Under what conditions will a volcano erupt? Can we predict the eruption behavior of a volcano by studying rocks from its previous eruptions? Definitive answers to these questions still elude geoscientists. It is known that water greatly influences the properties of magmas, including magma viscosity, degree of crystallization of the melt, and whether a volcano erupts explosively or quietly extrudes magma flows.
This work explores the possibility that crystals formed from magmas in Mount St. Helens are "time capsules" of magmatic water content- more specifically, that the concentration of structural hydroxyl groups in the feldspar phenocrysts from each eruption is a proxy for the water content of the magma that it grew from. For more information about this research, and to find other web sites about Mount St. Helens, click on the links below.
Postcard picture of Mount St. Helens before the May 18, 1980 eruption.