Introduction To Avalanche Theory - Mammut ELEMENT Barryvox Reference Manual

INTRODUCTION TO AVALANCHE THEORY

7. Introduction to Avalanche Theory
We would like to provide you with some basics on
this complex topic and recommend thorough initial
and ongoing advanced avalanche training.
The Slab Avalanche: The Set Trap
Most winter outdoor travelers trigger their own ava-
lanches. The snowpack is fragile. Slab avalanches
resemble set traps: If we trigger it, the trap snaps.
Remember that a small slab of 100 m 3 weighs about
25 tons!
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7.1 Hazard identification
Very critical weather situations
The avalanche danger increases rapidly after
storms with new snow, wind, and cold tempera-
tures. Slopes with wind-drifted snow are especially
dangerous! Snow can also be moved by wind dur-
ing nice weather. The first nice day after a snow
event is particularly dangerous. Most accidents
occur when a cold front with strong winds and
snow moves in after days of blue skies and cold
temperatures! In this situation, new snow amounts
of 10 – 20 cm can constitute a critical situation that
can last several days.
Rapid and strong warming (downslope wind, rain)
can also cause an increase in avalanche danger,
which decreases again with falling temperatures. If
the snowpack is uneven and weak, the danger is
hard to perceive. This is often the case with shallow
snow packs in the beginning of winter or during
periods of little precipitation. In spring, the danger
usually increases as the day progresses: from low
in the morning following a clear night to consider-
able in the afternoon.
7. 2 Risk Assessment
Critical amounts of new snow
With the following amounts of new snowfall within
1 – 3 days, the danger level is at least
CONSIDERABLE:
10–20 cm with adverse conditions
20–30 cm with average conditions
30–50 cm with favorable conditions
Adverse conditions
➜ Strong wind (> 50 km/h)
➜ Low temperatures (< -8° C)
➜ Slope seldom traveled
Favorable conditions
➜ Light wind
➜ Temperatures little below 0° C
➜ Slope traveled frequently
Humans as Trigger of the Trap
The steeper and more shaded the slope is, the
greater the likelihood of releasing a slab avalanche.
The likelihood increases with large groups without
spacing, frequent turns, and especially with falls or
jumps over cornices or other shock loading. Remote
triggering is possible starting with the danger level
CONSIDERABLE, i.e. the person triggering the ava-
lanche can be standing dozens of meters outside of
the fracture zone. This is fatal at the bottom of a
slope, because the entire slope above can be
released!
Note: Light forest (trees far enough apart to ski or
ride through) will not protect you from slab ava-
lanches. Even rock outcroppings will not prevent
the release of slab avalanches.
7.3 Precautions
7.3.1 Standard Safety Precautions
The following standard safety precautions should
always be taken regardless of the danger level:
➜ Avalanche transceiver on SEND,
along with a probe pole and shovel
➜ Avoid fresh wind-deposited snow
➜ Consider daily fluctuations in temperature,
especially in the spring
➜ Constantly assess the conditions
throughout the trip
Pay attention to avalanche hazard even during
the summer, in particular after recent snowfall.
Apply the safety precautions if required.
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