The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that eruptive activity continued at Lewotobi Laki-laki during 16-31 December, though seismic data indicated that the activity was decreasing. White-and-gray ash plumes that were sometimes dense rose as high as 2 km above the summit and drifted NE, N, and NW on 18, 20, and 22 December. A webcam image at 1902 on 20 December showed incandescence reflected in the plume above the summit. Incandescence at the crater was visible in a webcam image from 2245 on 22 December. White plumes rose as high as 1 km above the summit and drifted in multiple directions on the other days. During 16-23 December the seismic network recorded an increase in gas emission signals but a decrease in several other types of signals including the number of earthquakes indicating eruptive activity, harmonic tremor, tornillo events, low-frequency earthquakes, both shallow and deep volcanic earthquakes, and both the amplitude and occurrence of tremor. Weak rumbling sounds were heard at the observation post. At 1000 on 24 December the Alert Level was lowered to 3 (on a scale of 1-4) and the public was warned to stay 5 km away from the center of Laki-laki and 6 km in a semicircle counterclockwise from the NE to the SW.

On 24 and 31 December eruptive events were detected but not visually confirmed. Two dense gray ash plumes rose 1.5-2 km above the crater rim and drifted NE on 28 December. On 31 December weak rumbling was heard at the observation post and crater incandescence at the summit was visible. White plumes rose as high as 1 km above the crater rim and drifted in various directions on the other days during 24-31 December.

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.

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