|
 Everyone
who's ever been or wanted to go off-piste should make it their business
to understand as much as possible about the risks.
This
article, from Facewest,
specialists in backcountry equipment, helps explain the different
types of avalanche you may come across.
Remember - the best
way to survive an avalanche is by not getting caught in one in the
first place.
1. Soft Slab Avalanche
This is the most common
type of winter avalanche and associated with the build up of fresh
snow on lee slopes. The snow is moved by wind of 10-30 mph. After
a heavy snowfall it could occur on any slope. The slab is
released as a single unit but breaks up as it flows over the ground.
If there is enough fresh snow and the slope is steep enough then
it may become a powder avalanche.
2. Dry Powder Avalanche
This type is most common in cold dry conditions and after a fresh
snow fall. If it snowed heavily, at 2cm per hour or more, then it
is especially risky. As little as 20 cm of fresh snow poses a threat.
The snow starts to move as a soft slab and gathers speed and more
snow. The snow will ride up on a cushion of air and become an airborne
powder avalanche travelling in excess of 100 mph. In front of the
avalanche will be a blast wave. Inhalation of snow and suffocation
is often a problem with this type of avalanche.
3. Hard Slab Avalanche
The hard slab represents one of the greatest dangers, not because
of its frequency but because its solid appearance gives a false
sense of security to those travelling over it. The combination of
strong winds (more than 30 mph.) and cold temperature favour it’s
formation. If it remains cold then the danger may persist for some
time. The slab can even be covered by further snow falls. The slab
releases in one unit like a soft slab but breaks up into great chunks
of snow and ice that have enormous destructive power. Watch out
for sudden local subsidence, cracking or dull booming noises as
clues that you may be on a hard slab.
4. Wet Avalanche
Common in spring and thaw conditions, water flowing through the
snow or between the snow and ground has weakened its adhesion. These
travel at relatively slow speeds but carrying a huge weight of snow
and water. These are the easiest to predict due to the weather conditions
for their formation. Cracks in the snow and large snowballs rolling
down are visible clues.
[Article courtesy of
Facewest
- to buy backcountry equipment, check out our online store]
|
