Mount Semeru erupts with pyroclastic flow, distance unknown due to fog

Lumajang, East Java - Mount Semeru, located on the border of Lumajang and Malang regencies in East Java, erupted with a pyroclastic flow (APG), its runout distance unknown due to fog on Wednesday afternoon.

“An eruption occurred at Mount Semeru at 11:22 WIB, but the ash column height could not be observed due to fog,” said Mount Semeru Observation Post officer Sigit Rian Alfian in a written report received in Lumajang.

The eruption was recorded on the seismogram with a maximum amplitude of 23 mm and duration of approximately 3 minutes 29 seconds.

“The eruption consisted of a pyroclastic flow with an unknown runout distance due to the mountain being shrouded in fog,” he added.

According to official data, Mount Semeru erupted seven times between 00:14 WIB and 11:22 WIB, with eruption heights ranging from 600 to 800 metres above the summit.

Residents must avoid activities within 500 metres of riverbanks along the Besuk Kobokan due to the risk of pyroclastic flow expansion and lahar flows extending up to 17 kilometres from the summit,” he said.

Additionally, residents must avoid activities within a 5-kilometre radius of the crater/summit due to the risk of rock ejections (incandescent material).

Residents are also urged to remain vigilant for potential pyroclastic flows, lava collapses, and lahars along river valleys originating from the summit of Mount Semeru.

“Particularly along the Besuk Kobokan, Besuk Bang, Besuk Kembar, and Besuk Sat rivers, as well as potential lahars in smaller tributaries of the Besuk Kobokan,” he added.