Analyses of pyroclastic deposits as a tool for investigating the dynamics of volcanic eruptions

Abstract

Recent progress in the science of the products of volcanic eruptions has made it possible to reconstruct past eruption processes on the basis of high-resolution volcanic stratigraphy. Case studies on changing eruption style and related conduit-and magma chamber-processes are helpful in establishing systematic, general patterns for the development of eruptions. They also contribute information towards an eruption mechanism tree that describes bifurcations in eruption processes according to the governing conditions. Methodological progress has been made on various aspects of eruptions, including our understanding of magma-ascent processes in relation to decompression-induced crystallization of groundmass microlites, precise determinations of volatile solubility in silicate melts, the development of analytical methods to measure volatile contents in glass and estimate magma pressure, the accumulation of permeability data, and advances in analytical techniques for rock microstructures (e.g., X-ray microtomography). Given these developments, we can retrieve information on the timescales of eruption dynamics and on the volume of erupted materials from the volcanic stratigraphy.Keywords: pyroclastic deposit, volcanic stratigraphy, pumice, eruption dynamics, degassing, fragmentation Michihiko Nakamura