GLACIAL LAKE OUTBURST

Subject : Geography

Context : A glacial lake outburst flood hit the village of Gya in Ladakh, destroying houses, fields and bridges. Using remote sensing data, researchers from Germany have mapped the evolution of Gya glacial lake and note the cause of the flood.

Concept :

• Glacial Lake Outburst Flood (GLOF) refers to the glacier floods caused by the drainage of naturally dammed lakes in the glacier, on or at the margin of glaciers.
• Glacial lakes form when a glacier retreats, leaving the debris mass at the end of the glacier – the end moraine
• The moraine wall can act as a natural dam, trapping the melt water from the glacier and leading to the formation of a lake.
• The moraine dams are composed of unconsolidated boulders, gravel, sand, and silt. As with landslide dams, they can eventually break catastrophically, leading to a glacial lake outburst flood or GLOF.
• Many big glaciers melted rapidly, forming a large number of glacial lakes. Such lakes are inherently unstable and can be subject to catastrophic drainage, which is a potential source of danger to people and property in the valleys below them.

In Himalayas :

• While these events have been regarded as a major risk in the central Himalayan region including Sikkim, the arid Trans-Himalayan regions of Ladakh have received attention only recently. Here the glaciers are located at high altitudes not lower than 5,200 m and most glaciers are of small size.