High-level eruption at Semeru volcano, ash to 15.2 km (50 000 feet) a.s.l., Indonesia


A high-level eruption took place at Semeru volcano, East Java, Indonesia at around 08:20 UTC on Saturday, December 4, 2021. The Aviation Color Code was raised to Red. The eruption comes just two days after a high-level eruption at Sangay volcano, Ecuador.1

At 09:20 UTC, the ash cloud was estimated rising up to 15.2 km (50 000 feet) above sea level, according to the Darwin VAAC VA Advisory released at 09:48 UTC.2

"Volcanic ash observed on latest RGB and Visible satellite imagery moving SW of the summit. Ash seems to have detached from the summit and continues to move SW. IR temperature of -85 °C (-121 °F) obtained correspond to 15.2 km (50 000 feet) a.s.l."

Ash has completely blocked out the Sun over the area. Some users on social media are reporting fast-flowing lahars.

Authorities reported extensive damage to buildings, cars, roads, and farms.

The deputy chief of Lumajang district, Indah Masdar, said Saturday one person had died and 41 people had suffered burn injuries.3

The death toll rose to 13 and the number of injured to 57 on Sunday, December 5, disaster officials said.4

The eruption caught locals by surprise and send thousands of them fleeing its path of destruction.

Homes and livestock in at least 11 villages of Lumajang district were coated in volcanic ash.

At least seven people remain missing after the eruption, including two who authorities believe are still alive, Lumajang Public Order Agency spokesman Adi Hendro told AFP.5

"There were signs they are still alive as there were lights maybe from their cellphones," he said. "But we cannot go there as the ground is still very hot."

Lava mixed with debris and heavy rain had already destroyed at least one bridge in Lumajang, preventing rescuers from immediately accessing the area.

But emergency services footage on Sunday showed a desolate scene in the village of Kampung Renteng with rescue workers toiling surrounded by buckled buildings and fallen trees.

"There were 10 people carried away by the mudflow," said a resident of Kampung Renteng. "One of them was almost saved. He was told to run away but said 'I can't, who will feed my cows?'"

Geological summary

Semeru, the highest volcano on Java, and one of its most active, lies at the southern end of a volcanic massif extending north to the Tengger caldera. The steep-sided volcano, also referred to as Mahameru (Great Mountain), rises above coastal plains to the south.

Gunung Semeru was constructed south of the overlapping Ajek-ajek and Jambangan calderas.

A line of lake-filled maars was constructed along a N-S trend cutting through the summit, and cinder cones and lava domes occupy the eastern and NE flanks. Summit topography is complicated by the shifting of craters from NW to SE.

Frequent 19th and 20th-century eruptions were dominated by small-to-moderate explosions from the summit crater, with occasional lava flows and larger explosive eruptions accompanied by pyroclastic flows that have reached the lower flanks of the volcano.

This volcano is located within the Bromo Tengger Semeru-Arjuno, a UNESCO Biosphere Reserve property.6


1 Major explosive event at Sangay volcano, ash to possibly 15.2 km (50 000 feet) a.s.l., Ecuador – The Watchers

2 FVAU01 ADRM 040948 – VA ADVISORY – DTG: 20211204/0948Z – VAAC: DARWIN

3 Semeru volcano spews ash, killing one, injuring 41 – The Jakarta Post

4 Semeru volcano eruption kills 13, dozens injured – The Jakarta Post

5 Indonesia volcano eruption death toll rises to 13 – AFP

6 Semeru – Geological summary – GVP

Featured image credit: WarungJurnalis/Instagram

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