BPPTKG reported that the eruption at Merapi continued during 9-15 November and seismicity remained at high levels. Cloudy often prevented clear visuals of the summit. A seismogram detected a pyroclastic flow at 0905 on 11 November that lasted 135 seconds; it descended 1 km down the Boyong drainage (SW), though webcam images were cloudy. A second pyroclastic flow occurred at 1208 on the same day, lasting 104 seconds and descending 1 km down the Boyong drainage (SW). On 12 November a lava avalanche traveled as far as 800 m down the SW flank. Two lava avalanches were observed descending the SW for 1.5 km on 15 November. The Alert Level remained at 3 (on a scale of 1-4), and the public was warned to stay 3-7 km away from the summit based on location.

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.

Source: Balai Penyelidikan dan Pengembangan Teknologi Kebencanaan Geologi (BPPTKG)