Avalanche

Q:

On 7th April 2012 an Avalanche hit a Pakistan military

Definition: “An avalanche is a mass of snow, often mixed with ice and debris, which travels down
mountain sides, destroying all in its path.

Avalanches are dangerous due to their speed, mass, and force, often striking without warning.
They can bury people, vehicles, and entire buildings, as seen in the case of the 2012 Gayari sector
avalanche in Pakistan, where 140 soldiers and civilians were trapped under deep snow.

Causes of Avalanches:

1. Heavy Snowfall:
o Adds weight to the existing snowpack, increasing the chances of instability.
2. Snowpack Conditions:
o Weak layers within the snowpack can cause the upper layers to collapse and
slide.
o Changes in temperature can melt or weaken certain layers.
3. Slope Angle:
o Avalanches are most likely to occur on slopes between 30° and 45°.
o Too steep, snow slides off frequently; too flat, snow accumulates without sliding.
4. Human Activity:
o Skiers, hikers, or snowmobiles can trigger avalanches by disturbing an unstable
snowpack.
5. Vibrations:
o Natural (thunder) or artificial (explosions, loud noise) vibrations can trigger an
avalanche.
6. Rapid Temperature Changes:
o Sudden warming can melt snow, increasing water content and reducing
snowpack cohesion.

Types of Avalanches:

1. Slab Avalanche:
  Description: These are the most common and most dangerous type of avalanche. In
slab avalanches, a cohesive slab of snow breaks away from the snowpack and slides
down the slope.
 Cause: A weak layer of snow beneath the slab is often the trigger. The slab breaks
away when the weak layer can't support the weight of the snow above it.
 Danger: Slab avalanches can be extremely large, fast-moving, and deadly because
they involve large volumes of snow. They can bury people deep under the snow,
making rescue operations extremely difficult and dangerous.
 Example: The avalanche that hit the Gayari sector in 2012 was a type of slab
avalanche, causing a major disaster.Loose Snow Avalanche:
2. Loose Snow Avalanche:
 Description: These occur when a small amount of loose snow (usually dry snow) is
released at a single point and gradually gathers more snow as it moves downhill. It often
looks like a powder cloud.
 Cause: These avalanches are typically triggered by disturbances, such as a skier or hiker
disturbing the snow surface.
 Danger: Although they are generally smaller and less destructive than slab avalanches,
they can still be dangerous in areas with poor visibility or where people are in the direct
path of the avalanche.
 Example: A skier might accidentally trigger a small loose snow avalanche while moving
through a steep terrain.
3. Ice Avalanche:
 Description: These occur when large masses of ice (often from glaciers) break off and
slide down the slope. Ice avalanches are rare but can be extremely dangerous due to the
volume of material they move.
 Cause: Ice avalanches typically occur in glaciers or icy slopes where the ice fractures and
releases a massive amount of material.
 Danger: While not as common as snow avalanches, ice avalanches can be extremely
dangerous due to the sheer mass and momentum of the ice moving down the slope.
They can also dislodge large rocks and debris along with the ice.
4. Wet Snow Avalanche:
 Description: Wet snow avalanches occur when the snow becomes heavy and wet due to
warmer temperatures or rain. The snow pack becomes saturated, making it more likely
to slide.
 Cause: A rise in temperature during the day or a significant rainstorm can cause the
snow to melt and weaken the snowpack, leading to an avalanche.
 Danger: Wet snow avalanches are usually slower than dry snow avalanches but can be
just as destructive due to the weight and mass of the snow. They are often associated
with springtime when temperatures rise and cause melting.
 Example: In mountainous regions during spring, wet snow avalanches can occur,
particularly after a period of warm weather or rain.

Effects of Avalanches:

1. Loss of Life:
 o Avalanches can bury people under meters of snow, leading to suffocation and
death.
2. Destruction of Property:
o Homes, ski resorts, and roads in mountainous regions can be destroyed.
3. Environmental Impact:
o Damages forests, disrupts wildlife habitats, and alters the landscape.
4. Disruption of Transportation:
o Can block mountain roads, railways, and delay rescue operations.
5. Economic Loss:
o Tourism, agriculture, and transport sectors can suffer huge losses.

Prevention and Mitigation:

1. Avalanche Forecasting:
o Monitoring snowpack, weather conditions, and issuing warnings.
2. Controlled Triggering:
o Using explosives to trigger small, controlled avalanches to prevent larger ones.
3. Barriers and Fences:
o Snow fences, retaining walls, and deflection structures built to reduce avalanche
impact.
4. Zoning Laws:
o Avoiding construction in high-risk avalanche-prone areas.
5. Education and Training:
o Educating mountaineers and tourists about avalanche risks and safety measures.