During 12-18 July, lava flows at Merapi were observed and reached a maximum distance of 2 km SE along the Gendol River. Gas plumes were also observed daily and reached heights of 1 km above the crater (12,800 ft a.s.l.). On 17 July, CVGHM reported that the Alert Level was lowered one level to 3 (on a scale of 1-4) in all remaining areas previously at Alert Level 4 (S slopes). Pyroclastic flows were not observed during the reporting period.

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: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)