Glacier Collapse (Geography)
Glacier Collapse (Geography)
Why In News:
Scientific assessment of the recent event in Nepal indicated that the event was associated with a glacier collapse and landslide-generated debris flow, rather than a conventional earthquake.
Glacier Collapse
A glacier collapse occurs when a large portion of unstable glacier ice suddenly detaches and moves downslope.
The moving mass may contain ice, rock, sediment and water, producing a rapidly moving avalanche or debris flow.
Such an event can generate destructive flash floods in downstream valleys.
Glacier Collapse vs GLOF
A glacier collapse involves the sudden failure or movement of a mass of glacier ice.
A Glacial Lake Outburst Flood (GLOF) occurs when water stored in a glacial lake is suddenly released due to failure of its natural dam.
A glacier collapse can trigger or contribute to a GLOF if it enters or destabilises a glacial lake.
Therefore, glacier collapse and GLOF are related but not synonymous hazards.
About Glaciers
Glaciers are large, perennial masses of ice, snow, rock and sediment that form on land and move slowly downslope under the influence of gravity and their own weight.
Glaciers form when snow accumulation over several years exceeds snowmelt and ablation.
With time, accumulated snow becomes compressed into dense firn, which further compacts to form glacial ice.
The process of conversion of snow into firn is known as firnification.
Major Types of Glaciers
Ice Sheets: Vast masses of glacial ice covering extensive areas; mainly found in Antarctica and Greenland.
Ice Caps: Dome-shaped masses of ice that flow outward in different directions.
Valley/Alpine Glaciers: Glaciers that originate in mountainous regions and flow through valleys.
Cirque Glaciers: Relatively small glaciers occupying bowl-shaped depressions (cirques) in mountainous areas.
Major Glacial Landforms
Erosional Landforms:
U-shaped valleys: Formed by the erosive action of glaciers.
Cirques: Bowl-shaped depressions formed at the head of glacial valleys.
Horns: Sharp, pyramid-shaped peaks formed by erosion of surrounding cirques.
Fjords:Deep, narrow, glacially carved valleys submerged and filled with seawater.
Depositional Landforms:
Moraines: Ridges or deposits of rock debris and glacial till left behind by glaciers.
Eskers: Long, winding ridges of sand and gravel deposited by subglacial meltwater streams.
Drumlins: Smooth, elongated hills of glacial till aligned broadly with the direction of ice movement.