PVMBG reported that eruptive activity at Marapi (on Sumatra) was ongoing during 12-18 June. White gas-and-steam plumes rose 200-300 m above the summit and drifted S, SW, W, and NE during 12-13 and 16 June. A dense gray ash plume rose 500 m above the summit and drifted NW on 17 June. Emissions were not visible on the other days; eruptive events were recorded during 12-13 and 15-17 June, though no emissions were observed. 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.

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