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Indonesia volcano: What we know about Mount Marapi

December 7, 2023

An eruption at one of Indonesia's most active volcanoes killed 23 people.

Motorists ride past by as Mount Merapi spews volcanic materials during its eruption in Agam, West Sumatra, Indonesia
Mount Merapi erupts on December 3, 2023Image: Ardhy Fernando/AP/picture alliance

A furious volcanic ​eruption at Mount Marapi​ killed 23 hikers in Indonesia and sent at least a dozen more missing on Sunday.

Hot ash clouds sprawled over several kilometers, blanketing nearby villages with volcanic debris.

More than 50 climbers were evacuated on Sunday and many were treated for burns. Indonesia's Geology and Volcanology Research Agency has warned the public to keep at least three kilometers away from the crater's mouth, and two climbing routes have been cordoned off.

Videos emerging on social media show climbers caked with volcanic dust being rescued and evacuated.

Mount Marapi is one of Indonesia's most active volcanoes.


Where is Mount Marapi?

Indonesia sits on the Pacific Ocean's so-called Ring of Fire — a tectonic belt home to two-thirds of all volcanoes worldwide. Indonesia alone has nearly 130 active volcanoes.

Mount Marapi is located in West Sumatra, Indonesia, and dominates local landscape and culture.

The conical volcano's peak reaches 2,891 meters (9,484 feet). Around 250,000 people live within its 10-kilometer radius.

Why is Marapi risky?

The majority of people living near Marapi practice agriculture — the volcanic ash makes the land fertile and suitable for farming. Although the active volcano poses a severe disaster risk, people refuse to leave the mountains. 

Students are seen at school as Mount Marapi volcano spews volcanic ash
Schoolchildren watch as Mount Marapi spews volcanic ash Image: Iggoy el Fitra/Antara Foto/REUTERS

Marapi is located in a region with high seismic activity, making it prone to earthquakes that can cause sudden eruptions, piling one calamity on top of the other.

Marapi is a stratovolcano, a type of volcano built up of many layers of lava and other volcanic materials. Gas between these layers can cause intense swelling and sudden collapse. This can create an expulsion of hot gasses and debris that flow forcefully downhill, causing mass destruction.

Not to be confused with Mount Merapi

Mount Marapi in West Sumatra is often confused with Mount Merapi, Indonesia's most active volcano. Located between the province of Central Java and the Special Region of Yogyakarta, Indonesia, Merapi has erupted regularly since 1548. One lava dome — a protrusion on Earth from which lava erupts — on its southwest side has produced a total of 91 avalanches.

The growth and collapse of this lava dome led to the formation of a steep side on Merapi. Eruptions over the past two decades have also been accompanied by vicious pyroclastic flows — fast-moving avalanches of hot gas, slurry mudflow, debris, water and other volcanic matter that flow along the volcano's flanks.

Merapi is characteristic of these, producing more dangerous ash avalanches than any other volcano in the world.

Representative image of volcanic ash hurtling towards agricultural lands
Volcanic ash from a different Indonesian volcano, Mount Semeru, hurtling toward agricultural landsImage: Samsul Arifin/ANTARA/REUTERS

Edited by: Clare Roth

A previous version of this article stated that the volcano that erupted on December 3 is named Mount Merapi. This is a different volcano located near Central Java. DW has now amended the article to reflect the name and location of the volcano that erupted: Mount Marapi in West Sumatra. The current text has been corrected accordingly.

DW Sushmitha Ramakrishnan
Sushmitha Ramakrishnan Journalist exploring the interplay of science, politics and society.