Formation of dense lava from vesicular silicic magma

Abstract

Foam collapse is the necessary process for explaining non-explosive silicic eruptions. However, no direct evidence showed that the foam collapse was actually operating in natural magma. We analysed groundmass glass of Mukaiyama rhyolite lava using an FE-EPMA, and observed spatial heterogeneity in the volatile content. We interpret this heterogeneity as reflecting the history of degassing and compaction of magma.