BPPTKG reported that the eruption at Merapi (on Java) continued during 12-18 January. Seismicity remained at high levels. The SW lava dome produced a total of 88 lava avalanches that descended the S and SW flanks; five traveled S as far as 1.2 km down the upper part of the Boyong drainage and 83 traveled SW as far as 1.6 km down the upper part of the Bebeng drainage. Four pyroclastic flows descended the Bebeng drainage as far as 2.4 km. Morphological changes to the SW lava dome identified in webcam images were due to continuing collapses of material. The Alert Level remained at 3 (on a scale of 1-4), and the public was warned to stay 3-7 km away from the summit, based on location.

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.

Source: Balai Penyelidikan dan Pengembangan Teknologi Kebencanaan Geologi (BPPTKG)