Strong eruption at Merapi volcano, ashfall reported up to 45 km (28 miles) away, Indonesia

Indonesia's Mount Merapi has erupted twice on Sunday, June 21, 2020, ejecting ash up to 6 000 m (20 000 feet) into the sky, according to the Center for Volcanology and Geological Hazard Mitigation (PVMBG). The first explosion occurred at 02:13 UTC (09:13 LT) and lasted for more than five minutes, while the second one took place minutes later at 02:27 UTC (09:13 LT), with a duration of about 2 minutes.

As of 09:16 UTC (16:16 LT) on June 21, the Aviation Color Code is Yellow, which indicates that volcanic activity has decreased significantly but continues to be monitored closely for a possible increase.

The direction of the wind to the west caused ash to fall in the regencies of Magelang and Kulonprogo, as said in a statement issued by the Yogyakarta Geological Disaster Technology Research and Development Center (BPPTKG).

"Both eruptions were recorded on a seismogram with an amplitude of 75 mm," it wrote. The column height reached more than 6 000 m (20 000 feet) from the summit.

The Magelang Regency Disaster Management Agency (BPBD) reports that light and heavy volcanic ash rain showered 39 villages in 8 sub-districts in the Magelang Regency: Srumbung (heavy), Dukun (light), Sawangan (light), Salam (light), Muntilan (light), Ngluwar (light), Mungkid (light), and Borobudur (light).

Indonesia’s Badan Nasional Penanggulangan Bencana (BNPB) reports that thin ash is distributed in several areas around the slopes of Mount Merapi (Tlogo Lele, Boyolali Regency, Central Java). Whereas in other places, residents in the Turi, Pakem and Yogyakarta cities do not see volcanic ash.

The farthest ashfall was reported in the Grimulyo District area, Kulon Progo, which is about 45 km (28 miles) from the volcano's peak.

BPPTKG noted that prior to the explosive eruption, there has been an increase in seismicity since June 8. There were 80 volcanic-tectonic earthquakes between that day up to June 20.

The agency warned people to avoid the area within a radius of 3 km (1.9 miles) from Merapi's peak.

Mount Merapi is one of Indonesia's most active volcanoes. In 2010, an eruption killed more than 300 and forced almost 400 000 to evacuate.

Image credit: BPPTKG

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 the 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. 

Subsequently, the growth of the steep-sided Young Merapi edifice, its upper part unvegetated due to frequent eruptive 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 during historical time. (GVP)

Featured image credit: BPPTKG