During 9-15 December higher-than-normal seismicity at Guntur led VSI to raise the Alert Level to 2 (on a scale of 1-4). Visual observations of the summit did not reveal any surface changes or ash plumes. In comparison to the previous week, the number of shallow volcanic and tectonic earthquakes increased, while deep volcanic earthquakes decreased. Seismicity remained higher than normal during 16-22 December, but fewer earthquakes occurred than during the previous week. The Alert Level remained at 2.

Geological Summary. Guntur is a complex of several overlapping stratovolcanoes about 10 km NW of the city of Garut in western Java. Young lava flows, the most recent of which was erupted in 1840, are visible on the flanks of the erosionally unmodified Gunung Guntur, which rises about 1550 m above the plain of Garut. It is one of a group of younger cones constructed to the SW of an older eroded group of volcanoes at the NE end of the complex. Guntur, whose name means "thunder," is the only center with recorded activity, with eruptions since the late-17th century. Although it produced frequent explosive eruptions in the 19th century, it has not erupted since.

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