BPPTKG reported that at 0522 on 3 March an eruption at Merapi produced an ash plume that rose 6 km above the crater rim and pyroclastic flows that descended the SSE flank less than 2 km. The ash plume drifted mainly NE and caused ashfall within 10 km, particularly in areas to the N including Musuk and Cepogo Boyolali. Video of the event showed incandescent material being ejected above the summit and lightning in the ash cloud. The report noted that there were no clear precursors for the eruption. 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.

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