The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that on 19 September the seismic network at Lewotobi Laki-laki recorded an increase in the number of low-frequency earthquakes, followed by an eruption at 1432 that produced ash plumes that rose 500-1,000 m above the summit. The Alert Level was raised to 4 (the highest level on a scale of 1-4) at 2100 and the exclusion zone was increased to 6 km from the center of Laki-laki and 7 km in a semicircle clockwise from the SW to the NE. At 2158 eruptive activity became continuous and remained continuous at least through 2229, with ash plumes rising 800-1,500 m above the summit and drifting SW. At 2246 an ash plume rose around 6 km above the summit and drifted W and SW and a webcam at that same time showed incandescent material on the upper flanks. Incandescent material being ejected straight up above the summit and falling onto the upper flanks was visible in a 2254 webcam image. Ash plumes rose 3 km above the summit and drifted W and SW at 2307, at 2327, and at 2341. Ash-and-gas emissions were continuous for most of 20 September. Multiple eruptive events produced ash plumes that rose as high as 3 km above the summit and drifted NW, W, and SW. Summit incandescence was visible in a few of the webcam images. According to a news report three flights using the Komodo International Airport, around 300 km W, were canceled on 20 September and two were rescheduled for the next day. Multiple eruptive events were recorded on 21 September. Ash plumes again rose as high as 3 km above the summit and drifted N, NW, W, and SW. Ash plumes during 22-23 September rose 600-2,000 m above the summit and drifted NW, W, and SW. Minor incandescence at the summit was visible in a webcam image at 1915 on 22 September.

Geological Summary. The Lewotobi edifice in eastern Flores Island is composed of the two adjacent Lewotobi Laki-laki and Lewotobi Perempuan stratovolcanoes (the "husband and wife"). Their summits are less than 2 km apart along a NW-SE line. The conical Laki-laki to the NW has been frequently active during the 19th and 20th centuries, while the taller and broader Perempuan has had observed eruptions in 1921 and 1935. Small lava domes have grown during the 20th century in both of the summit craters, which are open to the north. A prominent cone, Iliwokar, occurs on the E flank of Perampuan.

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM), Antara News