Report on Merapi (Indonesia) — 11 November-17 November 2020
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 11 November-17 November 2020
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2020. Report on Merapi (Indonesia). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 11 November-17 November 2020. 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 during 6-12 November sometimes dense white emissions from Merapi rose as high as 250 m above the summit. The report noted that the lava-dome volume was an estimated 200,000 cubic meters based on analyses of drone images captured on 3 November. Avalanches of material traveled 3 km down the WSW flank in the Putih/Sat drainage at 1450 on 8 November. Photos from 11 November showed no changed to the morphology of the lava dome in the summit crater. Electronic Distance Measurement (EDM) data continued to detect shortening between points in the NW at a deformation rate of 10 cm per day. Seismicity was higher than the previous week.
On 13 November BPPTKG noted that avalanches had been traveling 1-3 km down the N and NW flanks, indicating summit instability. Authorities recommended no activities within 5 km of the summit. BNPB reported that as of 15 November more than 1,800 residents from the surrounding districts of Boyolali, Magelang, Klaten, and Sleman had been relocated to shelters. Livestock was also being relocated, particularly from three villages within 7 km of the summit. PVMBG noted that less than a dozen rock avalanches were heard at observations posts during 15-17 November. The Alert Level remained at 3 (on a scale of 1-4).
Geologic Background. 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.
Sources: Balai Penyelidikan dan Pengembangan Teknologi Kebencanaan Geologi (BPPTKG), Badan Nacional Penanggulangan Bencana (BNPB), Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)