007-01-01

    Full Text Available El soberano, como manifestación de la organización social, mas allá de expresar de un modo inevitable la seguridad de los hombres ante el desorden del "Estado natural", establece el origen de la sociedad de intercambio y la propiedad. El desarrollo de este proceso histórico, lejos de ser un acto espontáneo de los hombres como efecto de su propensión natural al cambio, es posible a partir de las condiciones generadas por el Leviatán.

  16. Taller de capacitación e intercambio en procesos de innovación rural

    Directory of Open Access Journals (Sweden)

    Veterinaria.org

    2008-01-01

    Full Text Available ResumenCon un rotundo éxito se celebró en Bayamo, el Taller de capacitación e intercambio en procesos de innovación rural, el día 7 de diciembre del 2007, organizado por el Órgano de Base “Jorge Dimitrov” de Bayamo, auspiciado por la Filial Granma del Consejo Científico de Veterinaria de Cuba. Se impartieron cuatro conferencias desarrolladas por prestigiosos investigadores que abordaron diversos temas de gran impacto e importancia en la ganadería de la provincia y el país.

  17. Hacia una critica interna de la teoría del intercambio desigual de Emmanuel

    OpenAIRE

    Garay S. Luis Jorge

    1980-01-01

    El presente ensayo constituye apenas una versión parcial y preliminar de un trabajo más extenso que el autor está desarrollando sobre la teoría del intercambio desigual de Emmanuel. Entendido así el carácter de éste, su objetivo se limita únicamente a estudiar los principales supuestos, inconsistencias y vicios teóricos y metodológicos implícitos en
    el "traslado" particular que Emmanuel realiza del esquema de precios de Marx al plano del comercio internacional. En otras palabras, e...

  18. Central San Juan caldera cluster: regional volcanic framework

    Science.gov (United States)

    Lipman, Peter W.

    2000-01-01

    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

  19. Evolution of deep collapse caldera: from structural to gravitational process

    Science.gov (United States)

    Geshi, N.; Acocella, V.; Ruch, J.

    2012-04-01

    We discuss the evolution of deep-subsiding caldera mainly controlled by gravitational process. Progress of caldera subsidence increases its subsidence/diameter ratio (S/D ratio). We investigate the surface features of calderas undergoing significant subsidence with regard to their diameter. First, we consider the evolution of the 2000 Miyakejima caldera, from double-concentric ring faults at earlier collapsing stages, to a gravitational-erosion dominant stage at a mature stage. When the topographic S/D approaches 0.33, the topographic S/D (hereafter S/Dt) becomes significantly different from the structural S/D (hereafter S/Ds), owing to the gravitational erosion on the caldera wall and accumulation of the debris on the floor. As collapse progresses, the peripheral block bounded by the inner reverse fault and outer normal fault extends and tilts towards the caldera center; it finally collapses towards the caldera floor and the double-ring faults disappeares. Subsidence of the caldera floor induces the gravitational erosion of the wall. This process increases the topographic diameter and the filling of the floor decreases the topographic depth. Consequently, the S/Dt decreases, while the continuous caldera subsidence increases the S/Ds. This evolution finds close similarities with the caldera collapses of Krakatau (1883), Katmai (1912), Fernandina (1968), Tolbachik (1975-76), Pinatubo (1991) and Dolomieu (2007). Analogue experiments mimic the observed variation, evolving from a depression controlled by the activity of the double-ring faults to that controlled by the gravitational slumping of the wall and sedimentation at the floor. The transition occurs for S/Dt ~0.34. These results show that the control on the shape of mature calderas (S/Ds>0.07) and approaching S/Dt=0.3 passes from a mainly structural to a mainly gravitational type. Both S/Dt and S/Ds are needed to describe the evolution of a collapse and the processes accompanying it. Evaluating the S/Dt and S

  20. Regional and local tectonics at Erta Ale caldera, Afar (Ethiopia)

    Science.gov (United States)

    Acocella, Valerio

    2006-10-01

    Erta Ale volcano lies along the on-shore Red Sea Rift (northern Afar, Ethiopia), separating the Nubia and Danakil plates. Erta Ale has a NNW-SSE elongated caldera, with a subvertical rim scarp, hosting a lava lake. Structural field work was aimed at defining the deformation pattern around the caldera. The caldera consists of along-rim and across-rim structures, resulting from local and regional (maximum extension ˜NE-SW) stress fields, respectively. These structures cross-cut each other at high angles, suggesting that the two stress fields remain distinct, each prevailing during rifting or caldera collapse. The local along-rim extensional fractures are gravity-driven structures that formed due to the retreat of the caldera wall after collapse, and are confined to the region of caldera subsidence. The across-rim structures are mainly located to the N and S of the caldera, where they form rift zones each accommodating a similar amount of extension (˜6.3 m), but displaying different trends and extension directions. Analogue models of interacting fractures are consistent with the Southern Rift being representative of the regional fault kinematics, while the Northern Rift is a local perturbation, resulting from the interaction between two right-stepping rift segments along the Erta Ale Range.

  1. Optimum geometry for boiler soot blowers nozzles; Geometria optima de toberas para deshollinadores de caldera

    Energy Technology Data Exchange (ETDEWEB)

    Espinoza Garza, Jesus; Garcia Tinoco, Guillermo J.; Martinez Flores, Jose Oscar [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)

    1989-12-31

    For boiler soot blowing converging-diverging nozzles are employed, whose function is to convert thermal energy of a gas into kinetic energy to remove the deposits that adhere to the heat exchanger surfaces. In this paper are described the experimental equipment and the methods for flow, dynamic pressure, discharge velocity and air expansion factor calculation in each nozzle, as a function of its design geometry, utilizing air from a five stage centrifugal compressor. The graphic analysis of the results, concludes that the most efficient nozzles are not the ones than develop the greatest velocity, but the ones of highest dynamic pressure at the outlet. The nozzle geometry that allows obtaining the maximum dynamic air pressure at the discharge is A{sub 2}/A{sub g}=1.3676 [Espanol] Para el deshollinado de calderas se utilizan las toberas convergentes-divergentes, cuya funcion es convertir la energia termica de un gas en energia cinetica para remover los depositos que se adhieren a las superficies de intercambio de calor. En este trabajo se describen el equipo experimental y los metodos de calculo para flujo, presion dinamica, velocidad a la descarga y factor de expansion del aire en cada tobera, como funcion de su geometria de diseno. Durante la experimentacion se evaluaron siete disenos diferentes de toberas, empleando aire de un compresor centrifugo de cinco etapas. Del analisis grafico de los resultados, se concluye que las toberas mas eficientes no son las que desarrollan mayor velocidad sino las de mayor presion dinamica de la salida. La geometria de tobera que permite obtener la maxima presion dinamica del aire a la descarga es A{sub 2}/A{sub g} = 1.3676.

  2. INTERCAMBIO COMERCIAL UNIÓN EUROPEA - COMUNIDAD ANDINA (1997-2007

    Directory of Open Access Journals (Sweden)

    MARÍA GUERRA

    2009-01-01

    Full Text Available El presente artículo, analiza los intercambios comerciales entre la Unión Europea (UE y la Comunidad Andina de Naciones (CAN, con especial énfasis en la aplicación del Sistema de Preferencias Generalizado (SPG, en el periodo 1994 - 2007. Como resultado, se evidencia que el SPG andino, como política europea de cooperación internacional, no ha cumplido satisfactoriamente los objetivos primordiales de su formulación, principalmente por el grado de asimetrías y disfunciones que ha presentado a lo largo de su aplicación. También se analizó la institucionalidad de la CAN y las características del intercambio comercial intrarregional y la ampliación de su mercado en el mismo período. Finalmente como metodología para la elaboración de dicha investigación, se utilizó la descripción y análisis crítico basado en el estudio de estadísticas de fuentes oficiales y Organismos Internacionales, así como de teorías referidas al tema.

  3. Stratigraphy of Reforma Caldera, Baja California Sur, Mexico

    Science.gov (United States)

    García Sánchez, L.; Macias, J. L.; Osorio, L. S.; Pola, A.; Avellán, D. R.; Arce, J. L.; Saucedo, R.; Sánchez, J. M.; García-Tenorio, F.; Cisneros, G.; Reyes-Agustín, G.; Cardona, S.; Jimenez, A.

    2015-12-01

    The Reforma caldera is located at ~35 km to the northwest of Santa Rosalía in the central part of the Baja California peninsula. It has 10 km in diameter and a maximum height of 1200 masl in the center and between 100 and 500 masl in its slopes. Reforma is within a tectonic zone affected by two fault systems: A NW-SE normal fault system linked to the opening of the Gulf of California, and a NNW-SSE and NW-SE strike-slip fault system associated with an active Riedel system. Reforma was built upon Cretaceous granites that outcrop at the caldera center, Miocene to Pliocene volcano-sedimentary rocks of the Comondú group, and Miocene marine sediments of the Santa Rosalía basin. On top of these rocks outcrop at least four submarine to subaerial ignimbrites interbedded with marine fossiliferous beds and the lower Pleistocene deposits associated to the Reforma caldera. These deposits are formed by a ignimbrite that shifts to different lithofacies that change gradually their welding, here dubbed basal, transitional, intermediate, and upper (all of then enriched in black fiammes), followed by a pumice-rich, white fiammes, and vitrophyre lithofacies, which are distributed around the 9 km wide caldera and have been associated to the caldera formation episode. Deposits related to post-caldera volcanism are andesite-basaltic lava flows erupted along the caldera rim through localized feeding dikes and andesitic and rhyolitic domes, and scoria cinder cones exposed inside and outside the caldera. On top of these deposits rest the middle Pleistocene Aguajito caldera deposits.

  4. Damping of power oscillations of exchange lines using a DC link; Amortecimento de oscilacoes de potencia de linhas de intercambio utilizando um elo de CC

    Energy Technology Data Exchange (ETDEWEB)

    Paccini, Rodrigo de O.; Custodio, Diogo T.; Kopcak, Igor; Costa, Vivaldo F. da [Universidade Estadual de Campinas (UNICAMP), SP (Brazil). Dept. de Sistemas de Energia Eletrica], Emails: rodrigo@dsee.fee.unicamp.br, totti@dsee.fee.unicamp.br, kopcak@dsee.fee.unicamp.br, vivaldo@dsee.fee.unicamp.br.

    2009-07-01

    This article presents a study that evaluates the effectiveness of a DC link in order to damp power oscillations, of inter area exchange, under small disturbance conditions, operating with Automatic Control Generation. The DC link was represented by a power injection model included the Sensitivity Power Model. Through this representation, the DC link was inserted in the block diagram, modeled as an injection power in the bars terminals in the net active and reactive, closing a new power balance at every instant. It was also designed a controller for damping power oscillations (POD-Power Oscillation Damping Controller) for modulation the power of the DC link and, therefore, insertion of additional damping in a frequency oscillations of exchange lines. The results confirm that the DC link has a great potential for maintaining the damping of oscillations frequency so inter area when equipped with POD controllers.

  5. Magma storage in a strike-slip caldera.

    Science.gov (United States)

    Saxby, J; Gottsmann, J; Cashman, K; Gutiérrez, E

    2016-07-22

    Silicic calderas form during explosive volcanic eruptions when magma withdrawal triggers collapse along bounding faults. The nature of specific interactions between magmatism and tectonism in caldera-forming systems is, however, unclear. Regional stress patterns may control the location and geometry of magma reservoirs, which in turn may control the spatial and temporal development of faults. Here we provide new insight into strike-slip volcano-tectonic relations by analysing Bouguer gravity data from Ilopango caldera, El Salvador, which has a long history of catastrophic explosive eruptions. The observed low gravity beneath the caldera is aligned along the principal horizontal stress orientations of the El Salvador Fault Zone. Data inversion shows that the causative low-density structure extends to ca. 6 km depth, which we interpret as a shallow plumbing system comprising a fractured hydrothermal reservoir overlying a magmatic reservoir with vol% exsolved vapour. Fault-controlled localization of magma constrains potential vent locations for future eruptions.

  6. Magma storage in a strike-slip caldera

    Science.gov (United States)

    Saxby, J.; Gottsmann, J.; Cashman, K.; Gutiérrez, E.

    2016-07-01

    Silicic calderas form during explosive volcanic eruptions when magma withdrawal triggers collapse along bounding faults. The nature of specific interactions between magmatism and tectonism in caldera-forming systems is, however, unclear. Regional stress patterns may control the location and geometry of magma reservoirs, which in turn may control the spatial and temporal development of faults. Here we provide new insight into strike-slip volcano-tectonic relations by analysing Bouguer gravity data from Ilopango caldera, El Salvador, which has a long history of catastrophic explosive eruptions. The observed low gravity beneath the caldera is aligned along the principal horizontal stress orientations of the El Salvador Fault Zone. Data inversion shows that the causative low-density structure extends to ca. 6 km depth, which we interpret as a shallow plumbing system comprising a fractured hydrothermal reservoir overlying a magmatic reservoir with vol% exsolved vapour. Fault-controlled localization of magma constrains potential vent locations for future eruptions.

  7. Determinantes del intercambio directo de drogas ilegales a pequeña escala en Cali

    Directory of Open Access Journals (Sweden)

    Bustamante Amaya Christian David

    2012-09-01

    Full Text Available Este documento centra su análisis en el estudio de los determinantes que explican el intercambio directo de drogas ilegales a pequeña escala en la ciudad de Cali, a partir de la estimación de modelos de datos de conteo. Se verifica el cumplimiento de los supuestos teóricos de la elección racional de los individuos que son esbozados en la economía del crimen. Los resultados del modelo sugieren que si un expendedor considera su actividad como riesgosa, reduce en una significativa cantidad el número de horas dedicadas al expendio. Por otra parte, el precio de un cigarrillo de marihuana afecta negativamente el número de veces que un individuo consume al día; no obstante, la magnitud del efecto para esta variable denota el alto grado de inelasticidad al precio que tiene el consumo de esta droga.

  8. Hacia una critica interna de la teoría del intercambio desigual de Emmanuel

    Directory of Open Access Journals (Sweden)

    Garay S. Luis Jorge

    1980-12-01

    Full Text Available El presente ensayo constituye apenas una versión parcial y preliminar de un trabajo más extenso que el autor está desarrollando sobre la teoría del intercambio desigual de Emmanuel. Entendido así el carácter de éste, su objetivo se limita únicamente a estudiar los principales supuestos, inconsistencias y vicios teóricos y metodológicos implícitos en
    el "traslado" particular que Emmanuel realiza del esquema de precios de Marx al plano del comercio internacional. En otras palabras, el análisis aquí incluido corresponde más a lo que en la literatura se denomina una crítica interna que a una crítica externa de la teoría de intercamhio desigual de Emmanuel.

  9. Cooperación e intercambio de conocimiento en redes inter-organizativas informales

    Directory of Open Access Journals (Sweden)

    Carlos Martin-Rios

    2013-06-01

    Full Text Available El presente artículo explora el papel que juegan las redes informales de colaboración entre empresas para el intercambio de conocimiento. Para ello, se reportan los resultados de un estudio empírico llevado a cabo con una muestra de empresas localizadas en un campus tecnológico gestionado por una universidad que constituyen una red completa inter-organizacional. El estudio presenta evidencia sobre el papel que desempeñan las relaciones informales en el desarrollo de redes de conocimiento como vehículo para la transferencia de conocimiento tecnológico, de mercado y de gestión empresarial.

  10. Submarine Volcanic Morphology of Santorini Caldera, Greece

    Science.gov (United States)

    Nomikou, P.; Croff Bell, K.; Carey, S.; Bejelou, K.; Parks, M.; Antoniou, V.

    2012-04-01

    Santorini volcanic group form the central part of the modern Aegean volcanic arc, developed within the Hellenic arc and trench system, because of the ongoing subduction of the African plate beneath the European margin throughout Cenozoic. It comprises three distinct volcanic structures occurring along a NE-SW direction: Christianna form the southwestern part of the group, Santorini occupies the middle part and Koloumbo volcanic rift zone extends towards the northeastern part. The geology of the Santorini volcano has been described by a large number of researchers with petrological as well as geochronological data. The offshore area of the Santorini volcanic field has only recently been investigated with emphasis mainly inside the Santorini caldera and the submarine volcano of Kolumbo. In September 2011, cruise NA-014 on the E/V Nautilus carried out new surveys on the submarine volcanism of the study area, investigating the seafloor morphology with high-definition video imaging. Submarine hydrothermal vents were found on the seafloor of the northern basin of the Santorini caldera with no evidence of high temperature fluid discharges or massive sulphide formations, but only low temperature seeps characterized by meter-high mounds of bacteria-rich sediment. This vent field is located in line with the normal fault system of the Kolumbo rift, and also near the margin of a shallow intrusion that occurs within the sediments of the North Basin. Push cores have been collected and they will provide insights for their geochemical characteristics and their relationship to the active vents of the Kolumbo underwater volcano. Similar vent mounds occur in the South Basin, at shallow depths around the islets of Nea and Palaia Kameni. ROV exploration at the northern slopes of Nea Kameni revealed a fascinating underwater landscape of lava flows, lava spines and fractured lava blocks that have been formed as a result of 1707-1711 and 1925-1928 AD eruptions. A hummocky topography at

  11. Geology and structure of the Malpaso caldera and El Ocote ignimbrite, Aguascalientes, Mexico

    Science.gov (United States)

    Nieto-Obregón, Jorge; Aguirre-Díaz, Gerardo

    2008-10-01

    A new caldera, named Malpaso, is reported west of the city of Aguascalientes, Mexico. The Malpaso caldera is a volcano-tectonic depression, highly fractured and faulted, and was filled by voluminous pyroclastic products related to the caldera collapse. Due to these characteristics it as a graben caldera. It is truncated by younger normal faults of the Calvillo and Aguascalientes grabens. In this work we present a summary of the geologic and structural observations on this caldera, as well as a description of the main caldera product, the high-grade El Ocote ignimbrite.

  12. Reconstruction of caldera collapse and resurgence processes in the offshore sector of the Campi Flegrei caldera (Italy)

    Science.gov (United States)

    Steinmann, Lena; Spiess, Volkhard; Sacchi, Marco

    2015-04-01

    Large collapse calderas are associated with exceptionally explosive volcanic eruptions, which are capable of triggering a global catastrophe second only to that from a giant meteorite impact. Therefore, active calderas have attracted significant attention in both scientific communities and governmental institutions worldwide. One prime example of a large collapse caldera can be found in southern Italy, more precisely in the northern Bay of Naples within the Campi Flegrei Volcanic Area. The Campi Flegrei caldera covers an area of approximately 200 km² defined by a quasi-circular depression, half onland, half offshore. It is still under debate whether the caldera formation was related to only one ignimbritic eruption namely the Neapolitan Yellow Tuff (NYT) eruption at 15 ka or if it is a nested-caldera system related to the NYT and the Campanian Ignimbrite eruption at 39 ka. During the last 40 years, the Campi Flegrei caldera has experienced episodes of unrest involving significant ground deformation and seismicity, which have nevertheless not yet led to an eruption. Besides these short-term episodes of unrest, long-term ground deformation with rates of several tens of meters within a few thousand years can be observed in the central part of the caldera. The source of both short-term and long-term deformation is still under debate and possibly related to a shallow hydrothermal system and caldera resurgence attributed to a deeper magma chamber, respectively. Understanding the mechanisms for unrest and eruptions is of paramount importance as a future eruption of the Campi Flegrei caldera would expose more than 500,000 people to the risk of pyroclastic flows. This study is based on a dense grid (semi-3D) of high-resolution multi-channel seismic profiles acquired in the offshore sector of the Campi Flegrei caldera. The seismic lines show evidence for the escape of fluids and/or gases along weak zones such as faults, thereby supporting the existence of a hydrothermal

  13. Scaling properties of planetary calderas and terrestrial volcanic eruptions

    Directory of Open Access Journals (Sweden)

    L. Sanchez

    2012-11-01

    Full Text Available Volcanism plays an important role in transporting internal heat of planetary bodies to their surface. Therefore, volcanoes are a manifestation of the planet's past and present internal dynamics. Volcanic eruptions as well as caldera forming processes are the direct manifestation of complex interactions between the rising magma and the surrounding host rock in the crust of terrestrial planetary bodies. Attempts have been made to compare volcanic landforms throughout the solar system. Different stochastic models have been proposed to describe the temporal sequences of eruptions on individual or groups of volcanoes. However, comprehensive understanding of the physical mechanisms responsible for volcano formation and eruption and more specifically caldera formation remains elusive. In this work, we propose a scaling law to quantify the distribution of caldera sizes on Earth, Mars, Venus, and Io, as well as the distribution of calderas on Earth depending on their surrounding crustal properties. We also apply the same scaling analysis to the distribution of interevent times between eruptions for volcanoes that have the largest eruptive history as well as groups of volcanoes on Earth. We find that when rescaled with their respective sample averages, the distributions considered show a similar functional form. This result implies that similar processes are responsible for caldera formation throughout the solar system and for different crustal settings on Earth. This result emphasizes the importance of comparative planetology to understand planetary volcanism. Similarly, the processes responsible for volcanic eruptions are independent of the type of volcanism or geographical location.

  14. Science guide for the Long Valley Caldera deep hole

    Energy Technology Data Exchange (ETDEWEB)

    Rundle, J.B.; Eichelberger, J.C. (eds.)

    1989-05-01

    The Magma Energy Program of the US Department of Energy, Geothermal Technology Division, is planning to begin drilling a deep (6 km) exploration well in Long Valley Caldera, California, in September 1988. The location of the well is in the central part of the caldera, coincident with a large number of shallow (5-7 km) geophysical anomalies identified through many independent investigations. Results from the hole will permit the following: direct investigation of the geophysical anomalies interpreted to be magma; investigation of the patterns and conditions of deep fluid circulation and heat transport below the caldera floor; determination of the amount of collapse and subsequent resurgence of the central portion of Long Valley caldera; and determination of the intrusion history of the central plutonic complex beneath the caldera, and establishment of the relationship of intrusive to eruptive events. The hole will thus provide a stringent test of the hypothesis that magma is still present within the central plutonic complex. If the interpretation of geophysical anomalies is confirmed, the hole will provide the first observations of the environment near a large silicic magma chamber. 80 refs., 7 figs., 2 tabs.

  15. Carbonatite ring-complexes explained by caldera-style volcanism.

    Science.gov (United States)

    Andersson, Magnus; Malehmir, Alireza; Troll, Valentin R; Dehghannejad, Mahdieh; Juhlin, Christopher; Ask, Maria

    2013-01-01

    Carbonatites are rare, carbonate-rich magmatic rocks that make up a minute portion of the crust only, yet they are of great relevance for our understanding of crustal and mantle processes. Although they occur in all continents and from Archaean to present, the deeper plumbing system of carbonatite ring-complexes is usually poorly constrained. Here, we show that carbonatite ring-complexes can be explained by caldera-style volcanism. Our geophysical investigation of the Alnö carbonatite ring-complex in central Sweden identifies a solidified saucer-shaped magma chamber at ~3 km depth that links to surface exposures through a ring fault system. Caldera subsidence during final stages of activity caused carbonatite eruptions north of the main complex, providing the crucial element to connect plutonic and eruptive features of carbonatite magmatism. The way carbonatite magmas are stored, transported and erupt at the surface is thus comparable to known emplacement styles from silicic calderas.

  16. Modes and times of caldera resurgence: The Ischia Caldera, Italy, from high-precision archaeomagnetic dating

    Science.gov (United States)

    Vezzoli, Luigina; Principe, Claudia; Malfatti, Jonas; Arrighi, Simone; Tanguy, Jean-Claude; Le Goff, Maxime

    2009-10-01

    Ischia is a well exposed and densely populated late Quaternary caldera in the Campanian magmatic province of Italy. Ischia Caldera experienced an average uplift rate of 3.3 cm/year in the last ca. 30 ka and is still actively resurging. During the last 10 ka, coeval with the resurgence, a volcanic field of alkali-trachytic to trachyandesitic lava domes, lava flows, tuff and scoria rings, and pumice cones developed, mainly on the eastern sector of the caldera, along both resurgence-related faults and regional NNW- and NE-striking faults. In order to improve both our understanding of the recent volcanic history and the evaluation of future risks on Ischia Island, a high-precision archaeomagnetic dating method was applied to the products of 12 volcanic centres with probable age Ischia volcanism occurred in five periods separated by phases of quiescence and coeval with earthquake and landslide events. This fact suggests a pulsating mode of uplifting and deformations of the Ischia resurgence. During the two oldest periods of activity (7200-6800 BC and 4100-2300 BC), resurgence probably produced a dome-shaped structure. Location and geometry of vents suggest the occurrence of magma uprise along the fractures produced by bending of the overburden crustal block. Most of magma was emplaced as intrusions at the interior of the resurgent block, whereas volcanism was represented by very viscous, differentiated, and crystallized lavas that emplaced as domes and high aspect-ratio flows. The resurgent dome caused recurrent lateral collapses that removed about 2.5 km 3 of rocks. During the three youngest periods of activity (1800-1000 BC; 650 BC -355 AD; and 1302 AD), resurgence affected a fault-bounded, asymmetric block. This resulted from both (a) hydrostatic rebound of the crustal block after removal of material involved into huge slope instability triggering an increase in uplift rate, and (b) new influxes of less evolved magma batches into the shallow reservoir that, in turn

  17. Magmatic evolution of the Ilopango Caldera, El Salvador, Central America

    Science.gov (United States)

    Zezin, D.; Mann, C. P.; Hernández, W.; Stix, J.

    2010-12-01

    The Ilopango caldera (16 x 13 km) is an active, long-lived magmatic system, erupting voluminous amounts of pyroclastic material numerous times over the course of its evolution. The caldera is presently water filled and the most recent activity is a dome growth event in 1880. Established age constraints from extracaldera pyroclastic sequences, indicate caldera forming events occur ~ every 10,000 years over the last 40,000 years. The most recent pyroclastic eruption (TBJ) is constrained to A.D. 429 erupting 70 km3 DRE of pyroclastic material. We combine major element and trace element chemistry with 40Ar/39Ar age constraints of the intracaldera domes and intracaldera pyroclastic deposits to extent the caldera history. The intracaldera domes are andesitic to rhyolitic in composition (57 - 76 wt. % SiO2), some with basaltic enclaves (54 wt. % SiO2) and pyroclastic units observed inside the caldera (San Agustín Pumice Breccia) are dacitic to rhyolitic in composition (69 -75 wt. % SiO2). Formation of an intracaldera andesitic dome at 359±7.9 ka provides a minimum age of caldera formation and extends the caldera history back ~ 320 ka years. The variable composition of the intracaldera domes, the presence of mafic enclaves in the dome lavas, mafic clasts in the TB4 plinian fall, mafic banding in the TB3 and TB2, attest to the obvious involvement of a more mafic magma The highly evolved compositions of the pyroclastic units and the volume of erupted material, point towards a large evolving magma reservoir at depth. The mafic magma may replenish the subsurface reservoir and act as a catalyst for volcanic eruption. The presence of an intracaldera lake, the regularity with which the volcano erupts and the presence of a more mafic magma are the ingredients for a catastrophic disaster. The Ilopango caldera, located 10 km to the east of the capital city of San Salvador (~ 1.5 million people) poses a threat both locally and globally as demonstrated 1600 years ago as it

  18. Workshop on recent research in the Valles caldera

    Energy Technology Data Exchange (ETDEWEB)

    Heiken, G. (comp.)

    1985-02-01

    Over the last 5 years, there has been increased interest in the geology of the Jemez Mountains volcanic field, New Mexico. Of special interest is the Toledo-Valles caldera complex, which is targeted for research coring as part of the Continental Scientific Drilling Program. The general topics covered in this workshop were (1) hydrothermal systems and rock-water interactions, (2) volcanology and structural framework of the Jemez volcanic field, (3) determining the presence or absence of melt below the Valles caldera, and (4) deep coring and drilling technology. Separate abstracts were prepared for each presentation.

  19. El sistema de alternancia de turnos en los intercambios sincrónicos mediatizados por ordenador

    Directory of Open Access Journals (Sweden)

    Cristina Vela Delfa

    2011-09-01

    Full Text Available El objetivo de este artículo es el estudio de las interacciones de tipo sincrónico mediatizadas por ordenador, es decir, las conversaciones electrónicas desarrolladas con aplicaciones de chat o mensajería instantánea. Examinamos los conceptos manejados por el análisis de la conversación en el marco de la etnometodología con el objetivo de determinar la idoneidad de su aplicación a este tipo de interacciones. A partir de esta reflexión observamos que tales intercambios manifiestan propiedades estructurales específicas que afectan de manera directa a la gestión de los turnos de palabra. Los solapamientos entre turnos son constantes, ya que la persistencia del texto escrito permite que en cualquier momento opere la autoselección. Además, la necesidad de ostentar la presencia conversacional, que solo resulta posible con la publicación en pantalla de las contribuciones, lleva a los interlocutores a desarrollar estrategias compensatorias como, por ejemplo, la segmentación de las intervenciones. Todo ello contribuye a la ruptura de los pares de adyacencia cuya relación prioriza la relevancia informativa frente a la contigüidad estructural.

  20. Un sistema de intercambio híbrido: el mercado/tianguis La Purísima, Tehuacán-Puebla, México

    OpenAIRE

    Ernesto Licona Valencia

    2014-01-01

    El texto concibe al mercado-tianguis como una institución económica en la que se entremezclan varias formas de intercambio de bienes formando un sistema híbrido predominantemente monetario. Se describen etnográficamente los intercambios para revelar que los hechos económicos están mediados por los rasgos socioculturales de los sujetos, cuya función es fundamentalmente económica.

  1. Application of the Gauss theorem to the study of silicic calderas: The calderas of La Primavera, Los Azufres, and Los Humeros (Mexico)

    Science.gov (United States)

    Campos-Enríquez, J. O.; Domínguez-Méndez, F.; Lozada-Zumaeta, M.; Morales-Rodríguez, H. F.; Andaverde-Arredondo, J. A.

    2005-10-01

    We explored applications (including limitations) of Gauss's theorem to the study of silicic calderas. First it enables us to determine the mass deficiency from calderas. Mass deficiency itself has also other potential applications. It enables to make qualitative comparisons between calderas. We can use the mass deficiency to test, in a quick way and as a preliminary step to a formal gravity inversion, for the feasibility of caldera types of simple geometry (i.e., piston subsidence and funnel models). This application can be done in a straightforward way, once the mass deficiency has been determined. For this purpose the mass deficiency is converted to the volume of material missing at the caldera. Subsequently, for example, this volume and the respective caldera diameter enable us to estimate the height of the cylinder fitting the piston subsidence model. If the obtained parameters are congruent with the known geology and geophysical information then the model may be considered further in the inversion of the gravity data for the detailed structure. Other simple models (i.e., the funnel model) can also be analyzed in this way. In particular, when working with a piston subsidence caldera type, the Gauss theorem enables us to estimate the caldera collapse (very difficult to obtain based on geologic information alone). These possible uses of Gauss's theorem are illustrated with the calderas of La Primavera, Los Azufres, and Los Humeros caldera (Mexico). The obtained mass deficiency from these calderas follow the linear mass deficiency-diameter trend observed for other calderas. In particular, because of their diameters and mass deficiencies, La Primavera and Krakatau calderas can be considered equiparable. This comparison is of the most importance considering that La Primavera is located in the neighbourhood of a metropolis (Guadalajara City). Since geophysical studies have already established a piston subsidence model for these calderas, we assessed Gauss's theorem

  2. Igneous evolution of a complex laccolith-caldera, the Solitario, Trans-Pecos Texas: Implications for calderas and subjacent plutons

    Science.gov (United States)

    Henry, C.D.; Kunk, M.J.; Muehlberger, W.R.; McIntosh, W.C.

    1997-01-01

    The Solitario is a large, combination laccolith and caldera (herein termed "laccocaldera"), with a 16-km-diameter dome over which developed a 6 x 2 km caldera. This laccocaldera underwent a complex sequence of predoming sill, laccolith, and dike intrusion and concurrent volcanism; doming with emplacement of a main laccolith; ash-flow eruption and caldera collapse; intracaldera sedimentation and volcanism; and late intrusion. Detailed geologic mapping and 40Ar/39Ar dating reveal that the Solitario evolved over an interval of approximately 1 m.y. in three distinct pulses at 36.0, 35.4, and 35.0 Ma. The size, duration, and episodicity of Solitario magmatism are more typical of large ash-flow calderas than of most previously described laccoliths. Small volumes of magma intruded as abundant rhyolitic to trachytic sills and small laccoliths and extruded as lavas and tuffs during the first pulse at 36.0 Ma. Emplacement of the main laccolith, doming, ash-flow eruption, and caldera collapse occurred at 35.4 Ma during the most voluminous pulse. A complex sequence of debris-flow and debris-avalanche deposits, megabreccia, trachyte lava, and minor ash-flow tuff subsequently filled the caldera. The final magmatic pulse at 35.0 Ma consisted of several small laccoliths or stocks and numerous dikes in caldera fill and along the ring fracture. Solitario rocks appear to be part of a broadly cogenetic, metaluminous suite. Peralkaline rhyolite lava domes were emplaced north and west of the Solitario at approximately 35.4 Ma, contemporaneous with laccolith emplacement and the main pulse in the Solitario. The spatial and temporal relation along with sparse geochemical data suggest that the peralkaline rhyolites are crustal melts related to the magmatic-thermal flux represented by the main pulse of Solitario magmatism. Current models of laccolith emplacement and evolution suggest a continuum from initial sill emplacement through growth of the main laccolith. Although the Solitario

  3. Vesuvius, the Tengger Mountains and the problem of calderas

    NARCIS (Netherlands)

    Escher, B.G.

    1926-01-01

    Until recently there was no good general map of the Tengger Mountains, so that in 1914 F. von Wolff (bibl. 1) in his work „Der Vulkanismus”, vol. I, p. 510—511, gives a reproduction of Pr. Junghuhn's map of 1844. For a volcanic district that has frequently been used as an example of a caldera and ha

  4. Potential Hazards of Eruptions around the Tianchi Caldera Lake, China

    Institute of Scientific and Technical Information of China (English)

    WEI Haiquan; HONG Hanjing; R.S.J. SPARKS; J.S. WALDER; HAN Bin

    2004-01-01

    Since the eruption of the Tianchi volcano about 1000 years ago, there have been at least 3 to 5 eruptions of small to moderate size. In addition, hazardous avalanches, rock falls and debris flows have occurred during periods between eruptions. A future eruption of the Tianchi volcano is likely to involve explosive interaction between magma and the caldera lake. The volume of erupted magma is almost in a range of 0.1-0.5 km3. Tephra fallout may damage agriculture in a large area near the volcano. If only 1% of the lake water were ejected during an eruption and then precipitated over an area of 200 km2, the average rainfall would be 100 mm. Moreover, lahars are likely to occur as both tephra and water ejected from the caldera lake fall onto flanks of the volcano. Rocks avalanching into the caldera lake also would bring about grave hazards because seiches would be triggered and lake water with the volume equal to that of the landslide would spill out of the existing breach in the caldera and cause flooding downstream.

  5. GPS time series at Campi Flegrei caldera (2000-2013

    Directory of Open Access Journals (Sweden)

    Prospero De Martino

    2014-05-01

    Full Text Available The Campi Flegrei caldera is an active volcanic system associated to a high volcanic risk, and represents a well known and peculiar example of ground deformations (bradyseism, characterized by intense uplift periods, followed by subsidence phases with some episodic superimposed mini-uplifts. Ground deformation is an important volcanic precursor, and, its continuous monitoring, is one of the main tool for short time forecast of eruptive activity. This paper provides an overview of the continuous GPS monitoring of the Campi Flegrei caldera from January 2000 to July 2013, including network operations, data recording and processing, and data products. In this period the GPS time series allowed continuous and accurate tracking of ground deformation of the area. Seven main uplift episodes were detected, and during each uplift period, the recurrent horizontal displacement pattern, radial from the “caldera center”, suggests no significant change in deformation source geometry and location occurs. The complete archive of GPS time series at Campi Flegrei area is reported in the Supplementary materials. These data can be usefull for the scientific community in improving the research on Campi Flegrei caldera dynamic and hazard assessment.

  6. Calderas of the Central Sector of the Mexican Volcanic Belt

    Science.gov (United States)

    Aguirre-Diaz, G. J.

    2001-12-01

    The central sector of the Mexican Volcanic Belt (MVB) (-99 to -103, Long W) has the largest number of calderas so far identified in this province. The calderas (with their age range in Ma, and distance to the Middle America Trench in km, in parenthesis) are: Amazcala (7-6, 480), Apaseo (7-6, 440), Huichapan (5-4, 420), Agustinos (5-4, 400), Amealco (5-4, 400), Macua (4-3, 410), Muerta (?, 380), Catedral (6-5, 370), Azufres (4.5-0.03, 370 -Pradal & Robin, 1994), and Zitácuaro (12-0.5, 320 -Capra et al., 1997). Most calderas completed their activity in about 1 Ma, but Azufres and Zitácuaro had longer lives, mostly as post-caldera lava domes and associated pyroclastic flows. Amazcala is rhyolitic, peraluminous-peralkaline, and 10x14 km in diameter. Apaseo is a 11x14 km center that started as andesitic-dacitic and ended rhyolitic and mildly peraluminous; Huichapan started with dacitic ignimbrites and ended with a major rhyolitic ignimbrite; Agustinos is a > 6 km open semi-circle structure that erupted first an andesitic ignimbrite and then a rhyolitic one; Amealco is 10 km in size and erupted a succession of three ignimbrites with mingled glasses with compositions from trachyandesite to rhyolite; Macua is a summit crater structure, 3x5 km, that erupted an unwelded rhyolitic ignimbrite; Muerta is a sector collapse caldera, 4x5 km, associated to lithics-rich ignimbrite eruptions; next to Mexico-City is Catedral, a 9x6 km in diameter caldera with silicic ignimbrites and rim and central lava domes, some of which erupted block-and-ash flows; Azufres has being a matter of debate, but according to Padral and Robin (1994), is a long-lived structure, about 20 km in diameter, with the major caldera eruption at 4.5-3.4 Ma, and repeated dome and pyroclastic flow activity until 26 Ka ago; Zitácuaro (Capra et al., 1997) is another long-lived center, with eruptive cycles at 12 Ma (the caldera-forming event), 5 Ma and 0.5 Ma (mostly domes and associated pyroclastic flows). Most

  7. Structure of La Primavera caldera, Jalisco, Mexico, deduced from gravity anomalies and drilling results

    Science.gov (United States)

    Yokoyama, I.; Mena, M.

    1991-07-01

    Previous studies of La Primavera caldera have mostly been based on surface geology and topography. Since 1980, many wells, exploring for geothermal energy, have reached depths of about 2 to 3 km at the center of the caldera. The results of the drillings, together with those of the gravity surveys, provide information about the subsurface structure of the caldera, and shed light on its formation. The drilling results and gravity anomalies at La Primavera caldera and San Marcos, located at about 40 km distance from the caldera, suggest that regional gravity anomalies can be interpreted in terms of depths of the granitic basements: the basement beneath La Primavera caldera is about 3 km deep and consists of roughly the same horizon as that beneath San Marcos. The drilling results within the caldera reveal that the depth of the caldera fills ranges from 0.3 to 1 km at the drilling sites. The andesite basement, about 1 km deep, remains approximately horizontal, and the granitic basement has a depth of about 3 km. The surface topographies, such as the postcaldera domes, scarcely disturb the subsurface strata. The local gravity anomalies show two lows within the caldera reflecting the configuration of caldera bottom, two funnel-shaped depressions, one of which corresponds to a vent of the Tala tuff deduced from geological observations. The mass deficiency within the caldera estimated from the gravity anomaly, satisfies the general relationship that the mass deficiency is proportional to the caldera diameter cubed. This means that caldera structure is three-dimensional: the larger the diameter, the deeper the funnel-shape. At present this argument may be limited to funnel-shaped calderas.

  8. Intercambio de experiencias de capacitación y de práctica profesional

    Directory of Open Access Journals (Sweden)

    Marielos Vargas Morales

    2010-06-01

    Full Text Available

    Recibido 11 de agosto de 2009 • Aceptado 02 de diciembre de 2009 • Corregido 02 de marzo de 2010

     

    Resumen. Este artículo surge como producto de la implementación del proyecto Intercambio Académico entre la División de Educación Rural (DER, de la Universidad Nacional (UNA y escuelas colaboradoras. Desde su quehacer se abordan dos acciones fundamentales; la primera, la concepción teórico-metodológica de la práctica profesional de la DER y la segunda, el proceso de capacitación dirigido a maestros rurales en servicio. A partir de estas actividades académicas se exponen productos gestados a lo interno del proyecto y algunas reflexiones sobre la experiencia académica como resultado de lecciones aprendidas durante el proceso.

     

    Abstract. The present article arises from the implementation of the Academic Exchange project between the Division de Educación Rural (Rural Education School from Universidad Nacional and other collaborating schools. There are two fundamental actions that are approached; first, the theoretical methodological conception of the professional field practicum of the DER and second, the teaching training to rural teachers in service. From these academic activities, products developed are exposed in the project and some reflections about the academic experience were also exposed as a result of lessons learned during the whole process.

  9. Temperature data from wells in Long Valley Caldera, California

    Science.gov (United States)

    Farrar, Christopher; DeAngelo, Jacob; Williams, Colin; Grubb, Frederick; Hurwitz, Shaul

    2010-01-01

    The 30-by-20-km Long Valley Caldera (LVC) in eastern California (fig.1) formed at 0.76 Ma in a cataclysmic eruption that resulted in the deposition of 600 km? of Bishop Tuff outside the caldera rim (Bailey, 1989). By approximately 0.6 Ma, uplift of the central part of the caldera floor and eruption of rhyolitic lava formed the resurgent dome. The most recent eruptive activity in the area occurred approximately 600 yr ago along the Mono-Inyo craters volcanic chain (Bailey, 2004; Hildreth, 2004). LVC hosts an active hydrothermal system that includes hot springs, fumaroles, mineral deposits, and an active geothermal well field and power plant at Casa Diablo along the southwestern boundary of the resurgent dome (Sorey and Lewis, 1976; Sorey and others, 1978; Sorey and others, 1991). Electric power generation began in 1985 with about 10 Mwe net capacity and was expanded to about 40 Mwe (net) in 1991 (Campbell, 2000; Suemnicht and others, 2007). Plans for further expansion are focused mainly on targets in the caldera?s western moat (Sass and Priest, 2002) where the most recent volcanic activity has occurred (Hildreth, 2004). LVC has been the site of extensive research on geothermal resources and volcanic hazards (Bailey and others, 1976; Muffler and Williams, 1976; Miller and others, 1982; Hill and others 2002). The first geothermal exploratory drilling was done in the shallow (geothermal exploration and by the U.S. Geological Survey (USGS) and Sandia National Laboratory for volcanic and geothermal research and exploration. Temperature logs were obtained in some of these wells during or immediately following drilling, before thermal equilibration was complete. Most of the temperature logs, however, were obtained weeks, months, or years after well completion and are representative of dynamic thermal equilibrium. The maximum reservoir temperature for LVC is estimated to be about 220?C on the basis of chemical geothermometers (Fournier and Truesdell, 1973) using analytical

  10. La Identificación Social y las Instituciones Informales: su Efecto en el Intercambio de Conocimiento

    Directory of Open Access Journals (Sweden)

    Eréndira Fierro Moreno

    2014-01-01

    Full Text Available El efecto de los recursos organizaciones en la gestión del conocimiento ha sido ampliamente estudiado. Sin embargo, esta investigación analiza las instituciones informales y la identificación social como determinantes del intercambio de conocimiento. Se constata una brecha en el conocimiento respecto del análisis de la incidencia de las instituciones informales en las estrategias de gestión y de organización en las organizaciones en países de economías emergente. Con base en la teoría de recursos y capacidades, se formula la hipótesis de que las instituciones informales y la identificación social afectan al intercambio de conocimiento. Con un estudio transeccional y con una muestra de organizaciones del sector público del Estado de México, se encontró confirmación de las hipótesis. Se utilizó la técnica de modelación de ecuaciones estructurales. Los resultados de esta investigación confirman que los recursos al ser únicos y valiosos tales como las instituciones informales (siempre y cuando no sean factores restrictivos que afectan a las estrategias de las organizaciones y no sean ineficientes de modo que afecten a la organización y la identificación social ayudan a generar nuevas capacidades. Esta investigación permitió considerar la importancia de recursos organizacionales como generadores de intercambio de co nocimiento.

  11. Efficiency and exchange. neoclassical, institutionalist and neoinstitutionalist schools Eficiencia e intercambio. Corriente neoclásica, institucionalismo y neoinstitucionalismo

    Directory of Open Access Journals (Sweden)

    Morales F Fabio

    1997-06-01

    Full Text Available This article presents a brief review of the role played by institutions in economic exchange and decision-making within the neoclassical, institutionalist, and neoinstitutionalist schools of economic thought. For the neoclassical school, institutions are exogenous, don't affect exchange or economic decisions and, paradoxically, exclude from their analysis the main economic institution: the market. The author contrasts this point of view with the institutionalist and neoinstitutionalist visions in which institutions are essential in shaping the system of exchange and ensuring the functioning of markets, and presents a synthesis of the analytical concerns and contributions of these two approaches to economic thought.En este artículo se presenta una breve revisión del papel que juegan las instituciones en el intercambio y la toma de decisiones económicas dentro de las corrientes del pensamiento económico neoclásica, institucionalista y neoinstitucionalista. Para la corrientr neoclásica, las instituciones son exógenas, no afectan el intercambio ni las decisiones económicas y paradójicamente, se excluye del análisis la principal institución económica: el mercado. El autor contrasta este punto de vista con las visiones institucionalista y neoinstitucionalista en las que las instituciones son esenciales para configurar el sistema de intercambio y asegurar el funcionamiento del mercado, y presenta una síntesis de las preocupaciones analíticas y las contribuciones de estas dos vertientes del pensamiento económico.

  12. Efecto del intercambio de recursos y fuerza de trabajo en la elección de contingencias compartidas

    OpenAIRE

    Lizbeth Pulido Avalos; Nora Edith Rangel Bernal; Ángela Karina Ávila Hernández; Fátima Yaneth Mérida Velez; Emilio Ribes Iñesta

    2014-01-01

    Se planeó un experimento para evaluar el efecto del intercambio de recursos y fuerza de trabajo en la elección entre contingencias no compartidas o contingencias compartidas de altruismo parcial con o sin ganancias diferenciales. Ocho díadas de estudiantes universitarios resolvieron rompecabezas en dos computadoras interconectadas en red (cuatro lo hicieron en el mismo cubículo y cuatro en cubículos distintos a fin de restringir la posibilidad de interacción verbal). En las condiciones experi...

  13. Aproximación a una pedagogía de los intercambios en el aprendizaje de una lengua extranjera

    OpenAIRE

    Del Olmo Renedo, Daudencio

    1995-01-01

    El avance en el desarrollo de una pedagogía de los intercambios llevará a los enseñantes de los distintos países, comprometidos con su formación, a compartir un lenguaje común, a crear una cultura profesional común y, por lo mismo, a entenderse y a trabajar conjuntamente, en la seguridad de que su paso por el otro sistema educativo, relativizando el propio, ha ampliado su horizonte pedagógico.

  14. EFECTOS DEL CONTROL DE CAMBIO EN EL INTERCAMBIO COMERCIAL CON COLOMBIA. CONSECUENCIAS DEL RETIRO DE VENEZUELA DE LA COMUNIDAD ANDINA

    Directory of Open Access Journals (Sweden)

    Humberto José Mayora Guaita

    2013-02-01

    Full Text Available Trade between Colombia and Venezuela has been totally affected in the past four years. One of the salient features is evidenced by the records of imports and exports of billions of dollars that experienced their peak in 2008 with 7.289 million dollars of trade. However, since 2009 this trade declined due to political confrontations that made to rethink the challenges and strategies in Caracas and Bogota to recover, rather than economic, the political, institutional and even social. This research aims to analyze the causes that led to a stage where it is ob-served a booming in bilateral trade, momentum, maximum and steep drops, but one way or another are needed for its complement. The methodology used in this study was the documentary research. Finally these events are related to the rigors of exchange control in Venezuela, CADIVI, that affect the price of the products that are recorded daily in various transactions made by entrepreneurs and marketers on the Colombian side and by the end 2011 recorded an exchange of 2,193 million.El intercambio comercial entre Colombia y Venezuela ha estado totalmente afectado en los últimos cuatro años. Uno de los rasgos más destacados se evidencia con registros de importaciones y exportaciones de miles de millones de dólares que experimentaron sus máximas en 2008 con 7.289 millones de dólares de intercambio comercial. Sin embargo, des-de el año 2009 este intercambio disminuyó a causa de las confrontaciones políticas que hizo replantear los retos y estrategias en Caracas y Bogotá para recuperar más que las relaciones económicas, las políticas, institucionales y hasta sociales. Esta investigación tiene como objetivos analizar las causas que propiciaron un escenario donde se observa el comercio binacional con auge, impulso, máximas y caídas abruptas, pero que de una manera u otra manera se necesitan para su complemento. La metodología empleada consiste en la investigación documental. Finalmente

  15. Análisis crítico de los modelos interpretativos dominantes sobre el intercambio desigual en la historia

    OpenAIRE

    Carlos Alberto Tomás Astarita

    1989-01-01

    En este trabajo se considerará la situación historiográfica sobre el intercambio desigual o asimétrico, noción que aparece vinculada con el de desarrollo diferenciado entre países. La posición más conocida en el estudio de la historia europea es la de Immanuel Wallerstein, quien ha tratado el problema entre 1450 y 1750, en trabajos de muy amplia difusión internacional. La base del razonamiento de Wallerstein es que la transferencia de materias primas por manufacturas de un área o pa...

  16. Hollow volcanic tumulus caves of Kilauea Caldera, Hawaii County, Hawaii

    Directory of Open Access Journals (Sweden)

    William R. Halliday

    1998-01-01

    Full Text Available In addition to lava tube caves with commonly noted features, sizable subcrustal spaces of several types exist on the floor of Kilauea Caldera. Most of these are formed by drainage of partially stabilized volcanic structures enlarged or formed by injection of very fluid lava beneath a plastic crust. Most conspicuous are hollow tumuli, possibly first described by Walker in 1991. Walker mapped and described the outer chamber of Tumulus E-I Cave. Further exploration has revealed that it has a hyperthermic inner room beneath an adjoining tumulus with no connection evident on the surface. Two lengthy, sinuous hollow tumuli also are present in this part of the caldera. These findings support Walkers conclusions that hollow tumuli provide valuable insights into tumulus-forming mechanisms, and provide information about the processes of emplacement of pahoehoe sheet flows.

  17. Long Valley Caldera Lake and reincision of Owens River Gorge

    Science.gov (United States)

    Hildreth, Wes; Fierstein, Judy

    2016-12-16

    Owens River Gorge, today rimmed exclusively in 767-ka Bishop Tuff, was first cut during the Neogene through a ridge of Triassic granodiorite to a depth as great as its present-day floor and was then filled to its rim by a small basaltic shield at 3.3 Ma. The gorge-filling basalt, 200 m thick, blocked a 5-km-long reach of the upper gorge, diverting the Owens River southward around the shield into Rock Creek where another 200-m-deep gorge was cut through the same basement ridge. Much later, during Marine Isotope Stage (MIS) 22 (~900–866 ka), a piedmont glacier buried the diversion and deposited a thick sheet of Sherwin Till atop the basalt on both sides of the original gorge, showing that the basalt-filled reach had not, by then, been reexcavated. At 767 ka, eruption of the Bishop Tuff blanketed the landscape with welded ignimbrite, deeply covering the till, basalt, and granodiorite and completely filling all additional reaches of both Rock Creek canyon and Owens River Gorge. The ignimbrite rests directly on the basalt and till along the walls of Owens Gorge, but nowhere was it inset against either, showing that the basalt-blocked reach had still not been reexcavated. Subsidence of Long Valley Caldera at 767 ka produced a steep-walled depression at least 700 m deeper than the precaldera floor of Owens Gorge, which was beheaded at the caldera’s southeast rim. Caldera collapse reoriented proximal drainages that had formerly joined east-flowing Owens River, abruptly reversing flow westward into the caldera. It took 600,000 years of sedimentation in the 26-km-long, usually shallow, caldera lake to fill the deep basin and raise lake level to its threshold for overflow. Not until then did reestablishment of Owens River Gorge begin, by incision of the gorge-filling ignimbrite.

  18. Volcanic hazard assessment at the Campi Flegrei caldera

    OpenAIRE

    Mastrolorenzo, G.; Pappalardo, L; C. Troise; S. Rossano; Panizza, A; G. De Natale

    2006-01-01

    Previous and new results from probabilistic approaches based on available volcanological data from real eruptions of Campi Flegrei, are assembled in a comprehensive assessment of volcanic hazards at the Campi Flegrei caldera, in order to compare the volcanic hazards related to the different types of events. Hazard maps based on a very wide set of numerical simulations, produced using field and laboratory data as input parameters relative to the whole range of fallout and pyrocl...

  19. Uplift, thermal unrest and magma intrusion at Yellowstone caldera.

    Science.gov (United States)

    Wicks, Charles W; Thatcher, Wayne; Dzurisin, Daniel; Svarc, Jerry

    2006-03-02

    The Yellowstone caldera, in the western United States, formed approximately 640,000 years ago when an explosive eruption ejected approximately 1,000 km3 of material. It is the youngest of a series of large calderas that formed during sequential cataclysmic eruptions that began approximately 16 million years ago in eastern Oregon and northern Nevada. The Yellowstone caldera was largely buried by rhyolite lava flows during eruptions that occurred from approximately 150,000 to approximately 70,000 years ago. Since the last eruption, Yellowstone has remained restless, with high seismicity, continuing uplift/subsidence episodes with movements of approximately 70 cm historically to several metres since the Pleistocene epoch, and intense hydrothermal activity. Here we present observations of a new mode of surface deformation in Yellowstone, based on radar interferometry observations from the European Space Agency ERS-2 satellite. We infer that the observed pattern of uplift and subsidence results from variations in the movement of molten basalt into and out of the Yellowstone volcanic system.

  20. A kuroko-type polymetallic sulfide deposit in a submarine silicic caldera

    Science.gov (United States)

    Iizasa; Fiske; Ishizuka; Yuasa; Hashimoto; Ishibashi; Naka; Horii; Fujiwara; Imai; Koyama

    1999-02-12

    Manned submersible studies have delineated a large and actively growing Kuroko-type volcanogenic massive sulfide deposit 400 kilometers south of Tokyo in Myojin Knoll submarine caldera. The sulfide body is located on the caldera floor at a depth of 1210 to 1360 meters, has an area of 400 by 400 by 30 meters, and is notably rich in gold and silver. The discovery of a large Kuroko-type polymetallic sulfide deposit in this arc-front caldera raises the possibility that the numerous unexplored submarine silicic calderas elsewhere might have similar deposits.

  1. Relating seismic swarms and deformation in Long Valley Caldera, California

    Science.gov (United States)

    Montgomery-Brown, E. K.; Ellsworth, W. L.; Hill, D. P.; Shelly, D. R.; Langbein, J. O.; Lisowski, M.; Llenos, A. L.

    2013-12-01

    Earthquake swarm activity in the South Moat Seismic Zone (SMSZ) in Long Valley caldera began increasing following the onset of slow inflation of the resurgent dome in 2011. From 1980 through 1999 the caldera produced recurring earthquake swarms in the SMSZ accompanied by an 80-cm uplift of the resurgent dome. Since 2000, the caldera has been quieter than from 1980 to 1999, but it experienced a gradual 7-cm uplift episode in 2002-2003 and currently the caldera has been gradually uplifting since 2011 at less than half of the peak uplift velocity observed in the late 1990's. Two of the recent swarms in October/November of 2012 and March 2013 have been accompanied by small deformation transients during which caldera uplift paused for about a week despite otherwise steady inflation. To better understand this recent activity, we cross correlate seismic velocity waveforms from individual events recorded by the Long Valley seismic network to identify similar clusters (families) of earthquakes and analyze their temporal recurrence. Then, we use representative waveforms from each family as templates to search the continuous waveforms from the deep borehole seismometers in the Long Valley Exploratory Well (MDH1) for repeating, yet smaller, earthquakes. MDH1 consists of two three-component instruments, located 2592 m and 2263 m below ground level, that provide 6 channels with very low background noise relative to surface seismometers. The cross correlations identify about 25 times more earthquakes with most magnitudes ranging from -1 to +0.5, determined from an empirical relationship between catalog magnitude and observed amplitude on MDH1. We apply an ETAS model to the augmented catalog to detect subtle changes in background earthquake rates that might suggest a change in stressing rate. For comparison with the change in seismicity rates, a geodetically determined stress change is estimated from a simple model of the continuous GPS data. We model the uplift from 2011 to

  2. Propuesta para un programa de intercambio de alumnos de escuelas de ingeniería en países de Latinoamérica y el Caribe

    OpenAIRE

    Núñez Guerrero, Yilsy; Rodríguez Monroy, Carlos

    2011-01-01

    La evolución de la sociedad industrial hacia la sociedad del conocimiento ha proporcionado el escenario idóneo para la evolución en la oferta de educación superior la cual ha sufrido severos cambios en el último cuarto de siglo. Algunos de estos hechos están marcando las nuevas tendencias, siendo la movilidad e intercambio académico una de ellas. En este artículo se pretende formular una propuesta de un programa de intercambio de alumnos de escuelas de ingeniería en los países de Latinoaméric...

  3. Geologic map of the Caetano caldera, Lander and Eureka counties, Nevada

    Science.gov (United States)

    Colgan, Joseph P.; Henry, Christopher D.; John, David A.

    2011-01-01

    The Eocene (34 Ma) Caetano caldera in north-central Nevada offers an exceptional opportunity to study the physical and petrogenetic evolution of a large (20 km by 10–18 km pre-extensional dimensions) silicic magma chamber, from precursor magmatism to caldera collapse and intrusion of resurgent plutons. Caldera-related rocks shown on this map include two units of crystal-rich intracaldera tuff totaling over 4 km thickness, caldera collapse breccias, tuff dikes that fed the eruption, hydrothermally altered post-eruption rocks, and two generations of resurgent granitic intrusions (John et al., 2008). The map also depicts middle Miocene (about 16–12 Ma) normal faults and synextensional basins that accommodated >100 percent extension and tilted the caldera into a series of ~40° east-dipping blocks, producing exceptional 3-D exposures of the caldera interior (Colgan et al., 2008). This 1:75,000-scale map is a compilation of published maps and extensive new mapping by the authors (fig. 1), and supersedes a preliminary 1:100,000-scale map published by Colgan et al. (2008) and John et al. (2008). New mapping focused on the margins of the Caetano caldera, the distribution and lithology of rocks within the caldera, and on the Miocene normal faults and sedimentary basins that record Neogene extensional faulting. The definition of geologic units and their distribution within the caldera is based entirely on new mapping, except in the northern Toiyabe Range, where mapping by Gilluly and Gates (1965) was modified with new field observations. The distribution of pre-Cenozoic rocks outside the caldera was largely compiled from existing sources with minor modifications, with the exception of the northeastern caldera margin (west of the Cortez Hills Mine), which was remapped in the course of this work and published as a stand-alone 1:6000-scale map (Moore and Henry, 2010).

  4. Implications of a Caldera Origin of the Lunar Crater Copernicus

    Science.gov (United States)

    Green, J.

    2007-12-01

    The forthcoming renaissance in lunar exploration will focus on many objectives such as Copernicus. Copernicus appears to be a caldera for at least 8 reasons. If a caldera we see (1) transient activity (2) no overturned impact flap at the crater margins (3) internal sinuous leveed lava flow channels (4) a lava covered floor (5) terraces of different ages (6) multiple central volcanoes, one showing a directed volcanic blast (7) olivine-rich komatiitic lavas on central volcanoes and (8) magmatic inflation/deflation on caldera flanks localizing craterlets and extinct fumaroles in "loop" patterns. Regarding (6), directed volcanic blasts can remove a segment of the volcano wall as evidenced in terrestrial analogs at Mt. St. Helens and Bezymianny. Impact mechanisms to produce this feature in Copernicus are contrived. For (7) Clementine spectral data show a high olivine content of the central mountains on Copernicus which I interpret as forsteritic spinifex mineralization in komatiitic lavas and not as impact rebound of olivine-rich deep seated rocks. (8) MacDonald (1956) documented loop patterns on the flank of Halemaumau in Hawaii defining arcuate fractures localizing fumaroles and craterlets. Inflation/deflation of subjacent magma bodies are interpreted as the cause for these loops. Inflation/deflation mechanisms on caldera flanks are common around terrestrial calderas. "Loop" patterns on the flank of Copernicus localizing "gouge" craterlets have been interpreted as ballistic features resulting from the meteorite impact of this crater. Questioned is the logic of a linear N26E trending array of fragments within Copernicus to serve as a source of ballistic projectiles to form the loops localizing conjugate craterlets. The fused craterlet axes on the lunar loops do not point back to a presumed impact center in Copernicus. The axes are oriented parallel to a regional northwest (N35-60W) fracture zone. Implications for an endogenic origin of Copernicus would involve

  5. Magma transfer at Campi Flegrei caldera (Italy) before the 1538 AD eruption

    Science.gov (United States)

    di Vito, Mauro A.; Acocella, Valerio; Aiello, Giuseppe; Barra, Diana; Battaglia, Maurizio; Carandente, Antonio; Del Gaudio, Carlo; de Vita, Sandro; Ricciardi, Giovanni P.; Ricco, Ciro; Scandone, Roberto; Terrasi, Filippo

    2016-08-01

    Calderas are collapse structures related to the emptying of magmatic reservoirs, often associated with large eruptions from long-lived magmatic systems. Understanding how magma is transferred from a magma reservoir to the surface before eruptions is a major challenge. Here we exploit the historical, archaeological and geological record of Campi Flegrei caldera to estimate the surface deformation preceding the Monte Nuovo eruption and investigate the shallow magma transfer. Our data suggest a progressive magma accumulation from ~1251 to 1536 in a 4.6 ± 0.9 km deep source below the caldera centre, and its transfer, between 1536 and 1538, to a 3.8 ± 0.6 km deep magmatic source ~4 km NW of the caldera centre, below Monte Nuovo; this peripheral source fed the eruption through a shallower source, 0.4 ± 0.3 km deep. This is the first reconstruction of pre-eruptive magma transfer at Campi Flegrei and corroborates the existence of a stationary oblate source, below the caldera centre, that has been feeding lateral eruptions for the last ~5 ka. Our results suggest: 1) repeated emplacement of magma through intrusions below the caldera centre; 2) occasional lateral transfer of magma feeding non-central eruptions within the caldera. Comparison with historical unrest at calderas worldwide suggests that this behavior is common.

  6. Riobamba y el ferrocarril. Nuevas dinámicas de intercambio regional en el primer cuarto del siglo XX

    Directory of Open Access Journals (Sweden)

    Franklin Cepeda Astudillo

    2006-11-01

    Full Text Available Este artículo analiza los conflictos que produjo el paso del ferrocarril por Riobamba. Describe la lucha por la rectificación de la vía férrea, que enlazaba las ciudades de Guayaquil y Quito, y subraya las pugnas y aspiraciones locales relacionadas con el nuevo medio de transporte. Señala las reacciones de la opinión pública riobambeña, expuestas en su prensa local, y las posturas tanto de los gobiernos como de la empresa que construyó la obra. Además, estudia las consecuencias que se derivaron del paso del ferrocarril: la ampliación del mercado interno como consecuencia del incremento del comercio interregional, el desarrollo de los poblados situados a lo largo del trazado ferroviario y la aceleración del intercambio de personas y bienes.

  7. REMOCIÓN DE COBRE Y NÍQUEL POR INTERCAMBIO CATIÓNICO CON UNA ZEOLITA NATURAL

    Directory of Open Access Journals (Sweden)

    Arnoldy Estupiñan

    2010-10-01

    Full Text Available Se empleó la zeolita natural clinoptilolita, para remover cobre y níquel de aguas residuales de una industria de galvanotecnia. La capacidad de intercambio determinada para la zeolita transformada al estado homoiónico sódico, fue de 0,794 meq/g para cobre y 0,447 meq/g para níquel. Se realizaron ensayos en cochada y en columna, alcanzando éste último un mayor acercamiento al equilibrio. En los ensayos de regeneración, la zeolita sódica concentró el cobre hasta 23,5 veces con respecto al valor que presenta en los enjuagues de los baños de recubrimiento en medio ácido, mostrando su potencialidad para usarla en el tratamiento de estos residuos, por su efectividad y bajo costo.

  8. Preliminary geologic studies of Sierra El Aguajito (Baja California, Mexico): a resurgent-type caldera

    Science.gov (United States)

    Garduño-Monroy, V. H.; Vargas-Ledezma, H.; Campos-Enriquez, J. O.

    1993-12-01

    Geologic field studies conducted in the Quaternary volcanic field of Tres Virgenes (State of Baja California Sur, Mexico) revealed the existence of a resurgent caldera. The caldera's eruptive products, the Aguajito sequence, overlie the products of the nearby Reforma caldera (Reforma sequence) whose youngest products have already been dated as Quaternary. The rim of the Aguajito caldera is inferred by the existence of an arcuate alignment of rhyolitic domes. The mean diameter of this subcircular feature is 10 km. The volume of its mapped acidic products is a minimum of 10 km 3. Several horizons within the sequence contain shells. K/Ar dates of the ignimbrites and domes of El Aguajito formation confirm that the unit are Pleistocene. The detailed stratigraphy also shows the evolution of a marine regression partly related to the caldera.

  9. Long Valley Caldera 2003 through 2014: overview of low level unrest in the past decade

    Science.gov (United States)

    Wilkinson, Stuart K.; Hill, David P.; Langbein, John O.; Lisowski, Michael; Mangan, Margaret T.

    2014-01-01

    Long Valley Caldera is located in California along the eastern escarpment of the Sierra Nevada Range. The caldera formed about 760,000 years ago as the eruption of 600 km3 of rhyolite magma (Bishop Tuff) resulted in collapse of the partially evacuated magma chamber. Resurgent doming in the central part of the caldera occurred shortly afterwards, and the most recent eruptions inside the caldera occurred about 50,000 years ago. The caldera remains thermally active, with many hot springs and fumaroles, and has had significant deformation and seismicity since at least 1978. Periods of intense unrest in the 1980s to early 2000s are well documented in the literature (Hill and others, 2002; Ewert and others, 2010). In this poster, we extend the timeline forward, documenting seismicity and deformation over the past decade.

  10. A multidisciplinary study of the 2014-2015 Bárðarbunga caldera collapse, Iceland

    Science.gov (United States)

    Tumi Gudmundsson, Magnus; Jonsdóttir, Kristin; Hooper, Andy; Holohan, Eoghan; Halldorsson, Saemundur

    2016-04-01

    The collapse of the ice-filled Bárðarbunga caldera in central Iceland occurred in autumn and winter, when weather was highly unsettled and conditions for monitoring in many ways difficult. Nevertheless several detailed time series could be obtained on the collapse and to a degree the associated flood-basalt eruption in Holuhraun. This was achieved through applying an array of sensors, that were ground, air and satellite based, partly made possible through the EU-funded FUTUREVOLC supersite project. This slow caldera collapse lasted six months, ending in February 2015. The array of sensors used, coupled with the long duration of the event, allowed unprecedented detail in observing a caldera collapse. The deciphering of the course of events required the use of aircraft altimeter surveys of the ice surface, seismic and GPS monitoring, the installation of a GPS station on the glacier surface in the centre of the caldera that continuously recorded the subsidence. Full Stokes 3-D modelling of the 700-800 m thick ice in the caldera, constrained by observations, was applied to remove the component of ice deformation that had a minor effect on the measured subsidence. The maximum subsidence of the subglacial caldera floor was about 65 meters. The combined interpretation of geochemical geobarometers, subsidence geometry with GPS and InSAR deformation signals, seismicity and distinct element deformation modelling of the subsidence provided unprecedented detail of the process and mechanism of caldera collapse. The collapse involved the re-activation of pre-existing ring faults, and was initiated a few days after magma started to drain from underneath the caldera towards the eventual eruption site in Holuhraun, 45 km to the northeast. The caldera collapse was slow and gradual, and the flow rate from underneath the caldera correlates well with the lava flow rate in Holuhraun, both in terms of total volume and variations in time.

  11. Renewed inflation of Long Valley Caldera, California (2011 to 2014)

    Science.gov (United States)

    Montgomery-Brown, Emily; Wicks, Chuck; Cervelli, Peter F.; Langbein, John O.; Svarc, Jerry L.; Shelly, David R.; Hill, David P.; Lisowski, Michael

    2015-01-01

    Slow inflation began at Long Valley Caldera in late 2011, coinciding with renewed swarm seismicity. Ongoing deformation is concentrated within the caldera. We analyze this deformation using a combination of GPS and InSAR (TerraSAR-X) data processed with a persistent scatterer technique. The extension rate of the dome-crossing baseline during this episode (CA99 to KRAC) is 1 cm/yr, similar to past inflation episodes (1990–1995 and 2002–2003), and about a tenth of the peak rate observed during the 1997 unrest. The current deformation is well modeled by the inflation of a prolate spheroidal magma reservoir ∼7 km beneath the resurgent dome, with a volume change of ∼6 × 106 m3/yr from 2011.7 through the end of 2014. The current data cannot resolve a second source, which was required to model the 1997 episode. This source appears to be in the same region as previous inflation episodes, suggesting a persistent reservoir.

  12. Months between rejuvenation and volcanic eruption at Yellowstone caldera, Wyoming

    Science.gov (United States)

    Till, Christy B.; Vazquez, Jorge A.; Boyce, Jeremy W

    2015-01-01

    Rejuvenation of previously intruded silicic magma is an important process leading to effusive rhyolite, which is the most common product of volcanism at calderas with protracted histories of eruption and unrest such as Yellowstone, Long Valley, and Valles, USA. Although orders of magnitude smaller in volume than rare caldera-forming super-eruptions, these relatively frequent effusions of rhyolite are comparable to the largest eruptions of the 20th century and pose a considerable volcanic hazard. However, the physical pathway from rejuvenation to eruption of silicic magma is unclear particularly because the time between reheating of a subvolcanic intrusion and eruption is poorly quantified. This study uses geospeedometry of trace element profiles with nanometer resolution in sanidine crystals to reveal that Yellowstone’s most recent volcanic cycle began when remobilization of a near- or sub-solidus silicic magma occurred less than 10 months prior to eruption, following a 220,000 year period of volcanic repose. Our results reveal a geologically rapid timescale for rejuvenation and effusion of ~3 km3 of high-silica rhyolite lava even after protracted cooling of the subvolcanic system, which is consistent with recent physical modeling that predict a timescale of several years or less. Future renewal of rhyolitic volcanism at Yellowstone is likely to require an energetic intrusion of mafic or silicic magma into the shallow subvolcanic reservoir and could rapidly generate an eruptible rhyolite on timescales similar to those documented here.

  13. Sheet flow caves of Kilauea Caldera, Hawaii County, Hawaii

    Directory of Open Access Journals (Sweden)

    William R. Halliday

    1998-01-01

    Full Text Available Terminal lobes of sheet flows of pahoehoe lava sometimes form three-dimensional nests, initially separated by partitions consisting of accreted ‘skins” of each lobe. Melting breaks down these partitions, forming a uniform flow unit. In Kilauea Caldera we have found and mapped sizable drained cavities in low-slope sheet flows. Their general pattern includes three-dimensional nests, with partially melted septa evident in some examples. Christmas Cave is the most extensive found to date, with 632 meters surveyed on two levels. It is located at the lower end of an inflated sheet flow tongue which underwent local deflation as a result of drainage through the cave after its parameters were partially fixed. Small conduit remnants persist in its boundary ridges. The major part of the cave consists of wide, low nestled chambers. Meltdown of such partitions is one of the few emplacement mechanisms of thermal erosion which may not involve any mechanical element. Additional caves in this caldera are being identified and studied.

  14. Physical volcanology of the mafic segment of the subaqueous New Senator caldera, Abitibi greenstone belt, Quebec, Canada

    Energy Technology Data Exchange (ETDEWEB)

    Moore, Lyndsay N; Mueller, Wulf U [Universite du Quebec a Chicoutimi, 555 boul. du l' Universite, Chicoutimi, Quebec, G7H2B1 (Canada)], E-mail: lyndsay.moore@uqac.ca

    2008-10-01

    Archean calderas provide valuable insight into internal geometries of subaqueous calderas. The New Senator caldera, Abitibi greenstone belt, Canada, is an Archean example of a subaqueous nested caldera with a basal stratigraphy dominated by gabbro-diorite dykes and sills, ponded magmas and basalt and andesite lava flows. The aim of our study is to focus on the use of physical volcanology to differentiate between the various mafic units found at the base of the New Senator caldera. Differentiation between these various mafic units is important from an exploration point of view because in modern subaqueous summit calders (e.g. Axial Seamount) margins of ponded magmas are often sites of VMS formation.

  15. Control adaptable utilizando Redes Neuronales Artificiales Polinomiales

    Directory of Open Access Journals (Sweden)

    E. Gómez

    2000-01-01

    Full Text Available Existen en la literatura de Control Adaptable, diferentes procedimientos en los que es posible identificar un sistema lineal. El problema fundamental es que una cantidad importante de fenómenos de la vida real son de tipo no lineal y no es tan sencillo el modelar este tipo de dinámicas. En este trabajo se presenta una forma de identificar sistemas no lineales utilizando las propiedades de las Redes Neuronales Artificiales y las técnicas de Algoritmo Genético en la optimización de su arquitectura. Adicionalmente se presenta una técnica novedosa de control adaptable para cancelar la dinámica no lineal del sistema y colocar los polos en el punto de operación deseado. Se presenta el comportamiento del algoritmo para el caso lineal yno lineal y finalmente se analiza la importancia teórica y operacional de estas técnicas.

  16. Fuel oil-water emulsions to reduce unburned particle emissions from boilers; Emulsiones agua en combustoleo para reducir las emisiones de particulas inquemadas en calderas

    Energy Technology Data Exchange (ETDEWEB)

    Diego Marin, Antonio; Ocampo Barrera, Rene; Martinez Flores, Marco Antonio; Tamayo Flores, Gustavo Adolfo; Alarcon Quiroz, Ernesto [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)

    1997-12-31

    To diminish the problems caused by fuels in boilers such as abnormal soiling of heat interchange surfaces, decrease of thermal and combustion efficiencies and increment of pollutants it is proposed the utilization of fuel oil water emulsions. This technology process is described, its development and application in other countries is shown and mention is made of the experiences in this regard at the Instituto de Investigaciones Electricas (IIE), as well as the perspectives this technology has in Mexico. In conclusion, the fuel oil water emulsion is an alternative that can help burning efficiently the fuel oil and so to contribute to fulfill with the limits established by the environmental regulations on pollutant emissions. The development of this technology is economical and of simple application, compared with others, such as the installation of new burners, the utilization of a commercial technology for flue gas conditioning, etcetera [Espanol] Para disminuir los problemas ocacionados por el combustoleo en las calderas como: ensuciamientos anormales de las superficies de intercambio de calor, disminucion de eficiencias termicas y de combustion e incremento de las emisiones, se propone la utilizacion de la emulsion de agua en combustoleo. Se describe el proceso de esta tecnologia, se muestra su desarrollo y aplicacion en otros paises y se mencionan las experiencias a este respecto en el Instituto de Investigaciones Electricas (IIE), asi como las perspectivas que tiene esta tecnologia en Mexico. En conclusion, la emulsion de agua en combustoleo es una alternativa que puede ayudar a quemar eficientemente al combustoleo y asi contribuir a cumplir con los limites de emisiones que establecen normas ambientales. El desarrollo de esta tecnologia es economica y de aplicacion sencilla, comparada con otras como: la instalacion de nuevos quemadores, la utilizacion de una tecnologia comercial para acondicionar los gases de combustion, etcetera

  17. Subsurface architecture of a strike-slip collapse structure: insights from Ilopango caldera, El Salvador

    Science.gov (United States)

    Saxby, Jennifer; Gottsmann, Joachim; Cashman, Katherine; Gutierrez, Eduardo

    2016-04-01

    While most calderas are created by roof collapse along ring-like faults into an emptying magma reservoir during a large and violent explosive eruption, an additional condition for caldera formation may be tectonically induced extensional stresses. Here we provide geophysical insights into the shallow sub-volcanic plumbing system of a collapse caldera in a major strike-slip tectonic setting by inverting Bouguer gravity data from the Ilopango caldera in El Salvador. Despite a long history of catastrophic eruptions with the most recent in 500 A.D., the internal architecture of the caldera has not been investigated, although studies of the most recent eruption have not identified the ring faults commonly associated with caldera collapse. The gravity data show that low-density material aligned along the principal stress orientations of the El Salvador Fault Zone (ESFZ) forms a pronounced gravity low beneath the caldera. Extending to around 6 km depth, the low density structure likely maps a complex stacked shallow plumbing system composed of magmatic and fractured hydrothermal reservoirs. A substantial volume of the plumbing system must be composed of a vapour phase to explain the modeled negative density contrasts. We use these constraints to map the possible multi-phase parameter space contributing to the subsurface architecture of the caldera and propose that the local extension along the complex ESFZ controls accumulation, ascent and eruption of magma at Ilopango. The data further suggest that future eruptions at Ilopango could be facilitated by rapid rise of magma along conjugate fault damage zones through a mechanically weak crust under tension. This may explain the absence of clear ring fault structures at the caldera.

  18. Anomalías magnéticas en la Caldera Piedra Parada, Patagonia, Argentina

    OpenAIRE

    Aragón, Eugenio; Pinotti, Lucio; D´Eramo, Fernando Javier; GÓMEZ-ORTIZ, DAVID; Tejero López, Rosa; Tubia, José María; Cavarozzi, Claudia Ernestina; Aguilera, Yolanda Emilia; Ribot, Alejandro Mario; Gianibelli, Julio; Chernicoff, Carlos Jorge

    2009-01-01

    La caldera de Piedra Parada constituye el principal edificio volcánico del Complejo Volcánico Piroclástico del curso medio del río Chubut, situado en la provincia argentina de Chubut. Los materiales intracaldera están constituidos por coladas riolíticas, sills andesíticos, domos riolíticos y tobas de composición riolítica. Con objeto de investigar la estructura de la caldera, se han obtenido tanto datos magnéticos terrestres como aeromagnéticos. Los mapas magnéticos muestran que la caldera se...

  19. Closing crack earthquakes within the Krafla caldera, North Iceland

    Science.gov (United States)

    Mildon, Zoë K.; Pugh, David J.; Tarasewicz, Jon; White, Robert S.; Brandsdóttir, Bryndís

    2016-11-01

    Moment tensor analysis with a Bayesian approach was used to analyse a non-double-couple (non-DC) earthquake (Mw ˜ 1) with a high isotropic (implosive) component within the Krafla caldera, Iceland. We deduce that the earthquake was generated by a closing crack at depth. The event is well located, with high signal-to-noise ratio and shows dilatational P-wave first arrivals at all stations where the first arrival can be picked with confidence. Coverage of the focal sphere is comprehensive and the source mechanism stable across the full range of uncertainties. The non-DC event lies within a cluster of microseismic activity including many DC events. Hence, we conclude that it is a true non-DC closing crack earthquake as a result of geothermal utilization and observed magma chamber deflation in the region at present.

  20. Intercambio de gases y relaciones hídricas durante el retraso de la senescencia foliar de trigo (Triticum aestivum L.) por la citocinina bap

    OpenAIRE

    Ricardo Martínez-Gutiérrez; Zavaleta-Mancera, Hilda A.; Lucero del Mar Ruíz-Posadas; Adriana Delgado-Alvarado; Rocío Vaca-Paulín

    2008-01-01

    Se estudió el efecto de la citocinina 6-bencilaminopurina (BAP) en el intercambio de gases y relaciones hídricas de Triticum aestivum L. durante el retraso de la senescencia foliar en invernadero. Plántulas de 21 días después de la siembra (DDS) fueron asperjadas con BAP 0,1mM o agua (testigo) cada 3 días por 20 días. El retraso de senescencia foliar en las plantas tratadas con BAP fue monitoreado mediante cuantificación de clorofila y proteína soluble total. El intercambio de gases se estimó...

  1. Portal Asiático de Información: un servicio transcontinental de intercambio de artículos

    Directory of Open Access Journals (Sweden)

    Martha E. Mantilla

    2011-08-01

    Full Text Available El Portal Asiático de Información de la Universidad de Pittsburgh es un innovador servicio de cooperación entre bibliotecas de Estados Unidos y bibliotecas de la China, Japón, y Corea, que facilita el acceso rápido a artículos publicados en revistas académicas, utilizando tecnología de bajo costo.

  2. Oblique synoptic images, produced from digital data, display strong evidence of a "new" caldera in southwestern Guatemala

    Science.gov (United States)

    Duffield, W.; Heiken, G.; Foley, D.; McEwen, A.

    1993-01-01

    The synoptic view of broad regions of the Earth's surface as displayed in Landsat and other satellite images has greatly aided in the recognition of calderas, ignimbrite plateaus and other geologic landforms. Remote-sensing images that include visual representation of depth are an even more powerful tool for geologic interpretation of landscapes, but their use has been largely restricted to the exploration of planets other than Earth. By combining Landsat images with digitized topography, we have generated regional oblique views that display compelling evidence for a previously undocumented late-Cenozoic caldera within the active volcanic zone of southwestern Guatemala. This "new" caldera, herein called Xela, is a depression about 30 km wide and 400-600 m deep, which includes the Quezaltenango basin. The caldera depression is breached only by a single river canyon. The caldera outline is broadly circular, but a locally scalloped form suggests the occurrence of multiple caldera-collapse events, or local slumping of steep caldera walls, or both. Within its northern part, Xela caldera contains a toreva block, about 500 m high and 2 km long, that may be incompletely foundered pre-caldera bedrock. Xela contains several post-caldera volcanoes, some of which are active. A Bouguer gravity low, tens of milligals in amplitude, is approximately co-located with the proposed caldera. The oblique images also display an extensive plateau that dips about 2?? away from the north margin of Xela caldera. We interpret this landform to be underlain by pyroclastic outflow from Xela and nearby Atitla??n calderas. Field mapping by others has documented a voluminous rhyolitic pumiceous fallout deposit immediately east of Xela caldera. We speculate that Xela caldera was the source of this deposit. If so, the age of at least part of the caldera is between about 84 ka and 126 ka, the ages of deposits that stratigraphically bracket this fallout. Most of the floor of Xela caldera is covered

  3. Estudio de las características del intercambio gaseoso de variedades de geranio en cultivo protegido en zonas de clima mediterráneo

    OpenAIRE

    Sant i Vilella, M. Dolors

    1987-01-01

    [spa] En plantas de geranio dedicadas a la producción de esquejes (Pelargonium x hortorum cv. Orange Ricard, P. grandiflorum cv. FJamingo y P. peltatum cv. Old Lady, cultivadas en contenedor, en substrato artificial, en un invernadero comercial) se realizaron series estacionales de medidas del intercambio gaseoso en laboratorio en respuesta a cambios de irradiancia, temperatura y humedad del aire, y se determinaron en el invernadero la respuesta en el ciclo diario de la fotosíntesis neta, tra...

  4. Seismic constraints on caldera dynamics from the 2015 Axial Seamount eruption

    Science.gov (United States)

    Wilcock, William S. D.; Tolstoy, Maya; Waldhauser, Felix; Garcia, Charles; Tan, Yen Joe; Bohnenstiehl, DelWayne R.; Caplan-Auerbach, Jacqueline; Dziak, Robert P.; Arnulf, Adrien F.; Mann, M. Everett

    2016-12-01

    Seismic observations in volcanically active calderas are challenging. A new cabled observatory atop Axial Seamount on the Juan de Fuca ridge allows unprecedented real-time monitoring of a submarine caldera. Beginning on 24 April 2015, the seismic network captured an eruption that culminated in explosive acoustic signals where lava erupted on the seafloor. Extensive seismic activity preceding the eruption shows that inflation is accommodated by the reactivation of an outward-dipping caldera ring fault, with strong tidal triggering indicating a critically stressed system. The ring fault accommodated deflation during the eruption and provided a pathway for a dike that propagated south and north beneath the caldera’s east wall. Once north of the caldera, the eruption stepped westward, and a dike propagated along the extensional north rift.

  5. Maars to calderas: end-members on a spectrum of explosive volcanic depressions

    Directory of Open Access Journals (Sweden)

    Danilo M. Palladino

    2015-07-01

    Full Text Available We discuss maar-diatremes and calderas as end-members on a spectrum of negative volcanic landforms (depressions produced by explosive eruptions (note – we focus on calderas formed during explosive eruptions, recognizing that some caldera types are not related to such activity. The former are dominated by ejection of material during numerous discrete phreatomagmatic explosions, brecciation, and subsidence of diatreme fill, while the latter are dominated by subsidence over a partly evacuated magma chamber during sustained, magmatic volatile-driven discharge. Many examples share characteristics of both, including landforms that are identified as maars but preserve deposits from non-phreatomagmatic explosive activity, and ambiguous structures that appear to be coalesced maars but that also produced sustained explosive eruptions with likely magma reservoir subsidence. A convergence of research directions on issues related to magma-water interaction and shallow reservoir mechanics is an important avenue toward developing a unified picture of the maar-diatreme-caldera spectrum.

  6. Field trip guide to the Valles Caldera and its geothermal systems

    Energy Technology Data Exchange (ETDEWEB)

    Goff, F.E.; Bolivar, S.L.

    1983-12-01

    This field trip guide has been compiled from extensive field trips led at Los Alamos National Laboratory during the past six years. The original version of this guide was designed to augment a workshop on the Valles Caldera for the Continental Scientific Drilling Program (CSDP). This workshop was held at Los Alamos, New Mexico, 5-7 October 1982. More stops were added to this guide to display the volcanic and geothermal features at the Valles Caldera. The trip covers about 90 miles (one way) and takes two days to complete; however, those who wish to compress the trip into one day are advised to use the designated stops listed in the Introduction. Valles Caldera and vicinity comprise both one of the most exciting geothermal areas in the United States and one of the best preserved Quaternary caldera complexes in the world.

  7. Sobreviviendo al margen. Intercambio y redes de reciprocidad entre hogares en situación de pobreza de Villa Lugano

    Directory of Open Access Journals (Sweden)

    Helga Fourcade

    2012-01-01

    Full Text Available El artículo presenta una investigación, desde la perspectiva de los actores, del funcionamiento de las redes de intercambio recíproco entre un grupo de hogares en situación de pobreza de Villa Lugano (Buenos Aires, Argentina. Para su abordaje fue seleccionado un enfoque analítico basado en los activos, la vulnerabilidad y la estructura de oportunidades. En ese marco, se pretende analizar las modificaciones en el abanico de activos del que disponen los hogares, ante las variaciones de los elementos constitutivos de la estructura de oportunidades en la que se desenvuelven, haciendo énfasis en las características particulares que determinan su lugar en las redes de las que participan. El mercado de trabajo, el Estado y la sociedad representan tres escenarios que, cada uno con sus particularidades, influyen considerablemente en las capacidades de los hogares a la hora de transformar los recursos en activos, condicionando las adaptaciones de los hogares en vistas de mantener o incrementar su bienestar.

  8. How caldera collapse shapes the shallow emplacement and transfer of magma in active volcanoes

    Science.gov (United States)

    Corbi, Fabio; Rivalta, Eleonora; Pinel, Virginie; Maccaferri, Francesco; Bagnardi, Marco; Acocella, Valerio

    2016-04-01

    Calderas are topographic depressions formed by the collapse of a partly drained magma reservoir. At volcanic edifices with calderas, eruptive fissures can circumscribe the outer caldera rim, be oriented radially and/or align with the regional tectonic stress field. Constraining the mechanisms that govern this spatial arrangement is fundamental to understand the dynamics of shallow magma storage and transport and evaluate volcanic hazard. Here we use numerical models to show that the previously unappreciated unloading effect of caldera formation may contribute significantly to the stress budget of a volcano. We first test this hypothesis against the ideal case of Fernandina, Galápagos, where previous models only partly explained the peculiar pattern of circumferential and radial eruptive fissures and the geometry of the intrusions determined by inverting the deformation data. We show that by taking into account the decompression due to the caldera formation, the modeled edifice stress field is consistent with all the observation. We then develop a general model for the stress state at volcanic edifices with calderas based on the competition of caldera decompression, magma buoyancy forces and tectonic stresses. These factors control the shallow accumulation of magma in stacked sills, consistently with observations as well as the conditions for the development of circumferential and/or radial eruptive fissures, as observed on active volcanoes. This top-down control exerted by changes in the distribution of mass at the surface allows better understanding of how shallow magma is transferred at active calderas, contributing to forecasting the location and type of opening fissures.

  9. Proceedings of the second workshop on hydrologic and geochemical monitoring in the Long Valley Caldera

    Energy Technology Data Exchange (ETDEWEB)

    Sorey, M.L.; Farrar, C.D.; Wollenberg, H.A. (eds.)

    1986-12-01

    A workshop was held to review the results of hydrologic and geochemical monitoring and scientific drilling in the Long Valley caldera. Such monitoring is being done to detect changes in the hydrothermal system induced by ongoing magmatic and techonic processes. Data from a 2400-ft deep core hole completed in June 1986 were presented at the 1986 workshop and participants discussed the need and rationale for siting locations for future scientific drilling in the caldera.

  10. Long Valley Caldera-Mammoth Mountain unrest: The knowns and unknowns

    Science.gov (United States)

    Hill, David P.

    2017-01-01

    This perspective is based largely on my study of the Long Valley Caldera (California, USA) over the past 40 years. Here, I’ll examine the “knowns” and the “known unknowns” of the complex tectonic–magmatic system of the Long Valley Caldera volcanic complex. I will also offer a few brief thoughts on the “unknown unknowns” of this system.

  11. Conduit enlargement during the precursory Plinian eruption of Aira Caldera, Japan

    Science.gov (United States)

    Geshi, Nobuo; Miyabuchi, Yasuo

    2016-09-01

    Increase in magma flux as the result of conduit enlargement is one of the key processes that triggered caldera collapse and eruption of the Ito ignimbrite from Aira Caldera at ~29 ka. We examine the total volume of the pumice fall deposit, vertical variations in grain size of pumice, and the lithic content in the Osumi pumice deposit to investigate the trigger for caldera collapse. Wider distribution of the later-stage unit and the upward coarsening of grain size throughout the Osumi pumice fall deposit indicate an increase in magma discharge toward the onset of collapse. The total volume of lithic fragments in the Osumi pumice fall deposit is estimated as ~1.6 km3, based on the lithic content in several representative outcrops and the total volume of the Osumi pumice fall deposit. The lithic fragments in the Osumi pumice fall deposit indicate intense mechanical erosion of the conduit during the Plinian eruption prior to caldera collapse. Caldera collapse requires decompression of the magma chamber by withdrawal of magma; effective enlargement of the conduit diameter during precursory eruptive phases is one of the important processes that subsequently allow the rapid discharge of a large volume of magma, which in turn facilitates decompression of the reservoir and induces caldera collapse.

  12. Hydrothermal activity in the Tulancingo-Acoculco Caldera Complex, central Mexico. Exploratory studies

    Energy Technology Data Exchange (ETDEWEB)

    Lopez-Hernandez, Aida [Gerencia de Proyectos Geotermoelectricos, CFE, Alejandro Volta 655, 58290 Morelia, Michoacan (Mexico); Centro de Geociencias, Universidad Nacional Autonoma de Mexico, Campus Juriquilla, Queretaro, Qro., 76230 (Mexico); Garcia-Estrada, Gerardo; Palma-Guzman, Hugo; Quijano-Leon, Jose L. [Gerencia de Proyectos Geotermoelectricos, CFE, Alejandro Volta 655, 58290 Morelia, Michoacan (Mexico); Aguirre-Diaz, Gerardo; Gonzalez-Partida, Eduardo [Centro de Geociencias, Universidad Nacional Autonoma de Mexico, Campus Juriquilla, Queretaro, Qro., 76230 (Mexico)

    2009-09-15

    Mineral alteration and fluid inclusion studies of drill cuttings and core samples indicate that the sedimentary basement rocks and the volcanic rocks associated with Tulancingo-Acoculco Caldera Complex have been the site of two distinct and major hydrothermal events. The complex, located in the eastern portion of the Trans-Mexican Volcanic Belt, is formed by the Pliocene Tulancingo Caldera and the younger (Pleistocene) Acoculco Caldera, which developed within the older depression. The volcanic rocks are underlain by Cretaceous sedimentary rocks of the Sierra Madre Oriental. The earliest important hydrothermal event occurred during the emplacement of Mid-Tertiary granitic intrusions that metamorphosed the sedimentary rocks; these intrusives are not exposed at the surface. However, granitic rocks were encountered at the bottom of exploratory borehole EAC-1, drilled within the Caldera Complex. The second main event occurred during the formation of the Tulancingo and Acoculco Calderas. Both episodes lead to secondary mineralization that reduced the permeability of the reservoir rocks. A possible third hydrothermal event may be associated with the recent magmatic activity within the Acoculco Caldera.Thermal logs from well EAC-1 display a conductive thermal gradient with maximum temperatures exceeding 300 C at 2000 m depth. Although there are no active thermal springs in the area, there is extensive fossil surface hydrothermal alteration and cold gas discharges with high He{sup 3}/He{sup 4} ratios. (author)

  13. Post-eruptive flooding of Santorini caldera and implications for tsunami generation

    Science.gov (United States)

    Nomikou, P.; Druitt, T. H.; Hübscher, C.; Mather, T. A.; Paulatto, M.; Kalnins, L. M.; Kelfoun, K.; Papanikolaou, D.; Bejelou, K.; Lampridou, D.; Pyle, D. M.; Carey, S.; Watts, A. B.; Weiß, B.; Parks, M. M.

    2016-11-01

    Caldera-forming eruptions of island volcanoes generate tsunamis by the interaction of different eruptive phenomena with the sea. Such tsunamis are a major hazard, but forward models of their impacts are limited by poor understanding of source mechanisms. The caldera-forming eruption of Santorini in the Late Bronze Age is known to have been tsunamigenic, and caldera collapse has been proposed as a mechanism. Here, we present bathymetric and seismic evidence showing that the caldera was not open to the sea during the main phase of the eruption, but was flooded once the eruption had finished. Inflow of water and associated landsliding cut a deep, 2.0-2.5 km3, submarine channel, thus filling the caldera in less than a couple of days. If, as at most such volcanoes, caldera collapse occurred syn-eruptively, then it cannot have generated tsunamis. Entry of pyroclastic flows into the sea, combined with slumping of submarine pyroclastic accumulations, were the main mechanisms of tsunami production.

  14. Martian Hot Springs? Silica deposits in the Nili Patera Caldera.

    Science.gov (United States)

    Skok, J. R.; Mustard, J. F.; Ehlmann, B. L.; Murchie, S. L.

    2011-12-01

    The caldera of the Syrtis Major volcanic complex shows evidence of a late-stage, chemically evolved eruption that emplaced a volcanic cone and an evolved dacitic lava flow. This cone and flow contain several light-toned deposits, spectrally defined, with the CRISM instrument, by a broad asymmetrical absorption centered at 2.21 μm that is characteristic of a Si-OH bond. Additional weak 1.4 and 1.9 μm OH- and H2O related absorption features were detected that combined with the 2.21 μm feature confirms the detection of hydrated silica (SiO2 nH2O). The deposits are expressed morphologically as low mounds in stereo HiRISE data that superpose and post-date the volcanic flows. This mineral detection and volcanic context is consistent with several formation mechanisms, notably volcanic outgassing leading to fumarole surface alteration or silica deposition in volcanically driven hot springs. Since current orbital observations do not allow conclusive determination of precise mechanism, we here focus on the hot spring silica depositional hypothesis and investigate what the current observations tell us about such a system. These deposits would occur as post-eruption volcanic heat-driven hydrothermal convection of ground and possibly magmatic waters. Convecting, heated water would dissolve the igneous minerals in the basalt that forms the majority of the caldera mobilizing significant silica. Silica saturated fluids that reach the surface cool and deposit amorphous silica as the silica solubility in the fluids decreases. The large size and mound building nature of individual deposits require a significant and sustained fluid source for deposition. That amorphous silica deposits were detected in several distinct regions illustrates the prevalence of this process in this volcanic complex. The largest deposit is located on the southern flank of the cone and forms a fan-shaped morphology as the material is sourced from a vent and flows downslope. Another small deposit was

  15. The confirmation of a work hypothesis: a new caldera in the center of the Mexican Volcanic Belt; La confirmacion de una hipotesis de trabajo: una nueva caldera en el centro del Cinturon Volcanico Mexicano

    Energy Technology Data Exchange (ETDEWEB)

    Anguita Virella, Francisco; Pal Verma, Surendra; Milan, Marcos; Garcia Cacho, Luis; Samaniego M, Daniel [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)

    1991-12-31

    After synthesizing the most relevant aspects of the current volcanology and the genesis process of the collapse calderas, a process is described on the location and confirmation of a new caldera (the Mazahua) in the central part of the Mexican Volcanic Belt (MVB). [Espanol] Tras sintetizar los aspectos mas destacados de la vulcanologia actual y el proceso de genesis de las calderas de colapso, se describe el proceso de localizacion y confirmacion de una nueva caldera (la Mazahua) en la parte central del Cinturon Volcanico Mexicano (CVM).

  16. Building and interpreting a database to understand recent caldera unrest from monitoring data

    Science.gov (United States)

    Di Lorenzo, Riccardo; Acocella, Valerio; Scandone, Roberto; Geshi, Nobuo

    2014-05-01

    Calderas are among the most spectacular, dangerous and active volcanoes on the Earth. Activation of seismicity, surface deformation and anomalous degassing are commonly observed at many calderas, denoting unrest. The unrest can be intermittent, lasting for months to years, or persistent, over decades to centuries. Although most caldera unrest episodes do not lead to an eruption, the possibility of an impending eruption warrants detailed monitoring and study. To better understand caldera unrest, we built a database from all available publications and reports on the recent unrest episodes at calderas in the world. We focused our attention on the unrest episodes which have occurred in the last 25 years, being complementary to Newhall and Dzurisin (1988). We considered the monitoring data from more than 45 unresting calderas, 35 of which characterized by eruptions. Attention has been given to seismicity, deformation and gas variations, along with their possible interaction. The database consists of an excel sheet containing the: (a) caldera descriptive parameters (caldera name, UTM coordinates, maximum and minimum diameter, area, date of last eruption, magma composition); (b) seismic data (width, maximum and minimum depth of area undergoing seismicity, frequency and duration and maximum magnitude; (c) geodetic data (location and width of deformed area, intensity and duration of the deformation); (d) geochemical data (location of anomalies, changes in maximum temperature, variations in chemical composition, duration of the anomaly, pH changes); (e) presence of eruptions and their characterization. The preliminary analysis of the database confirms that all eruptions are preceded by an unrest episode, but not all unrest episodes culminate in an eruption; this suggests that these indicators are a necessary condition to establish the state of unrest, which may anticipate an impending eruption; however, the indicators are not always adequate to determine the occurrence of

  17. Geochemical and geochronologic data from the Hall Creek caldera, Toiyabe Range, Nevada

    Science.gov (United States)

    Colgan, Joseph P.; Henry, Christopher D.

    2017-01-01

    The magmatic, tectonic, and topographic evolution of what is now the northern Great Basin remains controversial, notably the temporal and spatial relation between magmatism and extensional faulting. This controversy is exemplified in the northern Toiyabe Range of central Nevada, where previous geologic mapping suggested the presence of a caldera that sourced the late Eocene (34.0 mega-annum [Ma]) tuff of Hall Creek. This region was also inferred to be the locus of large-magnitude middle Tertiary extension (more than 100 percent strain) localized along the Bernd Canyon detachment fault, and to be the approximate location of a middle Tertiary paleodivide that separated east and west-draining paleovalleys. Geologic mapping, 40Ar/39Ar dating, and geochemical analyses document the geologic history and extent of the Hall Creek caldera, define the regional paleotopography at the time it formed, and clarify the timing and kinematics of post-caldera extensional faulting. During and after late Eocene volcanism, the northern Toiyabe Range was characterized by an east-west trending ridge in the area of present-day Mount Callaghan, probably localized along a Mesozoic anticline. Andesite lava flows erupted around 35–34 Ma ponded hundreds of meters thick in the erosional low areas surrounding this structural high, particularly in the Simpson Park Mountains. The Hall Creek caldera formed ca. 34.0 Ma during eruption of the approximately 400 cubic kilometers (km3) tuff of Hall Creek, a moderately crystal-rich rhyolite (71–77 percent SiO2) ash-flow tuff. Caldera collapse was piston-like with an intact floor block, and the caldera filled with thick (approximately 2,600 meters) intracaldera tuff and interbedded breccia lenses shed from the caldera walls. The most extensive exposed megabreccia deposits are concentrated on or close to the caldera floor in the southwestern part of the caldera. Both silicic and intermediate post-caldera lavas were locally erupted within 400 thousand

  18. Hacia un modelo etnológico de la reciprocidad desde el paradigma pilagá del intercambio

    Directory of Open Access Journals (Sweden)

    Fernando Lynch

    2002-12-01

    Full Text Available

    Se propone una reflexión sobre la significación etnológica del principio de reciprocidad a través de la consideración de un caso etnográfico particular: el modo en que los aborígenes pilagá practican y conciben el intercambio de bienes. Se parte de un paradigma antropológico que, de acuerdo a una postulación dialógica de la praxis investigativa, define a su objeto en términos de la relación establecida entre los otros étnicos y nosotros. Este primer nivel de distinción cognoscitiva se corresponde con una orientación metodológica concebida pues como un ejercicio de “reciprocidad de perspectivas”. El segundo nivel se desarrolla en función de circunscribir el objeto específico de esta investigación en términos de su carácter tautológico, esto es, de la articulación epistemológica de la descripción empírica y la explicación conceptual del prirncipio de reciprocidad. En tercera instancia, a través de una interpretación dialéctica de la explicación y la comprensión, se tiende hacia la aprehensión de la semántica de profundidad de la lógica de la circulación de bienes en términos de la jerarquía reciprocitaria consignada “entre” ellos y nosotros.

  19. Stratigraphy of Pyroclastic Deposits of EL Aguajito Caldera, Baja California Sur, MÉXICO

    Science.gov (United States)

    Osorio Ocampo, L. S.; Macias, J. L.; García Sánchez, L.; Pola, A.; Saucedo, R.; Sánchez, J. M.; Avellán, D. R.; Cardona, S.; Reyes-Agustín, G.; Arce, J. L.

    2015-12-01

    El Aguajito caldera is located in the State of Baja California Sur, it comprises an area of 450 km2 and sits within the Santa Rosalía Basin which is controlled by NE-SW extensional structures and the NW-SE Cimarron Fault that transects the caldera structure. The oldest rocks are ~90 Ma granodiorites covered by an Oligocene-Miocene volcano-sedimentary sequence, the Miocene Santa Lucia Formation and La Esperanza basalt. Pliocene volcanism is represented by La Reforma caldera, El Aguajito caldera, and the Tres Vírgenes Volcanic complex. This study focuses on the cartography and stratigraphy of area in order to understand the evolution of the volcanic system. The stratigraphy from base to top consists of a series of shallow marine sediments (fossiliferous sandstones) covered by a thick sequence of ignimbrites and pyroclastic flows interbedded with volcaniclastic deposits (Gloria and El Infierno Formations). On top of these deposits is El Aguajito caldera, it consists of a 2 m thick pumice fallout followed by an ignimbrite with three transitional lithofacies: a ≤30-m thick light-pink pyroclastic flow enriched in pumice at the base that gradually becomes enrich in lithics towards the top with the occurrence of degasing pipes. On top rests a 15 m-thick light-purple ignimbrite slightly welded with fiammes and a sequence of pumiceous pyroclastic flows and fallouts. These deposits have been associate to the caldera formation with a collapse diameter of ~8 km marked by rhyolitic domes exposed along a ring collapse crowned the sequence as well as NW-SE aligned rhyolitic domes parallel to the seashore. This cartography allowed to present a preliminary new geological map with four stratigraphic units recognized so far, that were emplaced under subaerial conditions beginning with a Plinian column followed by the emplacement of El Aguajito ignimbrite with its subsequent caldera collapse and finally the extrusion of resurgent domes.

  20. The Tala Tuff, La Primavera caldera Mexico. Pre-eruptive conditions and magma processes before eruption

    Science.gov (United States)

    Sosa-Ceballos, G.

    2015-12-01

    La Primavera caldera, Jalisco Mexico, is a Pleistocenic volcanic structure formed by dome complexes and multiple pyroclastic flows and fall deposits. It is located at the intersection of the Chapala, Colima, and Tepic grabens in western Mexico. The first volcanic activity associated to La Primavera started ~0.1 Ma with the emission of pre-caldera lavas. The caldera collapse occurred 95 ka and is associated to the eruption of ~20 km3of pumice flows known as the Tala tuff (Mahood 1980). The border of the caldera was replaced by a series of domes dated in 75-30 ky, which partially filled the inner depression of the caldera with pyroclastic flows and falls. For more than a decade the Federal Commission of Electricity in Mexico (CFE) has prospected and evaluated the geothermal potential of the Cerritos Colorados project at La Primavera caldera. In order to better understand the plumbing system that tapped the Tala tuff and to investigate its relation with the potential geothermal field at La Primavera we performed a series of hydrothermal experiments and studied melt inclusions hosted in quartz phenocrysts by Fourier Infra red stectroscopy (FTIR). Although some post caldera products at La Primavera contain fayalite and quartz (suggesting QFM conditions) the Tala tuff does not contain fayalite and we ran experiments under NNO conditions. The absence of titanomagnetite does not allowed us to calculate pre-eruptive temperature. However, the stability of quartz and plagioclase, which are natural phases, suggest that temperature should be less than 750 °C at a pressure of 200 MPa. The analyses of H2O and CO2 dissolved in melt inclusions yielded concentrations of 2-5 wt.% and 50-100 ppm respectively. This data confirm that the pre-eruptive pressure of the Tala tuff is ~200 MPa and in addition to major elements compositions suggest that the Tala tuff is either, compositionally zoned or mixed with other magma just prior to eruption.

  1. Geologic map of the Cochetopa Park and North Pass Calderas, northeastern San Juan Mountains, Colorado

    Science.gov (United States)

    Lipman, Peter W.

    2012-01-01

    The San Juan Mountains in southwestern Colorado have long been known as a site of exceptionally voluminous mid-Tertiary volcanism, including at least 22 major ignimbrite sheets (each 150-5,000 km3) and associated caldera structures active at 33-23 Ma. Recent volcanologic and petrologic studies in the San Juan region have focused mainly on several ignimbrite-caldera systems: the southeastern area (Platoro complex), western calderas (Uncompahgre-Silverton-Lake City), and the central cluster (La Garita-Creede calderas). Far less studied has been the northeastern San Juan region, which occupies a transition between earlier volcanism in central Colorado and large-volume younger ignimbrite-caldera foci farther south and west. The present map is based on new field coverage of volcanic rocks in seventeen 7.5' quadrangles in northeastern parts of the volcanic field, high-resolution age determinations for 120 new sites, and petrologic studies involving several hundred new chemical analyses. This mapping and the accompanying lab results (1) document volcanic evolution of the previously unrecognized North Pass caldera and the morphologically beautifully preserved but enigmatic Cochetopa basin, including unique features not previously described from ignimbrite calderas elsewhere; (2) provide evidence for a more rapid recurrence of large ignimbrite eruptions than previously known elsewhere; (3) quantify the regional time-space-volume progression from the earlier Sawatch magmatic trend southward into the San Juan region; and (4) permit more rigorous comparison between the broad mid-Tertiary magmatic belt in the western U.S. Cordillera and the type continental-margin arc volcanism in the central Andes.

  2. MGS-TES thermal inertia study of the Arsia Mons Caldera

    Science.gov (United States)

    Cushing, G.E.; Titus, T.N.

    2008-01-01

    Temperatures of the Arsia Mons caldera floor and two nearby control areas were obtained by the Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES). These observations revealed that the Arsia Mons caldera floor exhibits thermal behavior different from the surrounding Tharsis region when compared with thermal models. Our technique compares modeled and observed data to determine best fit values of thermal inertia, layer depth, and albedo. Best fit modeled values are accurate in the two control regions, but those in the Arsia Mons' caldera are consistently either up to 15 K warmer than afternoon observations, or have albedo values that are more than two standard deviations higher than the observed mean. Models of both homogeneous and layered (such as dust over bedrock) cases were compared, with layered-cases indicating a surface layer at least thick enough to insulate itself from diurnal effects of an underlying substrate material. Because best fit models of the caldera floor poorly match observations, it is likely that the caldera floor experiences some physical process not incorporated into our thermal model. Even on Mars, Arsia Mons is an extreme environment where CO2 condenses upon the caldera floor every night, diurnal temperatures range each day by a factor of nearly 2, and annual average atmospheric pressure is only around one millibar. Here, we explore several possibilities that may explain the poor modeled fits to caldera floor and conclude that temperature dependent thermal conductivity may cause thermal inertia to vary diurnally, and this effect may be exaggerated by presence of water-ice clouds, which occur frequently above Arsia Mons. Copyright 2008 by the American Geophysical Union.

  3. Gravity modelling of the Ramadas Caldera (Argentinean Puna, central Andes)

    Energy Technology Data Exchange (ETDEWEB)

    Casas, A. [Barcelona Univ. (Spain). Facultad de Geologia; Hernandez, E.; Marti, J. [Consejo Superior de Investigaciones Cientificas, Barcelona (Spain). Inst. de Ciencias de la Terra Jaume Almera; Petrinovic, I. [Universidad Nacional de Salta (Argentina)

    1995-12-31

    In order to identify and characterize the event area of abundant Upper Miocene proximal rhyolitic pyroclastic deposits and extrusive domes which concentrate in the Ramadas area, near Sant`Antonio de los Cobres (Salta) at the Puna Altiplano (Central Andes), a detailed gravity survey has been carried out. Regional Bouguer gravity data were augmented with new 173 gravity observations measured sufficiently close-spaced to resolve the short wavelength produced by the structure of interest. Besides, the geophysical survey was done in conjunction with geologic and geochemical studies which were critically important to our interpretation. After the separation of the regional trend, the residual anomaly map displays a circular gravity low reaching-80 m Gal centered over scarce outcrops of rhyolitic and pyroclastic. This gravity low is interpreted as produced by block subsidence along ring fractures during eruption and/or deflation of the chamber. As the accumulation of thick, low density rock types in the zone of collapse is responsible of the prominent negative gravity anomalies, them has been used to estimated the thickness of caldera infill. (author). 8 refs., 4 figs

  4. Volcanic calderas delineate biogeographic provinces among Yellowstone thermophiles.

    Science.gov (United States)

    Takacs-Vesbach, Cristina; Mitchell, Kendra; Jackson-Weaver, Olan; Reysenbach, Anna-Louise

    2008-07-01

    It has been suggested that the distribution of microorganisms should be cosmopolitan because of their enormous capacity for dispersal. However, recent studies have revealed that geographically isolated microbial populations do exist. Geographic distance as a barrier to dispersal is most often invoked to explain these distributions. Here we show that unique and diverse sequences of the bacterial genus Sulfurihydrogenibium exist in Yellowstone thermal springs, indicating that these sites are geographically isolated. Although there was no correlation with geographic distance or the associated geochemistry of the springs, there was a strong historical signal. We found that the Yellowstone calderas, remnants of prehistoric volcanic eruptions, delineate biogeographical provinces for the Sulfurihydrogenibium within Yellowstone (chi(2): 9.7, P = 0.002). The pattern of distribution that we have detected suggests that major geological events in the past 2 million years explain more of the variation in sequence diversity in this system than do contemporary factors such as habitat or geographic distance. These findings highlight the importance of historical legacies in determining contemporary microbial distributions and suggest that the same factors that determine the biogeography of macroorganisms are also evident among bacteria.

  5. Tourism Development Based on Geopark in Bakkara Caldera Toba, Indonesia

    Science.gov (United States)

    Ginting, N.; Vinky Rahman, N.; Sembiring, G.

    2017-03-01

    Bakkara Caldera Toba is an outstanding product of natural phenomena of Toba Supervolcano which has fascinating nature and culture. Bakkara has a great potential to develop world tourism further. It requires a model of sustainable planning Geopark to develop Bakkara. This sustainable concept helps to improve the local community and tourist’s quality of life and also still maintain the quality of the environment. through field observation and depth interview. The Collected data with a triangulation method. Development tourism destination such as attractions and environment; facilities and services; accessibility; image; and price to consume. It associated based on Geopark aspects there are; geological heritage; geo-conservation activities; sustainable tourism activities; educational; activities; community involvement products; strong management structure; and secure basis, infrastructure, and activities. The results of this study indicate that the Bakkara has the potential to become a tourist destination by applying the concept of Geotourism which accentuate its natural side, by optimizing the management of its destination attractions, its facilities and services, and its accessibilities.

  6. Stress field control during large caldera-forming eruptions

    Directory of Open Access Journals (Sweden)

    Antonio Costa

    2016-10-01

    Full Text Available Crustal stress field can have a significant influence on the way magma is channelled through the crust and erupted explosively at the surface. Large Caldera Forming Eruptions (LCFEs can erupt hundreds to thousands of cubic kilometres of magma in a relatively short time along fissures under the control of a far-field extensional stress. The associated eruption intensities are estimated in the range 109 - 1011 kg/s. We analyse syn-eruptive dynamics of LCFEs, by simulating numerically explosive flow of magma through a shallow dyke conduit connected to a magma chamber that in turn is fed by a deeper magma reservoir, both under the action of an extensional far-field stress. Results indicate that huge amounts of high viscosity silicic magma can be erupted over timescales of a few to several hours. Our study provides answers to outstanding questions relating to the intensity and duration of catastrophic volcanic eruptions in the past. In addition, it presents far-reaching implications for the understanding of dynamics and intensity of large-magnitude volcanic eruptions on Earth and to highlight the necessity of a future research to advance our knowledge of these rare catastrophic events.

  7. Stress field control during large caldera-forming eruptions

    Science.gov (United States)

    Costa, Antonio; Marti, Joan

    2016-10-01

    Crustal stress field can have a significant influence on the way magma is channelled through the crust and erupted explosively at the surface. Large Caldera Forming Eruptions (LCFEs) can erupt hundreds to thousands of cubic kilometres of magma in a relatively short time along fissures under the control of a far-field extensional stress. The associated eruption intensities are estimated in the range 109 - 1011 kg/s. We analyse syn-eruptive dynamics of LCFEs, by simulating numerically explosive flow of magma through a shallow dyke conduit connected to a magma chamber that in turn is fed by a deeper magma reservoir, both under the action of an extensional far-field stress. Results indicate that huge amounts of high viscosity silicic magma can be erupted over timescales of a few to several hours. Our study provides answers to outstanding questions relating to the intensity and duration of catastrophic volcanic eruptions in the past. In addition, it presents far-reaching implications for the understanding of dynamics and intensity of large-magnitude volcanic eruptions on Earth and to highlight the necessity of a future research to advance our knowledge of these rare catastrophic events.

  8. Eruptive and noneruptive calderas, northeastern San Juan Mountains, Colorado: Where did the ignimbrites come from?

    Science.gov (United States)

    Lipman, P.W.; McIntosh, W.C.

    2008-01-01

    The northeastern San Juan Mountains, the least studied portion of this well-known segment of the Southern Rocky Mountains Volcanic Field are the site of several newly identified and reinterpreted ignimbrite calderas. These calderas document some unique eruptive features not described before from large volcanic systems elsewhere, as based on recent mapping, petrologic data, and a large array of newly determined high-precision, laser-fusion 40Ar/39Ar ages (140 samples). Tightly grouped sanidine ages document exceptionally brief durations of 50-100 k.y. or less for individual Oligocene caldera cycles; biotite ages are more variable and commonly as much as several hundred k.y. older than sanidine from the same volcanic unit. A previously unknown ignimbrite caldera at North Pass, along the Continental Divide in the Cochetopa Hills, was the source of the newly distinguished 32.25-Ma Saguache Creek Tuff (???400-500 km3). This regionally, distinctive crystal-poor alkalic rhyolite helps fill an apparent gap in the southwestward migration from older explosive activity, from calderas along the N-S Sawatch locus in central Colorado (youngest, Bonanza Tuff at 33.2 Ma), to the culmination of Tertiary volcanism in the San Juan region, where large-volume ignimbrite eruptions started at ca. 29.5 Ma and peaked with the enormous Fish Canyon Tuff (5000 km3) at 28.0 Ma. The entire North Pass cycle, including caldera-forming Saguache Creek Tuff, thick caldera-filling lavas, and a smaller volume late tuff sheet, is tightly bracketed at 32.25-32.17 Ma. No large ignimbrites were erupted in the interval 32-29 Ma, but a previously unmapped cluster of dacite-rhyolite lava flows and small tuffs, areally associated with a newly recognized intermediate-composition intrusion 5 ?? 10 km across (largest subvolcanic intrusion in San Juan region) centered 15 km north of the North Pass caldera, marks a near-caldera-size silicic system active at 29.8 Ma. In contrast to the completely filled North Pass

  9. Magma Storage, Recharge and the Caldera Cycle at Rabaul, Papua New Guinea

    Science.gov (United States)

    Fabbro, G.; Bouvet de Maisonneuve, C.; Sindang, M.

    2015-12-01

    Many calderas have a history of repeated caldera-forming eruptions, interspersed with periods of more minor activity. Rabaul, for instance, has had at least 11 ignimbrite-forming eruptions over the last 200 ky. The most recent of these was the '1400 BP' eruption, which led to caldera collapse. Since then, there has been multiple smaller eruptions, including the ongoing activity from Tavurvur and Vulcan. An important question facing volcanology today is what controls the size of eruptions at calderas such as Rabaul.Detailed stratigraphic sampling of the 1400BP eruption reveals that prior to eruption, the magma reservoir below Rabaul contained a well-mixed dacite with whole-rock SiO2 contents of 65.0-66.4 wt%. The dacite contains a single phenocryst assemblage of plag (An44-52), cpx (En43-46Fs13-15Wo40-41), opx (En69-71Fs25-28Wo3) and magnetite, along with minor apatite. The homogeneity of the dacite is underscored by the narrow range of compositions of both the matrix glass and the melt inclusions (67.8-69.0 wt% SiO2). The only exception to this is at the top of the ignimbrite, representing some of the last magma to have been withdrawn. Dispersed throughout the dacitic pumices are darker, more mafic blebs. Streaks of mingled magma with a range of SiO2 contents, down to 59.9 wt% SiO2 are also found in the pumice, suggesting that a mafic recharge magma was intruded into the base of the reservoir shortly before eruption. High TiO2 contents rule out the direct involvement of basalt, and instead imply the magma that intruded into the reservoir was an andesite with at least 56 wt% SiO2. Phenocrysts related to this recharge magma are rare, and the crystals found in the dark blebs are identical in composition to those found in the dacite, indicating that the recharge was aphyric. The present-day, post-caldera recharge magma is different to the pre-1400 BP recharge magma: it is basaltic. This suggests that the plumbing system of Rabaul is different during the pre-caldera and

  10. Long Valley caldera and the UCERF depiction of Sierra Nevada range-front faults

    Science.gov (United States)

    Hill, David P.; Montgomery-Brown, Emily K.

    2015-01-01

    Long Valley caldera lies within a left-stepping offset in the north-northwest-striking Sierra Nevada range-front normal faults with the Hilton Creek fault to the south and Hartley Springs fault to the north. Both Uniform California Earthquake Rupture Forecast (UCERF) 2 and its update, UCERF3, depict slip on these major range-front normal faults as extending well into the caldera, with significant normal slip on overlapping, subparallel segments separated by ∼10  km. This depiction is countered by (1) geologic evidence that normal faulting within the caldera consists of a series of graben structures associated with postcaldera magmatism (intrusion and tumescence) and not systematic down-to-the-east displacements consistent with distributed range-front faulting and (2) the lack of kinematic evidence for an evolving, postcaldera relay ramp structure between overlapping strands of the two range-front normal faults. The modifications to the UCERF depiction described here reduce the predicted shaking intensity within the caldera, and they are in accord with the tectonic influence that underlapped offset range-front faults have on seismicity patterns within the caldera associated with ongoing volcanic unrest.

  11. Gravity field at unrest caldera: an application to Campi Flegrei area

    Science.gov (United States)

    Russo, Guido; Capuano, Paolo

    2010-05-01

    Campi Flegrei is a well known volcanic caldera which is characterized by a slow sequence of uplifts and downlifts (bradyseism) superimposed to a sporadic but remarkable explosive activity. Last eruption occurred in 1538, while the most recent uplift episodes (1970-72 and 1982-84) produced about 3 m of cumulative displacement at the town of Pozzuoli. This behavior and the proximity of the densely urbanized town of Naples increases the volcanic hazard of the area. The knowledge of the structural characteristics of the caldera is important to better understand and interpret measured data as well as the past volcanic history. In this frame, gravity data inversion can provide useful information. We collected and inverted about 1500 gravity data covering Campi Flegrei caldera and Ischia island, which is the other main volcanic center of the area, and was characterized in the past by several explosive eruptions (the last one in 1301), and presently by hydrothermal activity. The 3D inversion method was developed by us to deal with scattered data and the presence of topography, and is based on Thichonov regularization theory. As to Campi Flegrei caldera, its shape and bordering structure is clearly singled out in agreement with seismic tomography results. Less marked borders are also present at shallow depth on the NE part of the area. As to Ischia island, our results show the presence of a central high density block and the border of a caldera roughly coinciding with the coastline of the island.

  12. Geologic Map of the Central San Juan Caldera Cluster, Southwestern Colorado

    Science.gov (United States)

    Lipman, Peter W.

    2006-01-01

    The San Juan Mountains are the largest erosional remnant of a composite volcanic field that covered much of the southern Rocky Mountains in middle Tertiary time. The San Juan field consists mainly of intermediate-composition lavas and breccias, erupted about 35-30 Ma from scattered central volcanoes (Conejos Formation) and overlain by voluminous ash-flow sheets erupted from caldera sources. In the central San Juan Mountains, eruption of at least 8,800 km3 of dacitic-rhyolitic magma as nine major ash flow sheets (individually 150-5,000 km3) was accompanied by recurrent caldera subsidence between 28.3 Ma and about 26.5 Ma. Voluminous andesitic-dacitic lavas and breccias 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 more silicic explosive volcanism. Exposed calderas vary in size from 10 to 75 km in maximum dimension; the largest calderas are associated with the most voluminous eruptions.

  13. Un final abierto: circulación, colaboración e intercambio en las prácticas sonoras independientes a través de Internet

    Directory of Open Access Journals (Sweden)

    Ana María Romano G.

    2015-09-01

    Internet se ha constituido en un entorno en el que pueden confluir almacenamiento, difusión y distribución, por ello es fácil entender que goce de gran aceptación, pues día a día se fortalece como una tecnología que favorece  el intercambio y la colaboración musical. Internet, el gran aliado de las iniciativas independientes, ha ayudado a que lleguen a diversos públicos, muchas veces insospechados, y ha dado lugar a un empoderamiento sorprendente de los movimientos que reivindican la autogestión.

  14. Recordatorio para mejorar el intercambio en las listas profesionales de Veterinaria.org y hacer mejor uso de los boletines informativos

    OpenAIRE

    Veterinaria.org

    2008-01-01

    ResumenRecordar que los mensajes se deberían enviar a la lista más adecuada, así por ejemplo los casos clínicos específicos a L_Cons, los de temas profesionales generales a L_VET, los de asuntos informales a L_SOCIAL, etc, y no utilizar para ello los boletines, que están destinados para otro uso. Las especificaciones de cada lista de intercambio y boletines informativos están en http://www.veterinaria.org/listasyboletines

  15. Recordatorio para mejorar el intercambio en las listas profesionales de Veterinaria.org y hacer mejor uso de los boletines informativos

    Directory of Open Access Journals (Sweden)

    Veterinaria.org

    2008-02-01

    Full Text Available ResumenRecordar que los mensajes se deberían enviar a la lista más adecuada, así por ejemplo los casos clínicos específicos a L_Cons, los de temas profesionales generales a L_VET, los de asuntos informales a L_SOCIAL, etc, y no utilizar para ello los boletines, que están destinados para otro uso. Las especificaciones de cada lista de intercambio y boletines informativos están en http://www.veterinaria.org/listasyboletines

  16. Perspectivas de integración energética México- norteamericana: Intercambios de electricidad y gas natural en el noroeste mexicano

    Directory of Open Access Journals (Sweden)

    Agustín Sández Pérez

    1992-09-01

    Full Text Available Históricamente, la relación comercial México-norteamericana en el plano energético ha sido hegemonizada por el intercambio de hidrocarburos. En épocas de conflagración mundial, y más recientemente de conflictos bélicos en el Medio Oriente, el acceso preferencial a este recurso ha representado un factor importante de tensión para México. Fuera de las etapas de tensión, tal intercambio continúa siendo eje de la negociación comercial y aún más lejos, ha llegado a ocupar en algunos periodos un rol clave en la planeación económica global de la nación. Esta relación abrumadora, que parece privilegiar a toda costa el examen del intercambio petrolero en la relación comercial bilateral es, en cambio, ajena y distante al panorama social y productivo de la frontera norte y muy especialmente del noroeste mexicano. En éste, el intercambio energético se circunscribe hoya la venta de electricidad hacia el norte y la venta de gas natural hacia el sur de la frontera entre ambos países. El seguimiento de los circuitos eléctricos interconectados entre Baja California y California es un proceso relativamente reciente. Hacia mediados de los ochenta se realizaron las negociaciones entre autoridades y representantes de ambos países. Esta negociación reflejó, a su vez, la disparidad organizacional de la producción eléctrica. Más recientemente se han establecido programas y políticas destinadas al uso eficiente de la energía. A la vez se presencian procesos paralelos de gran trascendencia. Una de las alternativas que se discuten hoy para el abatimiento de costos de producción es la utilización del gas natural como alimento de la termoelectricidad a fin de sostener la capacidad instalada y asegurar la exportación.

  17. Las relaciones de poder en los intercambios comerciales de la cadena productiva del tequila y su incidencia en la competitividad de la rama industrial

    OpenAIRE

    Orozco-Martínez, José L.

    2011-01-01

    Las relaciones de poder permean todo el ámbito de la interacción humana, individualmente o en grupos. Estas relaciones se dan en situaciones concretas que influyen, y en muchos casos determinan, el resultado de dicha interacción, dependiendo de las fuentes de poder de los respectivos interactuantes, y la capacidad y forma en que éstos utilizan dicho poder en situaciones particulares. Los ejercicios del poder se hacen patentes en las relaciones de intercambio comercial de la ...

  18. «Haciendo amigos»: intercambios educativos hispano-estadounidenses en clave política, 1959-1968

    Directory of Open Access Journals (Sweden)

    Francisco RODRÍGUEZ JIMÉNEZ

    2009-03-01

    Full Text Available RESUMEN: La dimensión cultural de la relación hispano-estadounidense durante el franquismo ha sido poco estudiada. Sin embargo, tuvo un papel importante e influyó notablemente en los aspectos políticos, militares, económicos, etc., de aquella conexión. Dentro de aquel ámbito, un episodio destacado fue el establecimiento del programa de cooperación e intercambio educativo y científico de becas Fulbright. Para gestionarlo se creó una comisión binacional. Pese a determinadas declaraciones iniciales de supuesta sintonía entre las partes, los agentes diplomáticos de Washington tenían unas expectativas y prioridades bastante diferentes de las que albergaban sus homólogos de Madrid. Las estadounidenses se centraron en potenciar la enseñanza del inglés y de los Estudios Norteamericanos, American Studies, en las universidades de nuestro país. Las españolas, en poder beber de los prestigiosos centros de conocimiento técnico y científico existentes en los Estados Unidos. Hemos analizado, tomando como ejemplo el caso de la Universidad de Salamanca, cuáles fueron los avatares sobre el terreno y en qué grado se cumplieron los objetivos específicos estadounidenses de que sus producciones humanísticas fueran entendidas y estudiadas en España.ABSTRACT: Cultural aspects of the Spanish-Northamerican relations during the Franco’s regime have been scarcely studied. Nevertheless, they played an important role and influenced notably the political, military and economic aspects of that connection. Inside that context, an outstanding episode was the establishment of the Fulbright grants, a program of cooperation and of educational and scientific scholarship exchange. A binational commission was created in order to manage this project. Despite certain initial declarations of a supposed perfect understanding between the two parts, the diplomatic agents of Washington had quite different expectations and priorities from those that their

  19. Revised volcanic history of the San Juan, Uncompahgre, Silverton, and Lake City calderas in the western San Juan Mountains, Colorado

    Science.gov (United States)

    Lipman, Peter W.; Steven, Thomas A.; Luedke, Robert G.; Burbank, Wilbur

    1973-01-01

    The sequence of mid-Cenozoic volcanic events in the western San Juan Mountains is closely analogous to that elsewhere in the San Juan volcanic field. The Lake Fork, Picayune, and San Juan Formations were erupted from a cluster of central volcanoes from 35 to 30 m.y. ago, when dominant activity shifted to more silicic ash-flow eruptions with accompanying caldera collapses. The Uncompahgre and San Juan calderas, each about 20 km across, formed mainly from eruption of the 28-m.y.-old Sapinero Mesa Tuff. Collapse occurred concurrently with eruption, and intracaldera tuffs accumulated to a thickness of more than 700 m. Both calderas were resurgently domed together; the northeast-trending Eureka graben formed along the distended crest of that dome. The Uncompahgre caldera was then flooded by several 27- to 28-m.y.-old ash-flow sheets from easterly sources, and also by one apparently erupted from the Silverton caldera nested within the older San Juan caldera. The Lake City caldera, located within the older Uncompahgre caldera, formed about 22.5 m.y. ago in response to eruption of the Sunshine Peak Tuff.

  20. Electrical structure of Plaine des Sables caldera, Piton de la Fournaise volcano (Reunion Island

    Directory of Open Access Journals (Sweden)

    P. A. Schnegg

    1997-06-01

    Full Text Available An Audio Magnetotelluric (AMT profile has been carried out across the Plaine des Sables, a former caldera of the active Piton de la Fournaise volcano, Reunion Island. Located in the Western Indian Ocean, between the Mascarene and Madagascar basins, this basaltic shield volcano originates from the activity of a hot spot. Our aim was to determine the internal structure of the volcano, in particular the shallow electrical properties of an area extending between the old and the new caldera rims. Although several teams had already conducted AMT work in this region a few years ago, there was a need for more a detailed, in depth survey. Our final model displays a noticeable slope of the Plaine des Sables basement oriented toward the present Fournaise summit. This slope is interpreted as resulting from successive landslides toward the ocean. We conclude that this dipping, electrically good conducting layer, probably belongs to the flat layering of an older caldera.

  1. Doubly stochastic models for volcanic hazard assessment at Campi Flegrei caldera

    CERN Document Server

    Bevilacqua, Andrea

    2016-01-01

    This study provides innovative mathematical models for assessing the eruption probability and associated volcanic hazards, and applies them to the Campi Flegrei caldera in Italy. Throughout the book, significant attention is devoted to quantifying the sources of uncertainty affecting the forecast estimates. The Campi Flegrei caldera is certainly one of the world’s highest-risk volcanoes, with more than 70 eruptions over the last 15,000 years, prevalently explosive ones of varying magnitude, intensity and vent location. In the second half of the twentieth century the volcano apparently once again entered a phase of unrest that continues to the present. Hundreds of thousands of people live inside the caldera and over a million more in the nearby city of Naples, making a future eruption of Campi Flegrei an event with potentially catastrophic consequences at the national and European levels.

  2. Crustal magma pathway beneath Aso caldera inferred from three-dimensional electrical resistivity structure

    Science.gov (United States)

    Hata, Maki; Takakura, Shinichi; Matsushima, Nobuo; Hashimoto, Takeshi; Utsugi, Mitsuru

    2016-10-01

    At Naka-dake cone, Aso caldera, Japan, volcanic activity is raised cyclically, an example of which was a phreatomagmatic eruption in September 2015. Using a three-dimensional model of electrical resistivity, we identify a magma pathway from a series of northward dipping conductive anomalies in the upper crust beneath the caldera. Our resistivity model was created from magnetotelluric measurements conducted in November-December 2015; thus, it provides the latest information about magma reservoir geometry beneath the caldera. The center of the conductive anomalies shifts from the north of Naka-dake at depths >10 km toward Naka-dake, along with a decrease in anomaly depths. The melt fraction is estimated at 13-15% at 2 km depth. Moreover, these anomalies are spatially correlated with the locations of earthquake clusters, which are distributed within resistive blocks on the conductive anomalies in the northwest of Naka-dake but distributed at the resistive sides of resistivity boundaries in the northeast.

  3. The 2014-2015 slow collapse of the Bárðarbunga caldera, Iceland

    Science.gov (United States)

    Tumi Gudmundsson, Magnus; Jónsdóttir, Kristín; Roberts, Matthew; Ófeigsson, Benedikt G.; Högnadóttir, Thórdís; Magnússon, Eyjólfur; Jarosch, Alexander H.; Pálsson, Finnur; Einarsson, Páll; Sigmundsson, Freysteinn; Drouin, Vincent; Hjörleifsdóttir, Vala; Reynolds, Hannah I.; Dürig, Tobias; Vogfjörd, Kristín; Hensch, Martin; Munoz-Cobo Belart, Joaquin; Oddsson, Björn

    2015-04-01

    The Bárðarbunga caldera is located in central Iceland, under in NW corner of Vatnajökull ice cap. The caldera is about 65 km2 in area, with 500-600 m high topographic rims and is fully covered with up to 800 m thick ice. On 16 August 2014 an intense earthquake swarm started in Bárðarbunga, the beginning of a major volcano-tectonic rifting event forming a 45 km long dyke extending from the caldera to Holuhraun lava field outside the northern margin of Vatnajökull (Sigmundsson et al., 2014). A large basaltic, effusive fissure eruption began in Holuhraun on 31 August that by January had formed a lava field of volume in excess of one cubic kilometre. The collapse of the caldera is expected to have begun a few days after the onset of the earthquake swarm, probably coinciding with the first M5 earthquake. This slow caldera collapse has been monitored through repeated mapping of the gradually increasing subsidence bowl (~80 km2 in December) with airborne profiling of the ice surface, satellite mapping, an online GPS station set up in September on the glacier surface in the centre of the caldera with a strong motion sensor added in November, and indirectly through recording of seismic activity. Satellite interferograms constrain both ice movements and the rate of collapse. The rate of collapse was greatest in the first two weeks or 0.5-1 m/day in the centre, but has since gradually declined with time. The daily rate was 0.1-0.2 m/day in January, when the maximum lowering had reached about 60 m. A gradual widening of the subsidence bowl has been observed since early September. It is asymmetric, deepest in the NE part of the caldera. Downwards displacement extends outside the pre-existing topographic caldera rims, particularly on the south side where the rims have subsided by over 10 meters. Ice-flow modelling indicates that the ice is mostly passively subsiding with the caldera floor. Thus, horizontal ice flow has had little effect on the shape of the subsidence bowl

  4. Scientific core hole Valles caldera No. 2b (VC-2b), New Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Garner, J.N.; Hulen, J.B.; Lysne, P.; Jacobson, R.; Goff, F.; Nielson, D.L.; Pisto, L.; Criswell, C.W.; Gribble, R. (Los Alamos National Lab., NM (USA); Utah Univ. Research Inst., Salt Lake City, UT (USA); Sandia National Labs., Albuquerque, NM (USA); Los Alamos National Lab., NM (USA); Utah Univ. Research Inst., Salt Lake City, UT (USA); Tonto Drilling Services, Inc., Salt Lake City, UT (USA); Los Alamo

    1989-01-01

    Research core hole was continuously cored to 1.762 km on the western flank of the caldera's resurgent dome in 1988. Bottom hole temperature is about 295{degree}C within Precambrian (1.5 Ga) quartz monzonite, deep within the liquid-dominated portions of the Sulphur Springs hydrothermal system. VC-2b may be the deepest, hottest, continuously cored hole in North America. Core recovery was 99.2%. The only major drilling problems encountered were when temperatures at the bit exceeded 225{degree}C below depths of about 1000 m. The result of these conditions was loss of viscosity and/or lubricity in the mud, apparently caused by breakdown of the high temperature polymers. Lithologies in caldera-fill indicate the drill site may be proximal to ignimbrite vents and that an intracaldera lake with temperatures approaching boiling formed soon after the caldera itself. Structural correlations between VC-2b and the 528-m-deep companion hole VC-2a indicate the earlier Toledo caldera (1.45 Ma; Otowi Member tuffs) and even older Lower Tuffs caldera experienced no structural resurgence similar to the 1.12 million year old Valles caldera. The hydrothermal system penetrated by these bores, consists of a shallow vapor-rich cap, which has evolved from an earlier 200{degree}C liquid-dominated system, overlying stacked, liquid-dominated zones up to about 300{degree}C. Geochemistry of mud returns collected during drilling suggests chloride-rich geothermal fluids were entering the bore and mixing with the drilling fluids in the fractured lower Paleozoic and Precambrian sections. 23 refs., 5 figs., 1 tab.

  5. Recrystallization and anatexis along the plutonic-volcanic contact of the Turkey Creek caldera, Arizona

    Science.gov (United States)

    du Bray, E.A.; Pallister, J.S.

    1999-01-01

    Unusual geologic and geochemical relations are preserved along the contact between intracaldera tuff and a resurgent intrusion within the 26.9 Ma Turkey Creek caldera of southeast Arizona. Thick intracaldera tuff is weakly argillically altered throughout, except in zones within several hundred meters of its contact with the resurgent intrusion, where the groundmass of the tuff has been variably converted to granophyre and unaltered sanidine phenocrysts are present. Dikes of similarly granophyric material originate at the tuff-resurgent intrusion contact and intrude overlying intracaldera megabreccia and tuff. Field relations indicate that the resurgent intrusion is a laccolith and that it caused local partial melting of adjacent intracaldera tuff. Geochemical and petrographic relations indicate that small volumes of partially melted intracaldera tuff assimilated and mixed with dacite of the resurgent intrusion along their contact, resulting in rocks that have petrographic and compositional characteristics transitional between those of tuff and dacite. Some of this variably contaminated, second-generation magma coalesced, was mobilized, and was intruded into overlying intracaldera rocks. Interpretation of the resurgent intrusion in the Turkey Creek and other calderas as intracaldera laccoliths suggests that intrusions of this type may be a common, but often unrecognized, feature of calderas. Development of granophyric and anatectic features such as those described here may be equally common in other calderas. The observations and previously undocumented processes described here can be applied to identification and interpretation of similarly enigmatic relations and rocks in other caldera systems. Integration of large-scale field mapping with detailed petrographic and chemical data has resulted in an understanding of otherwise intractable but petrologically important caldera-related features.

  6. Inflation of Aira Caldera (Japan detected over Kokubu urban area using SAR interferometry ERS data

    Directory of Open Access Journals (Sweden)

    D. Remy

    2006-08-01

    Full Text Available Nine ERS-1 and ERS-2 descending orbit data acquired over the Aira Caldera between June 1995 and November 1998 were used to create 31 differential interferograms. Although the interferograms exhibit a relatively low level of coherence, even for couples sampling short time intervals (6 months, Differential Interferometric Synthetic Aperture Radar (DinSAR reveals a pattern of range change signal during the observation period in the urban area of Kokubu city. The analysis of the ground deformation time series relative to the earliest ERS images evidenced a maximum uplift of 23 mm between the north and the south of the city during the studied period. Taking the reduced surface of the coherent area into account, we performed a simple modelling of the deformation field assuming a spherical inflating source within an elastic half-space medium. This simple model predicts a source located beneath the centre of Aira Caldera with a maximum volume increase of 30 106 m3 between 1995 and 1997, which would produced an inflation of about 7 cm of the centre of Aira Caldera and 4 cm of the south of Kokubu city. These results are in good agreement with other geophysical observations carried out on Aira caldera during this unrest period. Despite the limited spatial extent of the coherent areas around Aira Caldera, this study shows that DinSAR method using ERS data can be successfully used to detect subtle ground displacement changes of the volcanic complex and thus provides complementary information to ground-based geodetic monitoring of dynamic processes at Aira Caldera and Sakurajima volcano.

  7. Rhyodacites of Kulshan caldera, North Cascades of Washington: Postcaldera lavas that span the Jaramillo

    Science.gov (United States)

    Hildreth, W.; Lanphere, M.A.; Champion, D.E.; Fierstein, J.

    2004-01-01

    Kulshan caldera (4.5??8 km), at the northeast foot of Mount Baker, is filled with rhyodacite ignimbrite (1.15 Ma) and postcaldera lavas and is only the third Quaternary caldera identified in the Cascade arc. A gravity traverse across the caldera yields a steep-sided, symmetrical, complete Bouguer anomaly of -16 mGal centered over the caldera. Density considerations suggest that the caldera fill, which is incised to an observed thickness of 1 km, may be about 1.5 km thick and is flat-floored, overlying a cylindrical piston of subsided metamorphic rocks. Outflow sheets have been stripped by advances of the Cordilleran Ice Sheet, but the climactic fallout (Lake Tapps tephra) is as thick as 30 cm some 200 km south of the caldera. Ten precaldera units, which range in 40Ar/39Ar age from 1.29 to 1.15 Ma, are dikes and erosional scraps that probably never amounted to a large edifice. A dozen postcaldera rhyodacite lavas and dikes range in age from 1.15 to 0.99 Ma; rhyodacites have subsequently been absent, the silicic reservoir having finally crystallized. At least 60 early Pleistocene intermediate dikes next intruded the caldera fill, helping energize an acid-sulfate hydrothermal system and constituting the main surviving record of an early postcaldera andesite-dacite pile presumed to have been large. Most of the pre- and postcaldera rhyodacites were dated by 40Ar/39Ar or K-Ar methods, and 13 were drilled for remanent magnetic directions. In agreement with the radiometric ages, the paleomagnetic data indicate that eruptions took place before, during, and after the Jaramillo Normal Polarity Subchron, and that one rhyodacite with transitional polarity may represent the termination of the Jaramillo. Most of the biotite-hornblende-orthopyroxene-plagioclase rhyodacite lavas, dikes, and tuffs are in the range 68-73% SiO2, but there were large compositional fluctuations during the 300-kyr duration of the rhyodacite episode. The rhyodacitic magma reservoir was wider (11 km) than

  8. Spasmodic tremor and possible magma injection in Long Valley caldera, eastern California

    Energy Technology Data Exchange (ETDEWEB)

    Ryall, A.; Ryall, F.

    1983-03-25

    Intensive microearthquake swarms with the appearance of volcanic tremor have been observed in the southwest part of Long Valley caldera, southeastern California. This activity, possibly associated with magma injection, began 6 weeks after several strong (magnitude 6+) earthquakes in an area south of the caldera and has continued sporadically to the present time. The earthquake sequence and magmatic activity are part of a broad increase in tectonic activity in a 15,000-square-kilometer region surrounding the White Mountains seismic gap, an area with high potential for the next earthquake in the western Great Basin.

  9. Identification of Calderas Associated With The Acidic Jurassic Volcanism of Southern Patagonia, Argentina

    Science.gov (United States)

    Chernicoff, C. J.; Salani, F. M.

    During the Jurassic, the Patagonian region was subject to a predominantly acidic volcanism locally known as the Chon Aike Volcanic Province, related to the breakup of Gondwana. It comprises ignimbrites, breccias and agglomerates, and a minor component of rhyolitic and dacitic lava domes. In the study area (Río Seco region, Santa Cruz Province), the Jurassic volcanics are largely overlain by Neogene and Quaternary sediments. However, the aeromagnetic survey of this region has unravelled the magnetic pattern of the volcanics, notably two conspicuous calderas, since the young cover sediments are non-magnetic. The magnetic susceptibility of the volcanic rocks ranges 50 to 80 x 10-5 S.I., as oppossed to the nearly null values of the overlying sediments. The geological interpretation of the aeromagnetic survey is mostly based on the analytic signal of the total magnetic intensity, where two distinct sub-circular magnetic lineaments have been recognized and regarded as calderic structures. The eastern caldera, 30 km wide, is centered at 48º 52' S.L./ 68º 02' W.L., and the western caldera, 23 km wide, is centered at 48º 53' S.L. / 68º 29' W.L.. In addition, a number of smaller, high gradient magnetic anomalies have been identified and interpreted as intra- and extracaldera domes. In the eastern caldera, a number of domes follow an anular pattern of fractures regarded as the boundary of an older, outer caldera. A magnetic circular lineament located within the latter structure has been interpreted as a younger, inner caldera which presents a number of small domes in its central depression; additional domes are also located in between the two calderic structures. The western caldera is less complex since it comprises a single structure with intra-caldera domes. The total magnetic gradient (analytic signal) associated with the domes is one order of magnitude higher (0.1 to 0.2) than the mean value of the region (0.03). In addition to the anular fractures and domes, a

  10. Apropiación, distribución e intercambio: el ganado vacuno en el marco de las reducciones de abipones y mocoví (1743-1767

    Directory of Open Access Journals (Sweden)

    Carina Lucaioli

    2007-01-01

    Full Text Available En el presente artículo hemos tomado como recorte espacio-temporal las misiones jesuíticas fundadas para los grupos abipones y mocoví durante el siglo XVIII en el Chaco austral. Nuestro objetivo se orientó a analizar las múltiples relaciones entabladas con la sociedad hispanocriolla a partir de los distintos usos y formas de apropiación del ganado vacuno entre estos grupos. Las reducciones funcionaron como espacios complejos que condensaron variados intereses y conjugaron la interacción de distintos sujetos sociales. Asimismo, fueron lugares que permitieron a los grupos reducidos desplegar una serie de estrategias económicas y políticas para hacer frente a la sujeción colonial. Las actividades indígenas relacionadas con el manejo del ganado vacuno emergen como un exponente del tipo de respuestas elaboradas a tal fin. A partir de la lectura y análisis de fuentes documentales, identificamos y describimos tres tipos de stock ganadero: el ganado vacuno de las reducciones, los animales particulares en manos de individuos prestigiosos y las manadas destinadas al intercambio. Nos hemos propuesto analizar las formas de apropiación, distribución e intercambio, los sujetos e intereses intervinientes y el valor relativo del ganado vacuno en los diferentes contextos específicos

  11. An Analysis of Sulfur Content and Multiple Sulfur Isotope Fractionation of Tephra Deposits at Valles Caldera, New Mexico: Variations over the Course of Two Caldera-Forming Eruptions

    Science.gov (United States)

    Campbell, M. E.; Wing, B. A.; Stix, J.

    2010-12-01

    Caldera-forming eruptions leave behind a record of their tempo and mode in their associated tephra deposits. Interpreting this record requires monitors of the pre-eruptive state of the host magma chamber, potential triggers of the eruption, as well as a proxy for volatile evolution during the eruption. Because of the coexistence of multiple S-bearing species in a magma-gas system, S isotopes stand as a potentially powerful tool to interrogate the eruptive records of caldera-forming events. To date, few S isotopic profiles have been measured through the full eruptive cycle of an explosive silicic complex. Here, we present the first multiple S isotope dataset of the complete evolution of a large, silicic, caldera-forming system. High-silica rhyolite samples from Valles Caldera, New Mexico, were gathered from formations spanning two entire caldera cycles: the Lower Bandelier Tuff (LBT, which formed Toledo caldera at 1.6 Ma), the Cerro Toledo Rhyolite, the Upper Bandelier Tuff (UBT, which formed Valles caldera at 1.2 Ma), and the Valles Rhyolite. Whole-rock S was chemically extracted to Ag2S from samples collected from various units within these formations, and S isotopic compositions were subsequently evaluated by fluorination of the Ag2S and mass spectrometry of the resulting SF6. All S isotopic measurements are reported relative to the V-CDT scale. Concurrent analyses of in-house standard materials demonstrate 1 sigma uncertainties for the full analytical procedure on Δ34S, Δ33S, and Δ36S of better than 0.1‰, 0.01‰, and 0.1‰ respectively. Measured δ34S values range from 0.6 to 8.3‰, while Δ33S and Δ36S values vary from -0.06 to 0.02‰ and -0.5 to 0.3‰, respectively. The lowest δ34S values are from units occurring within or immediately before the earliest-erupted plinian Pumice Beds of the LBT and UBT (0.6 to 2.6‰), while the most elevated δ34S values are from the latest-erupted UBT plinian Pumice Bed unit that we sampled (7.0 and 8.3‰). δ34S

  12. Galileo's Last Fly-Bys of Io: NIMS Observations of Loki, Tupan, and Emakong Calderas

    Science.gov (United States)

    Lopes, Rosaly M. C.; Kamp, L. W.; Davies, A. G.; Smythe, W. D.; Carlson, R. W.; Doute, S.; McEwen, A.; Turtle, E. P.; Leader, F.; Mehlman, R.

    2002-01-01

    NIMS results from the 2001 Galileo fly-bys of Io will be presented, focusing on three calderas that may contain lava lakes. Preliminary results from the January 2002 Io fly-by will be presented. Additional information is contained in the original extended abstract.

  13. Identification of a Kulshan caldera correlative tephra in the Palouse loess of Washington State, northwest USA

    Science.gov (United States)

    King, Georgina E.; Pearce, Nicholas J. G.; Roberts, Helen M.; Smith, Victoria C.; Westgate, John A.; Gaylord, David R.; Sweeney, Mark R.

    2016-09-01

    The Kulshan caldera formed at ∼1.15 Ma on the present-day site of Mt. Baker, Washington State, northwest USA and erupted a compositionally zoned (dacite-rhyolite) magma and a correlative eruptive, the Lake Tapps tephra. This tephra has previously been described, but only from the Puget Lowland of NW Washington. Here an occurrence of a Kulshan caldera correlative tephra is described from the Quaternary Palouse loess at the Washtucna site (WA-3). Site WA-3 is located in east-central Washington, ∼340 km southeast of the Kulshan caldera and ∼300 km east-southeast of the Lake Tapps occurrence in the Puget Lowland. Major- and trace element chemistry and location of the deposit at Washtucna within reversed polarity sediments indicates that it is not correlative with the Mesa Falls, Rockland, Bishop Ash, Lava Creek B or Huckleberry Ridge tephras. Instead the Washtucna deposit is related to the Lake Tapps tephra by fractional crystallisation, but is chemically distinct, a consequence of its eruption from a compositionally zoned magma chamber. The correlation of the Washtucna occurrence to the Kulshan caldera-forming eruption indicates that it had an eruptive volume exceeding 100 km3, and that its tephra could provide a valuable early-Pleistocene chronostratigraphic marker in the Pacific Northwest.

  14. Monitoring super-volcanoes: geophysical and geochemical signals at Yellowstone and other large caldera systems.

    Science.gov (United States)

    Lowenstern, Jacob B; Smith, Robert B; Hill, David P

    2006-08-15

    Earth's largest calderas form as the ground collapses during immense volcanic eruptions, when hundreds to thousands of cubic kilometres of magma are explosively withdrawn from the Earth's crust over a period of days to weeks. Continuing long after such great eruptions, the resulting calderas often exhibit pronounced unrest, with frequent earthquakes, alternating uplift and subsidence of the ground, and considerable heat and mass flux. Because many active and extinct calderas show evidence for repetition of large eruptions, such systems demand detailed scientific study and monitoring. Two calderas in North America, Yellowstone (Wyoming) and Long Valley (California), are in areas of youthful tectonic complexity. Scientists strive to understand the signals generated when tectonic, volcanic and hydrothermal (hot ground water) processes intersect. One obstacle to accurate forecasting of large volcanic events is humanity's lack of familiarity with the signals leading up to the largest class of volcanic eruptions. Accordingly, it may be difficult to recognize the difference between smaller and larger eruptions. To prepare ourselves and society, scientists must scrutinize a spectrum of volcanic signals and assess the many factors contributing to unrest and toward diverse modes of eruption.

  15. Temporal models for the episodic volcanism of Campi Flegrei caldera (Italy) with uncertainty quantification

    Science.gov (United States)

    Bevilacqua, Andrea; Flandoli, Franco; Neri, Augusto; Isaia, Roberto; Vitale, Stefano

    2016-11-01

    After the large-scale event of Neapolitan Yellow Tuff ( 15 ka B.P.), intense and mostly explosive volcanism has occurred within and along the boundaries of the Campi Flegrei caldera (Italy). Eruptions occurred closely spaced in time, over periods from a few centuries to a few millennia, and were alternated with periods of quiescence lasting up to several millennia. Often events also occurred closely in space, thus generating a cluster of events. This study had two main objectives: (1) to describe the uncertainty in the geologic record by using a quantitative model and (2) to develop, based on the uncertainty assessment, a long-term subdomain specific temporal probability model that describes the temporal and spatial eruptive behavior of the caldera. In particular, the study adopts a space-time doubly stochastic nonhomogeneous Poisson-type model with a local self-excitation feature able to generate clustering of events which are consistent with the reconstructed record of Campi Flegrei. Results allow the evaluation of similarities and differences between the three epochs of activity as well as to derive eruptive base rate of the caldera and its capacity to generate clusters of events. The temporal probability model is also used to investigate the effect of the most recent eruption of Monte Nuovo (A.D. 1538) in a possible reactivation of the caldera and to estimate the time to the next eruption under different volcanological and modeling assumptions.

  16. A three-dimensional gravity model of the geologic structure of Long Valley caldera

    Energy Technology Data Exchange (ETDEWEB)

    Carle, S.F.; Goldstein, N.E.

    1987-03-01

    Several attempts to define and interpret this anomaly have been made in the past using 2-D and 3-D models. None of the previous interpretations have yielded definitive results, but in fairness, the interpretation here has benefited from a larger gravity data base and more subsurface control than available to previous workers. All published 3-D models simplistically assumed constant density of fill. All 2-D models suffered from the inherent three-dimensionality of the complicated density structure of Long Valley caldera. In addition, previous interpreters have lacked access to geological data, such as well lithologies and density logs, seismic refraction interpretations, suface geology, and structural geology interpretations. The purpose of this study is to use all available gravity data and geological information to constrain a multi-unit, 3-D density model based on the geology of Long Valley caldera and its vicinity. Insights on the geologic structure of the caldera fill can help other geophysical interpretations in determining near-surface effects so that deeper structure may be resolved. With adequate control on the structure of the caldera fill, we are able to examine the gravity data for the presence of deeper density anomalies in the crust. 20 refs., 7 figs.

  17. Topographic modelling of caldera analogues using Structure from Motion - Multiview stereo-photogrammetry

    Science.gov (United States)

    Ulusoy, İnan; Aydın, Eda; Evren Çubukçu, H.

    2016-04-01

    Analogue caldera models have long been used in volcanology to investigate structural evolution of volcanoes during tumescence and collapse periods. Influence of tectonic forces on volcanic features are also in the scope of those experiments. As well as interior modelling of the caldera experiments, topographic modelling is essential for digital monitoring and quantification purposes. Topographic modelling of those sandbox models is possible using laser scanning techniques. Particle tracking using still images is another way to demonstrate and quantify the structure and movement during the experiment. The quantum leap in the digital photography and computation tools and ease of access to both, provides the use of a new modelling technique in various scales and applications in Geology. Although the roots are older, Structure from Motion - Multiview stereo-photogrammetry (SfM-MVS) is a relatively new technique for surface modelling via several high resolution photographs. We have used SfM-MVS to digitally model the elevation of the tumescence and collapse cycles in analogue caldera experiments. Several sandbox experiments have been modelled using SfM-MVS technique stage by stage during tumescence and collapse periods. It has been possible to evaluate the structural evolution of the collapse models. Additionally, using particle tracking via still images acquired during the experiments, we have modelled the superficial evolution of the caldera structure. SfM-MVS is an effective low budget method for modelling in decimetric scale down to millimetre/micrometre precision.

  18. Steady subsidence of a repeatedly erupting caldera through InSAR observations: Aso, Japan

    Science.gov (United States)

    Nobile, Adriano; Acocella, Valerio; Ruch, Joel; Aoki, Yosuke; Borgstrom, Sven; Siniscalchi, Valeria; Geshi, Nobuo

    2016-04-01

    The relation between unrest and eruption at calderas is still poorly understood. Aso caldera, Japan, shows minor episodic eruptions, mainly phreatic, associated with steady subsidence. We analyse the recent deformation of Aso using SAR images from 1993 to 2011 and compare this with the eruptive activity. Although the dataset suffers from limitations (e.g., atmospheric effects, coherence loss, low signal to noise ratio), we observe a steady subsidence signal from 1996 to 1998, that suggests an overall contraction of a magmatic source below the caldera centre, from 4.5 to 7 km depth. Because of the similar volumes of the contracting source and erupted material, we propose that the contraction may have been induced by the release of the magmatic fluids feeding the eruptions. If confirmed by further data, this hypothesis suggests that degassing processes play a crucial role in triggering minor eruptions within open conduit calderas, as at Aso. These features underline the importance of defining any eruptive potential also from deflating magmatic systems with open conduit.

  19. Quantifying volcanic hazard at Campi Flegrei caldera (Italy) with uncertainty assessment: 1. Vent opening maps

    Science.gov (United States)

    Bevilacqua, Andrea; Isaia, Roberto; Neri, Augusto; Vitale, Stefano; Aspinall, Willy P.; Bisson, Marina; Flandoli, Franco; Baxter, Peter J.; Bertagnini, Antonella; Esposti Ongaro, Tomaso; Iannuzzi, Enrico; Pistolesi, Marco; Rosi, Mauro

    2015-04-01

    Campi Flegrei is an active volcanic area situated in the Campanian Plain (Italy) and dominated by a resurgent caldera. The great majority of past eruptions have been explosive, variable in magnitude, intensity, and in their vent locations. In this hazard assessment study we present a probabilistic analysis using a variety of volcanological data sets to map the background spatial probability of vent opening conditional on the occurrence of an event in the foreseeable future. The analysis focuses on the reconstruction of the location of past eruptive vents in the last 15 ka, including the distribution of faults and surface fractures as being representative of areas of crustal weakness. One of our key objectives was to incorporate some of the main sources of epistemic uncertainty about the volcanic system through a structured expert elicitation, thereby quantifying uncertainties for certain important model parameters and allowing outcomes from different expert weighting models to be evaluated. Results indicate that past vent locations are the most informative factors governing the probabilities of vent opening, followed by the locations of faults and then fractures. Our vent opening probability maps highlight the presence of a sizeable region in the central eastern part of the caldera where the likelihood of new vent opening per kilometer squared is about 6 times higher than the baseline value for the whole caldera. While these probability values have substantial uncertainties associated with them, our findings provide a rational basis for hazard mapping of the next eruption at Campi Flegrei caldera.

  20. Monitoring super-volcanoes: Geophysical and geochemical signals at Yellowstone and other large caldera systems

    Science.gov (United States)

    Lowenstern, J. B.; Smith, R.B.; Hill, D.P.

    2006-01-01

    Earth's largest calderas form as the ground collapses during immense volcanic eruptions, when hundreds to thousands of cubic kilometres of magma are explosively withdrawn from the Earth's crust over a period of days to weeks. Continuing long after such great eruptions, the resulting calderas often exhibit pronounced unrest, with frequent earthquakes, alternating uplift and subsidence of the ground, and considerable heat and mass flux. Because many active and extinct calderas show evidence for repetition of large eruptions, such systems demand detailed scientific study and monitoring. Two calderas in North America, Yellowstone (Wyoming) and Long Valley (California), are in areas of youthful tectonic complexity. Scientists strive to understand the signals generated when tectonic, volcanic and hydrothermal (hot ground water) processes intersect. One obstacle to accurate forecasting of large volcanic events is humanity's lack of familiarity with the signals leading up to the largest class of volcanic eruptions. Accordingly, it may be difficult to recognize the difference between smaller and larger eruptions. To prepare ourselves and society, scientists must scrutinize a spectrum of volcanic signals and assess the many factors contributing to unrest and toward diverse modes of eruption. ?? 2006 The Royal Society.

  1. Sericite from the Silverton caldera, Colorado: correlation among structure, composition, origin, and particle thickness.

    Science.gov (United States)

    Eberl, D.D.; Srodon, J.; Lee, M.; Nadeau, P.H.; Northrop, H.R.

    1987-01-01

    The mineralogy and the origin of a suite of almost pure sericites, collected from fractures in hydrothermally altered volcanic rocks in the vicinity of the Silverton caldera in the western San Juan Mountains of Colorado, USA, are analysed.-J.A.Z.

  2. The Caetano Caldera, Nevada: 5 km Thickness of Intracaldera Rhyolite Ignimbrite and Co-Magmatic Batholith

    Science.gov (United States)

    John, D. A.; Henry, C. D.; Colgan, J. P.

    2008-12-01

    The Caetano caldera in northern Nevada is cut by Miocene extensional faults that extraordinarily expose a complete, thick (>4 km) intracaldera rhyolite ignimbrite (Caetano Tuff) and underlying cogenetic granitic plutons in tilted blocks reaching to >5 km of paleodepth. The caldera contains (1) a 1-km-thick upper unit of Caetano Tuff composed of multiple, thin cooling units and interbedded sedimentary rocks, (2) a >3.5- km-thick lower compound cooling unit of Caetano Tuff, and (3) 5 shallowly emplaced (locally 50 km2. Ten sanidine 40Ar/39Ar ages from the stratigraphically lowest Caetano Tuff through the youngest shallow pluton are indistinguishable at 33.8 Ma, indicating that eruption of >1000 km3 of rhyolite tuff, caldera collapse, magma resurgence, and pluton emplacement occurred in residual magma from the reservoir that fed the later parts of the eruption. Field, geochemical, and geochronologic data prove a shallow batholith-scale magma reservoir erupted to form the Caetano caldera and fed cogenetic granite plutons. Additional geochemical and geochronologic (SHRIMP) studies are underway to constrain magma sources, duration of assembly, and compositional zoning of the Caetano magma reservoir.

  3. A short review of our current understanding of the development of ring faults during collapse caldera formation

    Directory of Open Access Journals (Sweden)

    Adelina eGeyer

    2014-09-01

    Full Text Available The term collapse caldera refers to those volcanic depressions resulting from the sinking of the chamber roof due to the rapid withdrawal of magma during the course of an eruption. During the last three decades, collapse caldera dynamics has been the focus of attention of numerous, theoretical, numerical and experimental studies. Nonetheless, even if there is a tendency to go for a general and comprehensive caldera dynamics model, some key aspects remain unclear, controversial or completely unsolved. This is the case of ring fault nucleation points and propagation and dip direction. Since direct information on calderas’ deeper structure comes mainly from partially eroded calderas or few witnessed collapses, ring faults layout at depth remains still uncertain. This has generated a strong debate over the detailed internal fault and fracture configuration of a caldera collapse and, in more detail, how ring faults initiate and propagate. We offer here a very short description of the main results obtained by those analogue and theoretical/mathematical models applied to the study of collapse caldera formation. We place special attention on those observations related to the nucleation and propagation of the collapse-controlling ring faults. This summary is relevant to understand the current state-of-the-art of this topic and it should be taken under consideration in future works dealing with collapse caldera dynamics.

  4. Plio-pleistocene volcano-tectonic evolution of la Reforma Caldera, Baja California, Mexico

    Science.gov (United States)

    Demant, Alain; Ortlieb, Luc

    1981-01-01

    La Reforma volcanic complex, in east-central Baja California, shows a characteristic caldera structure, 10 km in diameter. The first eruptive stage, during the Pliocene, was manifested by ash and pumice falls and by subaqueous pumitic flows. In a second stage basic flows were deposited in a near-shore environment (subaerial and pillow lavas). During the early Pleistocene a large ignimbritic eruption, producing mainly pantelleritic tuffs, immediately predated the formation of the caldera itself. Afterwards, along marginal fractures of the caldera, some rhyolitic domes and flows partially covered the thick ignimbritic sheet. A block of Miocene substratum, in the center of the caldera, has been uplifted, nearly 1 km, by "resurgent doming". Small outcrops of diorite might constitute the top of coarse-grained crystallized magmatic bodies, and thus support the "resurgent doming" interpretation. A few basaltic cones were finally built on the flanks of the caldera complex; the latter are not related to the caldera history but to the extension tectonics of the Gulf of California which are also responsible for the Tortuga Island and the Holocene Tres Virgenes tholeiitic cones. South of la Reforma are found the highest (+300 m) Pleistocene marine deposits of the Gulf coast of Baja California. The uplift of this area is due in part to the positive epeirogenic movements of the whole peninsular crustal block, and also to the late doming of the caldera. On the coastal (eastern) flank of La Reforma complex up to seven stepped wave-cut terraces have been preserved, the highest reaching more than +150 m and the lowest ones +25 m. Lateral correlations of the marine terraces along the whole Gulf of California suggest that this volcano-tectonic uplift, that is still active, is of the order of 240 mm/10 3 y. The set of terraces is interpreted to be Middle (700-125 × 10 3y) to Upper (125-80 × 10 3y) Pleistocene, and is tentatively correlated with the paleoclimatic chronology of deep

  5. Evidence from cosmic-ray exposure dating based on 36Cl for the pre-Minoan caldera on Santorini, Greece

    Science.gov (United States)

    Athanassas, Constantin; Bourlès, Didier; Braucher, Regis; Druitt, Tim; Nomikou, Paraskevi; Léanni, Laetitia

    2016-04-01

    The physiography of Santorini prior to the Minoan (Late Bronze Age) eruption (17th century BCE) is of great archaeological interest, given the importance of Santorini as a commercial centre and port in the Minoan empire. However, the paleogeography of the pre-Minoan caldera has been a point of controversy: Heiken and McCoy (1984) advocated the existence, in the southern part of the present-day caldera, of a pre-existing caldera formed during the 172 ka Lower Pumice eruption, whereas Druitt and Francaviglia (1992), based on the presence of in situ plinian pumice from the Minoan eruption adhering to the modern cliff, conceived the pre-Minoan (22 ka) caldera as having occupied much of the northern basin of the present-day caldera. With the goal of settling the debate we performed cosmic ray exposure dating employing in situ-produced cosmogenic 36Cl to date different generations of caldera cliffs at Santorini, and hence to identify those cliffs predating the Minoan eruption. Our methodology involved the determination of the in situ-produced cosmogenic 36Cl in basaltic and andesitic rocks cropping out in the cliffs. The samples returned 36Cl CRE ages consistent with previously published field mapping of cliff populations based on geomorphological and stratigraphic arguments (Druitt and Francaviglia 1992), suggesting that much of the present cliff line of northern Santorini predated the Minoan eruption, or was superficially modified by landslips and rockfalls during that eruption. The 36Cl CRE ages enable us to better define the paleogeography of the pre-Minoan caldera. References [1] Druitt, T. H. and Francaviglia, V.1992. Caldera formation on Santorini and the physiography of the islands in the Late Bronze Age. Bulletin of Volcanology 54, 484-493. [2] Heiken G and McCoy F (1984) Caldera development during the Minoan eruption, Thira, Cyclades, Greece. Journal of Geophysical Research: 89 (B10), 8841-8862.

  6. Nursing work in Spain and Cuba: an exchange experience. Labor de Enfermería en España y Cuba: Un intercambio de experiencia.

    Directory of Open Access Journals (Sweden)

    Héctor Cabrera Rodríguez

    2005-12-01

    Full Text Available A descriptive study was performed in 5 students from Granada that were in their working practices in Cienfuegos; mainly in policlinics, maternity homes, family doctors offices etc. as part of the agreement between Granada university and Cienfuegos Medicine School. Our experience has been very positive both, in the professional and personal field. The interchange between paramedical staff of both countries developed solidarity and humanism. This exchange allows knowing the high degree of transmissible diseases due to immigrants' arrival, lack of epidemiological control and waste of material and money. We can assure that the main achievement of this experience was encounter of these visitors with other Spanish students and teachers in the University of Granada. This activity was different from the traditional university lecture. Se realizó un estudio descriptivo con 5 estudiantes de Granada que durante el mes de agosto del 2004 realizaron una pasantía por los diferentes centros de salud de nuestra provincia, enfatizando en los consultorios médicos, hogares maternos, Policlínico Principal de Urgencias, entre otros, como fruto del convenio efectuado entre la Universidad de Granada y la Facultad de Ciencias Médicas de Cienfuegos. Nuestra experiencia fue muy positiva tanto en el plano profesional como en el personal, predominó el intercambio entre el personal paramédico de ambos países; dejando frutos como la solidaridad y el humanismo. Este intercambio permitió conocer que existe alto grado de enfermedades transmisibles debido a la entrada de inmigrantes, deficiente control epidemiológico, así como derroche de material y dinero por su sistema de salud. Podemos señalar que la expresión máxima que manifestó esta experiencia de intercambio entre nuestras instituciones y las motivaciones que sobre la misma se abren al futuro, fue el encuentro desarrollado entre las estudiantes que visitaron Cuba con otros estudiantes y profesores espa

  7. Descripción y análisis de las normas de metadatos para intercambio de información audiovisual de la Digital Production Partnership (dpp

    Directory of Open Access Journals (Sweden)

    Jorge Caldera Serrano

    2015-11-01

    Full Text Available La entidad británica Digital Production Partnership (dpp es una asociación de creciente creación pero que cuenta con socios indudablemente solventes y potentes en el ámbito de la información audiovisual en los medios televisivos. Entre las acciones de la DPP se encuentra la redacción de una directiva de metadatos asociados a la información audiovisual con el fin de que sea un modelo estándar para el intercambio de recursos audiovisuales. Este trabajo tiene como objetivo el mostrar dicha directiva así como las principales ventajas y características de dicha acción y como puede servir de base a la implementación de bases de datos documentales para cadenas de televisión.

  8. Digital Geologic Map of Mount Mazama and Crater Lake Caldera, Oregon

    Science.gov (United States)

    Bacon, C. R.; Ramsey, D. W.

    2002-12-01

    Crater Lake caldera formed ~7700 cal yr B.P. by the eruption of 50 km3 of mainly rhyodacitic magma and the resulting collapse of Mount Mazama. A new 1:24,000-scale digital geologic map compiled in ArcInfo depicts the geology of this volcanic center, peripheral volcanoes, the caldera walls and floor, and superjacent pyroclastic, talus, and glacial deposits. The geology of the caldera walls was mapped in the field on photographs taken from the lake (see accompanying abstract and poster, "Geologic panoramas of the walls of Crater Lake caldera,Oregon"); the geology of the flanks of Mount Mazama and the surrounding area was mapped on aerial photographs; and features of the caldera floor were mapped on a multibeam echo-sounding bathymetric map (Gardner et al., 2001; Bacon et al., 2002). Volcanic map units are defined on the basis of chemical composition and petrographic characteristics. Map unit colors were chosen to indicate the compositions of volcanic rocks, cooler colors for mafic units and warmer colors for silicic units. Map unit color intensity indicates age, with more intense coloring for younger units. Ages of many units have been determined by K-Ar and 40Ar/39Ar dating by M.A. Lanphere. Several undated units have been correlated using paleomagnetic secular variation measurements by D.E. Champion. Crystallization facies of some of the larger lava flows are mapped separately (e.g., vitrophyre, felsite, carapace), as are breccia and lava facies of submerged postcaldera volcanoes. Also shown on the caldera floor are landslide (debris avalanche) and sediment gravity-flow deposits. A major north-south normal fault system traverses the map area west of the caldera and displaces dated late Pleistocene lava flows, allowing determination of a long-term slip rate of ~0.3 mm/yr (Bacon et al., 1999). Faults bounding large downdropped blocks of the south caldera wall are also shown. Where practical, lava flow margins are represented as intra-unit contacts. A number of small

  9. Geothermal hydrology of Valles Caldera and the southwestern Jemez Mountains, New Mexico

    Science.gov (United States)

    Trainer, Frank W.; Rogers, Robert J.; Sorey, M.L.

    2000-01-01

    The Jemez Mountains in north-central New Mexico are volcanic in origin and have a large central caldera known as Valles Caldera. The mountains contain the Valles geothermal system, which was investigated during 1970-82 as a source of geothermal energy. This report describes the geothermal hydrology of the Jemez Mountains and presents results of an earlier 1972-75 U.S. Geological Survey study of the area in light of more recent information. Several distinct types of thermal and nonthermal ground water are recognized in the Jemez Mountains. Two types of near-surface thermal water are in the caldera: thermal meteoric water and acid sulfate water. The principal reservoir of geothermal fluids is at depth under the central and western parts of the caldera. Nonthermal ground water in Valles Caldera occurs in diverse perched aquifers and deeper valley-fill aquifers. The geothermal reservoir is recharged by meteorically derived water that moves downward from the aquifers in the caldera fill to depths of 6,500 feet or more and at temperatures reaching about 330 degrees Celsius. The heated geothermal water rises convectively to depths of 2,000 feet or less and mixes with other ground water as it flows away from the geothermal reservoir. A vapor zone containing steam, carbon dioxide, and other gases exists above parts of the liquid-dominated geothermal zone. Two subsystems are generally recognized within the larger geothermal system: the Redondo Creek subsystem and the Sulphur Creek subsystem. The permeability in the Redondo Creek subsystem is controlled by stratigraphy and fault-related structures. Most of the permeability is in the high-angle, normal faults and associated fractures that form the Redondo Creek Graben. Faults and related fractures control the flow of thermal fluids in the subsystem, which is bounded by high-angle faults. The Redondo Creek subsystem has been more extensively studied than other parts of the system. The Sulphur Springs subsystem is not as well

  10. Intercambio gaseoso en el síndrome de dificultad respiratoria aguda Gas exchange in acute respiratory distress syndrome

    Directory of Open Access Journals (Sweden)

    G. A. Raimondi

    2003-04-01

    Full Text Available El síndrome de dificultad respiratoria aguda (ARDS se caracteriza por presentar alteraciones severas del intercambio gaseoso (IG causadas por «shunt» e importante irregularidad de la ventilación perfusión (V A/Q. Esto es consecuencia del edema intersticial y el colapso y ocupación alveolar. Además de la fracción inspirada de oxígeno y la evolución de la patología pulmonar, hay distintas variables que son capaces de alterar la presión parcial de oxígeno arterial (PaO2. Es así que los cambios del volumen minuto circulatorio, la concentración de hemoglobina, el consumo de oxígeno o la alcalosis pueden modificar la PaO2 a través de su influencia en la PO2 de sangre venosa mixta. A pesar de la influencia de estas diferentes variables, la anormalidad del IG se ha podido analizar adecuadamente por medio de la técnica de eliminación de múltiples gases inertes (MIGET. Asimismo, se han descripto diversas estrategias ventilatorias (presión positiva de fin de espiración, relaciones inspiratorias-espiratorias invertidas, volúmenes corrientes elevados, etc. que producen mejoría del IG principalmente a través del aumento de la presión media en la vía aérea al reclutar áreas pulmonares previamente colapsadas. También el cambio de decúbito a posición ventral, por modificaciones en la distribución de presión pleural regional, disminuye el colapso alveolar con mejoría de la PaO2. Asimismo hay distintas intervenciones farmacológicas capaces de mejorar el IG tales como la administración de óxido nítrico (ON o de prostaglandinas (PGI2 o PGE1 por vía inhalatoria. Estas producen vasodilatación de las áreas bien ventiladas aumentando el flujo cardíaco a ese nivel y disminuyendo relativamente el flujo por las áreas de «shunt». La almitrina endovenosa, droga vasoconstrictora pulmonar, mejora el IG al aumentar la vasoconstricción hipóxica. Se ha demostrado efecto aditivo de la almitrina con la inhalación de ON. A pesar del

  11. Confianza, influencia política e intercambio de recursos en arenas decisorias regionales Trust, Political Influence, and Exchange of Resources in Regional Decision-Making Arenas

    Directory of Open Access Journals (Sweden)

    RAMIRO BERARDO

    2012-01-01

    Full Text Available La literatura politológica destaca la importancia de la confianza en la emergencia de procesos sociopolíticos cooperativos, pero en la politología latinoamericana no existen aún exploraciones empíricas de la relación entre confianza y otras variables que también afectan la cooperación en arenas decisorias regionales. Este artículo contribuye a solucionar esta limitación examinando la relación entre confianza, intercambio de recursos y reconocimiento de influencia política, entre actores de tres regiones subnacionales de la Argentina. Los resultados sugieren que tanto el reconocimiento de influencia como el intercambio de recursos se correlacionan de manera muy significativa con las relaciones de confianza que existe entre los actores. Esta relación tiene implicancias sobre procesos de gobernanza a nivel regional, que discutimos en detalle.Research in political science has identified trust as an important variable for the emergence of cooperative social-political processes, but there are no empirical explorations in Latin American political science yet of the relationship between trust and other variables that are thought to affect cooperation in regional decision-making arenas. This article contributes to addressing this limitation by examining the relationship between trust, exchange of resources, and perception of political influence among actors in 3 sub-national regions in Argentina. Results suggest that these variables are significantly related to each other, which has implications for our understanding of how regional governance processes work. We discuss these implications in detail.

  12. REFRIGERAÇÃO UTILIZANDO PASTILHAS DE EFEITO PELTIER

    OpenAIRE

    Antonio Luiz P. S. Campos; Aécio Vinícius Amorim Farias; Jainne Daniele F. S. Fernandes; Alailson de Freitas Braz; Machado, Ludmila Sayonara S. X.; Edfranklin de Souza Pimentel

    2010-01-01

    Pastilhas de Peltier são dispositivos baseados no efeito Peltier e são aplicadas para produzir efeito refrigerador ou aquecedor. Este trabalho aborda conceitos envolvidos na fabricação e funcionamento desses dispositivos tais como: histórico do efeito Peltier e desenvolvimento de placas de efeito Peltier. É feito um estudo de eficiência da refrigeração de água utilizando uma placa de efeito Peltier existente no Campus Natal – Zona Norte. Para isso, é implementada uma estrutura de refrigeração...

  13. Un administrador de procesamiento distribuido utilizando Windows Sockets

    OpenAIRE

    Naiouf, Marcelo; De Giusti, Armando Eduardo; Chaer, R.; Fonseca, A.

    1996-01-01

    Se presenta un administrador de procesamiento distribuido utilizando Windows Sockets, que permite la comunicación y distribución de tareas entre máquinas de una red, para la ejecución de algoritmos paralelos. La plataforma del sistema es una red en al cual la única restricción es que las estaciones estén ejecutando Windows. El soporte de comunicaciones se realiza a través de una librería que permite utilizar canales de comunicación sobre la red administrando la señalización mediante el env...

  14. Understanding the link between circumferential dikes and eruptive fissures around calderas based on numerical and analog models

    Science.gov (United States)

    Corbi, Fabio; Rivalta, Eleonora; Pinel, Virginie; Maccaferri, Francesco; Acocella, Valerio

    2016-06-01

    Active calderas are seldom associated with circumferential eruptive fissures, but eroded magmatic complexes reveal widespread circumferential dikes. This suggests that, while the conditions to emplace circumferential dikes are easily met, mechanisms must prevent them from reaching the surface. We explain this discrepancy with experiments of air injection into gelatin shaped as a volcano with caldera. Analog dikes show variable deflection, depending on the competition between overpressure, Pe, and topographic unloading, Pl; when Pl/Pe = 4.8-5.3, the dikes propagate orthogonal to the least compressive stress. Due to the unloading, they become circumferential and stall below the caldera rim; buoyancy is fundamental for the further rise and circumferential fissure development. Numerical models quantitatively constrain the stress orientation within the gelatin, explaining the observed circumferential dikes. Our results explain how dikes propagate below the rim of felsic and mafic calderas, but only in the latter they are prone to feed circumferential fissures.

  15. How medium-size resurgent calderas work: the case of Pantelleria, Ischia and the unrest Campi Flegrei structures

    Science.gov (United States)

    Orsi, Giovanni; Civetta, Lucia; Arienzo, Ilenia; Carandente, Antonio; D'Antonio, Massimo; de Vita, Sandro; di Renzo, Valeria; di Vito, Mauro; Marotta, Enrica; Belviso, Pasquale

    2010-05-01

    Assessment of time and space relationships among magmatism, volcanism, and resurgence of medium-size calderas is a necessary tool to formulate a general model for their dynamics which also permits to forecast their evolution. To define a general hypothesis for the Campi Flegrei caldera, in a persistent state of unrest, the Ischia and Pantelleria medium-size resurgent structures, in variable stages of evolution, have been investigated. In particular some parameters such as the structural and volcanological evolution, with emphasis on resurgence dynamics and coeval volcanism, and the evolution, present state and role of the magmatic system in resurgence, have been defined. For the Campi Flegrei caldera, the data collected during unrest episodes have also been taken into account. This innovative approach adds a time-perspective on how resurgent calderas behave. The proposed general hypothesis will help in long- and short-term volcanic hazards assessment and will support Civil Defence Authorities in elaborating actions devoted to volcanic risk reduction.

  16. Evolution of the Creede Caldera and its relation to mineralization in the Creede mining district, Colorado

    Science.gov (United States)

    Barton, Paul B.; Rye, Robert O.; Bethke, Philip M.

    2000-01-01

    At 25 Ma a major epithermal silver and base metal deposit formed in rhyolitic welded tuff near Creede, Colorado. Nearly 24000 metric tons of silver, appreciable lead, and small amounts of zinc, copper, and gold, have been produced from large, crustified veins under Bachelor and Bulldog Mountains north and northwest of Creede. Prior geologic, hydrologic, and stable-isotope studies showed that ore deposition was associated with the mixing and boiling of waters from diverse sources and suggester that a critical part of the ore-forming fluid may have originated within the ancient lake and sediments of the lacustrine Creede Formation that filled the Creede caldera. Two drill holes that sampled the heretofore hidden lower half of the Creede Formation are the focus of this book. The Creede caldera formed at 26.9 Ma within a high constructional plateau of silicic ashflows that covered and were sporadically interlayed with, intermediate lavas and lahars from large stratovolcanoes. The Creede caldera lake had an inflow evaporation balance that did not permit rapid filling to create a brim-full deep lake. Thus salts were evaporatively concentrated; but, with the exception of possible gypsum, no evaporite minerals preserved. Cool springs deposited travertine as mounds and contributed to limestone interlaminations within the sediment. The lake bottom was anoxic, and bacterial reduction of sulfate led to extreme sulfur isotopic fractionation in diagenetic pyrite. The caldera gradually resurged, converting the initial equant lake into an arcuate moat. Resurgent doming, alluvial fans, lacustrine sediments, ashfalls, and lava domes displaced water, lifted the lake so that it overlapped what later became the southern edge of the mineralized are, and eventually filled the basin. At 25.1 Ma an unseen pluton intruded beneath the northen part of the Creede district and created a convecting olume that drew in brine from the Creede caldera fill, meteotic water from highlands to the north

  17. Postcaldera volcanism and hydrothermal activity revealed by autonomous underwater vehicle surveys in Myojin Knoll caldera, Izu-Ogasawara arc

    Science.gov (United States)

    Honsho, Chie; Ura, Tamaki; Kim, Kangsoo; Asada, Akira

    2016-06-01

    Myojin Knoll caldera, one of the submarine silicic calderas lying on the volcanic front of the northern Izu-Ogasawara arc, has attracted increasing attention since the discovery of a large hydrothermal field called the Sunrise deposit. Although numerous submersible surveys have been conducted in Myojin Knoll caldera, they have not sufficiently explored areas to produce a complete picture of the caldera and understand the origin of the Sunrise deposit. We conducted comprehensive deep-sea surveys using an autonomous underwater vehicle and obtained high-resolution bathymetric and magnetic data and sonar images from ~70% of the caldera. The detailed bathymetric map revealed that faulting and magma eruptions, possibly associated with an inflation-deflation cycle of the magma reservoir during postcaldera volcanism, had generally occurred in the caldera wall. The main dome of the central cone was covered with lava flows and exhibits exogenous growth, which is unusual for rhyolitic domes. The magnetization distribution in the central cone indicates preferential magma intrusion along a NW-SE direction. It is presumed that magma migrated along this direction and formed a rhyolite dome at the foot of the southeastern caldera wall, where the Sunrise deposit occurs. The Sunrise deposit is composed mainly of three ridges extending in slope directions and covers ~400 × ~400 m. Magnetization reduction in the deposit area is small, indicating that the alteration zone beneath the Sunrise deposit is slanting rather than vertical. It is presumed that several slanting and near-vertical volcanic vents serve as pathways of hydrothermal fluid in Myojin Knoll caldera.

  18. Pyroclastic deposits as a guide for reconstructing the multi-stage evolution of the Somma-Vesuvius Caldera

    Science.gov (United States)

    Cioni, Raffaello; Santacroce, Roberto; Sbrana, Alessandro

    The evolution of the Somma-Vesuvius caldera has been reconstructed based on geomorphic observations, detailed stratigraphic studies, and the distribution and facies variations of pyroclastic and epiclastic deposits produced by the past 20,000years of volcanic activity. The present caldera is a multicyclic, nested structure related to the emptying of large, shallow reservoirs during Plinian eruptions. The caldera cuts a stratovolcano whose original summit was at 1600-1900m elevation, approximately 500m north of the present crater. Four caldera-forming events have been recognized, each occurring during major Plinian eruptions (18,300 BP "Pomici di Base", 8000 BP "Mercato Pumice", 3400 BP "Avellino Pumice" and AD 79 "Pompeii Pumice"). The timing of each caldera collapse is defined by peculiar "collapse-marking" deposits, characterized by large amounts of lithic clasts from the outer margins of the magma chamber and its apophysis as well as from the shallow volcanic and sedimentary units. In proximal sites the deposits consist of coarse breccias resulting from emplacement of either dense pyroclastic flows (Pomici di Base and Pompeii eruptions) or fall layers (Avellino eruption). During each caldera collapse, the destabilization of the shallow magmatic system induced decompression of hydrothermal-magmatic and hydrothermal fluids hosted in the wall rocks. This process, and the magma-ground water interaction triggered by the fracturing of the thick Mesozoic carbonate basement hosting the aquifer system, strongly enhanced the explosivity of the eruptions.

  19. The Campi Flegrei caldera (Italy): Formation and evolution in interplay with sea-level variations since the Campanian Ignimbrite eruption at 39 ka

    Science.gov (United States)

    Steinmann, Lena; Spiess, Volkhard; Sacchi, Marco

    2016-11-01

    To date, the origin of the Campi Flegrei caldera is still under debate and may be related to (1) a single caldera collapse associated with the Neapolitan Yellow Tuff (NYT) eruption, (2) two subsequent caldera collapses associated with the NYT and the preceding Campanian Ignimbrite (CI) eruptions forming a nested-caldera complex, or (3) not related to a caldera collapse after all. Here, we study the submerged portion of the caldera, which has favored a marine depositional setting and, thus, represents an ideal location for the reconstruction of its formation history, utilizing multichannel seismic data. Volcanic deposits and edifices were seismically distinguished from sedimentary successions, and the stratigraphy could be refined and extended back to the Campanian Ignimbrite eruption at 39 ka. High-resolution multichannel reflection seismic data revealed the existence of a nested-caldera complex formed during the CI eruption at 39 ka and the more recent NYT eruption at 15 ka. A ring-fault bounding an inner caldera collapse structure was clearly imaged. It appears that this inner ring-fault was initially activated during the CI caldera collapse and later reactivated during the NYT caldera collapse with different amounts of subsidence. The NYT caldera probably formed during an asymmetrical collapse with a maximum subsidence of 75 m in the offshore portion. The vertical displacement related to the CI caldera collapse may be significantly larger. The submerged caldera depression accommodates post-eruption sediments. Within this high-resolution archive, two major unconformities developed at 8.6 ka and 5 ka, when resurgence-related uplift exceeded the rate of sea-level rise concurrent with the emersion of the La Starza terrace. A previously unknown post-collapse submarine volcanic mound located between Nisida Island and Nisida Bank probably formed between 4.8 and 3.7 ka. Also, the Penta Palummo Bank appears to be constructed of at least two monogenetic volcanic edifices

  20. The structural setting of the Ischia Island Caldera (Italy): first evidence from seismic and gravity data

    Science.gov (United States)

    Capuano, Paolo; De Matteis, Raffaella; Russo, Guido

    2015-09-01

    Ischia Island is one of the active volcanoes of the Neapolitan area (Italy). Hazard assessment of active, densely populated volcano is primarily based on knowledge of the volcano's past behaviour and of its present state. As a contribution to the definition of the present structural setting of Ischia Island, we constructed a new model of the shallow crust using geophysical data: seismic wave travel times and Bouguer anomaly data. We analysed these data sets through seismic tomography and gravity data inversion. The main results inferable from the 3D seismic and gravity images are the definition of the caldera rim along the perimeter of the island, as hypothesized by many authors, and the presence of a high velocity and density area inside the caldera consistent with extension of the resurgent block that characterizes the recent deformation of the island.

  1. 3D Imaging of Brittle/Ductile transition of the crust beneath the resurgent calderas

    Science.gov (United States)

    Tizzani, P.; Castaldo, R.; Pepe, S.; Solaro, G.

    2012-04-01

    Rheology is a crucial factor to understand the mechanical behaviour and evolution of the crust in young and tectonically active belts. The aim of this paper is to investigate the rheological properties of the crust beneath resurgent calderas as Long Valley caldera (California USA) and Campi Flegrei (Southern Italy). Through the rheological proprieties of the calderas area, we highlight the driving process that determine the cut off of the local seismicity [K. Ito, 1993]. In this context, we consider the thermal proprieties and mechanical heterogeneity of the crust in order to develop a 3D conductive time dependent thermal model of the upper crust beneath the two calderas. More specifically we integrate geophysical information (gravimetric, seismic and boreholes data) available for the considered area in FEM environment [Manconi A. et al., 2010]. We performed a numerical solution of Fourier equation to carry out an advance optimization of the real measured data. We produce a set of forward models and propose, in order to analyse and solve the statistical problem, the Monte Carlo optimization procedures as Genetic Algorithm [Manconi A. et al., 2009]. In particular we search for the heat production, the volume source distribution and the surface emissivity parameters that providing the best-fit of the geothermal profiles data measured at boreholes, by solving the non stationary heat flow equation (Campanian Ignimbrite eruption about 40 kyr for Campi Flegrei caldera and Bishop tuff eruption about 700 kyr for Long Valley caldera). The performed thermal fields allow us to obtain the rheological stratification of the crust beneath two resurgent calderas; the models suggest that the uprising of a ductile layer which connects the upper mantle to the volcanic feeding system could determine the stress conditions that controlled the distribution of seismicity. In fact, the computed 3D imaging of Brittle/Ductile transition well agrees with the seismic hypocentral distribution

  2. Zircon oxygen isotopes reveal Ivrea-Verbano Zone source characteristics of the Sesia Valley Caldera

    Science.gov (United States)

    Economos, R. C.; Quick, J. E.; Sinigoi, S.; de Silva, S. L.

    2013-12-01

    The Sesia Valley, in the Italian Alpine foothills, contains >14 km diameter caldera adjacent to and structurally shallower than the famous Ivrea-Verbano Zone deep crustal section. The caldera and its associated eruptive sequence presents opportunity to explore volcanic magmatism in light of exposed and well characterized source candidates, namely lower crustal gabbros and the mid-crustal metasedimentary Kinzigite formation. Original geochemical characteristics of volcanic units have been obscured by the effects of subsequent hydrothermal alteration. The resistance of the mineral zircon to fluid alteration makes it a prime candidate for the preservation and exploration of these geochemical signals, such as O isotopes. Lower crustal gabbros in the Ivrea-Verbano Zone have broadly monotonic whole-rock δ18O values between +8 and +9‰VSMOW (Sinigoi et al., 1994). Kinzigites preserve a much higher and more heterogeneous δ18O values, typically ranging from +10‰ up to +15‰ (Baker, 1990). Zircons from the caldera-forming rhyolitic eruption units and a pre-caldera rhyodacitic unit were analyzed by ion microprobe at UCLA for in-situ oxygen isotope ratios. External reproducibility of within-mount standard R33 grains range from 0.27 to 0.36‰. Rhyolites from the caldera-forming eruption yield a range of δ18O(zircon) values from 6.3‰ to 8.3‰. This range displays rough correlation with CL activity - CL active grains have lower δ18O(zircon) values while CL dark grains have higher δ18O(zircon) values. This variation may correlate with U contents, which are notoriously low in zircons from Ivrea-Verbano Zone gabbros. We argue that the range in O isotope values suggests zircons are a good fit for magmas influenced by gabbro and Kinzigite sources. However, these zircons do not appear to be inherited directly from either the gabbro or Kinzigite sources as their O isotope signatures are typically intermediate between the two. The pre-caldera rhyodacite sample displays a

  3. Gradual caldera collapse at Bárdarbunga volcano, Iceland, regulated by lateral magma outflow.

    Science.gov (United States)

    Gudmundsson, Magnús T; Jónsdóttir, Kristín; Hooper, Andrew; Holohan, Eoghan P; Halldórsson, Sæmundur A; Ófeigsson, Benedikt G; Cesca, Simone; Vogfjörd, Kristín S; Sigmundsson, Freysteinn; Högnadóttir, Thórdís; Einarsson, Páll; Sigmarsson, Olgeir; Jarosch, Alexander H; Jónasson, Kristján; Magnússon, Eyjólfur; Hreinsdóttir, Sigrún; Bagnardi, Marco; Parks, Michelle M; Hjörleifsdóttir, Vala; Pálsson, Finnur; Walter, Thomas R; Schöpfer, Martin P J; Heimann, Sebastian; Reynolds, Hannah I; Dumont, Stéphanie; Bali, Eniko; Gudfinnsson, Gudmundur H; Dahm, Torsten; Roberts, Matthew J; Hensch, Martin; Belart, Joaquín M C; Spaans, Karsten; Jakobsson, Sigurdur; Gudmundsson, Gunnar B; Fridriksdóttir, Hildur M; Drouin, Vincent; Dürig, Tobias; Aðalgeirsdóttir, Guðfinna; Riishuus, Morten S; Pedersen, Gro B M; van Boeckel, Tayo; Oddsson, Björn; Pfeffer, Melissa A; Barsotti, Sara; Bergsson, Baldur; Donovan, Amy; Burton, Mike R; Aiuppa, Alessandro

    2016-07-15

    Large volcanic eruptions on Earth commonly occur with a collapse of the roof of a crustal magma reservoir, forming a caldera. Only a few such collapses occur per century, and the lack of detailed observations has obscured insight into the mechanical interplay between collapse and eruption. We use multiparameter geophysical and geochemical data to show that the 110-square-kilometer and 65-meter-deep collapse of Bárdarbunga caldera in 2014-2015 was initiated through withdrawal of magma, and lateral migration through a 48-kilometers-long dike, from a 12-kilometers deep reservoir. Interaction between the pressure exerted by the subsiding reservoir roof and the physical properties of the subsurface flow path explain the gradual, near-exponential decline of both collapse rate and the intensity of the 180-day-long eruption.

  4. Using InSAR to investigate long term caldera unrest: case studies from Yellowstone and Long Valley

    Science.gov (United States)

    battaglia, maurizio

    2016-04-01

    Interpreting geodetic measurements can be particularly difficult in the case of slow, years-to-decades deformation, such as that commonly observed at large Quaternary silicic calderas. For example, Yellowstone caldera has shown a complex behavior over recent decades: uplift of resurgent domes within the caldera started sometime after 1923, reaching a total of 90 cm, but in 1984 the deformation reversed to subsidence at a rate of 1-2 cm/yr until 1992. Starting in 1992, the deformation began migrating from one resurgent dome to the other, and deformation was also detected along the caldera boundary - the so-called Northern Caldera Rim - starting in the mid-1990s. Evidence from geodetic surveys suggests that magma intrusion and/or pressurization of hydrothermal fluids may both drive uplift at Yellowstone. Geodetic measurements at Long Valley caldera have also revealed multiple episodes of caldera uplift, but in contrast to Yellowstone, deformation is largely restricted to the caldera's single resurgent dome. The fact that the energy released during the resurgent dome uplift is much larger than that which can be explained by seismic activity within and around the caldera, together with the observation that the onset of accelerated deformation precedes increases in earthquake activity by several weeks, suggests that the major source of caldera unrest is probably magma intrusion beneath the resurgent dome. Here we present time series of surface deformation for Yellowstone and Long Valley retrieved by applying the SBAS InSAR technique. We estimate the average regional deformation signal by using the mean velocity values derived from coherent SAR pixels belonging to areas outside the caldera. This tectonic signal is removed from the InSAR displacement and we modeled the InSAR, leveling, and gravity measurements to retrieve the best fitting source parameters. For Yellowstone caldera, different distinct sources, either hydrothermal or magmatic, have been intermittently

  5. Decadal to monthly timescales of magma transfer and reservoir growth at a caldera volcano.

    Science.gov (United States)

    Druitt, T H; Costa, F; Deloule, E; Dungan, M; Scaillet, B

    2012-02-01

    Caldera-forming volcanic eruptions are low-frequency, high-impact events capable of discharging tens to thousands of cubic kilometres of magma explosively on timescales of hours to days, with devastating effects on local and global scales. Because no such eruption has been monitored during its long build-up phase, the precursor phenomena are not well understood. Geophysical signals obtained during recent episodes of unrest at calderas such as Yellowstone, USA, and Campi Flegrei, Italy, are difficult to interpret, and the conditions necessary for large eruptions are poorly constrained. Here we present a study of pre-eruptive magmatic processes and their timescales using chemically zoned crystals from the 'Minoan' caldera-forming eruption of Santorini volcano, Greece, which occurred in the late 1600s BC. The results provide insights into how rapidly large silicic systems may pass from a quiescent state to one on the edge of eruption. Despite the large volume of erupted magma (40-60 cubic kilometres), and the 18,000-year gestation period between the Minoan eruption and the previous major eruption, most crystals in the Minoan magma record processes that occurred less than about 100 years before the eruption. Recharge of the magma reservoir by large volumes of silicic magma (and some mafic magma) occurred during the century before eruption, and mixing between different silicic magma batches was still taking place during the final months. Final assembly of large silicic magma reservoirs may occur on timescales that are geologically very short by comparison with the preceding repose period, with major growth phases immediately before eruption. These observations have implications for the monitoring of long-dormant, but potentially active, caldera systems.

  6. Servicio de M-comercio: Sistema de interacción entre un centro comercial y sus visitantes utilizando las tecnologías WAP y Bluetooth M-commerce service: Interaction system between a mall and visitors using WAP and Bluetooth technologies

    Directory of Open Access Journals (Sweden)

    Jorge Gómez Rojas

    2013-04-01

    Full Text Available El servicio de interacción es un medio de comunicación que mejora las relaciones comerciales entre los centros comerciales y sus visitantes, utilizando las tecnologías de comunicaciones móviles WAP y Bluetooth como una nueva alternativa de negocios, y sin usar la red del operador de telefonía móvil celular. El sistema de interacción mencionado permite el intercambio de información de un grupo potencial de compradores entre los visitantes de un centro comercial y la administración de los diferentes comercios utilizando el teléfono celular. El sistema se compone de una aplicación móvil en J2ME, puntos de acceso Bluetooth y Wi-Fi, un servidor Bluetooth y un servidor Web con aplicaciones para ser accedidas por dispositivos móviles.The interaction service is a means of communication that improves trade relations between the mall and visitors using mobile communications technology WAP and Bluetooth, as a new business alternative, and without operator's network using the mobile phone. The proposed system of interaction, allows the exchange of information from a potential pool of buyers among visitors to a shopping center and the administration of the various shops, through the cell phone. The system consists of a mobile application in J2ME, the access points, Bluetooth server, and Web server with applications to mobile devices.

  7. Surface Deformation of Los Humeros Caldera, Mexico, Estimated by Interferometric Synthetic Aperture Radar (InSAR).

    Science.gov (United States)

    Santos Basurto, R.; Lopez Quiroz, P.; Carrasco Nuñez, G.; Doin, M. P.

    2014-12-01

    Los Humeros caldera is located in the eastern part of the Trans-Mexican Volcanic Belt, to the north of the state of Puebla and bordering the west side of the state of Veracruz. The study of the caldera, is of great interest because there is a geothermal field currently working inside of it. In fact, Los Humeros, is the third more important geothermal field in Mexico. In this work, we used InSAR to estimate the surface deformation on the caldera, aiming to contribute to its modeling and to help preventing subsidence related hazards on the geothermal field and surroundings. On this study, we calculated 34 interferograms from 21 SAR images of the ENVISAT European Space Agency Mission. The analysis of the interferograms, allow us to detect, decorrelation of the interferometric signal increased, when time spans were greater than 70 days. Also, for those with good signal correlation, the atmospheric signal dominated the interferogram, masking completely the deformation. Moreover, residual orbital ramps were detected, in some of the calculated interferograms. An algorithm capable to remove all the interferogram signal contributions but the deformation related, has been implemented. Resulting deformation and its correlation with several variables like the geology, the hydrogeology and the seismic records, were analysed through its integration in a Geographic Information System.

  8. Proceedings of the symposium on the Long Valley Caldera: A pre-drilling data review

    Energy Technology Data Exchange (ETDEWEB)

    Goldstein, N.E. (ed.)

    1987-09-01

    This proceedings volume contains papers or abstracts of papers presented at a two-day symposium held at the Lawrence Berkeley Laboratory (LBL) on 17 and 18 March 1987. Speakers presented a large body of new scientific results and geologic-hydrogeoloic interpretations for the Long Valley caldera. The talks and the discussions that followed focused on concepts and models for the present-day magmatic-hydrothermal system. Speakers at the symposium also addressed the topic of where to site future scientific drill holes in the caldera. Deep scientific drilling projects such as those being contemplated by the DOE Division of Geothermal Technology (DGT), under the Magma Energy Program, and by the DOE Office of Energy Research, Division of Engineering and Geosciences (DEG), along with the USGS and NSE, under the Continental Scientific Drilling Program (CSDP), will be major and expensive national undertakings. DOE/DEG is sponsoring a program of relatively shallow coreholes in the caldera, and DOE/DGT is considering the initiation of a multiphase program to drill a deep hole for geophysical observations and sampling of the ''near magmatic'' environment as early as FY 1988, depending on the DOE budget. Separate abstracts have been prepared for the individual papers.

  9. Reconstructing the evoluortunity to study processes related to composite volction of an eroded Miocene caldera volcano (Yamanlar volcano, İzmir, Turkey)

    Science.gov (United States)

    Karaoğlu, Özgür; Brown, Richard J.

    2016-05-01

    The Miocene Yamanlar composite volcano is located in the central part of a shear zone in western Turkey. The volcano's deeply-eroded interior provides excellent three-dimensional exposure of a faulted caldera-floor and caldera-fill rocks as well as surrounding extracaldera ignimbrites. We present a much-revised stratigraphy and geological map of Yamanlar in order to quantify the evolutionary stages of the volcano. The Yamanlar volcanic cone was composed of > 800 m of basaltic-andesite to andesite lavas and lava domes. The volcano underwent at least one phase of caldera formation associated with an explosive eruption that deposited an ignimbrite sheet within and outside the caldera. Lithofacies architecture analysis is applied to the proximal and medial exposures of the Early-Middle Yamanlar Formation, which occurs outside of the caldera. Field evidence of the succession indicates a caldera-forming eruption. Our results indicate that the formation of the Yamanlar caldera resulted from one major catastrophic eruption that generated several sustained pyroclastic density currents (PDCs) subdivided by fall deposits with sharp contacts. The ignimbrite sheet is composed of four flow units. The presence of numerous coarse-grained lithic-rich horizons within the ignimbrite sheet is consistent with caldera subsidence. Post-caldera volcanism is indicated by intrusions and lava domes erupted along the inferred caldera-bounding faults, some of which record ~ 90 m of displacement. Widespread, coarse-grained breccias that overlie the ignimbrite sheet are interpreted as debris avalanche deposits resulting from gravitational failure of the flanks of the volcano or the caldera wall during or after caldera subsidence.

  10. Facies analysis of an ancient, dismembered, large caldera complex and implications for intra-arc subsidence: Middle Jurassic strata of Cobre Ridge, southern Arizona, USA

    Science.gov (United States)

    Riggs, Nancy R.; Busby-Spera, Cathy J.

    1991-11-01

    The Middle Jurassic (˜ 170 Ma) Cobre Ridge caldera is an elongate caldera complex that formed during the eruption of the tuff of Pajarito, a crystal-rich rhyodacite ignimbrite with an estimated volume > 1000 km 3. The caldera subsided in two subequal blocks: to the southeast, caldera-forming ignimbrite is as much as 3000 m thick, whereas the northwest half of the caldera subsided to lesser depths during the initial eruption, but was the locus of subsidence during subsequent eruptions, providing a depocenter for a > 1.5 km-thick section of secondary- and post-collapse volcanic and sedimentary strata. These strata record moat formation and filling and waning volcanism, including: (1) areally restricted ignimbrites up to several tens of meters thick that may have been ponded between caldera margins and/or fault scarps; (2) a ⩾ 600 m-thick ignimbrite whose eruption probably caused further collapse of the caldera or enlargement of the caldera margins; (3) a localized debris apron deposit up to 500 m thick that represents material reworked from intra-caldera pyroclastic deposits and possibly caldera walls; and (4) eolian and fluvial sandstones and water-lain tuffs. Megabreccia blocks as large as 0.5 km along strike probably demarcate approximate caldera margins, suggesting that the composite caldera was approximately 50 km long by 25 km wide. The preserved thickness of the strata of Cobre Ridge ( > 4500 m) is greater than many ancient continental volcanic sequences, suggesting external (i.e. tectonic) controls on subsidence, but preservation of this great thickness of strata is apparently due entirely to volcanic subsidence.

  11. Eruptive history, geochronology, and post-eruption structural evolution of the late Eocene Hall Creek Caldera, Toiyabe Range, Nevada

    Science.gov (United States)

    Colgan, Joseph P.; Henry, Christopher D.

    2017-02-24

    The magmatic, tectonic, and topographic evolution of what is now the northern Great Basin remains controversial, notably the temporal and spatial relation between magmatism and extensional faulting. This controversy is exemplified in the northern Toiyabe Range of central Nevada, where previous geologic mapping suggested the presence of a caldera that sourced the late Eocene (34.0 mega-annum [Ma]) tuff of Hall Creek. This region was also inferred to be the locus of large-magnitude middle Tertiary extension (more than 100 percent strain) localized along the Bernd Canyon detachment fault, and to be the approximate location of a middle Tertiary paleodivide that separated east and west-draining paleovalleys. Geologic mapping, 40Ar/39Ar dating, and geochemical analyses document the geologic history and extent of the Hall Creek caldera, define the regional paleotopography at the time it formed, and clarify the timing and kinematics of post-caldera extensional faulting. During and after late Eocene volcanism, the northern Toiyabe Range was characterized by an east-west trending ridge in the area of present-day Mount Callaghan, probably localized along a Mesozoic anticline. Andesite lava flows erupted around 35–34 Ma ponded hundreds of meters thick in the erosional low areas surrounding this structural high, particularly in the Simpson Park Mountains. The Hall Creek caldera formed ca. 34.0 Ma during eruption of the approximately 400 cubic kilometers (km3) tuff of Hall Creek, a moderately crystal-rich rhyolite (71–77 percent SiO2) ash-flow tuff. Caldera collapse was piston-like with an intact floor block, and the caldera filled with thick (approximately 2,600 meters) intracaldera tuff and interbedded breccia lenses shed from the caldera walls. The most extensive exposed megabreccia deposits are concentrated on or close to the caldera floor in the southwestern part of the caldera. Both silicic and intermediate post-caldera lavas were locally erupted within 400 thousand

  12. Measurement of high turbidity water behavior by ADCP at Izena Caldera in Okinawa Trough

    Science.gov (United States)

    Furuta, S.; Arai, R.; Yamazaki, T.

    2012-12-01

    Hydrothermal processes associated with spreading centers of plate-tectonics form hydrothermal activities and the resulted seafloor massive sulfide (SMS) deposits. Given that the SMS deposits found in the western Pacific have been considered to be potential sources of gold, silver, copper, zinc, and lead, there is a strong possibility that they will be mined near future. In order to take measures against environmental impacts during the mining of SMS deposits, it is important to measure components of hydrothermal origin with high temporal and spatial resolution on site, and to understand the mass circulation and transfer systems around the mining area. The Acoustic Doppler Current Profiler (ADCP) is effective tool for measurement of current field in water column in general. In addition, it is also useful for detection of turbidity profile in the water column simultaneously, applying an acoustic propagation model to the data. Izena Caldera, which is 3 km in short, 6 km in long axes and is generically from1,600 m to 1,700 m in depth, is located at the northwest of Okinawa Island. There both attractive SMS deposits and active hydrothermal vent systems have been confirmed. Because of the active vent systems and a bowl-like geographical structure, a quite unique mass circulation and transfer background condition is expected in Izena Caldera. The mining operation will add plenty of suspended materials into the background condition. For a primary understanding of the background condition, the authors analyzed the ADCP data and found two high-turbidity water zones in Izena Caldera and their behavior relationships with the current structure. The vertical downward current affects one of the high-turbidity zones around 1,220 m in depth. The current velocity against north-south direction and east-west direction affects the other high-turbidity zone 1,550 m in depth. Also the zones are recognized the higher synchronization with the lumi-solar diurnal tide, about 24 hours. The

  13. Volcano hazards implications of rhyolitic melt or magma at shallow depth under Krafla Caldera

    Science.gov (United States)

    Eichelberger, John; Papale, Paolo; Sigmundsson, Freysteinn

    2014-05-01

    Krafla Caldera in northern Iceland is a well-monitored and extensively drilled caldera system that underwent a major rifting and eruption episode in 1975 to 1984. The recent surprise discovery of ~900oC "magma" (crystal+melt felsite and possibly crystal-poor rhyolite magma as well) in the Iceland Deep Drilling Project borehole #1 (IDDP-1) in 2009, as well as previous less publicized drilling encounters with rhyolite melt, challenges our understanding of caldera unrest. Further drilling may lead to improved understanding of volcanic hazards in calderas and better interpretation of precursory deformation and seismic signals that may herald eruption. Salient features of the IDDP-1 discovery relative to volcanic hazards are: 1. The rhyolite magma is at only 2.1 km depth. If such magma were known to have intruded to such shallow depth in a populated caldera, there would likely be serious discussion of evacuating the population. 2. The drill site was chosen because magma was not expected at shallow depth, based on the occurrence of seismicity to twice that depth beneath the site during the last eruption, and on 3-D resistivity structure. 3. The eruption was entirely basaltic; no rhyolite reached the surface. Thus, rhyolite magma intruded to shallow depth and was stored there without erupting and without being detected either geophysically or petrologically. An alternative, which seems unlikely, is that the rhyolite evolved from basalt or by basalt-induced partial melting after 1984. If it is possible to return to this magmatic body through further drilling, as recently proposed to the International Continental Scientific Drilling Program (ICDP) by the Krafla Magma Drilling Project, complementary field, laboratory experiments, and computational experiments can be conducted to understand the "source" and how it produces deformation, seismic, and geochemical signals at the surface. Experiments could include injection of fluid with tracers directly into the melt-bearing zone

  14. Planeamento de uma estrada utilizando CCS Candy - Caso de estudo

    OpenAIRE

    Oliveira, Sara Maria de

    2013-01-01

    O tema desta dissertação foi escolhido tendo em consideração a crescente necessidade de planeamento de empreitadas de construção de estradas, sendo um dos objetivos desta dissertação o de oferecer uma visão global do processo de planeamento da construção de uma estrada, focado apenas no fator tempo, recorrendo a ferramentas informáticas e utilizando um caso de estudo de uma estrada real e já construída. Inicialmente, faz-se uma breve descrição dos métodos de planeamento mais aplicados em p...

  15. REFRIGERAÇÃO UTILIZANDO PASTILHAS DE EFEITO PELTIER

    Directory of Open Access Journals (Sweden)

    Antonio Luiz P. S. Campos

    2010-06-01

    Full Text Available Pastilhas de Peltier são dispositivos baseados no efeito Peltier e são aplicadas para produzir efeito refrigerador ou aquecedor. Este trabalho aborda conceitos envolvidos na fabricação e funcionamento desses dispositivos tais como: histórico do efeito Peltier e desenvolvimento de placas de efeito Peltier. É feito um estudo de eficiência da refrigeração de água utilizando uma placa de efeito Peltier existente no Campus Natal – Zona Norte. Para isso, é implementada uma estrutura de refrigeração de água e são feitas medições para determinar a eficiência de sistema. Por fim, são apresentadas conclusões sobre o estudo desenvolvido.

  16. History of surface displacements at the Yellowstone Caldera, Wyoming, from leveling surveys and InSAR observations, 1923-2008

    Science.gov (United States)

    Dzurisin, Daniel; Wicks, Charles W.; Poland, Michael P.

    2012-01-01

    Modern geodetic studies of the Yellowstone caldera, Wyoming, and its extraordinary tectonic, magmatic, and hydrothermal systems date from an initial leveling survey done throughout Yellowstone National Park in 1923 by the U.S. Coast and Geodetic Survey. A repeat park-wide survey by the U.S. Geological Survey (USGS) and the University of Utah during 1975-77 revealed that the central part of the caldera floor had risen more than 700 mm since 1923, at an average rate of 14±1 mm/yr. From 1983 to 2007, the USGS conducted 15 smaller surveys of a single level line that crosses the northeast part of the caldera, including the area where the greatest uplift had occurred from 1923 to 1975-77. The 1983 and 1984 surveys showed that uplift had continued at an average rate of 22±1 mm/yr since 1975-77, but no additional uplift occurred during 1984-85 (-2±5 mm/yr), and during 1985-95 the area subsided at an average rate of 19±1 mm/yr. The change from uplift to subsidence was accompanied by an earthquake swarm, the largest ever recorded in the Yellowstone area (as of March 2012), starting in October 1985 and located near the northwest rim of the caldera. Interferometric synthetic aperture radar (InSAR) images showed that the area of greatest subsidence migrated from the northeast part of the caldera (including the Sour Creek resurgent dome) during 1992-93 to the southwest part (including the Mallard Lake resurgent dome) during 1993-95. Thereafter, uplift resumed in the northeast part of the caldera during 1995-96, while subsidence continued in the southwest part. The onset of uplift migrated southwestward, and by mid-1997, uplift was occurring throughout the entire caldera (essentially rim to rim, including both domes). Consistent with these InSAR observations, leveling surveys indicated 24±3 mm of uplift in the northeast part of the caldera during 1995-98. The beginning of uplift was coincident with or followed shortly after an earthquake swarm near the north caldera rim

  17. Is there a geochemical link between volcanic and plutonic rocks in the Organ Mountains caldera?

    Science.gov (United States)

    Memeti, V.; Davidson, J.

    2013-12-01

    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

  18. Magma plumbing system at the beginning of repeated caldera eruption: A case study on Aso-1 erupted about 270 ky ago from Aso caldera, SW Japan

    Science.gov (United States)

    Miyagi, I.; Hoshizumi, H.; Miyabuchi, Y.

    2015-12-01

    In order to understand the commencement of magma plumbing system of a polygenetic caldera, we started petrological study on the earliest eruptive product of Aso caldera, SW Japan. Aso caldera is one of the active volcano in Japan which have produced four stages (Aso-1, -2, -3, -4) of large-scale pyroclastic flow deposits 270 to 90 ky. ago. A suite of samples were collected from the bottom of Aso-1 pyroclastic flow deposit and from the underlying tephra layer (Ono et al., 1979). The tephra comprises more than 10 pumice fall units inter-layered by dark gray volcanic ash. For whole rock chemistry, coarser pumice fragments were separated. For mineral and glass chemistry, phenocrysts and glass particles were handpicked from the sieved 500-1000 um fractions under a binocular microscope. This fraction consist of plagioclase, orthopyroxene, variably vesiculated volcanic glass fragments, and clinopyroxene phenocrysts. They were analyzed using an electron micro-probe. The suite of samples are similar and major temporal change is the chemical composition of orthopyroxenes; those from upper horizon are relatively Mg rich. Anorthite content of plagioclase phenocryst is bimodal 49-53 mol. % (major) and 57-70 mol. % (minor). Silica content of matrix glass fall in a narrow range 68-70 wt. %. Temperature and oxygen fugacity were estimated to be 865-905 deg-C and FMQ+2 log unit, respectively, using ILMAT (Lepage, 2003). Pressure and water content of the magma are estimated to be 5-7 kbar and 0.5-1 wt. % H2O, respectively, using rhyolite-MELTS (Gualda et al., 2012) on the most undifferentiated tholeiitic basalt of Aso 4KC-03 (Hunter, 1998) to reproduce the observed composition of matrix glass (68-70 wt. % SiO2) and plagioclase (An 49-53 mol. %). The calcic plagioclase (An 57-70 mol. %), however, suggest that the basalt was initially hydrous and require magma degassing before the differentiation. If we assume degassing by magma convection in a conduit (Kazahaya et al., 1994), the

  19. Early Miocene Kırka-Phrigian Caldera, western Turkey (Eskişehir province), preliminary volcanology, age and geochemistry data

    Science.gov (United States)

    Seghedi, Ioan; Helvacı, Cahit

    2016-11-01

    Large rhyolitic ignimbrite occurrences are closely connected to the Early Miocene initiation of extension in the central-western Anatolia crossing the Tavşanlı-Afyon zones. Field and laboratory data performed at the apex of the Eskişehir-Afyon-Isparta volcanic area allowed recognition of newly identified caldera structure, named here "Kırka-Phrigian caldera". Transtensive/distensive tectonic stresses since 25 Ma ago resulted in the NNW-SSE elongation of the magma chamber and influenced the roughly elliptical shape of the subsided block (caldera floor). The caldera, which is roughly oval (24 km × 15 km) in shape, formed during a series of collapse events, starting at 19 Ma, by the generation of a huge volume of extra- and intracaldera ignimbrites. Intracaldera post-collapse sedimentation and further volcanism at the northern edge (at 18.6 Ma) were controlled through subsidence-related faults with generation of a series of volcanic structures (domes and lavas) showing a large compositional range. Enriched mantle components within the subcontinental lithospheric mantle began to melt via decompression melting during the initiation of extension. The heat resulting from the fractionation of ascending mantle melts produced the silicic compositions in large mushy crustal reservoirs; interaction of these melts with fertile crustal rocks further caused crustal anataxis and consequently two different compositions: Rhyolite-1 and Rhyolite-2. The eruptions of Kırka-Phrigian caldera-related ignimbrites were probably triggered by basaltic intrusion. Rock volumes and geochemical evidence suggest that silicic volcanic rocks come from a long-lived complex magma chamber system. After caldera generation there was a northern shift to small volume extra- and intra-caldera episodic rhyolitic, basaltic-trachy andesitic, trachytic and lamproitic volcanism, the latter being the youngest (16.2 Ma) indicating a more primitive magma input which originated in an enriched mantle

  20. Cuantificación y procedencia de los intercambios de CO2 en un ecosistema carbonatado mediante la técnica de eddy covariance y el análisis de los isótopos estables de carbono

    Directory of Open Access Journals (Sweden)

    P. Serrano-Ortiz

    2010-01-01

    Full Text Available Los intercambios de CO2 entre atmósfera y ecosistemas, así como los procesos que intervienen en dichos intercambios, son de vital interés para la caracterización del ciclo global del carbono y la repercusión del calentamiento global sobre estos ecosistemas naturales. En ecosistemas de origen carbonatado, los procesos biológicos de fotosíntesis y respiración interactúan con procesos de ventilación de cavidades y de disolución y precipitación de carbonatos que pueden incluso dominar el intercambio de CO2 en determinadas épocas del año. En este trabajo, se usó la técnica de eddy covariance junto con análisis de los isótopos estables de carbono y medidas de flujo de CO2 de suelo y otras variables meteorológicas, para determinar la procedencia del CO2 intercambiado. Los resultados obtenidos demuestran que el ecosistema actúa como sumidero o fuente de CO2 en función de las condiciones meteorológicas y la época del año. Bajo condiciones óptimas de temperatura y recursos hídricos, la huella isotópica del carbono (d13C del aire alcanza valores muy negativos indicando un origen biológico del intercambio. En épocas de sequía y senescencia biológica estos procesos se reducen considerablemente. La atmósfera externa y la cavidad toman valores de d13C muy similares indicando un alto grado de ventilación de la cavidad.

  1. A catalogue of caldera unrest at Taupo Volcanic Centre, New Zealand, using the Volcanic Unrest Index (VUI)

    Science.gov (United States)

    Potter, Sally H.; Scott, Bradley J.; Jolly, Gill E.; Johnston, David M.; Neall, Vince E.

    2015-09-01

    Caldera unrest occurs frequently at Taupo Volcanic Centre (TVC), New Zealand, occasionally resulting in deleterious socio-economic impacts. This large silicic volcano most recently erupted in 232 AD in an explosive, caldera-forming rhyolitic eruption, devastating the central North Island. Eruptions are preceded by volcanic unrest, often consisting of seismicity, deformation, degassing, and/or geothermal system changes. These phenomena may also occur due to non-magmatic processes, complicating eruption forecasting. As volcanic unrest may or may not lead to an eruption, it needs to be characterised to provide effective warnings; this is best achieved by understanding past unrest. In this research, a catalogue of caldera unrest at TVC is developed using an historical chronology methodology, spanning from 1872 to December 2011. The Volcanic Unrest Index (VUI), which is introduced by Potter et al. (2015), is estimated for the catalogue, demonstrating its use and providing a characterisation of unrest at TVC. Sixteen episodes of unrest are identified; 4 are classified as moderate unrest (VUI 3), and 12 are classified as minor unrest (VUI 2). There has been median interval of approximately 3 years between unrest episodes and a median unrest episode duration of just under 5 months. This research provides context for future caldera unrest crises at TVC and contributes to the global caldera unrest dataset.

  2. Conductive heat flux in VC-1 and the thermal regime of Valles caldera, Jemez Mountains, New Mexico ( USA).

    Science.gov (United States)

    Sass, J.H.; Morgan, P.

    1988-01-01

    Over 5% of heat in the western USA is lost through Quaternary silicic volcanic centers, including the Valles caldera in N central New Mexico. These centers are the sites of major hydrothermal activity and upper crustal metamorphism, metasomatism, and mineralization, producing associated geothermal resources. Presents new heat flow data from Valles caldera core hole 1 (VC-1), drilled in the SW margin of the Valles caldera. Thermal conductivities were measured on 55 segments of core from VC-1, waxed and wrapped to preserve fluids. These values were combined with temperature gradient data to calculate heat flow. Above 335 m, which is probably unsaturated, heat flow is 247 + or - 16 mW m-2. Inteprets the shallow thermal gradient data and the thermal regime at VC-1 to indicate a long-lived hydrothermal (and magmatic) system in the southwestern Valles caldera that has been maintained through the generation of shallow magma bodies during the long postcollapse history of the caldera. High heat flow at the VC-1 site is interpreted to result from hot water circulating below the base of the core hole, and we attribute the lower heat flow in the unsaturated zone is attributed to hydrologic recharge. -from Authors

  3. FESTIVALES DE INNOVACIÓN LOCAL: UN ESPACIO PARA EL INTERCAMBIO, EL APRENDIZAJE, LA COMUNICACIÓN Y LA COMERCIALIZACIÓN

    Directory of Open Access Journals (Sweden)

    Ania Yong

    2011-01-01

    Full Text Available El fomento de huertos familiares en la comunidadde San Andrés con el objetivo de promover la producción artesanal de conservas domésticas, es resultado de la realizaciónde visitas de intercambio y talleres de aprendizaje entreproductores urbanos y rurales. Estas acciones desarrolladas durante los años 2005 y 2006 propiciaron la adopción y adaptaciónde especies hortícolas en la localidad. A finales del año 2006,productoras y productores de La Palma, Pinar del Río comenzarona demandar espacios para mostrar el resultado de sus producciones,por lo que fue necesario crear espacios para que intercambiaran,aprendieran y comercializaran sus productos en la comunidad.Estos espacios fueron denominados Festivales de InnovaciónLocal y permitieron el reconocimiento de las potencialidadeslocales para producir alimentos sanos mediante tecnologíasamigables con el medio ambiente donde el productor ofrecía directamente a los consumidores sus productos e intercambiaba directamente con los consumidores.

  4. EVALUACIÓN DE LA ACTIVIDAD FOTOSINTÉTICA ASOCIADA CON EL INTERCAMBIO GASEOSO DE DOS VARIEDADES DE Coffea arabica OBTENIDAS POR CULTIVO In Vitro

    Directory of Open Access Journals (Sweden)

    Elizabeth Isaac

    2010-01-01

    Full Text Available El trabajo se desarrolló en el Laboratorio de Células y Cultivo de Tejidos del Centro de Bioplantas en julio de 2007, con el objetivo de evaluar la actividad fotosintética de las plántulas de Coffea arabica var. Catuai y Caturra rojo, obtenidas in vitro en fase de multiplicación. Se determinaron la tasa de fotosíntesis neta, transpiración, conductancia estomática y concentración de pigmentos clorofílicos para cada una de las variedades a las ocho semanas de cultivadas; las vitroplantas crecieron en condiciones controladas en un medio MS suplementado con 0,5 ¿mol de AIA y 5 ¿mol de 6-BAP. Los resultados mostraron que ambas variedades desarrolladas in vitro presentaron tasas de fotosíntesis neta similares a las plantas de cafeto adultas cultivadas en condiciones de campo, lo que demostró la capacidad de fotosíntesis de las plántulas, conservando un adecuado equilibrio para el intercambio gaseoso en el proceso fotosintético durante la etapa de multiplicación in vitro.

  5. Redes de participación e intercambios en la radio pública: los podcasting Networks of Participation and Communicative Interchanges in Public Radio: Podcasting

    Directory of Open Access Journals (Sweden)

    Carmen Salgado Santamaría

    2009-10-01

    Full Text Available El desarrollo de los podcasting, como sistema añadido de la ciberradio, impulsa a las redes de participación e intercambios comunicativos de interés social, que exhiben numerosas ventajas frente a las prácticas radiofónicas conocidas. La difusión que la radio pública realiza de los podcasts, la colocan en el actual proceso de convergencia tecnológica, y la sitúan en una sociedad de la información y del conocimiento, capaz de ofrecer diferentes servicios al alcance de todos los ciudadanos. Sólo la introducción de nuevos contenidos y servicios que aporten valor añadido a los existentes y satisfagan las necesidades de sus usuarios, procurarán la rentabilidad de este sistema. The development of podcasting as an additional system of cyberradio stimulates the appearance of networks of participation and communicative interchanges of social interest, and has numerous advantages over conventional radio practices. The spreading of podcasts through public radio situates it within the process of technological convergence and in an Information and Knowledge society which is able to offer different services within reach of all citizens. Only the introduction of new contents and services that contribute added value to the existing ones and satisfy the needs of users will make this system profitable.

  6. Insights into deposition and deformation of intra-caldera ignimbrites, central Nevada

    Science.gov (United States)

    MacDonald, William D.; Palmer, H. Currie; Deino, Alan L.; Shen, Po-Yu

    2012-11-01

    Magnetic studies, together with structural and 40Ar/39Ar age analyses, were used to investigate the development and deformation of ignimbrites of the Caetano Tuff formation in central-north Nevada. Magnetic susceptibility, susceptibility anisotropy (AMS) and magnetic remanence approaches were used to decipher events accompanying emplacement and subsequent deformation of that tuff, for both intracaldera tuffs and outflow deposits. 40Ar/39Ar ages, both those presented here and previously published ages, indicate about 33.8 Ma for the age of Caetano ignimbrites, approximately at the Eocene/Oligocene boundary. Although extensive faulting associated with regional extension of the Great Basin region has dissected these deposits, the thickness of the intra-caldera ignimbrites has been estimated at 3.5 km or more. Thermal modeling for cooling of a caldera filling of 3.5 km thickness indicates acquisition of remanent magnetization can persist up to 25 ka, sufficient to average secular variation. This contrasts with rapid cooling and remanence acquisition in outflow ignimbrites typically only tens of meters thick. A 750 m thick reference section was selected for more detailed study about 10 km to the west of the type area. This reference section, fault-bounded at both base and top, represents the upper part of the formation. Its lower member includes the uppermost 250 m of the lower massive resistant unit of ignimbrites, a middle member of 375 m of well stratified pyroclastic deposits, vitrophyres and sediments, and an upper member of about 125 m of recessive ignimbrite and thin-bedded clastic and pyroclastic deposits. Structural and magnetic remanence measurements suggest 13° eastward tilting of the caldera floor occurred early during deposition of the middle member. Flow directions inferred from AMS Kmax axes in the middle member diverge about 45° relative to those in the underlying member and suggest a change in vent source accompanying the deposition of the middle

  7. A fluid-driven earthquake swarm on the margin of the Yellowstone caldera

    Science.gov (United States)

    Shelly, David R.; Hill, David P.; Massin, Frederick; Farrell, Jamie; Smith, Robert B.; Taira, Taka'aki

    2013-01-01

    Over the past several decades, the Yellowstone caldera has experienced frequent earthquake swarms and repeated cycles of uplift and subsidence, reflecting dynamic volcanic and tectonic processes. Here, we examine the detailed spatial-temporal evolution of the 2010 Madison Plateau swarm, which occurred near the northwest boundary of the Yellowstone caldera. To fully explore the evolution of the swarm, we integrated procedures for seismic waveform-based earthquake detection with precise double-difference relative relocation. Using cross-correlation of continuous seismic data and waveform templates constructed from cataloged events, we detected and precisely located 8710 earthquakes during the three-week swarm, nearly four times the number of events included in the standard catalog. This high-resolution analysis reveals distinct migration of earthquake activity over the course of the swarm. The swarm initiated abruptly on January 17, 2010 at about 10 km depth and expanded dramatically outward (both shallower and deeper) over time, primarily along a NNW-striking, ~55º ENE-dipping structure. To explain these characteristics, we hypothesize that the swarm was triggered by the rupture of a zone of confined high-pressure aqueous fluids into a pre-existing crustal fault system, prompting release of accumulated stress. The high-pressure fluid injection may have been accommodated by hybrid shear and dilatational failure, as is commonly observed in exhumed hydrothermally affected fault zones. This process has likely occurred repeatedly in Yellowstone as aqueous fluids exsolved from magma migrate into the brittle crust, and it may be a key element in the observed cycles of caldera uplift and subsidence.

  8. Mineral and chemical variations within an ash-flow sheet from Aso caldera, Southwestern Japan

    Science.gov (United States)

    Lipman, P.W.

    1967-01-01

    Although products of individual volcanic eruptions, especially voluminous ash-flow eruptions, have been considered among the best available samples of natural magmas, detailed petrographic and chemical study indicates that bulk compositions of unaltered Pleistocene ash-flow tuffs from Aso caldera, Japan, deviate significantly from original magmatic compositions. The last major ash-flow sheet from Aso caldera is as much as 150 meters thick and shows a general vertical compositional change from phenocryst-poor rhyodacite upward into phenocryst-rich trachyandesite; this change apparently reflects in inverse order a compositionally zoned magma chamber in which more silicic magma overlay more mafic magma. Details of these magmatic variations were obscured, however, by: (1) mixing of compositionally distinct batches of magma during upwelling in the vent, as indicated by layering and other heterogeneities within single pumice lumps; (2) mixing of particulate fragments-pumice lumps, ash, and phenocrysts-of varied compositions during emplacement, with the result that separate pumice lenses from a single small outcrop may have a compositional range nearly as great as the bulk-rook variation of the entire sheet; (3) density sorting of phenocrysts and ash during eruption and emplacement, resulting in systematic modal variations with distance from the caldera; (4) addition of xenocrysts, resulting in significant contamination and modification of proportions of crystals in the tuffs; and (5) ground-water leaching of glassy fractions during hydration after cooling. Similar complexities characterize ash-flow tuffs under study in southwestern Nevada and in the San Juan Mountains, Colorado, and probably are widespread in other ash-flow fields as well. Caution and careful planning are required in study of the magmatic chemistry and phenocryst mineralogy of these rocks. ?? 1967 Springer-Verlag.

  9. Survey and assessment of post volcanic activities of a young caldera lake, Lake Cuicocha, Ecuador

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    G. Gunkel

    2009-05-01

    Full Text Available Cuicocha is a young volcano adjacent to the inactive Pleistocene Cotacachi volcano complex, located in the western cordilleras of the Ecuadorian Andes. A series of eruptions with intensive ash emission and collapse of the caldera occurred around 4500–3000 y BP. A crater 3.2 km in diameter and a maximum depth of 450 m was formed. Further eruptions of the volcano occurred 1300 y BP and formed four smaller domes within the caldera. Over the last few hundred years, a caldera lake has developed, with a maximum depth of 148 m. The lake water is characterized by sodium carbonate with elevated concentrations of manganese, calcium and chloride. Nowadays, an emission of gases, mainly CO2, and an input of warm spring water occur in Lake Cuicocha. The zone of high activity is in the western basin of the lake at a depth of 78 m, and continuous gas emissions with sediment resuspension were observed using sonar. In the hypolimnion of the lake, CO2 accumulation occurs up to 0.2% saturation, but the risk of a limnic eruption can be excluded at present. The lake possesses monomictic stratification behaviour, and during overturn an intensive gas exchange with the atmosphere occurs. Investigations concerning the sedimentation processes of the lake suggest only a thin sediment layer of up to 10–20 cm in the deeper lake basin; in the western bay, in the area of gas emissions, the lake bottom is partly depleted of sediment in the form of holes, and no lake colmation exists. Decreases in the lake water level of about 30 cm y−1 indicate a percolation of water into fractures and fissures of the volcano, triggered by a nearby earthquake in 1987.

  10. The Laramide Mesa formation and the Ojo de Agua caldera, southeast of the Cananea copper mining district, Sonora, Mexico

    Science.gov (United States)

    Cox, Dennis P.; Miller, Robert J.; Woodbourne, Keith L.

    2006-01-01

    The Mesa Formation extends from Cananea, Mexico, southeast to the Sonora River and is the main host rock of Laramide porphyry copper deposits in the Cananea District and at the Alacran porphyry prospect to the east. The Mesa consists of two members-a lower andesite and an upper dacite. The lowest part of the dacite member is a crystal tuff about 100 m thick. This tuff is the outfall of a caldera centered near the village of Ojo de Agua, dated by 40Ar/39Ar at 65.8 Ma ?0.4. The Ojo de Agua Caldera is about 9 km in diameter and is filled by a light gray biotite dacite tuff with abundant flattened pumice fragments. The volume of the caldera is estimated to be 24 km3.

  11. Modificaciones en las calderas igneotubulares cubanas // Modifications in the Cuban boilers of fire tube

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    I. Pérez Mallea

    1998-01-01

    Full Text Available El objetivo de este trabajo es optimizar y diseñar las calderas igneotubulares nacionales, incluyendo las de inversión de llama yagua caliente. Con este fin se creo un software como soporte científico técnico que permite realizar los diferentes cálculosverificativos a través de los cuales se optimiza._________________________________________________________________________Abstract .The objective of this work is the optimizing and designing of the Cuban boilers of fire tube, including those of inverting offlame and hot water. A software have been developed as technical scientific supper for different calculations and optimizingprocess.

  12. Pyroclastic eruptions from Axial caldera, Juan de Fuca Ridge, NE Pacific Ocean

    Energy Technology Data Exchange (ETDEWEB)

    Helo, Christoph; Stix, John [Department of Earth and Planetary Sciences, McGill University, 3450 University Street, Montreal, Quebec H3A 2A7 (Canada); Clague, Dave A [Monterey Bay Aquarium Research Institute 7700 Sandholdt Road, Moss Landing, CA 95039-9644 (United States)

    2008-10-01

    Unconsolidated volcaniclastic glass deposits on the flanks of Axial Seamount, a caldera system situated on the Juan de Fuca Ridge in the NE Pacific Ocean, demonstrate the occurrence of explosive events, in addition to effusive activity. The variety of produced glass fragments ranges from various angular forms to thin deep-sea limu o Pele, with dominantly moderately fractionated to occasionally primitive MOR basalt composition. A model involving the collapse of a magmatic foam layer may account for the observed spectrum of glass fragments.

  13. Reservoir processes and fluid origins in the Baca geothermal system, Valles Caldera, New Mexico ( USA).

    Science.gov (United States)

    Truesdell, A.H.; Janik, C.J.

    1986-01-01

    At the Baca geothermal field in the Valles caldera, New Mexico, 19 deep wells were drilled in an attempt to develop a 50-MW (megawatts electric) power plant. The chemical and isotopic compositions of steam and water samples have been used to indicate uniquely the origin of reservoir fluids and natural reservoir processes. Two distinct reservoir fluids exist at Baca. These fluids originate from the same deep, high-temperature (335oC), saline (2500 mg/kg Cl) parent water but have had different histories during upflow which are described.-after Authors

  14. Hydrothermal precious-metal deposits related to graben-calderas of the Sierra Madre Occidental

    Science.gov (United States)

    Aguirre-Diaz, G. J.; Labarthe-Hernandez, G.; Nieto-Obregon, J.; Tristan-Gonzalez, M.; Gonzalez-Partida, E.

    2007-05-01

    The Sierra Madre Occidental (SMO) covers the NW portion of Mexico and it is the host for several important precious metal mine operations, such as Tayoltita, Cienega, Topia, Fresnillo, Zacatecas, Guanajuato and Bolaños, just to mention a few. The southern part of the Basin and Range extension affected also NW Mexico and formed NW- to NE-trending normal faults that bound many large grabens, which are particularly long and deep in the southern SMO. Both graben formation and mid-Tertiary silicic volcanic activity coincided in space and time, particularly for the 38-23 Ma period, the Ignimbrite Flare-up event, but this activity dates back to Eocene and was as young as Miocene. This volcanism included large rhyolitic domes, too. At the southern SMO, the vents of this silicic volcanism are related to graben's master faults and we have named them graben-calderas. Evidences include large pyroclastic dikes and post-ignimbrite aligned rhyolitic domes and lava dikes. All these features were found along the graben-caldera walls or on the graben's shoulders. Some of these vents are related to gold and silver hydrothermal mineralization. In most cases a paleo-lake filled the graben-caldera for a period of time, either during the ignimbrite emplacement or after it. Some of the graben-caldera ignimbrites were deposited in subaqueous environments and post-ignimbrite rhyolitic domes and dikes were intruded in non-consolidated water-saturated tuffs or sedimentary deposits. This lacustrine environment provided the necessary water for the hydrothermal system. The combination of all these factors in space and time, grabens+volcanism+water, resulted in the development of precious-metal hydrothermal ore deposits. Bolaños mine in the Bolaños graben represent our case-study, but we have confirmed the same tectono-volcanic-lake relationship at other mine-districts along the SMO. We conclude that locating the fissural vents of the silicic ignimbrites by means of just geologic mapping is be

  15. ESTUDIO MORFOGENÉTICO DE BAHÍA CALDERA, COSTA RICA

    OpenAIRE

    Saborío, Víctor

    2011-01-01

    La zona de estudio denominada Unidad Caldera, está comprendida en la hoja básica Barranca No. 3.245.I, escala 1:50.000 del IGN, cubriendo un área de 42 km2. Esta caracterizada por una precipitación promedio anual de 1. 600- 2. 000 milímetros; las temperaturas promedios oscilan entre 25- 30º C., lo que determinan un clima cálido seco- húmedo alternado. Los vientos predominantes son los alisios del noreste y de influencia monzónica provenientes del Sur franco y del Suroeste. Las direcciones del...

  16. Can we see the distal dyke communicate with the caldera? Examples of temporal correlation analysis using seismicity from the Bárðarbunga volcano

    Science.gov (United States)

    Jónsdóttir, Kristín; Jónasson, Kristján; Tumi Guðmundsson, Magnús; Hensch, Martin; Hooper, Andrew; Holohan, Eoghan; Sigmundsson, Freysteinn; Halldórsson, Sæmundur Ari; Vogfjörð, Kristín; Roberts, Matthew; Barsotti, Sara; Ófeigsson, Benedikt; Hjörleifsdóttir, Vala; Magnússon, Eyjólfur; Pálsson, Finnur; Parks, Michelle; Dumont, Stephanie; Einarsson, Páll; Guðmundsson, Gunnar

    2016-04-01

    The Bárðarbunga volcano is composed of a large oval caldera (7x11 km) and fissures extending tens of kilometers away from the caldera along the rift zone, which marks the divergent plate boundary across Iceland. On August 16th, 2014 an intense seismic swarm started below the Bárðarbunga caldera and in the two weeks that followed a dyke migrated some 47 km laterally in the uppermost 6-10 km of the crust along the rift. The dyke propagation terminated in lava fields just north of Vatnajökull glacier, where a major (1.5 km3) six months long eruption took place. Intense earthquake activity in the caldera started in the period August 21-24 with over 70 M5 earthquakes accompanying slow caldera collapse, as verified by various geodetic measurements. The subsidence is likely due to magma withdrawal from a reservoir at depth beneath the caldera. During a five months period, October-February, the seismic activity was separated by over 30 km in two clusters; one along the caldera rims (due to piecewise caldera subsidence) and the other at the far end of the dyke (as a result of small shear movements). Here we present statistical analysis comparing the temporal behaviour of seismicity recorded in the two clusters. By comparing the earthquake rate in the dyke in temporal bins before and after caldera subsidence earthquakes to the rate away from these bins (background rate), we show posing a statistical p-value test, that the number of dyke earthquakes was significantly higher (p earthquake (>M4.6) in the caldera. Increased dyke seismicity was also observed 0-3 hours following a large caldera earthquake. Elevated seismicity in the dyke before a large caldera earthquake may occur when a constriction in the dyke was reduced, followed by pressure drop in the chamber. Assuming that the large caldera earthquakes occurred when chamber pressure was lowest, the subsiding caldera piston may have caused temporary higher pressure in the dyke and thereby increased the likelihood of an

  17. Resurgent Toba – field, chronologic, and model constraints on time scales and mechanisms of resurgence at large calderas

    Directory of Open Access Journals (Sweden)

    Shanaka L De Silva

    2015-06-01

    Full Text Available New data reveal details of the post-caldera history at the Earth’s youngest resurgent supervolcano, Toba caldera in Sumatra. Resurgence after the caldera-forming ~74 ka Youngest Toba Tuff eruption uplifted the caldera floor as a resurgent dome, Samosir Island, capped with 100m of lake sediments. 14C age data from the uppermost datable sediments reveal that Samosir Island was submerged beneath lake level (~900m a.s.l ~33.7 ky. Since then, Samosir experienced 700m of uplift as a tilted block dipping to the west. Using 14C ages and elevations of sediment along a transect of Samosir reveal that minimum uplift rates were ~4.9 cm/yr from ~33.7 to 22.5 ka, but diminished to ~0.7 cm/yr after 22.5ka. Thermo-mechanical models informed by these rates reveal that detumescence does not produce the uplift nor the uplift rates estimated for Samosir. However, models calculating the effect of volume change of the magma reservoir within a temperature-dependent viscoelastic host rock reveal that a single pulse of ~475 km3 of magma produces a better fit to the uplift data than a constant flux. Reproducing the uplift rates require more sophisticated models. Motivation for resurgent uplift of the caldera floor is rebound of remnant magma as the system re-established magmastatic and isostatic equilibrium after the caldera collapse. Previous assertions that the caldera floor was apparently at 400m a.s.l or lower requires that uplift must have initiated between sometime between 33.7 ka and 74 ka at a minimum average uplift rate of ~1.1 cm/ year. The change in uplift rate from pre-33.7 ka to immediately post-33.7 ka suggests a role for deep recharge augmenting rebound. Average minimum rates of resurgent uplift at Toba are at least an order of magnitude slower than net rates of restlessness at currently active calderas. This connotes a distinction between resurgence and restlessness controlled by different processes, scales of process, and controlling variables.

  18. Rhyolitic calderas and centers clustered within the active andesitic belt of Ecuador's Eastern Cordillera

    Energy Technology Data Exchange (ETDEWEB)

    Mothes, Patricia A; Hall, Minard L [Instituto Geofisico, Escuela Politecnica Nacional, Quito (Ecuador)], E-mail: pmothes@igepn.edu.ec

    2008-10-01

    In the Ecuadorian volcanic arc a cluster of scattered rhyolitic and dacitic centers within the mainly andesitic Eastern Cordillera includes large caldera structures (Chalupas, Chacana, Cosanga) as well as smaller edifices, built upon the Paleozoic-Mesozoic metamorphic basement. At the Chacana caldera magmatism dates from 2.7 Ma to historic times. These centers erupted enormous ash flows and thick pumice lapilli falls that covered the InterAndean Valley near Quito. The role of the 50-70 km-thick crust with a notable negative gravity anomaly appears to be related to the generation of this highly silicic magmatism occurring along the crest of the Andes in the NVZ.

  19. Thermomechanical controls on magma supply and volcanic deformation: application to Aira caldera, Japan

    Science.gov (United States)

    Hickey, James; Gottsmann, Joachim; Nakamichi, Haruhisa; Iguchi, Masato

    2016-09-01

    Ground deformation often precedes volcanic eruptions, and results from complex interactions between source processes and the thermomechanical behaviour of surrounding rocks. Previous models aiming to constrain source processes were unable to include realistic mechanical and thermal rock properties, and the role of thermomechanical heterogeneity in magma accumulation was unclear. Here we show how spatio-temporal deformation and magma reservoir evolution are fundamentally controlled by three-dimensional thermomechanical heterogeneity. Using the example of continued inflation at Aira caldera, Japan, we demonstrate that magma is accumulating faster than it can be erupted, and the current uplift is approaching the level inferred prior to the violent 1914 Plinian eruption. Magma storage conditions coincide with estimates for the caldera-forming reservoir ~29,000 years ago, and the inferred magma supply rate indicates a ~130-year timeframe to amass enough magma to feed a future 1914-sized eruption. These new inferences are important for eruption forecasting and risk mitigation, and have significant implications for the interpretations of volcanic deformation worldwide.

  20. Magma storage and evolution of the most recent effusive and explosive eruptions from Yellowstone Caldera

    Science.gov (United States)

    Befus, Kenneth S.; Gardner, James E.

    2016-04-01

    Between 70 and 175 ka, over 350 km3 of high-silica rhyolite magma erupted both effusively and explosively from within the Yellowstone Caldera. Phenocrysts in all studied lavas and tuffs are remarkably homogenous at the crystal, eruption, and caldera-scale, and yield QUILF temperatures of 750 ± 25 °C. Phase equilibrium experiments replicate the observed phenocryst assemblage at those temperatures and suggest that the magmas were all stored in the upper crust. Quartz-hosted glass inclusions contain 1.0-2.5 % H2O and 50-600 ppm CO2, but some units are relatively rich in CO2 (300-600 ppm) and some are CO2-poor (50-200 ppm). The CO2-rich magmas were stored at 90-150 MPa and contained a fluid that was 60-75 mol% CO2. CO2-poor magmas were stored at 50-70 MPa, with a more H2O-rich fluid (X_{{{text{CO}}2 }} = 40-60 %). Storage pressures and volatiles do not correlate with eruption age, volume, or style. Trace-element contents in glass inclusions and host matrix glass preserve a systematic evolution produced by crystal fractionation, estimated to range from 36 ± 12 to 52 ± 12 wt%. Because the erupted products contain Yellowstone magmatic system may undergo rapid changes. The variations in depth suggest the magmas were sourced from multiple chambers that follow similar evolutionary paths in the upper crust.

  1. Thermogladius calderae gen. nov., sp. nov., an anaerobic, hyperthermophilic crenarchaeote from a Kamchatka hot spring.

    Science.gov (United States)

    Kochetkova, Tatiana V; Kublanov, Ilya V; Toshchakov, Stepan V; Osburn, Magdalena R; Novikov, Andrei A; Bonch-Osmolovskaya, Elizaveta A; Perevalova, Anna A

    2016-01-21

    An obligately anaerobic, hyperthermophilic, organoheterotrophic archaeon, strain 1633T, was isolated from a terrestrial hot spring of the Uzon Caldera (Kamchatka Peninsula, Russia). Cells were regular cocci, 0.5-0.9 μm in diameter, with one flagellum. The temperature range for growth was 80-95°C, with an optimum at 84°C. Strain 1633T grew on yeast extract, beef extract, peptone, cellulose and cellobiose. No growth was detected on other sugars or carbohydrates, organic acids, or under autotrophic conditions. The only detected growth products were CO2, acetate, and H2. Growth rate was stimulated by elemental sulfur, which was reduced to hydrogen sulfide. In silico calculated G+C content of strain 1633T genomic DNA was 55.64 mol%. 16S rRNA gene sequence analysis placed the strain 1633T together with the non-validly published "Thermogladius shockii" strain WB1 in a separate genus-level cluster within the Desulfurococcaceae family. ANI results revealed 75.72% identity between 1633T and WB1. Based on these results we propose a novel genus and species, for which the name Thermogladius calderae gen. nov., sp. nov. (type strain 1633T=DSM 22663T=VKM B-2946T) is proposed.

  2. Thermomechanical controls on magma supply and volcanic deformation: application to Aira caldera, Japan

    Science.gov (United States)

    Hickey, James; Gottsmann, Joachim; Nakamichi, Haruhisa; Iguchi, Masato

    2016-01-01

    Ground deformation often precedes volcanic eruptions, and results from complex interactions between source processes and the thermomechanical behaviour of surrounding rocks. Previous models aiming to constrain source processes were unable to include realistic mechanical and thermal rock properties, and the role of thermomechanical heterogeneity in magma accumulation was unclear. Here we show how spatio-temporal deformation and magma reservoir evolution are fundamentally controlled by three-dimensional thermomechanical heterogeneity. Using the example of continued inflation at Aira caldera, Japan, we demonstrate that magma is accumulating faster than it can be erupted, and the current uplift is approaching the level inferred prior to the violent 1914 Plinian eruption. Magma storage conditions coincide with estimates for the caldera-forming reservoir ~29,000 years ago, and the inferred magma supply rate indicates a ~130-year timeframe to amass enough magma to feed a future 1914-sized eruption. These new inferences are important for eruption forecasting and risk mitigation, and have significant implications for the interpretations of volcanic deformation worldwide. PMID:27619897

  3. Estudio termodinámico de las reacciones de intercambio en la fabricación de aceros por el proceso de electroescoria

    Directory of Open Access Journals (Sweden)

    Ruiz-Valdepeñas, F.

    1998-05-01

    Full Text Available Microalloyed steels can be manufactured by electroslag remelting provided that a good understanding of the complex thermodynamics in this process is achieved. Slag components, elements dissolved in liquid steel, ferroalloys and deoxidizers play a significant role. Theoretical calculations based on the concept of thermodynamic activity are proposed which describe the oxidation and exchange reactions of the elements with affinity for oxygen. Experimental results are interpreted and it is then possible to propose an overview of the outstanding phenomena which take place. It is therefore possible to adjust the process to the manufacturing of steels with different composition from electrode.

    Para aplicar el proceso de electroescoria a la fabricación de aceros es necesario comprender los complejos procesos termodinámicos que tienen lugar, en los que intervienen los óxidos componentes de la escoria, los aleantes disueltos en el acero líquido y los elementos de las ferroaleaciones y desoxidantes que se adicionan. Calculando las actividades termodinámicas de los elementos en el metal fundido y de los óxidos en la escoria, se plantean los equilibrios teóricos de oxidación de los elementos con mayor afinidad por el oxígeno, así como sus equilibrios de intercambio mutuo. Comparando los equilibrios teóricos con los resultados experimentales se puede interpretar cómo evoluciona el sistema durante la refusión y ajustar la composición de la escoria y demás parámetros para fabricar un acero de composición distinta a la del electrodo.

  4. Bibliography of literature pertaining to Long Valley Caldera and associated volcanic fields

    Science.gov (United States)

    Ewert, John W.; Harpel, Christopher J.; Brooks, Suzanna K.; Marcaida, Mae

    2011-01-01

    On May 25-27, 1980, Long Valley caldera was rocked by four M=6 earthquakes that heralded the onset of a wave of seismic activity within the caldera which has continued through the present. Unrest has taken the form of seismic swarms, uplift of the resurgent dome, and areas of vegetation killed by increased CO2 emissions, all interpreted as resulting from magma injection into different levels beneath the caldera, as well as beneath Mammoth Mountain along the southwest rim of the caldera. Continuing economic development in the Mammoth Lakes area has swelled the local population, increasing the risk to people and property if an eruption were to occur. The U.S. Geological Survey (USGS) has been monitoring geophysical activity in the Long Valley area since the mid-1970s and continues to track the unrest in real time with a sophisticated network of geophysical sensors. Hazards information obtained by this monitoring is provided to local, State, and Federal officials and to the public through the Long Valley Observatory. The Long Valley area also was scientifically important before the onset of current unrest. Lying at the eastern foot of the Sierra Nevada, the deposits from this active volcanic system have provided fertile ground for research into Neogene tectonics, Quaternary geology and geomorphology, regional stratigraphy, and volcanology. In the early 1970s, intensive studies of the area began through the USGS Geothermal Investigations Program, owing to the presence of a large young silicic volcanic system. The paroxysmal eruption of Long Valley caldera about 760,000 years ago produced the Bishop Tuff and associated Bishop ash. The Bishop Tuff is a well-preserved ignimbrite deposit that has continued to provide new and developing insights into the dynamics of ignimbrite-forming eruptions. Another extremely important aspect of the Bishop Tuff is that it is the oldest known normally magnetized unit of the Brunhes Chron. Thus, the age of the Bishop Tuff is used to

  5. Geology of the Mid-Miocene Rooster Comb Caldera and Lake Owyhee Volcanic Field, eastern Oregon: Silicic volcanism associated with Grande Ronde flood basalt

    Science.gov (United States)

    Benson, Thomas R.; Mahood, Gail A.

    2016-01-01

    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

  6. Ballistic blocks around Kīlauea Caldera: Their vent locations and number of eruptions in the late 18th century

    Science.gov (United States)

    Swanson, Donald A.; Zolkos, Scott P.; Haravitch, Ben

    2012-01-01

    Thousands of ballistic blocks occur around Kīlauea Caldera and record part of the latest major period of explosive activity on the volcano, in late 1790 or within a few years thereafter. The sizes of the blocks – the largest of which is more than 2 m in nominal diameter – and differences in rock types allow the definition of at least 6 dispersal lobes of mostly undetermined relative age. The orientations of the lobes help approximate the locations of vents or explosion sources on the floor of the caldera, now deeply buried by younger lava flows. The vents may have been distributed northward for about 2 km from near the site of the modern Halema'uma'u Crater and were apparently confined to the western half of the caldera. The blocks are entirely lithic except for those in one dispersal lobe, which contains cored bombs and blocks as well as juvenile lapilli. Eruption parameters calculated from EJECT! suggest that the phreatic and phreatomagmatic explosions could have been generated at the water table, about 600 m below the high point on the caldera rim.

  7. Quantifying volcanic hazard at Campi Flegrei caldera (Italy) with uncertainty assessment: 2. Pyroclastic density current invasion maps

    Science.gov (United States)

    Neri, Augusto; Bevilacqua, Andrea; Esposti Ongaro, Tomaso; Isaia, Roberto; Aspinall, Willy P.; Bisson, Marina; Flandoli, Franco; Baxter, Peter J.; Bertagnini, Antonella; Iannuzzi, Enrico; Orsucci, Simone; Pistolesi, Marco; Rosi, Mauro; Vitale, Stefano

    2015-04-01

    Campi Flegrei (CF) is an example of an active caldera containing densely populated settlements at very high risk of pyroclastic density currents (PDCs). We present here an innovative method for assessing background spatial PDC hazard in a caldera setting with probabilistic invasion maps conditional on the occurrence of an explosive event. The method encompasses the probabilistic assessment of potential vent opening positions, derived in the companion paper, combined with inferences about the spatial density distribution of PDC invasion areas from a simplified flow model, informed by reconstruction of deposits from eruptions in the last 15 ka. The flow model describes the PDC kinematics and accounts for main effects of topography on flow propagation. Structured expert elicitation is used to incorporate certain sources of epistemic uncertainty, and a Monte Carlo approach is adopted to produce a set of probabilistic hazard maps for the whole CF area. Our findings show that, in case of eruption, almost the entire caldera is exposed to invasion with a mean probability of at least 5%, with peaks greater than 50% in some central areas. Some areas outside the caldera are also exposed to this danger, with mean probabilities of invasion of the order of 5-10%. Our analysis suggests that these probability estimates have location-specific uncertainties which can be substantial. The results prove to be robust with respect to alternative elicitation models and allow the influence on hazard mapping of different sources of uncertainty, and of theoretical and numerical assumptions, to be quantified.

  8. Volcanic flood simulation of magma effusion using FLO-2D for drainage of a caldera lake at the Mt. Baekdusan

    Science.gov (United States)

    Lee, Khil-Ha; Kim, Sung-Wook; Kim, Sang-Hyun

    2014-05-01

    Many volcanic craters and calderas are filled with large amounts of water that can pose significant flood hazards to downstream communities due to their high elevation and the potential for catastrophic releases of water. Recent reports pointed out the Baekdusan volcano that is located between the border of China and North Korea as a potential active volcano. Since Millennium Eruption around 1000 AD, smaller eruptions have occurred at roughly 100-year intervals, with the last one in 1903. Sudden release of huge volume of water stored in temporarily elevated caldera lakes are a recurrent feature of volcanic environments, due to the case with which outlet channels are blocked by and re-cut through, unwelded pyroclastic deposits. The volcano is showing signs of waking from a century-long slumber recently. Volcanic floods, including breakouts from volcanic lakes, can affect communities beyond the areas immediately affected by a volcanic eruption and cause significant hydrological hazards because floods from lake-filled calderas may be particularly large and high. Although a number of case studies have been presented in the literature, investigation of the underlying physical processes is required as well as a method for interpreting the process of the rapid release of water stored in a caldera lake. The development of various forecasting techniques to prevent and minimize economic and social damage is in urgent need. This study focuses on constructing a flood hazard map triggered by the magma effusion in the Baekdusan volcano. A physically-based uplift model was developed to compute the amount of water and time to peak flow. The ordinary differential equation was numerically solved using the finite difference method and Newton-Raphson iteration method was used to solve nonlinear equation. The magma effusion rate into the caldera lake is followed by examples at other volcanic activities. As a result, the hydrograph serves as an upper boundary condition when hydrodynamic

  9. AUV Mapping of Axial Seamount, Juan de Fuca Ridge: The Southern Caldera Floor and Upper South Rift

    Science.gov (United States)

    Clague, D. A.; Caress, D.; Paduan, J. B.; Chadwick, W. W.; Butterfield, D. A.; Thomas, H.; Conlin, D.; Thompson, D. R.

    2007-12-01

    During September 2006 and August 2007 NOAA NeMO cruises, we conducted 7 high-resolution near-bottom seafloor mapping surveys of Axial Seamount using the MBARI Mapping AUV D. Allan B. The 200 kHz multibeam and 110 kHz sidescan surveys of the south caldera and upper south rift, conducted at 50 m vehicle altitude, achieved sub-meter resolution bathymetry and sidescan imagery. Numerous previous and concurrent submersible or ROV dives provide ground-truth of what the maps depict. A companion poster presents the AUV surveys of the north caldera and northeastern caldera rim. The southern caldera wall is buried beneath at least 5 voluminous lava flows, including the 1998 flow, each erupted from fissures extending along the southeastern edge of the caldera roughly parallel to the upper south rift zone. The caldera wall here was not as tall as on the southwest, north, and northeast of the caldera, and may have been as low as 35 m tall before it was buried. Active and inactive hydrothermal vents are generally located along the inferred buried caldera wall. Eruptive fissures are characterized by series of depressions aligned along each fissure; no ramparts or other constructional edifices were constructed along them. The aligned depressions suggest that lava drained back down the fissures at the end of the eruptions. The fissure eruptions were large volume and had large effusion rates as seen by their interwoven channels and the extent of the flows. Most of these flows have central channels of lineated sheet flows, bordered by folded and then jumbled sheet flows, surrounded by lobate flows with lava pillars and collapse structures and pillowed flow margins. As an example, the 1998 eruption in and near the caldera issued from 5 en echelon fissures extending at least 3 km. The largest flow lobe extending to the south was mapped along its entire western boundary using JASON II, but the flow extends to the southeast beyond the mapped region. An unusual km-across feature was mapped

  10. Dynamics and pre-eruptive conditions of catastrophic, ignimbrite-producing eruptions from the Yenkahe Caldera, Vanuatu

    Science.gov (United States)

    Firth, Chris W.; Cronin, Shane J.; Turner, Simon P.; Handley, Heather K.; Gaildry, Clement; Smith, Ian

    2015-12-01

    A combined stratigraphic and geochemical examination of ~ 43 kyr of volcanic activity is presented for the Yenkahe Caldera, a mafic-intermediate volcanic system on the island of Tanna, in the Vanuatu Arc. Through this period two catastrophic ignimbrite-producing eruptions have occurred: the Siwi eruption and the older, Old Tanna Ignimbrite eruption. The latter was previously linked with a different edifice to the north-east, however re-examination has shown it was derived from the Yenkahe Caldera. Radiocarbon dating of this ignimbrite gives an age of ~ 43 kyr B.P. Both eruptions produced voluminous ignimbrite sheets, however differences in deposit sequences show that the eruptions followed distinct courses. Deposits from the more recent Siwi eruption display greater evidence for phreatomagmatic phases during eruption onset. Both ignimbrites are distributed asymmetrically about the caldera, indicating partial collapse in each case. The early stages of the Siwi eruption produced directed pyroclastic surges and spatter fountains. Between these two major eruptions, volcanic activity was maintained through the formation of small, discrete volcanic cones, such as Yasur, which is active today. Whole rock major and trace element data show that intra-caldera activity between cataclysmic eruptions produced magmas of uniform basaltic-trachy-andesitic composition (SiO2 ~ 56 wt.%). Minerals within these lavas appear to be in equilibrium with their host. The Siwi eruption produced the most evolved, trachy-andesitic magma (SiO2 > 58 wt.%), while the Old Tanna eruption is associated with less evolved, basaltic-andesite magma (SiO2 ~ 53 wt.%). Juvenile clasts from both ignimbrites display diverse mineral chemistry and mineral disequilibrium textures. From these variations in geochemistry and petrology we suggest that a crystal mush or resident magma remained following low-magnitude, intra-caldera activity. MELTS modelling suggest that this was stored at shallow depths, equivalent

  11. Caldera resurgence: new insights from the study of the Siwi-Yenkahe-Yasur system (Vanuatu)

    Science.gov (United States)

    Brothelande, E.; Lenat, J.; Merle, O.; Peltier, A.

    2013-12-01

    On Tanna Island (Vanuatu), the Siwi caldera hosts a complex association between a permanently active explosive volcano (Yasur) and one of the fastest growing resurgent dome on Earth (Yenkahe). Uplifted coral terraces and marine tuff indicate a very high resurgence rate over the past 1000 yrs (15.6 cm.yr-1) making the Yenkahe dome one of the most relevant example of active post-caldera resurgence, but also one of the most dangerous structure of that kind. New data acquired between 2008 and 2012 brought further constraints on resurgent processes involved. Tectonic patterns inferred from structural observations on satellite images and on the field, completed by a meticulous photogrammetry study, argue for a relatively extended and shallow source of deformation. Two different approaches, using analogue and numerical modeling, were developed to explore the doming effects of different sources within the first kilometers. These models provide the first quantitative estimations on the depth and the shape of the source (magmatic and/or hydrothermal) that generated the Yenkahe dome. Analysis of external surface features, such as faults patterns and collapse scars revealed by photogrammetry and field observations, also provided new data for proposing hypotheses of a multi-step construction of the Yenkahe and discussing the potential instabilities of the dome, notably on the shore-bordering eastern flank. Geophysical investigations, combining electrical methods (T.D.E.M., E.R.T., S.P.), gravimetry and magnetism, were performed providing a wide range of information in terms of internal structure. Lithology units can be distinguished at different scales, and tectonic features connected to the surface can be defined. Conductive bodies representing the hydrothermal system can be located in relationship with these features, broaching the question of a possible phreatic or phreato-magmatic activity in the future. The combination of a wide panel of methods brings here a new image on

  12. Using StaMPS to process RADARSAT images of Askja caldera

    Science.gov (United States)

    de Zeeuw-van Dalfsen, E.; Hooper, A. J.; Sigmundsson, F.; Pedersen, R.; Jaupart, C. P.

    2009-12-01

    We have used RADARSAT SLC images from the Canadian Space Agency to create complex interferograms from part of the northern volcanic zone in Iceland. The dataset covers the 2000-2009 period and is a valuable addition to the limited number of good interferometric image pairs available for the area during this time, due to problems with the ERS in 2000 and limited other coverage for part of the period. Here, the Stanford Method for Persistent Scatterers (StaMPS) has been applied to RADARSAT data for the first time. This has enhanced the quality of the interferograms with respect to earlier processing using the Doris software package developed by the Delft Institute for Earth-Oriented Space Research (DEOS), Delft University of Technology. The StaMPS software was adapted for general use with RADARSAT data. Of our particular interest is the Askja caldera and its surroundings which are covered by the images. The Askja caldera has been gradually deflating since 1983 and InSAR images provide an excellent tool to monitor this deformation. In the last two years, previously undetected activity has been observed in the area. Since 2006 small magnitude lower-crustal earthquake swarms have been detected around the Askja caldera (Soosalu et al., 2009). Furthermore, 20 km to the east of Askja in the vicinity of the Upptyppingar mountain, intense persistent deep-seated seismic activity has been recorded since the beginning of 2007 (Jakobsdóttir et al. 2008). Both of these observations, even though very different in character, suggest magma movement at deep levels. The events may relate to recharging of the volcanic systems in the area, or alternatively to flow of magma away from the central part of the Askja system. Detailed monitoring of the area is therefore important. The time series of RADARSAT interferograms shows that Askja continues to subside into summer 2009, but further analysis can test if the rate of subsidence has slowed down in relation to the unrest in the area. We

  13. Storage and eruption of large volumes of rhyolite lava: Example from Solfatara Plateau, Yellowstone Caldera

    Science.gov (United States)

    Befus, K.; Gardner, J. E.; Zinke, R.

    2010-12-01

    The cataclysmic volcanic history of Yellowstone caldera has been extensively documented in both popular media and scholarly journals. High-silica magmas should erupt explosively because of their high viscosity and volatile content; however, numerous passively-erupted, large-volume rhyolite lava flows have also erupted from Yellowstone caldera. We use petrologic observations of one such flow, the Solfatara Plateau obsidian lava, to provide insights into the eruptive dynamics and pre-eruptive magmatic conditions of large-volume rhyolite lava. Solfatara Plateau, a 7 km3 high-silica rhyolite lava that extends 4-15 km from vent, erupted 103±8 ka within the Yellowstone caldera1. Quartz and sanidine are the dominant phenocrysts, with crystal contents of 5-10% throughout. FTIR analyses of glass inclusions in quartz and sanidine phenocrysts indicate that pre-eruptive dissolved volatile contents were up to 3.0 wt. % H2O and 250 ppm CO2. Myrmekite blebs partially envelop quartz and sanidine phenocrysts in all samples from along the margins of the flow (up to 3 km from flow front). Sanidines in samples from near vent are unzoned at Or49±2. Those at the flow front have similar cores, but rims are more sodic (Or44±6). Alkali feldspars in myrmekite range from Or27 to Or50. Petrologic observations, such as heavily embayed quartz phenocrysts and dissolution of myrmekite indicate disequilibrium within the system, likely as a result of significant heating that caused portions of the magma body to go from near-solidus to near-liquidus conditions prior to erupting. When it did erupt, volatile loss during eruptive ascent led to undercooling and significant microlite crystallization of Fe-Ti oxide and clinopyroxene microlites. Fe-Ti microlites occur as roughly equidimensional crystals, 1-10 µm across, as well as high-aspect-ratio needles, 3-60 µm long. Clinopyroxene microlites occur primarily as individual prismatic crystals, but also occur as linked, curved chains or as overgrowths

  14. Propuesta, diseño y adaptación de un sistema de intercambio de cabinas para un simulador de helicóptero EC 145 T2

    OpenAIRE

    2014-01-01

    En este proyecto se plantea una propuesta de un sistema de intercambio de cabina para un simulador de vuelo de helicóptero civil. Se trata de una parte del proyecto “Simulador de Vuelo de Helicóptero EC 145 T2 D” que engloba todos los sistemas que conforman el simulador. Para una mejor comprensión de los términos empleados a lo largo del proyecto se comenzará dando una visión general de lo que es un simulador de vuelo, dando a conocer sus antecedentes históricos, el aspecto actual y los...

  15. Nuevas perspectivas de las políticas académicas en Europa y en el mundo: participación e intercambio universitario en el espacio europeo de educación superior

    OpenAIRE

    Bartolomé Cenzano, José Carlos De

    2014-01-01

    Esta revista provee acceso libre inmediato a su contenido bajo el principio de que hacer disponible gratuitamente investigación al publico apoya a un mayor intercambio de conocimiento global El presente trabajo aborda el cambio de paradigma en las relaciones interuniversitarias, mediante la creación de un Espacio Europeo de Educación Superior, nacido en el seno de la Declaración de Bolonia. Esta investigación en clave constitucional y en el ámbito de las relaciones internaciona...

  16. Decoloración y regeneración de resinas de intercambio iónico utilizadas en el refino de caña de azúcar: optimización y modelado

    OpenAIRE

    2016-01-01

    Este Trabajo Fin de Master aborda el estudio experimental a escala piloto-laboratorio de la etapa de regeneración de resinas de intercambio iónico cargadas con colorantes procedentes de la etapa de decoloración del refino de caña de azúcar, con el objetivo de encontrar las condiciones óptimas de regeneración. Los resultados demostraron una relación entre la carga de colorantes y el tiempo de regeneración, de forma que cuando se opera con altas cargas de color, sería recomendable alargar el ti...

  17. Impacto de la maniobra de inspiración profunda en el intercambio gaseoso del sujeto con obesidad severa e hipertensión arterial pulmonar asociada a síndrome de Eisenmenger

    OpenAIRE

    Santos-Martínez,Luis-Efren; Martínez-Guerra,María-Luisa; Bautista, Edgar; Castillo, Francisco; Castañón,Alicia; Pulido,Tomás; Hernández,José-Luis; Sandoval,Julio

    2008-01-01

    La obesidad y el síndrome de Eisenmenger son entidades ampliamente estudiadas. Sin embargo, su asociación es inusual y no informada. Ambas cursan con alteraciones del intercambio gaseoso de grado variable. En la obesidad severa son atribuidas a trastornos en la relación ventilación/perfusión y al cortocircuito venoarterial pulmonar que dependen del volumen pulmonar. En el síndrome de Eisenmenger con obesidad severa, esta dependencia se desconoce. Material y métodos: Se estudiaron 28 sujetos o...

  18. Identidad, intercambio y aventura en el Alto Neuquén IDENTITY, TRADE, AND ADVENTURE IN THE ALTO NEUQUÉN

    Directory of Open Access Journals (Sweden)

    Rolando Silla

    2009-12-01

    Full Text Available Pretendemos analizar cómo son considerados los denominados chilenos que habitan el lado occidental de los Andes por los grupos denominados crianceros (pastores trashumantes que habitan una serie de localidades y parajes rurales del Alto Neuquén, patagonia argentina. Veremos que en el sistema clasificatorio y autoclasi- ficatorio de estos grupos opera el principio de los indiscernibles: las categorías adscriptivas se multiplican sin solución de continuidad. Se manifiesta así una superposición y continuidad de identidades más que oposiciones entre el argentino, el chileno, el mapuche, etc. Esto es lo que observamos cuando empezamos a analizar las categorías de adscripción en acto y no como modelo. Nos proponemos señalar cómo esta ambigüedad y superposición de identidades se hace también manifiesto en valoraciones ambiguas y superpuestas respecto a cómo los crianceros argentinos valoran moralmente a los crianceros chilenos. Para ello analizaré ciertas situaciones de intercambio que se caracterizan por ser poco claras, tales como el comercio, el robo y el contrabando de ganado que ocurre a ambos lados de la frontera internacional.This article examines how Chileans living in the Western Andes are thought of by the crianceros (transhumanance shepherds who live in the Alto Neuquén, (Argentinean Patagonian. It is observed that the principle of indiscernible operates in the classificatory and self-classificatory systems of these groups: the ascriptive categories cannot be discerned or distinguished from one another and multiply ad infinitum. A superposition and continuity of identities is manifested rather than an opposition between Argentineans, Chileans, Mapuche, and so on. These forms appear when ascriptive categories are analyzed in action rather than in models. It is shown that such ambiguity and superposition of identities is also made manifest in ambiguous and superposed moral judgments of Chilean shepherds by Argentinean

  19. Don y Dendê: los sistemas de intercambio de los grupos de capoeira en Madrid a partir de Marcel Mauss

    Directory of Open Access Journals (Sweden)

    Menara Lube Guizardi

    2014-12-01

    Full Text Available Resumen: Identificamos en las asociaciones de capoeira brasileña estudiadas en Madrid un sistema de prestaciones totales vinculado al imperativo de la circulación de una fuerza inmaterial, un tipo de mana que los capoeiristas denominan “Dendê”, “Axé” o “Energía”. El presente ensayo utiliza el “Ensayo sobre los dones” de Marcel Mauss para analizar cómo la aceptación de este mana de la capoeira involucra a los capoeiristas en un círculo recíproco de intercambios: la “energía” recibida en la rueda debe ser devuelta, pues la no devolución implica poner en riesgo la integridad física, espiritual y psicológica del individuo.Palabras-clave: Sistema de prestaciones totales; incorporación; capoeira; corporalidad; ritos. Resumo: Identificamos, nas associações de capoeira estudadas em Madri, um sistema de prestações totais vinculado ao imperativo da circulação de uma força imaterial, um tipo de mana que os capoeiristas denominam “Dendê”, “Axé” o “Energia”. O presente ensaio utiliza o “Ensaio sobre a dádiva” de Marcel Mauss para analisar como a aceitação deste mana da capoeira envolve aos capoeiristas num círculo recíproco de intercâmbios: a “energia” recebida na roda deve ser devolvida , pois a não devolução implica colocar em risco a integridade física, espiritual e psicológica do individuo.Palavras-chave: Sistema de prestações totais; incorporação; capoeira; corporalidade; ritos. Abstract: The Brazilian capoeira associations I studied in Madrid organized their collective exchanges through a system of total prestations connected to the movement of an immaterial power: a kind of mana that the capoeira players called "Dendê", "Axé" or "Energia". This essay explores how the acceptance of this  “mana” engages the capoeira players in a circuit of reciprocal exchanges: the "energy" received at the roda must be returned, since the lack of reciprocity put in danger the physical

  20. Re-pensando el orden colonial: los intercambios hispano-indígenas en el fuerte del río Negro

    Directory of Open Access Journals (Sweden)

    María Teresa Luiz

    2005-01-01

    un conjunto de transacciones que definieron un particular régimen de intercambios basado en la reciprocidad. Estas prácticas de naturaleza política y económica favorecieron el mantenimiento de cierto equilibrio de fuerzas que se trasunta en la disminución de la conflictividad fronteriza durante las últimas décadas del período colonial.

  1. Workshop on hydrologic and geochemical monitoring in the Long Valley Caldera: proceedings

    Energy Technology Data Exchange (ETDEWEB)

    Sorey, M.L.; Farrar, C.D.; Wollenberg, H.A.

    1984-10-01

    A workshop reviewed the results of hydrologic and geochemical monitoring in the Long Valley caldera. Such monitoring is being done to detect changes in the hydrothermal system induced by ongoing magmatic and tectonic processes. Workshop participants discussed the need to instrument sites for continuous measurements of several parameters and to obtain additional hydrologic and chemical information from intermediate and deep drill holes. In addition to seismic and deformation monitoring, programs are currently in progress to monitor changes in the discharge characteristics of hot springs, fumaroles, and soil gases, as well as pressures and temperatures in wells. Some hydrochemical parameters are measured continuously, others are measured monthly or at longer intervals. This report summarizes the information presented at the hydrologic monitoring workshop, following the workshop agenda which was divided into four sessions: (1) overview of the hydrothermal system; (2) monitoring springs, fumaroles, and wells; (3) monitoring gas emissions; and (4) conclusions and recommendations.

  2. PRESENT STATE OF THE HYDROTHERMAL SYSTEM IN LONG VALLEY CALDERA, CALIFORNIA.

    Science.gov (United States)

    Sorey, Michael L.

    1985-01-01

    Results of test drilling to depths of 2 km and data on the chemical and isotopic content of waters from hot springs and fumaroles permit a conceptual model of the present-day hydrothermal system in Long Valley caldera to be delineated. The model consists of two principal zones in which hot water flows laterally from west to east at depths less than 1 km within and around the resurgent dome. Maximum measured temperatures within these zones are near 170 degree C, but estimates from chemical geothermometers and extrapolation of a high temperature gradient measured in a recent drill hole indicate that a source reservoir at temperatures near 240 degree C may exist at greater depths in the Bishop Tuff beneath the west moat.

  3. Rock physics of fibrous rocks akin to Roman concrete explains uplifts at Campi Flegrei Caldera

    Science.gov (United States)

    Vanorio, Tiziana; Kanitpanyacharoen, Waruntorn

    2015-08-01

    Uplifts in the Campi Flegrei caldera reach values unsurpassed anywhere in the world (~2 meters). Despite the marked deformation, the release of strain appears delayed. The rock physics analysis of well cores highlights the presence of two horizons, above and below the seismogenic area, underlying a coupled process. The basement is a calc-silicate rock housing hydrothermal decarbonation reactions, which provide lime-rich fluids. The caprock above the seismogenic area has a pozzolanic composition and a fibril-rich matrix that results from lime-pozzolanic reactions. These findings provide evidence for a natural process reflecting that characterizing the cementitious pastes in modern and Roman concrete. The formation of fibrous minerals by intertwining filaments confers shear and tensile strength to the caprock, contributing to its ductility and increased resistance to fracture.

  4. SELECTED CHEMICAL ANALYSES AND GEOTHERMOMETRY OF HOT SPRING WATERS FROM THE CALABOZOS CALDERA, CENTRAL CHILE.

    Science.gov (United States)

    Thompson, J.M.; Grunder, A.L.; Hildreth, Wes

    1983-01-01

    Hot springs discharging from the active hydrothermal system associated with the Calabozos caldera, Chile, have measured orifice temperatures as high as 98. 5 degree C and calculated geothermometer temperatures as high as 250 degree C. Three types of spring waters can be identified from the chemical analyses: a Na-Cl type, a Na-HCO//3 type and a Na-mixed anion type. Chloride-enthalpy relations indicate that the hydrothermal reservoir water may attain temperatures near 342 degree C and that most spring waters are mixed with cold meteoric water. Despite the proximity of Mesozoic marine gypsum deposits, the Cl/Br weight ratio of the Calabozos spring waters does not appear to indicate that these waters have a significant 'marine' signature. Refs.

  5. Isotopic and trace element characteristics of rhyolites from the Valles Caldera, New Mexico. Final technical report

    Energy Technology Data Exchange (ETDEWEB)

    Self, S.; Sykes, M.L. [Hawaii Univ., Honolulu, HI (United States). Dept. of Geology and Geophysics; Wolff, J.A. [Texas Univ., Arlington, TX (United States). Dept. of Geology; Skuba, C.E. [McMaster Univ., Hamilton, ON (Canada). Dept. of Geology

    1991-09-01

    This report is a summary of work supported by DOE grant No. DE-FGO5-87ER13795 that was completed or is still in progress. The stated purpose of this grant was to collect geochemical information (trace element, radiogenic isotope and stable oxygen and hydrogen isotope) on samples from core holes VC-I and VC-2a in the Valles caldera in order to establish a consistent detailed intracaldera stratigraphy and relate this to extracaldera volcanic rock units of the Jemez Mountains. Careful stratigraphic control of the intracaldera units is necessary to evaluate models of caldera formation, ignimbrite deposition, and resurgence. Combined stable and radiogenic isotope and trace element data will also provide major insights to petrogenesis of the Bandelier magma system. The composition of non-hydrothermally altered samples from outflow units of the Bandelier Tuff and related volcanics must be known to assess isotopic variations of intracaldera ignimbrite samples. On detailed examination of the VC-2a core samples, it became apparent that hydrothermal alteration is so extensive that no geochemical information useful for stratigraphic fingerprinting or petrogenesis could be obtained, and that correlation with other intracaldera units and extracaldera units must be made on the basis of stratigraphic position and gross lithologic characteristics. Accordingly, we emphasize geochemical data from the extracaldera Bandelier Tuffs and related units which will be useful for comparison with proposed drill hole VC-4 and for any future studies of the region. The stable isotope, radiogenic isotope and trace element data obtained from this project, combined with existing major and trace element data for volcanic rocks from this area, provide an extensive data base essential to future Continental Scientific Drilling Program projects in the Jemez Mountains of New Mexico.

  6. New constraints on mechanisms of remotely triggered seismicity at Long Valley Caldera

    Science.gov (United States)

    Brodsky, E.E.; Prejean, S.G.

    2005-01-01

    Regional-scale triggering of local earthquakes in the crust by seismic waves from distant main shocks has now been robustly documented for over a decade. Some of the most thoroughly recorded examples of repeated triggering of a single site from multiple, large earthquakes are measured in geothermal fields of the western United States like Long Valley Caldera. As one of the few natural cases where the causality of an earthquake sequence is apparent, triggering provides fundamental constraints on the failure processes in earthquakes. We show here that the observed triggering by seismic waves is inconsistent with any mechanism that depends on cumulative shaking as measured by integrated energy density. We also present evidence for a frequency-dependent triggering threshold. On the basis of the seismic records of 12 regional and teleseismic events recorded at Long Valley Caldera, long-period waves (>30 s) are more effective at generating local seismicity than short-period waves of comparable amplitude. If the properties of the system are stationary over time, the failure threshold for long-period waves is ~0.05 cm/s vertical shaking. Assuming a phase velocity of 3.5 km/s and an elastic modulus of 3.5 x 1010Pa, the threshold in terms of stress is 5 kPa. The frequency dependence is due in part to the attenuation of the surface waves with depth. Fluid flow through a porous medium can produce the rest of the observed frequency dependence of the threshold. If the threshold is not stationary with time, pore pressures that are >99.5% of lithostatic and vary over time by a factor of 4 could explain the observations with no frequency dependence of the triggering threshold. Copyright 2005 by the American Geophysical Union.

  7. Abrupt transition from fractional crystallization to magma mixing at Gorely volcano (Kamchatka) after caldera collapse

    Science.gov (United States)

    Gavrilenko, Maxim; Ozerov, Alexey; Kyle, Philip R.; Carr, Michael J.; Nikulin, Alex; Vidito, Christopher; Danyushevsky, Leonid

    2016-07-01

    A series of large caldera-forming eruptions (361-38 ka) transformed Gorely volcano, southern Kamchatka Peninsula, from a shield-type system dominated by fractional crystallization processes to a composite volcanic center, exhibiting geochemical evidence of magma mixing. Old Gorely, an early shield volcano (700-361 ka), was followed by Young Gorely eruptions. Calc-alkaline high magnesium basalt to rhyolite lavas have been erupted from Gorely volcano since the Pleistocene. Fractional crystallization dominated evolution of the Old Gorely magmas, whereas magma mixing is more prominent in the Young Gorely eruptive products. The role of recharge-evacuation processes in Gorely magma evolution is negligible (a closed magmatic system); however, crustal rock assimilation plays a significant role for the evolved magmas. Most Gorely magmas differentiate in a shallow magmatic system at pressures up to 300 MPa, ˜3 wt% H2O, and oxygen fugacity of ˜QFM + 1.5 log units. Magma temperatures of 1123-1218 °C were measured using aluminum distribution between olivine and spinel in Old and Young Gorely basalts. The crystallization sequence of major minerals for Old Gorely was as follows: olivine and spinel (Ol + Sp) for mafic compositions (more than 5 wt% of MgO); clinopyroxene and plagioclase crystallized at ˜5 wt% of MgO (Ol + Cpx + Plag) and magnetite at ˜3.5 wt% of MgO (Ol + Cpx + Plag + Mt). We show that the shallow magma chamber evolution of Old Gorely occurs under conditions of decompression and degassing. We find that the caldera-forming eruption(s) modified the magma plumbing geometry. This led to a change in the dominant magma evolution process from fractional crystallization to magma mixing. We further suggest that disruption of the magma chamber and accompanying change in differentiation process have the potential to transform a shield volcanic system to that of composite cone on a global scale.

  8. Fiber-Reinforced Rocks Akin to Roman Concrete Help Explain Ground Deformation at Campi Flegrei Caldera

    Science.gov (United States)

    Vanorio, Tiziana; Kanitpanyacharoen, Waruntorn

    2016-04-01

    The caldera of Campi Flegrei is one of the active hydrothermal systems of the Mediterranean region experiencing notable unrest episodes in a densely populated area. During the last crisis of 1982-1984, nearly 40,000 people were evacuated for almost two years from the main town of Pozzuoli, the Roman Puteoli, due to the large uplifts (~2 m over two years) and the persistent seismic activity. The evacuation severely hampered the economy and the social make-up of the community, which included the relocation of schools and commercial shops as well as the harbor being rendered useless for docking. Despite the large uplifts, the release of strain appears delayed. Seismicity begins and reaches a magnitude of 4.0 only upon relatively large uplifts (~ 70-80 cm) contrary to what is generally observed for calderas exhibiting much lower deformation levels. Over and above the specific mechanism causing the unrest and the lack of identification of a shallow magmatic reservoir (concrete. The formation of fibrous minerals by intertwining filaments confers shear and tensile strength to the caprock, contributing to its ductility and increased resistance to fracture. The importance of the findings reported in this study lies not only on the fibrous and compositionally nature of the caprock but also on its possible physicochemical deterioration. Given the P-T-XCO2 conditions regulating the decarbonation reactions, the influx of new fluids into the Campi Flegrei system lowers the temperature of the decarbonation reaction and dilutes the existing CO2, thus triggering additional CO2, methane, and steam to form. As these gases rise toward the surface, the natural cement layer halts them, leading to pore pressure increase and subsequent ground deformations.

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

    Directory of Open Access Journals (Sweden)

    Heryadi Rachmat

    2016-08-01

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

  10. Editorial: el intercambio profesional panamericano

    OpenAIRE

    2011-01-01

    El Presidente de Chile, excelentísimo señor Juan Antonio Ríos "en cada colombiano ha visto un chileno" y el embajador de México decía: "Los pueblos americanos se aman mucho pero se conocen poco."

  11. Alteration in the Madera limestone and Sandia formation from core hole VC-1 Valles Caldera, New Mexico

    Science.gov (United States)

    Keith, Terry E. C.

    1988-06-01

    Core hole VC-1 penetrated the southwestern ring fracture zone of the 1.1 Ma Valles caldera and at a depth of 333 m intersected the top of the Paleozoic section including the Abo Formation, Madera Limestone, and Sandia Formation, reaching a total depth of 856 m. The Paleozoic rocks, which consist of thin-bedded limestone, siltstone, mudstone, sandstone, and local conglomerate, are overlain by volcanic rocks of the caldera moat that are less than 0.6 Ma. Diagenetic and at least three hydrothermal alteration stages were identified in the Madera Limestone and Sandia Formation. Diagenetic clay alteration was pervasive throughout the sedimentary rocks. Volcanic activity at 16.5 Ma and continuing through the formation of the Valles caldera resulted in high thermal gradients, which caused recrystallization of diagenetic clay minerals. Interstratified smectite-illite is the most diagnostic clay mineral throughout the section; structurally, the illite component in the ordered interstratified illite-smectite changes gradationally from 70% at the top of the Madera Limestone to 95% at the base of the section in the Sandia Formation. Pyrite that occurs as small clots and lenses as well as finely disseminated is interpreted as being of diagenetic origin, especially in organic-rich beds. Low permeability of much of the Paleozoic section precluded the deposition of hydrothermal minerals except in fractures and intergranular space in some of the more permeable sandstone and brecciated horizons. Three stages of hydrothermal mineral deposition are defined. Stage I is widespread and includes mainly chlorite, calcite, pyrite, and interstratified smectite-illite that was formed prior to caldera development at temperatures approximating 200°C. Stage II is characterized by quartz, sericite, and scarce sulfides deposited locally by fluids at approximately 275°C shortly before or at the time of early caldera-related volcanism. The Stage III hydrothermal event, associated with formation of

  12. 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: guzmansilvina@gmail.com

    2008-10-01

    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.

  13. Remoción de níquel, cadmio y zinc del agua, utilizando clinoptilolita heulandita

    Directory of Open Access Journals (Sweden)

    Thelma B. Pavón Silva

    2000-01-01

    Full Text Available Se aplica el proceso de intercambio iónico con una zeolita natural obtenida en Taxco, Guerrero, México, para la remoción de Zn, Cd y Ni de soluciones acuosas. Para este proceso, el mineral se homoionizó con cloruro de sodio y posteriormente se puso en contacto con soluciones 0.01 N de sales de nitratos de Zn, Cd y Ni, durante 8 días.

  14. Eficiencia en la prescripción de medicamentos: impacto de un programa de intercambio terapéutico The efficiency of drug prescription: impact of a therapeutic exchange program

    Directory of Open Access Journals (Sweden)

    Isabel Rosich

    2012-02-01

    Full Text Available Objetivo: Evaluar el impacto de un programa de intercambio terapéutico a omeprazol de los inhibidores de la bomba de protones (IBP. Método: Ensayo comunitario que compara el impacto de un programa de intercambio terapéutico en los equipos de atención primaria de una comarca respecto a la no aplicación en una comarca control. Se incluyó a los pacientes con prescripción de un IBP entre mayo de 2008 y junio de 2009. La intervención consistió en sesiones educativas y facilitar a cada médico (n=68 los pacientes con un IBP que pudiera cambiarse a omeprazol. Se obtuvo información de la historia clínica (IBP prescrito, equipo de atención primaria y de la aplicación de farmacia (coste de la dosis diaria definida de los IBP. A partir del riesgo relativo (RR se comparó el porcentaje de intercambio terapéutico en cada comarca antes y después de la intervención. También se calculó el porcentaje de omeprazol al final de cada periodo de estudio y los cambios en los costes en IBP. Resultados: Hubo más intercambios terapéuticos en el grupo de intervención (RR: 4,2; intervalo de confianza del 95% [IC95%]:3,1-5,8 respecto al control (RR: 1,8; IC95%:1,2-2,6. En el grupo de intervención, el porcentaje de pacientes con omeprazol pasó del 86,2% al 89,3%, y en el control del 84,3% al 84,7%. El coste del grupo IBP disminuyó un 7,6% en el grupo de intervención y aumentó un 2,0% en el control. Conclusiones: El programa de intercambio terapéutico se ha mostrado efectivo. Se trata de una intervención sencilla, capaz de modificar las prescripciones y reducir sus costes.Objective: To assess the impact of substituting proton pump inhibitors (PPI for omeprazole. Method: We performed a community trial of the impact of a therapeutic exchange program in the primary care teams of a region compared with non-implementation in a control region. The study included patients prescribed a PPI between May 2008 and June 2009. The intervention consisted of

  15. Some aspects of the volcanology and geochemistry of the Tengger Caldera, Java, Indonesia: eruption of a K-rich tholeiitic series

    Science.gov (United States)

    van Gerven, M.; Pichler, H.

    The Tengger Caldera together with the active Mount Bromo is situated in Java, Indonesia. Though activity of Mt Bromo has been recorded since 1804, little modern petrographic and geochemical data is available. In this study we provide a detailed petrographic and stratigraphic description of the two major caldera units, i.e. the "pre-caldera formation" and the "post-caldera formation". A zonal arrangement of the alkali content of the Sunda arc volcanoes, i.e. an increase of the alkali content in the lavas across the arc from the trench to the backarc basin, has been noticed for many years. In contrast to the common classification of the geochemistry and magmatic affinity of the Javanese volcanoes related to the depth of the Benioff zone (100-150 km for tholeiitic rocks and 150-250 km for calc-alkaline rocks), we found a tholeiitic trend expressed by increasing FeO∗/MgO with increasing SiO 2 and an average {Zr}/{Y} ratio of 4.9 for the Tengger Caldera volcanics (Benioff zone depth ca 200 km), despite high alkali contents (K 2O > 2 wt%). These features characterize the Tengger Caldera volcanics as medium to high-K tholeiitic andesites and basaltic andesites.

  16. First CSDP (Continental Scientific Drilling Program)/thermal regimes core hole project at Valles Caldera, New Mexico (VC-1): Drilling report

    Energy Technology Data Exchange (ETDEWEB)

    Rowley, J.; Hawkins, W.; Gardner, J. (comps.)

    1987-02-01

    This report is a review and summary of the core drilling operations of the first Valles Caldera research borehole (VC-1) under the Thermal Regimes element of the Continental Scientific Drilling Program (CSDP). The project is a portion of a broader program that seeks to answer fundamental scientific questions about magma, rock/water interactions, and volcanology through shallow (<1-km) core holes at Long Valley, California; Salton Sea, California; and the Valles Caldera, New Mexico. The report emphasizes coring operations with reference to the stratigraphy of the core hole, core quality description, core rig specifications, and performance. It is intended to guide future research on the core and in the borehole, as well as have applications to other areas and scientific problems in the Valles Caldera. The primary objectives of this Valles Caldera coring effort were (1) to study the hydrogeochemistry of a subsurface geothermal outflow zone of the caldera near the source of convective upflow, (2) to obtain structural and stratigraphic information from intracaldera rock formations in the southern ring-fracture zone, and (3) to obtain continuous core samples through the youngest volcanic unit in Valles Caldera, the Banco Bonito rhyolite (approximately 0.1 Ma). All objectives were met. The high percentage of core recovery and the excellent quality of the samples are especially notable. New field sample (core) handling and documentation procedures were successfully utilized. The procedures were designed to provide consistent field handling of the samples and logs obtained through the national CSDP.

  17. Rapid differentiation in a sill-like magma reservoir: a case study from the campi flegrei caldera.

    Science.gov (United States)

    Pappalardo, Lucia; Mastrolorenzo, Giuseppe

    2012-01-01

    In recent decades, geophysical investigations have detected wide magma reservoirs beneath quiescent calderas. However, the discovery of partially melted horizons inside the crust is not sufficient to put constraints on capability of reservoirs to supply cataclysmic eruptions, which strictly depends on the chemical-physical properties of magmas (composition, viscosity, gas content etc.), and thus on their differentiation histories. In this study, by using geochemical, isotopic and textural records of rocks erupted from the high-risk Campi Flegrei caldera, we show that the alkaline magmas have evolved toward a critical state of explosive behaviour over a time span shorter than the repose time of most volcanic systems and that these magmas have risen rapidly toward the surface. Moreover, similar results on the depth and timescale of magma storage were previously obtained for the neighbouring Somma-Vesuvius volcano. This consistency suggests that there might be a unique long-lived magma pool beneath the whole Neapolitan area.

  18. Typology of Natural Hazards and Assessment of Associated Risks in the Mount Bambouto Caldera (Cameroon Line, West Cameroon)

    Institute of Scientific and Technical Information of China (English)

    Ghislain T. ZANGMO; Armand D. KAGOU; David G. NKOUATHIO; Pierre WANDJI

    2009-01-01

    Mount Bambouto is a polygenic stratovoicano of the Cameroon Volcanic Line, built between 21 Ma and 4.5 Ma. It is situated approximately 200 km NE of Mount Cameroon, between 09°55' and 10°15' longitude east and, 05°25' and 05°50' latitude north. The volcano covers an area of (13×8 km). Mount Bambouto is characterized by several natural hazards of different origins: meteorological, such as landslides and rock falls; anthropogenic, such as bushfires, tribal wars and deforestation; and volcanological, such as volcanic eruption. The thematic map shows that 55-60% of the caldera has high probability of occurrence of mass movement. The caldera has a high population density (3000 inhabitants), which increases the level of risk, evaluated at approximately $US3.8 million for patrimony, 3000 civilian deaths and destruction of biodiversity.

  19. Caldera collapse: Perspectives from comparing Galápagos volcanoes, nuclear-test sinks, sandbox models, and volcanoes on Mars

    Science.gov (United States)

    Howard, K.A.

    2010-01-01

    The 1968 trapdoor collapse (1.5 km3) of Fernandina caldera in the Galapágos Islands developed the same kinds of structures as found in small sandbox-collapse models and in concentrically zoned sinks formed in desert alluvium by fault subsidence into underground nuclear-explosion cavities. Fernandina’s collapse developed through shear failure in which the roof above the evacuating chamber was lowered mostly intact. This coherent subsidence contrasts to chaotic piecemeal collapse at small, rocky pit craters, underscoring the role of rock strength relative to subsidence size. The zoning at Fernandina implies that the deflated magma chamber underlay a central basin and a bordering inward-dipping monocline, which separates a blind inner reverse fault from an outer zone of normal faulting. Similar concentric zoning patterns can be recognized in coherent subsidence structures ranging over 16 orders of magnitude in size, from sandbox experiments to the giant Olympus Mons caldera on Mars.

  20. The Late Cretaceous Middle Fork caldera, its resurgent intrusion, and enduring landscape stability in east-central Alaska

    Science.gov (United States)

    Bacon, Charles R.; Dusel-Bacon, Cynthia; Aleinikoff, John N.; Slack, John F.

    2014-01-01

    Dissected caldera structures expose thick intracaldera tuff and, uncommonly, cogenetic shallow plutons, while remnants of correlative outflow tuffs deposited on the pre-eruption ground surface record elements of ancient landscapes. The Middle Fork caldera encompasses a 10 km × 20 km area of rhyolite welded tuff and granite porphyry in east-central Alaska, ∼100 km west of the Yukon border. Intracaldera tuff is at least 850 m thick. The K-feldspar megacrystic granite porphyry is exposed over much of a 7 km × 12 km area having 650 m of relief within the western part of the caldera fill. Sensitive high-resolution ion microprobe with reverse geometry (SHRIMP-RG) analyses of zircon from intracaldera tuff, granite porphyry, and outflow tuff yield U-Pb ages of 70.0 ± 1.2, 69.7 ± 1.2, and 71.1 ± 0.5 Ma (95% confidence), respectively. An aeromagnetic survey indicates that the tuff is reversely magnetized, and, therefore, that the caldera-forming eruption occurred in the C31r geomagnetic polarity chron. The tuff and porphyry have arc geochemical signatures and a limited range in SiO2 of 69 to 72 wt%. Although their phenocrysts differ in size and abundance, similar quartz + K-feldspar + plagioclase + biotite mineralogy, whole-rock geochemistry, and analytically indistinguishable ages indicate that the tuff and porphyry were comagmatic. Resorption of phenocrysts in tuff and porphyry suggests that these magmas formed by thermal rejuvenation of near-solidus or solidified crystal mush. A rare magmatic enclave (54% SiO2, arc geochemical signature) in the porphyry may be similar to parental magma and provides evidence of mafic magma and thermal input.

  1. Aquifer Recharge Estimation through Atmospheric Chloride Mass Balance at Las Cañadas Caldera, Tenerife, Canary Islands, Spain

    OpenAIRE

    Rayco Marrero-Diaz; Alcalá, Francisco J.; Pérez, Nemesio M.; Dina L. López; Melián, Gladys V.; Eleazar Padrón; Germán D. Padilla

    2015-01-01

    The atmospheric chloride mass balance (CMB) method was used to estimate net aquifer recharge in Las Cañadas Caldera, an endorheic summit aquifer area about 2000 m a.s.l. with negligible surface runoff, which hosts the largest freshwater reserve in Tenerife Island, Canary Islands, Spain. The wet hydrological year 2005–2006 was selected to compare yearly atmospheric chloride bulk deposition and average chloride content in recharge water just above the water table, both deduced from periodical...

  2. Numerical models for ground deformation and gravity changes during volcanic unrest: simulating the hydrothermal system dynamics of an active caldera

    OpenAIRE

    Coco, A.; Gottsmann, J.; F. Whitaker; Rust, A; G. Currenti; A. Jasim; S. Bunney

    2015-01-01

    Ground deformation and gravity changes in active calderas during periods of unrest can signal an impending eruption and thus must be correctly interpreted for hazard evaluation. It is critical to differentiate variation of geophysical observables related to volume and pressure changes induced by magma migration from shallow hydrothermal activity associated with hot fluids of magmatic origin rising from depth. In this paper we present a nu...

  3. Evidence from cosmic ray exposure (CRE) dating for the existence of a pre-Minoan caldera on Santorini, Greece

    Science.gov (United States)

    Athanassas, C. D.; Bourlès, D. L.; Braucher, R.; Druitt, T. H.; Nomikou, P.; Léanni, L.

    2016-05-01

    Cosmic ray exposure (CRE) dating was performed on the caldera cliffs of Santorini with the aim of detecting cliff segments predating the Minoan eruption (17th century BCE). The methodology involved the determination of in situ-produced cosmogenic 36Cl concentration in basaltic-to-rhyodacitic whole rocks cropping out in the cliffs. After the samples were processed following the chemical protocol of 36Cl preparation for silicate rocks, 36Cl concentrations were measured by accelerator mass spectrometry (AMS). Important challenges during the implementation procedure were related to large amounts of radiogenic 36Cl, complex modeling of inherited 36Cl, and dominance of the thermal and epithermal (low-energy) neutron capture production pathway. Nevertheless, quantitative assessments on the basis of the contribution of the low-energy neutron capture pathway percent to the total production rate validated the calculated CRE dates. Current CRE ages demonstrate that an ancient caldera existed on pre-Minoan Santorini, occupying at least the northern half of the modern-day caldera.

  4. A three-dimensional QP imaging of the shallowest subsurface of Campi Flegrei offshore caldera, southern Italy

    Science.gov (United States)

    Serlenga, Vincenzo; Lorenzo, Salvatore; Russo, Guido; Amoroso, Ortensia; Garambois, Stephane; Virieux, Jean; Zollo, Aldo

    2016-11-01

    To improve the knowledge of the shallowest subsurface of Campi Flegrei caldera, a 3-D P wave attenuation tomography of the area was performed. We analyzed about 18,000 active seismic traces, which provided a data set of 11,873 Δt* measurements, e.g., the differential travel times to quality factor ratios. These were inverted through an adapted tomographic inversion procedure. The 3-D tomographic images reveal an average QP about 70, interpreted as water-saturated volcanic and marine sediments. An arc-like, low-QP structure at 0.5-1 km depths was interpreted as a densely fractured, fluid-saturated rock volume, well matching the buried rim of Campi Flegrei caldera. The spatial distribution of high- and low-QP bodies in the inner caldera is correlated with low-Vp values and may reflect either the differences in the percentage of fluid saturation of sediments or the presence of vapor state fluids beneath fumarole manifestations.

  5. Deformation of the Long Valley Caldera, California: Inferences from measurements from 1988 to 2001

    Science.gov (United States)

    Langbein, J.O.

    2003-01-01

    Two periods of volcanic unrest occurred between 1989 and 1998 in the Long Valley Caldera, eastern California. Numerous earthquakes were recorded, and these periods of unrest were documented with high-precision geodetic measurements. The first round of unrest started rapidly in late 1989 and slowly decreased in rate through the early 1990s. For this interval there are both leveling and two-color electronic distance meter (EDM) measurements. The second round of unrest started slowly in mid-1997, climaxed in late 1997, and rapidly returned to quiescence by mid-1998. Deformation was recorded by both the two-color EDM and continuous GPS. Both episodes require inflation at 6-7 km beneath the resurgent dome, and both episodes had roughly 0.1 m extension across the resurgent dome. In addition, the data presented here suggest that there is a deeper, 10-20 km, inflation source beneath the south moat of the caldera. For both episodes, the better-resolved inflation beneath the resurgent dome is a near-vertical, prolate spheroid rather than an isotropic source, which suggests that magma came up through vertical cracks. However, the modeling suggests that the location changed with the depth from 6.0 to 6.7 km for the later episode. In contrast to the earlier episode, the 1997-1998 episode has additional deformation in the south moat, where the simplest model is that of a right-lateral slip on a steeply dipping plane that is defined by the location of earthquakes in the south moat. Models of the time-dependent behavior suggest that slip on this fault occurred from late November through December 1997, corresponding to the time of greatest moment release by the earthquake swarm in the south moat. Confounding the interpretation of these data is an active geothermal field near the center of the EDM network and adjacent to the south moat and resurgent dome. Additional modeling of leveling and EDM data within the geothermal field during a period of low rate of inflation of the dome

  6. Are eruptions from linear fissures and caldera ring dykes more likely to produce pyroclastic flows?

    Science.gov (United States)

    Jessop, D. E.; Gilchrist, J.; Jellinek, A. M.; Roche, O.

    2016-11-01

    Turbulent volcanic jets are produced by highly-energetic explosive eruptions and may form buoyant plumes that rise many tens of kilometres into the atmosphere to form umbrella clouds or collapse to generate ground-hugging pyroclastic flows. Ash injected into the atmosphere can be transported for many hundreds of kilometres with the potential to affect climate, disrupt global air travel and cause respiratory health problems. Pyroclastic flows, by contrast, are potentially catastrophic to populations and infrastructure close to the volcano. Key to which of these two behaviours will occur is the extent to which the mechanical entrainment and mixing of ambient air into the jet by large (entraining) eddies forming the jet edge changes the density of the air-ash mixture: low entrainment rates lead to pyroclastic flows and high entrainment rates give rise to buoyant plumes. Recent experiments on particle-laden (multi-phase) volcanic jets from flared and straight-sided circular openings suggest that the likelihood for buoyant plumes will depend strongly on the shape and internal geometry of the vent region. This newly recognised sensitivity of the fate of volcanic jets to the structure of the vent is a consequence of a complex dynamic coupling between the jet and entrained solid particles, an effect that has generally been overlooked in previous studies. Building on this work, here we use an extensive series of experiments on multi-phase turbulent jets from analogue linear fissures and annular ring fractures to explore whether the restrictive vent geometry during cataclysmic caldera-forming (CCF) eruptions will ultimately lead a relatively greater frequency of pyroclastic flows than eruptions from circular vents on stratovolcanoes. Our results, understood through scaling analyses and a one-dimensional theoretical model, show that entrainment is enhanced where particle motions contribute angular momentum to entraining eddies. However, because the size of the entraining

  7. Comparison between 3D model of Pisciarelli area (Campi Flegrei caldera) through Terrestrial Laser Scanner

    Science.gov (United States)

    Caputo, Teresa; Somma, Renato; Marino, Ermanno; Terracciano, Rosario; Troise, Claudia; De Natale, Giuseppe

    2016-04-01

    The volcanic/geothermal area of Pisciarelli is located within Campi Flegrei caldera .This last is a densely populated area, including the Pozzuoli town and bordering the western side of the Naples city, this causes a high vulnerability and consequently a high volcanic risk. In the recent decades this area has experienced minor ground uplift episodes accompanied by low magnitude seismicity and by strong intensification of degassing activity in particular localized at Pisciarelli area. We present the results of the Terrestrial Laser Scanner (TLS), using a Reigl VZ1000®, analysis of Pisciarelli area performed in June 2013 and the comparison with the data acquired later in March 2014. We apply the TLS technique based on Time of Flight (TOF) method in order to define an accurate 3D digital model for detailed analysis of this area performing numerous scans from different points of view in the area. In this ways was ensured a good coverage of the whole investigated area in order to avoid shaded portion due to the high soil degassing activity. Such fact limits the capacity of laser penetration is caused by wavelength near infrared range. For each survey was obtained a Digital Terrain Model (DTM) from the reconstructed data and both were compared. In particular, we have identified two "critical" areas of interest that will be monitored more frequently. These are: 1) in the lower part of the studied area a major fault line that bounding the Agnano caldera moderately NE-dipping; 2) in the upper part of the study area a zone of depletion with its zone of accumulation. The DTM were georeferenced into the UTM-WGS84 reference frame. The aim of this work is to define a procedure to compare between 3D model applied to monitoring of this area. Also to evaluate of volumetric and morphologic changes and to recognizing unstable masses by comparison of 3D data. For this purpose other TLS surveys will be performed in the upcoming in this active volcanic/geothermal area.

  8. A novel thermophilic methane-oxidizing bacteria from thermal springs of Uzon volcano caldera, Kamchatka

    Science.gov (United States)

    Dvorianchikova, E.; Kizilova, A.; Kravchenko, I.; Galchenko, V.

    2012-04-01

    Methane is a radiatively active trace gas, contributing significantly to the greenhouse effect. It is 26 times more efficient in absorbing and re-emitting infrared radiation than carbon dioxide. Methanotrophs play an essential role in the global carbon cycle by oxidizing 50-75% of the biologically produced methane in situ, before it reaches the atmosphere. Methane-oxidizing bacteria are isolated from the various ecosystems and described at present. Their biology, processes of methane oxidation in fresh-water, marsh, soil and marine habitats are investigated quite well. Processes of methane oxidation in places with extreme physical and chemical conditions (high or low , salinity and temperature values) are studied in much smaller degree. Such ecosystems occupy a considerable part of the Earth's surface. The existence of aerobic methanotrophs inhabiting extreme environments has been verified so far by cultivation experiments and direct detection of methane monooxygenase genes specific to almost all aerobic methanotrophs. Thermophilic and thermotolerant methanotrophs have been isolated from such extreme environments and consist of the gammaproteobacterial (type I) genera Methylothermus, Methylocaldum, Methylococcus and the verrucomicrobial genus Methylacidiphilum. Uzon volcano caldera is a unique area, where volcanic processes still happen today. Hydrothermal springs of the area are extreme ecosystems which microbial communities represent considerable scientific interest of fundamental and applied character. A thermophilic aerobic methane-oxidising bacterium was isolated from a sediment sample from a hot spring (56.1; 5.3) of Uzon caldera. Strain S21 was isolated using mineral low salt medium. The headspace gas was composed of CH4, Ar, CO2, and O2 (40:40:15:5). The temperature of cultivation was 50, pH 5.5. Cells of strain S21 in exponential and early-stationary phase were coccoid bacilli, about 1 μm in diameter, and motile with a single polar flagellum. PCR and

  9. Ambient Noise Imaging of Menengai Caldera in the Central Kenya Dome

    Science.gov (United States)

    Patlan, E.; Wamalwa, A.; Kaip, G.; Velasco, A. A.

    2012-12-01

    The Geothermal Development Company (GDC) and the University of Texas at El Paso (UTEP) have deployed fourteen seismic stations around the Menengai geothermal field along the Kenya rift system to monitor the seismicity around the Menengai Caldera. The goal of the project is to identify active faults and fracture systems that may contain hydrothermal fluids and favorable drilling targets, plus image the magma chamber. The deployment has a variety of seismic sensors with different frequency responses, and the instruments where deployed in two stages, with seven stations recording continuously since Mar. 2011, and another seven stations being deployed in Aug. 2011. We use vertical component waveform data from Mar. 2011 to Mar. 2012 to image the caldera using ambient noise tomography. We first cut waveform data every 5 hours recorded at single seismic station, applying a 1-bit normalization to eliminate earthquake signals and any instrumentation irregularities. We also apply spectral whitening in order to flatten the spectrum to minimize the source contamination. We cross-correlate waveforms to retrieve the Green's functions for all combinations of stations within our seismic network, accounting for different frequency responses, given the different sensors frequency responses (Guralp 3T's and 40Ts). We introduce a period cut-off in which it is acceptable for closely spaced station-pairs to have inter-station distance greater than ~3 wavelengths. This avoids deterioration of the cross correlation result. We compute signal-to-noise-ratios (SNR) of the cross-correlation to determine the quality of the data, where the SNR is defined as the peak amplitude divided by the root-mean-square noise in the window. The computed cross-correlations were stacked in 3-month bins to account for seasonal variability in order to estimate the group velocity uncertainties at each period. We used Frequency Time Analysis (FTAN) and a match filter analysis (MTA) in order to approximate the

  10. Structure and evolution of an active resurgent dome evidenced by geophysical investigations: The Yenkahe dome-Yasur volcano system (Siwi caldera, Vanuatu)

    Science.gov (United States)

    Brothelande, E.; Lénat, J.-F.; Chaput, M.; Gailler, L.; Finizola, A.; Dumont, S.; Peltier, A.; Bachèlery, P.; Barde-Cabusson, S.; Byrdina, S.; Menny, P.; Colonge, J.; Douillet, G. A.; Letort, J.; Letourneur, L.; Merle, O.; Di Gangi, F.; Nakedau, D.; Garaebiti, E.

    2016-08-01

    In this contribution, we focus on one of the most active resurgences on Earth, that of the Yenkahe dome in the Siwi caldera (Tanna Island, Vanuatu), which is associated with the persistently active Yasur volcano. Gravity and magnetic surveys have been carried out over the past few years in the area, as well as electrical methods including electrical resistivity tomography (ERT), time domain electro-magnetics (TDEM) and self-potential (SP). These investigations were completed by thermometry, CO2 soil gas measurements, field observations and sampling. This multi-method approach allows geological structures within the caldera to be identified, as well as associated hydrothermal features. The global structure of the caldera is deduced from gravity data, which shows the caldera rim as a high density structure. Large lava fields, emplaced before and after the onset of resurgence, are evidenced by combined gravity, magnetic and resistivity signals. In the middle of the caldera, the Yenkahe dome apparently results from a combination of volcanic and tectonic events, showing that lava extrusion and resurgence have been operating simultaneously or alternately during the Siwi caldera post-collapse history. There is a clear distinction between the western and eastern parts of the dome. The western part is older and records the growth of an initial volcanic cone and the formation of a small caldera. This small caldera (paleo-Yasur caldera), partially filled with lava flows, is the present-day focus of volcanic activity and associated fluid circulation and alteration. The eastern part of the dome is presumably younger, and is characterized by intense, extensive hydrothermal alteration and activity. Its northern part is covered by lava flow piles and exhibits a shallow hydrothermal zone in ERT. The southern part has hydrothermal alteration and activity extending at least down to the base of the resurgent dome. This part of the dome is built up of low cohesion rock and is thus

  11. Numerical simulation of the combustion in natural gas boiler by using a reduced reaction mechanism; Simulacion numerica de la combustion en una caldera a gas natural utilizando un mecanismo de reaccion reducido

    Energy Technology Data Exchange (ETDEWEB)

    Echaniz, Victoria; Brizuela, Eduardo [Universidad Nacional de Mar del Plata (Argentina). Facultad de Ingenieria. Dept. de Ingenieria Mecanica

    2001-07-01

    Combustion of natural gas in air in a utility boiler is simulated by means of a finite volume approach, using a Reduced Reaction Scheme and Eddy Break Up concepts. Results are presented for a turbulent diffusion flame, under operational conditions and in full size, including heat transfer by conduction/convection and radiation. Preliminary results only are presented and a limited comparison with experimental results is made due to the scope of the task which involves a facility in service. Nevertheless, results are considered satisfactory, although there are indications that it is necessary to continue refining the mixing and radiation models for better matching with operational conditions. (author)

  12. Building a flood hazard map due to magma effusion into the caldera lake of the Baekdusan Volcano

    Science.gov (United States)

    Lee, K.; Kim, S.; Yun, S.; Yu, S.; Kim, I.

    2013-12-01

    Many volcanic craters and calderas are filled with large amounts of water that can pose significant flood hazards to downstream communities due to their high elevation and the potential for catastrophic releases of water. Recent reports pointed out the Baekdusan volcano that is located between the border of China and North Korea as a potential active volcano. Since Millennium Eruption around 1000 AD, smaller eruptions have occurred at roughly 100-year intervals, with the last one in 1903. The volcano is showing signs of waking from a century-long slumber recently and the volcanic ash may spread up to the northeastern of Japan. The development of various forecasting techniques to prevent and minimize economic and social damage is in urgent need. Floods from lake-filled calderas may be particularly large and high. Volcanic flood may cause significant hydrologic hazards for this reason. This study focuses on constructing a flood hazard map triggered by the uplift of lake bottom due to magma effusion in the Baekdusan volcano. A physically-based uplift model was developed to compute the amount of water and time to peak flow. The ordinary differential equation was numerically solved using the finite difference method and Newton-Raphson iteration method was used to solve nonlinear equation. The magma effusion rate into the caldera lake is followed by the past record from other volcanic activities. As a result, the hydrograph serves as an upper boundary condition when hydrodynamic model (Flo-2D) runs to simulate channel routing downstream. The final goal of the study stresses the potential flood hazard represented by the huge volume of water in the caldera lake, the unique geography, and the limited control capability. he study will contribute to build a geohazard map for the decision-makers and practitioners. Keywords: Effusion rate, Volcanic flood, Caldera lake, Uplift, Flood hazard map Acknowledgement This research was supported by a grant [NEMA-BAEKDUSAN-2012-1-2] from

  13. The Campi Flegrei Deep Drilling Project (CFDDP): New insight on caldera structure, evolution and hazard implications for the Naples area (Southern Italy)

    Science.gov (United States)

    De Natale, Giuseppe; Troise, Claudia; Mark, Darren; Mormone, Angela; Piochi, Monica; Di Vito, Mauro A.; Isaia, Roberto; Carlino, Stefano; Barra, Diana; Somma, Renato

    2016-12-01

    The 501 m deep hole of the Campi Flegrei Deep Drilling Project, located west of the Naples metropolitan area and inside the Campi Flegrei caldera, gives new insight to reconstruct the volcano-tectonic evolution of this highly populated volcano. It is one of the highest risk volcanic areas in the world, but its tectonic structure, eruptive history, and size of the largest eruptions are intensely debated in the literature. New stratigraphic and 40Ar/39Ar geochronological dating allow us to determine, for the first time, the age of intracaldera deposits belonging to the two highest magnitude caldera-forming eruptions (i.e., Campanian Ignimbrite, CI, 39 ka, and Neapolitan Yellow Tuff, NYT, 14.9 ka) and to estimate the amount of collapse. Tuffs from 439 m of depth yield the first 40Ar/39Ar age of ca. 39 ka within the caldera, consistent with the CI. Volcanic rocks from the NYT were, moreover, detected between 250 and 160 m. Our findings highlight: (i) a reduction of the area affected by caldera collapse, which appears to not include the city of Naples; (ii) a small volume of the infilling caldera deposits, particularly for the CI, and (iii) the need for reassessment of the collapse amounts and mechanisms related to larger eruptions. Our results also imply a revaluation of volcanic risk for the eastern caldera area, including the city of Naples. The results of this study point out that large calderas are characterized by complex collapse mechanisms and dynamics, whose understanding needs more robust constraints, which can be obtained from scientific drilling.

  14. Quantifying Soil Organic Carbon Redistribution after Forest Fire using Thermal Analyses, Valles Caldera, New Mexico

    Science.gov (United States)

    Kuklewicz, K. B.; Rasmussen, C.

    2014-12-01

    The frequency and severity of wildfire in western conifer forests is expected to increase with continued climate change induced warming and drying. The effects of wildfire on carbon cycle processes, and particularly surface soil organic matter composition and post fire erosive redistribution is poorly understood. The recent Thompson Ridge wildfire event in 2013 in the Valles Caldera, part of the Jemez-Catalina Critical Zone Observatory, provides the opportunity to track post-fire changes in surface soil organic matter composition over time relative to pre-fire conditions. Here we applied thermal analyses to quantify changes in surface soil organic matter composition, with a focus on charred materials, across a range of hillslope and convergent landscape positions. It was hypothesized that the fraction of charred material would increase post-burn in all surface soils, with a subsequent decline in hillslope positions and a gain in convergent positions as surface material was eroded and deposited in water gathering portions of the landscape. Our results confirmed that charcoal increased directly after the fire in all samples, but a clear signal of erosive redistribution was not observed, suggesting that the movement of charcoal throughout a landscape is more complex than the simple hypothesis put forward here. Future work will expand the spatial distribution of samples in a systematic fashion that better captures variation in topography and erosive versus depositional areas of the landscape.

  15. Dynamic triggering of microearthquakes in the Long Valley Caldera and Coso Geothermal Field

    Science.gov (United States)

    Aiken, C.; Peng, Z.; Wu, C.

    2010-12-01

    Recent studies have shown that microearthquakes can be dynamically triggered by the passing of surface waves from regional and teleseismic events. However, the underlying physical mechanisms and the necessary conditions that favor dynamic triggering are still in debate. Here we conduct a systematic search of dynamically triggered microearthquakes around the Long Valley Caldera (LVC) and Coso Geothermal Field (CGF) in California. In each region, we select distant mainshocks in 1999-2010 with M>=7.5 over 1000 km away, or M>=5.5 between 100-2500 km. Next, we apply 2-8 or 2-16 Hz band-pass-filtered data to the three-component seismograms recorded at each region, and identify triggered events as high-frequency seismic energy during large-amplitude surface waves of regional and teleseismic events. We calculate the beta statistic values based on events listed in the local earthquake catalogs and hand-picked events from the envelope functions, and verify that the triggering is statistically significant. Based on this simple procedure, we have identified many distant events that have triggered activity in both regions, including the recent 08/03/2009 and 04/04/2010 Baja California earthquakes at regional distances, and the 02/27/2010 Chile earthquake at teleseismic distances. Our next steps are to examine the dynamic triggering thresholds in each region, and to understand the triggering potential in terms of frequency, amplitude, incident angle, and type of surface waves.

  16. The shallow-water chitons (Mollusca, Polyplacophora of Caldera, Region of Atacama, northern Chile

    Directory of Open Access Journals (Sweden)

    Juan Francisco Araya

    2015-03-01

    Full Text Available The Molluscan species of the northern littoral of Chile have been sparsely studied. This work reviews for the first time the diversity of polyplacophoran molluscs around the port of Caldera, in the Region of Atacama (26°45’49”S; 70°45’17”W to 27°20’23”S; 70°56’46”W, northern Chile. Eleven species were found in this study: Acanthopleura echinata (Barnes, 1824; Callistochiton pulchellus (Gray, 1828; Calloplax vivipara (Plate, 1899, Chaetopleura peruviana (Lamarck, 1819; Chiton cumingsii Frembly, 1827; Chiton granosus Frembly, 1827; Chiton magnificus Deshayes, 1827; Enoplochiton niger (Barnes, 1824, Radsia barnesii (Gray, 1828, Tonicia atrata (G. B. Sowerby II, 1840 and Tonicia chilensis (Frembly, 1827. All of the species occurring in the area have distributions in the southeastern Pacific Ocean, from Ecuador to central Chile, and three of them are species endemic to the Chilean coasts (Calloplax vivipara, Radsia barnesii, and Tonicia atrata. This diversity of species is comparable to that of better surveyed faunas of central and southern Chile or Patagonia. Of the eleven species recorded, the geographic distribution records for Callistochiton pulchellus, Radsia barnesii and Tonicia atrata are extended, and Calloplax vivipara is found alive again after 40 years, filling a gap in its known distribution. Illustrations of living specimens in their habitat, distribution records and a taxonomic key for all the studied taxa are also provided.

  17. Duration of the Banco Bonito Rhyolite Eruption, Vales Caldera, New Mexico based on magma transport modeling

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, Benjamin R. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Baldridge, W. Scott [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Gable, Carl W. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Sicilian, James M. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2007-03-05

    Finite volume calculations of the flow of rhyolite are presented to investigate the fate of viscous magmas flowing in planar fractures with realistic length to width ratios of up to 2500:1. Heat and mass transfer for a melt with a temperature dependent viscosity and the potential to undergo phase change are considered. Magma driving pressures and dike widths are chosen to satisfy simple elastic considerations. These models are applied within a parameter space relevant to the Banco Bonito rhyolite flow, Valles caldera, New Mexico. We estimate a maximum eruption duration for the event of ~200 days, realized at a minimum possible dike width of 5-6 m and driving pressure of 7-8 MPa. Simplifications in the current model may warrant scaling of these results. However, we demonstrate the applicability of our model to magma dynamics issues and suggest that such models may be used to infer information about both the timing of an eruption and the evolution of the associated magma source.

  18. Young cumulate complex beneath Veniaminof caldera, Aleutian arc, dated by zircon in erupted plutonic blocks

    Science.gov (United States)

    Bacon, Charles R.; Sisson, Thomas W.; Mazdab, Frank K.

    2007-06-01

    Mount Veniaminof volcano, Alaska Peninsula, provides an opportunity to relate Quaternary volcanic rocks to a coeval intrusive complex. Veniaminof erupted tholeiitic basalt through dacite in the past ˜260 k.y. Gabbro, diorite, and miarolitic granodiorite blocks, ejected 3700 14C yr B.P. in the most recent caldera-forming eruption, are fragments of a shallow intrusive complex of cumulate mush and segregated vapor-saturated residual melts. Sensitive high-resolution ion microprobe (SHRIMP) analyses define 238U-230Th isochron ages of 17.6 ± 2.7 ka, 5 +11/-10 ka, and 10.2 ± 4.0 ka (2σ) for zircon in two granodiorites and a diorite, respectively. Sparse zircons from two gabbros give 238U-230Th model ages of 36 ± 8 ka and 26 ± 7 ka. Zircons from granodiorite and diorite crystallized in the presence of late magmatic aqueous fluid. Although historic eruptions have been weakly explosive Strombolian fountaining and small lava effusions, the young ages of plutonic blocks, as well as late Holocene dacite pumice, are evidence that the intrusive complex remains active and that evolved magmas can segregate at shallow levels to fuel explosive eruptions.

  19. Proyecto MMM (MiniWEB, Multilingüe, Maxiaprendizaje Intercambio y comunicación entre centros educativos de diferentes países vía internet

    Directory of Open Access Journals (Sweden)

    Marta Liesa Orus

    2012-04-01

    Full Text Available El presente trabajo relata un proyecto realizado en una comunidad española, con el aporte de la Universidad de Zaragoza, en que se usan ordenadores y su multiplicidad de oportunidades como herramienta actual de trabajo, en classes de educacion infantil, con los objjetivos de compensar desigualdades, prevenir el analfabetismo y el fracasso escolar, facilitar el aprendizaje de la lectura, impulsar la utilización de la tecnologia desde el inicío de la escolarización y facilitar el trabajo autônomo del niño. Es um proyecto en que participam, además de España, Francia, USA y Andorra, lo que posibilita un intercambio tanto entre los alunnos, como entre los professore, através de la internet.

  20. Intercambio gaseoso y contenido de azúcares en raíces de los genotipos de yuca TMS60444 y CAGBS1A8-3A crecidos bajo condiciones de campo

    OpenAIRE

    Maldonado Valero, Bibiana Andrea

    2012-01-01

    En la presente investigación se estudiaron los genotipos de yuca TMS60444 “silvestre” y CAGBS1A8-3A “transgénico” por su potencial promisorio para producción de bioetanol. En plantas de 3, 8 y 13 meses de edad, se evaluó en hojas mediante el análisis de gases en infrarrojo IRGA el intercambio gaseoso en relación con factores climáticos, y se determinaron en raíces los niveles de glucosa Glc, fructosa Frc y sacarosa Suc con cromatografía líquida de alta eficiencia HPLC. La respuesta fotosintét...

  1. A complex magma reservoir system for a large volume intra- to extra-caldera ignimbrite: Mineralogical and chemical architecture of the VEI8, Permian Ora ignimbrite (Italy)

    Science.gov (United States)

    Willcock, M. A. W.; Bargossi, G. M.; Weinberg, R. F.; Gasparotto, G.; Cas, R. A. F.; Giordano, G.; Marocchi, M.

    2015-11-01

    Intra-caldera settings record a wealth of information on caldera-forming processes, yet field study is rarely possible due to lack of access and exposure. The Permian Ora Formation, Italy, preserves > 1000 m of vertical section through its intra-caldera succession. This provides an excellent opportunity to detail its mineralogical and geochemical architecture and gain understanding of the eruption evolution and insight into the pre-eruptive magma system. Detailed juvenile clast phenocryst and matrix crystal fragment point count and image analysis data, coupled with bulk-rock chemistry and single mineral compositional data, show that the Ora ignimbrite succession is rhyolitic (72.5-77.7% SiO2), crystal-rich (~ 25-57%; average 43%) and has a constant main mineral population (volcanic quartz + sanidine + plagioclase + biotite). Although a seemingly homogeneous ignimbrite succession, important subtle but detectable lateral and vertical variations in modal mineralogy and bulk-rock major and trace elements are identified here. The Ora Formation is comprised of multiple lithofacies, dominated by four densely welded ignimbrite lithofacies. They are crystal-rich, typically lithic-poor (cake' stratigraphy. The intra-caldera succession is divided into two depo-centres: Southern and Northern, with proximal extra-caldera deposits preserved to the south and north of the system. The Southern and Northern intra-caldera ignimbrite successions are discriminated by variations in total biotite crystal abundance. Detailed mineralogical and chemical data records decreases across the caldera system from south to north in biotite phenocrysts in the groundmass of juvenile clasts (average 12-2%), matrix biotite (average 7.5-2%) and plagioclase crystal fragments (average 18-6%), and total crystal fragment abundance in the matrix (average 47-37%); a biotite compositional change to iron-rich (0.57-0.78 Fe); and bulk-rock element decreases in Fe2O3, MgO, P2O5, Ce, Hf, V, La and Zr, and

  2. Distributed-Temperature-Sensing Using Optical Methods: A First Application in the Offshore Area of Campi Flegrei Caldera (Southern Italy for Volcano Monitoring

    Directory of Open Access Journals (Sweden)

    Stefano Carlino

    2016-08-01

    Full Text Available A temperature profile 2400 m along the off-shore active caldera of Campi Flegrei (Gulf of Pozzuoli was obtained by the installation of a permanent fiber-optic monitoring system within the framework of the Innovative Monitoring for Coastal and Marine Environment (MON.I.C.A project. The system consists of a submerged, reinforced, multi-fiber cable containing six single-mode telecom grade optical fibers that, exploiting the stimulated Brillouin scattering, provide distributed temperature sensing (DTS with 1 m of spatial resolution. The obtained data show that the offshore caldera, at least along the monitored profile, has many points of heat discharge associated with fluid emission. A loose association between the temperature profile and the main structural features of the offshore caldera was also evidenced by comparing DTS data with a high-resolution reflection seismic survey. This represents an important advancement in the monitoring of this high-risk volcanic area, since temperature variations are among the precursors of magma migration towards the surface and are also crucial data in the study of caldera dynamics. The adopted system can also be applied to many other calderas which are often partially or largely submerged and hence difficult to monitor.

  3. Water-level changes induced by local and distant earthquakes at Long Valley caldera, California

    Science.gov (United States)

    Roeloffs, E.; Sneed, M.; Galloway, D.L.; Sorey, M.L.; Farrar, C.D.; Howle, J.F.; Hughes, J.

    2003-01-01

    Distant as well as local earthquakes have induced groundwater-level changes persisting for days to weeks at Long Valley caldera, California. Four wells open to formations as deep as 300 m have responded to 16 earthquakes, and responses to two earthquakes in the 3-km-deep Long Valley Exploratory Well (LVEW) show that these changes are not limited to weathered or unconsolidated near-surface rocks. All five wells exhibit water-level variations in response to earth tides, indicating they can be used as low-resolution strainmeters. Earthquakes induce gradual water-level changes that increase in amplitude for as long as 30 days, then return more slowly to pre-earthquake levels. The gradual water-level changes are always drops at wells LKT, LVEW, and CH-10B, and always rises at well CW-3. At a dilatometer just outside the caldera, earthquake-induced strain responses consist of either a step followed by a contractional strain-rate increase, or a transient contractional signal that reaches a maximum in about seven days and then returns toward the pre-earthquake value. The sizes of the gradual water-level changes generally increase with earthquake magnitude and decrease with hypocentral distance. Local earthquakes in Long Valley produce coseismic water-level steps; otherwise the responses to local earthquakes and distant earthquakes are indistinguishable. In particular, water-level and strain changes in Long Valley following the 1992 M7.3 Landers earthquake, 450 km distant, closely resemble those initiated by a M4.9 local earthquake on November 22, 1997, during a seismic swarm with features indicative of fluid involvement. At the LKT well, many of the response time histories are identical for 20 days after each earthquake, and can be matched by a theoretical solution giving the pore pressure as a function of time due to diffusion of a nearby, instantaneous, pressure drop. Such pressure drops could be produced by accelerated inflation of the resurgent dome by amounts too

  4. Strengths and strain energies of volcanic edifices: implications for eruptions, collapse calderas, and landslides

    Directory of Open Access Journals (Sweden)

    A. Gudmundsson

    2012-07-01

    Full Text Available Natural hazards associated with volcanic edifices depend partly on how fracture resistant the edifices are, i.e. on their strengths. Observations worldwide indicate that large fluid-driven extension fractures (dikes, inclined sheets, shear fractures (landslides, and mixed-mode fractures (ring dikes and ring faults normally propagate more easily in a basaltic edifice (shield volcano than in a stratovolcano. For example, dike-fed eruptions occur once every few years in many basaltic edifices but once every 102-3 yr in many stratovolcanoes. Large landslides and caldera collapses also appear to be more common in a typical basaltic edifice/shield volcano than in a typical stratovolcano. In contrast to a basaltic edifice, a stratovolcano is composed of mechanically dissimilar rock layers, i.e. layers with mismatching elastic properties (primarily Young's modulus. Elastic mismatch encourages fracture deflection and arrest at contacts and increases the amount of energy needed for a large-scale edifice failure. Fracture-related hazards depend on the potential energy available to propagate the fractures which, in turn, depends on the boundary conditions during fracture propagation. Here there are two possible scenarios: one in which the outer boundary of the volcanic edifice or rift zone does not move during the fracture propagation (constant displacement; the other in which the boundary moves (constant load. In the former, the total potential energy is the strain energy stored in the volcano before fracture formation; in the latter, the total potential energy is the strain energy plus the work done by the forces moving the boundary. Constant-displacement boundary conditions favor small eruptions, landslides, and caldera collapses, whereas constant-load conditions favor comparatively large eruptions, landslides, and collapses. For a typical magma chamber (sill-like with a diameter of 8 km, the strain energy change due to magma-chamber inflation

  5. The Life and Times of Supervolcanoes: Inferences from Long Valley Caldera

    Science.gov (United States)

    Simon, Justin

    2014-01-01

    Cataclysmic eruptions of silicic magma from "supervolcanoes" are among the most awe-inspiring natural phenomena found in the geologic record, in terms of size, power, and potential hazard. Based on the repose intervals between eruptions of this magnitude, the magmas responsible for them could accumulate gradually in the shallow crust over time scales that may be in excess of a million years (Smith, 1979; Spera and Crisp, 1981; Shaw, 1985). Pre-eruption magma residence time scales can also be inferred from the age difference between eruption (i.e., using 40Ar/39Ar dating to determine the time when hot erupted material cools to below its Ar closure temperature, 200 to 600 degC) and early pre-eruption crystallization (i.e., zircon saturation temperatures; Reid et al., 1997). I will discuss observations from Long Valley a Quaternary volcanic center in California. Long Valley is a voluminous, dominantly silicic caldera system. Based on extensive dating of accessory minerals (e.g., U-Th-Pb dating of zircon and allanite) along with geochemical and isotopic data we find that silicic magmas begin to crystallize 10's to 100's of thousands of years prior to their eruption and that rhyolites record episodes of punctuated and independent evolution rather than the periodic tapping of a long-lived magma. The more punctuated versus more gradual magma accumulation rates required by the absolute and model ages, respectively, imply important differences in the mass and heat fluxes associated with the generation, differentiation, and storage of voluminous rhyolites and emphasize the need to reconcile the magmatic age differences.

  6. Change in Magma Dynamics at Okataina Rhyolite Caldera revealed by Plagioclase Textures and Geochemistry

    Science.gov (United States)

    Shane, P. A. R.

    2015-12-01

    A fundamental reorganization of magma dynamics at Okataina volcano, New Zealand, occurred at 26 ka involving a change from smaller volume, high-temperature rhyodacite magmas to a lower eruptive tempo of larger volume, low-temperature, rhyolite magmas. Zircon studies demonstrate the presence of a periodically active, long-lived (100,000 yr) magmatic reservoir. However, there is little correlation between periods of zircon crystallization and eruption events. In contrast, the changing magmatic dynamics is revealed in plagioclase growth histories. Crystals from the ~0.7 ka Kaharoa eruption are characterized by resorbed cores displaying a cellular-texture of high-An (>40) zones partially replaced by low-An (Mg, Sr and Ti follow the resorption surface and display rimward depletion trends, accompanied by Ba and REE enrichment. The zonation is consistent with fractional crystallization and cooling. The cores display wide trace element diversity, pointing to crystallization in a variety of melts, before transport and mixing into a common magma where the rims grew. Plagioclase from the ~36 ka Hauparu eruption display several regrowth zones separated by resorption surfaces, which surround small resorbed cores with a spongy cellular texture of variable An content (An 40-50). The crystals display step-wise re-growth of successively higher An, Fe, Mg and Ti content, consistent with progressive mafic recharge. Two crystal groups are distinguished by trace element chemistry indicating growth in separate melts and co-occurrence via magma-mingling. The contrasting zoning patterns in plagioclase correspond to the evolutionary history of magmatism at Okataina. Emptying of the magma reservoir following caldera eruption at 46 ka reduced barriers to mafic magma ascent. This is recorded by the frequent resorption and recharge episodes in Hauparu crystals. Subsequent re-development of a more silicic reservoir zone (post-26 ka) dampened thermal and mass perturbations, resulting in simpler

  7. Renewed Volcano-Stratigraphc Studies of Calderas with Geothermal Potential in Mexico

    Science.gov (United States)

    Macias, J. L.; Arce, J. L.; García-Tenorio, F.; Layer, P. W.; Saucedo, R.; Castro, R.; Garduño, V. H.; Jimenez, A.; Pérez, H.; Valdez, G.; Meriggi, L.

    2014-12-01

    During the past six years we have carried out volcanologic fieldwork either in active geothermal fields in Mexico (Los Azufres, Tres Vírgenes, and Cerro Prieto) or in potential sites in which some geothermal exploration studied had been done by the National Power Company (CFE). These studies have been very successful in reassessing the location of the geothermal reservoirs within the volcanic successions through detailed mapping of the volcanic units using high resolution topography and satellite imagery to produce 3-D imagery in conjunction with field work to produce preliminary geologic maps. Detailed stratigraphy of volcanic units, assisted with 40Ar/39Ar and radiocarbon geochronology have redefined the evolution of some of these complexes. For example, our studies at Los Azufres geothermal field located in the State of Michoacán indicate that the volcanic complex of the same name sits upon a structural high transected by E-W faults related to the youngest structures of the Trans-Mexican Volcanic Belt. The volcanic complex has been emplaced during the past ~1.5 Ma. During this time, magmas evolved from basaltic to rhyolitic in composition with the emplacement of circa 100 vents. Several landforms have undergone intense hydrothermal alteration and, in some cases, generated debris avalanches. The revised stratigraphy based on drill holes and new dates of cores suggested that the geothermal reservoir is hosted in Miocene rocks bracketed between the Miocene Sierra de Mil Cumbres volcanics (17-22 Ma) and the products of the volcanic field itself. Similar studies will be carried out at four other Pleistocene calderas (Acoculco, La Primavera, Aguajito and Reforma) attempting to refine their volcanic stratigraphy, evolution, and the location of the geothermal system, and those results will help in the design of exploration strategies for geothermal sources.

  8. Mass transfer constraints on the chemical evolution of an active hydrothermal system, Valles caldera, New Mexico

    Science.gov (United States)

    White, A.F.; Chuma, N.J.; Goff, F.

    1992-01-01

    Partial equilibrium conditions occur between fluids and secondary minerals in the Valles hydrothermal system, contained principally in the Tertiary rhyolitic Bandelier Tuff. The mass transfer processes are governed by reactive phase compositions, surface areas, water-rock ratios, reaction rates, and fluid residence times. Experimental dissolution of the vitric phase of the tuff was congruent with respect to Cl in the solid and produced reaction rates which obeyed a general Arrhenius release rate between 250 and 300??C. The 18O differences between reacted and unreacted rock and fluids, and mass balances calculations involving Cl in the glass phase, produced comparable water-rock ratios of unity, confirming the importance of irreversible reaction of the vitric tuff. A fluid residence time of approximately 2 ?? 103 years, determined from fluid reservoir volume and discharge rates, is less than 0.2% of the total age of the hydrothermal system and denotes a geochemically and isotopically open system. Mass transfer calculations generally replicated observed reservoir pH, Pco2, and PO2 conditions, cation concentrations, and the secondary mineral assemblage between 250 and 300??C. The only extraneous component required to maintain observed calcite saturation and high Pco2 pressures was carbon presumably derived from underlying Paleozoic limestones. Phase rule constraints indicate that Cl was the only incompatible aqueous component not controlled by mineral equilibrium. Concentrations of Cl in the reservoir directly reflect mass transport rates as evidenced by correlations between anomalously high Cl concentrations in the fluids and tuff in the Valles caldera relative to other hydrothermal systems in rhyolitic rocks. ?? 1992.

  9. Joint body and surface wave tomography applied to the Toba caldera complex (Indonesia)

    Science.gov (United States)

    Jaxybulatov, Kairly; Koulakov, Ivan; Shapiro, Nikolai

    2016-04-01

    We developed a new algorithm for a joint body and surface wave tomography. The algorithm is a modification of the existing LOTOS code (Koulakov, 2009) developed for local earthquake tomography. The input data for the new method are travel times of P and S waves and dispersion curves of Rayleigh and Love waves. The main idea is that the two data types have complementary sensitivities. The body-wave data have good resolution at depth, where we have enough crossing rays between sources and receivers, whereas the surface waves have very good near-surface resolution. The surface wave dispersion curves can be retrieved from the correlations of the ambient seismic noise and in this case the sampled path distribution does not depend on the earthquake sources. The contributions of the two data types to the inversion are controlled by the weighting of the respective equations. One of the clearest cases where such approach may be useful are volcanic systems in subduction zones with their complex magmatic feeding systems that have deep roots in the mantle and intermediate magma chambers in the crust. In these areas, the joint inversion of different types of data helps us to build a comprehensive understanding of the entire system. We apply our algorithm to data collected in the region surrounding the Toba caldera complex (north Sumatra, Indonesia) during two temporary seismic experiments (IRIS, PASSCAL, 1995, GFZ, LAKE TOBA, 2008). We invert 6644 P and 5240 S wave arrivals and ~500 group velocity dispersion curves of Rayleigh and Love waves. We present a series of synthetic tests and real data inversions which show that joint inversion approach gives more reliable results than the separate inversion of two data types. Koulakov, I., LOTOS code for local earthquake tomographic inversion. Benchmarks for testing tomographic algorithms, Bull. seism. Soc. Am., 99(1), 194-214, 2009, doi:10.1785/0120080013

  10. Estudio vulcanológico y qeoquímico del maar de la Caldera del Rey. Tenerife (Canarias

    Directory of Open Access Journals (Sweden)

    Paradas Herrero, A.

    1984-12-01

    Full Text Available In this study a cartographic, morphological, geochemical and petrographic study is made of the ''Caldera del Rey". The "Caldera del Rey" is a volcanic structure formed by two overlapping maars, The second one (maar that was formed is of greaten dimensions and destroyed part of the first one, Both maars erupted throught a possible fracture N 35 E, which is one of the directions with regional importance in the Archipelago. The eruption, which was very explosive, has been thought to be due in part to the great importance of the gaseous phase of the salic magma and also to the steam produced during the interaction of the magma with underground water. This explosivity can be clearly seen in the cleaf resalte cul out in the "Serie Basáltica Antigua" to some extent penetrated and fragmented by the eruption, The phreatomagmatic character of the eruption is evident because of the existence of accretionary lapilli. The materials emitted are exc1usively of aerial projection: agglomerates, tuffs cinerites. There was no flow of lava. ' Some of the fragments of tuffs as cinerites and pumice are comagmatic. These correspond to salic trachytic phonolitic rocks, which represent one of the last stages of differentiation of the alkaline oceanic magmas. The geochemical character of the materials of the "Caldera del Rey" is characteristic and can be easily distinguished from other nearly salic deposits formed in different cycles.

    En este trabajo se hace el estudio cartográfico, morfológico, petrográfico y geoquímico de la Caldera del Rey. La Caldera del Reyes un edificio volcánico formado por dos maars imbricados. El que se formó en segundo lugar es de mayores dimensiones y destruyó en parte el primero. Ambos aprovecharon para hacer erupción una posible fractura de dirección N 35'"E, de importancia regional en el Archipiélago. La erupción fue de una gran explosividad, que se supone debida, en parte, a la gran importancia de la fase gaseosa del

  11. Caldera resurgence as a possible cause of slope failure in volcanic areas: the Ischia island case history

    Science.gov (United States)

    de Vita, Sandro; Seta Marta, Della; Paola, Fredi; Enrica, Marotta; Giovanni, Orsi; Fabio, Sansivero

    2010-05-01

    Slope instability in active volcanic areas is a factor of major hazard to be considered. Due to their rapid growth and deformation, active volcanoes experience gravitational disequilibrium and periodical structural failures. Depending on the geodynamic framework of a volcano, nature, style of activity and climatic conditions, slope instability occurs at different scales, from relatively small-volume mass movements to huge lahars and debris avalanches. Moreover, volcanoes located in coastal areas or islands, may experience lateral collapses with the potential to generate large tsunamis. Although there is very little literature on the relationships among caldera resurgence, volcanism and slope instability, recently also the caldera resurgence has been suggested as a possible cause of slope failure, as for the southern flank of the island of Ischia in the Southern Tyrrhenian sea (Italy). Ischia island gives a good opportunity to investigate such phenomena and related effects, as it is the only documented example of resurgent caldera in which, during uplift, volcanism and generation of mass movements have been very active and linked to each other in a sort of cyclical behaviour. The island of Ischia is one of the most impressive examples of resurgent calderas in the world. This caldera formed in response to a complex explosive eruption that, about 55 ka B.P., produced the Mt. Epomeo Green Tuff ignimbritic deposit. Starting from at least 30 ka B.P. the caldera floor has been uplifted of about 900 m, due to a resurgent phenomenon, which occurred through intermittent uplifting, likely triggered by the intrusion of new magma into the system, and tectonic quietness phases. During uplift, volcanism and generation of mass movements were very active. The resurgent area is composed of differentially displaced blocks and has a poligonal shape, resulting from reactivation of regional faults and activation of faults directly related to volcano-tectonism. The western sector is

  12. Geochemical Similarities Between the Pre-Caldera and Modern Evolutionary Series of Eruptive Products from Gorely Volcano, Kamchatka

    Science.gov (United States)

    Gavrilenko, M.; Ozerov, A.

    2010-12-01

    Gorely volcano, in southern Kamchatka, is a large, long-lived shield-type volcano that is currently in an eruptive phase. Prior eruptions occurred in 1980 and 1984. It is comprised of three structural units: Pra-Gorely volcano; thick ignimbrite complex, associated with a caldera forming eruption; modern edifice named ‘Young Gorely’. An integrated mineralogical-geochemical have been conducted on all structural units of the Gorely volcanic edifice to determine their genetic conditions. After geochemical analysis two evolution series were found. First, Pra-Gorely volcano is represented by a suite of compositions ranging from basalt to rhyolite, with in this series, high-Mg basalts were discovered. Second, Young Gorely edifice is composed of only basalt, andesite and dacite. The reconstruction of chemical evolution trends shows that both volcanic series of Gorely volcano share the same genetic history with similar evolutionary stages. We suggest fractionation of an upper mantle peridotite as a common means to produce both volcanic series as a result of which the evolution of all rocks was generated. The magmatic series of Pra-Gorely and Young Gorely volcanoes were formed under different geodynamic conditions. Between these two series was a powerful stage of caldera formation, during which 100 km3 of ignimbrites were emplaced. The 12-km diameter caldera collapse was the catalyst for large-scale reorganization of the volcanic feeding system. Nevertheless following caldera collapse, Young Gorely was formed by activity inside the caldera and shows very similar evolutionary trends to that of Pra-Gorely. It can be confidently stated that crustal components are practically absent in the evolution of the series, and the compositional range is attributed directly to the evolution of the magmatic melts of Gorely volcano. Microprobe analyses conducted on olivine and pyroxene phenocrysts of Gorely volcano lavas, show that there were at least two stages of crystallization

  13. Real-time monitoring of seismicity and deformation during the Bárdarbunga rifting event and associated caldera subsidence

    Science.gov (United States)

    Jónsdóttir, Kristín; Ófeigsson, Benedikt; Vogfjörd, Kristín; Roberts, Matthew; Barsotti, Sara; Gudmundsson, Gunnar; Hensch, Martin; Bergsson, Bergur; Kjartansson, vilhjálmur; Erlendsson, Pálmi; Friðriksdóttir, Hildur; Hreinsdóttir, Sigrún; Guðmundsson, Magnús; Sigmundsson, Freysteinn; Árnadóttir, Thóra; Heimisson, Elías; Hjorleifsdóttir, Vala; Soring, Jón; Björnsson, Bogi; Oddsson, Björn

    2015-04-01

    We present a monitoring overview of a rifting event and associated caldera subsidence in a glaciated environment during the Bárðarbunga volcanic crisis. Following a slight increase in seismicity and a weak deformation signal, noticed a few months before the unrest by the SIL monitoring team, an intense seismic swarm began in the subglacial Bárðarbunga caldera on August 16 2014. During the following two weeks, a dyke intruded into the crust beneath the Vatnajökull ice cap, propagating 48 km from the caldera to the east-north-east and north of the glacier where an effusive eruption started in Holuhraun. The eruption is still ongoing at the time of writing and has become the largest eruption in over 200 years in Iceland. The dyke propagation was episodic with a variable rate and on several occasions low frequency seismic tremor was observed. Four ice cauldrons, manifestations of small subglacial eruptions, were detected. Soon after the swarm began the 7x11 km wide caldera started to subside and is still subsiding (although at slower rates) and has in total subsided over 60 meters. Unrest in subglacial volcanoes always calls for interdisciplinary efforts and teamwork plays a key role for efficient monitoring. Iceland has experienced six subglacial volcanic crises since modern digital monitoring started in the early 90s. With every crisis the monitoring capabilities, data interpretations, communication and information dissemination procedures have improved. The Civil Protection calls for a board of experts and scientists (Civil Protection Science Board, CPSB) to share their knowledge and provide up-to-date information on the current status of the volcano, the relevant hazards and most likely scenarios. The evolution of the rifting was monitored in real-time by the joint interpretation of seismic and cGPS data. The dyke propagation could be tracked and new, updated models of the dyke volume were presented at the CPSB meetings, often daily. In addition, deformation

  14. Scenario earthquake hazards for the Long Valley Caldera-Mono Lake area, east-central California

    Science.gov (United States)

    Chen, Rui; Branum, David M.; Wills, Chris J.; Hill, David P.

    2014-01-01

    As part of the U.S. Geological Survey’s (USGS) multi-hazards project in the Long Valley Caldera-Mono Lake area, the California Geological Survey (CGS) developed several earthquake scenarios and evaluated potential seismic hazards, including ground shaking, surface fault rupture, liquefaction, and landslide hazards associated with these earthquake scenarios. The results of these analyses can be useful in estimating the extent of potential damage and economic losses because of potential earthquakes and in preparing emergency response plans. The Long Valley Caldera-Mono Lake area has numerous active faults. Five of these faults or fault zones are considered capable of producing magnitude ≥6.7 earthquakes according to the Uniform California Earthquake Rupture Forecast, Version 2 (UCERF 2) developed by the 2007 Working Group of California Earthquake Probabilities (WGCEP) and the USGS National Seismic Hazard Mapping (NSHM) Program. These five faults are the Fish Slough, Hartley Springs, Hilton Creek, Mono Lake, and Round Valley Faults. CGS developed earthquake scenarios for these five faults in the study area and for the White Mountains Fault to the east of the study area. Earthquake scenarios are intended to depict the potential consequences of significant earthquakes. They are not necessarily the largest or most damaging earthquakes possible. Earthquake scenarios are both large enough and likely enough that emergency planners should consider them in regional emergency response plans. Earthquake scenarios presented here are based on fault geometry and activity data developed by the WGCEP, and are consistent with the 2008 Update of the United States National Seismic Hazard Maps (NSHM).For the Hilton Creek Fault, two alternative scenarios were developed in addition to the NSHM scenario to account for different opinions in how far north the fault extends into the Long Valley Caldera. For each scenario, ground motions were calculated using the current standard practice

  15. Manejo de Mercancías Químicas peligrosas en puerto Caldera, Puntarenas, Costa Rica.

    Directory of Open Access Journals (Sweden)

    José Carlos Mora

    2016-03-01

    Full Text Available Puerto Caldera, located in Puntarenas, Costa Rica, is one of the most important Harbors of Central America, which is a key point to transport about 1.5 millions of metric tons of different categories of products every year, including dangerous chemical merchandise. The chemical has have originated emergencies, which has given rise to the necessity to asses load and unload process, and storage. In attention to the matter the most important aspects related to the fulfillment of the national and international norms during the merchandise dangerous transportation in Harbors were evaluated. According to the evaluation of the different handling, storage and transportation processes, Puerto Caldera, face among others the following problems: Personal training necessities addressed to the employees involved in the process of handling dangerous merchandise. Insufficient equipment and materials to guarantee a safe environment. The permanence of merchandise for long periods in warehouse. Unsuitable conditions of warehouse for the proper storage of chemical merchandise. Absence of classification and location criteria of dangerous chemical merchandise in the unloading and loading areas as well as in warehouse. Based up the previous evaluations, the following aspects were developed: An improvement plan for adequate handling of chemical merchandise. Recommendation of specific guidelines to create a Contingencies Plan. The purposes of the two aspects are to promote actions to diminish the risk of accidents associated to the handling of a dangerous merchandise. In the same way, it was proposed a Plan of Improvement and basic lineaments to elaborate a Plan of Contingencies that includes actions to diminish the risk of accidents associated to the handling of dangerous merchandise and to diminish the consequences, in case of accident, as far as the loss of lives, damages to the people, the property and the environment. All this will make Puerto Caldera a safe place

  16. Pyroclastic density current hazard maps at Campi Flegrei caldera (Italy): the effects of event scale, vent location and time forecasts.

    Science.gov (United States)

    Bevilacqua, Andrea; Neri, Augusto; Esposti Ongaro, Tomaso; Isaia, Roberto; Flandoli, Franco; Bisson, Marina

    2016-04-01

    Today hundreds of thousands people live inside the Campi Flegrei caldera (Italy) and in the adjacent part of the city of Naples making a future eruption of such volcano an event with huge consequences. Very high risks are associated with the occurrence of pyroclastic density currents (PDCs). Mapping of background or long-term PDC hazard in the area is a great challenge due to the unknown eruption time, scale and vent location of the next event as well as the complex dynamics of the flow over the caldera topography. This is additionally complicated by the remarkable epistemic uncertainty on the eruptive record, affecting the time of past events, the location of vents as well as the PDCs areal extent estimates. First probability maps of PDC invasion were produced combining a vent-opening probability map, statistical estimates concerning the eruptive scales and a Cox-type temporal model including self-excitement effects, based on the eruptive record of the last 15 kyr. Maps were produced by using a Monte Carlo approach and adopting a simplified inundation model based on the "box model" integral approximation tested with 2D transient numerical simulations of flow dynamics. In this presentation we illustrate the independent effects of eruption scale, vent location and time of forecast of the next event. Specific focus was given to the remarkable differences between the eastern and western sectors of the caldera and their effects on the hazard maps. The analysis allowed to identify areas with elevated probabilities of flow invasion as a function of the diverse assumptions made. With the quantification of some sources of uncertainty in relation to the system, we were also able to provide mean and percentile maps of PDC hazard levels.

  17. 2.8-Ma ash-flow caldera at Chegem River in the northern Caucasus Mountains (Russia), contemporaneous granites, and associated ore deposits

    Science.gov (United States)

    Lipman, P.W.; Bogatikov, O.A.; Tsvetkov, A.A.; Gazis, C.; Gurbanov, A.G.; Hon, K.; Koronovsky, N.V.; Kovalenko, V.I.; Marchev, P.

    1993-01-01

    Diverse latest Pliocene volcanic and plutonic rocks in the north-central Caucasus Mountains of southern Russia are newly interpreted as components of a large caldera system that erupted a compositionally zoned rhyolite-dacite ash-flow sheet at 2.83 ?? 0.02 Ma (sanidine and biotite 40Ar/39Ar). Despite its location within a cratonic collision zone, the Chegem system is structurally and petrologically similar to typical calderas of continental-margin volcanic arcs. Erosional remnants of the outflow Chegem Tuff sheet extend at least 50 km north from the source caldera in the upper Chegem River. These outflow remnants were previously interpreted by others as erupted from several local vents, but petrologic similarities indicate a common origin and correlation with thick intracaldera Chegem Tuff. The 11 ?? 15 km caldera and associated intrusions are superbly exposed over a vertical range of 2,300 m in deep canyons above treeline (elev. to 3,800 m). Densely welded intracaldera Chegem Tuff, previously described by others as a rhyolite lava plateau, forms a single cooling unit, is > 2 km thick, and contains large slide blocks from the caldera walls. Caldera subsidence was accommodated along several concentric ring fractures. No prevolcanic floor is exposed within the central core of the caldera. The caldera-filling tuff is overlain by andesitic lavas and cut by a 2.84 ?? 0.03-Ma porphyritic granodiorite intrusion that has a cooling age analytically indistinguishable from that of the tuffs. The Eldjurta Granite, a pluton exposed low in the next large canyon (Baksan River) 10 km to the northwest of the caldera, yields variable K-feldspar and biotite ages (2.8 to 1.0 Ma) through a 5-km vertical range in surface and drill-hole samples. These variable dates appear to record a prolonged complex cooling history within upper parts of another caldera-related pluton. Major W-Mo ore deposits at the Tirniauz mine are hosted in skarns and hornfels along the roof of the Eldjurta Granite

  18. Persistent inflation at Aira caldera accompanying explosive activity at Sakurajima volcano: Constraining deformation source parameters from Finite Element inversions

    Science.gov (United States)

    Hickey, James; Gottsmann, Jo; Iguchi, Masato; Nakamichi, Haruhisa

    2015-04-01

    Aira caldera is located within Kagoshima Bay at the southern end of Kyushu, Japan. Sakurajima is an active post-caldera andesitic stratovolcano that sits on the caldera's southern rim. Despite frequent Vulcanian-type explosive activity, the area is experiencing continued uplift at a maximum rate of approximately 1.5 cm/yr with a footprint of 40 km, indicating that magma is being supplied faster than it is erupted. This is of particular concern as the amplitude of deformation is approaching the level inferred prior to the 1914 VEI 4 eruption. Using GPS data from 1996 - 2007 we explore causes for the uplift. To solve for the optimum deformation source parameters we use an inverse Finite Element method accounting for three-dimensional material heterogeneity (inferred from seismic tomography) and the surrounding topography of the region. The same inversions are also carried out using Finite Element models that incorporate simplified homogeneous or one-dimensional subsurface material properties, with and without topography. Results from the comparison of the six different models show statistically significant differences in the inferred deformation sources. This indicates that both subsurface heterogeneity and surface topography are essential in geodetic modelling to extract the most realistic deformation source parameters. The current best-fit source sits within a seismic low-velocity zone in the north-east of the caldera at a depth of approximately 14 km with a volume increase of 1.2 x 108 m3. The source location underlies a region of active underwater fumaroles within the Wakamiko crater and differs significantly from previous analytical modelling results. Seismic data further highlights areas of high seismic attenuation as well as large aseismic zones, both of which could allude to inelastic behaviour and a significant heat source at depth. To integrate these observations, subsequent forward Finite Element models will quantify the importance of rheology and

  19. The thermal regime in the resurgent dome of Long Valley Caldera, California: Inferences from precision temperature logs in deep wells

    Science.gov (United States)

    Hurwitz, S.; Farrar, C.D.; Williams, C.F.

    2010-01-01

    Long Valley Caldera in eastern California formed 0.76Ma ago in a cataclysmic eruption that resulted in the deposition of 600km3 of Bishop Tuff. The total current heat flow from the caldera floor is estimated to be ~290MW, and a geothermal power plant in Casa Diablo on the flanks of the resurgent dome (RD) generates ~40MWe. The RD in the center of the caldera was uplifted by ~80cm between 1980 and 1999 and was explained by most models as a response to magma intrusion into the shallow crust. This unrest has led to extensive research on geothermal resources and volcanic hazards in the caldera. Here we present results from precise, high-resolution, temperature-depth profiles in five deep boreholes (327-1,158m) on the RD to assess its thermal state, and more specifically 1) to provide bounds on the advective heat transport as a guide for future geothermal exploration, 2) to provide constraints on the occurrence of magma at shallow crustal depths, and 3) to provide a baseline for future transient thermal phenomena in response to large earthquakes, volcanic activity, or geothermal production. The temperature profiles display substantial non-linearity within each profile and variability between the different profiles. All profiles display significant temperature reversals with depth and temperature gradients temperature in the individual boreholes ranges between 124.7??C and 129.5??C and bottom hole temperatures range between 99.4??C and 129.5??C. The high-temperature units in the three Fumarole Valley boreholes are at the approximate same elevation as the high-temperature unit in borehole M-1 in Casa Diablo indicating lateral or sub-lateral hydrothermal flow through the resurgent dome. Small differences in temperature between measurements in consecutive years in three of the wells suggest slow cooling of the shallow hydrothermal flow system. By matching theoretical curves to segments of the measured temperature profiles, we calculate horizontal groundwater velocities in

  20. Crystallization and eruption ages of Breccia Museo (Campi Flegrei caldera, Italy) plutonic clasts and their relation to the Campanian ignimbrite

    Science.gov (United States)

    Gebauer, Samantha K.; Schmitt, Axel K.; Pappalardo, Lucia; Stockli, Daniel F.; Lovera, Oscar M.

    2014-01-01

    The Campi Flegrei volcanic district (Naples region, Italy) is a 12-km-wide, restless caldera system that has erupted at least six voluminous ignimbrites during the late Pleistocene, including the >300 km3 Campanian ignimbrite (CI) which originated from the largest known volcanic event of the Mediterranean region. The Breccia Museo (BM), a petrologically heterogeneous and stratigraphically complex volcanic deposit extending over 200 km2 in close proximity to Campi Flegrei, has long remained contentious regarding its age and stratigraphic relation to the CI. Here, we present crystallization and eruption ages for BM plutonic ejecta clasts that were determined via uranium decay series and (U-Th)/He dating of zircon, respectively. Despite mineralogical and textural heterogeneity of these syenitic clasts, their U-Th zircon rim crystallization ages are indistinguishable with an average age of 49.7 ± 2.5 ka (2σ errors; mean square of weighted deviates MSWD = 1.2; n = 34). A subset of these crystals was used to obtain disequilibrium-corrected (U-Th)/He zircon ages which average 41.7 ± 1.8 ka (probability of fit P = 0.54; n = 15). This age closely overlaps with published CI 40Ar/39Ar eruption ages (40.6 ± 0.1 ka) after recalibration to recently revised flux monitor ages. Concordant eruption ages for BM and CI agree with previous chemostratigraphic and paleomagnetic correlations, suggesting their origin from the same eruption. However, they are at variance with recalibrated 40Ar/39Ar ages which have BM postdate CI by 3 ± 1 ka. BM syenites show similar geochemical and Sr-Nd isotopical features of pre-caldera rocks erupted between 58 and 46 ka, but are distinctive from subsequent caldera-forming magmas. Energy-constrained assimilation and fractional crystallization modeling of Nd-Sr isotopic data suggests that pre-caldera magmas formed a carapace of BM-type intrusions in a mid-crust magma chamber (≥8 km depth) shielding the younger CI magma from contamination by

  1. Geodetic constraints to the source mechanism of the 2011-2013 unrest at Campi Flegrei (Italy) caldera

    Science.gov (United States)

    Trasatti, Elisa; Polcari, Marco; Bonafede, Maurizio; Stramondo, Salvatore

    2016-04-01

    Campi Flegrei (Italy) is a nested caldera and together with Vesuvius is one of the Italian GEO Geohazard Supersites (GSNL). The area is characterized by one of the highest volcanic hazard of the world, due to the very high density of inhabitants (1800/km²), the persistent activity of the system and the explosive character of volcanism. A major unrest episode took place in 1982-84, when the town of Pozzuoli, located at the caldera center, was uplifted by 1.80 m. Minor uplifts of few centimeters, seismic swarms and degassing episodes took place in 1989, 2000 and 2004-06. Since 2005 Campi Flegrei is uplifting, reaching a ground velocity of 9 cm/yr in 2012, showing that the caldera is in a critical state on the verge of instability. In this work, we present results from SAR Interferometry and geodetic data modelling at Campi Flegrei in the framework of the EU's FP7 MED-SUV Project. We exploit two COSMO-SkyMed data sets to map the deformation field during 2011-2013. The spatial distributions of the cumulative displacement from COSMO-SkyMed ascending/descending orbits show similar behaviors, confirming the bell-shaped pattern of the deformation at least within the inner rim of the caldera. The resulting data, together with GPS data from the Neapolitan Volcanoes Continuous GPS network (NeVoCGPS) is fitted through a geophysical inversion process using finite element forward models to account for the 3D heterogeneous medium. The best fit model is a north dipping mixed-mode dislocation source lying at ~5 km depth. The driving mechanism is ascribable to magma input into the source of the large 1982-1984 unrest (since similar source characteristics were inferred) that generates initial inflation followed by additional shear slip accompanying the extension of crack tips. The history and the current state of the system indicate that Campi Flegrei is able to erupt again. Constraining the defomation source may have important implications in terms of civil protection and the

  2. A 2-D FEM thermal model to simulate water flow in a porous media: Campi Flegrei caldera case study

    Directory of Open Access Journals (Sweden)

    V. Romano

    2012-05-01

    Full Text Available Volcanic and geothermal aspects both exist in many geologically young areas. In these areas the heat transfer process is of fundamental importance, so that the thermal and fluid-dynamic processes characterizing a viscous fluid in a porous medium are very important to understand the complex dynamics of the these areas. The Campi Flegrei caldera, located west of the city of Naples, within the central-southern sector of the large graben of Campanian plain, is a region where both volcanic and geothermal phenomena are present. The upper part of the geothermal system can be considered roughly as a succession of volcanic porous material (tuff saturated by a mixture formed mainly by water and carbon dioxide. We have implemented a finite elements approach in transient conditions to simulate water flow in a 2-D porous medium to model the changes of temperature in the geothermal system due to magmatic fluid inflow, accounting for a transient phase, not considered in the analytical solutions and fluid compressibility. The thermal model is described by means of conductive/convective equations, in which we propose a thermal source represented by a parabolic shape function to better simulate an increase of temperature in the central part (magma chamber of a box, simulating the Campi Flegrei caldera and using more recent evaluations, from literature, for the medium's parameters (specific heat capacity, density, thermal conductivity, permeability. A best-fit velocity for the permeant is evaluated by comparing the simulated temperatures with those measured in wells drilled by Agip (Italian Oil Agency in the 1980s in the framework of geothermal exploration. A few tens of days are enough to reach the thermal steady state, showing the quick response of the system to heat injection. The increase in the pressure due to the heat transport is then used to compute ground deformation, in particular the vertical displacements characteristics of the Campi Flegrei caldera

  3. Modelo para estudios de estabilidad de calderas de recuperación de calor (HRSG) y turbina de vapor

    OpenAIRE

    Corasaniti, Víctor Fabián; Agüero, Jorge Luis; Bianchi Lastra, Raúl E.

    2013-01-01

    En este trabajo se presenta la determinación y validación de los parámetros de un modelo digital para estudios de estabilidad que representa dos Calderas de Recuperación de Calor (HRSG, del inglés Heat Recovery Steam Generator), conjuntamente con la Turbina de Vapor a la cual suministran vapor. Los 2 HRSG producen vapor a partir de los gases de escape de 2 turbinas de gas. El modelo de simulación se implementa en el programa PSS/E (Power System Simulator), programa usado para estudios de est...

  4. Diseño de un sistema de estabilización utilizando sensores inteligentes

    OpenAIRE

    2015-01-01

    Diseño de un sistema de estabilización utilizando sensores inteligentes. This final project proposes the development of an intelligent sensor system low cost based on accelerometers and PICs to create a stabilization system for detecting tilt of a platform. This system will maintain the platform in an equilibrium position, regardless of the movement of the brackets that supports it. Hence, the system will be able to interpret and process the data output by the accelerometer detecting chang...

  5. Simulación y Evaluación de un Esquema de Control Inteligente en una Caldera Industrial Usando Simulink-Edición Única.

    OpenAIRE

    Enrique Arriaga de Valle

    1999-01-01

    En el presente trabajo se modifica y escala un modelo basado en los principios fisicos de funcionamiento de una caldera (Dieck, 1983) para implementar un simulador usando Simulink y evaluar el comportamiento del nivel en el domo. El simulador fue sometido a una doble validación. La primera se hizo reproduciendo en medida de lo posible el comportamiento de la caldera modelada originalmente a fin de ver el efecto de la reducción de estados. Después se cambiaron los parámetros para simular una c...

  6. Gravity changes due to overpressure sources in 3D heterogeneous media: application to Campi Flegrei caldera, Italy

    Directory of Open Access Journals (Sweden)

    M. Bonafede

    2008-06-01

    Full Text Available Employing 3D finite element method, we develop an algorithm to calculate gravity changes due to pressurized sources of any shape in elastic and inelastic heterogeneous media. We consider different source models, such as sphere, spheroid and sill, dilating in elastic media (homogeneous and heterogeneous and in elasto-plastic media. The models are oriented to reproduce the gravity changes and the surface deformation observed at Campi Flegrei caldera (Italy, during the 1982-84 unrest episode. The source shape and the characteristics of the medium have great influence in the calculated gravity changes, leading to very different values for the source densities. Indeed, the gravity residual strongly depends upon the shape of the source. Non negligible contributions also come from density and rigidity heterogeneities within the medium. Furthermore, if the caldera is elasto-plastic, the resulting gravity changes exhibit a pattern similar to that provided by a low effective rigidity. Even if the variation of the source volumes is quite similar for most of the models considered, the density inferred for the source ranges from ? 400 kg/m3 (supercritical water to ? 3300 kg/m3 (higher than trachytic basalts, with drastically different implications for risk assessment.

  7. A GIS-based volcanic hazard and risk assessment of eruptions sourced within Valles Caldera, New Mexico

    Science.gov (United States)

    Alcorn, Rebecca; Panter, Kurt S.; Gorsevski, Pece V.

    2013-11-01

    The objective of this study is to evaluate the spatial extent of a possible future eruption using a GIS-based volcanic hazard tool designed to simulate pyroclastic fallout and density currents (PDCs) as well as lava flows and to assess the social and economic vulnerabilities of the area at risk. Simulated pyroclastic fallout deposits originating from the El Cajete crater within the Valles Caldera, Jemez Mountains volcanic field, New Mexico, are calibrated to isopach and lithic isopleth maps of the Lower and Upper El Cajete as constructed by Wolff et al. (2011). The change in the axial orientation of fallout deposits between the Lower and Upper El Cajete is best matched using seasonal variations in wind speed and direction based on modern atmospheric records. The calibration of PDCs is based on the distribution and run-out of the Battleship Rock Ignimbrite. Once calibrated, hazards are simulated at a second vent location determined from probability distributions of structural features. The resulting hazard simulation maps show the potential distribution of pyroclastic fallout, PDCs and lava flows, indicating areas to the S/SE of Valles Caldera to be at greatest risk.

  8. Investigation of geothermal potential in the Waianae Caldera Area, Western Oahu, Hawaii. Assessment of Geothermal Resources in Hawaii: Number 2

    Energy Technology Data Exchange (ETDEWEB)

    Cox, M.E.; Sinton, J.M.; Thomas, D.M.; Mattice, M.D.; Kauahikaua, J.P.; Helstern, D.M.; Fan, P.

    1979-09-01

    Studies of Lualualei Valley, Oahu have been conducted to determine whether a thermal anomaly exists in the area and, if so, to identify sites at which subsurface techniques should be utilized to characterize the resource. Geologic mapping identifies several caldera and rift zone structures in the Valley and provides a tentative outline of their boundaries. Clay mineralogy studies indicate that minor geothermal alteration of near-surface rocks has occurred at some period in the history of the area. Schlumberger resistivity soundings indicate the presence of a low resistivity layer beneath the valley floor, which has been tentatively attributed to warm water-saturated basalt. Soil and groundwater chemistry studies outline several geochemical anomalies around the perimeter and within the inferred caldera boundaries. The observed anomalies strongly suggest a subsurface heat source. Recommendations for further exploratory work to confirm the presence of a geothermal reservoir include more intensive surveys in a few selected areas of the valley as well as the drilling of at least three shallow (1000-m) holes for subsurface geochemical, geological and geophysical studies.

  9. Geochemical exploration of a promissory Enhanced Geothermal System (EGS): the Acoculco caldera, Mexico.

    Science.gov (United States)

    Peiffer, Loic; Romero, Ruben Bernard; Pérez-Zarate, Daniel; Guevara, Mirna; Santoyo Gutiérrez, Edgar

    2014-05-01

    The Acoculco caldera (Puebla, Mexico) has been identified by the Mexican Federal Electricity Company (in Spanish 'Comisión Federal de Electricidad', CFE) as a potential Enhanced Geothermal System (EGS) candidate. Two exploration wells were drilled and promising temperatures of ~300° C have been measured at a depth of 2000 m with a geothermal gradient of 11oC/100m, which is three times higher than the baseline gradient measured within the Trans-Mexican Volcanic Belt. As usually observed in Hot Dry Rock systems, thermal manifestations in surface are scarce and consist in low-temperature bubbling springs and soil degassing. The goals of this study were to identify the origin of these fluids, to estimate the soil degassing rate and to explore new areas for a future detailed exploration and drilling activities. Water and gas samples were collected for chemical and isotopic analysis (δ18O, δD, 3He/4He, 13C, 15N) and a multi-gas (CO2, CH4, H2S) soil survey was carried out using the accumulation chamber method. Springs' compositions indicate a meteoric origin and the dissolution of CO2 and H2S-rich gases, while gas compositions reveal a MORB-type origin mixed with some arc-type contribution. Gas geothermometry results are similar to temperatures measured during well drilling (260° C-300° C). Amongst all measured CO2 fluxes, only 5% (mean: 5543 g m-2 day-1) show typical geothermal values, while the remaining fluxes are low and correspond to biogenic degassing (mean: 18 g m-2 day-1). The low degassing rate of the geothermal system is a consequence of the intense hydrothermal alteration observed in the upper 800 m of the system which acts as an impermeable caprock. Highest measured CO2 fluxes (above > 600 g m-2 day-1) have corresponding CH4/CO2 flux ratios similar to mass ratios of sampled gases, which suggest an advective fluid transport. To represent field conditions, a numerical model was also applied to simulate the migration of CO2 towards the surface through a

  10. The Askja rockslide and the associated tsunami in the caldera lake

    Science.gov (United States)

    Vogfjörd, Kristin; Kristinn Helgason, Jon; Jonsdottir, Kristin; Brynjolfsson, Sveinn; Grimsdottir, Harpa; Johannesson, Tomas; Hensch, Martin; Ripepe, Maurizio

    2015-04-01

    A large rockslide was released in Askja, central Iceland, on the evening of 21 July 2014 and descended into the caldera lake. It is one of the largest known rockslides since the settlement of Iceland. The release area of the slide is approximately 900 m wide and 350 m above the lake. The front of the landslide travelled at least 2000 m along the lake bottom where it reached the depth of 150 m. The total run-out is approximatly 3100 m and the fall height 500 m. The estimated volume of the slide is estimated as 15-50 million m3. The rockslide appeared as shallow tremor on IMO seismographs near Askja and the data show that the slide was released at 23:24. The slide created seismic waves that travelled over most of Iceland in roughly one minute. In addition, it triggered atmospheric pressure waves that were detected on an infrasound array some 210 km southwest of the event. The infrasound waves travelled this distance in 11 minutes and were reflected in the stratosphere. Photographs from the rockslide area indicate that considerable movement had started a few years before the slide was released. Slow movement in the bedrock seems to have accelerated in the summer of 2014. There was deep snow in the mountains and fairly warm weather before the slide occurred. Percolating water from the melting snow might, thus, have increased the rate of movement. Seismic data indicate that a creeping movement started around 40 minutes before the slide, but at 23:24 the failure point was reached and the rockslide was released. The slide triggered a tsunami in the lake that washed up on the lakeshores all around the lake, reaching up to 20-30 m elevation above the water level and even higher in some places. The wave travelled farthest around 400 m (horizontally) into the flatland SE of the crater Víti. It was fortunate that the rockslide occurred late at night when nobody was close to the water, otherwise it would have been extremely hazardous. A few hours earlier, dozens of people were

  11. Fluidized landslides induced by extreme rainfall along basaltic caldera cliff of Mt. Aso in July 2012

    Science.gov (United States)

    Fukuoka, Hiroshi; Matsushi, Yuki; Furuya, Gen; Saito, Hitoshi

    2013-04-01

    In the end of the rainy season of 2012, a extreme rainfall affected western Japan in July and induced hundreds of fluidized landslides claiming casualties of more than 20. Measured trigger precipitation was recorded by the nearby ground-based station of the AMeDAS network (Automated Meteorological Data Acquisition System)as about 80 mm/h for consecutive 4 hours. Analysis of Radar-Raingauge Analyzed Precipitation-operated by the Japan Meteorological Agency showed landslide affected area almost coincided with the ones of heavier precipitation. Most of the landslides took place along the outer caldera rim and flank of the central cone of Mt. Aso, a basaltic active volcano. Most of the landslides slid on the boundary of strongly weathered soils, which used to be new volcanic accretion materials. Outstanding features of these landslides are: (1) This area had been affected by similar heavy rainfall decades ago, however, again a number of landslides took place in the nearby past scars; (2) Many of the soil slide bodies are shallow less than 5 meters deep and possibly immediately transformed into debris flows or mud flows and traveled long distance to reach the downslope communities; (3) Visual observation of the sources showed the high possibility that some of the slides were apparently induced by liquefaction. Similar cases were reported of past 2 landslide disasters in Japan. This strongly suggests that excessive rainfall can trigger numerous mud flows of unexpected reach. We conducted close field study at a typical soil slide - mud flow site. It originally initiated as debris or soil slide on a thin steep bedding plane of about 34 degrees consisting of coarser accretion materials. Needle penetration test showed comparatively weaker strength in the layer. It is underlain by a layer of finer materials. Such a higher permeability contrast could contribute to higher susceptibility of excess pore pressure generation. We took soil samples from the vicinity of sliding

  12. The Natural and Political Caldera-lake crisis of Mount Pinatubo, Philippines, 2001

    Science.gov (United States)

    Rodolfo, K. S.; Rodolfo, K. S.

    2001-12-01

    In 1991 Mount Pinatubo's eruptions produced a caldera with a 5.4 km2 catchment that ever since has gathered a lake with a surface that has risen roughly 10 m every rainy season. The rim is lowest at 960+ masl in the northwest, at the Maraunot notch, named after the stream into which overtopping lake water would drain, thence along the Balin Baquero and Bucao to the town of Botolan and the South China Sea 40 km downstream. In December 2000, with only 10 m of remaining notch freeboard, Philippine government geologists and American colleagues were aware of the potential for catastrophic breaching, because the surface 20 m of rock beneath the rim is highly erodible breccia. A breakout of as much as 60 x 106 m3 is considered possible. Easily eroded eruption debris is abundant in the path of the flood, which could "bulk up" into worst-case lahars with a volume of 3 x 108 m3. Government engineers discussed lowering the lake with siphons or a tunnel, or scraping down and strengthening the notch, but did nothing. Only in August, three months into a very wet monsoon season, when only about 5 m of freeboard remained, did the government inform the 46,000 Botolan inhabitants of the danger. It did so only after Oxfam GB, a humanitarian organization, issued a report written by private geological consultants familiar with Pinatubo and its lahars. The crisis, still evolving, unfortunately is pitting government attitudes and policies -- strict control of information and decisions regarding hazards -- against those of academic science, and of some NGOs concerned with community development and empowerment. In August, the government abruptly abandoned its initial denials of a serious threat, and decided to build a canal with which to induce a breach at a propitious time. Poorly paid and supervised aborigine labor has inadvertently reduced the freeboard to only 2 m, and the government is announcing that it will evacuate Botolan and induce the breach as early as September 5. Spontaneous

  13. Near real-time monitoring of surface deformation at Long Valley Caldera, California (Invited)

    Science.gov (United States)

    Ji, K.; Llenos, A. L.; Herring, T.

    2013-12-01

    Continuous monitoring of volcanic activity enables us to detect changes from usual activity, issue alerts of impending eruptions and thereby reduce volcanic risk. We have developed a near real-time monitoring tool for surface deformation: the Targeted Projection Operator (TPO). TPO is simple, fast, and easily applied whenever new data are available. With Global Positioning System (GPS) data, we have used TPO for continuous monitoring of surface deformation in the Long Valley Caldera (LVC) region in eastern California. TPO projects GPS position time series onto a target spatial pattern and obtains the amplitude of the projection at each epoch. For this, we assume that a deformation event (i.e., an inflationary or deflationary event) has the same spatial pattern as past events but with possibly different amplitude. This assumption is reasonable for the recent quiet phase in LVC because the 2007-2009 inflation is similar to the 2009-2010 deflation with respect to the deformation pattern. We selected horizontal pattern of the 2009-2010 event along which the GPS data are projected to recover the time-varying amplitudes. Large changes in amplitude imply changes in strength of the event. An anomalous change can be detected by comparing with amplitudes during relatively quiet time periods. Growing misfits between the TPO spatial pattern and the spatial variations of the GPS pattern, indicate changes in the deformation mechanism which can then be explored to assess whether potentially new mechanisms are developing. So far this has not been the case for LVC; the current spatial patterns of deformation match the shape deduced for the 2007-2009 inflation event. TPO shows that LVC has experienced inflation since late 2011 although the rate briefly slowed down in May and October 2012 and has started to slow again since June 2013. The rate of this event is about four times faster than the 2007-2009 inflation event and is consistent with a Mogi source located beneath the resurgent

  14. Lithology, Geochemistry and Paleomagnetism of the Table Mountain Formation at the Little Walker Caldera

    Science.gov (United States)

    Schubert, R.; Pluhar, C. J.; Carlson, C. W.; Jones, S. A.

    2015-12-01

    West of Bridgeport Valley near the Central Sierra Nevada crest, the Little Walker Caldera (LWC) erupted Stanislaus Group lavas and tuffs during the Late Miocene. Remnants of these rocks are now distributed from the western Sierra Nevada foothills across the range and into the Walker Lane. This wide distribution is attributed to the lavas flowing down paleochannels, which provide an excellent marker for deformation over the last 10 Ma. Priest (1978) identified a thick section of these lavas along Flatiron Ridge, the southeast margin of the LWC, which our preliminary data suggests may correlate with lavas in the Sweetwater Mountains to the northeast and at Rancheria Mtn near Hetch Hetchy to the southwest. The oldest unit in the Stanislaus group is the Table Mountain Formation, a trachyandesite. At Priest's measured section it is divided into three members. By our measurements, the Lower Member (Tmtl) is 256 meters thick, has a fine-grained groundmass with plagioclase and augite phenocrysts (<0.5 cm), and the presence of augite phenocrysts distinguishes it from the other members. Some Tmtl flows have chalcedony amigdules. Overlying this, the Large Plagioclase member (Tmtp) is 43.5 meters thick. Distinguished by (~1 cm) plagioclase and occasional small olivine phenocrysts. The Upper Member (Tmtu) is 116 meters thick, very fine-grained and often platy. Tmtl has a distinctive northwest-oriented normal polarity and geochemistry, similar to several localities at Rancheria Mtn. Tmtu has a reversed polarity similar to the polarity of Table Mountain Formation in the Sweetwater Mountains and lavas that directly underlie the ~9.5 Ma Tollhouse Flat member of the Eureka Valley Tuff at Rancheria Mtn. Thus, our preliminary data suggest that the lower member at Priest's Measured Section could correlate to the normal polarity samples at Rancheria Mtn. Also, that the upper Member reversed-polarity samples may correlate with lavas both at the Sweetwater Mountains and Rancheria Mtn

  15. LA OPULENCIA EN LA ESCASEZ. INTERCAMBIOS DE OBJETOS, RELACIONES SOCIALES Y AMBIGÜEDADES EN INSTITUTOS CORRECCIONALES DE CÓRDOBA / Opulence on scarcity. Exchange of objects, social relations and ambiguities in correctional institutes of Córdoba

    Directory of Open Access Journals (Sweden)

    Graciela María Tedesco

    2009-12-01

    Full Text Available Este artículo se propone reflexionar sobre las relaciones sociales que se entrelazan durante el proceso de dar, recibir, intercambiar distintos objetos en institutos correccionales de la ciudad de Córdoba. A través del análisis de situaciones como “la visita”, “el arreglo de las habitaciones”, “el fumar y compartir en el sector”; se analizan formas de tejer vínculos con el afuera, actualizar recuerdos sobre la calle, y de producir intercambios y reforzar ciertos valores dentro del grupo que convive en el instituto. La descripción de estas situaciones implica asimismo, indagar los mecanismos y circuitos a través de los cuales se incorporan distintos sentidos a los objetos, así como también, el modo en que éstos configuran la subjetividad de las personas. De esta manera, el artículo busca mostrar la dinámica que lleva a que, en contextos institucionales marcados por privación y escasez, los jóvenes generen diversos intercambios y utilicen la ambigüedad como un medio para un construir abundancia y poder.Palabras clave: jóvenes, institutos correccionales, relaciones sociales, objetosAbstractThis article proposes to reflect on the social relations that are intertwined in the process of giving, receiving, exchanging various objects in correctional institutes in the city of Córdoba. Across the analysis of situations as “the visit”, “the arrangement of the bedroom”, “to smoke and share in the sector”; discusses ways to weave ties to the outside, upgrade memory on the street and produce exchanges and strengthen certain values within the group that lives in institute. The description of these situations also means, investigate the mechanisms and circuits through which incorporate different meanings to objects, and also, they shape the subjectivity of people. Thus, the article shows the dynamics means that, in institutional contexts marked by deprivation and scarcity, young men exchanges and use the ambiguity, as a

  16. The Project Serapis: High Resolution Seismic Imagingof The Campi Flegrei Caldera Structure

    Science.gov (United States)

    Zollo, A.; Virieux, J.; Capuano, P.; Chiarabba, C.; de Franco, R.; Makris, J.; Michelini, A.; Musacchio, G.; Serapis Group

    expected NE-SW and SE-NW structural trends and it has been designed to get 2D/3D images of the crustal structure at a regional scale. A denser 2D network of 35 OBSs has been deployed in the bay of Pozzuoli aimed at detecting and modeling reflected/converted waves from 1 the possible shallow to deep discontinuities beneath the Campi Flegrei caldera. The main target of this particular receiver lay-out is the detailed imaging of the magma chamber top, expected at 4-5 km depth, according to temperature measurements in wells and sparse seismic observations. About 5000 shots have been performed dur- ing the SERAPIS experiment, at an average spatial spacing of 125 m, for a total ship travel path of 620 km. All of the seismic lines have been re-sampled at least twice, using a staggered configuration, which results in a smaller source spacing (less than 65m). In the gulf of Pozzuoli the source array had a geometry of a 5x5 km grid, slightly shifted south with respect to the OBS array. Seismic signals produced by air- guns have been well detected up to 50-60 km distance and the whole Campi Flegrei, Ischia and Procida on-land networks have recorded high quality seismograms pro- duced by the gridded source array in the bay of Pozzuoli. Due to the extended and very dense source and receiver arrays used for SERAPIS, this campaign can provide an innovative contribution to the accurate reconstruction of the Campi Flegrei caldera structure and to the definition of its feeding system at depth. *SERAPIS group: Auger Emmanuel, Bernard Marie-Lise, Bobbio Antonella, Bonagura Mariateresa, Cantore Luciana, Convertito Vincenzo, D'Auria Luca, De Matteis Raffaella, Emolo Anto- nio, Festa Gaetano, Gasparini Paolo, Giberti Grazia, Herrero Andre, Improta Luigi, Lancieri Maria Flora, Nielsen Stefan, Nisii Vincenzo, Russo Guido, Satriano Clau- dio, Simini Mariella, Vassallo Maurizio, Bruno Pier Paolo, Buonocunto Ciro, Capello Marco, Del Pezzo Edoardo, Galluzzo Danilo, Gaudiosi Germana, Giuliana Alessio

  17. The earliest low and high δ18O caldera-forming eruptions of the Yellowstone plume: Implications for the 30–40 Ma Oregon calderas and speculations on plume-triggered delaminations

    Directory of Open Access Journals (Sweden)

    Angela Nicole Seligman

    2014-11-01

    Full Text Available We present new isotopic and trace element data for four eruptive centers in Oregon: Wildcat Mountain (40 Ma, Crooked River (32–28 Ma, Tower Mountain (32 Ma, and Mohawk River (32 Ma. The first three calderas are located too far east to be sourced through renewed subduction of the Farallon slab following accretion of the Yellowstone-produced Siletzia terrane at ~50 Ma. Basalts of the three eastern eruptive centers yield high Nb/Yb and Th/Yb ratios, indicating an enriched sublithospheric mantle source, while Mohawk River yields trace element and isotopic (δ18O and εHf values that correlate with its location above a subduction zone. The voluminous rhyolitic tuffs and lavas of Crooked River (41 x 27 km have δ18Ozircon values that include seven low δ18Ozircon units (1.8–4.5 ‰, one high δ18Ozircon unit (7.4–8.8 ‰, and two units with heterogeneous zircons (2.0–9.0 ‰, similar to younger Yellowstone-Snake River Plain rhyolites. In order to produce these low δ18O values, a large heat source, widespread hydrothermal circulation, and repeated remelting are all required. In contrast, Wildcat Mountain and Tower Mountain rocks yield high δ18Ozircon values (6.4–7.9 ‰ and normal to low εHfi values (5.2–12.6, indicating crustal melting of high-δ18O supracrustal rocks. We propose that these calderas were produced by the first appearance of the Yellowstone plume east of the Cascadia subduction zone, which is supported by plate reconstructions that put the Yellowstone plume under Crooked River at 32–28 Ma. Given the eastern location of these calderas along the suture of the accreted Siletzia terrane and North America, we suggest that the Yellowstone hotspot is directly responsible for magmatism at Crooked River, and for plume-assisted delamination of portions of the edge of the Blue Mountains that produced the Tower Mountain magmas, while the older Wildcat Mountain magmas are related to suture zone instabilities that were created

  18. The earliest low and high δ18O caldera-forming eruptions of the Yellowstone plume: Implications for the 30-40 Ma Oregon calderas and speculations on plume-triggered delaminations

    Science.gov (United States)

    Seligman, Angela; Bindeman, Ilya; McClaughry, Jason; Stern, Richard; Fisher, Chris

    2014-11-01

    We present new isotopic and trace element data for four eruptive centers in Oregon: Wildcat Mountain (40 Ma), Crooked River (32-28 Ma), Tower Mountain (32 Ma), and Mohawk River (32 Ma). The first three calderas are located too far east to be sourced through renewed subduction of the Farallon slab following accretion of the Yellowstone-produced Siletzia terrane at ~50 Ma. Basalts of the three eastern eruptive centers yield high Nb/Yb and Th/Yb ratios, indicating an enriched sublithospheric mantle source, while Mohawk River yields trace element and isotopic (δ18O and ɛHf) values that correlate with its location above a subduction zone. The voluminous rhyolitic tuffs and lavas of Crooked River (41 x 27 km) have δ18Ozircon values that include seven low δ18Ozircon units (1.8-4.5 ‰), one high δ18Ozircon unit (7.4-8.8 ‰), and two units with heterogeneous zircons (2.0-9.0 ‰), similar to younger Yellowstone-Snake River Plain rhyolites. In order to produce these low δ18O values, a large heat source, widespread hydrothermal circulation, and repeated remelting are all required. In contrast, Wildcat Mountain and Tower Mountain rocks yield high δ18Ozircon values (6.4-7.9 ‰) and normal to low ɛHfi values (5.2-12.6), indicating crustal melting of high-δ18O supracrustal rocks. We propose that these calderas were produced by the first appearance of the Yellowstone plume east of the Cascadia subduction zone, which is supported by plate reconstructions that put the Yellowstone plume under Crooked River at 32-28 Ma. Given the eastern location of these calderas along the suture of the accreted Siletzia terrane and North America, we suggest that the Yellowstone hotspot is directly responsible for magmatism at Crooked River, and for plume-assisted delamination of portions of the edge of the Blue Mountains that produced the Tower Mountain magmas, while the older Wildcat Mountain magmas are related to suture zone instabilities that were created following accretion of the

  19. Ambient seismic noise tomography reveals a hidden caldera and its relation to the Tarutung pull-apart basin at the Sumatran Fault Zone, Indonesia

    Science.gov (United States)

    Ryberg, Trond; Muksin, Umar; Bauer, Klaus

    2016-07-01

    We analyzed the noise recordings of a short-period seismic network to derive a shallow crustal S-wave velocity model at the Sumatra Fault in Northern Sumatra, Indonesia. By correlating the noise of 40 seismic stations' recording for 9 months, we could recover Rayleigh waves from vertical component recordings with sufficient signal-to-noise ratio. Group velocities of the Rayleigh waves could be determined in the period range from 0.71 to 4.4 s. These group velocities were used to invert for 2D group velocity maps at specific periods. Finally, the derived group velocity maps were inverted for a 3D S-wave velocity model. This model shows a region of a strong velocity decrease off the Great Sumatran Fault Zone, at the northeastern margin of the young Tarutung pull-apart basin. This observed low velocity block coincides with a caldera-like morphological feature which is interpreted as the surface expression of a hidden volcanic caldera. Considering the surface manifestations of geothermal activity around this anomaly, we conclude that the caldera is still acting as a heat source. On the other hand, the weak morphological expression at the surface indicates a certain age of the caldera which might be older than the Tarutung pull-apart basin. The findings provide important constraints on general concepts for the formation of pull-apart basins along the Sumatran fault and their relation to volcanism.

  20. Tephra dispersal during the Campanian Ignimbrite (Italy) eruption: implications for ultra-distal ash transport during the large caldera-forming eruption

    Science.gov (United States)

    Smith, Victoria C.; Isaia, Roberto; Engwell, Sam L.; Albert, Paul. G.

    2016-06-01

    The Campanian Ignimbrite eruption dispersed ash over much of the central eastern Mediterranean Sea and eastern Europe. The eruption started with a Plinian phase that was followed by a series of pyroclastic density currents (PDCs) associated with the collapse of the Plinian column and the caldera. The glass compositions of the deposits span a wide geochemical range, but the Plinian fallout and PDCs associated with column collapse, the Lower Pumice Flow, only erupted the most evolved compositions. The later PDCs, the Breccia Museo and Upper Pumice Flow, erupted during and after caldera collapse, tap a less evolved component, and intermediate compositions that represent mixing between the end-members. The range of glass compositions in the Campanian Ignimbrite deposits from sites across the central and eastern Mediterranean Sea allow us to trace the dispersal of the different phases of this caldera-forming eruption. We map the fallout from the Plinian column and the plumes of fine material associated with the PDCs (co-PDCs) across the entire dispersal area. This cannot be done using the usual grain-size methods as deposits in these distal regions do not retain characteristics that allow attribution to either the Plinian or co-PDC phases. The glass compositions of the tephra at ultra-distal sites (>1500 km from the vent) match those of the uppermost PDC units, suggesting that most of the ultra-distal dispersal was associated with the late co-PDC plume that was generated during caldera collapse.

  1. A tale of ambiguities and interpretation pitfalls: seismology based source models for the Bárðarbunga caldera collapse earthquakes, Iceland

    Science.gov (United States)

    Heimann, Sebastian; Cesca, Simone; Hensch, Martin; Dahm, Torsten; Hjörleifsdóttir, Vala

    2016-04-01

    The 2014-2015 collapse of the Bárðarbunga caldera was accompanied by a notable seismic sequence of more than 80 events with Mw >= 4.5. We analyse these earthquakes using broadband recordings from the Icelandic regional seismic network using standard and probabilistic centroid moment tensor inversion. Our results reveal that the centroids of the events cluster beneath the northern and southern caldera rims and are characterized by the superposition of a near-vertical negative compensated linear vector dipole (CLVD) and shear faulting of different orientations. It is well known that moment tensor decompositions are non-unique. We demonstrate that in this particular case, applying the standard moment tensor decomposition scheme would lead to wrong conclusions, incompatible with independent observations like the fault orientations at the caldera rims. We propose an alternative decomposition scheme which is well compatible with the observations. Furthermore, we propose a simple mechanical model for asymmetric, drainage-driven caldera collapses, capable of explaining the seismological observations at regional distances: an initial failure along a steep fault is followed by a deformation response of a deeper magmatic source. The shear faulting contribution occurs either as thrust faulting along an outward dipping fault (northern rim) or as normal faulting along an inward dipping fault (southern rim). As a side note, we discuss the parameter trade-offs in our full and deviatoric centroid moment tensor inversion problems and show how to rigorously quantify uncertainties on the results.

  2. Keanakākoʻi Tephra produced by 300 years of explosive eruptions following collapse of Kīlauea's caldera in about 1500 CE

    Science.gov (United States)

    Swanson, Donald A.; Rose, Timothy R.; Fiske, Richard S.; McGeehin, John P.

    2012-01-01

    The Keanakākoʻi Tephra at Kīlauea Volcano has previously been interpreted by some as the product of a caldera-forming eruption in 1790 CE. Our study, however, finds stratigraphic and 14C evidence that the tephra instead results from numerous eruptions throughout a 300-year period between about 1500 and 1800. The stratigraphic evidence includes: (1) as many as six pure lithic ash beds interleaved in sand dunes made of earlier Keanakākoʻi vitric ash, (2) three lava flows from Kīlauea and Mauna Loa interbedded with the tephra, (3) buried syneruptive cultural structures, (4) numerous intraformational water-cut gullies, and (5) abundant organic layers rich in charcoal within the tephra section. Interpretation of 97 new accelerator mass spectrometry (AMS) 14C ages and 4 previous conventional ages suggests that explosive eruptions began in 1470–1510 CE, and that explosive activity continued episodically until the early 1800s, probably with two periods of quiescence lasting several decades. Kīlauea's caldera, rather than forming in 1790, predates the first eruption of the Keanakākoʻi and collapsed in 1470–1510, immediately following, and perhaps causing, the end of the 60-year-long, 4–6 km3 ʻAilāʻau eruption from the east side of Kīlauea's summit area. The caldera was several hundred meters deep when the Keanakākoʻi began erupting, consistent with oral tradition, and probably had a volume of 4–6 km3. The caldera formed by collapse, but no eruption of lava coincided with its formation. A large volume of magma may have quickly drained from the summit reservoir and intruded into the east rift zone, perhaps in response to a major south-flank slip event, leading to summit collapse. Alternatively, magma may have slowly drained from the reservoir during the prolonged ʻAilāʻau eruption, causing episodic collapses before the final, largest downdrop took place. Two prolonged periods of episodic explosive eruptions are known at Kīlauea, the Keanak

  3. Dynamics of the 2007 Eruptions of Piton de la Fournaise and the Related Caldera Collapse from a Single Very Broad-band Seismic Station

    Science.gov (United States)

    Fontaine, Fabrice R.; Roult, Geneviève; Michon, Laurent; Barruol, Guilhem; Ferrazzini, Valérie; Di Muro, Andrea; Reymond, Dominique; Peltier, Aline; Staudacher, Thomas

    2014-05-01

    Seismic records from the RER very broad-band seismic station (La Réunion Island) belonging to the GEOSCOPE network are investigated to understand the eruptive succession (February to May) of Piton de la Fournaise and the caldera collapse episode of April 2007. Data first indicate that the short-lived, small volume, summit eruption of February 18 occurred during a phase of continuous inflation initiated in January 2007. Inflation decelerated around 2 weeks before a second short-lived small volume eruption on March 30-31 on the SE flank, almost simultaneous with a sudden, large deflation of the edifice. Deflation rate, which had stabilized at a relatively low level, increased anew on April 1 while no magma was emitted, followed on April 2 by a more distant and one of the most voluminous eruptions of the last two centuries at La Réunion Island. The RER station shows that very long period (VLP) and ultra long period (ULP) events developed during this period. Seven ULP events preceded the caldera collapse and 48 ones occurred during the caldera collapse over 9 days, most of which during the first 30 hours. A thorough examination of the seismic signals corrected for tide effects shows that each collapse event was coeval with VLP and ULP signals. Each individual collapse showed similar ULP and VLP signals characterized by periods of ~ 500 s and ~ 7 s, respectively. The back-azimuth of most ULP signals related to the caldera collapse points clearly toward the Dolomieu caldera. The strikingly constant duration of the VLP signals (around 20 s) related to the collapse events and their occurrence before the collapse initiation suggest a physical control of the volcanic edifice. Waveforms and spectrograms of the various caldera collapse events show very homogeneous patterns, suggesting a similar and repeating volcano-tectonic process for the formation of the VLP signals events. Although tilt may be responsible of part of the ULP signals observed during the collapse events, we

  4. Sistemas microfluídicos amperométricos utilizando enzimas imobilizadas

    OpenAIRE

    Luís Marcos Cerdeira Ferreira

    2011-01-01

    Este trabalho descreve o desenvolvimento de um sistema microfluídico, contendo, como componente principal, um reator enzimático constituído de um microcanal fabricado em substrato de poli(metacrilato de metila) e um sistema amperométrico como detector. Para a construção de microcanais foi utilizando equipamento de usinagem a laser de CO2 para escavar os microcanais, que a seguir foram selados termicamente. A superfície interna desse microcanal foi submetida à modificação química com poli(etil...

  5. Monitoramento dos extratos brutos de espécies de Polygala (Polygalaceae utilizando Artemia salina

    Directory of Open Access Journals (Sweden)

    A.B.P. Montanher

    2003-01-01

    Full Text Available Extratos de duas espécies de Polygala foram submetidos a um biomonitoramento utilizando o teste de toxicidade frente a Artemia salina, com a finalidade de detectar atividade citotóxica. Os resultados obtidos para o extrato bruto, frações hexânica e diclorometano de Polygala sabulosa Aw. Benn. mostraram-se promissores. No entanto, bioensaios mais específicos devem ser encorajados nos extratos vegetais que apresentam atividade diante deste bioensaio, a fim de confirmar estas conclusões.

  6. Clasificación de los elementos de una muestra de sangre utilizando Redes Neuronales

    OpenAIRE

    Lanzarini, Laura Cristina; Vargas Camacho, María Teresa; Badrán, Amado F.; De Giusti, Armando Eduardo

    1996-01-01

    El análisis de una muestra de sangre es una de las prácticas más comunes solicitadas por los médicos para un diagnóstico y pronóstico adecuados. Mediante su estudio es posible detectar distintas. patologías que van desde los más simples procesos fisiológicos o inflamatorios a los más complejos procesos neoplásicos (leucemias) y de allí su importancia. El presente trabajo es una aplicación de reconocimiento de patrones utilizando redes neuronales actualmente en desarrollo, que permite clasi...

  7. Desarrollo de apio minimamente procesado fortificado con vitamina e, utilizando la ingenieria de matrices

    OpenAIRE

    YISELL JOHAN MARTELO CASTAÑO; MISAEL CORTES RODRIGUEZ; HÉCTOR SUAREZ MAHECHA

    2011-01-01

    El objetivo de este trabajo fue desarrollar un producto minimamente procesado fortificado con vitamina E, a partir de apio (Apium graveolens L. var.dulce), utilizando la ingenieria de matrices como metodologia de obtencion de alimentos funcionales. Trozos de apio impregnados al vacio con dl¿¿tocoferol acetato emulsificado en una solucion isotonica al vegetal de NaCl, 1,2%, fueron evaluados en funcion del tiempo de almacenamiento y el envasado (con y sin vacio), en terminos de la cuantificacio...

  8. Productividad en una celda de manufactura flexible simulada en promodel utilizando path networks type crane

    OpenAIRE

    María Elena Bernal Loaiza; German Cock Sarmiento; Jorge Hernán Restrepo Correa

    2015-01-01

    Esta investigación se centra en el diseño de una simulación del proceso de una celda de manufactura flexible (FMC) de la Facultad de Ingeniería Industrial de la Universidad Tecnológica de Pereira, con el propósito de medir y elegir aquella alternativa de solución que mejore en mayor grado la productividad del sistema actual utilizando los resultados que proporciona el software Promodel. Para realizar lo anterior se utilizaron etapas de la simulación como definición del sistema, formulación de...

  9. Seguimiento de la reactogenicidad de la vacuna DTP cubana, utilizando dos métodos paralelos

    OpenAIRE

    María de los Ángeles Peña Machado; Telma María Triana Rodríguez; Jorge Menéndez Hernández; Mayelin Mirabal Sosa; Marlen Armesto del Río; Morelia Baró Suárez; Lorenzo la Rosa Ocampo; Marlen Raymundo Valdés; Liudmila Ibelin Egües Torres; Giset Jiménez López

    2005-01-01

    Con el objetivo de caracterizar la reactogenicidad de la vacuna Antidiftérica-Antitetánica- Antipertusis (DTP) cubana, desarrollada por el Instituto Finlay, se realizó un estudio utilizando dos métodos o fuentes de información diferentes y paralelos. La primera se obtuvo de un ensayo clínico (EC) Fase IV, abierto, no controlado, en el que se incluyeron 57 lactantes. La segunda fuente de información se obtuvo de los reportes de los eventos temporalmente asociados a la vacunación (ETAV), recepc...

  10. The effect of pressurized magma chamber growth on melt migration and pre-caldera vent locations through time at Mount Mazama, Crater Lake, Oregon

    Science.gov (United States)

    Karlstrom, Leif; Wright, Heather M.; Bacon, Charles R.

    2015-01-01

    The pattern of eruptions at long-lived volcanic centers provides a window into the co-evolution of crustal magma transport, tectonic stresses, and unsteady magma generation at depth. Mount Mazama in the Oregon Cascades has seen variable activity over the last 400 ky, including the 50 km3 climactic eruption at ca. 7.7 ka that produced Crater Lake caldera. The physical mechanisms responsible for the assembly of silicic magma reservoirs that are the precursors to caldera-forming eruptions are poorly understood. Here we argue that the spatial and temporal distribution of geographically clustered volcanic vents near Mazama reflects the development of a centralized magma chamber that fed the climactic eruption. Time-averaged eruption rates at Mount Mazama imply an order of magnitude increase in deep magma influx prior to the caldera-forming event, suggesting that unsteady mantle melting triggered a chamber growth episode that culminated in caldera formation. We model magma chamber–dike interactions over ∼50 ky preceding the climactic eruption to fit the observed distribution of surface eruptive vents in space and time, as well as petrologically estimated deep influx rates. Best fitting models predict an expanding zone of dike capture caused by a growing, oblate spheroidal magma chamber with 10–30 MPa of overpressure. This growing zone of chamber influence causes closest approaching regional mafic vent locations as well as more compositionally evolved Mazama eruptions to migrate away from the climactic eruptive center, returning as observed to the center after the chamber drains during the caldera-forming eruption.

  11. The eruptive history and chemical stratigraphy of a post-caldera, steady-state volcano: Yasur, Vanuatu

    Science.gov (United States)

    Firth, Chris W.; Handley, Heather K.; Cronin, Shane J.; Turner, Simon P.

    2014-07-01

    The persistent activity of Yasur volcano, a post-caldera scoria cone in the southern Vanuatu Arc, along with the uniformity exhibited by its eruptive products, indicates that it is a "steady-state" volcano. This implies that rates of magma replenishment and tapping are in equilibrium. Examination of recently exposed tephra sequences suggests that Strombolian-style activity at Yasur has persisted in its current form for the last 630-850 years. Eruption of tephra with uniform grain size and texture throughout this period indicates invariant eruption magnitude and style. Based on tephra accumulation rates, a uniform, time-averaged eruption flux of ˜410-480 m3 days-1 is estimated. Major and trace element analyses of glass shards and mineral grains from these tephra deposits show limited variation in magma composition throughout that time, consistent with a chemically buffered magma reservoir and models for steady-state volcanism. Similarly, mineral crystallisation temperature estimates are within error, suggesting the magma reservoir has retained a constant temperature through this time, while pressure estimates suggest shallow crystallisation. Eruptions appear to be driven by gas release, with small fluctuations in magma chemistry and eruptive behaviour governed by perturbations in volatile flux. This period of steady-state activity was preceded by ˜600 years of higher-magnitude, lower-frequency eruptions during which less evolved compositions were erupted. Variation between these two styles of eruptive behaviour may be explained by a shift from a periodically closed to fully opened conduit, allowing more regular magma release and changes to degassing regimes. New radiocarbon ages suggest a period of irregular eruptive behaviour extending >1,400 year B.P. Overall, a transition from an irregular to a very steady magmatic system has occurred over the past ˜2 kyr. Previously determined tectonic indicators for caldera resurgence in the area suggest revived magma

  12. Numerical models for ground deformation and gravity changes during volcanic unrest: simulating the hydrothermal system dynamics of a restless caldera

    Science.gov (United States)

    Coco, A.; Gottsmann, J.; Whitaker, F.; Rust, A.; Currenti, G.; Jasim, A.; Bunney, S.

    2016-04-01

    Ground deformation and gravity changes in restless calderas during periods of unrest can signal an impending eruption and thus must be correctly interpreted for hazard evaluation. It is critical to differentiate variation of geophysical observables related to volume and pressure changes induced by magma migration from shallow hydrothermal activity associated with hot fluids of magmatic origin rising from depth. In this paper we present a numerical model to evaluate the thermo-poroelastic response of the hydrothermal system in a caldera setting by simulating pore pressure and thermal expansion associated with deep injection of hot fluids (water and carbon dioxide). Hydrothermal fluid circulation is simulated using TOUGH2, a multicomponent multiphase simulator of fluid flows in porous media. Changes in pore pressure and temperature are then evaluated and fed into a thermo-poroelastic model (one-way coupling), which is based on a finite-difference numerical method designed for axi-symmetric problems in unbounded domains.Informed by constraints available for the Campi Flegrei caldera (Italy), a series of simulations assess the influence of fluid injection rates and mechanical properties on the hydrothermal system, uplift and gravity. Heterogeneities in hydrological and mechanical properties associated with the presence of ring faults are a key determinant of the fluid flow pattern and consequently the geophysical observables. Peaks (in absolute value) of uplift and gravity change profiles computed at the ground surface are located close to injection points (namely at the centre of the model and fault areas). Temporal evolution of the ground deformation indicates that the contribution of thermal effects to the total uplift is almost negligible with respect to the pore pressure contribution during the first years of the unrest, but increases in time and becomes dominant after a long period of the simulation. After a transient increase over the first years of unrest

  13. Numerical models for ground deformation and gravity changes during volcanic unrest: simulating the hydrothermal system dynamics of an active caldera

    Directory of Open Access Journals (Sweden)

    A. Coco

    2015-08-01

    Full Text Available Ground deformation and gravity changes in active calderas during periods of unrest can signal an impending eruption and thus must be correctly interpreted for hazard evaluation. It is critical to differentiate variation of geophysical observables related to volume and pressure changes induced by magma migration from shallow hydrothermal activity associated with hot fluids of magmatic origin rising from depth. In this paper we present a numerical model to evaluate the thermo-poroelastic response of the hydrothermal system in a caldera setting by simulating pore pressure and thermal expansion associated with deep injection of hot fluids (water and carbon dioxide. Hydrothermal fluid circulation is simulated using TOUGH2, a multicomponent multiphase simulator of fluid flows in porous media. Changes in pore pressure and temperature are then evaluated and fed into a thermo-poroelastic model (one-way coupling, which is based on a finite-difference numerical method designed for axi-symmetric problems in unbounded domains. Based on data for the Campi Flegrei caldera (Italy, a series of simulations assess the influence of fluid injection rates and mechanical properties on the hydrothermal system, uplift and gravity. Heterogeneities in hydrological and mechanical properties associated with the presence of ring faults are a key determinant of the fluid flow pattern and consequently the geophysical observables. Peaks (in absolute value of uplift and gravity change profiles computed at the ground surface are located close to injection points (namely at the centre of the model and fault areas. Temporal evolution of the ground deformation indicates that the contribution of thermal effects to the total uplift is almost negligible with respect to the pore pressure contribution during the first years of the unrest, but increases in time and becomes dominant after a long period of the simulation. After a transient increase over the first years of unrest, gravity

  14. P, S velocity and VP/VS ratio beneath the Toba caldera complex (Northern Sumatra) from local earthquake tomography

    Science.gov (United States)

    Koulakov, Ivan; Yudistira, Tedi; Luehr, Birger-G.; Wandono

    2009-06-01

    In this paper, we investigate the crustal and uppermost mantle structure beneath Toba caldera, which is known as the location of one of the largest Cenozoic eruptions on Earth. The most recent event occurred 74000 yr BP, and had a significant global impact on climate and the biosphere. In this study, we revise data on local seismicity in the Toba area recorded by a temporary PASSCAL network in 1995. We applied the newest version of the LOTOS-07 algorithm, which includes absolute source location, optimization of the starting 1-D velocity model, and iterative tomographic inversion for 3-D seismic P, S (or the VP/VS ratio) and source parameters. Special attention is paid to verification of the obtained results. Beneath the Toba caldera and other volcanoes of the arc, we observe relatively moderate (for volcanic areas) negative P- and S-velocity anomalies that reach 18 per cent in the uppermost layer, 10-12 per cent in the lower crust and about 7 per cent in the uppermost mantle. Much stronger contrasts are observed for the VP/VS ratio that is a possible indicator of dominant effect of melting in origin of seismic anomalies. At a depth of 5 km beneath active volcanoes, we observe small patterns (7-15 km size) with a high VP/VS ratio that might be an image of actual magmatic chambers filled with partially molten material feeding the volcanoes. In the mantle wedge, we observe a vertical anomaly with low P and S velocities and a high VP/VS ratio that link the cluster of events at 120-140 km depth with Toba caldera. This may be an image of ascending fluids and melts released from the subducted slab due to phase transitions. However, taking into account poor vertical resolution, these results should be interpreted with prudence. Although the results show clear signatures that are quite typical for volcanic areas (low velocity and high VP/VS ratio beneath volcanoes), we do not observe any specific features in seismic structure that could characterize Toba as a super volcano.

  15. Exportaciones, términos de intercambio y crecimiento económico de Brasil y México, de 1960 a 2002: un análisis comparativo

    Directory of Open Access Journals (Sweden)

    Carlos Alberto Fraga Castillo

    2006-01-01

    Full Text Available México y Brasil son las economías más grandes de la región, caracterizadas por una fuerte presencia de la industria. Ambas han tenido, en diferente grado, un cambio importante en su estrategia de desarrollo, pasando de un modelo centrado en la sustitución de importaciones y la intervención del Estado en la economía a otro modelo abierto a la competencia externa y concentrado en las exportaciones como motor de impulso. El propósito de este trabajo es precisamente comparar en qué medida dicha reorientación "hacia el sector externo"se revela en la capacidad de arrastre del sector exportador al resto de la economía. Para ello se evalúan las elasticidades de comercio y -con base en el modelo desarrollado por A.P. Thirlwall- se estima su impacto en la tasa de crecimiento económico de largo plazo. crecimiento, restricción, intercambio, exportaciones, balanza.

  16. Mecanismos de intercambio en períodos de transición: el caso de los arrendamientos de dos estancias de la Puna jujeña (1813-1819

    Directory of Open Access Journals (Sweden)

    Conti, Viviana E.

    1994-06-01

    Full Text Available Not available.

    Las condiciones de desarrollo y consolidación del sistema colonial mercantilista en los Andes Meridionales se modifican rápidamente en la segunda mitad del XVIII. Pero se trata de una modificación ambigua: renacer de la minería potosina y reverdecer del comercio por un lado, pero reiteradas crisis estructurales -guerras y sequias-« por el otro. En la primera década del XIX es evidente el deterioro de todo el sistema pero también las estrategias asumidas para detenerlo. En este artículo se examinan los arrendamientos de tierras en plena Guerra de Independencia como fuente rentística colonial, acceso alternativo a bienes y moneda y conjunto de estrategias comerciales del campesinado de la Puna jujeña. Se concluye que estos campesinos mantuvieron su producción e intercambios captando moneda en el circuito mercantil. Los arrendamientos, como antes el tributo, marcan el éxito de las estrategias indígenas en el manejo de plata y bienes frente al mercado y al pago mismo de sus obligaciones.

  17. CityGML como modelo de datos para la representación, intercambio y visualización de información sobre el patrimonio arquitectónico

    Directory of Open Access Journals (Sweden)

    Iñaki Prieto

    2012-05-01

    Full Text Available La documentación del patrimonio arquitectónico se ha convertido, en los últimos años, en una prioridad para las instituciones encargadas de la gestión y conservación del patrimonio. Una de las posibles soluciones consiste en utilizar estándares como CityGML para almacenar información 3D e información semántica relacionada con el patrimonio arquitectónico. Este artículo presenta la metodología de trabajo que estamos siguiendo en el proyecto ADISPA que consiste en: generar y almacenar la información a documentar en CityGML; y analizar las herramientas y estándares para interoperabilidad, compatibilidad e intercambio con el fin de explotar la información del modelo de datos en aplicaciones de modelado, anotación y visualización 3D.

  18. Acuerdos binacionales de mercados y la economía subterránea dominico-haitiana. (Reflejos de un intercambio desigual; discriminación y pobreza en el Batey Dominicano

    Directory of Open Access Journals (Sweden)

    Juan Toribio

    2012-01-01

    Full Text Available El artículo propone un recorrido histórico, analítico y crítico de las incidencias que han acompañado las relaciones económicas, comerciales y políticas dominico- haitianas y la conformación de un mercado subterráneo alimentado por la existencia de una significativa población de origen haitiano y dominicohaitiano residente en su mayoría en los bateyes de la República. Se realiza un breve recorrido por la senda histórica escaneando los principales acuerdos de mercados y la economía de ambos países en dirección a identificar el perfil y las características que contienen los últimos pactos binacionales de mercado y la permanencia de una economía subterránea, no formal, que drena importantes flujos de recursos humanos, técnicos, físicos y financieros entre ambas naciones. En el artículo se convoca una discusión académica, pero también política de las perspectivas que muestran hoy las relaciones Dominico-Haitianas, para ambos casos se tendría que admitir la presencia de un oscuro y complejo escenario cuyos pilares se sustentan en una economía de intercambio desigual sin modificaciones importantes en el corto y mediano plazos.

  19. Modelos de elección discreta aplicados a la estimación de la distribución geográfica de los intercambios comerciales en Andalucia

    Directory of Open Access Journals (Sweden)

    José Manuel Rueda Cantuche

    2002-01-01

    Full Text Available El trabajo que se realiza quinquenalmente para la elaboración del Marco Input-Output requiere una cantidad de recursos que difícilmente pueden ser asignados anualmente a este cometido. Por ello, pueden resultar de enorme utilidad todos aquellos trabajos de investigación sobre la aplicación de nuevos instrumentos de carácter cuantitativo y estocástico que permitan establecer estimaciones sobre determinadas variables económicas necesarias para la construcción de dicho Marco pero con carácter anual. En esta comunicación se presentan los primeros avances de un proyecto de investigación que aplica modelos de elección discreta con datos ordenados para la elaboración de una metodología que permita conocer los intercambios comerciales de productos entre Andalucía y el resto de España, a través de comerciantes mayoristas e intermediarios de comercio.

  20. Implementación de un nuevo sistema de tratamiento de agua con ceniza proveniente de los lavadores de gases de combustión de las calderas del ingenio San Carlos

    OpenAIRE

    Vizueta Méndez, Julio Alexander; Martínez Lozano, Ernesto

    2013-01-01

    Para la producción de azúcar y energía eléctrica el Ingenio San Carlos quema bagazo de caña en sus calderas generándose cantidades considerables de cenizas con los gases de combustión. El Ministerio del Ambiente regula la cantidad de particulado de cenizas que este tipo de caldera emite hacia la atmosfera y la empresa esta obligada a cumplir con los parámetros establecidos para las emisiones. Para el control de particulado de ceniza, las calderas cuentan con sistemas es de una importancia el ...

  1. Nuevas evidencias geofísicas de la existencia de una caldera cubierta en laguna Pozuelos: Puna norte New geophysical evidences of the presence of a buried caldera in Laguna Pozuelos: Northern Puna

    Directory of Open Access Journals (Sweden)

    Claudia B Prezzi

    2010-03-01

    Full Text Available En el extremo sur de la cuenca de laguna de Pozuelos aflora el complejo volcánico Pan de Azúcar. El mismo está integrado por varios centros eruptivos de composición dacítica y morfología dómica que poseen una edad de ~12 Ma. Interpretaciones previas de líneas sísmicas y un relevamiento magnetométrico detallado indicaron la presencia de cuerpos intrusivos no aflorantes. La determinación de la existencia de nuevos cuerpos intrusivos no aflorantes en la zona resulta de interés debido a que: 1 estos complejos volcánicos dacíticos están estrechamente asociados con mineralización de interés económico (forman parte del cinturón estañífero boliviano; y 2 la existencia de una caldera antigua (~ 12 Ma de grandes dimensiones, ahogada bajo la cubierta sedimentaria que rellena la depresión de Pozuelos, ha sido propuesta por distintos autores. Los complejos dómicos representarían las fases magmáticas finales de dicho sistema magmático caldérico. Con la finalidad de determinar la existencia de dicho sistema caldérico y/o de otros cuerpos intrusivos no aflorantes se llevaron a cabo nuevos relevamientos magnetométricos y gravimétricos terrestres detallados. El mapa magnetométrico obtenido presenta conspicuas anomalías positivas y negativas que dominan el sector sur de la cuenca, probablemente asociadas con la presencia de los domos dacíticos aflorantes. La anomalía residual de Bouguer presenta un patrón semicircular, mostrando sólo valores positivos. La curvatura de las señales magnetométricas y gravimétricas fue analizada y se utilizó la deconvolución de Euler para estimar las profundidades a las fuentes causantes de las anomalías detectadas. Los resultados obtenidos hasta el momento apoyan la hipótesis de la existencia de una gran caldera soterrada en la cuenca de Laguna Pozuelos. La identificación de un gran sistema caldérico mioceno medio contribuirá a una mejor comprensión de la evolución magmática de la Puna

  2. Advisory expert system for energy analysis in industrial boilers; Sistema experto asesor en el analisis energetico de calderas industriales

    Energy Technology Data Exchange (ETDEWEB)

    Kemper Valverde, Nicolas; Lara Rosano, Felipe; Vazquez Nava, Rodolfo [Laboratorio de Inteligencia Artificial, Instituto de Ingenieria UNAM, Mexico, D. F. (Mexico)

    1994-12-31

    This paper presents an expert system for the operational analysis of industrial boilers, estimating the potential of heat recovery, in the small and medium size industry. The package is friendly, practical, flexible easy to maintain and expandable to take into consideration the user`s specific requirements and allows the analysis of the energy losses in the combustion, feed water, drains, and insulation, identifying the enhancements and estimating the saving potential, in energy as well as economical. [Espanol] En este trabajo se presenta un sistema experto para analizar la operacion de calderas industriales estimando el potencial de recuperacion de calor, en la pequena y mediana industria. El paquete es amigable, practico, flexible, facil en su mantenimiento y expandible para tomar en consideracion los requerimientos especificos de los usuarios y permite el analisis de las perdidas de energia en la combustion, agua de alimentacion, purgas y aislamientos, identificando las mejoras y estimando ahorros potenciales, tanto energeticos como economicos.

  3. Evaluation of mineral resource potential, caldera geology, and volcano-tectonic framework at and near Yucca Mountain

    Energy Technology Data Exchange (ETDEWEB)

    Weiss, S.I.; Noble, D.C.; Larson, L.T. [Univ. of Nevada, Reno, NV (United States)

    1992-09-30

    This report summarizes the result of Task 3 work initially discussed in our monthly reports for the period October 1, 1991 through September 30, 1992, and contained in our various papers and abstracts, both published and currently in press or review. Our work during this period has involved (a) the continuation of studies begun prior to October, 1991, focussed mainly on aspects of the caldera geology, volcanic stratigraphy, magmatic activity, hydrothermal mineralization and extensional tectonics of the western and northwestern parts of the southwestern Nevada volcanic field (SWNVF), and (b) new studies of the alteration and trace-metal geochemistry of subsurface rocks at Yucca Mountain utilizing drill hole samples obtained in late 1991 and early 1992.

  4. Three-dimensional electrical resistivity model of the hydrothermal system in Long Valley Caldera, California, from magnetotellurics

    Science.gov (United States)

    Peacock, J. R.; Mangan, M. T.; McPhee, D.; Wannamaker, P. E.

    2016-08-01

    Though shallow flow of hydrothermal fluids in Long Valley Caldera, California, has been well studied, neither the hydrothermal source reservoir nor heat source has been well characterized. Here a grid of magnetotelluric data were collected around the Long Valley volcanic system and modeled in 3-D. The preferred electrical resistivity model suggests that the source reservoir is a narrow east-west elongated body 4 km below the west moat. The heat source could be a zone of 2-5% partial melt 8 km below Deer Mountain. Additionally, a collection of hypersaline fluids, not connected to the shallow hydrothermal system, is found 3 km below the medial graben, which could originate from a zone of 5-10% partial melt 8 km below the south moat. Below Mammoth Mountain is a 3 km thick isolated body containing fluids and gases originating from an 8 km deep zone of 5-10% basaltic partial melt.

  5. ROCK PHYSICS. Rock physics of fibrous rocks akin to Roman concrete explains uplifts at Campi Flegrei Caldera.

    Science.gov (United States)

    Vanorio, Tiziana; Kanitpanyacharoen, Waruntorn

    2015-08-07

    Uplifts in the Campi Flegrei caldera reach values unsurpassed anywhere in the world (~2 meters). Despite the marked deformation, the release of strain appears delayed. The rock physics analysis of well cores highlights the presence of two horizons, above and below the seismogenic area, underlying a coupled process. The basement is a calc-silicate rock housing hydrothermal decarbonation reactions, which provide lime-rich fluids. The caprock above the seismogenic area has a pozzolanic composition and a fibril-rich matrix that results from lime-pozzolanic reactions. These findings provide evidence for a natural process reflecting that characterizing the cementitious pastes in modern and Roman concrete. The formation of fibrous minerals by intertwining filaments confers shear and tensile strength to the caprock, contributing to its ductility and increased resistance to fracture.

  6. Evaluation of minderal resource potential, Caldera geology, and volcano-tectonic framework at and near Yucca Mountain, Task 3

    Energy Technology Data Exchange (ETDEWEB)

    Weiss, S.I.; Noble, D.C.; Larson, L.T. [Univ. of Nevada, Reno, NV (United States)

    1993-09-30

    This report summarizes the results of Task 3 work that was initially discussed in our monthly reports for the period October 1, 1992 through September 30, 1993, and contained in our various papers and abstracts, both published and currently in press or in review. Our work during this period was involved (a) the continuation of studies begun prior to October, 1992, focussed mainly on aspects of the caldera geology, volcanic stratigraphy, magmatic activity, hydrothermal mineralization and extensional tectonics of the western and northwestern parts of the southwestern and Nevada volcanic field (SWNVF), studies of the subsurface rocks of Yucca Mountain utilizing drill hole samples obtained in 1991 and 1992, and (b) new studies of veins and siliceous rocks cropping out in northwestern Yucca Mountain that provide evidence for previously unrecognized hydrothermal activity during the Crater Flat Tuff period of volcanism.

  7. MODELO CONCEPTUAL DE UN PROYECTO DE SOFTWARE UTILIZANDO EL RAZONAMIENTO BASADO EN CASOS

    Directory of Open Access Journals (Sweden)

    Martha Delgado Dapena

    2002-10-01

    Full Text Available

    Este trabajo tiene por objetivo aprovechar el conocimiento acumulado por los diseñadores (proyectistas de software en nuevos proyectos, utilizando el razonamiento basado en casos (RBC, para obtener un modelo conceptual de UML (lenguaje de modelación unificado partiendo de una lista de requerimientos candidatos definidos por los analistas. Con esta información, de carácter preliminar, los grupos de desarrollo pueden simplificar de manera notable algunos aspectos de las fases de modelación iniciales que permitan aprovechar el trabajo y las experiencias previas y aceleren por vías probadas el proceso total de elaboración de software. En este trabajo se describen las características generales del funcionamiento de un sistema que se desarrolla en el Centro de Estudios de Ingeniería de Sistemas (CEIS, que aborda estos temas de la ingeniería de software, utilizando la técnica de inteligencia artificial de razonamiento basado en casos.

  8. DYNAMIC MIXING MODEL OF THE CHIGNAHUAPAN THERMAL SPRING IN THE GEOTHERMAL ZONE OF THE ACOCULCO CALDERA, PUEBLA, MEXICO

    Science.gov (United States)

    Gutierrez-Cirlos, A.; Torres-Rodriguez, V.

    2009-12-01

    The Acoculco Caldera, of Pliocenic age, is located within the limits of the Transmexican Volcanic Belt (CVT) and the Sierra Madre Oriental (SMOr). The Acoculco geothermal zone consists of a 790m thick igneous sequence, related to a volcanic complex formed by andesites and rhyolitic domes emplaced in an 18 Km diameter annular fracture. It unconformably overlies a 5000 m thick section of folded and faulted Jurassic-Cretaceous carbonate rocks. The Chignahuapan Spring, located in the extreme eastern part of the Geothermal Zone of the Acoculco Caldera, yields temperatures of 49°C and discharges an estimated of 98 lps from the karstified Lower Cretaceous limestone. Both major and trace element geochemical analysis were carried out, and results were interpreted using Piper and Stiff diagrams, as well as geothermometry. The results indicate that water belongs to the calcium-bicarbonate type and yield temperatures in a range of 70-80°C at depth, which suggest an extensive lateral flow from the main reservoir and mixing with shallow groundwaters. The spring suffers significant variations in its temperature throughout the year, especially during the rainy season, when water temperature decreases up to 10°C. Analyzing the hot spring water temperature data from of the last 10 years and comparing it with the precipitation and air temperature curves of the region, we expect to develop a dynamic mixing model which depicts the relation between these factors and the importance of each one in the water temperature variation. We also look forward to be able to forecast water temperature trends for the next several years and correlate it with climate change in the area.

  9. 238U-230Th dating of chevkinite in high-silica rhyolites from La Primavera and Yellowstone calderas

    Science.gov (United States)

    Vazquez, Jorge A.; Velasco, Noel O.; Schmitt, Axel K.; Bleick, Heather A.; Stelten, Mark E.

    2014-01-01

    Application of 238U-230Th disequilibrium dating of accessory minerals with contrasting stabilities and compositions can provide a unique perspective on magmatic evolution by placing the thermochemical evolution of magma within the framework of absolute time. Chevkinite, a Th-rich accessory mineral that occurs in peralkaline and metaluminous rhyolites, may be particularly useful as a chronometer of crystallization and differentiation because its composition may reflect the chemical changes of its host melt. Ion microprobe 128U-230Th dating of single chevkinite microphenocrysts from pre- and post-caldera La Primavera, Mexico, rhyolites yields model crystallization ages that are within 10's of k.y. of their corresponding K-Ar ages of ca. 125 ka to 85 ka, while chevkinite microphenocrysts from a post-caldera Yellowstone, USA, rhyolite yield a range of ages from ca. 110 ka to 250 ka, which is indistinguishable from the age distribution of coexisting zircon. Internal chevkinite-zircon isochrons from La Primavera yield Pleistocene ages with ~5% precision due to the nearly two order difference in Th/U between both minerals. Coupling chevkinite 238U-230Th ages and compositional analyses reveals a secular trend of Th/U and rare earth elements recorded in Yellowstone rhyolite, likely reflecting progressive compositional evolution of host magma. The relatively short timescale between chevkinite-zircon crystallization and eruption suggests that crystal-poor rhyolites at La Primavera were erupted shortly after differentiation and/or reheating. These results indicate that 238U-230Th dating of chevkinite via ion microprobe analysis may be used to date crystallization and chemical evolution of silicic magmas.

  10. Regulatory, Land Ownership, and Water Availability Factors for a Magma Well: Long Valley Caldera and Coso Hot Springs, California

    Energy Technology Data Exchange (ETDEWEB)

    Blackett, Robert

    1985-09-01

    The U.S. Department of Energy is currently engaged in a program to demonstrate the engineering feasibility of extracting thermal energy from high-level molten magma bodies. The program is being carried out under the direction of Sandia National Laboratories where a number of individual projects support the overall program. The existing program elements include (1) high-temperature materials compatibility testing; (2) studies of properties of melts of various compositions; and (3) the investigation of the economics of a magma energy extraction system. Another element of the program is being conducted with the cooperation of the U.S. Geological Survey, and involves locating and outlining magma bodies at selected sites using various geophysical techniques. The ultimate goal here will be to define the limits of a magma body as a drilling target. During an earlier phase of the program, more than twenty candidate study sites considered were evaluated based upon: (1) the likelihood of the presence of a shallow magma chamber, (2) the accessibility of the site, and (3) physical and institutional constraints associated with each site with respect to performing long-term experiments. From these early phase activities, the number of candidate sites were eventually narrowed to just 2. The sites currently under consideration are Coso Hot Springs and the Long Valley caldera (Figure 1). This report describes certain attributes of these sites in order to help identify potential problems related to: (1) state and federal regulations pertaining to geothermal development; (2) land ownership; and (3) water resource availability. The information sources used in this study were mainly maps, publications, and informative documents gathered from the California Division of Oil and Gas and the U.S. Department of the Interior. Environmental studies completed for the entire Long Valley caldera study area, and for portions of the Coso Hot Springs study area were also used for reference.

  11. Was Miyakejima undergoing subsidence before the 2000 caldera collapse? JERS1 InSAR results: 1992-1998

    Science.gov (United States)

    Furuya, M.

    2003-12-01

    Miyakejima volcano is a basaltic strato volcano island on the eastern edge of the Philippine Sea Plate, and was undergoing a number of eruption activities over the past centuries. In July-August 2000, the Miyakejima volcano underwent a caldera collapse, prompting many modern geodetic and geophysical measurements (e.g., Geshi et al. 2002; Furuya et al. 2003). The observation results on the pre-caldera-collapse stages are, however, limitted. Were there any precursory secular subsidence before the collapse? Though Miyazaki (1990) reported a secular subsidence at the Miyakejima, using leveling technique, there are no documented reports, to my knowledge, which employed radar interferometry to examine the ground displacements at Miyakejima. Here I will report on the results derived from the radar interferometry at Miyakejima volcano. I chose JERS-1 data (L-band HH) for the analysis, so that I could get rid of the loss of coherence; most of the Miyakejima is covered with vegetation. To remove the topographic fringes as well as to re-estimate the spatial baseline data (Rosen et al. 1996), I employed 10-meter resolution digital elevation map derived by Geographical Survey Institute, Japan. I could generate 24 differential interferograms at the time of writing this text. However, I do not yet recognize any significant "signals" that can be discriminated with the atmospheric "noise". There appears to be no specific subsidence pattern, which are detected in a number of other volcanos in the world (e.g., Lu et al. 2002; Yarai et al. 2002; Okuyama et al. 2002). I am going to show a stacked interferogram like that in Fujiwara et al. (1998) and to examine the existence of volcanic signals.

  12. Steam flow generation in semi-arid, forested and seasonally snow-covered catchments, Valles Caldera, New Mexico

    Science.gov (United States)

    Liu, F.; Bales, R. C.; Conklin, M. H.; Kostrzewski, J. M.

    2005-12-01

    Stream flow generation is poorly understood for semi-arid, forested and seasonally snow-covered catchments in southwest US. Here we report on initial results of a pioneer study on source waters and flowpaths using isotopic and geochemical tracers in two streams originated from Redondo Peak in Valles Caldera, New Mexico. The Valles Caldera is the latest collapse feature in the volcanic field and hosts high-temperature hydrothermal systems with several geothermal springs. It is currently covered by ponderosa pine in lower elevations and mixed conifer in higher elevations. Samples were collected from snow, hillslope groundwater, and stream water at Redondo Creek and La Jara Creek from December 2004 to July 2005. Using diagnostic tools of mixing models and end-member mixing analysis, it is suggested that stream water quantity and quality at Redondo Creek were primarily controlled by mixing of two end-members: hillslope subsurface water and geothermal springs. Hillslope subsurface water was sourced from snowmelt and then gradually released to stream flow through spring and summer. Infiltration-excess overland flow of snowmelt did not appear to occur. Contribution of hillslope subsurface water to stream flow was 90% on average from December 2004 to July 2005 and its percentage gradually increased from spring to summer with increase in discharge. Contribution of geothermal springs decreased on percentage over season with a peak (20%) in late march and lowest but relatively constant value (5%) through June and July. Stream flow generation at La Jara Creek was relatively simple, all from hillslope subsurface water. This information may improve our understanding of changes of hydrological and biogeochemical cycles in response to climate warming in these and similar catchments in southwest US.

  13. Geomorfología de la región de los lagos Moquehue y Aluminé: consideraciones acerca de las propuestas Calderas Meseta del Arco y Nacimientos del Aluminé (Neuquén Geomorphology of the Moquehue and Aluminé Lakes: Considerations about the Meseta del Arco and Nacimientos del Aluminé calderas

    Directory of Open Access Journals (Sweden)

    Emilio F. González Díaz

    2010-05-01

    Full Text Available Se exponen elementos de juicio geomórficos y estructurales, que avalan la morfogénesis glaciaria de la depresión en artesa que aloja la cuenca lacustre Moquehue-Aluminé, ubicada en la cordillera neuquina (38°30´S, adyacente al límite internacional. Trabajos anteriores distinguen en la región dos calderas de un gran complejo volcánico plio-cuaternario, situado al este del frente volcánico actual e integrado por nueve depresiones caldéricas y cuerpos dómicos asociados. En el área de estudio sólo la caldera de Pino Hachado tiene la validez necesaria, cuestionándose el reconocimiento de las calderas denominadas Nacimientos del Aluminé y Meseta del Arco, al tiempo que se avala el origen erosivo de las abruptas escarpas orientales que marginan el plateau de Lonco Luan-Meseta del Arco, las que fueran interpretadas como márgenes de las sugeridas calderas. Se analizan las fases o tipología del englazamiento pleistoceno local, su extensión, las direcciones de los principales movimientos de su flujo y su más que probable aporte de hielo por difluencia, a un contemporáneo englazamiento en Chile (laguna Icalma. Se describen aspectos de la morfogenia volcánica cenozoica y otros más locales de la remoción en masa y el proceso eólico. Se incorporan breves comentarios acerca de un propuesto drenaje atlántico de un río Bío Bío preglaciario y se cuestiona aquellos antecedentes que avalan la extensión en la región de la fosa Bío Bío-Aluminé y la presencia de las citadas calderas. Una serie de perfiles esquemáticos topográfico-geológicos contribuyen a dicho cuestionamiento.The region is situated in the Neuquén Cordillera at 38° 30´S latitud close to the international border. Geomorphic and structural features are presented which indicated a glacial morphogenesis for the depression that contains the Moquehue- Aluminé lakes. Previous works have identified a large volcanic complex related to Plio-Quaternary volcanic activity

  14. Fault Networks in the Northwestern Albuquerque Basin and Their Potential Role in Controlling Mantle CO2 Degassing and Fluid Migration from the Valles Caldera

    Science.gov (United States)

    Smith, J. R.; Crossey, L. J.; Karlstrom, K. E.; Fischer, T. P.; Lee, H.; McGibbon, C. J.

    2015-12-01

    The Rio Grande rift (RGR) has Quaternary and active volcanism and faulting that provide a field laboratory for examining links between mantle degassing and faults as fluid conduits. Diffuse and spring CO2 flux measurements were taken at 6 sites in the northwestern Albuquerque Basin (NWAB) and Valles caldera geothermal system. All sites progress to the southwest from the 1.25 Ma Valles caldera, down the rift-related Jemez fault network, to intersect with the Nacimiento fault system. Mantle CO2 and He degassing are well documented at 5 of 6 sites, with decreasing 3He/4He ratios away from the caldera. The instrument used to measure CO2 flux was an EGM-4 CO2 gas analyzer (PP systems) with an accumulation chamber. Carbonic springs at Penasco Springs (PS) and San Ysidro (SY), and the carbonate-cemented Sand Hill Fault (SHF) were targeted, all near the western border of the RGR. The SHF has no spring activity, had the smallest maximum flux of all the sites (8 g/m2d), but carbonate along the fault zone (<2 m wide) attest to past CO2 flux. The other two sites are equal distance (30-40 km) between the SHF site and Valles caldera sites. These sites have active carbonic springs that precipitate travertine mounds. Our work suggests these sites reflect intersections of the Nacimiento fault with NE trending faults that connect to the Jemez fault network. The maximum diffuse flux recorded at SY (297 g/m2d) and PS (25 g/m2d) are high, especially along the fault and near springs. At SY and PS the instruments capacity was exceeded (2,400 g/m2d) at 6 of 9 springs. Interpretations indicate a direct CO2 flux through a fault-related artesian aquifer system that is connected to magmatic gases from the caldera. Maximum diffuse flux measurements of Alamo Canyon (20,906 g/m2d), Sulphur Springs (2,400 g/m2d) and Soda Dam (1,882 g/m2d) at Valles caldera geothermal sites are comparable to Yellowstone geothermal systems. We use geospatial analysis and local geologic mapping to examine

  15. The link between volcanism and plutonism in epizonal magma systems; high-precision U-Pb zircon geochronology from the Organ Mountains caldera and batholith, New Mexico

    Science.gov (United States)

    Rioux, Matthew; Farmer, G. Lang; Bowring, Samuel A.; Wooton, Kathleen M.; Amato, Jeffrey M.; Coleman, Drew S.; Verplanck, Philip L.

    2016-02-01

    The Organ Mountains caldera and batholith expose the volcanic and epizonal plutonic record of an Eocene caldera complex. The caldera and batholith are well exposed, and extensive previous mapping and geochemical analyses have suggested a clear link between the volcanic and plutonic sections, making this an ideal location to study magmatic processes associated with caldera volcanism. Here we present high-precision thermal ionization mass spectrometry U-Pb zircon dates from throughout the caldera and batholith, and use these dates to test and improve existing petrogenetic models. The new dates indicate that Eocene volcanic and plutonic rocks in the Organ Mountains formed from ~44 to 34 Ma. The three largest caldera-related tuff units yielded weighted mean 206Pb/238U dates of 36.441 ± 0.020 Ma (Cueva Tuff), 36.259 ± 0.016 Ma (Achenback Park tuff), and 36.215 ± 0.016 Ma (Squaw Mountain tuff). An alkali feldspar granite, which is chemically similar to the erupted tuffs, yielded a synchronous weighted mean 206Pb/238U date of 36.259 ± 0.021 Ma. Weighted mean 206Pb/238U dates from the larger volume syenitic phase of the underlying Organ Needle pluton range from 36.130 ± 0.031 to 36.071 ± 0.012 Ma, and the youngest sample is 144 ± 20 to 188 ± 20 ka younger than the Squaw Mountain and Achenback Park tuffs, respectively. Younger plutonism in the batholith continued through at least 34.051 ± 0.029 Ma. We propose that the Achenback Park tuff, Squaw Mountain tuff, alkali feldspar granite and Organ Needle pluton formed from a single, long-lived magma chamber/mush zone. Early silicic magmas generated by partial melting of the lower crust rose to form an epizonal magma chamber. Underplating of the resulting mush zone led to partial melting and generation of a high-silica alkali feldspar granite cap, which erupted to form the tuffs. The deeper parts of the chamber underwent continued recharge and crystallization for 144 ± 20 ka after the final eruption. Calculated magmatic

  16. Troca de gases prejudicada em pacientes com angina instável Deterioro del intercambio gaseoso en pacientes con angina inestable Impaired gas exchange in patients with unstable angina

    Directory of Open Access Journals (Sweden)

    Dayane Horta Rocha

    2009-09-01

    Full Text Available A identificação do diagnóstico de enfermagem "troca de gases prejudicada na assistência aos pacientes com angina" é visualizada rotineiramente, porém faz-se necessário um aprofundamento desta temática. Com o objetivo de analisar a ocorrência deste diagnóstico, realizamos um estudo transversal, de caráter descritivo-exploratório, com pacientes internados em um hospital especializado. Os dados foram obtidos por meio de entrevista, exame físico e consulta ao prontuário. O diagnóstico "troca de gases prejudicada" foi ausente em nossa amostra; entretanto, as variáveis profundidade da respiração, pressão arterial sistólica, sonolência e sódio sérico estiveram comprometidas, o que indica risco de agravamento. Visualizamos alguma relação entre os resultados obtidos e características do estilo de vida dos pacientes avaliados, o que reforça a importância de medidas preventivas para a obtenção de um melhor prognóstico na assistência aos pacientes com angina.La identificación del diagnóstico realizado por parte de la enfermería del Deterioro del intercambio gaseoso en el cuidado de pacientes con angina es comúnmente percibida, sin embargo es necesario profundizar esta temática. Con el objetivo de analizar la ocurrencia del diagnóstico del Deterioro del intercambio gaseoso en portadores de Angina Inestable desarrollamos un estudio transversal, de carácter descriptivo-exploratorio, con pacientes ingresados en un hospital especializado. Los datos fueron recolectados por medio de entrevistas, examenes físicos y consultas a los registros médicos. Este diagnóstico no fue identificado en nuestra muestra, sin embargo, las variables profundidad de la respiración, presión arterial sistólica, somnolencia y sodio sérico presentaron alteraciones , lo que indica riesgo de agravación del cuadro clínico. Se identificó una relación entre los resultados obtenidos y las características del estilo de vida de los pacientes

  17. “El poder de recibir al menos lo que doy”: El intercambio de recursos y la jerarquía, en el mundo académico de la nanotecnología

    Directory of Open Access Journals (Sweden)

    Villanueva-Felez, Africa

    2014-12-01

    Full Text Available In this study we investigate the academic field of nanotechnology for analyzing the relation between hierarchical positions occupied by researchers and the type of social ties and resource exchanges that they have with external partners. To do this, we use a theoretical multidisciplinary perspective of scientific collaborations, which combines the approach of networking and resource sharing (Granovetter, 1973, Lin, 2001 with a sociological approach to power relations (Bourdieu, 1997. Following the intuition of Nan Lin (2001, we conclude that the positions of researchers in institutional hierarchies are crucial to the way they access resources. Occupying an elevated position represents a sure and steady exchange of resources. This means always being able to receive at least the equivalent of what you give, in a playing field of academic power relations that is perpetuated over time.En el presente estudio nos aproximamos al ámbito académico de la nanotecnología, donde analizamos la relación que existe entre las posiciones jerárquicas que ocupan los investigadores y el tipo de vínculos sociales y de recursos que intercambian con colaboradores externos. Para ello recurrimos a una perspectiva teórica multidisciplinar de las colaboraciones científicas. Por un lado, al enfoque de las redes y el intercambio de recursos y por el otro, al enfoque sociológico de las relaciones de poder. Como comprobaremos durante nuestro desarrollo, las posiciones jerárquicas de los investigadores son determinantes en la forma que tienen de acceder a los recursos. Ocupar una posición elevada equivale a intercambiar recursos de forma segura y constante. Significa poder recibir siempre al menos los que das, dentro de un campo académico de relaciones de poder, que se reproduce en el tiempo.

  18. Presiones Antropogénicas Relacionadas con el Comportamiento, Hidrodinámica, Flujos e Intercambios de Compuestos Biógeno en el Estuario del Río las Casas. Isla de la Juventud, Cuba.

    Directory of Open Access Journals (Sweden)

    Eusebio Perigó Arnaud

    2005-01-01

    Full Text Available Se presentan los resultados de estudios realizados en el estuario del río Las Casas con el objetivo de evaluar el estado de la calidad del ecosistema, sometido a las presiones antropogénicas originadas por las descargas contaminantes en sus últimos 5 Km. de su desembocadura de residuales crudos industriales, agropecuarios y domésticos cuyos impactos se reflejan en una notable alteración del balance del oxígeno disuelto y altas concentraciones de materia orgánica y nutrientes en agua y sedimentos, lo cual afecta la estructura y el funcionamiento del estuario y es exportador de compuestos de C, N y P al Golfo de Batabanó de acuerdo a resultados obtenidos a partir de muestreos diurnos en la frontera estuario - golfo. Se aplicó un modelo hidronumérico de simulación acoplado de OD-DBO para conocer los porcentajes de tratamiento a que deben ser sometidos los residuales para que el cuerpo de agua alcance los valores de las normas de calidad para uso pesquero y así garantizar un manejo y uso sustentable de los recursos pesqueros, actividades portuarias y otras actividades como las recreativas y la acuicultura. La construcción de una planta comunitaria con tratamiento biológico y el uso de las aguas tratadas como fertirriegos serían las mejores alternativas para mitigar el impacto ambiental dado la cercanía de los focos y la naturaleza común de los residuos. Para la estimación de los intercambios de compuestos biógenos y el metabolismo del ecosistema estuarino se aplicó un modelo trófico de caja donde reportó que el estuario es un sumidero de estos compuestos

  19. PRODUCCION DE HIDROGENO POR FOTOELECTROLISIS DEL AGUA UTILIZANDO UN FOTOCATALIZADOR BASADO EN MEMBRANAS DE ALUMINA POROSA

    OpenAIRE

    HOMM JARA, PIA

    2013-01-01

    La producción de hidrógeno a partir del proceso de fotoelectrólisis del agua utilizando luz solar, es uno de los desafíos más importantes para los investigadores en el área de producción de energía en estos días. La obtención de hidrógeno por medio de una celda fotoelectroquímica (PEC) requiere de fotocatalizadores que satisfagan, simultáneamente, requerimientos como la absorción eficiente de luz solar, promover un rápido transporte de las cargas foto -generadas y además, poder llevar a...

  20. Tratamento de efluente tÃxtil utilizando o processo foto-fenton

    OpenAIRE

    Diego Ricieri Manenti

    2011-01-01

    O objetivo deste trabalho à avaliar o desempenho do processo foto-Fenton, utilizando energia solar e artificial como fontes de irradiaÃÃo UV, no tratamento de efluentes tÃxteis. Foram realizados experimentos preliminares para avaliar a eficiÃncia do processo foto-Fenton na mineralizaÃÃo e degradaÃÃo dos poluentes orgÃnicos e inorgÃnicos, bem como dos corantes sintÃticos. Para tanto, foi preparado o efluente tÃxtil sintÃtico pela mistura de seis corantes: Laranja TGL (C25H33ClN6O6S2), Azul FGL...

  1. Una propuesta para mejorar la completitud de requisitos utilizando un enfoque lingüístico

    Directory of Open Access Journals (Sweden)

    Carlos M. Zapata J.

    2006-01-01

    Full Text Available La calidad de los productos de software está estrechamente relacionada con la calidad de los requisitos especificados desde las primeras etapas del proceso de desarrollo; las propuestas encaminadas a la especificación de requisitos realizan incipientes esfuerzos para lograr que los requisitos del software sean lo suficientemente completos como para lograr la traducción de las necesidades y expectativas de los usuarios al producto final. En este artículo se presenta una propuesta para mejorar la calidad, en cuanto a completitud, de especificaciones de requisitos escritas en un subconjunto del español denominado español restringido, utilizando para ello un enfoque lingüístico basado en la gramática de casos.

  2. Trazado de rutas migratorias utilizando alelos HLA clase II de indígenas Wayuu venezolanos

    Directory of Open Access Journals (Sweden)

    Miriam Echeverria

    2012-01-01

    Full Text Available Se realizó un estudio comparativo utilizando las frecuencias alélicas HLA-DRB1* de la poblaciónWayuú venezolana, con datos reportados de las poblaciones Caucásicas, Negroides Americanas y Amerindias siguientes: Barí, Warao y Yucpa (venezolanas, Wayúu colombiana, Australianos, Atahabaskans, Indios americanos, Seri, Maya, Taraumara, Kogi, Cayapa, indígenas brasileros, Mataco-Wichi, Toba Pilaga y Eastern Toba, con el fin de evaluar su posible contribución al origen de esta población indígena. Los alelos DRB1*03:01, 04:01, 04:03, 04:04, 04:07, 08:02, 13:01, 14:02 y 16:02 de los Wayuú venezolanos son los únicos comunes a todas las poblaciones amerindias desde Norte América hasta la Patagonia; igualmente analizamos otras contribuciones.

  3. Una experiencia en formación inicial del profesorado utilizando la red social ELGG

    Directory of Open Access Journals (Sweden)

    Francisco Javier Álvarez Lires

    2015-01-01

    Full Text Available Una experiencia de investigación-innovación educativa en forma- ción inicial del profesorado de Grados universitarios en Educación In- fantil, Primaria y Máster de Educación Secundaria y Formación Profe- sional, sobre las posibilidades que ofrece la red social de comunidad de aprendizaje ELGG, utilizando una metodología docente focalizada en el alumnado, hacia un aprendizaje colaborativo y cooperativo. Los resulta - dos muestran amplia participación, percepción de beneficios de aprendi - zaje, por parte del alumnado, coordinación entre docentes de áreas dife - rentes y cumplimiento de objetivos en cuanto a promoción de espacios y formas de aprendizaje que rompen con modelos tradicionales aprove - chando las posibilidades educativas de las TIC.

  4. Perspectivas de manejo de capororoca (Myrsine umbellata Mart. utilizando análise retrospectiva

    Directory of Open Access Journals (Sweden)

    Luciano Farinha Watzlawick

    2005-06-01

    Full Text Available A análise retrospectiva é um instrumento para avaliação rápida do potencial de crescimento utilizando-se a periodicidade do incremento em diâmetro, isto é, o crescimento dos anéis anuais. Utilizando-se esta técnica, foi avaliado o desenvolvimento e o crescimento da capororoca (Myrsine umbellata Mart., espécie nativa da Florestal Ombrofila Mista. O presente estudo foi realizado no Município de General Carneiro - PR, em área pertencente às Indústrias Pedro N. Pizzatto. Foi feita a análise de tronco e a medição dos anéis anuais em fatias retiradas nas alturas relativas a 10%, 50% e 75% da altura do ponto de inversão morfológico, bem como também na altura do DAP em quatro árvores, nas quais foram analisados o incremento em diâmetro e altura. Pelos resultados obtidos, pode-se considerar que as árvores analisadas mostraram um crescimento em diâmetro forte no estado inicial, mas seguindo uma tendência de crescimento lento e contínuo a médio prazo, até a idade de 5 anos. Com relação à altura comercial (ponto de inversão morfológico com 2 a 4 metros, nas árvores analisadas são alcançadas dentro dos primeiros dois anos de vida.

  5. Projeto e desenvolvimento de um carro robô controlado por smartphone, utilizando a plataforma Amarino

    Directory of Open Access Journals (Sweden)

    Otávio Souza Martins Gomes

    2015-01-01

    Full Text Available Este artigo mostra a construção de um carro robô controlado por dispositivos móveis utilizando o sistema operacional Android e uma placa de prototipagem open source (Arduino. Utilizou-se de motores para sua movimentação e sensores para interação com o ambiente. O envio de comandos foi realizado utilizando a tecnologia Bluetooth e é capaz de movimentar o carro robô em todas as direções de acordo com os comandos do usuário. Sensores instalados no carro coletam informações do ambiente que são enviadas ao dispositivo Android. A construção bem sucedida deste carro robô mostra que é possível implementar novas funcionalidades para esse produto, bem como apoiar outros projetos relacionados a esse tema.Palavras-chave: Arduino. Android. Bluetooth. Carro robô. Robótica. Project and development of a robot car controlled by smartphone, using the platform amarinoABSTRACTThis work shows the build of a robot car controlled by mobile devices employing Android operating system and an open source prototyping board (Arduino. Motors for its movements and sensors for its environment interaction were employed. The commands are transmitted using Bluetooth technology which can move the robot car in all directions according to the user commands. Sensors installed in the car collect the environment information which is sent to the Android device. The success build of this robot car shows that new features can be possible implemented as well as to support other projects related to this research area.Keywords: Arduino. Android. Bluetooth. Robot car. Robotic.

  6. Active tectonics on Deception Island (West-Antarctica): A new approach by using the fractal anisotropy of lineaments, fault slip measurements and the caldera collapse shape

    Science.gov (United States)

    Pérez-López, R.; Giner-Robles, J.L.; Martínez-Díaz, J.J.; Rodríguez-Pascua, M.A.; Bejar, M.; Paredes, C.; González-Casado, J.M.

    2007-01-01

    The tectonic field on Deception Island (South Shetlands, West Antarctica) is determined from structural and fractal analyses. Three different analyses are applied to the study of the strain and stress fields in the area: (1) field measurements of faults (strain analysis), (2) fractal geometry of the spatial distribution of lineaments and (3) the caldera shape (stress analyses). In this work, the identified strain field is extensional with the maximum horizontal shortening trending NE-SW and NW-SE. The fractal technique applied to the spatial distribution of lineaments indicates a stress field with SHMAX oriented NE-SW. The elliptical caldera of Deception Island, determined from field mapping, satellite imagery, vents and fissure eruptions, has an elongate shape and a stress field with SHMAX trending NE-SW.

  7. The 2007 eruptions and caldera collapse of the Piton de la Fournaise volcano (La Réunion Island) from tilt analysis at a single very broadband seismic station

    Science.gov (United States)

    Fontaine, Fabrice R.; Roult, Geneviève; Michon, Laurent; Barruol, Guilhem; Muro, Andrea Di

    2014-04-01

    Seismic records from La Réunion Island very broadband Geoscope station are investigated to constrain the link between the 2007 eruptive sequence and the related caldera collapse of the Piton de la Fournaise volcano. Tilt estimated from seismic records reveals that the three 2007 eruptions belong to a single inflation-deflation cycle. Tilt trend indicates that the small-volume summit eruption of 18 February occurred during a phase of continuous inflation that started in January 2007. Inflation decelerated 24 days before a second short-lived, small-volume eruption on 30 March, almost simultaneous with a sudden, large-scale deflation of the volcano. Deflation rate, which had stabilized at relatively low level, increased anew on 1 April while no magma was erupted, followed on 2 April by a major distal eruption and on 5 April by a summit caldera collapse. Long-term tilt variation suggests that the 2007 eruptive succession was triggered by a deep magma input.

  8. Unravelling the collapse mechanisms at a Jurassic caldera of the Chon Aike silicic LIP in Southern Patagonia (47° 15 'S, 71° 40'W), Argentina

    Science.gov (United States)

    Sruoga, P.; Japas, S.; Salani, F.; Kleiman, L.; Graffigna, M.

    2008-10-01

    La Peligrosa Caldera is located at Sierra Colorada (47° 15'S, 71° 40' W) in the Chon-Aike silicic LIP. It represents an unique window to understand the eruptive mechanisms that prevailed throughout the ignimbritic flare-up in Southern Patagonia during middle to late Jurassic times. Key pieces of lithologic and structural evidences are taken into account to reconstruct the volcanic structure.

  9. Effect of petrophysical properties and deformation on vertical zoning of metasomatic rocks in U-bearing volcanic structures: A case of the Strel'tsovka caldera, Transbaikal region

    Science.gov (United States)

    Petrov, V. A.; Andreeva, O. V.; Poluektov, V. V.

    2014-03-01

    The development of vertical zoning of wall-rock metasomatic alteration is considered with the Mesozoic Strel'tsovka caldera as an example. This caldera hosts Russia's largest uranium ore field. Metasomatic rocks with the participation of various phyllosilicates, carbonates, albite, and zeolites are widespread in the ore field. In the eastern block of the caldera, where the main uranium reserves are accommodated, hydromica metasomatic alteration gives way to beresitization with depth. Argillic alteration, which is typical of the western block, is replaced with hydromica and beresite alteration only at a significant depth. Postore argillic alteration is superposed on beresitized rocks in the lower part of the section. Two styles of vertical metasomatic zoning are caused by different modes of deformation in the western and eastern parts of the caldera. Variations of the most important petrophysical properties of host rocks—density, apparent porosity, velocities of P- and S-waves, dynamic Young's modulus, and Poisson coefficient—have been determined by sonic testing of samples taken from different depths. It is suggested that downward migration of the brittle-ductile transition zone could have been a factor controlling facies diversity of metasomatic rocks. Such a migration was caused by a new phase of tectonothermal impact accompanied by an increase in the strain rate or by emplacement of a new portion of heated fluid. Transient subsidence of the brittle-ductile boundary increases the depth of the hydrodynamically open zone related to the Earth's surface and accelerates percolation of cold meteoric water to a greater depth. As a result, the temperature of the hydrothermal solution falls down, increasing the vertical extent of argillic alteration. High-grade uranium mineralization is also localized more deeply than elsewhere.

  10. Gas geochemistry of the Valles caldera region, New Mexico and comparisons with gases at Yellowstone, Long Valley and other geothermal systems

    Science.gov (United States)

    Goff, F.; Janik, C.J.

    2002-01-01

    Noncondensible gases from hot springs, fumaroles, and deep wells within the Valles caldera geothermal system (210-300??C) consist of roughly 98.5 mo1% CO2, 0.5 mol% H2S, and 1 mol% other components. 3He/4He ratios indicate a deep magmatic source (R/Ra up to 6) whereas ??13C-CO2 values (-3 to -5???) do not discriminate between a mantle/magmatic source and a source from subjacent, hydrothermally altered Paleozoic carbonate rocks. Regional gases from sites within a 50-km radius beyond Valles caldera are relatively enriched in CO2 and He, but depleted in H2S compared to Valles gases. Regional gases have R/Ra values ???1.2 due to more interaction with the crust and/or less contribution from the mantle. Carbon sources for regional CO2 are varied. During 1982-1998, repeat analyses of gases from intracaldera sites at Sulphur Springs showed relatively constant CH4, H2, and H2S contents. The only exception was gas from Footbath Spring (1987-1993), which experienced increases in these three components during drilling and testing of scientific wells VC-2a and VC-2b. Present-day Valles gases contain substantially less N2 than fluid inclusion gases trapped in deep, early-stage, post-caldera vein minerals. This suggests that the long-lived Valles hydrothermal system (ca. 1 Myr) has depleted subsurface Paleozoic sedimentary rocks of nitrogen. When compared with gases from many other geothermal systems, Valles caldera gases are relatively enriched in He but depleted in CH4, N2 and Ar. In this respect, Valles gases resemble end-member hydrothermal and magmatic gases discharged at hot spots (Galapagos, Kilauea, and Yellowstone). Published by Elsevier Science B.V.

  11. Domes, Ash and Dust - Controls on soil genesis in a montane catchment of the Valles Caldera, New Mexico

    Science.gov (United States)

    Rasmussen, C.; Meding, S. M.; Vazquez, A.; Chorover, J.

    2012-12-01

    Soil genesis in volcanic terrain may be controlled by complex assemblages of parent materials and local topography. The objective of this work was to quantify topographic and parent material controls on soil and catchment evolution in a mixed conifer, montane catchment in the Valles Caldera, New Mexico, as part of the Jemez River Basin Critical Zone Observatory. The field site is a 16 ha catchment at an elevation of 3,000 m, with a frigid soil temperature regime (0-8 *C), ustic soil moisture regime with bimodal precipitation of winter snowfall and convective summer rainfall (880 mm yr-1), and an overstory dominated by spruce and fir with dense grass cover in open areas. The catchment is located on the resurgent Redondo Dome that uplifted shortly after the last major eruption of the Valles Caldera 1.2 My ago. The dome includes a complex assemblage of pre-eruptive caldera materials and extant sedimentary rocks embedded within a welded, hydrothermally altered rhyolitic tuff. We sampled a transect of seven soil profiles spanning the dominant east-west aspect of the catchment across a catena with profiles located in summit, backslope, footslope, and toeslope positions. Soil morphology was described in the field and soil samples analyzed using a range of geochemical and mineralogical techniques including quantitative and qualitative x-ray diffraction of bulk samples and particle size fractions, elemental analysis by x-ray fluorescence, and laser particle size analysis. The data indicated strong landscape position control on soil drainage, grading from well-drained summits to poorly-drained toeslope positions based on the presence/absence of redoximorphic features. The drainage patterns were coupled with downslope thickening of dark, organic matter rich surface horizons, likely a function of both in situ organic matter production and downslope colluvial transport of carbon rich surface materials. Mineralogical and geochemical data indicated clear within profile lithologic

  12. Desarrollo de Recuperadores de Energía para Calderas Basados en Elementos Bifásicos Development of Heat Pipes for Boilers Based on Two Phase Elements

    Directory of Open Access Journals (Sweden)

    Georgiy Polupan

    2011-01-01

    Full Text Available Se presenta el diseño de precalentadores de aire compuestos de termosifones bimetálicos para recuperar la energía contenida en los gases de escape en calderas industriales. Se emplea un programa computacional en lenguaje Visual Basic que permite realizar el diseño térmico de precalentadores de aire compactos. Mediante el empleo de este programa, fue posible obtener varias configuraciones de precalentadores de aire, que satisfacen las condiciones de operación de una caldera Cleaver-Brooks CB 250. Se diseñó un precalentador de aire compacto, cuyas dimensiones fueron sólo la quinta parte de las dimensiones de la caldera. Con este diseño se obtuvo un aumento de eficiencia del 5 %.This paper presents the design of air-heaters made of bimetallic thermosyphons to recover the energy contained in the flue gases of industrial boilers. A computer program written in Visual Basic that performs the thermal calculation of different compact air-heaters was used. With the program it was possible to obtain several configurations of air-heaters that satisfy the operating conditions of a Cleaver-Brooks CB 250 boiler. A compact air-heater was designed with dimensions of only the fifth part of the boiler dimension. With this design efficiency increase of 5% was obtained.

  13. Eruption Depths, Magma Storage and Magma Degassing at Sumisu Caldera, Izu-Bonin Arc: Evidence from Glasses and Melt Inclusions

    Science.gov (United States)

    Johnson, E. R.

    2015-12-01

    Island arc volcanoes can become submarine during cataclysmal caldera collapse. The passage of a volcanic vent from atmospheric to under water environment involves complex modifications of the eruption style and subsequent transport of the pyroclasts. Here, we use FTIR measurements of the volatile contents of glass and melt inclusions in the juvenile pumice clasts in the Sumisu basin and its surroundings (Izu-Bonin arc) to investigate changes in eruption depths, magma storage and degassing over time. This study is based on legacy cores from ODP 126, where numerous unconsolidated (250 m), massive to normally graded pumice lapilli-tuffs were recovered over four cores (788C, 790A, 790B and 791A). Glass and clast geochemistry indicate the submarine Sumisu caldera as the source of several of these pumice lapilli-tuffs. Glass chips and melt inclusions from these samples were analyzed using FTIR for H2O and CO2 contents. Glass chips record variable H2O contents; most chips contain 0.6-1.6 wt% H2O, corresponding to eruption depths of 320-2100 mbsl. Variations in glass H2O and pressure estimates suggest that edifice collapse occurred prior-to or during eruption of the oldest of these samples, and that the edifice may have subsequently grown over time. Sanidine-hosted melt inclusions from two units record variably degassed but H2O-rich melts (1.1-5.6 wt% H2O). The lowest H2O contents overlap with glass chips, consistent with degassing and crystallization of melts until eruption, and the highest H2O contents suggest that large amounts of degassing accompanied likely explosive eruptions. Most inclusions, from both units, contain 2-4 wt% H2O, which further indicates that the magmas crystallized at pressures of ~50-100 MPa, or depths ~400-2800 m below the seafloor. Further glass and melt inclusion analyses, including major element compositions, will elucidate changes in magma storage, degassing and evolution over time.

  14. Contrasting plagioclase textures and geochemistry in response to magma dynamics in an intra-caldera rhyolite system, Okataina volcano

    Science.gov (United States)

    Shane, Phil

    2015-05-01

    The changing magmatic dynamics of the rhyolite caldera volcano, Okataina Volcanic Centre, New Zealand, is revealed in plagioclase growth histories. Crystals from the ~ 0.7 ka Kaharoa eruption are characterized by resorbed cores displaying a cellular texture of high-An (> 40) zones partially replaced by low-An (Mg, Sr, and Ti follow the resorption surface and display rimward depletion trends, accompanied by Ba and REE enrichment. The zonation is consistent with fractional crystallization and cooling. The cores display wide trace element diversity, pointing to crystallization in a variety of melts, before transport and mixing into a common magma where the rims grew. Plagioclase from the ~ 36 ka Hauparu eruption display several regrowth zones separated by resorption surfaces, which surround small resorbed cores with a spongy cellular texture of variable An content (An40-50). The crystals display step-wise regrowth of successively higher An, Fe, Mg, and Ti content, consistent with progressive mafic recharge. Two crystal groups are distinguished by trace element chemistry, indicating growth in separate melts and co-occurrence via magma mingling. For plagioclase in both eruption deposits, partition coefficients (D) estimated from crystal rim-groundmass glass analyses, produce melt compositions similar to the array of rock and glass compositions erupted and are consistent with the processes of fractional crystallization and recharge. However, D values estimated from some published formulations based on An content and temperature produce unrealistic melts. The contrasting zoning patterns in plagioclase correspond to the evolutionary history of magmatism at Okataina. Emptying of the magma reservoir following caldera eruption at 46 ka reduced barriers to mafic magma ascent. This is recorded by the frequent resorption and recharge episodes in Hauparu crystals. Subsequent redevelopment of a more silicic reservoir zone (post-26 ka) dampened thermal and mass perturbations

  15. Timescales of magma processes occurred prior to recent Campi Flegrei caldera eruptions: first results from diffusion profiles on plagioclase phenocrysts

    Science.gov (United States)

    D'Antonio, Massimo; Arienzo, Ilenia; Fedele, Lorenzo; Iovine, Raffaella; Carmine Mazzeo, Fabio; Civetta, Lucia; Orsi, Giovanni; Wörner, Gerhard

    2015-04-01

    Knowledge of the timescales of magma rising and stagnation, as well as mingling/mixing processes occurring in the shallow plumbing system of an active volcano is crucial for volcanic hazard assessment and risk mitigation. Among few recently developed methodologies, high-precision, high spatial resolution analysis of major-, minor- and trace elements on zoned phenocrysts through electron microprobe techniques represents a powerful tool to provide good estimates of timescales of pre-eruptive magma rising, stagnation and/or mingling/mixing processes. To this purpose, volcanic rock samples of trachytic composition representative of the Agnano-Monte Spina eruption (4.7 ka CAL BP) occurred at the Campi Flegrei caldera (southern Italy) have been selected. The investigation has been carried out in the framework of Project V2 - Precursori di Eruzioni, funded by the Italian Dipartimento per la Protezione Civile - Istituto Nazionale di Geofisica e Vulcanologia. The investigated rock samples are pumice fragments from which double-polished, 100 µm thick thin sections have been prepared for analytical purposes. Back-scattered electrons (BSE) images have been acquired at the scanning electron microscope (SEM), in order to identify the plagioclase phenocrysts suitable to be analyzed successively, selected among those that best display their zoning. After a careful observation of the BSE images, major-, minor- and selected trace element contents have been determined through combined energy-dispersive and wavelength-dispersive system electron microprobe analyses (EDS-WDS-EMPA) on transects crossing the growth zones of the selected phenocrysts. This methodology has allowed reconstructing the diffusion profile of some key-elements through the growth zones of the investigated phenocrysts. Successively, the diffusion profiles have been combined with textural features obtained through BSE images in order to obtain diffusion models aimed at estimating the timescales of crystals

  16. Hydrothermal fluid flow models of Campi Flegrei caldera, Italy constrained by InSAR surface deformation time series observations

    Science.gov (United States)

    Lundgren, P.; Lanari, R.; Manzo, M.; Sansosti, E.; Tizzani, P.; Hutnak, M.; Hurwitz, S.

    2008-12-01

    Campi Flegrei caldera, Italy, located along the Bay of Naples, has a long history of significant vertical deformation, with the most recent large uplift (>1.5m) occurring in 1983-1984. Each episode of uplift has been followed by a period of subsidence that decreases in rate with time and may be punctuated by brief episodes of lesser uplift. The large amplitude of the major uplifts that occur without volcanic activity, and the subsequent subsidence has been argued as evidence for hydrothermal amplification of any magmatic source. The later subsidence and its temporal decay have been argued as due to diffusion of the pressurized caldera fill material into the less porous surrounding country rock. We present satellite synthetic aperture radar (SAR) interferometry (InSAR) time series analysis of ERS and Envisat data from the European Space Agency, based on exploiting the Small Baseline Subset (SBAS) approach [Berardino et al., 2002]; this allows us to generate maps of relative surface deformation though time, beginning in 1992 through 2007, that are relevant to both ascending and descending satellite orbits. The general temporal behavior is one of subsidence punctuated by several lesser uplift episodes. The spatial pattern of deformation can be modeled through simple inflation/deflation sources in an elastic halfspace. Given the evidence to suggest that fluids may play a significant role in the temporal deformation of Campi Flegrei, rather than a purely magmatic or magma chamber-based interpretation, we model the temporal and spatial evolution of surface deformation as a hydrothermal fluid flow process. We use the TOUGH2-BIOT2 set of numerical codes [Preuss et al., 1999; Hsieh, 1996], which couple multi-phase (liquid-gas) and multi-component (H2O-CO2) fluid flow in a porous or fractured media with plane strain deformation and fluid flow in a linearly elastic porous medium. We explore parameters related to the depth and temporal history of fluid injection, fluid

  17. The Averno 2 fissure eruption: a recent small-size explosive event at the Campi Flegrei Caldera (Italy)

    Science.gov (United States)

    di Vito, Mauro Antonio; Arienzo, Ilenia; Braia, Giuseppe; Civetta, Lucia; D'Antonio, Massimo; di Renzo, Valeria; Orsi, Giovanni

    2011-04-01

    The Averno 2 eruption (3,700 ± 50 a B.P.) was an explosive low-magnitude event characterized by magmatic and phreatomagmatic explosions, generating mainly fall and surge beds, respectively. It occurred in the Western sector of the Campi Flegrei caldera (Campanian Region, South Italy) at the intersection of two active fault systems, oriented NE and NW. The morphologically complex crater area, largely filled by the Averno lake, resulted from vent activation and migration along the NE-trending fault system. The eruption generated a complex sequence of pyroclastic deposits, including pumice fall deposits in the lower portion, and prevailing surge beds in the intermediate-upper portion. The pyroclastic sequence has been studied through stratigraphical, morphostructural and petrological investigations, and subdivided into three members named A through C. Member A was emplaced during the first phase of the eruption mainly by magmatic explosions which generated columns reaching a maximum height of 10 km. During this phase the eruption reached its climax with a mass discharge rate of 3.2 106 kg/s. Intense fracturing and fault activation favored entry of a significant amount of water into the system, which produced explosions driven by variably efficient water-magma interaction. These explosions generated wet to dry surge deposits that emplaced Member B and C, respectively. Isopachs and isopleths maps, as well as areal distribution of ballistic fragments and facies variation of surge deposits allow definition of four vents that opened along a NE oriented, 2 km long fissure. The total volume of magma extruded during the eruption has been estimated at about 0.07 km3 (DRE). The erupted products range in composition from initial, weakly peralkaline alkali-trachyte, to last-emplaced alkali-trachyte. Isotopic data and modeling suggest that mixing occurred during the Averno 2 eruption between a more evolved, less radiogenic stored magma, and a less evolved, more radiogenic magma

  18. Nuevas evidencias geofísicas de la existencia de una caldera cubierta en laguna Pozuelos: Puna norte

    Directory of Open Access Journals (Sweden)

    Claudia B Prezzi

    2010-03-01

    Full Text Available En el extremo sur de la cuenca de laguna de Pozuelos aflora el complejo volcánico Pan de Azúcar. El mismo está integrado por varios centros eruptivos de composición dacítica y morfología dómica que poseen una edad de ~12 Ma. Interpretaciones previas de líneas sísmicas y un relevamiento magnetométrico detallado indicaron la presencia de cuerpos intrusivos no aflorantes. La determinación de la existencia de nuevos cuerpos intrusivos no aflorantes en la zona resulta de interés debido a que: 1 estos complejos volcánicos dacíticos están estrechamente asociados con mineralización de interés económico (forman parte del cinturón estañífero boliviano; y 2 la existencia de una caldera antigua (~ 12 Ma de grandes dimensiones, ahogada bajo la cubierta sedimentaria que rellena la depresión de Pozuelos, ha sido propuesta por distintos autores. Los complejos dómicos representarían las fases magmáticas finales de dicho sistema magmático caldérico. Con la finalidad de determinar la existencia de dicho sistema caldérico y/o de otros cuerpos intrusivos no aflorantes se llevaron a cabo nuevos relevamientos magnetométricos y gravimétricos terrestres detallados. El mapa magnetométrico obtenido presenta conspicuas anomalías positivas y negativas que dominan el sector sur de la cuenca, probablemente asociadas con la presencia de los domos dacíticos aflorantes. La anomalía residual de Bouguer presenta un patrón semicircular, mostrando sólo valores positivos. La curvatura de las señales magnetométricas y gravimétricas fue analizada y se utilizó la deconvolución de Euler para estimar las profundidades a las fuentes causantes de las anomalías detectadas. Los resultados obtenidos hasta el momento apoyan la hipótesis de la existencia de una gran caldera soterrada en la cuenca de Laguna Pozuelos. La identificación de un gran sistema caldérico mioceno medio contribuirá a una mejor comprensión de la evolución magmática de la Puna

  19. Sustainability assessment of geothermal exploitation by numerical modelling: the example of high temperature Mofete geothermal field at Campi Flegrei caldera (Southern Italy)

    Science.gov (United States)

    Carlino, Stefano; Troiano, Antonio; Giulia Di Giuseppe, Maria; Tramelli, Anna; Troise, Claudia; Somma, Renato; De Natale, Giuseppe

    2015-04-01

    The active volcanic area of Campi Flegrei caldera has been the site of many geothermal investigations, since the early XX century. This caldera is characterised by high heat flow, with maximum value > 150 mWm-2, geothermal gradients larger than 200°Ckm-1 and diffuse magmatic gases discharge at the surface. These features encouraged an extensive campaign for geothermal investigation, started in 1939, with many drillings performed at Campanian volcanoes (Campi Flegrei and Ischia) and later at Vesuvius. Several wells aimed to the exploitation of high enthalpy geothermal energy, were drilled in the Campi Flegrei caldera, down to a maximum depth of ~3 km involving mainly two sites (Mofete and S.Vito geothermal fields) located in western and northern sector of caldera respectively. The most interesting site for geothermal exploitation was the Mofete zone, where a number of 4 productive wells were drilled and tested to produce electrical power. Based on data inferred from the productive tests it was established a potential electrical extractable power from Mofete field of at least 10MWe. More recently an empirical evaluation of the whole geothermal potential of the caldera provides a value of more than 1 GWe. The results of AGIP-ENEL exploration at Campi Flegrei highlighted the feasibility of geothermal exploitation. Here, we show for the first time the results of numerical simulations (TOUGH2 code ®) of fluids extraction and reinjection from the Mofete geothermal field, in order to produce at least 5MWe from zero emission power plant (Organic Rankine Cycle type). The simulation is aimed to understand the perturbation of the geothermal reservoir in terms of temperature, pressure change, and possible related seismicity, after different simulated time of exploitation. The modeling is mainly constrained by the data derived from geothermal exploration and productive tests performed since 1979 by AGIP-ENEL Companies. A general assessment of the maximum potential magnitude

  20. Fluid geochemistry and soil gas fluxes (CO2-CH4-H2S) at a promissory Hot Dry Rock Geothermal System: The Acoculco caldera, Mexico

    Science.gov (United States)

    Peiffer, L.; Bernard-Romero, R.; Mazot, A.; Taran, Y. A.; Guevara, M.; Santoyo, E.

    2014-09-01

    The Acoculco caldera has been recognized by the Mexican Federal Electricity Company (CFE) as a Hot Dry Rock Geothermal System (HDR) and could be a potential candidate for developing an Enhanced Geothermal System (EGS). Apart from hydrothermally altered rocks, geothermal manifestations within the Acoculco caldera are scarce. Close to ambient temperature bubbling springs and soil degassing are reported inside the caldera while a few springs discharge warm water on the periphery of the caldera. In this study, we infer the origin of fluids and we characterize for the first time the soil degassing dynamic. Chemical and isotopic (δ18O-δD) analyses of spring waters indicate a meteoric origin and the dissolution of CO2 and H2S gases, while gas chemical and isotopic compositions (N2/He, 3He/4He, 13C, 15N) reveal a magmatic contribution with both MORB- and arc-type signatures which could be explained by an extension regime created by local and regional fault systems. Gas geothermometry results are in agreement with temperature measured during well drilling (260 °C-300 °C). Absence of well-developed water reservoir at depth impedes re-equilibration of gases upon surface. A multi-gas flux survey including CO2, CH4 and H2S measurements was performed within the caldera. Using the graphical statistical analysis (GSA) approach, CO2 flux measurements were classified in two populations. Population A, representing 95% of measured fluxes is characterized by low values (mean: 18 g m- 2 day- 1) while the remaining 5% fluxes belonging to Population B are much higher (mean: 5543 g m- 2 day- 1). This low degassing rate probably reflects the low permeability of the system, a consequence of the intense hydrothermal alteration observed in the upper 800 m of volcanic rocks. An attempt to interpret the origin and transport mechanism of these fluxes is proposed by means of flux ratios as well as by numerical modeling. Measurements with CO2/CH4 and CO2/H2S flux ratios similar to mass ratios

  1. Radiogenic Heat Production in the Gölcük Caldera and Direkli, Isparta Angle (Southwest Anatolia)

    Science.gov (United States)

    Ayten Uyanık, Nurten; Öncü, Ziya; Akkurt, İskender

    2016-04-01

    The radiogenic heat is one of the important parameter due to the radioactivity has existed since beginning of universe as prediction of Big-Bang theory. In this study the radiogenic heat production of the Gölcük caldera and Direkli fields of the Isparta-Turkey, has been investigated. Total of 1390 data were obtained in the study area. The study area is included of the Gölcük volcanism and its around that is located in Isparta province of Turkey's Mediterranean region. The Gölcük volcanism is a young volcanism. Around this volcanism the andesite, trachy andesite, tuff, pumice and such a geological units is available. The data were collected using in-situ measurements with gamm-ray spectrometer. These measurements were covered natural radioactive elements (Uranium U, Thorium Th and Potassium K). Radiogenic heat production values were calculated using the literature relationships and in-situ measurement values of these radioactive elements. Radiogenic heat map of study area were obtained using radiogenic heat production values. In the map the red zone areas shows highest heat values while green zones areas of the map presents lowest heat values. Key words: Radioactive elements, radiogenic heat, map, Gölcük-Direkli(Isparta), Turkey

  2. Geochemical Features of the Hubin Spring Gases from the Northern Caldera Lake of the Tianchi Volcano, Changbai Mountains

    Institute of Scientific and Technical Information of China (English)

    Gao Ling; Shangguan Zhiguan; Wei Haiquan; Zhao Ciping

    2011-01-01

    This paper deals with geochemical features of gas emitted from the Hubin Springs. The Hubin Springs zone, a strong thermal emission zone, is are locatedd at the north edge of the Tianchi caldera lake. Very young deposits with uncertain eruption date are found on the top area of the Tianwenfeng, which might have been formed in one of the recent eruptions or the Millennium Eruption. It is of significance to study the geochemistry features of the emitting gas from the Hubin Springs to understand the activities of the Tianchi Volcano. This paper systematically sampled and analyzed the gases emitted from the Hubin Springs and discussed their geochemistry features. The results show that there is a high content of deep derived gases, such as CO2, He, CH4 and Ar in Hubin Springs zone. The isotopic ratio of He lies between 4. 18 and 5. 95 Ra. The averaged mantle derived gas content calculated from the ^4He/2^20Ne ratio and He content reaches 67.1%. All these show that the Hubin Springs are located on a special belt of deep gases released in high intensity and large scale. The spatial distribution of Helium isotope is characterized by concavity, showing that this special area may be related to the volcanic edifice. It is highly possible that the released gases represent the residual gas samples of the latest eruptions from the Tianchi Volcano. However more detailed studies are demanded.

  3. Three-dimensional electrical resistivity model of the hydrothermal system in Long Valley Caldera, California, from magnetotellurics

    Science.gov (United States)

    Peacock, Jared R.; Mangan, Margaret T.; McPhee, Darcy K.; Wannamaker, Phil E.

    2016-01-01

    Though shallow flow of hydrothermal fluids in Long Valley Caldera, California, has been well studied, neither the hydrothermal source reservoir nor heat source has been well characterized. Here a grid of magnetotelluric data were collected around the Long Valley volcanic system and modeled in 3-D. The preferred electrical resistivity model suggests that the source reservoir is a narrow east-west elongated body 4 km below the west moat. The heat source could be a zone of 2–5% partial melt 8 km below Deer Mountain. Additionally, a collection of hypersaline fluids, not connected to the shallow hydrothermal system, is found 3 km below the medial graben, which could originate from a zone of 5–10% partial melt 8 km below the south moat. Below Mammoth Mountain is a 3 km thick isolated body containing fluids and gases originating from an 8 km deep zone of 5–10% basaltic partial melt.

  4. Near real-time monitoring of volcanic surface deformation from GPS measurements at Long Valley Caldera, California

    Science.gov (United States)

    Ji, Kang Hyeun; Herring, Thomas A.; Llenos, Andrea L.

    2013-01-01

    Long Valley Caldera in eastern California is an active volcanic area and has shown continued unrest in the last three decades. We have monitored surface deformation from Global Positioning System (GPS) data by using a projection method that we call Targeted Projection Operator (TPO). TPO projects residual time series with secular rates and periodic terms removed onto a predefined spatial pattern. We used the 2009–2010 slow deflation as a target spatial pattern. The resulting TPO time series shows a detailed deformation history including the 2007–2009 inflation, the 2009–2010 deflation, and a recent inflation that started in late-2011 and is continuing at the present time (November 2012). The recent inflation event is about four times faster than the previous 2007–2009 event. A Mogi source of the recent event is located beneath the resurgent dome at about 6.6 km depth at a rate of 0.009 km3/yr volume change. TPO is simple and fast and can provide a near real-time continuous monitoring tool without directly looking at all the data from many GPS sites in this potentially eruptive volcanic system.

  5. Aquifer Recharge Estimation through Atmospheric Chloride Mass Balance at Las Cañadas Caldera, Tenerife, Canary Islands, Spain

    Directory of Open Access Journals (Sweden)

    Rayco Marrero-Diaz

    2015-05-01

    Full Text Available The atmospheric chloride mass balance (CMB method was used to estimate net aquifer recharge in Las Cañadas Caldera, an endorheic summit aquifer area about 2000 m a.s.l. with negligible surface runoff, which hosts the largest freshwater reserve in Tenerife Island, Canary Islands, Spain. The wet hydrological year 2005–2006 was selected to compare yearly atmospheric chloride bulk deposition and average chloride content in recharge water just above the water table, both deduced from periodical sampling. The potential contribution of chloride to groundwater from endogenous HCl gas may invalidate the CMB method. The chloride-to-bromide molar ratio was an efficient tracer used to select recharge water samples having atmospheric origin of chloride. Yearly net aquifer recharge was 631 mm year−1, i.e., 69% of yearly precipitation. This result is in agreement with potential aquifer recharge estimated through an independent lumped-parameter rainfall-runoff model operated by the Insular Water Council of Tenerife. This paper illustrates basic procedures and routines to use the CMB method for aquifer recharge in active volcanic oceanic islands having sparse-data coverage and groundwater receiving contribution of endogenous halides.

  6. Lower Pliensbachian caldera volcanism in high-obliquity rift systems in the western North Patagonian Massif, Argentina

    Science.gov (United States)

    Benedini, Leonardo; Gregori, Daniel; Strazzere, Leonardo; Falco, Juan I.; Dristas, Jorge A.

    2014-12-01

    In the Cerro Carro Quebrado and Cerro Catri Cura area, located at the border between the Neuquén Basin and the North Patagonian Massif, the Garamilla Formation is composed of four volcanic stages: 1) andesitic lava-flows related to the beginning of the volcanic system; 2) basal massive lithic breccias that represent the caldera collapse; 3) voluminous, coarse-crystal rich massive lava-like ignimbrites related to multiple, steady eruptions that represent the principal infill of the system; and, finally 4) domes, dykes, lava flows, and lava domes of rhyolitic composition indicative of a post-collapse stage. The analysis of the regional and local structures, as well as, the architectures of the volcanic facies, indicates the existence of a highly oblique rift, with its principal extensional strain in an NNE-SSW direction (˜N10°). The analyzed rocks are mainly high-potassium dacites and rhyolites with trace and RE elements contents of an intraplate signature. The age of these rocks (189 ± 0.76 Ma) agree well with other volcanic sequences of the western North Patagonian Massif, as well as, the Neuquén Basin, indicating that Pliensbachian magmatism was widespread in both regions. The age is also coincident with phase 1 of volcanism of the eastern North Patagonia Massif (188-178 Ma) represented by ignimbrites, domes, and pyroclastic rocks of the Marifil Complex, related to intraplate magmatism.

  7. Near real-time monitoring of volcanic surface deformation from GPS measurements at Long Valley Caldera, California

    Science.gov (United States)

    Ji, Kang Hyeun; Herring, Thomas A.; Llenos, Andrea L.

    2013-03-01

    Long Valley Caldera in eastern California is an active volcanic area and has shown continued unrest in the last three decades. We have monitored surface deformation from Global Positioning System (GPS) data by using a projection method that we call Targeted Projection Operator (TPO). TPO projects residual time series with secular rates and periodic terms removed onto a predefined spatial pattern. We used the 2009-2010 slow deflation as a target spatial pattern. The resulting TPO time series shows a detailed deformation history including the 2007-2009 inflation, the 2009-2010 deflation, and a recent inflation that started in late-2011 and is continuing at the present time (November 2012). The recent inflation event is about four times faster than the previous 2007-2009 event. A Mogi source of the recent event is located beneath the resurgent dome at about 6.6 km depth at a rate of 0.009 km3/yr volume change. TPO is simple and fast and can provide a near real-time continuous monitoring tool without directly looking at all the data from many GPS sites in this potentially eruptive volcanic system.

  8. Applied technology in the solution of geothermal drilling problems of deep wells in La Primavera caldera (Mexico)

    Science.gov (United States)

    Santoyo-Gutiérrez, S.; García, A.; Morales, M.; Perezyera, J.; Rosas, A.

    1991-07-01

    The drilling of deep wells in the La Primavera caldera has evidenced a highly complex and hazardous problematic situation due to considerable losses of drilling fluids. Such large losses have not occurred in any other geothermal field in the world. These losses are due mainly to the structural conditions of the geological formations which are penetrated. The technology employed in the construction of deep wells has played a very important role in the solution to these problems. Field case histories describe the effectiveness of the developments of drilling fluids and cement materials in cavernous formations with severe lost-circulation problems. A processed clay bentonite was developed whose high performance and rapid hydration characteristics allowed a reduction of up to 5 hours in the drilling fluid conditioning time. Also, useful results were obtained through the development of a granular plugging mixture which maintained sealing properties at 70 kg/cm 2 under cavernous simulated conditions. This granular plugging mixture kept losses of the volume of drilling fluid under 8% with respect to the total volume. Special cement plugs with thixotropic behavior allowed the handling and placement of this slurry in the problematic zone. The CaSO 4 addition to the cement slurry was optimized so that a placement time of 30 min could be obtained. Additionally, the mechanical compressive strength values of this special cement plug ranged from 50 to 100 kg/cm 2.

  9. Task 3: Evaluation of mineral resource potential, caldera geology, and volcano-tectonic framework at and near Yucca Mountain

    Energy Technology Data Exchange (ETDEWEB)

    Weiss, S.I.; Noble, D.C.; Larson, L.T. [Univ. of Nevada, Reno, NV (United States)

    1994-12-31

    This report summarizes the work of Task 3 that was initially discussed in our monthly reports for the period October 1, 1993 through September 30, 1994, and is contained in our various papers and abstracts, both published and in press or currently in review. Our efforts during this period have involved the continuation of studies begun prior to October, 1993, focussed mainly on aspects of the caldera geology, magmatic activity, hydrothermal mineralization and extensional tectonics of the western and central parts of the southwestern Nevada volcanic field (SWNVF), studies of the subsurface rocks of Yucca Mountain utilizing drill-hole sampled obtained in 1991 and 1992, and studies of veins and siliceous ledges cropping out in northwestern Yucca Mountain. These veins and ledges provide evidence for near-surface hydrothermal activity in northwestern Yucca Mountain during the Crater Flat Tuff period of volcanism. During the period of this report we have concentrated our efforts on the production and publication of documents summarizing many of the data, interpretations and conclusions of Task 3 studies pertaining to hydrothermal activity and mineralization in the Yucca Mountain region and their relations to volcanism and tectonic activity. The resulting two manuscripts for journal publication and a compilation of radiometric age and trace-element geochemical data are appended to this report.

  10. Casos curiosos, peculiaridades y formas alternativas de anotar la música en el área hispánica en el siglo XVII. Procesos de intercambio entre lo culto y lo popular

    Directory of Open Access Journals (Sweden)

    Ezquerro Esteban, Antonio

    2001-12-01

    Full Text Available The present paper deals with an approach to some cases on Spanish 17th century Music notated in a wide variety of forms. The graphic image of these cases, will help us to better understand the adopted shapes of music, in order to reach a better "circulation" among the chapel masters and composers of the period. And that concerns not only to music, but also to the accompanying poems, or other "working models" in further elaborations, such as musical incipits, etc. Then, this contribution goes to think about on the strong influence of the Catholic church -as main patron of music in Spain- on the conformed traditions and customs of Hispanic composition, as well as on the repertories, and how these "manners" conditioned peculiar ways of notating music, creating a big variety of manuscript copies. And last but not least, the paper studies possible interchanges between the "cultivated" and "popular" surroundings of music, trough an blurred round trip, that it is needed, again, to clarify today.

    El presente artículo pretende realizar una aproximación a algunos casos de música hispana del siglo XVII anotada de las formas más variadas, no por poco frecuentes, menos importantes. Se presenta la imagen "gráfica" de algunas de las múltiples vías que la música de la época llegó a adoptar para "circular" libremente entre los maestros de capilla y compositores (y no sólo la música, sino los textos que la debían acompañar, u otros patrones de trabajo y elaboración posterior, como sus incipits musicales, etc.. Se reflexiona brevemente sobre el enorme influjo del mecenazgo eclesiástico sobre las tradiciones y "costumbres" de composición hispanas, así como sobre los repertorios, y cómo estos "modos de hacer", condicionaron peculiares formas de anotar la música hispánica en una gran variedad de copias manuscritas. Por último, se abordan en este contexto posibles intercambios entre el entorno musical "culto" y el "popular", en

  11. Avaliacao da Relacao entre a Doenca Hepatica Nao Gordurosa e CAD utilizando TCMF

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    Duran Efe

    2014-01-01

    Full Text Available Fundamento: Alguns fatores de risco para a aterosclerose são acompanhados pela doença hepática gordurosa não alcoólica (DHGNA. Desejamos usar a tomografia computadorizada multi-fatias (TCMF como a técnica para encontrar relação entre a DHGNA e a doença arterial coronariana (DAC. Objetivo: A relação entre a DHGNA e a DAC foi investigada através de TCMF. Métodos: Um total de 372 indivíduos com ou sem sintomas cardíacos, que foram submetidos à angiografia por TCMF, foram incluídos no estudo. Os pacientes foram divididos em dois grupos, de acordo com a presença da DHGNA. Os segmentos arteriais coronarianos foram avaliados visualmente via angiografia por TCMF. Com base no grau de estenose arterial coronariana, aqueles com placas ausentes ou mínimas foram considerados como normais, enquanto aqueles que apresentavam estenose de menos do que 50% e no mínimo uma placa foram considerados como portadores da doença arterial coronariana não obstrutiva (não-obsDAC. Os pacientes que apresentaram no mínimo uma placa e estenose arterial coronariana de 50% ou mais foram considerados como portadores de doença arterial coronariana obstrutiva (obsDAC. A DHGNA foi determinada de acordo com o protocolo de TCMF, utilizando a densidade hepática. Resultados: De acordo com a densidade hepática, o número de pacientes com doença hepática gordurosa não alcoólica (grupo 1 foi de 204 (149 homens, 54,8% e com fígado normal (grupos 2 foi de 168 (95 homens, 45.2%. Houve 50 (24,5% não-obsDAC e 57 (27,9% casos de obsDAC no Grupo 1, e 39 (23,2% não-obsDAC e 23 (13,7% casos de obsDAC no Grupo 2. Conclusões: O presente estudo utilizando TCMF demonstrou que a frequência da doença arterial coronariana em pacientes com NAFDL foi significativamente superior do que nos pacientes em NAFDL.

  12. DETERMINANTES DEL LOGRO ESCOLAR EN MÉXICO. Primeros resultados utilizando la prueba ENLACE media superior

    Directory of Open Access Journals (Sweden)

    Rafael E. de Hoyos

    2012-01-01

    Full Text Available Aunque los años de escolaridad de los mexicanos aumentaron significativamente en los pasados 20 años, la calidad del sistema educativo —un determinante importante del crecimiento económico de largo plazo— dista mucho de ser satisfactorio. Utilizando los resultados de la primera prueba estandarizada en educación media superior (ENLACE-MS, este estudio muestra que un modelo que incluye las características del hogar, individuales, institucionales y escolares puede explicar más de 40% de las diferencias observadas en las calificaciones de matemáticas. Desde el punto de vista de la política pública, los resultados de este trabajo sugieren que, a fin de aumentar la calidad de la educación, las autoridades educativas deberían concentrarse en mejorar la infraestructura escolar, la calidad de los docentes y la relación entre los estudiantes y las autoridades escolares.

  13. Modelaje geológico y de recursos del yacimiento Pastelillo utilizando el krigeaje de indicadores

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    José Q. Cuador-Gil

    2005-03-01

    Full Text Available En ocasiones la complejidad y variabilidad de un yacimiento mineral hace dificil establecer dominios geológicos homogéneos que puedan ser utilizados para aplicar control geológico a la estimación de los parámetros más relevantes. La imposibilidad de crear un modelo geológico con unidades bien definidas conduce a trabajar con poblaciones heterogéneas, lo cual degrada considerablemente la calidad de las estimaciones. Tal es el caso de Pastelillo, yacimiento de materia prima para cemento, en el que es difícil reproducir la geometría de los distintos tipos tecnológicos utilizando el método tradicional de correlación geológica. Las distintas litologías que conforman el yacimientos están completamente mezcladas tanto en el plano como en la vertical y estos frecuentes cambios faciales provocan una gran variabilidad litológica y tecnológica en el yacimiento. Teniendo en cuenta lo anterior se propone emplear un método de interpolación espacial que permita hacer estimaciones en presencia de poblaciones complejas. En el artículo se establece un modelo tecnológico y de recursos para el yacimiento Pastelillo a partir del empleo de una técnica de estimación de la geoestadística no lineal: el krigeaje de indicadores.

  14. Biossorção de azul de metileno utilizando resíduos agroindustriais

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    Andressa C. Honorato

    2015-07-01

    Full Text Available O presente trabalho avaliou a capacidade de adsorção do corante azul de metileno nos resíduos da palha de milho e da bainha do palmito pupunha in natura. A caracterização dos resíduos foi determinada utilizando-se a microscopia eletrônica de varredura e espectroscopia na região do infravermelho a qual indicou a presença de grupos carboxílicos, hidroxila e carbonila. O tempo necessário para que o sistema atingisse o equilíbrio para ambos os resíduos foi de 240 min, seguindo uma cinética descrita pelo modelo de pseudo-segunda ordem. A capacidade máxima de adsorção foi de 102,8 mg g-1 para o resíduo da palha de milho, seguindo o modelo de isoterma de Langmuir e 50,9 mg g-1 para o resíduo de palmito pupunha, sendo que o modelo que melhor se ajusta foi Freundlich. Desta forma, esses resíduos são promissores para a adsorção do corante azul de metileno em efluentes.

  15. DESARROLLO DE APIO MINIMAMENTE PROCESADO FORTIFICADO CON VITAMINA E, UTILIZANDO LA INGENIERIA DE MATRICES

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    YISELL JOHAN MARTELO CASTAÑO

    2011-01-01

    Full Text Available El objetivo de este trabajo fue desarrollar un producto minimamente procesado fortificado con vitamina E, a partir de apio (Apium graveolens L. var.dulce, utilizando la ingenieria de matrices como metodologia de obtencion de alimentos funcionales. Trozos de apio impregnados al vacio con dl¿¿tocoferol acetato emulsificado en una solucion isotonica al vegetal de NaCl, 1,2%, fueron evaluados en funcion del tiempo de almacenamiento y el envasado (con y sin vacio, en terminos de la cuantificacion de sus propiedades fisicoquimicas, color, textura, estabilidad de la vitamina E y caracteristicas sensoriales. Se formulo la emulsion con el objetivo de adicionar teoricamente un 73% del Valor Diario Recomendado (VDR vitamina E/100 g de apio fresco y su cuantificacion se realizo por HPLC. La respuesta a la impregnacion en la matriz fue de 12,10+-1,15%, lo cual permitio alcanzar un 112% VDR vitamina E/100g apio fresco, manteniendose este contenido durante el almacenamiento de 9 dias en ambos tipos de envasado. Los parametros fisicoquimicos del producto fueron afectados por la IV, el tiempo y el envasado, manteniendo su coloracion verdosa y presentando disminucion en la firmeza. La ingenieria de matrices constituye una metodologia efectiva para el desarrollo de apio minimamente procesado adicionado con vitamina E.

  16. Monitoramento do processo de compressão de ibuprofeno utilizando controle estatístico

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    Sara Elis Bianchi

    2012-04-01

    Full Text Available O Controle Estatístico de Processo (CEP é uma ferramenta bastante utilizada para auxiliar no controle da qualidade de parâmetros físicos como peso médio, dureza e friabilidade. Através das cartas de controle é possível detectar desvios dos parâmetros do processo, reduzindo a quantidade de produtos fora da especificação e, consequentemente, os custos da produção. A avaliação de trinta lotes de ibuprofeno em uma indústria farmacêutica, utilizando controle estatístico de processo, permitiu o fornecimento de informações imprescindíveis para a investigação detalhada dos pontos críticos do processo, diagnosticando as possíveis não conformidades na etapa de compressão deste fármaco. Desta maneira, podem-se propor atividades de melhoria, através da identificação e eliminação das causas especiais de variação no processo, com a finalidade de produzir comprimidos com qualidade.

  17. UTILIZANDO O MÉTODO TODIM PARA AVALIAR AS MELHORES EMPRESAS PARA TRABALHAR

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    Renato Teixeira da Silva

    2011-06-01

    Full Text Available Este artigo expõe uma nova proposta de ordenação das 5 melhores empresas para trabalhar em termos de qualidade do ambiente de trabalho e qualidade na gestão de pessoas utilizando-se do método TODIM como suporte científico para tal. A ordenação inicial, proposta pela revista Você/SA Exame, utiliza como método classificador o índice de felicidade no trabalho, uma soma ponderada de índices resultantes da percepção dos funcionários, das práticas da empresa e da constatação feita por jornalistas em visitas às empresas. Este trabalho, que utiliza o método TODIM, considera esses itens como critérios de avaliação e realiza uma análise comparativa das alternativas. Ao final, é executada uma comparação entre as ordenações e uma análise de sensibilidade, analisando as especificidades de cada método de ordenação e a consistência de seus resultados.

  18. Cálculo del factor de efectividad utilizando colocación ortogonal sobre elementos finitos

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    Javier Fontalvo Alzate

    2011-02-01

    Full Text Available En el presente documento se resuelve el problema del cálculo del factor de efectividad para la transferencia de masa y calor con reacción química en un pellet catalítico utilizando una técnica adecuada especialmente para números de Thiele elevados en donde la solución se restringe a una pequeña zona muy cercana a la superficie. La técnica aprovecha la rapidez de convergencia de la colocación ortogonal y la facilidad de ubicación de elementos en zonas en donde se presentan grandes gradientes del método para las diferencias finitas. La eficiencia del método está basada en la utilización del método LV para la descomposición de matrices. Se muestran comparaciones con otros métodos numéricos de solución del problema.

  19. Crónica de los intercambios entre los grupos humanos paleolíticos. La contribución del arte para el periodo 20000-12000 años BP

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    Georges SAUVET

    2009-08-01

    Full Text Available RESUMEN: En el transcurso de sus ciclos estacionales, los cazadores-recolectores del Paleolítico superior frecuentemente entraban en contacto con otros grupos. Testimonio de ello son la difusión de ciertas materias primas y los intercambios de bienes materiales y de las habilidades tecnológicas, pero los intercambios socioculturales no pueden evaluarse más que a través del compartimiento de valores simbólicos, revelado, principalmente, por la creación de obras de carácter artístico (arte mueble, arte rupestre y objetos de adorno personal. En un cuadro cronológicamente restringido (entre 20000 y 12000 BP y un espacio limitado (desde el norte de España al sudoeste de Francia, hemos investigado los argumentos temáticos, estilísticos y técnicos que permiten evaluar el grado de ósmosis sociocultural entre los grupos que vivían en este vasto territorio. Nuestra encuesta concluye con una visión contrastada de la historia de estas sociedades. Ciertos caracteres dejan entrever particularismos regionales de naturaleza idiosincrásica, pero, por el contrario y al menos para ciertos periodos, otros muestran una unificación de los sistemas de representación, que debe reflejar una homogeneización en las formas de organización social. Así, después de un periodo bastante largo, durante el que la Región Cantábrica desarrolló un sistema propio, independiente del de las regiones de Aquitania y Nortepirenaica, se asiste en el conjunto del territorio y durante el Magdaleniense medio, a una aproximación entre las concepciones artísticas, que probablemente sea la consecuencia de una intensificación de los contactos y del establecimiento de redes sociales operativas. Hacia el final del Magdaleniense, esta unidad de conjunto se disuelve progresivamente, a causa de una expansión territorial que hizo que los contactos se produjeran entre poblaciones cada vez más alejadas. En el plano metodológico, las obras de arte plástico son

  20. Localización y mapeo simultáneo (SLAM) utilizando un sensor de profundidad por infrarrojo

    OpenAIRE

    2015-01-01

    El propósito de este proyecto es diseñar y desarrollar un robot que implemente una solución al problema de SLAM (Simultaneous Localization And Mapping), utilizando una cámara y un sensor de profundidad por infrarrojo (Kinect). Para este fin se dividió el proyecto en tres etapas: a) robot: estructura con notebook y Kinect; b) software de procesamiento de imágenes; c) Mapeo y localización.

  1. Evaluación de un generador de vapor de la industria petroquímica utilizando radiotrazadores

    OpenAIRE

    2005-01-01

    El presente estudio consistió en evaluar un generador de vapor de la industria petroquímica, utilizando ácido oleico marcado con Yodo-131 como radiotrazador para la fase hidrocarburo e Indio-113m para la fase acuosa, con la finalidad de determinar eventuales fugas durante el transporte de agua y de los fondos de la columna principal durante sus respectivos recorridos en el interior del sistema.

  2. Caldera La Peligrosa (47º15´S, 71°40´O: un evento clave en la Provincia Silícea Chon Aike La Peligrosa caldera (47°15´ 5,71°40´W: A key event in the siliceous province of Chon Aike

    Directory of Open Access Journals (Sweden)

    Patricia Sruoga

    2010-05-01

    Full Text Available En el área ubicada entre el lago Ghío y la sierra Colorada, en la Cordillera Patagónica Austral, aflora una secuencia piroclástico- lávica de carácter proximal correspondiente al Complejo El Quemado, de edad jurásica tardía. A partir del análisis integrado de litofacies y estructuras se llevó a cabo la reconstrucción de la arquitectura volcánica. Se han reconocido cuatro litofacies ignimbríticas y una litofacies lávico-hipabisal de composición riolítica, cuyo emplazamiento estuvo controlado por un sistema de fallas transtensionales de orientación NNO predominante. Se propone un modelo de evolución de la caldera La Peligrosa en tres etapas:1 pre-colapso, durante la cual se define una zona dilatante propicia para la formación de la caldera, con incipiente fallamiento en bloques, 2 colapso, cuando ocurre el emplazamiento de potentes ignimbritas cristalinas y megabrechas en una cubeta de subsidencia progresiva, controlada por un régimen transtensional con dirección de extensión NE y 3 post-colapso, durante la cual se produce el derrame de lavas junto con la intrusión de cuerpos dómicos, bajo condiciones de extensión oblicua con dirección de extensión NO. El pasaje de un ambiente transtensional a condiciones de extensión oblicua acompañó las últimas etapas del desarrollo de la caldera representando un notable cambio en las condiciones de la deformación en tiempos jurásicos. La formación y desarrollo de la caldera La Peligrosa puede ser considerada como un evento clave para entender los mecanismos eruptivos del vasto volcanismo ignimbrítico de la Provincia Silícea Chon Aike.In the area located between Ghío lake and sierra Colorada, in Cordillera Patagónica Austral, the Late Jurassic El Quemado Complex is represented by vent-facies of pyroclastic and lava origin. A reconstruction of the volcanic architecture has been carried out based on the integrated study of the lithofacies and the structures. Four ignimbritic

  3. Distribución y abundancia de larvas de Heterocarpus reedi Bahamonde, 1955, Cervimunida johni Porter, 1903 y Pleuroncodes monodon (H. Milne Edwards, 1837, frente a Coquimbo y Caldera, Chile Distribution and abundance of Heterocarpus reedi Bahamonde, 1955, Cervimunida johni Porter, 1903, and Pleuroncodes monodon (H. Milne Edwards, 1837, larvae off Coquimbo and Caldera, Chile

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    Armando Mujica

    2011-01-01

    Full Text Available Como aporte a la dinámica poblacional de especies que constituyen recursos pesqueros, se analizaron 160 muestras de zooplancton obtenidas con redes Bongo en 40 estaciones oceanógraficas entre Caldera y Coquimbo, en octubre y diciembre de 2005. De ellas se separó la totalidad de las larvas de crustáceos decápodos y se identificaron las de Heterocarpus reedi, Cervimunida johni y Pleuroncodes monodon. Las mayores abundancias de zoeas tempranas de las tres especies se encontraron en octubre en la zona de Coquimbo, mientras que en diciembre predominaron los estados más avanzados de desarrollo. En la zona de Caldera, en ambos meses de muestreo, predominaron los estados avanzados de desarrollo de H. reedi y P. monodon y zoeas tempranas de C. johni. La frecuencia de ocurrencia de las larvas de H reedi en la zona de Coquimbo fue similar en ambos meses, mientras que en la zona de Caldera fue mayor en octubre. La frecuencia de ocurrencia de las larvas de P. monodon y C. johni fue mayor en octubre en ambas zonas. Todas las megalopas capturadas en las dos zonas y meses de muestreo corresponden sólo a un morfotipo, con características morfológicas similares a los juveniles más pequeños de P. monodon. Sobre la base de la distribución y abundancia de larvas de las tres especies, se postula que el desove ocurre antes en la zona de Caldera que en la de Coquimbo, principalmente en zonas próximas a la costa, dada las diferencias de abundancia de los estados de desarrollo.To better understand the population dynamics of fishery resource species, 160 zooplankton samples were obtained with a Bongo net at 40 oceanographic stations around Caldera and Coquimbo in October and December, 2005, and analyzed. All crustacean decapod larvae were sorted, and Heterocarpus reedi, Cervimunida johni, and Pleuroncodes monodon larvae were identified. For all three species, the highest abundances of early zoea were found in October in Coquimbo, whereas advanced larval

  4. Mechanisms and timescales of generating eruptible rhyolitic magmas at Yellowstone caldera from zircon and sanidine geochronology and geochemistry

    Science.gov (United States)

    Stelten, Mark; Cooper, Kari M.; Vazquez, Jorge A.; Calvert, Andrew T.; Glessner, Justin G

    2015-01-01

    We constrain the physical nature of the magma reservoir and the mechanisms of rhyolite generation at Yellowstone caldera via detailed characterization of zircon and sanidine crystals hosted in three rhyolites erupted during the (ca. 170 – 70 ka) Central Plateau Member eruptive episode – the most recent post-caldera magmatism at Yellowstone. We present 238U-230Th crystallization ages and trace-element compositions of the interiors and surfaces (i.e., unpolished rims) of individual zircon crystals from each rhyolite. We compare these zircon data to 238U- 230Th crystallization ages of bulk sanidine separates coupled with chemical and isotopic data from single sanidine crystals. Zircon age and trace-element data demonstrate that the magma reservoir that sourced the Central Plateau Member rhyolites was long-lived (150 – 250 kyr) and genetically related to the preceding episode of magmatism, which occurred ca. 256 ka. The interiors of most zircons in each rhyolite were inherited from unerupted material related to older stages of Central Plateau Member magmatism or the preceding late Upper Basin Member magmatism (i.e., are antecrysts). Conversely, most zircon surfaces crystallized near the time of eruption from their host liquids (i.e., are autocrystic). The repeated recycling of zircon interiors from older stages of magmatism demonstrates that sequentially erupted Central Plateau Member rhyolites are genetically related. Sanidine separates from each rhyolite yield 238U-230Th crystallization ages at or near the eruption age of their host magmas, coeval with the coexisting zircon surfaces, but are younger than the coexisting zircon interiors. Chemical and isotopic data from single sanidine crystals demonstrate that the sanidines in each rhyolite are in equilibrium with their host melts, which considered along with their near-eruption crystallization ages suggests that nearly all CPM sanidines are autocrystic. The paucity of antecrystic sanidine crystals relative to

  5. Evidence for a deep crustal hot zone beneath the Diamante Caldera-Maipo volcanic complex, Southern Volcanic Zone

    Science.gov (United States)

    Drew, D.; Murray, T.; Sruoga, P.; Feineman, M. D.

    2010-12-01

    Subduction zones at convergent continental margins are dynamic environments that control the long-term evolution and interaction of the crust and residual mantle. The Southern Volcanic Zone (SVZ) of the Andes formed as a result of volcanic activity and uplift due to the eastern subduction of the Nazca Plate beneath the South American Plate. Maipo and neighboring volcanoes in the northern SVZ are unique in that the continental crust is exceptionally thick (~50 km), causing the mantle-derived magma to stall and interact with the crust at multiple levels prior to eruption. Maipo is an andesite/dacite stratovolcano that lies within the Diamante Caldera, which formed approximately 450 Ka during an explosive eruption that produced 350 km3 of rhyolitic ignimbrite. Following post-caldera reactivation Maipo has undergone a complex evolution, first erupting 86 Ka and experiencing seven eruptive events extending to historic times. The Maipo lavas represent a unique geochemical evolution resulting from fractional crystallization, crustal assimilation, and magma mixing in the lower and upper crust. By analyzing trace element compositions, major element compositions, and 87Sr/86Sr ratios in sixteen samples, we have begun to constrain the complex geochemical processes that formed this volcano and contribute to the differentiation of Andean continental crust. The major element analysis of the samples reflects the extent of differentiation resulting in dacite to andesite volcanic rock, and was used to distinguish between the seven eruptive events. The trace elements and Sr isotope ratios reflect the composition of the source rock, the extent of crustal assimilation, and the crystallization of minerals from the resulting mantle derived magma. The SiO2 weight percent (ranging from 54.3 to 68.5%) and 87Sr/86Sr ratios (0.7048 to 0.7057) show a linear correlation nearly identical to that reported by Hildreth and Moorbath (1988, CMP 98, 455-489) for nearby Cerro Marmolejo, suggesting a

  6. Multilocus sequence analysis of Thermoanaerobacter isolates reveals recombining, but differentiated, populations from geothermal springs of the Uzon Caldera, Kamchatka, Russia

    Science.gov (United States)

    Wagner, Isaac D.; Varghese, Litty B.; Hemme, Christopher L.; Wiegel, Juergen

    2013-01-01

    Thermal environments have island-like characteristics and provide a unique opportunity to study population structure and diversity patterns of microbial taxa inhabiting these sites. Strains having ≥98% 16S rRNA gene sequence similarity to the obligately anaerobic Firmicutes Thermoanaerobacter uzonensis were isolated from seven geothermal springs, separated by up to 1600 m, within the Uzon Caldera (Kamchatka, Russian Far East). The intraspecies variation and spatial patterns of diversity for this taxon were assessed by multilocus sequence analysis (MLSA) of 106 strains. Analysis of eight protein-coding loci (gyrB, lepA, leuS, pyrG, recA, recG, rplB, and rpoB) revealed that all loci were polymorphic and that nucleotide substitutions were mostly synonymous. There were 148 variable nucleotide sites across 8003 bp concatenates of the protein-coding loci. While pairwise FST values indicated a small but significant level of genetic differentiation between most subpopulations, there was a negligible relationship between genetic divergence and spatial separation. Strains with the same allelic profile were only isolated from the same hot spring, occasionally from consecutive years, and single locus variant (SLV) sequence types were usually derived from the same spring. While recombination occurred, there was an “epidemic” population structure in which a particular T. uzonensis sequence type rose in frequency relative to the rest of the population. These results demonstrate spatial diversity patterns for an anaerobic bacterial species in a relative small geographic location and reinforce the view that terrestrial geothermal springs are excellent places to look for biogeographic diversity patterns regardless of the involved distances. PMID:23801987

  7. Cultivation and complete genome sequencing of Gloeobacter kilaueensis sp. nov., from a lava cave in Kilauea Caldera, Hawai'i.

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    Jimmy H W Saw

    Full Text Available The ancestor of Gloeobacter violaceus PCC 7421(T is believed to have diverged from that of all known cyanobacteria before the evolution of thylakoid membranes and plant plastids. The long and largely independent evolutionary history of G. violaceus presents an organism retaining ancestral features of early oxygenic photoautotrophs, and in whom cyanobacteria evolution can be investigated. No other Gloeobacter species has been described since the genus was established in 1974 (Rippka et al., Arch Microbiol 100:435. Gloeobacter affiliated ribosomal gene sequences have been reported in environmental DNA libraries, but only the type strain's genome has been sequenced. However, we report here the cultivation of a new Gloeobacter species, G. kilaueensis JS1(T, from an epilithic biofilm in a lava cave in Kīlauea Caldera, Hawai'i. The strain's genome was sequenced from an enriched culture resembling a low-complexity metagenomic sample, using 9 kb paired-end 454 pyrosequences and 400 bp paired-end Illumina reads. The JS1(T and G. violaceus PCC 7421(T genomes have little gene synteny despite sharing 2842 orthologous genes; comparing the genomes shows they do not belong to the same species. Our results support establishing a new species to accommodate JS1(T, for which we propose the name Gloeobacter kilaueensis sp. nov. Strain JS1(T has been deposited in the American Type Culture Collection (BAA-2537, the Scottish Marine Institute's Culture Collection of Algae and Protozoa (CCAP 1431/1, and the Belgian Coordinated Collections of Microorganisms (ULC0316. The G. kilaueensis holotype has been deposited in the Algal Collection of the US National Herbarium (US# 217948. The JS1(T genome sequence has been deposited in GenBank under accession number CP003587. The G+C content of the genome is 60.54 mol%. The complete genome sequence of G. kilaueensis JS1(T may further understanding of cyanobacteria evolution, and the shift from anoxygenic to oxygenic photosynthesis.

  8. Hydrothermal fluid venting in the offshore sector of Campi Flegrei caldera: A geochemical, geophysical, and volcanological study

    Science.gov (United States)

    Di Napoli, R.; Aiuppa, A.; Sulli, A.; Caliro, S.; Chiodini, G.; Acocella, V.; Ciraolo, G.; Di Vito, M. A.; Interbartolo, F.; Nasello, C.; Valenza, M.

    2016-10-01

    The ongoing unrest at the Campi Flegrei caldera (CFc) in southern Italy is prompting exploration of its poorly studied offshore sector. We report on a multidisciplinary investigation of the Secca delle Fumose (SdF), a submarine relief known since antiquity as the largest degassing structure of the offshore sector of CFc. We combined high-resolution morphobathymetric and seismostratigraphic data with onshore geological information to propose that the present-day SdF morphology and structure developed during the initial stages of the last CFc eruption at Monte Nuovo in AD 1538. We suggest that the SdF relief stands on the eastern uplifted border of a N-S-trending graben-like structure formed during the shallow emplacement of the Monte Nuovo feeding dike. We also infer that the high-angle bordering faults that generated the SdF relief now preferentially allow the ascent of hot brines (with an equilibrium temperature of 179°C), thereby sustaining hydrothermal degassing on the seafloor. Systematic vertical seawater profiling shows that hydrothermal seafloor venting generates a sizeable CO2, pH, and temperature anomaly in the overlying seawater column. Data for the seawater vertical profile can be used to estimate the CO2 and energy (heat) outputs from the SdF area at ˜50 tons/d (˜0.53 kg/s) and ˜80 MW, respectively. In view of the cause-effect relationship with the Monte Nuovo eruption, and the substantial gas and energy outputs, we consider that the SdF hydrothermal system needs to be included in monitoring programs of the ongoing CFc unrest.

  9. The link between volcanism and plutonism in epizonal magma systems; high-precision U–Pb zircon geochronology from the Organ Mountains caldera and batholith, New Mexico

    Science.gov (United States)

    Rioux, Matthew; Farmer, Lang; Bowring, Samuel; Wooton, Kathleen M.; Amato, Jeffrey M.; Coleman, Drew S.; Verplanck, Philip L.

    2016-01-01

    The Organ Mountains caldera and batholith expose the volcanic and epizonal plutonic record of an Eocene caldera complex. The caldera and batholith are well exposed, and extensive previous mapping and geochemical analyses have suggested a clear link between the volcanic and plutonic sections, making this an ideal location to study magmatic processes associated with caldera volcanism. Here we present high-precision thermal ionization mass spectrometry U–Pb zircon dates from throughout the caldera and batholith, and use these dates to test and improve existing petrogenetic models. The new dates indicate that Eocene volcanic and plutonic rocks in the Organ Mountains formed from ~44 to 34 Ma. The three largest caldera-related tuff units yielded weighted mean 206Pb/238U dates of 36.441 ± 0.020 Ma (Cueva Tuff), 36.259 ± 0.016 Ma (Achenback Park tuff), and 36.215 ± 0.016 Ma (Squaw Mountain tuff). An alkali feldspar granite, which is chemically similar to the erupted tuffs, yielded a synchronous weighted mean 206Pb/238U date of 36.259 ± 0.021 Ma. Weighted mean 206Pb/238U dates from the larger volume syenitic phase of the underlying Organ Needle pluton range from 36.130 ± 0.031 to 36.071 ± 0.012 Ma, and the youngest sample is 144 ± 20 to 188 ± 20 ka younger than the Squaw Mountain and Achenback Park tuffs, respectively. Younger plutonism in the batholith continued through at least 34.051 ± 0.029 Ma. We propose that the Achenback Park tuff, Squaw Mountain tuff, alkali feldspar granite and Organ Needle pluton formed from a single, long-lived magma chamber/mush zone. Early silicic magmas generated by partial melting of the lower crust rose to form an epizonal magma chamber. Underplating of the resulting mush zone led to partial melting and generation of a high-silica alkali feldspar granite cap, which erupted to form the tuffs. The deeper parts of the chamber underwent continued recharge and crystallization for 144 ± 20 ka after the

  10. CÓMO MEJORAR LA EFICIENCIA OPERATIVA UTILIZANDO EL TRABAJO EN EQUIPO

    Directory of Open Access Journals (Sweden)

    Carlos Alberto Franco

    2000-01-01

    Full Text Available En este artículo se presenta un modelo para aumentar la eficiencia operativa de diversas organizaciones de la economía con el fin de mejorar sus resultados financieros y por consiguiente su competitividad. Este modelo permite aprovechar los talentos de las personas que laboran en la empresa, organizándolos en equipos o grupos para que puedan identificar y aprovechar oportunidades de mejoramiento que conduzcan a un aumento significativo de la eficiencia productiva. La metodología que aquí se expone es particularmente útil para las empresas medianas y pequeñas que regularmente no cuentan con recursos ni infraestructura suficiente para introducir los cambios que CÓMO MEJORAR LA EFICIENCIA OPERATIVA UTILIZANDO EL TRABAJO EN EQUIPO CARLOS ALBERTO FRANCO Director MBA de la Universidad Icesi en convenio con la Universidad de Tulane. Ingeniero Eléctrico de la Universidad del Valle. Máster en Ingeniería de Carnegie Mellon University, Pisttsburg. Ph.D. en Ingeniería Eléctrica de USC (U.S.A. FRANCISCO VELÁSQUEZ V. Director del Programa de Administración de Empresas Plan Diurno. Ingeniero Electricista de la Universidad del Valle. Magister en Administración del Instituto de Estudios Superiores de Monterrey, Campus ciudad de México. mejoren su productividad. El modelo se puede aplicar directamente por los jefes o supervisores de cada una de las áreas de la empresa, sin necesidad de recurrir a asesorías costosas.

  11. Evaluación de ataques UDP Flood utilizando escenarios virtuales como plataforma experimental

    Directory of Open Access Journals (Sweden)

    Deyci Toscano

    2011-07-01

    Full Text Available Los ataques por denegación de servicio (DoS tienen como propósito imposibilitar el acceso a los servicios de una organización durante un periodo indefinido; por lo general, están dirigidos a los servidores de una empresa, para que no puedan ser accedidos por usuarios autorizados. El presente trabajo se enfoca en la evaluación de ataques DoS tipo UDP Flood, utilizando como plataforma de experimentación un entorno virtual de red que permite identificar cómo actúan dichos ataques en la saturación del ancho de banda; para llevarlo a cabo se diseñó e implementó una red híbrida con segmentación WAN, LAN y DMZ que inhabilita el acceso interno y externo a un servicio Web expuesto. Las herramientas evaluadas fueron UPD Unicorn, Longcat Flooder y UDPl.pl Script de Perl; las dos primeras instaladas sobre Windows, y la última, sobre Linux. Para validar está investigación se desarrolló un mecanismo de detección y mitigación de los ataques a nivel del firewall e IDS/IPS, evitando de este modo la saturación de la red. Finalmente, se evaluó el consumo dememoria, CPUy ancho de banda durante el ataque, la detección y la evasión, con el fin de determinar cuál genera mayor impacto. Los resultados demuestran que el mecanismo detecta, controla y mitiga los ataques.

  12. Evaluación de ataques UDP Flood utilizando escenarios virtuales como plataforma experimental

    Directory of Open Access Journals (Sweden)

    Walter Fuertes

    2012-05-01

    Full Text Available Los ataques por denegación de servicio (DoS tienen como propósito imposibilitar el acceso a los servicios de una organización durante un periodo indefinido; por lo general, están dirigidos a los servidores de una empresa, para que no puedan ser accedidos por usuarios autorizados. El presente trabajo se enfoca en la evaluación de ataques DoS tipo UDP Flood, utilizando como plataforma de experimentación un entorno virtual de red que permite identificar cómo actúan dichos ataques en la saturación del ancho de banda; para llevarlo a cabo se diseñó e implementó una red híbrida con segmentación WAN, LAN y DMZ que inhabilita el acceso interno y externo a un servicio Web expuesto. Las herramientas evaluadas fueron UPD Unicorn, Longcat Flooder y UDPl.pl Script de Perl; las dos primeras instaladas sobre Windows, y la última, sobre Linux. Para validar está investigación se desarrolló un mecanismo de detección y mitigación de los ataques a nivel del firewall e IDS/IPS, evitando de este modo la saturación de la red. Finalmente, se evaluó el consumo dememoria, CPUy ancho de banda durante el ataque, la detección y la evasión, con el fin de determinar cuál genera mayor impacto. Los resultados demuestran que el mecanismo detecta, controla y mitiga los ataques. 

  13. Productividad en una celda de manufactura flexible simulada en promodel utilizando path networks type crane

    Directory of Open Access Journals (Sweden)

    María Elena Bernal Loaiza

    2015-04-01

    Full Text Available Esta investigación se centra en el diseño de una simulación del proceso de una celda de manufactura flexible (FMC de la Facultad de Ingeniería Industrial de la Universidad Tecnológica de Pereira, con el propósito de medir y elegir aquella alternativa de solución que mejore en mayor grado la productividad del sistema actual utilizando los resultados que proporciona el software Promodel. Para realizar lo anterior se utilizaron etapas de la simulación como definición del sistema, formulación del modelo, identificación de variables, recolección de datos, implementación e interpretación.Como resultado, se calculó la productividad teniendo en cuenta las variables del modelo y tiempo de la simulación, al mismo tiempo se interpretó la información de cada una de las locaciones, hallando el porcentaje de utilización y total de entidades para las locaciones con capacidad unitaria; para las locaciones con mayor capacidad se encuentra información referente al porcentaje de tiempo vacío, parcialmente ocupado, lleno y no disponible respecto del tiempo disponible. A diferencia de otras simulaciones, en este diseño en la parte de redes se utilizó el tipo de red Crane, asociado a los recursos del modelo. El cual facilita el desplazamiento de los brazos robots con las piezas que circulan a través del sistema.

  14. Caracterización de depósitos de suelo utilizando geo-radar

    Directory of Open Access Journals (Sweden)

    Moreno V. Francisco Javier

    2003-08-01

    Full Text Available

    The radar technique prospects the subsoil with electromagnetic waves with frequencies between 10 and 1200 Mhz. A reflection radar image shows contrasts of the subsoil generated by its inhomogeneous electromagnetic properties. The velocity of the dielectric constant, correlated with mineral fabric, structure and water contained in rocks. Meanwhile lab assays, correlations between this properties for sand, cloy and a mixture of the, were stablished.

    La técnica del geo-radar, o G.P.R. por su sigla en inglés (Ground Penetrating Radar, es una forma de prospección del subsuelo utilizando ondas  electromagnéticas con frecuencias entre 10 y 1200 Mhz. Una imagen de geo-radar obtenida por reflexión contiene contrastes generados por la variación espacial de las propiedades electromagnéticas. La velocidad de las ondas electromagnéticas en un suelo depende fundamentalmente de la constante dieléctrica equivalente, la cual se puede correlacionar con la fábrica, la estructura y el contenido de agua. Por medio de pruebas en laboratorio se establecieron correlaciones para arena, recebo y arcilla.

  15. Cardiomioplastia celular utilizando el factor estimulante del crecimiento de colonias de granulocitos

    Directory of Open Access Journals (Sweden)

    Fabián Alberto Jaimes Barragán

    2008-11-01

    Full Text Available INTRODUCCIÓN: el presente estudio tuvo como objetivo evaluar la eficacia y seguridad de la cardiomioplastia celular utilizando el factor estimulante de colonias de granulocitos en pacientes con cardiopatía isquémica. MÉTODOS: se llevó a cabo un estudio de “antes y despúes” para datos longitudinales comparando variables ecocardiográficas, número de Mets alcanzados en la prueba de esfuerzo antes, 2, 6 y 12 meses después del procedimiento, también se evaluaron la mortalidad y los efectos adversos de la terapia. RESULTADOS: la mediana de la fracción de eyección antes de implantar las células fue de 30% con un rango intercuartil de 28-35%; la media de los Mets fue de 6 con un rango intercuartil de 5-7; ambas variables, al igual que los volúmenes ventriculares en fin de diástole y sístole se incrementaron de forma significativa después del procedimiento. Un paciente presentó infección de la herida quirúrgica y tres murieron dos meses después de la implantación (uno por choque séptico y dos por choque cardiogénico. CONCLUSIÓN: en Medellín, Colombia, es factible hacer la cardiomioplastia celular; se trata de un procedimiento seguro que logra una mejoría sostenida de la fracción de eyección y los Mets más allá de los beneficios obtenidos con la revascularización y la terapia farmacológica óptima.

  16. Acceso remoto seguro a cuentas de usuario utilizando plataformas de virtualización

    Directory of Open Access Journals (Sweden)

    Walter Fuertes, Maritza Enríquez y Diego Veloz

    2011-05-01

    Full Text Available En  las  universidades  persiste  el  problema  de  la subutilización de recursos tecnológicos; sin embargo, sesigue  incurriendo en gastos por adquisición de servidores,hardware  y  software. Frente  a  este  escenario,  en  laindustria se han venido desarrollando las tecnologías devirtualización, que ahorran energía y costos de inversiónde hardware. En  consecuencia,  el  artículo propone  elacceso remoto seguro a cuentas de usuario en un servidoruniversitario  virtualizado;  para  llevarlo  a  cabo  sediseñaron  e  implementaron  varias  topologías  deexperimentación, utilizando Virtual Box 3.1.3 y VMwareServer 2.0.2,  y  se  evaluaron diversas  tecnologías  deconexiones remotas seguras, bajo  idénticas condicionesy parámetros de  comprobación. En  cada  topología  seevaluó el rendimiento del servidor, el performance y  laseguridad  de  la  red  en  producción. Los  resultadosmuestran  la  funcionalidad  de  este  proyecto  deinvestigación  que  facilita  el  acceso  remoto  seguro deusuarios a los recursos informáticos universitarios.

  17. EVALUACIÓN DE LA BIOESTIMULACION (NUTRIENTES EN SUELOS CONTAMINADOS CON HIDROCARBUROS UTILIZANDO RESPIROMETRIA

    Directory of Open Access Journals (Sweden)

    Roldán Fabio

    2011-04-01

    Full Text Available Se evaluó el proceso de bioestimulación por nutrientes: fertilizantes inorgánicos compuestos (FIC N:P:K 28:12:7 y sales inorgánicas simples (SIS NH4NO3 y K2HPO4 en suelos contaminados con hidrocarburos utilizando respirometría. El suelo fue contaminado con lodos aceitosos a una concentración ~40,000 mgTPH/kgps. Para cuantificar el consumo de oxigeno se utilizaron dos respirómetros de medición manométrica HACH® 2173b y OXITOP® PF600 durante ensayos de trece días. Se evaluaron dos tratamientos (FIC y SIS y tres controles (abiótico, sustrato de referencia y sin nutrientes. Se analizaron parámetros físico-químicos (pH, nutrientes y TPH y microbiológicos (heterótrofos y degradadores al inicio y al final de cada ensayo. SIS y el control sin nutrientes presentaron las mayores tasas de respiración, en el equipo HACH se obtuvieron valores de: 802.28 y 850.72 mgO2kgps-1d-1 respectivamente mientras que en el OXITOP fueron de 936.65 y 502.05 mgO2kgps-1d-1, respectivamente. En ninguno de los equipos se observo un aumento significativo de los degradadores, indicando que la bioestimulación no tuvo un efecto sobre la densidad microbiana. Por otro lado FIC, presentó los recuentos y tasas de respiración más bajas (188.18 y 139.87 mgO2kgps-1d-1 en HACH y OXITOP, respectivamente, esto pudo estar correlacionado a un efecto toxico generado por la acumulación de amoniaco.

  18. Shallow sub-surface structure of the central volcanic complex of Tenerife, Canary Islands: implications for the evolution and the recent reactivation of the Las Canadas caldera

    Energy Technology Data Exchange (ETDEWEB)

    Gottsmann, J [Department of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol BS8 1RJ (United Kingdom); Camacho, A G; Fernandez, J [Instituto de Astronomia y Geodesia (CSIC-UCM), Ciudad Universitaria, Pza. de Ciencias, 3, 28040 Madrid (Spain); MartI, J [Institute of Earth Sciences ' Jaume Almera' , CSIC, Lluis Sole SabarIs s/n, Barcelona 08028 (Spain); Wooller, L; Rymer, H [Department of Earth and Environmental Sciences, Open University, Walton Hall, Milton Keynes, MK7 6AA (United Kingdom); GarcIa, A [Department of Volcanology, Museo Nacional de Ciencias Naturales, CSIC, C/ Jose Gutierrez Abascal, 2, 28006 Madrid (Spain)], E-mail: j.gottsmann@bristol.ac.uk

    2008-10-01

    We present a new local Bouguer anomaly map of the Central Volcanic Complex (CVC) of Tenerife, Spain. The high-density core of the CVC and the pronounced gravity low centred in the Las Canadas caldera (LCC) in greater detail than previously available. Mathematical construction of a subsurface model from the local anomaly data, employing a 3-D inversion enables mapping of the shallow structure beneath the complex, giving unprecedented insights into the sub-surface architecture of the complex, and shedding light on its evolution.

  19. Rendimiento térmico de calderas bagaceras modernas en Tucumán, R. Argentina Thermal efficiency of modern bagasse boilers in Tucumán, Argentina

    Directory of Open Access Journals (Sweden)

    Federico J. Franck Colombres

    2011-12-01

    Full Text Available Se evaluaron tres calderas de vapor modernas instaladas en ingenios azucareros de Tucumán, R. Argentina, equipos que se encuadran dentro de las tecnologías de producción más limpia. Tomando como base la metodología de cálculo de la eficiencia térmica de generadores de vapor desarrollada en 2008 por la Sección Ingeniería y Proyectos Agroindustriales de la Estación Experimental Agroindustrial Obispo Colombres, y a partir de los datos recolectados por medio de mediciones y balances de materia y energía, se determinaron sus principales variables características de operación. Las eficiencias energéticas determinadas para cada una fueron del 73,5%; 75,2% y 77,3%. Se realizó además una comparación con las calderas de vapor convencionales y se determinó el ahorro de bagazo que puede obtenerse con las calderas modernas, el cual resultó ser de un 27,6%. Como una ventaja adicional, se hace mención a la posibilidad de mejora del rendimiento térmico del ciclo motriz de la planta, que viene acompañada con el aumento de la presión de trabajo de la caldera.Three modern steam boilers, installed in sugar mills in Tucumán, R. Argentina, to attain a cleaner production, were evaluated. Their major operating variables were determined using the methodology for calculating thermal efficiency of steam generators developed by Sección Ingeniería y Proyectos Agroindustriales of Estación Experimental Agroindustrial Obispo Colombres in 2008, and data obtained from measurements and material and energy balances. Energy efficiency values determined for each boiler were 73.5%, 75.2% and 77.3%, respectively. A comparison with conventional steam boilers was drawn and it was found that bagasse savings amounted to about 27.6% when modern boilers were used. The possibility of improving the thermal efficiency of the plant cycle by increasing boiler pressure is mentioned as an additional advantage.

  20. Investigaciones dendrogeomorfológicas aplicadas al estudio de la peligrosidad por avenidas e inundaciones en el parque nacional de la Caldera de Taburiente (La Palma, Islas Canarias).

    OpenAIRE

    Díez Herrero, Andrés; Genova Fuster, Maria del Mar; Mayer Suárez, Pablo Lucas; Ballesteros Cánovas, Juan Antonio; Becerril Carretero, Laura; Rubiales Jimenez, Juan Manuel; Hernández Ruiz, M.; Saz Sánchez, M. A.; Bodoque del Pozo, Jose Maria; Ruiz Villanueva, V.

    2012-01-01

    La red de drenaje del parque nacional de la Caldera de Taburiente (La Palma, Islas Canarias) está constituida por numerosos torrentes tributarios del barranco de Las Angustias, que presentan frecuentes e intensos eventos de avenidas súbitas. Estas riadas han producido incluso víctimas mortales entre practicantes de senderismo (3 fallecidos en noviembre de 2001) e importantes pérdidas económicas al interferir con los proyectos de repoblación de las riberas con especies autóctonas (superio...

  1. Caldera La Peligrosa (47º15´S, 71°40´O: un evento clave en la Provincia Silícea Chon Aike

    Directory of Open Access Journals (Sweden)

    Patricia Sruoga

    2010-05-01

    Full Text Available En el área ubicada entre el lago Ghío y la sierra Colorada, en la Cordillera Patagónica Austral, aflora una secuencia piroclástico- lávica de carácter proximal correspondiente al Complejo El Quemado, de edad jurásica tardía. A partir del análisis integrado de litofacies y estructuras se llevó a cabo la reconstrucción de la arquitectura volcánica. Se han reconocido cuatro litofacies ignimbríticas y una litofacies lávico-hipabisal de composición riolítica, cuyo emplazamiento estuvo controlado por un sistema de fallas transtensionales de orientación NNO predominante. Se propone un modelo de evolución de la caldera La Peligrosa en tres etapas:1 pre-colapso, durante la cual se define una zona dilatante propicia para la formación de la caldera, con incipiente fallamiento en bloques, 2 colapso, cuando ocurre el emplazamiento de potentes ignimbritas cristalinas y megabrechas en una cubeta de subsidencia progresiva, controlada por un régimen transtensional con dirección de extensión NE y 3 post-colapso, durante la cual se produce el derrame de lavas junto con la intrusión de cuerpos dómicos, bajo condiciones de extensión oblicua con dirección de extensión NO. El pasaje de un ambiente transtensional a condiciones de extensión oblicua acompañó las últimas etapas del desarrollo de la caldera representando un notable cambio en las condiciones de la deformación en tiempos jurásicos. La formación y desarrollo de la caldera La Peligrosa puede ser considerada como un evento clave para entender los mecanismos eruptivos del vasto volcanismo ignimbrítico de la Provincia Silícea Chon Aike.

  2. An integrated multidisciplinary re-evaluation of the geothermal system at Valles Caldera, New Mexico, using an immersive three-dimensional (3D) visualization environment

    Science.gov (United States)

    Fowler, A.; Bennett, S. E.; Wildgoose, M.; Cantwell, C.; Elliott, A. J.

    2012-12-01

    We describe an approach to explore the spatial relationships of a geothermal resource by examining diverse geological, geophysical, and geochemical data sets using the immersive 3-dimensional (3D) visualization capabilities of the UC Davis Keck Center for Active Visualization in the Earth Sciences (KeckCAVES). The KeckCAVES is a facility where stereoscopic images are projected onto four, surfaces (three walls and a floor), which the user perceives as a seamless 3D image of the data. The user can manipulate and interact with the data, allowing a more intuitive interpretation of data set relationships than is possible with traditional 2-dimensional techniques. We incorporate multiple data sets of the geothermal system at Valles Caldera, New Mexico: topography, lithology, faults, temperature, alteration mineralogy, and magnetotellurics. With the ability to rapidly and intuitively observe data relationships, we are able to efficiently and rapidly draw conclusions about the subsurface architecture of the Valles Caldera geothermal system. We identify two high-temperature anomalies, one that corresponds with normal faults along the western caldera ring fracture, and one that with the resurgent dome. A cold-temperature anomaly identified adjacent to the resurgent dome high-temperature anomaly appears to relate to a fault controlled graben valley that acts as a recharge zone, likely funneling cold meteoric water into the subsurface along normal faults observed on published maps and cross sections. These high-temperature anomalies broadly correspond to subsurface regions where previous magnetotelluric studies have identified low apparent resistivity. Existing hot springs in the Sulfur Springs area correspond to the only location where our modeled 100°C isotherm intersects the ground surface. Correlation between the first occurrence of key alteration minerals (pyrite, chlorite, epidote) in previously drilled boreholes and our temperature model vary, with chlorite showing a

  3. Application of HydroGeoSphere to model the response to anthropogenic climate change of three-dimensional hydrological processes in the geologically, geothermally, and topographically complex Valles Caldera super volcano, New Mexico: Preliminary results

    Science.gov (United States)

    Wine, M.; Cadol, D. D.

    2014-12-01

    Anthropogenic climate change is expected to reduce streamflow in the southwestern USA due to reduction in precipitation and increases in evaporative demand. Understanding the effects of climate change in this region is particularly important for mountainous areas since these are primary sources of recharge in arid and semi-arid environments. Therefore we undertook to model effects of climate change on the hydrological processes in Valles Caldera (448 km2), located in the Jemez Mountains of northern New Mexico. In Valles Caldera modeling the surficial, hydrogeological, and geothermal processes that influence hydrologic fluxes each present challenges. The surficial dynamics of evaporative demand and snowmelt both serve to control recharge dynamics, but are complicated by the complex topography and spatiotemporal vegetation dynamics. Complex factors affecting evaporative demand include leaf area index, temperature, albedo, and radiation affected by topographic shading; all of these factors vary in space and time. Snowmelt processes interact with evaporative demand and geology to serve as an important control on streamflow generation, but modeling the effects of spatiotemporal snow distributions on streamflow generation remains a challenge. The complexity of Valles Caldera's geology—and its associated hydraulic properties—rivals that of its surficial hydrologic forcings. Hydrologically important geologic features that have formed in the Valles Caldera are three-dimensionally intricate and include a dense system of faults, alluvium, landslides, lake deposits, and features associated with the eruption and collapse of this super volcano. Coupling geothermally-driven convection to the hydrologic cycle in this still-active geothermal system presents yet an additional challenge in modeling Valles Caldera. Preliminary results from applying the three-dimensional distributed hydrologic finite element model HydroGeoSphere to a sub-catchment of Valles Caldera will be

  4. Estudio de eliminación de arsénico con resinas de intercambio iónico en agua potable de Zimapán, Estado de Hidalgo, México

    Directory of Open Access Journals (Sweden)

    Pérez-Moreno, F.

    2006-10-01

    Full Text Available Anionic exchange resins were research with respect its capacity for removal arsenic content in water. Water of well V from Zimapán Hidalgo Mexico was used to make this research, because this water have a mean concentration of 480 ± 11 μg·L-1 of arsenic and it is
    available as drinking water. The exchange resins employed were two strong anionic, one macroreticular (IRA-900 and other gel type (IRA-400, as soon as one third anionic weak macroreticular type (IRA-96. The experiments carried with this resins showing that IRA-900 has highest efficient in the process of arsenic removal from drinking water, because, it showed a treatment capacity of 700 Vagua·Vres-1; while that capacities of IRA-400 e IRA-96 resins were 320 and 52 Vagua·Vres-1 respectively. The mean concentration of arsenic residue in the treatise water was 24 μg·l-1 and it is within the maximum level permissible by Mexican official norm for drinking water.

    Se investigaron resinas de intercambio aniónico con respecto a su capacidad para la eliminación de arsénico contenido en agua. Se utilizó agua del pozo V de Zimapán, Hidalgo, México, cuya concentración promedio es de 480 ± 11 μg·l-1 de arsénico y es utilizada para consumo humano. Se emplearon dos reinas aniónicas fuertes; una, de tipo macro reticular (IRA-900 y la otra de tipo gel (IRA-400, así como una tercera, aniónica débil, de tipo macro reticular (IRA-96. Los experimentos realizados con estas resinas muestran que la IRA-900 es la que mostró la más alta eficiencia en la eliminación de arsénico del agua potable, debido a que presentó una capacidad de tratamiento de 700 Vagua·Vres-1, mientras que las capacidades de las resinas IRA-400 e IRA-96 fueron de 320 y 52 Vagua·Vres-1, respectivamente. La concentración promedio de ars

  5. Validation of a smooth configuration surface for compact heat exchangers using a numerical method//Validación de la superficie de un intercambiador de calor compacto en configuración lisa utilizando un método numérico

    Directory of Open Access Journals (Sweden)

    José‐L. Leiro‐Garrido

    2014-08-01

    Full Text Available This work determines the thermo hydraulics behavior of smooth configuration surface for a compact heat exchanger by means of numerical simulation. The objective is to use the results as baseline for research in the enhancement of heat transfer and drag reduction, directed to reduce the energy consumption and diminish the environmental impact. The fin tube heat exchanger models described.The constraints used in the implementation of the equation solver are announced. The average heat transfer coefficient and pressure drop obtained from numerical simulation are compare to experimental results presented in literature for models with the same dimensions and configuration. A good agreement between numerical and experimental results is reached. Local mechanisms responsible for the heat transfer and pressure drop are detailed. The study is conducted inside thelaminar regime for frontal velocities ranging between 0.5 and 6 m/s.Key words: compact heat exchanger, heat transfer coefficient, numerical simulation, pressure drop.______________________________________________________________________________ResumenEste trabajo determina el comportamiento termo hidráulico de una superficie perteneciente a un intercambiador de calor compacto en configuración lisa utilizando un método de simulación numérica. El objetivo es caracterizar la superficie para poder utilizarla como una referencia en las comparaciones con superficies de intercambio de calor intensificadas. Los datos obtenidos seutilizaran en la determinación de los valores relativos de intensificación de la transferencia de calor y el arrastre intentando reducir el consumo energético y su impacto ambiental. Se describe el modelo de intercambiador de calor con tubos aletados. Los resultados numéricos obtenidos presentan unbuen ajuste con los valores experimentales. Los resultados del coeficiente de transferencia de calor global y la caída de presión son explicados a partir de las

  6. 40Ar/39Ar dating of tuff vents in the Campi Flegrei caldera (southern Italy): Toward a new chronostratigraphic reconstruction of the Holocene volcanic activity

    Science.gov (United States)

    Fedele, L.; Insinga, D.D.; Calvert, A.T.; Morra, V.; Perrotta, A.; Scarpati, C.

    2011-01-01

    The Campi Flegrei hosts numerous monogenetic vents inferred to be younger than the 15 ka Neapolitan Yellow Tuff. Sanidine crystals from the three young Campi Flegrei vents of Fondi di Baia, Bacoli and Nisida were dated using 40Ar/39Ar geochronology. These vents, together with several other young edifices, occur roughly along the inner border of the Campi Flegrei caldera, suggesting that the volcanic conduits are controlled by caldera-bounding faults. Plateau ages of ∼9.6 ka (Fondi di Baia), ∼8.6 ka (Bacoli) and ∼3.9 ka (Nisida) indicate eruptive activity during intervals previously interpreted as quiescent. A critical revision, involving calendar age correction of literature 14C data and available 40Ar/39Ar age data, is presented. A new reference chronostratigraphic framework for Holocene Phlegrean activity, which significantly differs from the previously adopted ones, is proposed. This has important implications for understanding the Campi Flegrei eruptive history and, ultimately, for the evaluation of related volcanic risk and hazard, for which the inferred history of its recent activity is generally taken into account.

  7. El capitán Miguel Caldera y la frontera chichimeca: entre el mestizo historiográfico y el soldado del rey

    Directory of Open Access Journals (Sweden)

    Ruiz Guadalajara, Juan Carlos

    2010-04-01

    Full Text Available This article attempts to examine critically the image that contemporary historiography has built around the figure of Captain Miguel Caldera. In contrast, it shows aspects that bring us closer to his Hispanic identity, to his role as a member of the militia in the service of Philip II of Spain and to the part he played as an instrument of domination and in the disappearance of the nomads of the Chichimecan frontier. It also contributes to the discussion of frontier cultural development in the context of the Hispanic monarchy’s expansion in the 16th century.

    Este artículo intenta un acercamiento crítico a la imagen que la historiografía contemporánea ha construido en torno a la figura del capitán Miguel Caldera. Muestra, en contraste, elementos que nos aproximan a su identidad hispánica, a su papel como miliciano al servicio de Felipe II y a su función como vehículo de la dominación y desaparición de los nómadas de la frontera chichimeca. También pretende aportar elementos de discusión sobre el proceso cultural fronterizo en el ámbito de la expansión de la monarquía hispánica en el siglo XVI.

  8. Cosecha de café con aire utilizando aspiración.

    Directory of Open Access Journals (Sweden)

    Campillo O. Pablo Ignacio

    2000-12-01

    Full Text Available Las ventosas son utilizadas para sujetar y para transportar productos industriales, avícolas y agrícolas. Por su diseño, por los materiales utilizados en su fabricación y por la amplia gama de tamaños, las ventosas se adaptan a diferentes formas y rugosidades superficiales. Estos dispositivos pueden ser empleados para desprender frutos maduros en cosechadores operados por el hombre o en equipos robotizados. En este estudio se evaluaron cuatro tipos de ventosas en la sujeción y el desprendimiento de frutos maduros de café (Coffea arabica var. Colombia: de Fuelle 1, Fuelle 2, Multifuelle y Profunda. Se midieron las siguientes variables: área de contacto de la ventosa, proporción de agarre (proporción de frutos agarrados en una rama, proporción de desprendimiento (proporción de frutos maduros desprendidos en una rama, fuerza media de desprendimiento (N y presión media de vacío (kPa. Los resultados obtenidos, indicaron que la proporción de agarre fue del 100 % y la proporción de desprendimiento fue superior al 86 % para todas las ventosas estudiadas. La presión media de vacío varió entre valores de –57 kPa y –45 kPa para todas las ventosas. La fuerza media de desprendimiento varió para cada ángulo y cada ventosa, encontrándose valores entre 3,0 y 10 N. El desprendimiento del fruto de café, utilizando un sistema neumático de vacío con ventosas, depende del tipo de ventosa utilizada, siendo independiente del ángulo en el que actúa. La ventosa más adecuada, según los resultados obtenidos, para agarrar y desprender frutos maduros de café, fue la de tipo Multifuelle.

  9. Seguimiento de la reactogenicidad de la vacuna DTP cubana, utilizando dos métodos paralelos

    Directory of Open Access Journals (Sweden)

    María de los Ángeles Peña Machado

    2005-05-01

    Full Text Available Con el objetivo de caracterizar la reactogenicidad de la vacuna Antidiftérica-Antitetánica- Antipertusis (DTP cubana, desarrollada por el Instituto Finlay, se realizó un estudio utilizando dos métodos o fuentes de información diferentes y paralelos. La primera se obtuvo de un ensayo clínico (EC Fase IV, abierto, no controlado, en el que se incluyeron 57 lactantes. La segunda fuente de información se obtuvo de los reportes de los eventos temporalmente asociados a la vacunación (ETAV, recepcionados por la Unidad Coordinadora Nacional de Farmacovigilancia (UCNFv que incluyen a 86 lactantes que fueron atendidos por sospechas de ETAV. En el EC se aplicaron 167 dosis, los eventos adversos esperados e inesperados se observaron en un escaso número de lactantes, fueron mayoritariamente ligeros y autolimitados en el tiempo y su frecuencia de aparición se redujo en la 2da y 3ra dosis. El dolor fue el evento local más frecuente y la fiebre fue el evento general que más se presentó. No se reportaron vómitos y la anorexia, la somnolencia, y el llanto persistente aparecieron en un número limitado de sujetos vacunados.Se presentaron 12 eventos no esperados, solo en 2 de ellos se consideró que existía relación causal con la vacunación. Se reportó un evento adverso grave (niña hospitalizada por síndrome febril prolongado postvacunación, que se estudió y demostró que fue causado por una sepsis urinaria persistente provocada por una malformación vesico-ureteral. Los 86 reportes recepcionados por la UCNFv incluían un total de 141 ETAV, dentro de los síntomas locales, el eritema alcanzó un 9,30% y la induración un 5,81%, la fiebre fue un síntoma frecuente aunque no se especifica la temperatura corporal alcanzada. Aunque existen varias diferencias con relación a las condiciones en que se realiza la vigilancia de eventos adversos en un EC o en la práctica clínica habitual, los resultados aquí analizados nos confirman que la

  10. Geophysical imaging of the lacustrine sediments deposited in the La Calderilla Volcanic Caldera (Gran Canaria Island, Spain) for paleoclimate research

    Science.gov (United States)

    Himi, Mahjoub; Rodríguez-González, Alejandro; Criado, Constantino; Tapias, Josefina C.; Ravazzi, Cesare; Pérez-Torrado, Francisco; Casas, Albert

    2016-04-01

    The discovery of well-preserved maar structures is important not only for studying the eruptive activity and formation of volcanoes, but also for paleoclimate research, since laminated maar lake sediments may contain very detailed archives of climate and environmental history. Maars are a singular type of volcanic structure generated by explosive phreatomagmatic eruptions as a result of interaction between rising magma and groundwater. This kind of structures are characterised by circular craters, often filled with water and/or lacustrine sediments and surrounded by a ring of pyroclastic deposits.Recently a borehole was drilled at the bottom of La Calderilla volcanic complex which penetrated about 8.7 m in its sedimentary sequence and paleobotanical study has supplied the first evidence of paleoenvironmental evolution during the Holocene on the Gran Canaria Island. This survey, however, did not penetrate into the substrate because the total thickness of the sedimentary fill was unknown. Since the age of formation of La Calderilla volcanic complex based on K/Ar dating is about 85,000 years (Upper Pleistocene), the possibility of its sedimentary fill extends beyond of the Holocene is extremely attractive, since, for example, there are few paleoenvironmental data regarding how much the last glaciation that affected the Canary Islands. In these circumstances, the knowledge of the total thickness of the lacustrine sediments is crucial to design a deeper borehole in the next future. Therefore, the subsurface characterisation provided by geophysics is essential for determining thickness and geometry of the sedimentary filling. Multielectrode ERT method was used to obtain five 2-D resistivity cross-sections into La Calderilla volcanic caldera. An Iris Syscal Pro resistivity system with 48 electrodes connected to a 94 m long cable (2m electrode spacing) in Wenner-Schlumberger configuration for an investigation depth of about 20 m. Data quality (q 8000 Ω.m) that can be

  11. Magma Chamber Model of Batur Caldera, Bali, Indonesia: Compositional Variation of Two Facies, Large-Volume Dacitic Ignimbrites

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    Igan S. Sutawidjaja

    2015-05-01

    Full Text Available DOI:10.17014/ijog.2.2.111-124Batur is one of the finest known calderas on Earth, and is the source of at least two major ignimbrite eruptions with a combined volume of some 84 km3 and 19 km3. These ignimbrites have a similar compositions, raising the question of whether they are geneticaly related. The Batur Ignimbrite-1 (BI-1 is crystal poor, containing rhyodacitic (68 - 70wt % SiO2, white to grey pumices and partly welded and unwelded. The overlying Batur Ignimbrite-2 (BI-2 is a homogeneous grey to black dacitic pumices (64 - 66 wt % SiO2, unwelded and densely welded (40 - 60% vesicularity, crystal and lithic rich. Phase equilibria indicate that the Batur magma equilibrated at temperatures of 1100 - 1300oC with melt water contents of 3 - 6 wt%. The post-eruptive Batur magma was cooler (<1100oC and it is melt more water rich (> 6 wt % H2O. A pressure of 20 kbar is infered from mineral barometry for the Batur magma chamber. Magmatic chamber model is one in which crystals and melt separate from a convecting Batur magma by density differences, resulting in a stratified magma chamber with a homogeneous central zone, a crystal-rich accumulation zone near the walls or base, and a buoyant, melt-rich zone near the top. This is consistent with the estimated magma temperatures and densities: the pre-eruptive BI-1 magma was hoter (1300oC and more volatile rich (6 wt % H2O with density 2.25 g/cm3 than the BI-2 magma (1200oC; 4 wt % H2O in density was higher (2.50 g/cm3. Batur melt characteristics and intensive parameters are consistent with a volatile oversaturation-driven eruption. However, the higher H2O content, high viscosity and low crystal content of the BI-1 magma imply an external eruption trigger.

  12. Variability of the planktonic foraminifera community across the Eocene/Oligocene boundary, Fuente Caldera Section, Baetic Ranges (Spain)

    Science.gov (United States)

    Legarda-Lisarri, A.

    2013-12-01

    During the Eocene/Oligocene transition, in a massive extinction event that took place about 33.7 million years ago, the current high resolution study analyzes qualitatively and quantitatively the community structure of the planktonic foraminifera that were preserved in the hemipelagic sediments of the Tethys Sea. The sampled section of the Fuente Caldera column, located in the Baetic mountain ranges, spans a register of 396,551.7 years. Based in the identification of 27 species, that belong to 13 genera and 2 families of foraminifera, there have been found three biozones of Gonzalvo Zonation (Gonzalvo, 2002) in the studied stratigraphic interval: Turborotalia cocoaensis and Cribrohantkenina lazzarii Biozones (Rupelian), and Paragloborotalia increbescens (Priabonian). The planktonic foraminifera associations variability patterns are defined by paleoecologic indexes (diversity index, high and low latitude species index and planktonic and benthic foraminifera index), by geochemical proxies: δ18O and δ13C and by 'Q' Mode Factor Analysis. They prove that the deposition environment is outer platform and also, they suggest that the studied area in the Tethys Sea underwent many thermal pulses, during which some species extinct or appear. In the first extinction event the species Turborotalia cocoaensis and Turborotalia cunialensis became extinct. In the second one, Hantkenina alabamensis, Hantkenina brevispina, Cribrohantkenina lazzarii and Pseudohastigerina micra became extinct while a succession occured; Globigerina officinalis, Globoturborotalita anguliofficinalis and Tenuitellinata angustiumbilicata appeared. The cooling event that finished in the Lower Oligocene was the biggest of these pulses, which was extremely abrupt and corresponds to the Oi-1 event that was described by Miller (Miller, 1991). All this evidences that the planktonic foraminifera extinction in the Upper Eocene was a gradual and fast event, what is supported by the Factor Analysis application. Key

  13. Probabilistic tsunami hazard assessment related to underwater explosions in the Campi Flegrei caldera: Gulfs of Napoli and Pozzuoli (Tyrrhenian Sea, Italy).

    Science.gov (United States)

    Ulvrova, Martina; Selva, Jacopo; Paris, Raphael; Brizuela, Beatriz; Costa, Antonio; Grezio, Anita; Lorito, Stefano; Tonini, Roberto

    2016-04-01

    Tsunami caused by underwater volcanic explosions are typically characterized by short period waves and greater dispersion compared to tsunami generated by earthquakes, and the impact in the far-field is often limited. However, the effect of dispersion is reduced for underwater explosions occurring in shallow-water environments, as the length-to-depth ratio of the waves rapidly increase, and runup inland can be locally high. This effect was particularly illustrated by the 19 m runup at Karymsky Lake, Kamchatka, in 1996 (Belousov et al., 2010; Ulvrova et al., 2014). Hazards related to underwater volcanic explosions are challenging to evaluate and might be underestimated in some cases. In this study we consider different scenarios of explosions in the offshore part of the Campi Flegrei (Phlegraean Fields) caldera in the Pozzuoli - Naples region (Tyrrhenian Sea, Italy). The onshore eruptive history of the caldera is well documented (e.g. Orsi et al., 2004), but past and future activity offshore has been rarely discussed. The probability for eruptions in the submarine part of the caldera is perhaps low (Selva et al., 2012), but scenarios of tsunamis generated by underwater explosions and their impact in the proximal field (Bay of Pozzuoli) and far field (Bay of Naples) deserve to be considered due to high population density in the adjacent coastal areas. Initial surface displacement is estimated as a function of explosion energy at a given depth. We study 17 different potential vent locations within the Pozzuoli Bay, and 3 different vent radii (200 m, 650 m and 900 m), corresponding to the three representative eruptive scenarios identified in Orsi et al. (2009) and Selva et al. (2010). We then use these sources in a Bayesian Event Tree framework, following the procedure defined in Selva et al. (2010), in order to evaluate a first order Probabilistic Hazard Analysis for this type of tsunami sources for the Gulfs of Napoli and Pozzuoli. Belousov A., Voight B., Belousova M

  14. Atributos AVO/AVA de alta resolución utilizando very fast simulated anneling

    Directory of Open Access Journals (Sweden)

    Daniel O Pérez

    2012-06-01

    Full Text Available En este trabajo presentamos un nuevo método de inversión para obtener atributos AVO/AVA de tipo sparse-spike a partir de datos sísmicos prestack. El método propuesto apunta a obtener el menor número de reflectores que, convolucionados con la ondícula, ajustan al dato. Este método es una extensión, aplicada a datos prestack, de un trabajo anterior sobre deconvolución sparse-spike aplicado a datos poststack. Debido a la alta no linealidad del problema inverso, que incluye la determinación en tiempo de un número dado de reflectores, se busca la solución usando el algoritmo de optimización global conocido como Very Fast Simulated Annealing (VFSA. Contrariamente a otros métodos que también buscan soluciones de tipo sparse, y donde el número de incógnitas coincide con el número de muestras del dato sísmico, en la estrategia propuesta el número de incógnitas es mucho menor. Como consecuencia, las matrices a invertir son pequeñas y el proceso de inversión resulta relativamente económico en términos de costo computacional, aún cuando la inversión se realiza utilizando simulated annealing. La técnica permite, además, determinar incógnitas adicionales como por ejemplo una rotación de fase de la ondícula (para su calibración a partir de la estimación inicial o su frecuencia central (para compensar efectos de atenuación. Una ventaja de utilizar VFSA es que la incertidumbre de las soluciones puede ser estimada estocásticamente, aprovechando el gran número de soluciones que se ponen a prueba durante el proceso de inversión. Los atributos AVO/AVA de alta resolución que se obtienen luego de la inversión incluyen el Intercept y el Gradient, o sea los coeficientes de la aproximación de Shuey de dos términos de las ecuaciones de Zoeppritz, las que son utilizadas para modelar la variación con el ángulo de incidencia del coeficiente de reflexión. No obstante, la incorporación de otras aproximaciones es inmediata. Los

  15. Controle de um pré-regulador com alto fator de potência utilizando microcontrolador PIC /

    OpenAIRE

    Grosse, Alexandre de Souza

    1999-01-01

    Dissertação (Mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Estudo de controle digital em eletrônica de potência utilizando um microcontrolador especial PIC17C756 em um pré-regulador para correção ativa do fator de potência. O enfoque principal é dado no controle da malha de corrente do conversor elevador utilizado. Parte-se da caracterização do microcontrolador e seus periféricos e prossegue-se através do projeto do conversor BOOST. São apresentadas as técnicas de...

  16. Estudo do rejuvenescimento de membranas de poliamida de osmose reserva utilizando ácido tânico

    OpenAIRE

    João Batista Azevedo da Silva

    2001-01-01

    Neste trabalho é apresentado um estudo sobre o rejuvenescimento de membranas de poliamida de osmose reversa utilizando ácido tânico como agente de rejuvenescimento. Em uma primeira etapa foram estudadas oxidações de membranas por cloro livre catalisadas por ferro e alumínio, e degradações promovidas por procedimentos de limpeza química. Posteriormente, testes de rejuvenescimento foram realizados para encontrar as melhores condições para a recuperação da eficiência das membranas. Parâmetros op...

  17. Predicción de ingresos de causas penales utilizando programación genética lineal

    OpenAIRE

    Garcete Rodríguez, Alberto David; Barán, Benjamín

    2015-01-01

    Este trabajo propone una metodología de predicción de ingresos de causas penales utilizando Programación Genética Lineal (Linear Genetic Programming - LGP). El estudio se realizó en base a datos mensuales recogidos durante siete años (2007 a 2013), en los siete Juzgados Penales de Garantías de Ciudad del Este - Paraguay. La verificación del método propuesto se hizo mediante la comparación del método LGP implementado con modelos estadísticos conocidos como la regresión lineal, promedio móvil, ...

  18. Degradação de poliolefinas utilizando catalisadores zeolíticos Degradation of polyolefins using zeolitic catalysts

    OpenAIRE

    Maria Letícia M. Valle; Maria José O. C. Guimarães; Cristiane M. S. Sampaio

    2004-01-01

    Neste trabalho foi estudada a degradação de alguns dos principais constituintes dos rejeitos plásticos (polietileno de alta densidade (HDPE), polietileno de baixa densidade (LDPE) e polipropileno (PP)), empregando-se um catalisador exausto de unidades de craqueamento de fluidos (FCC) e um catalisador zeolítico (ADZ3) sintetizado em laboratório. Utilizando técnicas de termogravimetria (TG-DTG) e cromatografia gasosa (CG), foi possível avaliar os produtos gerados no craqueamento destas poliolef...

  19. La geometría del método Simplex y sus aplicaciones utilizando Matlab®

    OpenAIRE

    Raffo Lecca, Eduardo; Universidad Nacional Mayor de San Marcos; Ruiz Lizama, Edgar; Universidad Nacional Mayor de San Marcos

    2014-01-01

    El artículo revisa los conceptos de la geometría computacional aplicados al método simplex utilizando MATLAB®. Dado un modelo de programación lineal o PL, una solución factible es un vector que especifica un valor para cada variable en el problema, el cual sustituyéndolo satisface todas las restricciones; incluidas las de signo. El trabajo revisa los conceptos de la geometría computacional, el método simplex y presenta la manera de aplicar la forma gráfica a un problema PL. Se incluye archivo...

  20. Infección urinaria en pacientes con cateterismo vesical con sistema de drenaje cerrado, utilizando un frasco colector recambiable.

    OpenAIRE

    Valdez, Rosario; Miyahira Arakaki, Juan

    2014-01-01

    Con el objetivo de determinar la incidencia de ITU asociado a cateterismo vesical con sistema de drenaje cerrado utilizando un frasco recambiable, fueron evaluados 20 pacientes no críticos, cateterizados por 5 días. Se encontró una incidencia de bacteriuria asociada a cateterismo vesical de 5%, mientras que la contaminación del frasco de drenaje se documento en el 10% de los pacientes. Tanto la bacteriuría, como la contaminación del frasco colector ocurrieron a las 96 horas de cateterismo ves...

  1. Procedimiento para la gestión de mantenimiento utilizando herramientas de la cuarta generación

    OpenAIRE

    Aracelis Barrios; Maritza Ortiz

    2013-01-01

    El presente artículo presenta el diseño de un procedimiento para una gestión de mantenimiento sistémico, utilizando un conjunto de herramientas, que enfocan el uso de los recursos de la empresa asociados con las Personas, los Procesos y la Tecnología, orientados a mejorar la productividad, la toma de decisiones acertadas y a maximizar el rendimiento de los equipos, considerando entre otros, los factores de Confiabilidad, Mantenibilidad, Seguridad, Calidad y Medio Ambiente. El desarrollo del p...

  2. La Peligrosa caldera (47° 15‧S, 71° 40‧W): A key event during the Jurassic ignimbrite flare-up in Southern Patagonia, Argentina

    Science.gov (United States)

    Sruoga, P.; Japas, M. S.; Salani, F. M.; Kleiman, L. E.

    2014-01-01

    Pyroclastic and lava vent-facies, from the Late Jurassic El Quemado Complex, are described at the southern Lake Ghío, in the Cordillera Patagónica Austral. Based on the comprehensive study of lithology and structures, the reconstruction of the volcanic architecture has been carried out. Four ignimbrites and one rhyolitic lava unit, affected by oblique-slip normal faults have been recognized. The evolution of La Peligrosa Caldera has been modeled in three different stages:1) initial collapse, consisting of a precursory downsag subsidence, related to a dilatational zone, which controlled the location of the caldera, 2) main collapse, with the emplacement of large volume crystal-rich ignimbrites and megabreccias, under a progressive subsidence controlled by a pull-apart structure related to a transtensional regime and 3) post-collapse, in which lava flows and associated domes were emplaced under an oblique-extensional regime. The caldera records a remarkable change from transtension to oblique extension, which may represent an important variation in regional deformation conditions during Jurassic times. La Peligrosa Caldera may be considered a key event to understand the eruptive mechanisms of the flare-up volcanism in the Chon Aike Silicic Province.

  3. Aplicación de Lodo de Procesos de Intercambio Iónico como Mitigante de la Sodicidad en un Suelo Agrícola Salino-Sódico

    Directory of Open Access Journals (Sweden)

    Octavio Armendáriz Alcaraz

    2013-09-01

    Full Text Available La salinidad y sodicidad en los suelos es un problema que afecta a una gran extensión de campos agrícolas. El sodio en exceso provoca el rompimiento de la estructura del suelo, volviéndolo impermeable, lo que reduce la cantidad de agua que llega a la zona de raíz. Se evaluó la eficiencia de tres dosis (D1= 0.424 g,D2= 1.061g y D3= 1.7 g de un tipo de lodo obtenido de la planta potabilizadora de agua subterránea “La Campiña II” en el tratamiento de un suelo salino-sódico (44.13 g usando columnas de suelo en el laboratorio. Se determinaron las propiedades fisicoquímicas del suelo y del lodo, así como la velocidad final de infiltración (VFI, la conductividad eléctrica (CE y la relación de absorción de sodio (RAS. La adición de este tipo de lodos mejoró significativamente las VFI respecto a las muestras sin recibir tratamiento. La dosis de 1.061 g presentó la mejor velocidad final de infiltración. Se puede concluir que los experimentos utilizando el lodo de la planta “La Campiña II” se obtuvieron resultados que lo hacen atractivo para su uso en suelos agrícolas con problemas de sodicidad.

  4. Radiopacity of restorative materials using digital images Radiopacidade de materiais restauradores utilizando imagens digitais

    Directory of Open Access Journals (Sweden)

    Leda Maria Pescinini Salzedas

    2006-04-01

    Full Text Available The radiopacity of esthetic restorative materials has been established as an important requirement, improving the radiographic diagnosis. The aim of this study was to evaluate the radiopacity of six restorative materials using a direct digital image system, comparing them to the dental tissues (enamel-dentin, expressed as equivalent thickness of aluminum (millimeters of aluminum. Five specimens of each material were made. Three 2-mm thick longitudinal sections were cut from an intact extracted permanent molar tooth (including enamel and dentin. An aluminum step wedge with 9 steps was used. The samples of different materials were placed on a phosphor plate together with a tooth section, aluminum step wedge and metal code letter, and were exposed using a dental x-ray unit. Five measurements of radiographic density were obtained from each image of each item assessed (restorative material, enamel, dentin, each step of the aluminum step wedge and the mean of these values was calculated. Radiopacity values were subsequently calculated as equivalents of aluminum thickness. Analysis of variance (ANOVA indicated significant differences in radiopacity values among the materials (PA radiopacidade dos materiais tem sido valorizada como importante requisito, incrementando o diagnóstico radiográfico. O objetivo deste estudo foi avaliar, no sistema digital Digora, as densidades radiográficas de 06 materiais restauradores comparando-os aos tecidos dentais (esmalte e dentina, expressos em milímetros de alumínio (mm Al. Foram confeccionadas 05 amostras de cada material e três cortes de um molar extraído hígido (incluindo esmalte e dentina, com 2 mm de espessura, e um penetrômetro de alumínio com 09 degraus. Sobre cada placa óptica foram colocados amostras dos diferentes materiais, um corte do dente humano, o penetrômetro e a identificação, e feita a exposição utilizando um aparelho de raios X. Foram obtidas 05 medidas de densidade radiográfica de

  5. Medial meniscus transplantation using cyanoacrylate in rabbits Transplante de menisco medial utilizando cianoacrilato em coelhos

    Directory of Open Access Journals (Sweden)

    Leandro José Reckers

    2006-04-01

    Full Text Available PURPOSE: To evaluate meniscal transplantation using as fixation method a synthetic glue derived from cyanoacrylate acid. METHODS: Twenty rabbits were used, of which 10 for autologous transplantation and 10 for homologous transplantation. For the autologous transplantation the meniscus was removed, and then transplanted in the same animal, using the synthetic glue. For the homologous transplantation, the study was divided into two stages: 1- Removal of the meniscus which was maintained at a temperature of 73ºC. 2- Use of cyanoacrylate acid-derived surgical adhesive for meniscal retransplantation in a different rabbit 30 days after the transplant. RESULTS: Due to complications, euthanasia had to be anticipated to the 15th day in the homologous group and to the 18th day in the autologous group. Macroscopically, knees submitted to transplantation presented whitish secretions from the surgical incision up to deep planes. Necrosis was observed in both groups. Statistical analysis has shown that mild (p=0.043 and moderate (p=0.001 complications emerged in a significantly earlier way in the homologous group, where euthanasia was also performed earlier (p=0,005. CONCLUSION: Synthetic surgical adhesives derived from cyanoacrylate acid promoted cortical to medullary bone necrosis bone in both groups.OBJETIVO: Avaliar macroscópica e histologicamente o transplante meniscal, utilizando-se a cola sintética derivada do ácido cianoacrilato como método de fixação. MÉTODOS: Foram utilizados 20 coelhos, tendo 10 realizado transplante autólogo e 10, homólogo. Para o transplante autólogo, o menisco foi retirado e em seguida transplantado no mesmo animal, sendo fixado com a cola sintética. Para o transplante homólogo o estudo foi dividido em duas etapas: 1- retirada do menisco e manutenção a uma temperatura de 73°C negativos. 2- Utilização do adesivo cirúrgico derivado do ácido cianoacrilato para reimplantar num coelho diferente 30 dias após o

  6. EVALUACIÓN DE LA VULNERABILIDAD SÍSMICA DE ESTRUCTURAS UTILIZANDO UN DISEÑO POR DESEMPEÑO

    Directory of Open Access Journals (Sweden)

    JULIÁN CARRILLO

    2008-01-01

    Full Text Available Debido a la actualización de los códigos de diseño sísmico, los requerimientos y la demanda sísmica con los cuales deben diseñarse las nuevas estructuras, comúnmente son mayores que los utilizados durante la etapa de diseño de edificaciones existentes. La mayoría de los estudios de vulnerabilidad que deben realizarse, se efectúan utilizando métodos simplificados incluidos en los códigos de diseño sísmico. Sin embargo, en la mayoría de los casos, son demasiado conservadores y poco representativos del comportamiento real de las estructuras. Usando un enfoque de diseño por desempeño, es posible tener una estimación más acertada de dicho comportamiento, permitiendo, en la mayoría de los casos, disminuir o eliminar los costos de una rehabilitaón estructural. En el artículo se presenta la descripción detallada y un caso de estudio de una de las técnicas disponibles para la realizar un estudio de vulnerabilidad sísmica utilizando un enfoque de diseño por desempeño.

  7. Identificação de artrite em suínos utilizando imagem termográfica

    Directory of Open Access Journals (Sweden)

    Daniela Espangue Graciano

    2014-01-01

    Full Text Available Nos sistemas intensivos de produção de suíno uma das afecções mais prevalentes são as artrites, que causam dor aos animais podendo afetar seu desempenho e bem-estar. Deste modo, o diagnóstico precoce torna-se importante para que se dispense aos animais tratamento adequado em tempo hábil. Objetivou-se com este estudo de caso, avaliar a eficiência do uso das imagens termográficas para identificação de artrite, ou de lesões em suínos. Foram utilizados cinco animais com suspeita de artrite nos membros posteriores. A temperatura superficial (TS dos membros posteriores foi registrada por meio de imagens termográficas utilizando o termovisor da Testo®. Foram calculadas as médias de 10 pontos da TS de cada membro posterior dos suínos, sendo posteriormente comparadas utilizando o teste t-Student, com confiabilidade de 95%. Os valores médios de TS foram menores (P≤0,05 no membro sadio (33,6°C, do que naquele com artrite (35,6°C evidenciando que, por meio de imagens termográficas, é possível a identificação de processos inflamatórios em suínos.

  8. MODELACIÓN DE LA DISTRIBUCIÓN DE VIAJES EN EL VALLE DE ABURRÁ UTILIZANDO EL MODELO GRAVITATORIO

    Directory of Open Access Journals (Sweden)

    CARLOS GONZÁLEZ

    2009-01-01

    Full Text Available El presente artículo se basa en los últimos estudios de transporte que se realizaron en el ÁreaMetropolitana del Valle de Aburrá: Encuesta Origen/Destino 2005 y Estudio de rutas de buses, Modelación de la Red Vial del Valle de Aburrá, y Plan Maestro de Movilidad. Se realiza el análisis y desarrollo del modelo de distribución de viajes para el Área Metropolitana del Valle de Aburrá utilizando el software TransCAD con los datos del año 2005, utilizando el modelo gravitatorio, el cual determina los viajes que existen entre una y otra zona de acuerdo con la generación y la atracción de viajes que existen entre las zonas relacionadas y una función de impedancia que depende del tiempo de viaje entre zonas. Se analizó el modelo para diferentes períodos y motivos y se encontró que la función de impedancia que mejor se adapta al modelo estudiado es la exponencial negativa.

  9. Chemical abrasion-SIMS (CA-SIMS) U-Pb dating of zircon from the late Eocene Caetano caldera, Nevada

    Science.gov (United States)

    Watts, Kathryn E.; Coble, Matthew A.; Vazquez, Jorge A.; Henry, Christopher D.; Colgan, Joseph P.; John, David A.

    2016-01-01

    Zircon geochronology is a critical tool for establishing geologic ages and time scales of processes in the Earth's crust. However, for zircons compromised by open system behavior, achieving robust dates can be difficult. Chemical abrasion (CA) is a routine step prior to thermal ionization mass spectrometry (TIMS) dating of zircon to remove radiation-damaged parts of grains that may have experienced open system behavior and loss of radiogenic Pb. While this technique has been shown to improve the accuracy and precision of TIMS dating, its application to high-spatial resolution dating methods, such as secondary ion mass spectrometry (SIMS), is relatively uncommon. In our efforts to U-Pb date zircons from the late Eocene Caetano caldera by SIMS (SHRIMP-RG: sensitive high resolution ion microprobe, reverse geometry), some grains yielded anomalously young U-Pb ages that implicated Pb-loss and motivated us to investigate with a comparative CA and non-CA dating study. We present CA and non-CA 206Pb/238U ages and trace elements determined by SHRIMP-RG for zircons from three Caetano samples (Caetano Tuff, Redrock Canyon porphyry, and a silicic ring-fracture intrusion) and for R33 and TEMORA-2 reference zircons. We find that non-CA Caetano zircons have weighted mean or bimodal U-Pb ages that are 2–4% younger than CA zircons for the same samples. CA Caetano zircons have mean U-Pb ages that are 0.4–0.6 Myr older than the 40Ar/39Ar sanidine eruption age (34.00 ± 0.03 Ma; error-weighted mean, 2σ), whereas non-CA zircons have ages that are 0.7–1.3 Myr younger. U-Pb ages do not correlate with U (~ 100–800 ppm), Th (~ 50–300 ppm) or any other measured zircon trace elements (Y, Hf, REE), and CA and non-CA Caetano zircons define identical trace element ranges. No statistically significant difference in U-Pb age is observed for CA versus non-CA R33 or TEMORA-2 zircons. Optical profiler measurements of ion microprobe pits demonstrate consistent depths of ~ 1.6

  10. Sixty thousand years of magmatic volatile history before the caldera-forming eruption of Mount Mazama, Crater Lake, Oregon

    Science.gov (United States)

    Wright, Heather M.; Bacon, Charles R.; Vazquez, Jorge A.; Sisson, Thomas W.

    2012-01-01

    The well-documented eruptive history of Mount Mazama, Oregon, provides an excellent opportunity to use pre-eruptive volatile concentrations to study the growth of an explosive silicic magmatic system. Melt inclusions (MI) hosted in pyroxene and plagioclase crystals from eight dacitic–rhyodacitic eruptive deposits (71–7.7 ka) were analyzed to determine variations in volatile-element concentrations and changes in magma storage conditions leading up to and including the climactic eruption of Crater Lake caldera. Temperatures (Fe–Ti oxides) increased through the series of dacites, then decreased, and increased again through the rhyodacites (918–968 to ~950 to 845–895 °C). Oxygen fugacity began at nickel–nickel-oxide buffer (NNO) +0.8 (71 ka), dropped slightly to NNO +0.3, and then climbed to its highest value with the climactic eruption (7.7 ka) at NNO +1.1 log units. In parallel with oxidation state, maximum MI sulfur concentrations were high early in the eruptive sequence (~500 ppm), decreased (to ~200 ppm), and then increased again with the climactic eruption (~500 ppm). Maximum MI sulfur correlates with the Sr content (as a proxy for LREE, Ba, Rb, P2O5) of recharge magmas, represented by basaltic andesitic to andesitic enclaves and similar-aged lavas. These results suggest that oxidized Sr-rich recharge magmas dominated early and late in the development of the pre-climactic dacite–rhyodacite system. Dissolved H2O concentrations in MI do not, however, correlate with these changes in dominant recharge magma, instead recording vapor solubility relations in the developing shallow magma storage and conduit region. Dissolved H2O concentrations form two populations through time: the first at 3–4.6 wt% (with a few extreme values up to 6.1 wt%) and the second at ≤2.4 wt%. CO2 concentrations measured in a subset of these inclusions reach up to 240 ppm in early-erupted deposits (71 ka) and are below detection in climactic deposits (7.7 ka). Combined H2O and

  11. Deformation near the Casa Diablo geothermal well field and related processes Long Valley caldera, Eastern California, 1993-2000

    Science.gov (United States)

    Howle, J.F.; Langbein, J.O.; Farrar, C.D.; Wilkinson, S.K.

    2003-01-01

    Regional first-order leveling lines, which extend from Lee Vining, CA, to Tom's Place, CA, have been surveyed periodically since 1957 by the U.S. Geological Survey (USGS), the National Geodetic Survey (NGS), and Caltrans. Two of the regional survey lines, or leveling networks, intersect at the Casa Diablo geothermal well field. These leveling networks, referenced to a distant bench mark (C916) near Lee Vining, provide time-series vertical control data of land-surface deformation that began around 1980. These data are also useful for delineating localized subsidence at Casa Diablo related to reservoir pressure and temperature changes owing to geothermal development that began in 1985. A comparison of differences in bench-mark elevations for five time periods between 1983 and 1997 shows the development and expansion of a subsidence bowl at Casa Diablo. The subsidence coincides spatially with the geothermal well field and temporally with the increased production rates and the deepening of injection wells in 1991, which resulted in an increase in the rate of pressure decline. The subsidence, superimposed on a broad area of uplift, totaled about 310 mm by 1997. The USGS established orthogonal tilt arrays in 1983 to better monitor deformation across the caldera. One tilt array (DBR) was established near what would later become the Casa Diablo geothermal well field. This array responded to magmatic intrusions prior to geothermal development, tilting away from the well field. With the start of geothermal fluid extraction in 1985, tilt at the DBR array reversed direction and began tilting into the well field. In 1991, geothermal power production was increased by a factor of four, and reservoir pressures began a period of steep decline. These changes caused a temporary three-fold increase in the tilt rate. The tilt rate became stable in 1993 and was about 40% lower than that measured in 1991-1992, but still greater than the rates measured during 1985-1990. Data from the

  12. Complejo Caldera Diamante-volcán Maipo (34°10'S, 69º50'O: Evolución volcanológica y geoquímica e implicancias en su peligrosidad Volcanological and geochemical evolution and hazard assessment of the Diamante Caldera-Maipo Volcano Complex (34°10'S, 69º50'W

    Directory of Open Access Journals (Sweden)

    Patricia Sruoga

    2012-12-01

    Full Text Available El Complejo Caldera Diamante-Volcán Maipo (34°10' S, 69º50' O se halla situado en el extremo norte de la Zona Volcánica Sur. Su actividad se remonta a 450/150 ka, posee un registro histórico incierto y carece de manifestaciones fumarólicas o hidrotermales. Su evolución abarca dos etapas: 1 Diamante, con la formación de una caldera de colapso (20x16 km y el emplazamiento de ignimbritas de gran volumen y 2 Maipo, con la construcción de un estratovolcán, domo anular y conos adventicios asociados. Esta etapa comprende siete eventos eruptivos principales (cuatro preglaciales: 86 ± 10 ka / 88 ± 7 ka, 75 ± 16 ka, 45 ± 14 ka y 28 ± 17 ka y tres postglaciales: The Caldera Diamante-Maipo volcanic complex (34°10' S, 69º50' W is located at the northern end of the South Volcanic Zone. The eruptive activity started 450/150 ka ago and its historic record remains uncertain. At present, neither fumarolic activity nor hydrothermal manifestations are detected. Two main stages are distinguished in the evolution of the volcanic complex: 1 "Diamante stage" corresponds to the emplacement of large-volume ignimbrites associated to a 20 by 16 km in diameter collapse caldera and 2 the "Maipo stage" represents andesite-dacite stratocone-building lavas and pyroclastics, a ring-fault dome and parasitic cones emplaced during the last 100 ka of the complex lifetime (4 pre-glacial events: 86 ± 10 ka / 88 ± 7 ka, 75 ± 16 ka, 45 ± 14 ka, 28 ± 17 ka and 3 post-glacial events <14 ka. Scoria flows and fall deposits near the summit are assigned to the recent explosive record. The last eruption tentatively occurred in 1912. The volcanics define a high-K, calc-alkaline suite ranging in silica from 54% to 74%. The Maipo series encompasses two pyroxene with minor olivine andesites and two pyroxene and hornblende dacites. Magmatic differentiation is strongly controlled by fractional crystallization. However, periodic magma mixing and crustal assimilation should have

  13. Magma injection beneath the urban area of Naples: a new mechanism for the 2012–2013 volcanic unrest at Campi Flegrei caldera

    Science.gov (United States)

    D’Auria, Luca; Pepe, Susi; Castaldo, Raffaele; Giudicepietro, Flora; Macedonio, Giovanni; Ricciolino, Patrizia; Tizzani, Pietro; Casu, Francesco; Lanari, Riccardo; Manzo, Mariarosaria; Martini, Marcello; Sansosti, Eugenio; Zinno, Ivana

    2015-01-01

    We found the first evidence, in the last 30 years, of a renewed magmatic activity at Campi Flegrei caldera from January 2012 to June 2013. The ground deformation, observed through satellite interferometry and GPS measurements, have been interpreted as the effect of the intrusion at shallow depth (3090 ± 138 m) of 0.0042 ± 0.0002 km3 of magma within a sill. This interrupts about 28 years of dominant hydrothermal activity and occurs in the context of an unrest phase which began in 2005 and within a more general ground uplift that goes on since 1950. This discovery has implications on the evaluation of the volcanic risk and in the volcanic surveillance of this densely populated area. PMID:26279090

  14. Zeolitas (Clinoptilolita-Analcima-Filipsita) en depósitos iroclásticos miocenos del borde de la Caldera de Tejeda (Gran Canaria, Islas Cnarias)

    OpenAIRE

    García del Cura, M. Ángeles; La Iglesia Fernández , Ángel; Ordoñez Delgado, Salvador

    1999-01-01

    Se ha estudiado la composición química y mineralógica de las tobas miocenas azulverdosas o "azulejos" del borde oeste de la Caldera de Tejeda (Gran Canaria). Mediante técnicas de microscopía óptica, electrónica (de transmisión y barrido), análisis térmico, difracción de rayos X y análisis químico (FRX y MEB con EDAX) se han identificado los minerales presentes. La asociación mineral está formada básicamente por feldespatos (principalmente anortoc1asa), cuarzo, cristo balita, mica, minerale...

  15. Evaluación de la calidad ambiental de los sedimentos marinos en el sistema de bahías de Caldera (27°S, Chile

    Directory of Open Access Journals (Sweden)

    Jorge Valdés

    2014-07-01

    Full Text Available Se midió la concentración y distribución de Cu, Ni, Pb, V, Fe, Al y Zn en los sedimentos marinos en cuatro bahías (Caldera, Calderilla, Inglesa y Salada de la Región de Atacama, Chile. Las concentraciones medias globales fueron 76,8 mg kg-1 de Cu, 90,4 mg kg-1 de Zn, 39 mg kg-1 de Pb, 23,4 mg kg-1 de Ni, 118,5 mg kg-1 de V, 0,09% de Fe y 0,1 mg kg-1 para Al. El análisis estadístico realizado sobre la distribución y contenido de metales encontrado en estas bahías permitió separarlas en tres grupos diferentes; bahía Caldera caracterizada por un alto grado de industrialización, principalmente con actividades asociadas a la minería, bahía Calderilla con actividades de cultivos marinos y actividad industrial asociada a la pesca industrial, y bahías Inglesa y Salada, muy similares entre sí, caracterizadas por una intensa actividad de cultivos marinos y escasa o nula influencia de actividad industrial minera o pesquera. La aplicación del índice de geoacumulación y de normas ambientales de calidad de sedimentos permiten concluir que los niveles de metales medidos en estas bahías muestran un enriquecimiento incipiente asociado a la actividad antrópica desarrollada en la zona pero que, de momento solamente, suponen un riesgo ocasional para las comunidades bentónicas.

  16. Heat flow in vapor dominated areas of the Yellowstone Plateau volcanic field: implications for the thermal budget of the Yellowstone Caldera

    Science.gov (United States)

    Hurwitz, Shaul; Harris, Robert; Werner, Cynthia Anne; Murphy, Fred

    2012-01-01

    Characterizing the vigor of magmatic activity in Yellowstone requires knowledge of the mechanisms and rates of heat transport between magma and the ground surface. We present results from a heat flow study in two vapor dominated, acid-sulfate thermal areas in the Yellowstone Caldera, the 0.11 km2 Obsidian Pool Thermal Area (OPTA) and the 0.25 km2 Solfatara Plateau Thermal Area (SPTA). Conductive heat flux through a low permeability layer capping large vapor reservoirs is calculated from soil temperature measurements at >600 locations and from laboratory measurements of soil properties. The conductive heat output is 3.6 ± 0.4 MW and 7.5 ± 0.4 MW from the OPTA and the SPTA, respectively. The advective heat output from soils is 1.3 ± 0.3 MW and 1.2 ± 0.3 MW from the OPTA and the SPTA, respectively and the heat output from thermal pools in the OPTA is 6.8 ± 1.4 MW. These estimates result in a total heat output of 11.8 ± 1.4 MW and 8.8 ± 0.4 MW from OPTA and SPTA, respectively. Focused zones of high heat flux in both thermal areas are roughly aligned with regional faults suggesting that faults in both areas serve as conduits for the rising acid vapor. Extrapolation of the average heat flux from the OPTA (103 ± 2 W·m−2) and SPTA (35 ± 3 W·m−2) to the ~35 km2 of vapor dominated areas in Yellowstone yields 3.6 and 1.2 GW, respectively, which is less than the total heat output transported by steam from the Yellowstone Caldera as estimated by the chloride inventory method (4.0 to 8.0 GW).

  17. Fluid-faulting evolution in high definition: Connecting fault structure and frequency-magnitude variations during the 2014 Long Valley Caldera, California earthquake swarm

    Science.gov (United States)

    Shelly, David R.; Ellsworth, William L.; Hill, David P.

    2016-01-01

    An extended earthquake swarm occurred beneath southeastern Long Valley Caldera between May and November 2014, culminating in three magnitude 3.5 earthquakes and 1145 cataloged events on 26 September alone. The swarm produced the most prolific seismicity in the caldera since a major unrest episode in 1997-1998. To gain insight into the physics controlling swarm evolution, we used large-scale cross-correlation between waveforms of cataloged earthquakes and continuous data, producing precise locations for 8494 events, more than 2.5 times the routine catalog. We also estimated magnitudes for 18,634 events (~5.5 times the routine catalog), using a principal component fit to measure waveform amplitudes relative to cataloged events. This expanded and relocated catalog reveals multiple episodes of pronounced hypocenter expansion and migration on a collection of neighboring faults. Given the rapid migration and alignment of hypocenters on narrow faults, we infer that activity was initiated and sustained by an evolving fluid pressure transient with a low-viscosity fluid, likely composed primarily of water and CO2 exsolved from underlying magma. Although both updip and downdip migration were observed within the swarm, downdip activity ceased shortly after activation, while updip activity persisted for weeks at moderate levels. Strongly migrating, single-fault episodes within the larger swarm exhibited a higher proportion of larger earthquakes (lower Gutenberg-Richter b value), which may have been facilitated by fluid pressure confined in two dimensions within the fault zone. In contrast, the later swarm activity occurred on an increasingly diffuse collection of smaller faults, with a much higher b value.

  18. Insights into the 3D architecture of an active caldera ring-fault at Tendürek volcano through modeling of geodetic data

    KAUST Repository

    Vasyura-Bathke, Hannes

    2015-04-28

    The three-dimensional assessment of ring-fault geometries and kinematics at active caldera volcanoes is typically limited by sparse field, geodetic or seismological data, or by only partial ring-fault rupture or slip. Here we use a novel combination of spatially dense InSAR time-series data, numerical models and sand-box experiments to determine the three-dimensional geometry and kinematics of a sub-surface ring-fault at Tendürek volcano in Turkey. The InSAR data reveal that the area within the ring-fault not only subsides, but also shows substantial westward-directed lateral movement. The models and experiments explain this as a consequence of a ‘sliding-trapdoor’ ring-fault architecture that is mostly composed of outward-inclined reverse segments, most markedly so on the volcano\\'s western flanks but includes inward-inclined normal segments on its eastern flanks. Furthermore, the model ring-fault exhibits dextral and sinistral strike-slip components that are roughly bilaterally distributed onto its northern and southern segments, respectively. Our more complex numerical model describes the deformation at Tendürek better than an analytical solution for a single rectangular dislocation in a half-space. Comparison to ring-faults defined at Glen Coe, Fernandina and Bárðarbunga calderas suggests that ‘sliding-trapdoor’ ring-fault geometries may be common in nature and should therefore be considered in geological and geophysical interpretations of ring-faults at different scales worldwide.

  19. Causes of unrest at silicic calderas in the East African Rift: New constraints from InSAR and soil-gas chemistry at Aluto volcano, Ethiopia

    Science.gov (United States)

    Hutchison, William; Biggs, Juliet; Mather, Tamsin A.; Pyle, David M.; Lewi, Elias; Yirgu, Gezahegn; Caliro, Stefano; Chiodini, Giovanni; Clor, Laura E.; Fischer, Tobias P.

    2016-08-01

    Restless silicic calderas present major geological hazards, and yet many also host significant untapped geothermal resources. In East Africa, this poses a major challenge, although the calderas are largely unmonitored their geothermal resources could provide substantial economic benefits to the region. Understanding what causes unrest at these volcanoes is vital for weighing up the opportunities against the potential risks. Here we bring together new field and remote sensing observations to evaluate causes of ground deformation at Aluto, a restless silicic volcano located in the Main Ethiopian Rift (MER). Interferometric Synthetic Aperture Radar (InSAR) data reveal the temporal and spatial characteristics of a ground deformation episode that took place between 2008 and 2010. Deformation time series reveal pulses of accelerating uplift that transition to gradual long-term subsidence, and analytical models support inflation source depths of ˜5 km. Gases escaping along the major fault zone of Aluto show high CO2 flux, and a clear magmatic carbon signature (CO2-δ13C of -4.2‰ to -4.5‰). This provides compelling evidence that the magmatic and hydrothermal reservoirs of the complex are physically connected. We suggest that a coupled magmatic-hydrothermal system can explain the uplift-subsidence signals. We hypothesize that magmatic fluid injection and/or intrusion in the cap of the magmatic reservoir drives edifice-wide inflation while subsequent deflation is related to magmatic degassing and depressurization of the hydrothermal system. These new constraints on the plumbing of Aluto yield important insights into the behavior of rift volcanic systems and will be crucial for interpreting future patterns of unrest.

  20. Fluid-faulting evolution in high definition: Connecting fault structure and frequency-magnitude variations during the 2014 Long Valley Caldera, California, earthquake swarm

    Science.gov (United States)

    Shelly, David R.; Ellsworth, William L.; Hill, David P.

    2016-03-01

    An extended earthquake swarm occurred beneath southeastern Long Valley Caldera between May and November 2014, culminating in three magnitude 3.5 earthquakes and 1145 cataloged events on 26 September alone. The swarm produced the most prolific seismicity in the caldera since a major unrest episode in 1997-1998. To gain insight into the physics controlling swarm evolution, we used large-scale cross correlation between waveforms of cataloged earthquakes and continuous data, producing precise locations for 8494 events, more than 2.5 times the routine catalog. We also estimated magnitudes for 18,634 events (~5.5 times the routine catalog), using a principal component fit to measure waveform amplitudes relative to cataloged events. This expanded and relocated catalog reveals multiple episodes of pronounced hypocenter expansion and migration on a collection of neighboring faults. Given the rapid migration and alignment of hypocenters on narrow faults, we infer that activity was initiated and sustained by an evolving fluid pressure transient with a low-viscosity fluid, likely composed primarily of water and CO2 exsolved from underlying magma. Although both updip and downdip migration were observed within the swarm, downdip activity ceased shortly after activation, while updip activity persisted for weeks at moderate levels. Strongly migrating, single-fault episodes within the larger swarm exhibited a higher proportion of larger earthquakes (lower Gutenberg-Richter b value), which may have been facilitated by fluid pressure confined in two dimensions within the fault zone. In contrast, the later swarm activity occurred on an increasingly diffuse collection of smaller faults, with a much higher b value.

  1. Determinación de la curva de destilación flash para cortes de petróleo utilizando simuladores comerciales

    OpenAIRE

    Erdmann, Eleonora; Humana, Demetrio; Franco Domínguez, Samuel; Mercado Fuentes, Lorgio

    2010-01-01

    El presente trabajo describe un nuevo método para estimar la curva de destilación flash EFV (equilibrium flash vapo-rization) para cortes de petróleo utilizando simuladores comerciales. Para ello se implementa un modelo estaciona-rio de la destilación flash en un simulador comercial, y se ajusta el modelo utilizando una curva de destilación obte-nida con procedimientos estándares de laboratorio. Dicha curva puede ser del tipo TBP, ASTM D86, D1160 o D2887, entre otras; e involucra un procedimi...

  2. Intolerância glicêmica e o prognóstico perinatal em gestantes utilizando anti-retrovirais

    Directory of Open Access Journals (Sweden)

    El Beitune Patrícia

    2003-01-01

    Full Text Available OBJETIVOS: estudar o efeito das drogas anti-retrovirais sobre o metabolismo glicêmico em gestantes portadoras do HIV-1 e a ação dessas medicações sobre o prognóstico perinatal. MÉTODOS: estudo prospectivo realizado em 57 gestantes divididas em três grupos: grupo AZT, utilizando zidovudina (n=20; grupo TT, utilizando zidovudina+lamivudina+nelfinavir (n=25, e grupo controle, gestantes normais (n=12. Obteve-se a área sob a curva (ASC das glicemias após teste oral de tolerância à glicose com 75 g de glicose em quatro oportunidades durante a gravidez (1º=14-20 semanas, 2º=21-26 semanas, 3º=27-32 semanas e 4º=33-38 semanas. O prognóstico perinatal levou em consideração as taxas de prematuridade, restrição de crescimento intra-útero (RCIU, baixo peso ao nascer, mortalidade perinatal e transmissão vertical do HIV-1. Os dados foram analisados utilizando-se os testes não paramétricos do c², de Friedman e de Kruskal-Wallis. RESULTADOS: os valores da mediana da ASC foi de 11.685 mg/dL-2h para o grupo controle, 13.477 mg/dL-2h para o grupo AZT e 13.650 mg/dL-2h para o grupo TT (p=0,049. Não se observou efeito deletério dos anti-retrovirais sobre as taxas de prematuridade, baixo peso ao nascer, RCIU e índices de Apgar. Não houve nenhum caso de transmissão vertical do HIV-1. CONCLUSÕES: verificou-se o desenvolvimento de intolerância glicêmica em gestantes que utilizaram tratamento tríplice, não sendo observado naquelas que utilizaram apenas AZT. Não houve efeitos deletérios dos anti-retrovirais sobre o prognóstico perinatal.

  3. Tectonic evolution and mineralized characteristics of Taipusi caldera, Inner Mongolia%内蒙古太仆寺旗破火山演化过程及其成矿规律

    Institute of Scientific and Technical Information of China (English)

    王向兰; 胥迎红

    2012-01-01

    The outer ring of the caldera at Taipusi is low and gentle mountains which are comprised of lava from overflows and extrusive facies; the inside ring is aerial moutains which are comprise of pumice flow deposits from explosive facies. The center is taken up by the granite porphyry body from intrusion facies. The evolution of the caldera has gone through the evolutionary process in various ways including a sudden intense burst - the sinking of caldera - the formation of crate - the activity of the parasitic volcano - the resurgence of the caldera,etal. The model of action and the composition of magma have a great difference in the different stages. The mineralization locates in the contact zone of granite - porphyry of intrusive facies and froth of extrusice facies that superposed by the volcanic faults in the center of caldera. There are multiple factors of ore - controlling, such as east - west basement faults, caldera tectonics, porphyries body in the center, faults formed after the eruption,etal.%太仆寺旗破火山外环为相对低缓的山体,由溢流相和侵出相熔岩构成,内环为高山,由爆发相浮岩流堆积物构成,中心主要由侵入相花岗斑岩体占据.火山喷发经历了强烈喷发一破火山塌陷—破火山口形成—侧火山活动和破火山口复活等不同活动方式的演化过程,不同阶段火山活动方式和岩浆成分均有较大差异.破火山矿化主要发牛在花岗斑岩与侵出相泡沫熔岩接触带并有火山期后断裂叠加的部位,受东西向基底断裂、破火山口构造、破火山中心斑岩体和火山期后断裂等多重因素控制.