The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that eruptive activity at Marapi (on Sumatra) continued during 21-27 May, characterized by occasional dense ash plumes. White plumes rose 100-200 m above the summit and drifted in multiple directions during 21-22 and 24 May. Eruptive events were recorded at 1227 on 23 May and at 1457 on 26 May, though weather conditions prevented visual confirmation. On 25 May white-and-brown plumes rose 100-250 m above the summit and drifted E and SE. At 0822 on 27 May a dense white-and-gray ash plume rose 1.2 km above the summit and drifted SE. The Alert Level remained at 2 (on a scale of 1-4) and the public was warned to stay 3 km away from the active crater.

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.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)