At least 26 people are dead and 165 are missing after a flood hit northern India on Sunday. The flood was caused when part of a Himalayan glacier broke off and sent a wall of water and debris down a mountain, sweeping away everything in its path.
Rescuers on Monday were trying to rescue 37 power plant workers who remained trapped in a tunnel.
More than 2,000 members of the military, paramilitary groups and police have been taking part in search-and-rescue operations in the northern state of Uttarakhand.
The flood was caused when a portion of the Nanda Devi glacier snapped off Sunday morning, releasing water trapped behind it.
“Everything was swept away, people, cattle and trees,” Sangram Singh Rawat, a former village council member of Raini, the site closest to the glacier, told local media, according to Reuters.
Here’s what to know:
How are glaciers formed?
Glaciers begin to form when snow remains in the same area year-round, where enough snow accumulates to transform into ice, the National Snow and Ice Data Center said. Each year, new layers of snow bury and compress the previous layers.
Most of the world’s glacial ice is found in Antarctica and Greenland, but glaciers are found on nearly every continent, even Africa.
A large cluster of glaciers is in the Himalayas, which are part of India’s long northern border. Sunday’s disaster occurred in the western part of the Himalayas.
How does a glacier burst?
Proglacial lakes, formed after glaciers retreat, are often bound by sediment and boulder formations. Additional water or pressure, or structural weakness, can cause both natural and man-made dams to burst, sending a mass of floodwater surging down the rivers and streams fed by the glacier.
In this case, National Snow and Ice Data Center scientist Bruce Raup told USA TODAY that the cause of this burst appears to be a landslide that collided with a steep glacier.
He said that steep mountain environments can be hazardous for a number of reasons, including the fact that snow and ice on steep slopes can be unstable and slide catastrophically. In addition, rock and soil slopes, which undergo freeze/thaw cycles, can be unstable and can release, particularly during thaw cycles, Raup said.
Is global warming involved?
Experts said the disaster could be linked to global warming, and a team of scientists was flown to the site Monday to investigate exactly what happened.
Geologist Dwarika Dobhal, from the Wadia Institute of Himalayan Geology, told the Guardian that “climate change will make these events more common.”
High temperatures coupled with less snowfall can accelerate melting, which can cause water to rise to dangerous levels.
“Most mountain glaciers around the world were much larger in the past and have been melting and shrinking dramatically due to climate change and global warming,” said Sarah Das, an associate scientist at the Woods Hole Oceanographic Institution.
Some 3 million Olympic-size swimming pools full of water melt from glaciers in the Himalayas each year, a 2019 study said, and climate change is the primary cause.
Since the early 20th century, with few exceptions, glaciers around the world have been retreating at unprecedented rates, the National Snow and Ice Data Center said.
Can glacial floods be predicted?
Deadly or highly destructive glacial floods have occurred in Peru and Nepal. In Peru in 1941, 6,000 people died when a glacial lake burst through its dam, flooding the town of Huaraz below it.
A number of areas at risk of glacier bursts have been identified worldwide, including in the Himalayas and in the Andes in South America.
But while monitoring is possible, the remoteness of most glaciers presents challenges.
“There are many glaciers and glacial dammed lakes across the Himalayas, but most are unmonitored,” Das said. “Many of these lakes are upstream of steep river valleys and have the potential to cause extreme flooding when they break. Where these floods reach inhabited regions and sensitive infrastructure, things will be catastrophic.”
Contributing: The Associated Press