Abstract:

The crater of Mount St. Helens is a unique natural laboratory to study volcano-ice interactions. Crater Glacier, which started forming after the 1980 eruption, is one of the world’s last expanding glaciers and provides a remarkable opportunity to characterize the expansion of a glacier in an area of significant thermal flux and investigate the formation of subglacial voids (glaciovolcanic caves). This talk will provide a comprehensive overview of post-eruption volcano-ice interactions in the volcanic crater with results from multidisciplinary (on-site) investigations performed over the last decade. These include repeated mapping of cave systems, climatologic measurements, and the use of remote sensing data. Although glaciovolcanic caves were initially expanding, latest investigations indicate shrinkage. These results provide evidence for a new phase of dome cooling and a reduction of fumarolic activity. We also observed changes in lava dome morphology and substantial subsidence. As revealed by LiDAR data, some areas of the new lava dome subsided more than 35 m from 2009-2019. In contrast, almost no elevation change was observed at the old dome. Our studies provide insight into the dynamics of an advancing glacier in times of global glacier retreat and into the largely understudied topic of glaciovolcanic cave systems. Furthermore, they underline the importance of studying post-eruption volcano-ice interactions.

All are welcome.