Insights into the recurrent energetic eruptions that drive Awu, among the deadliest volcanoes on Earth

Abstract

The little-known Awu volcano (Sangihe Islands, Indonesia) is among the deadliest, with a cumulative death toll of 11 048. In less than 4 centuries, 18 eruptions were recorded, including two VEI 4 and three VEI 3 eruptions with worldwide impacts. The regional geodynamic setting is controlled by a divergent-double-subduction collision and an arc-arc collision. In that context, the slab stalls in the mantle, undergoes an increase in temperature, and becomes prone to melting, a process that sustained the magmatic supply. Awu also has the particularity of hosting alternatively and simultaneously a lava dome and a crater lake throughout its activity. The lava dome passively erupted through the crater lake and induced strong water evaporation from the crater. A conduit plug associated with this dome emplacement subsequently channeled the gas emission to the crater wall. However, with the lava dome cooling, the high annual rainfall eventually reconstituted the crater lake and created a hazardous situation on Awu. Indeed with a new magma injection, rapid pressure buildup may pulverize the conduit plug and the lava dome, allowing lake water injection and subsequent explosive water-magma interaction. The past vigorous eruptions are likely induced by these phenomena, possible scenarios for future events.