BPPTKG reported that the eruption at Merapi (on Java) continued during 31 May-6 June. Seismicity had decreased compared to the previous week. The SW lava dome produced 141 lava avalanches that traveled as far as 1.9 km down the upper part of the Bebeng drainage on the SW flank. Three pyroclastic flows also descended the Bebeng, traveling as far as 1 km. Morphological changes to the SW lava dome were due to continuing effusion and collapses of material. The volume of the SW dome was an estimated 2,335,200 cubic meters and the dome in the main crater was stable at an estimated 2,362,800 cubic meters based on a 6 June drone survey. The highest temperature of the SW dome was around 243 degrees Celsius, lower than the previous measurement. 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)