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Massive Rock and Ice Avalanche in Indian Himalaya Studied

June 10, 2021
raini hydroelectric plant

The destroyed 13.2 megawatt Rishiganga Hydropower project at Raini Village, about 13 kilometers  downstream of the rock and ice avalanche site. Fifty-three people out of the 204  killed or missing were at this site.

Credit: Mohd. Farooq Azam

Releasing the energy of about 30 Hiroshima atomic bombs, a huge wedge of rock, carrying a small glacier, collapsed from a Himalayan ridge. The gigantic avalanche of ice and rock sped down the Ronti Gad, Rishiganga, and Dhauliganga river valleys in Uttarakhand, India on Feb. 7, 2021, destroying two hydropower generating facilities and leaving more than 200 people dead or missing. 

“This disaster has taught us a lot about an entirely different kind of far-reaching hazard to hydropower generators being developed in the Himalayas,” said Planetary Science Institute Senior Scientist Jeffrey Kargel, a co-author of “A massive rock and ice avalanche caused the 2021 disaster at Chamoli, Indian Himalaya” that appears in Science. Fifty-two scientists analyzed satellite imagery, seismic records, and eyewitness videos and produced computer models of the flow. The team found that 27 million cubic meters of rock and glacier ice had collapsed from the steep north face of Ronti Peak. “The mass fell so far and fast that friction melted nearly all the ice, turning a solid mixture into a debris flow and muddy flood,” Kargel said. 

The source of this disaster was discovered by Dan Shugar (University of Calgary), the paper’s lead author. “High-resolution satellite imagery acquired as the disaster unfolded was critical to helping us understand the event almost in real time. Using satellite images, we tracked a plume of dust and water to a conspicuous dark patch high on a steep slope. This was the source of a giant landslide that triggered the cascade of events and caused immense death and destruction,” Shugar said. 

“This part of the Himalaya is riven with fractures,” said PSI’s Kargel. “The mass movement’s source looks like a giant cookie cutter extracted a perfect rock wedge shaped by four fractures or faults.” 

The rock and ice avalanche fell about 3,300 meters (11,000 feet). “The rock exploded to bits as it crashed down the steepest slopes during the first 1,600 meters – about a mile, releasing energy equivalent to about 15 Hiroshima atomic bombs. As the fall continued, more energy equivalent to an additional 15 Hiroshima atomic bombs was released,” Kargel said. “In minutes, that mass and energy crushed the rock to dust and melted almost all the ice, making a gushing muddy slurry, which then destroyed infrastructure and human lives. 

“The energy needed to pulverize the rock, melt the ice, and ravage the valley was provided by gravity, the mass of collapsed rock and ice, and more than two miles of fall distance,” Kargel said. 

Kavita Upadhyay, a water policy expert and Indian journalist who has written about the natural environment and hydropower of the region, is also a co-author on the paper. She described the losses: "The muddy flood wrecked two hydropower projects and swept away bridges. At least 190 of the victims were hydropower project workers who were unable to escape from the project sites.” 

Upadhyay said, “The Uttarakhand Himalaya has had numerous prior disasters, including a rainfall and glacier lake outburst flood that killed more than 4,000 people in 2013. For decades, local villagers warned of mountain hazards.”

The Science paper provided satellite evidence that previous giant ice masses had been dislodged from the same ridge and struck the same valley area in recent years just above the destroyed 13.2 megawatt Rishiganga hydropower facility. “The Vishnugad Tapovan project had a long history of repeated damaging flash floods and a rockfall,” Kargel said. “The much greater magnitude of this event certainly argues for avoiding development in these areas, especially given that we can expect global warming to increase their frequency.” 

Kargel’s work was funded by NASA grants to PSI from NASA’s Interdisciplinary Science Program and High Mountain Asia Team. 


Alan Fischer
Public Information Officer



Jeffrey Kargel
Senior Scientist


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