An Overview of the Large-Magnitude (VEI 4) Eruption of Merapi in 2010

Abstract

The VEI 4 eruption in 2010 was the worst volcanic disaster at Merapi in 80 years.The unusual size and dynamics of the eruption, the rapid acceleration of events and the large number of evacuees posed significant challenges for the management of the volcanic crisis and post-eruption recovery. The first indications of Merapi’s reawakening were observed in the seismic monitoring record about one year before the eruption. The eruption commenced on 26 October 2010, with initial explosions and associated pyroclastic density currents (PDCs) directed towards the south flank of Merapi. Subsequently, the intensity of the eruption accelerated with rapid lava dome growth and increasing PDC runout, culminating in a climactic eruption phase on 5 November, where blast-like, high-energy PDCs destroyed areas on Merapi’s south flank and PDCs reached ~16 km in the Gendol valley. After 5 November, the eruption waned, leading to reductions of the exclusion zone from mid-November 2010 and successive lowering of the alert level from early December 2010. The 2010 eruption was fed by basaltic andesite magma similar to other recent Merapi eruptions, but was driven by a larger than normal influx of deep, volatile-rich magma that replenished the shallower magma system within the carbonate-dominated upper crust beneath Merapi at relatively short timescales. During and after the eruption, lahars swept down almost all major valleys, causing considerably larger impact than after previous eruptions. As a result of the eruption, nearly 400,000 people were displaced from their homes and accommodated in temporary or permanent residences. Tourist activities and sand quarrying of PDC and lahar deposits facilitated post-eruption recovery. Mitigation measures, including strengthening of the volcano monitoring system, establishment of a disaster risk reduction forum, strengthening of community capacity, and preparation of contingency plans for local governments based on hazard scenarios, were all part of the disaster risk reduction strategy that saved many lives during the 2010 eruption crisis.