What is an Avalanche?
Spending winters in the mountains with nothing but white snow on all
sides can be quite relaxing. For those wanting an adrenaline rush, the
snow is a great place to go skiing, snowboarding and even having
snowball fights. However, being on the slopes means one has to
constantly be alert if they don’t want to get caught in an avalanche.
The rapid descent of snow may seem harmless, but it can cause a lot
of damage to life and property. This is why understanding of
avalanches is necessary for those fond of spending their luxury time in
the mountains.
On any slope, the snow is piled up and supported by a snow-pack. It
keeps the snow from tumbling down all the time. Avalanches occur
when the snow-pack starts to weaken and allows the buildup of snow
to be released. Small avalanches are generally made up of ice, snow
and air. The larger ones comprise of rocks, trees, debris and even mud
that is resting on the lower slopes. Contrary to belief, these snow
slides are not random events that occur without any warning signs.
Winter season is when they are most common, often brought on after
a large storm in the area. Rainfall and sleet also tend to be responsible
for avalanches in the summer and monsoon season.
4 Types of Avalanches
To help in understanding of avalanches, they have been classified into
four types.
1. Loose Snow Avalanches: First of these are the Loose Snow
Avalanches. They are common on steep slopes and are seen after a
fresh snowfall. Since the snow does not have time to settle down fully
or has been made loose by sunlight, the snow-pack is not very solid.
Such avalanches have a single point of origin, from where they widen
as they travel down the slope.
2. Slab Avalanches: Loose Snow Avalanches in turn could cause a
Slab Avalanche, which are characterized by a the fall of a large block
of ice down the slopes. Thin slabs cause fairly small amounts of
damage, while the thick ones are responsible for many fatalities.
3. Powder Snow Avalanches: Powder Snow Avalanches are a mix of
the other forms, Loose Snow and Slab. The bottom half of this
avalanche consists of a slab or a dense concentration of snow, ice and
air. Above this is a cloud of powdered snow, which can snowball into a
larger avalanche as it progresses down the slope. The speed attained
by this avalanche can cross 190 miles per hour and they can cross
large distances.
4. Wet Snow Avalanches: Finally, there are Wet Snow Avalanches.
These are quite dangerous as they travel slowly due to friction, which
collects debris from the path fairly easily. The avalanche comprises of
water and snow at the beginning, but understanding of avalanches has
showed us that it can pick up speed with ease.
Causes of Avalanches
There is no one reason behind the development of avalanches. It was
believed for long that the echo of a human voice in the mountains
could dislodge enough snow to start one. Similarly, a person’s weight
can cause a avalanche too. The sudden addition of weight can fracture
a weak area of snow. However, scientific understanding of avalanches
shows us that there are many environmental factors at work.
1. Snowstorm and Wind Direction: Heavy snowstorms are more
likely to cause Avalanches. The 24 hours after a storm are considered
to be the most critical. Wind normally blows from one side of the slope
of mountain to another side. While blowing up, it will scour snow off
the surface which can overhang a mountain.
2. Heavy snowfall: Heavy snowfall is the first, since it deposits snow
in unstable areas and puts pressure on the snow-pack. Precipitation
during the summer months is the leading cause of wet snow
avalanches.
3. Human Activity: Humans have contributed to the start of many
avalanches in recent years. Winter sports that require steep slopes
often put pressure on the snow-pack which it cannot deal. Combined
with the heavy deforestation and soil erosion in mountain regions, it
gives the snow little stability in the winter months. Further natural
causes include earthquakes and tremors, since they can often create
cracks in the snow-pack.
4. Vibration or Movement: The use of All Terrain Vehicles and
Snowmobiles creates vibrations within the snow that it cannot
withstand. Coupled with the gravitational pull, it is one of the quickest
ways to cause an avalanche. The other is construction work done with
explosives, which tend to weaken the entire surrounding area.
5. Layers of Snow: There are conditions where snow is already on
the mountains and has turned into ice. Then, fresh snow falls on top
which can easily slide down.
6. Steep Slopes: Layers of snow build up and and slide down the
mountain at a faster rate as steep slopes can increase the speed
of snow. A rock or piece of huge ice can shake the snow and cause it
to come down.
7. Warm Temperature: Warm temperatures that can last several
hours a day can weaken some of the upper layers of snow and cause it
to slide down.
Effects of Avalanches
As such, there is little damage to the overall ecological system due to
avalanches. They are a part of nature and have been happening for
thousands of years. However, they are a major natural hazard for the
local human population.
1. Damage to Life and Property: A large number of casualties takes
place after avalanches hit heavily populated areas. Infrastructure is
damaged and the blockage caused, impacts the livelihood of many.
People who enjoy skiing, snowboarding and snowmobiling are at a
greater risk of losing their lives. A powerful avalanche can even
destroy buildings and power supplies can be cut off.
2. Flash floods: When an avalanche occurs, it brings down all the
debris with it and can cause havoc in low lying areas. Flash floods are
seen to happen after avalanches, which is a long term problem many
villagers and townspeople have to deal with. They can also change
weather patterns and cause crop failure in farms present on the lower
fields.
3. Economic Impact: An avalanche can block anything in its path
and even restrict the normal movement of traffic. Various ski resorts
depend on tourists to run their business successfully. Ski resorts and
other businesses are forced to close until the avalanche decreases and
weather conditions become suitable.
