Report on Merapi (Indonesia) — 14 July-20 July 2021
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
14 July-20 July 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, 14 July-20 July 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 remained active during 9-15 July. The SW rim lava-dome volume was an estimated 1.83 million cubic meters and continued to shed material down the flank. One pyroclastic flow traveled 1.1 km down the SW flank and as far as 1.5 km SE. Avalanches traveled a maximum of 1.5 km SE (58 times), 2 km SW (98 times), 1 km W (one time), and 700 m NW (three times). The volume of the summit lava dome was 2.796 million cubic meters. 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.