This project is to carry out geochemical, physical, and experimental analyses of the pumice falls that resulted from plinian eruptions of Mount St. Helens. The objectives will be to examine the relationship between changes in eruption dynamics and differences in magmatic composition, rheology, and volatile content. Changes in the storage of magma (e.g., pressure, temperature, degree of volatile saturation) during the last 4,000 years at Mount St. Helens will also be investigated and examined for correlations to variations in eruption dynamics. This integrated physical-volcanologic, petrologic, and experimental study of actual eruptions will complement theoretical work to better understand the factors which control the style of explosive volcanism and the composition of its products.
