Report on Semeru (Indonesia) — 8 April-14 April 2015
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 8 April-14 April 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, 8 April-14 April 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 during 1 January-10 April white and gray plumes were observed rising above Semeru even though inclement weather sometimes prevented visual observations. During January white plumes and nine instances of grayish-white plumes rose 200-500 m above the crater. Seven incandescent avalanches from a lava-flow front traveled at most 300 m down the flank. In February white plumes and 19 instances of grayish-white plumes rose 200-600 m above the crater. Eruption sounds were reported five times. In March white plumes and 21 instances of grayish-white plumes rose 200-500 m above the crater. Nine explosions were heard. During 1-10 April there were 18 instances of grayish-white emissions. Seismicity from 1 January through 10 April fluctuated, and was dominated by emission and explosion signals. The Alert Level remained at 2 (on a scale of 1-4) and the public was reminded not to approach the crater within a 4-km radius.
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.