PVMBG reported that a phreatic eruption at Sirung was recorded at 1644 on 21 July. A white-and-gray ash plume rose 2 km above the summit and drifted N. The report noted that the event was preceded by an increase in tremor amplitude that lasted about 10 hours; no volcanic earthquakes indicating magma movement were recorded and tremor amplitude did not notably increase. The Alert Level was raised to 2 (on a scale of 1-4), with visitors and tourists prohibited within a 1.5 km radius of Sirung.

Geological Summary. Sirung volcano is located at the NE end of a 14-km-long line of volcanic centers that form a peninsula at the southern end of Pantar Island. The volcano is truncated by a 2-km-wide caldera whose floor often contains one or more small lakes. Much of the volcano is constructed of basaltic lava flows, and the Gunung Sirung lava dome forms the high point on the caldera's western rim. A number of phreatic eruptions have occurred from vents within the caldera during the 20th century. Forested Gunung Topaki, the high point of the volcanic chain, lies at the SW end and contains a symmetrical summit crater.

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