YOGYAKARTA: Indonesia’s most active volcano erupted on Monday with its biggest lava flow in months, sending a river of lava and searing gas clouds flowing 3.5 kilometres down its slopes on the densely populated island of Java.

The rumbling sound could be heard several kilometres away as Mount Merapi erupted, sending hot ash 600 metres (nearly 2,000 feet) into the sky. Ash blanketed nearby towns, but long-established evacuation orders are in place near the volcano, and no casualties were reported.

It was Merapi's biggest lava flow since authorities raised its danger level last November, said Hanik Humaida, the head of Yogyakartas Volcanology and Geological Hazard Mitigation Centre.

She said the lava dome just below Merapis southwest rim and the lava dome in the crater both have been active since the end of July. The southwest rim dome volume was estimated at 1.8 million cubic metres (66.9 million cubic feet) and about 3 metre (9.8 feet) tall before partially collapsing on Monday morning, sending pyroclastic flows traveled fast down the southwest flank at least twice.

Smaller pyroclastic flows of searing gas and lava traveled up to 1.5 kilometres southwest at least twice more during the day.

The 2,968-meter (9,737-foot) peak is near Yogyakarta, an ancient city of several hundred thousand people embedded in a large metro area on the island of Java. The city is a centre of Javanese culture and a seat of royal dynasties going back centuries.

Merapi's alert status has been at the second highest of four levels since it began erupting last November, and Indonesia’s Volcanology and Geological Hazard Mitigation Centre has not raised it despite the past week’s increased volcanic activity. The four levels describe eruption activity as normal, minor, moderate or major.

Published in Dawn, August 17th, 2021