A genetic classification of collapse calderas based on field studies, and analogue and theoretical modelling
Published:January 01, 2009
J. Martí, A. Geyer, A. Folch, 2009. "A genetic classification of collapse calderas based on field studies, and analogue and theoretical modelling", Studies in Volcanology: The Legacy of George Walker, T. Thordarson, S. Self, G. Larsen, S. K. Rowland, Á. Höskuldsson
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Many calderas are the culmination of long-lived volcanic systems. Field-based studies provide detailed descriptions and interpretations of the origins of individual examples, while analogue and mathematical modelling provide insights about caldera formation. Caldera morphology and structure yield information on subsidence mechanisms and geometry of the associated magma chamber, while studies of eruptive products address aspects of magma composition and eruption dynamics. Combining field data with analogue and numerical modelling leads us to propose a genetic classification of calderas based on the stress conditions that permit formation of ring faults and the pressure evolution in the magma chamber during a caldera-forming eruption. Two main end-members, referred to here as overpressure and underpressure calderas, develop from different initial conditions and generate different sequences of caldera-forming deposits. With overpressure calderas, stress conditions leading to the formation of ring faults are achieved prior to initiation of the eruption when an overpressurized sill-like magma chamber is loaded by mag-matic regional doming or subjected to regional extension. Caldera collapse is initiated near at the beginning of the eruption and the resulting eruptions are often very large. By comparison, underpressure calderas result from ring fault subsidence after significant decompression of the magma chamber following a pre-caldera eruptive episode.
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Studies in Volcanology: The Legacy of George Walker
Professor George Patrick Leonard Walker was one of the fathers of modern quantitative volcanology and arguably the foremost volcanologist of the twentieth century. In his long career, George studied a wide spectrum of volcanological problems and in doing so influenced almost every branch of the field. This volume, which honours his memory and his contributions to the field of volcanology, contains a collection of papers inspired by, and building upon, many of the ideas previously developed by George. Many of the contributors either directly studied under and worked with George, or were profoundly influenced by his ideas. The topics broadly fall under the three themes of lava flows and effusion, explosive volcanism, and volcanoes and their infrastructure.