PVMBG reported that a relatively high number of deep volcanic earthquakes were recorded at Merapi during 30 December-5 January. The seismic network recorded a pyroclastic flow that began at 2036 on 4 January and lasted for one minute and 45 seconds. The event was not visually observed due to foggy weather conditions. Minor ashfall was reported in Cepogo (4 km NE) and Boyolali (16 km E). The Alert Level remained at 2 (on a scale of 1-4), and residents were warned to stay outside of the 3-km exclusion zone.

Geological Summary. Merapi, one of Indonesia's most active volcanoes, lies in one of the world's most densely populated areas and dominates the landscape immediately north of the major city of Yogyakarta. It is the youngest and southernmost of a volcanic chain extending NNW to Ungaran volcano. Growth of Old Merapi during the Pleistocene ended with major edifice collapse perhaps about 2,000 years ago, leaving a large arcuate scarp cutting the eroded older Batulawang volcano. Subsequent growth of the steep-sided Young Merapi edifice, its upper part unvegetated due to frequent activity, began SW of the earlier collapse scarp. Pyroclastic flows and lahars accompanying growth and collapse of the steep-sided active summit lava dome have devastated cultivated lands on the western-to-southern flanks and caused many fatalities.

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM), Kompas.com, Balai Penyelidikan dan Pengembangan Teknologi Kebencanaan Geologi (BPPTKG)