PVMBG reported four explosions at Marapi on 4 June, each lasting less than one minute. The explosions occurred at 1001, 1011, 1256, and 1550, and produced dense ash-and-steam plumes that rose 300 m, at least 700 m, 200 m, and 250 m above the crater, respectively. The plumes drifted E. Ejected bombs were deposited around the crater. Seismicity increased after the explosions. Minor ashfall was reported in the Pariangan District (8 km SSE), Tanah Datar Regency. The Alert Level remained at 2 (on a scale of 1-4). Residents and visitors were advised not to enter an area within 3 km of the summit.

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)