Report on Semeru (Indonesia) — 8 December-14 December 2021
Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 8 December-14 December 2021
Managing Editor: Sally Sennert.
Please cite this report as:
Global Volcanism Program, 2021. Report on Semeru (Indonesia) (Sennert, S, ed.). Weekly Volcanic Activity Report, 8 December-14 December 2021. Smithsonian Institution and US Geological Survey.
8.108°S, 112.922°E; summit elev. 3657 m
All times are local (unless otherwise noted)
PVMBG reported that lava avalanches from the end of the 700-m-long lava flow on Semeru’s SE flank descended 500 m during 7-8 December. Lava avalanches were detected by the seismic network almost daily during 9-14 December, though weather conditions prevented visual confirmation. During 9-11 December crater incandescence was visible and gray-white ash plumes rose 300-1,000 m above the summit. White plumes rose as high as 1 km above the summit during 12-14 December.
According to BNPB, the death toll from the 4 December collapse event rose to 48 by 13 December, 12 people were still missing, 21 were seriously injured, and 9,374 people were in 129 evacuation centers. The Alert Level remained at 2 (on a scale of 1-4), with a general exclusion zone of 1 km and extensions to 5 km in the SSE sector.
Geological Summary. Semeru, the highest volcano on Java, and one of its most active, lies at the southern end of a volcanic massif extending north to the Tengger caldera. The steep-sided volcano, also referred to as Mahameru (Great Mountain), rises above coastal plains to the south. Gunung Semeru was constructed south of the overlapping Ajek-ajek and Jambangan calderas. A line of lake-filled maars was constructed along a N-S trend cutting through the summit, and cinder cones and lava domes occupy the eastern and NE flanks. Summit topography is complicated by the shifting of craters from NW to SE. Frequent 19th and 20th century eruptions were dominated by small-to-moderate explosions from the summit crater, with occasional lava flows and larger explosive eruptions accompanied by pyroclastic flows that have reached the lower flanks of the volcano.