Report on Merapi (Indonesia) — 3 February-9 February 2021
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
3 February-9 February 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, 3 February-9 February 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 2021 lava dome continued to grow just below Merapi’s SW rim during 29 January-4 February. One pyroclastic flow descended the SW flank as far as 600 m. The 2021 lava dome volume was an estimated 117,400 cubic meters on 4 February, with a growth rate of about 12,600 cubic meters per day. A comparison of photos taken on 21 January and 4 February showed that the morphological changes in the summit area were attributed to the growth of the 2021 lava dome as well as from a new dome slowly growing in the summit crater. Electronic Distance Measurement (EDM) data showed no notable deformation. Seismic activity was lower than the previous week. BNPB noted that a total of 537 people remained evacuated (190 people from Sleman Regency and 347 from Klaten) as of 3 February. The Alert Level remained at 3 (on a scale of 1-4), and the public were 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.