Flash floods, landslides, and the flow of “cold lava” from an erupting volcano claimed the lives of at least 43 individuals and left 19 others missing in Sumatra, Indonesia, last weekend.
The aftermath near Mount Marapi, an extremely active volcano in Indonesia, was captured in images and videos by the country’s disaster response agency, showcasing thick layers of mud and ash blanketing the surrounding roads and fields.
What is cold lava?
The phenomenon of cold lava, or “lahar” in Javanese, involves a mix of water and volcanic debris that cascades down a volcano’s slopes, often reaching the valleys below. These flows can move swiftly, covering distances up to 60 km from their source, and can occur at chilling speeds. Cold lava can flow rapidly, at a speed of hundreds of kilometers per hour, and spread as far away as 60 km from the volcano.
Considered much more hazardous than typical lava flows, lahars pose significant threats due to their density and speed, with the ability to destroy or envelop nearly anything in their wake, as noted by the United States Geological Survey. Lahars are particularly dangerous because they can destroy infrastructure, leaving people isolated amidst other volcanic dangers.
Lahars can form both with and without volcanic explosions. Factors like heavy rainfall or snow can mobilize loose volcanic debris, creating a destructive slurry that vegetation does not impede.
Lahars: How minor volcanic eruptions can cause major disasters
Brittany Brand, from the Boise State Hazard and Climate Resilience Institute at Boise State University, explained to Newsweek that even minor volcanic eruptions can trigger these deadly lahars by melting snow and generating swift flows.
Indonesia, with its geography of over 17,000 islands, frequently experiences natural disasters such as landslides and flash floods, especially in its many mountainous and flood-prone regions. The nation sits on the Pacific Ring of Fire, hosting more active volcanoes than any other country, including 127 identified peaks.
Mount Marapi itself has been notably active, erupting multiple times in the recent century, with significant eruptions recorded in December and again in January. The December eruption proved lethal, killing 23 climbers and blanketing nearby communities with volcanic ash up to 3,000 meters high. After its January activity, authorities advised against proximity within 4.5km of the crater. An earlier tragic event in 1979 saw the volcano erupt, resulting in 60 fatalities.
