Press reports describing a tephra eruption of Marapi on 30 April were incorrect. About 300 mm of rainfall remobilized an old lahar and other volcanic material on Marapi's N and E flanks, producing several landslides. The largest began at 2,400 m altitude on 30 April, and traveled as much as 20 km downslope to ~70 m altitude, leaving a deposit 20-150 m wide and 1-3 m thick. Eighty people were killed, five villages were damaged, and several acres of farmland were destroyed.

A VSI team inspected Marapi's crater on 8 May. Fumaroles emitted thin white vapor columns that had a slight sulfur odor and a temperature of 90-104°C.

Geological Summary. Gunung Marapi, not to be confused with the better-known Merapi volcano on Java, is Sumatra's most active volcano. This massive complex stratovolcano rises 2,000 m above the Bukittinggi Plain in the Padang Highlands. A broad summit contains multiple partially overlapping summit craters constructed within the small 1.4-km-wide Bancah caldera. The summit craters are located along an ENE-WSW line, with volcanism migrating to the west. More than 50 eruptions, typically consisting of small-to-moderate explosive activity, have been recorded since the end of the 18th century; no lava flows outside the summit craters have been reported in historical time.

Information Contacts: F. Suparban Mitrohartono and A. Sudradjat, VSI.