Balai Penyelidikan dan Pengembangan Teknologi Kegunungapian (BPPTK) reported that at 0415 on 22 July a booming sound from Merapi was followed by a rising plume observed from multiple observation posts. Ashfall was reported in areas S, including Kaliurang and Balerante. The Alert Level remained at 1 (on a scale from 0-4).

According to news articles, the eruption lasted until about 0530, and generated a dense black plume that rose 1 km. A booming sound was heard 30 km away. Ashfall affected the district of Deles, Tlogowatu, Kemalang, Balerante, Klaten, and Jawa Tengah. Hundreds of residents evacuated but returned to their homes later that day.

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 Kegunungapian (BPPTK), Bernama, Associated Press