2. Natural Disaster and its Types
•A natural disaster is a major adverse event
resulting from natural processes of the Earth
Avalanche
Thunderstorms
Tornados
Earthquakes
Tsunami
Hurricanes
Landslides
Volcanoes
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3. Avalanches
What is Avalanche?
An avalanche is a rapid movement of snow
down a slope as a result of structural weakness
in the snow cover
Three main forms:
• Loose
• Slab
• Slush
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4. Loose Avalanche
These can occur with little warning
At any time in the season
Speeds up to 300 km/hr
Force up to 50 tonnes per m2
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5. Slab Avalanche
The most commonly occurring type
Often started by human error
Speeds up to 10 – 150 km/hr
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6. Slush Avalanche
Usually occur later in the season
Movement rate 8 – 25 km/hr
Carry a considerable weight of snow – up to 1 million
tonnes
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7. What causes Avalanches
Avalanches are caused by layers of snow
building up and gaining strength
A vibration, voice or a train can cause a
avalanche
Rapid temperature changes which cause the
snow to melt or where rain falls on to the snow
When water under the snow build up, it can
cause an avalanche
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8. Avalanche Prone Regions
Avalanches are common in mountainous
areas of the world, especially in Arctic and
temperate regions
Frequency is variable according to local
climatic and topographic conditions
Examples: Alps, Scandinavian countries, US
and Canadian Rockies
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10. Effects of Avalanches
Avalanches can tear down trees, plants and ski lifts
Avalanches kill people by trapping them under the snow
Death and injury from the avalanches are the results of
impacts which fracture limbs, suffocation, hypothermia,
exhaustion, frostbite and shock
Communications, power lines and transport routes are
at risk
Buildings and structures are at risk from impact
pressures of up to 100 tonnes/m2
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11. Modifying the Avalanche
Most management techniques aim to retain the snow
on the mountainside or to deflect the avalanche
Artificially Triggering avalanches using explosive
charges or shelling at safe times and before the
snow accumulates to dangerous levels.
Planting tress along known avalanche paths.
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