Geology And Geophysics

Avalanche



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An avalanche is one of the most violent natural disasters. Each year avalanches take over 150 lives worldwide and the numbers are on the rise. The main reason for the increase is the boom of mountain sports: skiing, snowmobiling, rock and ice climbing, hiking, etc.

Most avalanches happen in the back country, where there are no crowds, ski lifts, or well manicured slopes. Areas of high traffic are controlled by park rangers who monitor the slopes and try to detect and even lessen the chances of avalanches. Often they use explosives to purposely cause small avalanches, to avoid large snow accumulations in potentially dangerous areas. The back country enthusiasts have to rely on themselves and they are the most likely victims.

The key to surviving an avalanche is knowledge, preparation, and caution.

* Before heading to the mountains take an avalanche safety training course. It is the best way to gain knowledge about avalanche safety. You will learn to recognize warning signs, to test the snow by digging a snow pit and doing a sheering tests, how the safety equipment works, etc. There are many organizations that offer such training. For example American Institute for Avalanche Research and Education (AIARE) offers courses all over the United States.

* Check weather forecast and pay attention to avalanche warnings. In mountain resort areas there are continuous updates of the conditions and you should diligently listen to the radio or watch TV forecasts before heading to the slopes. Majority of avalanches happen between December and April. During winter months north slopes are more susceptible and in spring, the south slopes. In winter, the most stable snow pack is created when there is gradual thaw during the day and it freezes overnight. The snow becomes hard as a rock and is often called snow 'cement'. Avalanches usually happen after fresh snow falls onto the cement snow pack. The cement is slippery and fresh snow can easily slide off and trigger an avalanche. Stay off dangerous slopes at least one day after new snowfall. In spring through summer, when it rains and the temperatures are above freezing also at night, snow becomes very unstable (even the cement).

* There are a few ways you can check the safety of the snow pack. Watch out for any cracks in the snow, snow slabs sheering off, or hollow noises as you walk or jump in the snow.

* Travel at the bottom or on top of the slopes. Crossing slopes in the middle you can put you at higher risk of getting caught in an avalanche.

* Do not travel alone. You will have a higher chance of survival if you are in a group.

* Wear warm clothing to avoid hypothermia. Keep your coat zipped to prevent from snow getting under it.

* Bring safety equipment. Here are a few items you should invest in:

- Slope meter is a simple tool measuring an angle of the slope. Most avalanches happen on slopes of 30% to 45% . Avoid slopes that are in danger zone.

- Rescue beacon is used in searches for avalanche victims. It transmits signal and also receives signals from other transmitters. It helps to get to buried victims fast. During an avalanche make sure your beacon is switched on to transmit signal, not to receive it.

- Avalanche cord is usually 30feet long. It was used before beacons became available. You can attach it to a belt (do not wrap it around your body) and let it drag behind. It you get buried in snow at least part of the cord should stay atop.

- Collapsible probes are used to probe the snow in search of victims.

- Shovels are needed for digging through the snow to the victim. After the avalanche the snow settles very quickly and it is hard to dig with hands or skis.

- Avalanche airbag system is designed to keep the victim above the surface. Airbags are packed in a specially designed backpack with a release handle.

Even if you take all the precautions, there is no guarantee that you won't get caught in an avalanche. Sometimes one can happen right under your feet. The most important thing is to stay calm. There are several ways to get out of trouble without much harm, but your survival depends on your ability to think clearly.

* As soon as you see an avalanche coming, shout to others. It will not only warn them, but also let them know of your position. After that try to keep your mouth closed to prevent from chocking on snow.

* If you are on a snowmobile, maneuver it to the side out of the avalanche's path as fast as you can. Then get off of it. Since the snowmobile is heavy, it will get buried deeper, while you might manage to stay on top.

* If the avalanche is way above you, run to the side as fast as possible. The highest volume of snow is in the center of the path and that's where it moves the fastest. Your chances of survival are better, if you are out of the main flow.

* Keep your balance. If you are skiing, try to get rid of the skis. They might drag you in deeper.

* Most likely you will lose the balance within a few seconds. In that case use swimming motion to move with the snow flow. Do not attempt to move against it. Try to keep your head above the snow.

* To try to stabilize yourself; grab a tree or a bush. It can prevent from dragging you down. Do not get under a rock or into a cave. You could get trapped.

* As the avalanche slows down and you aren't at the surface, curl into a fetal position to give yourself more room to breath and to move. If you are not able to do that, as soon as you can cover you mouth and nose with your hands to make and air pocket in front of you. This should allow you to breathe for about 30 minutes.

* When you come to a full stop, stretch one arm upwards to try to reach above the snow.

* Conserve your energy by staying calm. You can call for help, if you hear people. If there is no one around, your only chance is to try to dig yourself out. Once you are under the snow, it is hard to tell how deep you are buried, or which way to dig. You can spit and see which way your saliva goes and dig in the opposite direction. It is said to be a myth, because unless you see light you won't be able to dig yourself out, but it might be all you've got. If you can see light, dig towards it.

* Don't hesitate to urinate, if you have to. It may help rescue dogs to find you.

Many people do not realize how dangerous an avalanche can be, until they encounter one. Here are some numbers that should give you an idea about what to expect:

90% of avalanches are caused by the victim, or a person from the victim's group.

An avalanche travels between 60 and 80 mph, although there has been a record of 150mph. It reaches its top speed within 10 seconds after it starts.

People on snowmobiles are twice as likely to be victims as skiers or snowboarders.

25% of avalanche victims die from trauma from hitting trees or rocks on way down.

75% of victims buried in snow die from lack of air.

2% die from hypothermia.

93% of buried victims are alive if dug out within the first 15 minutes.

After 25 minutes your chances of survival are 50%.

After 45 minutes only 20% of people have been found alive.

95% of people are dead within 2 hours.

The key to surviving an avalanche is to avoid getting caught in the first place. Come to the mountains prepared and do not take unnecessary risks.

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