PVMBG reported seismic and visual monitoring of Sangeang Api during 1-17 June. During clear conditions, incandescence at the summit and white-and-gray plumes (100-1,500 m above the summit) were visible. On 1 June seismicity dramatically decreased, and as of 17 June was still declining. The Alert Level was reduced from 3 to 2 (on a scale of 1-4) on 17 June.

Geological Summary. Sangeang Api volcano, one of the most active in the Lesser Sunda Islands, forms a small 13-km-wide island off the NE coast of Sumbawa Island. Two large trachybasaltic-to-tranchyandesitic volcanic cones, Doro Api and Doro Mantoi, were constructed in the center and on the eastern rim, respectively, of an older, largely obscured caldera. Flank vents occur on the south side of Doro Mantoi and near the northern coast. Intermittent eruptions have been recorded since 1512, most of them during in the 20th century.

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