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avalanches
by Tessa Valladares
Physical Geology
Fall 2011
     
                                                                                                                                                                       
Avalanches

What They are, How They are Caused, And How to Avoid Them.

    Avalanches are very fast and often happen suddenly, There are usually a lot of warning signs before an avalanche begins . Most of the time, over 90% of the time avalanches are started or caused by a human or animal disturbing the snow. Avalanches kill more than 150 people worldwide each year. Most people killed are those who come across the mountains terrain such as skiers, snowboarders, snow mobiles, etc.

( Picture #1)

Most avalanches are smaller areas of dry powdery snow that doesn’t move and is usually in one big blob. These are smaller avalanches, and can cause damage and injury to people but not to the extent of  the bigger, more organized avalanches. The bigger, more damaging avalanches are caused when huge pieces of hard ice like snow break off of the mountain and begin to slide down the hill, becoming larger and faster as it goes. These moving avalanches can get up to speeds of 80 miles per hour in as little as about five seconds. When people get in the way of these type of avalanches, most do not get out in time.

(Picture #2)

Temperature, wind, how steep the side of the mountain is and the way a mountain faces can determine how a hill avalanches off . Also terrain, vegetation, and how the snow is compacted can also determine whether or not a slope will avalanche and how strong or how much it will avalanche. Because of all the factors, some avalanches are moderate, some are tiny, and some can be disastrous.

Many Avalanches often occur in the 24 hours after a snow storm passes through and drops about 12 or more inches of new snow onto the older more compact snow. The sudden and fast drop of more snow often causes the underneath layers to become weak from the weight, causing them to break off and begin to slide. Avalanches are built up in layers, heavy snow forms a layer of snow then it is compacted by a layer of ice caused by rain, then dirt and other weathering, then more snow, more ice ect. How the layers stick together will determine how weak the layers are, and how easily they will break off.

There are many ways to prevent avalanches and make them less powerful and destructive. Snow packing can be trimmed down by setting off explosions to cause smaller less damaging avalanches so that way one big, devastating one wont happen. Snow fences are also used so that the snow builds up along the fence and does not continue to travel down  hill getting larger and faster. Trees also can reduce the amount of avalanches greatly, or causes the avalanches to be less harmful. They hold snow in place and when there is an avalanche, the snow builds up against the trees and slows it down. In places like ski resorts or places where people are known to disrupt the snow.

(Picture #3)

There are also artificial barriers that can be built, such as snow nets, wooden or metal barriers, etc. But a lot of these barriers cannot stand up to falling rocks, and debri that end up destroying the barriers and the snow comes through anyways.

If caught in an avalanche, try to get off  the big ice that is sliding. Skiers and snowboarders can head down the hill as fast as possible then turn off either to the right or left away from the avalanche. Snow mobiles or other motor vehicles can try to go as fast as possible and also move out of the way.  If your not able to get out of the way you can try to grab for a tree, or if worst comes to worst, they say to try and swim with the snow, and when u come to then end of it “punch a hand towards the sky” and wait. Be sure to try and clear some room for air.

When  the avalanche stops, it becomes like concrete, it is heavy, and dense, and its very hard to even move, so waiting for rescue can be long and hard. “Statistics show that 93 percent of avalanche victims survive if dug out within 15 minutes. Then the survival rates drop fast. After 45 minutes, only 20 to 30 percent of victims are alive. After two hours, very few people survive”.

                Avalanches can be very small and occur when no one is around, and cause no damage, and then avalanches can also be extremely devastating, and cause many deaths and damages. Although avalanches are disasters many different things can be done to prevent avalanches or lessen their fury.

 

 

Photo credit:

Picture 1- http://www.google.com/imgres?q=skier+on+avalanche&um=1&hl=en&sa=N&biw=1366&bih=634&tbm=isch&tbnid=KWgCQuZNGM3UqM:&imgrefurl=http://espn.go.com/action/freeskiing/blog%3Fpost%3D4430198&docid=FaWIKusnoBfXvM&imgurl=http://a.espncdn.com/photo/2009/0828/as_ski_Tremper_550.jpg&w=550&h=399&ei=x0vUTsWfEsrYiAK72622Dg&zoom=1&iact=hc&vpx=1059&vpy=148&dur=284&hovh=191&hovw=264&tx=183&ty=135&sig=107432799905213518047&page=1&tbnh=133&tbnw=182&start=0&ndsp=19&ved=1t:429,r:5,s:0

 

Picture 2- http://www.google.com/imgres?q=avalanche+getting+bigger&um=1&hl=en&biw=1366&bih=634&tbm=isch&tbnid=IuO53bddYjFPUM:&imgrefurl=http://thedeal.cleansnipe.com/stash-your-cache-building-a-budget-backcountry-retreat/&docid=0cS4uied-qm1SM&imgurl=http://thedeal.cleansnipe.com/wp-content/uploads/2010/08/avalanche2.jpg&w=495&h=497&ei=N0zUToTcMYmpiAL1oO3JDg&zoom=1&iact=rc&dur=198&sig=107432799905213518047&page=1&tbnh=129&tbnw=126&start=0&ndsp=23&ved=1t:429,r:1,s:0&tx=72&ty=98

 

Picture 3- http://www.google.com/imgres?q=trees+in+an+avalanche&um=1&hl=en&sa=N&biw=1366&bih=634&tbm=isch&tbnid=rmzHGgqbSkMorM:&imgrefurl=http://sunvalleyonline.com/2010/01/22/skier-dies-in-avalanche-in-the-seattle-ridge-area-of-sun-valley-resort&docid=_Ob8fnn1W88joM&imgurl=http://sunvalleyonline.com/media/weather/2010/1/23/GPVImBoQwDJjTmkl4ebAyumfM-medium.jpg&w=319&h=240&ei=MU3UTqCzHI6MigKa9IWjDg&zoom=1&iact=rc&dur=180&sig=107432799905213518047&page=1&tbnh=132&tbnw=175&start=0&ndsp=18&ved=1t:429,r:14,s:0&tx=106&ty=84

 

 

 

 

Websites surrounding topic:

 

  1. http://en.wikipedia.org/wiki/Avalanche
  2. http://nsidc.org/snow/avalanche/
  3. http://science.howstuffworks.com/nature/natural-disasters/avalanche.htm
  4. http://www.avalanche.org/tutorial/tutorial.html
  5. http://geography.about.com/od/physicalgeography/a/avalanches.htm