BPPTKG reported that during 13-23 November sometimes dense white emissions from Merapi rose as high as 200 m above the summit. Avalanches of material traveled down the flanks, as far as 2 km in the Lamat drainage (W flank) at 0615 on 14 November. A comparison of photos taken on 11 and 19 November showed morphology changes in the summit area from a collapse of part of the 2018 dome and rockfalls from parts of the crater rim. Seismicity was higher than the previous week. A notable rockfall from the inner N crater rim was recorded by the webcam at 0650 on 22 November. Electronic Distance Measurement (EDM) data continued to measure a distance shortening between points in the NW at a deformation rate of 9 cm per day during 13-19 November, though on 23 November the rate was 11 cm per day. The Alert Level remained at 3 (on a scale of 1-4).

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.

Sources: Balai Penyelidikan dan Pengembangan Teknologi Kebencanaan Geologi (BPPTKG), Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)