Hydrothermal alteration and the stability of volcanic flanks

Double, double toil and trouble; Fire burn, and cauldron bubble: The influence of hydrothermal alteration on the stability of a volcano

Hydrothermal alteration is near-ubiquitous at volcanoes worldwide and is thought to promote volcano instability and flank collapse. However, hydrothermal alteration can manifest as the dissolution/partial replacement of primary minerals within the rock, leading to an increase in porosity, or the precipitation of minerals within void space within the rock, leading to a decrease in porosity. In this seminar, we will explore what these end-member types of alteration do to the physical and mechanical properties of volcanic rock, and the stability of a volcanic structure. Using a combination of laboratory measurements and modelling, we reach the conclusion that porosity-decreasing alteration and porosity-increasing alteration can both promote volcano instability and collapse, but by different mechanisms. You'll have to attend the seminar to find out how and why! The take-home message is that hydrothermal alteration is never good news for a volcano and should therefore be monitored at volcanoes worldwide and incorporated into volcanic hazard assessments.

Speaker : Prof Michael J. Heap, Strasbourg University