The video footage is violent and unsettling.
On Sunday, a stream of ice, water, mud and debris broke through a steep river valley in the northern Indian state of Uttarakhand. At least 32 people are dead and almost 200 are missing.
The tragic event occurred in a warming Himalayan region where glaciers are rapidly melting and retreating. However, glacier experts say the flood was likely not caused by the collapse or “erupting” of a glacier itself, although the warming climate may have played a role in the larger episode. Geoscientists will learn more in the days and weeks to come, but satellite evidence points to a high-altitude landslide that caused an avalanche of rock, glacial ice, and snow.
“The disaster was triggered by a rock-ice-snow avalanche. We almost certainly know that, ”explains Mohd Farooq Azam, Assistant Professor in Civil Engineering at the Indian Institute of Technology Indore. Azam explores glaciers in the Indian Himalayas.
This avalanche was an extreme event. On a steep ridge at a height of about 5,600 meters, a collapsed mountainside pulled down a glacier lying on the mountain, and the resulting rock-ice-snow mass hit the valley floor at about 3,500 meters. Then the mass flowed all the way down through the valley, said Azam.
With such a fast-moving avalanche, great friction instantly melts ice and snow, which is where some of the surging water seen in the videos comes from, explained Joseph Shea, an assistant professor of environmental geomatics at the University of Northern British Columbia who spent years in the Himalayas -Visited and explored the glacier.
However, the full source of the huge amount of water seen in the videos is an ongoing investigation, Azam said, noting that Indian scientists are judging the event from zero. The avalanche could have taken plenty of ice from the valley floor.
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In a region of rapidly melting ice, the natural question is how the relentlessly warming globe could have contributed to this chaotic event.
Large avalanches occur naturally mainly on steep, rockfall-prone, glaciated slopes. “It is very difficult to determine that this particular disaster was solely due to climate change,” said Azam. Landslides that lead to large debris flows are normal and well documented. A similar landslide occurred in Nepal in 2012.
Above all, however, climate change has increased the melting of glaciers and snow in the Himalayan region, said Azam, adding that “the incidence of mountain hazards due to climate change has also increased”.
See also: Where to See Earth’s Dying Glaciers
This could make a major rockfall or landslide around a glacier more likely. As shrinking glaciers retreat, they can leave unstable slopes open and prone to falling rocks, Shea explained. In addition, a warming climate creates more opportunities for elevated areas to freeze and thaw, freeze and thaw, etc. This allows water to penetrate cracks, freeze and expand, opening larger and larger cracks. “It finally releases these big blocks,” Shea said. At some point, gravity wins.
Both processes could possibly have contributed to the cascading rock-ice-snow avalanche, Shea said.
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The resulting flood of rocks, ice and water eventually flowed through a hydroelectric river dam and kept many workers trapped in a tunnel. Rescue operations are underway despite the loss of lives.
“It’s a tragic event,” said Shea.
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