Glacial Lake Outburst Flood

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 – exposed.  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.

GLOFs are common in Himalayan region. 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. These result in serious death tolls and destruction of valuable natural resources, such as forests, farms, and costly mountain infrastructures. The Hindu Kush-Himalayan region has suffered several GLOF events originating from numerous glacial lakes, some of which have trans-boundary impacts. Nepal has experienced several Glacial Lake Outburst Floods originating from numerous glacial lakes. ^{(Source of this information- India Environment Portal)}

This term was making news because of rumours that the Kedarnath tragedy of last year was caused by a GLOF. However, it was confirmed later that this tragedy was not caused due to GLOF but due to a combination of several factors viz. early rainfall, movement of southwest monsoon winds, and the formation of a temporary lake.