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CLAT 2021 21 Year Experienced Team

How glaciers and glacial lakes form?
Glaciers are found on every continent except Australia and some are hundreds of thousands of years old;
and a large cluster of glaciers are in the Himalayas. Glaciers are made of layers of compressed snow that
move or “flow” due to gravity and the softness of ice relative to rock. A glacier's “tongue” can extend
hundreds of kilometers from its high altitude origins, and the end, or “snout," can advance or retreat based
on snow accumulating or melting.
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 manmade dams to burst,
sending a mass of floodwater surging down the rivers and streams fed by the glacier.

What is GLOF?
A GLOF is a type of outburst flood that occurs when the dam containing a
glacial lake fails. An event similar to a GLOF, where a body of water contained by a glacier
melts or overflows the glacier, is called a jökulhlaup. The dam can consist of glacier ice or a terminal moraine.

Causes of GLOF
i. A buildup of water pressure or structural weakness of boundary due to an increase in the flow of water.
ii. An earthquake (Tectonic) or cryoseism (non-tectonic seismic event of the glacial cryosphere) can also
cause GLOF. During this, the boundary of the glacial lake will collapse suddenly and release the water in
the glacial lake.
iii. An avalanche of rock or heavy snow: During this, the water in the glacial lake might be displaced by the
avalanche.

iv. Volcanic eruptions under the ice can also cause GLOF. These volcanic eruptions might displace the
boundary or increase the pressure on glacial lake or both.
v. Heavy rainfall/melting of snow: This can lead to massive displacement of water in a glacial lake.
vi. Long-term dam degradation can also induce GLOF.
vii. Other reasons such as the collapse of an adjacent glacial lake, etc.

How vulnerable are the Himalayas to GLOFs?
Unlike earthen dams, the weak structure of the moraine dam leads to the abrupt failure of the dam on top of
the glacial lake, which holds large volume of water. A failure of the dam has the potential of releasing millions
of cubic metres of water in a short period, causing catastrophic flooding downstream. According to NDMA,
glacial retreat due to climate change occurring in most parts of the Hindu Kush Himalaya has given rise to the
formation of numerous new glacial lakes, which are the major cause of GLOFs.

Since glaciers in the Himalayas are in a retreating phase, glacial lakes are
growing and pose a potentially large risk to downstream infrastructure and life.
Why did the glacier in Uttarakhand burst?

It's not yet known what caused part of the Nanda Devi glacier to snap off Sunday morning, sending
floodwater surging downstream toward power plants and villages in India's northern state of
Uttarakhand.Seismic activity and a buildup of water pressure can cause glaciers to burst, but one particular
concern is climate change. High temperatures coupled with less snowfall can accelerate melting, which
causes water to rise to potentially 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.

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