GLACIAL LAKES (Syllabus: GS Paper 1 – Geography)

Context: A little over one in every four glacial lakes larger than 10 hectares in area (100000 sq m) in the Himalayas have increased in size since 1984, increasing the risk of a glacial lake outburst flood or GLOF, a phenomenon that’s become common on account of the climate crisis.

Glacial Lakes

• About: It is defined as a body of water that is present in adequate quantities, extends with a free surface in, beneath, beside, and/or in front of a glacier, and is the result of glacier activities and/or glacier retreating processes.
• Location: Glacial Lakes are common around the borders of glaciers and ice sheets, and they frequently shift from ice-contact lakes to ice-distal lakes when glaciers and ice sheets recede and become spatially separated from the lake.
• Formation: When a glacier erodes the surface before melting and filling the resulting depression. 
• Example: Devtal Glacial Lake, India's highest glacial lake which is located in the Garhwal Himalaya.
• Two main groups: 

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

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

• Sediments: Organic muds, glacial clays, silty clays, and sands are some of the sediments found in glacial lakes, depending on the time of creation.
• Distribution: The distribution of these elements over the lake bottom is determined by the status of the drainage basin as well as the chemical composition of the water.

Glacial Lake Outburst Floods (GLOFs)

• About: Glacial Lake Outburst Flood (GLOF) is a type of flood that occurs when a glacier-contained water body is suddenly released.
• Causes of GLOF: GLOFs happen when the natural dam formed by a glacial lake fails, allowing the stored water to flow rapidly.