|
A Few Quick
Avalanche Tips
Here are some excerpts from "Common Questions About
Avalanches", a page located on the avalanche.org site, written by Bruce Tremper,
Director of the Forest Service Utah Avalanche Center. This is an interesting
page with a good first hand account of an "avalanche ride". I recommend you read
the entire page, and anything else you can get your hands on.
In light of the recent deaths in the Selkirks, and the avalanche training last
night, I have clipped these highlights and posted them here. I think this
information is important to anyone who rides a snowmobile and I think we are
probably all more likely to skim over the highlights than read the entire page
from the link above. Please take a few minutes to read them. Most of it, you've
probably heard a hundred times. If you only remember one item from the excerpts
below, it may just be the info you need to stay alive someday. Can't hurt, might
help...
Jim
General avalanche facts:
-----------------------
"Avalanche victims are almost exclusively backcountry
recreationists--snowmobilers, climbers, snowboarders, snowshoers, skiers and
hikers. Snowmobilers lead the list with twice the number of fatalities as any
other activity."
"...in 90 percent of avalanche accidents, the avalanche is triggered by the
victim (or someone in the victim’s party)."
"...a disproportionate number of avalanche fatalities occur when one snowmobiler
gets stuck on a slope and another person rides up to help them."
"You can’t dig yourself out of avalanche debris. It’s like you are buried in
concrete. Your friends must dig you out."
"What we normally call avalanches are "slabs" or cohesive plates of snow that
shatter like a pane of glass and slide as a unit off the mountainside. Picture a
magazine sliding off the table, with the victim standing on the middle of the
magazine."
"Wind is the most common cause of avalanches. Wind can deposit snow 10 times
faster than snow falling from storms. Wind erodes snow from the upwind side of
obstacles and deposits snow on the downwind (lee sides). We call this "wind
loading"."
"Snow is very sensitive to the rate at which it is loaded or stressed. Two feet
of snow added over two weeks is not a problem. Two feet of snow in two days is a
much bigger problem. Two feet of snow in two hours is a huge problem. (Wind can
easily deposit two feet of snow in two hours.) Then, finally the weight of a
person can add a tremendous stress to a buried weak layer, not in two hours, but
in two tenths of a second - a very rapid change."
Assessing the risk:
-----------------
"Almost all avalanches occur on slopes between 35 and 45 degrees. Slopes less
than 30 degrees seldom produce avalanches and slopes steeper than about 50
degrees sluff so often that they tend not to build up into slabs."
"...the bad news is that exactly the kind of slopes we like to ski, snowboard or
snowmobile usually produce most of the avalanches."
"When you hear the snowpack collapse catastrophically with a giant "whoomph",
that's the sound of the snowpack screaming in your ear that it's extremely
unstable."
"Recently wind-loaded, steep slopes are almost always very dangerous while
recently wind-eroded slopes are usually fairly safe. "
"...anchors need to be fairly thick to be effective. For instance a thick,
mature grove of evergreen trees anchor the slab quite effectively while a sparse
grove of aspen trees have very little effect."
"What will happen to you if the slope slides? It's very difficult to survive an
avalanche if it strains you through thick trees or dumps you over a large cliff
or deposits you into a crevasse or dumps you into a narrow gully (creating a
very deep burial). On the other hand you have a fairly good chance of survival
on a small avalanche path, without obstacles and a gentle run-out."
"Never base your stability evaluation on just one test or observation. That’s
like deciding to get married after the first date. Bad mistake. Stability
analysis means integrating many different pieces of information together."
"The best sign of avalanches are other avalanches."
(But just because there are no avalanches around doesn't necessarily mean the
area is safe. -- CT)
Precautions:
------------
"Have an escape route planned. Always think avalanche. What will you do if you
trigger an avalanche? Have a plan first."
"One at a time. There always needs to be someone left in a safe spot to do the
rescue."
(Not to mention the possibility of the extra weight overloading the slab. -- CT)
"Use terrain to your advantage. Follow ridges, thick trees and slopes with safer
consequences. You can almost always go back the way you came. The route got you
there, it will most likely get you back as well."
"Watch out for cornices. They always break farther back than you think. Always
give them a wide berth. NEVER, NEVER walk out to the edge of a drop-off without
first checking it out. Many people have needlessly died this way."
If you get caught:
------------------
"You're first job is to GET OFF THE SLAB..."
"Grab some throttle and use your power and momentum to your advantage. If you're
headed uphill, continue uphill. If you're headed across the slope, continue to
the side to safe snow. If you're headed downhill, you're only hope is to try and
outrun the avalanche. Remember that large avalanches travel 60-80 mph and they
are difficult to outrun."
"Swim. If you can't escape off the slab or grab a tree, then you need to swim
hard. A human body is about three times denser than avalanche debris and it
tends to sink unless it's swimming hard."
"Clear an air space in front of your mouth. As the avalanche finally slows down
and just before it comes to rest, try and clear an air space in front of your
mouth."
"Push a hand upward. Visual clues allow your friends to find you faster."
"After the avalanche comes to a stop, the debris will instantly set up like
concrete. So any actions you take must occur BEFORE it comes to a stop."
In regard to recovering buried victims:
------------------------------------
"Watch them closely. Mentally fix the last seen area and closely watch to see
where they end up. This will greatly reduce the search times if you have a good
idea where to begin the search."
"If the victim is wearing a beacon, turn yours to receive and make SURE everyone
in your party is turned to receive."
"Look carefully for clues, hands sticking out of the snow, snowmobiles, skis,
gloves. In most snowmobile burials, the victim is usually just uphill of their
snowmobile."
"...they only have a precious few minutes to breathe under the snow, so every
minute counts. Spend about a half hour or an hour searching before you go for
help."
"With multiple burials, go for the shallow burials first. Get them breathing but
don't take the time to get them completely dug out, just keep moving and find
the next victim and get them breathing, and so on. Get as many people breathing
as possible before returning to treat the injured."
|
|