Explainer: How glaciers can burst and send floods downstream

The flood that struck two hydroelectric power plants in northern India and damaged the village was caused by a break on the upstream Himalayan glacier. Let’s see how glaciers and glacial lakes are formed and why they sometimes break.


How to form glaciers and glacial lakes

Glaciers are found on all continents except Australia, some hundreds of thousands of years old. A large cluster of glaciers is located in the Himalayas, which is part of India’s long northern border. The Sunday disaster occurred in the western Himalayas.

Glaciers are made up of compressed layers of snow that move or “flow” due to gravity and the softness of ice against rocks. The “tongue” of a glacier can extend hundreds of kilometers (miles) from its origin in the highlands, and the end, or “nose,” can move forward or backward based on snow cover or snowmelt.

According to the National Snow and Ice Data Center, “ice can run down mountain valleys, spread across plains, and in some places into the ocean.”

Glacial lakes that form after glaciers recede are often surrounded by sediment and boulder formation. Additional water, pressure, or structural weaknesses can cause both natural and artificial dams to burst, flooding rivers and streams supplied by glaciers.


Why did this glacier explode?

It is not yet known why part of the Nanda Devi glacier plunged on Sunday morning, sending a surge of floods downstream towards power plants and villages in Uttarakhand, northern India.

Seismic activity and rising water pressure can cause glacier bursts, but one particular concern is climate change. The combination of high temperatures and reduced snowfall can accelerate melting and raise water to potentially dangerous levels.

Salads, a quasi-scientist at the Woods Hole Oceanographic Institution, said: “Most mountain glaciers around the world are much larger in the past and are dramatically melting and shrinking due to climate change and global warming.


Is it possible to predict such a disaster?

In the past, Peru and Nepal have experienced fatal or highly devastating glacial lake outburst floods.

However, the remoteness of glaciers and lack of surveillance means that we do not have a clear understanding of how often glaciers occur and grow.

“But given the overall pattern of warming, glacier retreat, and growth in infrastructure projects, these events occur more often and overall if no measures are taken to mitigate these risks. It seems natural to assume that it will be destructive, “Das said. ..

Numerous potentially deadly glacier ruptures and floods have been identified around the world, including the Himalayas and the Andes of South America.

However, while monitoring is possible, the remoteness of most glaciers presents challenges.

“There are many glaciers and glacier-blocked lakes in the Himalayas, but most are unsupervised,” Das said. “Many of these lakes are upstream of steep river valleys and can cause extreme floods when they break. If these floods reach residential areas or sensitive infrastructure, things will be devastated. It will be something like that. “

A 2010 information page published by the International Center for Integrated Mountain Development called for enhanced glacier monitoring in the Hindu Kush Himalayas to better understand “the actual degree of glacial lake instability.”

Landslides and flash floods are more likely to occur in areas where glacier ruptures have occurred, and environmentalists are paying attention to construction in this area.


The Associated Press’s Department of Health Sciences is supported by the Department of Science Education at the Howard Hughes Medical Institute. AP is solely responsible for all content.

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Explainer: How glaciers can burst and send floods downstream

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