RESOLVING THE LEDGER
This is one outlet's own report from Scientific American — the article as it was filed. Other outlets are covering the same event; open the full story to compare every source side by side.
See the full story · 4 sources
What caused the Nepal disaster—and why climate change could make these events more likely
The disaster has claimed hundreds of lives, and at least 1,400 people are missing
Hundreds of people are dead, and at least 1,400 are missing, after a massive wall of water crashed through towns in Nepal and Tibet, an autonomous region of China. The flood tore up buildings, roads and other infrastructure along its path; the full extent of the damage will likely take weeks or even months to assess. But already, attention is turning to what could possibly have caused this catastrophe and why there was no warning.
Nepali officials have said the floods were likely unleashed by a glacial collapse , which is when a large piece of ice, rock and debris suddenly detaches from a glacier on a mountain. Officials told Indian media outlets that whatever fell off the glacier may have dropped into a glacial lake and blocked a river, resulting in the massive wave of ice, water and debris that plowed through settlements nearby. The glacier was likely a cirque glacier, the officials said, which is a glacier that has formed in a depression or basin high in the mountains.
A glacial collapse is similar to an avalanche—but instead of snow descending from a mountain slope, falling ice gathers energy and debris into a fast-flowing, destructive mixture. In this scenario in the recent disaster, as the material fell, it would have taken on energy and heat that would have caused further melt, adding to the flood.
If you're enjoying this article, consider supporting our award-winning journalism by subscribing . By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.
Dan Shugar, an Earth scientist at University of Calgary in Alberta, says that new satellite imagery shows "the glacier was only part of what failed."
"It looks to have been a large rock avalanche (a big bedrock landslide) that took part of the glacier with it," he says. "We don't know exactly how big yet but big."
The mountain in question is Langtang Lirung, part of the Himalayas. This mountain, which is the 99th highest in the world, is nestled in the Langtang Valley, colloquially known as the "Valley of Glaciers." Material from Langtang Lirung likely fell into the Lende Khola river on the border of Nepal and Tibet. Altogether, the event affected rivers more than 100 kilometers (62 miles) away, according to Reuters .
Initial seismic data suggested an earthquake may have caused the glacial collapse , but the U.S. Geological Survey suggested the avalanche itself set off a magnitude 5.2 landslide.
"You basically had the lower part of a glacier tongue that sheared off because the rock below failed," says Jakob Steiner, a geoscientist at the University of Graz in Austria. "So the glacier had nothing to support itself. That mass of ice and rock dropped from 5,100 to 3,000 meters, damming a river. Once that dam breached, the water accumulated behind it released causing the flood."
On Wednesday Kristen Cook, a geomorphologist at the Institute of Earth Science at Grenoble Alpes University in France, told Scientific American that the scale of the event is "really shocking." Based on initial analysis of seismic data, hundreds of millions of tons of material, including rock, ice and other debris, collapsed, Cook said.
It's possible more floodwaters could be coming. "Currently material remains up on the glacier, as do lakes a bit further down, so this remains a developing situation with potential recurrent events," Steiner says.
It's not clear what exact role climate change had in this catastrophe. What is clear is that Earth's glaciers are melting faster as a result of warming and that melting is destabilizing these glaciers—and the mountains that buttress them. This is particularly true in the Himalayas. A 2023 United Nations report found that Nepal had lost a third of its ice volume in the past 30 years, with glaciers there melting 65 percent faster in the last decade than in the previous 10 years.
"It's difficult to conclusively link a single event directly to climate change," Cook said in her earlier interview with SciAm . "We know it's getting warmer in the Himalaya. Permafrost is melting. Things are becoming unstable."
Shugar says that it is "100 percent" certain that climate change will make these events more likely "by some combination of glacier melt, permafrost thaw, and changes to precipitation and temperature patterns."
"Of course, one other very big factor is human activity," he says. "If an event like this happened in a valley with no people, we wouldn't be having this conversation. But as humans increase our footprint (not just with permanent settlements but also roads, pipelines..., tanker and cruise ship traffic in [fjords], etcetera) we will increase the severity of the disaster."
Claire Cameron is breaking news chief at Scientific American . Originally from Scotland, she moved to New York City in 2012. Her work has appeared in National Geographic , Slate , Inc. Magazine , Nautilus , Semafor , and elsewhere.
If you enjoyed this article, I’d like to ask for your support. Scientific American has served as an advocate for science and industry for 180 years, and right now may be the most critical moment in that two-century history.
SciAm always educates and delights me, and inspires a sense of awe for our vast, beautiful universe. I hope it does that for you, too.
If you subscribe to Scientific American , you help ensure that our coverage is centered on meaningful research and discovery; that we have the resources to report on the decisions that threaten labs across the U.S.; and that we support both budding and working scientists at a time when the value of science itself too often goes unrecognized.
There has never been a more important time for us to stand up and show why science matters. I hope you’ll support us in that mission.
Jeanna Bryner, Edit...
AIPROPX is an independent multi-source news index — we track, compare, and connect coverage from across the web into one place you won't find anywhere else.