PVMBG reported that eruptive activity at Lewotobi’s Laki-laki volcano increased during 26 May-9 June. Eruptive activity increased daily, and ash-and-steam plumes became taller, rising 100-900 m above the summit on average and drifting in multiple directions; dense ash emissions rose 1-1.1 km above them summit on 5 and 9 June. The number of volcanic earthquakes as well as earthquake signals indicating eruptive events and avalanches significantly increased. PVMBG noted that there was also a significant increase in other types of seismic signals, though those increases were unrelated to the eruption; repairs and changes to the seismic network resulted in better detection of seismic signals. Incandescence at the summit was visible in a 5 June webcam image, and Strombolian activity was periodically visible on 9 June. At 0900 on 10 June the Alert Level was raised to 3 (the second lowest level on a scale of 1-4) and the public was warned to stay outside of the exclusion zone, defined as a 3-km radius around Laki-laki crater, 4 km to the NNE, and 5 km on the NE flanks. Strombolian activity continued on 10 June and several ash emissions rose 600-1,000 m above the summit. Gray ash emissions rose 300-600 m above the summit and drifted SW and W on 11 June.

The lava flows on the NE flank advanced 20 m during 29 February-9 April to a total length of 4.34 km; the advancement was due to gravitational forces and not eruptive activity, and no additional advancement had been recorded since.

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)