Report on Merapi (Indonesia) — 26 May-1 June 2021
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
26 May-1 June 2021
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2021. Report on Merapi (Indonesia). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 26 May-1 June 2021. Smithsonian Institution and US Geological Survey.
7.54°S, 110.446°E; summit elev. 2910 m
All times are local (unless otherwise noted)
BPPTKG reported that the lava dome just below Merapi’s SW rim and the lava dome in the summit crater both continued to be active during 21-27 May. The SW rim lava-dome volume was an estimated 1.265 million cubic meters, with a growth rate of about 11,600 cubic meters per day, and continued to shed material down the flank. A total of 15 pyroclastic flows traveled a maximum of 2 km down the SW flank. Incandescent avalanches, recorded 70 times, traveled as far as 1.8 km down the SW flank and once went 800 m SE. The summit lava dome had not changed since observations the previous week. The Alert Level remained at 3 (on a scale of 1-4), and the public was warned to stay 5 km away from the summit.
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.