PVMBG reports that seismicity significantly increased on 8 June, particularly volcanic and shallow-volcanic earthquakes; 12 volcanic earthquakes were recorded on 22 June (previously, 1-5 events per day had been recorded), and there were 11 shallow volcanic earthquakes on 23 June (previously, 1-8 events per day had been recorded). On 24 June the Alert Level was raised to 2 (on a scale of 1-4). However, observers at the Colo Volcano Observation Post in the Wakai village did not see plumes during April-23 June. Residents and tourists were warned not to approach the volcano within a radius of 1.5 km.

Geological Summary. Colo volcano forms the isolated small island of Una Una in the middle of the Gulf of Tomini in northern Sulawesi. The broad, low volcano contains a 2-km-wide caldera with a small central cone. Three eruptions have been recorded since the late 1800's, but two of those caused widespread damage over the island. The last eruption, in 1983, produced pyroclastic flows that swept over most of the island shortly after all residents had been evacuated.

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