BPPTKG reported that during 19-25 June sometimes dense white emissions from Merapi rose as high as 600 m above the summit. The report noted that the lava-dome volume was an estimated 200,000 cubic meters on 13 June based on analyses of drone images. The morphology of the summit crater area had slightly changed after the 21 June eruption. Based on photos taken from the Ngepos Post about 19,000 cubic meters had been removed from the SW part of the summit, likely near or part of the crater rim. The Alert Level remained at 2 (on a scale of 1-4), and residents were warned to stay outside of the 3-km exclusion zone.

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)