PVMBG reported that eruptive activity at Marapi was ongoing during 6-12 December, though foggy and raining weather conditions often prevented visual observations of the summit. White-and-gray ash plumes rose 400-500 m and drifted NE, E, and W on 6 December. Eruptive events were recorded by the seismic network at 1009 on 6 December and at 0141 on 7 December though no ash emissions were observed. On 11 December white-and-gray ash plumes rose 200-400 m above the summit and drifted E and S. At 0805 that same day a dense gray ash plume rose 400 m above the summit and drifted N. The Alert Level remained at 2 (on a scale of 1-4), and the public was warned to stay 3 km away from the summit 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)