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Report on Merapi (Indonesia) — 6 December-12 December 2023


Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 6 December-12 December 2023
Managing Editor: Sally Sennert.

Please cite this report as:

Global Volcanism Program, 2023. Report on Merapi (Indonesia) (Sennert, S, ed.). Weekly Volcanic Activity Report, 6 December-12 December 2023. Smithsonian Institution and US Geological Survey.

Weekly Report (6 December-12 December 2023)



7.54°S, 110.446°E; summit elev. 2910 m

All times are local (unless otherwise noted)

BPPTKG reported that the eruption at Merapi (on Java) continued during 1-8 December. Two pyroclastic flows traveled S as far as 1.3 km down the upper part of the Boyong drainage and four pyroclastic flows traveled SW as far as 3 km down the upper parts of the Bebeng and Krasak drainages during 1-7 December. Minor ashfall occurred in the Sawangan District (15 km W), Magelang, and the Selo District (5 km NNE), Boyolali. The SW lava dome produced a total of 192 lava avalanches; 23 traveled as far as 1.5 km down the Boyong drainage and 169 traveled as far as 1.7 km down the Bebeng drainage. According to BNPB several dark gray pyroclastic flows were detected by the seismic network starting at 1449 on 8 December and traveled as far as 3.5 km down the Krasak drainage on the SW flank. Ash mixed with rain fell in Krinjing (5 km WNW) and Paten (9 km WNW) villages, Dukun District in the Magelang Regency, as well as in the Stabelan (4 km NW), Klakah (4 km NW), and Tlogolele (5 km NW) villages in the Selo District, Boyolali Regency. BPPTKG noted that minor morphological changes to the SW lava dome were identified in webcam images due to continuing lava effusion and collapses of material. Seismicity remained at high levels during the week. 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.

Sources: Balai Penyelidikan dan Pengembangan Teknologi Kebencanaan Geologi (BPPTKG), Badan Nacional Penanggulangan Bencana (BNPB)