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What is a Glacial Lake? Causes, reasons and risks associated with Glacial Lake Outburst

Why in News?

After the recent flash floods in Uttarkhand, the Government of India has pulled up its socks to strengthen the rescue missions in this area and the environmentalists all around the country are talking about the pros and cons of the climate change affecting the glaciers.

What is a Glacial lake?

A glacial lake is any body of water which finds its origins in glacial activity. The lakes are formed when the glacier erodes the land and melts to fill the depression created.

The glacial lakes are generally divided into two main groups: 

Ice-contact lakes- These are characterized by the presence of glacier ice terminating in lake water

Distal lakes- These are distant from glaciers or ice sheets, but still influenced by, their presence.

Glacial lakes are common features around the margins of glaciers and ice sheets. They often evolve from ice-contact lakes into ice-distal lakes as glaciers and ice sheets margins retreat and become spatially separated from the lake. 

NASA has recorded the data from the past 30 years and found out that the volume of the glacial lakes has increased by almost 50 percent across the world. 

Although this water stored in the glaciers has lesser impact on the sea levels, it can affect mountain communities downstream of the glacial lakes. 

According to the inventory of Wadia Institute of Himalayan Geology, Dehradun the hill state has a total of 1266 glacial lakes. DP Dobhal, a glaciologist with Wadia institute said, "All of them are not a threat. Formation of a glacial lake is a natural process. Among them, the Moraine Dam poses a threat. But then all Moraine Dam glacial lakes are not dangerous. Only 10-11 may be at risk."

What are Glacial Lake Outbursts?

  1. Glacial lake outbursts, or jökulhlaups, are very high-magnitude floods caused by the sudden drainage of water from a glacial lake. 
  2. Glacial lakes can either form on, in, under, or in front of glaciers and are inherently unstable. 
  3. Such outbursts account for the top seven floods ever known to have occurred in the world. They have been responsible for many floods in the past. 

Eg.- Glacial Lake Outburst in Hunza Valley in Pakistan and flash floods in Uttarakhand, India.

Take a look at the image. One can find here, the Tehsils in Uttarakhand which are vulnerable to Glacial Lake Outburst.

Facts about Glacial Lakes:

  1. These are not as stable as normal lakes. 
  2. The glacial lakes often have ice or a glacial sediment moraine on their sides. It is composed of loose rocks and debris that is pushed to the front ad sides of glaciers. 
  3. The glacier lakes can be quite unstable. They can cause dams and banks to break through massive floods. 

The ice caps of mountains are melting rapidly across the globe, as the world is getting warmer with every passing day. GLOFs are the outcome of this very climate change. It is caused when melting lakes form huge water bodies around ice dams and become prone to burst with any pressure or seismic activity . This in turn results in a powerful flood, loaded with lot of debris.

Know more: All about India's first Geothermal Energy Power Plant Project in Ladakh


Can we drink glacier lake water?

Although clean, but glacial lake water is not drinkable due to presence of a parasite in them

Why are glacier lakes so blue?

Due to rock flour suspended in the lake and the debris the glacier lakes appear blue

Where are the glacier lakes generally formed?

The glacier lake generally form at the foot of a glacier

What is a glacial lake known as?

A glacial lake is called as a tarn

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