Report on Merapi (Indonesia) — 15 August-21 August 2018
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 15 August-21 August 2018
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2018. Report on Merapi (Indonesia). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 15 August-21 August 2018. 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 seismicity at Merapi increased on 18 July, and again on 29 July. On 11 August a large earthquake was detected, and coupled with rumbling heard by Deles residents, possibly signaled new lava-dome effusion. Drone photos on 12 August showed a new lava dome growing within the fracture of the 2010 dome. By 18 August the new dome was 55 m long and 25 m wide, and about 5 m below the 2010 dome surface. The Alert Level remained at 2 (on a scale of 1-4), and resident 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.