Mount Semeru Volcano (Indonesia)

25.11.2025

Mount Semeru Volcano (Indonesia)

Location and Significance

• Mount Semeru is situated in East Java, Indonesia.
• It is the highest peak on the island of Java, with an elevation of about 3,676 meters (12,060 feet).
• Indonesia lies on the Equator and is part of the Indo-Pacific region, bordered by the Indian Ocean to the west and the Pacific Ocean to the east.
• The volcano is part of the Pacific "Ring of Fire" or Circum-Pacific Belt, known for intense seismic and volcanic activity.
• Semeru is also known as Mahameru, meaning "Great Mountain" or "Mahan Parvat."

Activity and Recent Eruptions

• Mount Semeru is the most active volcano in Indonesia with nearly continuous eruptions since 1967.
• It exhibited a significant eruption in November 2025, producing powerful pyroclastic flows that traveled up to 7-8.5 km down its slopes, accompanied by ash plumes rising 2 km into the atmosphere.
• The eruption forced evacuations of over 500 residents in Lumajang Regency and rescue operations for stranded climbers.
• Authorities have raised the alert level to the highest (Level IV, Awas) and imposed exclusion zones within 8-13 km radius, extending danger zones along river valleys due to risks of lahars or volcanic mudflows.
• The volcano's eruptions tend to generate frequent semi-explosive bursts, gas and ash clouds, and occasional lava dome collapses.
• Its 2021 eruption was deadly, causing more than 50 fatalities and widespread damage.

Geological and Geographical Context

• Semeru is a stratovolcano situated near the Java Sea.
• It lies close to the strategically important Strait of Malacca, between Malaysia and Indonesia near Singapore.
• The volcano's activity is influenced by its location on major tectonic boundaries within the Ring of Fire, where the Indo-Australian plate subducts beneath the Eurasian plate.
• Magma inside the volcano is molten rock beneath the surface; when it erupts, it is called lava.

Safety and Impact

• The recent eruptions have caused ashfall damaging homes, schools, bridges, and farmland.
• Residents are advised to avoid areas near riverbanks prone to lahars and to use masks against ash inhalation.
• The region remains on high volcanic alert, with ongoing seismic activity indicating potential further eruptions.