The floods that hit two hydropower plants and damaged villages in northern India were caused by a break on a Himalayan glacier upstream. Here’s a look at how glaciers and glacial lakes form and why they sometimes break:
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HOW GLACIERS AND GLACIAL LAKES FORM
Glaciers can be found on every continent except Australia and some are hundreds of thousands of years old. A large cluster of glaciers is located in the Himalayas, which are part of India’s long northern border. Sunday’s disaster took place in the western part of the Himalayas.
Glaciers are made of layers of compressed snow that move or “flow” due to gravity and the softness of ice in relation to rock. The “tongue” of a glacier can extend hundreds of kilometers (miles) from its high altitude origin, and the end, or “snout,” can move forward or backward based on snow accumulating or melting.
“Ice can flow through mountain valleys, fan out across plains, or in some locations spread out to sea,” said the National Snow and Ice Data Center.
Proglacial lakes, formed after glaciers retreat, are often bordered by sediment and rock formations. Additional water or pressure, or structural weakness, can cause both natural and man-made dams to burst, causing a mass of flood water to flow through the rivers and streams fed by the glacier.
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WHY IS THIS GLACIER RELAXED?
It is not yet known what caused part of the Nanda Devi Glacier to break down on Sunday morning, causing floodwaters to flow downstream to power plants and villages in India’s northern state of Uttarakhand.
Seismic activity and a build-up of water pressure can cause glaciers to burst, but a particular concern is climate change. High temperatures combined with less snowfall can accelerate melting, which can cause water to rise to potentially dangerous levels.
“Most mountain glaciers around the world were much larger in the past and are melting and shrinking dramatically due to climate change and global warming,” said Sarah Das, an associate scientist at Woods Hole Oceanographic Institute.
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CAN SUCH DISASTERS BE PRESENTED?
In the past, deadly or highly destructive glacial floods have occurred in Peru and Nepal.
But the remote locations of glaciers and a lack of monitoring mean we don’t have a clear understanding of how common they are and whether they are increasing, Das said.
“However, given the general pattern of warming, glacier retreat and increase in infrastructure projects, it seems logical to assume that these events will be more frequent and generally more destructive if measures are not taken to mitigate these risks,” said Das.
A number of impending, potentially deadly glacial eruptions and flooding have been identified worldwide, including in the Himalayas and the South American Andes.
But while monitoring is possible, the remoteness of most glaciers presents challenges.
“There are many glaciers and glacier-dammed lakes in the Himalayas, but most of them are not monitored,” said Das. “Many of these lakes are upstream of steep river valleys and can cause extreme flooding if they break. Where these floods reach populated areas and sensitive infrastructure, things will be catastrophic. “
An information page from 2010 published by the International Center for Integrated Mountain Development called for more glacial monitoring in the Hindu Kush Himalayas to better understand “the true degree of glacial lake instability.”
The region where the glacier eruption occurred is prone to landslides and flash floods, and environmentalists have warned against building in the region.
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The Associated Press’s Health and Science Department is supported by the Howard Hughes Medical Institute’s Science Education Department. The AP is solely responsible for all content.