PVMBG reported that eruptive activity at Marapi (on Sumatra) was ongoing during 29 May-4 June. White gas-and-steam plumes rose 150-400 m above the summit and drifted in multiple directions during 29 May-1 June and on 3 June. An eruptive event at 1304 on 30 May produced a dense gray ash plume that rose 2 km and drifted NW. BNPB noted that a booming noise from the event was heard in areas as far as the Marapi Volcano Observation post in Bukittinggi (12 km NW). White-and-gray ash plumes rose 200-1,000 m above the summit and drifted S, SW, W, and NW on 2 June. The Alert Level remained at 3 (on a scale of 1-4), and the public was warned to stay 4.5 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.

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM), Badan Nacional Penanggulangan Bencana (BNPB)