At 0553 on 11 March 2000, a significant explosion ejected thick black ash that rose 1,400 m above the summit. Explosions and ash emissions continued and increased in magnitude. At 0944 on the following day, a large explosion was heard more than 25 km away in the community of Bukittinggi. The explosion sent thick, black ash to a height of 3,000 m. Ashfall was reported ~350 km N of Marapi on the Lima Kaun District of Tanah Datar. Both major explosions were immediately preceded by shallow volcanic (B-type) earthquakes, while heightened seismicity, especially A- and B-type earthquakes, occurred up to a week before the explosions.

By 14 March explosions and ash emissions were continuing with decreased intensity. The gray-black plume rose 200 m above the crater rim. The following week seismicity increased notably with all earthquakes types increasing in number. During the [week of 28 March-3 April], black ash emissions continued to rise 100-200 m. Seismicity increased slightly compared to the previous week, but remained much lower than when the explosions initiated.

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: Dali Ahmad, Volcanological Survey of Indonesia (VSI), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/).