MONITORING AND MODELING ICE-ROCK AVALANCHES FROM ICE-CAPPED VOLCANOES: A CASE STUDY OF FREQUENT LARGE AVALANCHES ON ILIAMNA VOLCANO, ALASKA

Abstract

Iliamna is an andesitic stratovolcano of the Aleutian arc with regular gas and steam emissions and mantled by several large glaciers. Iliamna Volcano exhibits an unusual combination of frequent and large ice-rock avalanches in the order of 1 × 10⁶ m³ to 3 × 10⁷ m³ with recent return periods of 2–4 years. We have reconstructed an avalanche event record for the past 45 years that indicates Iliamna avalanches occur at higher frequency at a given magnitude than other mass failures in volcanic and alpine environments. Iliamna Volcano is thus an ideal site to study such mass failures and its relation to volcanic activity.