Based on reports from the VSI, the Darwin VAAC stated that during 15-21 February volcanic activity decreased at Merapi. According to the Meteorological and Geophysical Agency of Indonesia, during 11-18 February daily ash emissions rose up to ~150 m above the summit. The volcano remained at Alert Level 4, the highest level.

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: Darwin Volcanic Ash Advisory Centre (VAAC)