On 16 August the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported increased activity at Lewotobi Laki-laki after the 9 August eruption. At 1405 and 1747 on 13 August a white, gray, and brown ash plume and a gray-to-brown ash plume, respectively, rose around 200 m above the summit and drifted W and SW. Seismic data during 10-16 August, specifically an increase in non-harmonic tremor signals, indicated increased activity at shallow depths. In addition, deformation data indicated inflation. At 0800 on 16 August the Alert Level was raised to 4 (on a scale of 1-4) and increased the exclusion zone to a radius of 6 km from the center of Laki-laki and 7 km in a semicircle clockwise from the SW to the NE. At 1830 on 17 August a dense gray ash plume rose 1 km above the summit and drifted SW.

Activity escalated on 18 August with multiple ash plumes observed through the day. During 0038-0221 dense gray ash plumes rose at least 8 km above the summit and drifted W and NW. Webcam images from 0040 and 0222 showed incandescent material on the upper flanks and ash plumes rising from the summit and from areas along the down-flank margins of the ejected material. Ash plumes continued to be produced for almost another hour, though at 0723 the ash plumes were lower, rising 3.5 km above the summit and drifting W and NW. Dense gray ash plumes recorded at 0834, 0857, and 0911 rose 3.5-4 km above the summit and drifted W and NW. Dense gray ash plumes in the afternoon, at 1622 and 1651, rose 800 m above the summit and drifted S and SW. At 1721 a dense gray ash plume rose at least 6 km above the summit and drifted W and NW. A white-and-gray ash plume at 2008 rose 500 m above the summit and drifted N and NE; a webcam image a minute later showed minor crater incandescence. According to a news report a half a dozen flights in and out of Maumere (61 km W), Ende (125 km WSW), and Bajawa (200 km W) were canceled due to ash in the air.

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