Report on Merapi (Indonesia) — 30 January-5 February 2019
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 30 January-5 February 2019
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2019. Report on Merapi (Indonesia). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 30 January-5 February 2019. Smithsonian Institution and US Geological Survey.
7.54°S, 110.446°E; summit elev. 2910 m
All times are local (unless otherwise noted)
PVMBG reported that during 25-31 January the volume of the lava dome in Merapi’s summit crater was 461,000 cubic meters, relatively unchanged from the previous week. During 0000-2000 on 29 January as many as nine incandescent rockfall events were recorded, with material traveling 200-700 m SE in the Gendol River drainage. Three pyroclastic flows, recorded at 2017, 2053, and 2141, traveled 1.1-1.4 km down the Gendol drainage, and produced minor ashfall in areas E including Boyolali (17 km E), Mriyan (5 km E), and Mojosongo (44 km E). The Alert Level remained at 2 (on a scale of 1-4), and residents were warned to remain outside of the 3-km exclusion zone.
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 2000 years ago, leaving a large arcuate scarp cutting the eroded older Batulawang volcano. Subsequently growth of the steep-sided Young Merapi edifice, its upper part unvegetated due to frequent eruptive 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 during historical time.