This is an accomplishment-based renewal of a project designed to study how volatile species, such as H2O and CO2, can play a fundamental role in determining the explosivity of volcanic eruptions. Chemical aspects of magmatic degassing are well constrained from studies of dissolved volatiles in melts and gas emissions from volcanic systems. Recent experiments have also improved our understanding of the way the bubbles nucleate and grow as volatile-rich magma rises toward the surface. Still scarce, however, are studies that link chemical and physical processes related to the movement of volatile phases through subvolcanic systems. In this renewal, Cashman will address this problem by (1) extending recent work to examine physical movement of gases through volcanic systems using chemical signatures, (2) developing new techniques to quantify the structure of porous volcanic rocks, (3) relate the structure of porous samples to permeable flow characteristics, and (4) combine the structural and chemical data to trace the migration of volatiles (gases) through volcanic systems. This work will improve both our basic understanding of volcanic processes and our interpretation of volcano monitoring data. A specific application will be the ongoing eruption of Mount St. Helens, WA.
