Staff and Postgraduate Students
Miss Iona McIntosh
Bubbles in magma: reconstructing eruption dynamics from volatile concentrations in glass
Volcanic eruptions are driven by the nucleation and growth of bubbles, formed when volatile species dissolved in the melt come out of solution, often as a result of depressurisation due to ascent through the crust. The rate and extent of bubble growth are key factors controlling the explosivity of the eruption. Bubbles grow through two mechanisms: 1) diffusion of volatiles (chiefly water) from the silicate melt into the bubble, and 2) decompressive expansion. These two processes combine to modify the concentration of water in the melt around the bubbles, creating a record of the bubbles’ growth history. These concentration variations may be preserved when the magma is quenched to glass. The novel technique used in this project calibrates backscatter SEM images to create high resolution measurements of water concentration variations in volcanic glass, allowing this record to be read for the first time. These measurements will be used to improve current models of bubble growth, ultimately increasing our understanding of how and why volcanoes erupt.