On February 7, a disaster occurred in the Himalayas, in the Indian state of Uttarakhand. That may have claimed at least 150 lives. After initially speculating that a glacier collapsed or a glacier lake suddenly leaked, it now appears that the course of the deadly event has been rebuilt. British geologist Dave Petley of the University of Sheffield also wrote a report on the American Geophysical Union Blog, A large landslide over a glacier triggered a fatal chain reaction.
He and a few experts came to this conclusion after evaluating various satellite images depicting the area in the weeks and months immediately before and after the disaster. They also used various videos that eyewitnesses uploaded to social media for their analysis. These show, among other things, how a plume of dust first blows across a gorge in the Chamuli region, then a massive flood of water, mud and debris flows downstream. It completely destroyed a hydropower plant under construction, and badly damaged a second plant. A large number of workers may have died in both elbows.
According to Petley, the disaster began a few months ago when a crack formed in a mountain at the end of the river. This mass finally retreated on the morning of February 7: about 0.2 cubic kilometers of rock and ice fell nearly vertically 1,800 meters underground, before crashing onto the Runte Glacier below and pushing further down the glacier. This created large amounts of dust, which was deposited in recent satellite images as a brown layer on the snow and ice covered flanks of the adjacent mountain slopes.
The fiercely accelerating masses of rock that slid down the glacier tore apart the ice and other debris with them and smashed them. At the same time, the friction generated so much heat that the ice melted: water, debris, and fine materials mixed together. The landslide turned into a stream of mud and rubble, which plunged through the narrow valley below the Ice Tongue in the form of a flash flood. The force of the crowd even pushed the river’s water for a while as a wave before merging with it.
Through this analysis, Petley also refutes rumors in social networks, such as claims that such a disaster cannot occur naturally in winter, which is why it must be caused by explosions. Indeed, such events can also occur in the cold season, when the expansion of ice in rock crevices pushes the rocks away from the wall. Landslides like these occur regularly in mountains and could increase in the future due to climate change if water thaws and freezes back in the rocks frequently.
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