BPPTKG reported that the eruption at Merapi (on Java) continued during 1-7 March. Seismicity remained at high levels. The SW lava dome produced 123 lava avalanches that descended the S and SW flanks; one traveled S as far as 1 km down the upper part of the Boyong drainage and 122 traveled SW as far as 2 km down the upper part of the Bebeng drainage. A series of eight pyroclastic flows traveled as far as 2.6 km down the SW flank on 4 March; ashfall was reported at the Pasarbubar station, 800 m N, and minor ashfall was reported in Selo (6 km NNW) and Cepogo (4 km NE). Morphological changes to the SW lava dome identified in webcam images were due to continuing effusion and 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)