Report on Semeru (Indonesia) — 22 July-28 July 2015
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 22 July-28 July 2015
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2015. Report on Semeru (Indonesia). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 22 July-28 July 2015. 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 both white plumes and gray to brownish-gray plumes from Semeru were observed rising as high as 600 m above the crater and drifting N, NW, W, and SW during 1 April-13 July; inclement weather sometimes prevented observations. Ashfall was reported in Sawur and surrounding areas in April, and incandescent avalanches that traveled as far as 1 km were observed in May. Seismicity was dominated by explosions and emission signals. The Alert Level remained at 2 (on a scale from 1-4); visitors and residents were warned to avoid the SE flank within 4 km of the crater.
Geologic Background. 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.