The rupture of a glacier in the Himalayas, "a small drop in the ocean" -
20 Minutes
At least 32 dead and 170 missing.
The death toll in the flooding of the Dhauliganga River after the rupture of a glacier in northern India continues to rise.
If the precise reasons for this disaster are still uncertain, the landslide that led to the fall of the glacier "would not be directly linked to global warming", explains the glaciologist at the Institute of Environmental Geosciences in Grenoble, Patrick Wagnon .
Having taken part in numerous expeditions to the Himalayas to study the glaciers there, the researcher is well acquainted with the region "often confronted with this type of frequent extreme event", he assures us.
What really happened?
Following a landslide, a piece of glacier fell into the valley, flowing into the Dhauliganga River, causing a flood and the rupture of a dam.
"So it's not really a glacier fall, but rather a landslide from one of the sides of the mountain called the Trisul, which rises to 7,120 meters, on a slope of about thirty degrees. .
A whole part slipped, on which there was a hanging glacier, ”explains Patrick Wagnon.
A chain reaction that led to the fall mixed with rocks and ice, which came to throw themselves into the valley, over 2,000 to 3,800 meters of vertical drop.
“It sprayed, and it generated a lot of heat.
The ice melted, which created a torrential lava, that is to say a mixture of water, loaded with sediment.
So a priori, it is not directly linked to climate change, ”says the glaciologist.
Is this a rare event?
"These are extremely steep regions, especially here, where it is a young mountain with significant relief", explains Patrick Wagnon.
These high altitude regions (nearly 6,000 meters) are therefore subject to extreme climatic conditions, frost and bad weather.
Circumstances that increase the risk of landslides and rock falls.
More sensitive to climate change, the frequency of this type of event is nevertheless increasing due to global warming.
India: At least three dead and 150 missing after the rupture of a glacier in the Himalayas #India #himalayas pic.twitter.com/oLk3G3juMS
- 20 Minutes (@ 20Minutes) February 7, 2021
And after ?
“In the long term, on a geological scale, all the mountains are destined to disappear,” recalls the glaciologist.
Erosion and the transformation of mountains into plains are, in fact, well-known phenomena to scientists, and which have always existed.
But the melting of high-altitude permafrost, observed and proven almost everywhere in the world, could, in the short term, further destabilize the slopes and rock faces, causing more frequent and faster landslides.
“Beyond that, the melting of glaciers has a significant impact on the populations who live in high mountains, analyzes Patrick Wagnon.
Especially for hydroelectricity, irrigation and domestic use ”.
Even if, in the Himalayan range, the glaciers retreat less quickly than in the Alps, thanks to their very high altitude which allows them to regenerate, despite the significant global warming in these regions.
“There will still be glaciers for a long time!
», Assures the researcher.
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