The volume of the summit lava dome has remained constant since January at ~6.4 x 10⁶ m³. Two active solfataric vents fed a plume that rose to as much as 500 m above the summit. May 1989 temperatures at the vents were [813°C] (Gendol) and [575°C] (Woro). The number of earthquakes recorded . . . near Merapi [is shown in table 3]. No lahars occurred in February, although rainfall was increasing on the volcano's NW sector (while decreasing on the SW sector). An increased lahar alert notification has been released, especially for areas along SW-sector river valleys (K. Putih, K. Blongkeng, K. Krasak).

Geological Summary. Merapi, one of Indonesia's most active volcanoes, lies in one of the world's most densely populated areas and dominates the landscape immediately north of the major city of Yogyakarta. It is the youngest and southernmost of a volcanic chain extending NNW to Ungaran volcano. Growth of Old Merapi during the Pleistocene ended with major edifice collapse perhaps about 2,000 years ago, leaving a large arcuate scarp cutting the eroded older Batulawang volcano. Subsequent growth of the steep-sided Young Merapi edifice, its upper part unvegetated due to frequent activity, began SW of the earlier collapse scarp. Pyroclastic flows and lahars accompanying growth and collapse of the steep-sided active summit lava dome have devastated cultivated lands on the western-to-southern flanks and caused many fatalities.

Information Contacts: VSI.