Chamoli disaster due to avalanche

Chamoli disaster due to avalanche

Subject : Geography

Context : The flash flood on February 7 in Chamoli district, Uttarakhand, that claimed at least 72 lives with at least 200 missing was due to a large mass of snow, ice and rock avalanche along with a hanging mass of rock crashing into the RaunthiGarh valley floor.

Concept :

Glacial Lake Outburst Flood (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.
• Failure can happen due to various factors such as:

Erosion, a buildup of water pressure

Avalanche of rock or heavy snow

Earthquake or volcanic eruptions under the ice or

Displacement of water in a glacial lake when a large portion of an adjacent glacier collapses into it.

Avalanche

• Avalanche is a rapid downslope movement of a large detached mass of snow, ice, and associated debris such as rocks and vegetation.
• Small avalanches, or Sluffs, occur in large numbers, while large avalanches that may encompass slopes a kilometer or more in length with millions of tons of snow, occur infrequently but cause most of the damage.
• Humans have been exposed to the threat of sliding snow for as long as they have inhabited mountainous regions.

Types of Avalanches:

• Loose snow avalanches-formed in snow with little internal cohesion among individual snow crystals.
• Slab avalanches-Originate in snow with sufficient internal cohesion to enable a snow layer, or layers, to react mechanically as a single entity.
• Wet snow avalanches-These move more slowly than dry ones and are seldom accompanied by dust clouds.
• Direct action avalanches –These are the immediate result of a single snowstorm. They usually involve only fresh snow.
• Climax avalanches-Result of a series of snowstorms or a culmination of weather influences. Their fall is not necessarily associated with a current storm or weather situation.