Ash emission continued at an average rate of once every 56 minutes in November and December. Ash columns typically rose 500-700 m above the crater rim. Some clouds were less ash-rich, as indicated by a grayish color. Incandescent lava fragments were sometimes visible at night. Strombolian-type eruptions have accompanied the formation of the lava dome since extrusion began in 1967.

Lava avalanches from the dome have usually been contained at about 3 km altitude on the S flank of the volcano, in the upper reaches of the Kembar River, but one traveled farther down the river valley in early December. Before this year's monsoon rains VSI has alerted local authorities to the S and SE of the danger of lahars along the Kembar, Kobokan, Rejali, Sat, and Glidil Rivers.

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.

Information Contacts: A. Sudradjat and L. Pardyanto, VSI.