Relocation of an observatory to the area near Tongkoko provided scientists with previously unavailable seismic data. During 7-14 October, four deep-volcanic events were recorded at Tongkoko. This is significant because the volcano has been in repose for almost 122 years. Tongkoko was at Alert Level 1 (on a scale of 1-4) (note: VSI later corrected Alert Level from 2).

Geological Summary. The eastern peninsula at the far NE end of Sulawesi near the city of Bitung is occupied by a volcanic complex consisting of two major edifices within a nature reserve. To the north is Tangkoko (also known as Tongkoko), with a large caldera (~3 x 1.5 km) elongated towards the SE from the highest rim point; the rim at the opposite end is more than 400 m lower. Eruptions occurred from the summit crater in the 17th century and in 1801, when the caldera also reportedly contained a cone surrounded by a lake. About 1.5 km down the outer E flank is the Batuangus (or Batu Angus) lava dome, formed in 1801, along with an adjacent vent (Baru Batuangus) that has been the source of all subsequent eruptions. The higher twin-peaked Duasudara (also Dua Suadara) stratovolcano is about 4.5 km SW of the Tangkoko summit. A NE-facing open crater appears to have a hummocky debris flow that reaches the base of the Tangkoko edifice.

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