The summit of the volcano was covered by clouds during 12-18 March, but the seismic record showed increasing activity. Explosion and avalanche earthquakes still dominated seismicity and increased over the past week. There were 349 explosion earthquakes, an increase over the 303 detected during 6-12 March. The count of explosion earthquakes decreased to 259 the week of 19-26 March. Semeru is at hazard level 2 (on a scale of 1-4).

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.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)