An investigation of volcanic depressions. Part 1 - Geologic and geophysical features of calderas Progress report

Preferred classification of calderas and volcano- tectonic depressions based on relative amounts of lava and proclastic eject

Maars to calderas. End-members on a spectrum of explosive volcanic depressions

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

Propuesta de una guía de procedimientos para evaluar la integridad mecánica de las calderas pirotubulares en las Empresas Nicaragüenses en un período de Abril a Junio del 2014

El presente trabajo investigativo consiste en proponer una guía de procedimientos para evaluar la integridad mecánica de las calderas pirotubulares en las empresas Nicaragüenses, con el fin de brindar una herramienta básica que brinde los pasos a seguir para realizar un buen diagnóstico de dichas maquinas. Dentro de la problemática, el país no cuenta con una guía de procedimientos para evaluar la integridad mecánica de las calderas pirotubulares, lo cual permite que se presenten fallas que provoquen paros repentinos y disminuya la calidad del producto, etc. El estudio posee un enfoque cualitativo, siendo el tipo de investigación descriptivo y de corte transversal porque se elaboró en un periodo comprendido de abril a junio del 2014. La metodología que se utilizó para realizar la investigación fue documental, mediante la recopilación de información en libros, folletos, entre otros, para conformar el marco teórico relacionado al tema. En el análisis y resultados: en el inciso A. se describen conceptos, clasificación, funcionamiento y partes de las calderas pirotubulares esto para lograr un mejor entendimiento a la hora de ver la guía. En el inciso B. podrá encontrar las técnicas no destructivas del mantenimiento predictivo el cual nos da la base para la elaboración de la guía. El inciso C. presenta las posibles fallas que pueden presentar las calderas pirotubulares. Y por último en el inciso D. encuentran la propuesta de una guía de procedimientos para evaluar la integridad mecánica de las calderas pirotubulares. La guía podrá ser usada por las empresas que posean dentro de sus maquinarias calderas pirotubulare

Influence of regional tectonics and pre-existing structures on the formation of elliptical calderas in the Kenyan Rift

Calderas are formed by the collapse of large magma reservoirs and are commonly elliptical in map view. The orientation of elliptical calderas is often used as an indicator of the local stress regime; but, in some rift settings, pre-existing structural trends may also influence the orientation. We investigated whether either of these two mechanisms controls the orientation of calderas in the Kenyan Rift. Satellite-based mapping was used to identify the rift border faults, intra-rift faults and orientation of the calderas to measure the stress orientations and pre-existing structural trends and to determine the extensional regime at each volcano. We found that extension in northern Kenya is orthogonal, whereas that in southern Kenya is oblique. Elliptical calderas in northern Kenya are orientated NW–SE, aligned with pre-existing structures and perpendicular to recent rift faults. In southern Kenya, the calderas are aligned NE–SW and lie oblique to recent rift faults, but are aligned with pre-existing structures. We conclude that, in oblique continental rifts, pre-existing structures control the development of elongated magma reservoirs. Our results highlight the structural control of magmatism at different crustal levels, where pre-existing structures control the storage and orientation of deeper magma reservoirs and the local stress regime controls intra-rift faulting and shallow magmatism. Supplementary material: Details of the Standard Deviation Ellipse function and statistical methods are available at http://www.geolsoc.org.uk/SUP18849

Summary of space imagery studies in Utah and Nevada

The author has identified the following significant results. An enhanced enlargement of a S190B color image at a scale of 1/19,200 of the Bingham porphyry copper deposit has compared a geological map of the area with the space imagery map as fair for the intrusion boundaries and total lack of quality for mapping the sediments. Hydrothermal alteration is only slightly evident on space imagery at Bingham, but in the Tintic mining district and the volcanic piles of the Keg and Thomas ranges, Utah, hydrothermal alteration is readily mapped on color enlargements of S190B. Several sites of calderas were recognized and new ones located on space imagery. One of the tools developed is a mercury soil-gas analyzer that is becoming significant as an aid in locating hidden mineralized zones which were suggested from space imagery. In addition, this tool is a prime aid in locating and better delineating geothermal sites

Impact of volcanism on the sedimentary record of the Neuquén rift basin, Argentina: towards a cause and effect model

The analysis of volcano-sedimentary infill in sedimentary basins constitutes a challenge for basin analysis and hydrocarbon exploration worldwide. In order to understand the contribution of volcanism to the sedimentary record in rift basins, we study the Jurassic effusive-explosive volcanic infill of an inverted extensional depocentre at the Neuquén Basin, Argentina. A cause and effect model that evaluates the relationship between volcanism and sedimentation was devised to develop a conceptual model for the tectono-stratigraphic evolution of this volcanic rift basin. We show how the variations in the volcanism, coupled with the activity of extensional faults, determined the types of volcanic edifices (i.e., composite volcanoes, graben-calderas, and lava fields). Volcanic edifices controlled the stacking patterns of the volcanic units as well as sedimentary systems. The landform of the volcanic edifices, as well as the styles and scales of the eruptions governed the sedimentary input to the basin, setting the main variables of the sedimentary systems, such as provenance, grain size, transport and deposition and geometry. As a result, the contrasting volcaniclastic input, from higher volcaniclastic input to lower volcaniclastic input, associated with different subsidence patterns, determined the high-resolution syn-rift infill patterns of the extensional depocentre. The cause and effect model presented in this study isolates the variables of the volcanic environments that control the sedimentary scenarios. We suggest that, by adjusting the first order input parameters of the model, these cause and effect scenarios could be adapted to similar rift basins, in order to establish predictive facies models with stratigraphic controls, and the impact of volcanism on their stratigraphic records.Fil: D'Elia, Leandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; ArgentinaFil: Martí, Joan. Consejo Superior de Investigaciones Científicas. Instituto de Ciencias de la Tierra Jaume Almera; EspañaFil: Muravchik, Martin. University Of Bergen; Noruega. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Bilmes, Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico de Geología y Paleontología.; ArgentinaFil: Franzese, Juan Rafael. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentin

Major lineaments and possible calderas defined by side looking airborne radar imagery, St. Francois Mountains, Missouri

Side-looking radar imagery superiority over aerial photography of geological faults and patterns in St. Francis Mountains, Missour

Geologic interpretation of a radar mosaic of Yellowstone National Park

Geologic mapping of Yellowstone National Park area by interpretation of radar imager

Probabilistic enhancement of the Failure Forecast Method using a stochastic differential equation and application to volcanic eruption forecasts

We introduce a doubly stochastic method for performing material failure theory based forecasts of volcanic eruptions. The method enhances the well known Failure Forecast Method equation, introducing a new formulation similar to the Hull-White model in financial mathematics. In particular, we incorporate a stochastic noise term in the original equation, and systematically characterize the uncertainty. The model is a stochastic differential equation with mean reverting paths, where the traditional ordinary differential equation defines the mean solution. Our implementation allows the model to make excursions from the classical solutions, by including uncertainty in the estimation. The doubly stochastic formulation is particularly powerful, in that it provides a complete posterior probability distribution, allowing users to determine a worst case scenario with a specified level of confidence. We apply the new method on historical datasets of precursory signals, across a wide range of possible values of convexity in the solutions and amounts of scattering in the observations. The results show the increased forecasting skill of the doubly stochastic formulation of the equations if compared to statistical regression.Comment: 27 pages, 13 figure

Proceedings of the MEVTV Workshop on The Evolution of Magma Bodies on Mars

The workshop focused on many of the diverse approaches related to the evolution of magma bodies on Mars that have been pursued during the course of the Mars Evolution of Volcanism, Tectonism, and Volatiles (MEVTV) Program. Approximately 35 scientists from the Mars volcanology, petrology, geochemistry, and modeling communities attended. Segments of the meeting concentrated of laboratory analyses and investigations of SNC meteorites, the interpretation of Viking Orbiter and Lander datasets, and the interpretation of computer codes that model volcanic and tectonic processes on Mars. Abstracts of these reports are presented