UPSC Exam Preparation: Topic of the Day – Avalanche
Avalanche is any amount of snow sliding down a mountainside. It can be compared to a landslide, only with snow instead of earth.
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- Surface Avalanche: occurs when a layer of snow with different properties slides over another layer of snow. For example, when a layer of dry loosely packed snow slides over a dense layer of wet snow.
- Full-Depth Avalanche: occurs when an entire snow cover, from the earth to the surface, slides over to the ground.
When the balance between the gravitational force of snow cover and the resisting force of the slope and the anchoring effect of shrubs are lost, avalanches are caused.
Avalanche Prone Areas in India:
- Jammu and Kashmir – Higher reaches of Kashmir and Gurez valleys, Ladhak, Kargil and some of the major roads.
- Himachal Pradesh – Kinnaur, Kullu-Spiti and Chamba are vulnerable areas.
- Uttaranchal – Parts of Tehri Garhwal and Chamoli districts are vulnerable areas.
Snow Avalanche Zones:
- Red Zone: It is the zone where snow avalanches are most frequent and have an impact pressure of more than 3 tonnes per square metre. This is the most dangerous zone.
- Blue Zone: These are the areas where the avalanche force is less than 3 tonnes per square metre and where living and other activities may be permitted with connection of safe designs. However such areas may have to be vacated on warning.
- Yellow Zone: These are the zones where snow avalanches occur only occasionally.
Avalanches may occur due to a combination of factors such as the
- slope of the mountain,
- depth of snow cover,
- wind velocity and atmospheric temperature,
- vibrations caused by gunfire and
- Strength of resisting forces like vegetation cover of trees and shrubs.
Problems Associated
Avalanches create various crisis situations for the local administration;
- Road traffic may be blocked.
- Communication links to vital areas may be disrupted.
- Winter sports may be disturbed stranding tourists in places with scant facilities.
- Small rivers may be blocked creating danger of downstream flooding.
- Avalanches may sometimes hit or bury human settlements down the slopes, as in the Kashmir avalanche of 2005, which killed 278 persons, mostly living in temporary winter hutments.
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