Report on Merapi (Indonesia) — 4 November-10 November 2020
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
4 November-10 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, 4 November-10 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)
PVMBG and BPPTKG raised the Alert Level for Merapi to 3 (on a scale of 1-4) on 5 November because of increasing evidence of a potential eruption. The report noted that the number of earthquakes began increasing after the 21 June explosive eruption; seismicity intensified in October and continued an upward trend. Electronic Distance Measurement (EDM) data indicated a distance shortening of 4 cm between points in the NW just after the 21 June event, and then continued showing deformation at a rate of 3 mm per day through September. The rate increased to 9 cm per day in late October and reached 11 cm per day on 4 November. The seismicity and deformation rates were higher than the rates leading up to the extrusion of lava domes on 26 April 2006, but remained lower than the 2010 eruption precursory conditions. No morphological changes were visible; the lava-dome volume was an estimated 200,000 cubic meters on 3 November based on analyses of drone images. BPPTKG alerted 12 villages in hazardous areas spread across Yogyakarta and Central Java Province, and recommended that mining in local drainages and tourism around Merapi should cease.
BNPB reported that after the Alert Level was raised 607 vulnerable people (children for example) were evacuated from Krinjing, Paten, and Ngargomulyo villages in Dukun District, Magelang Regency, and emergency supplies were sent to multiple susceptible communities.
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.
Sources: Balai Penyelidikan dan Pengembangan Teknologi Kebencanaan Geologi (BPPTKG), Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM), Badan Nacional Penanggulangan Bencana (BNPB)