Avalanches Essay, Research Paper
Avalanche Testing and Safety
White soft fluffy snow, hard to imagine something so innocent could be so destructive. Just picture a few tons of snow traveling down the mountain at approximately 80 miles per hour, taking down everything in its path. Avalanches have been a threat as long as there has been snow and mountains. Since I m an avid backcountry skier it is important to learn about these life threatening snow masses. So in order to protect yourself from anything you must first learn how it works.
First off there is three main components to an avalanche, without them you can t have an avalanche. They go as follows: 1) snow 2) slope 3) snow instability. Secondly, there are two kinds of avalanches; slab and loose snow. Loose snow are minor and usually never exceed 20 miles per hour. While slab avalanches are the destructive and deadly mountain slides. It is not uncommon for one of these to destroy a small town or forest. Since loose snow avalanches aren t very dangerous, I will discuss slab avalanches. The fundamentals of how these snow masses occur, what to look for when testing and just all-together prevention.
The basic chemistry behind a slab avalanche is when one layer of snow does not bond to the layer below it. Any kind of temperature change, fresh snowfall, the weight of a person, all can cause the slab to break free from the lower layer. The formation of a slab is possible in many ways. One way is for the snow to develop a crust and then there be more snowfall. Since snow doesn t bond to the crust it becomes a potential for an avalanche zone. Another way is for surface hoar to develop, or large ice crystal on the snow. This is usually caused by condensation on the snow surface. This will also have poor bonding characteristics, and cause for a potential slide. The crystal itself is also very stable and will stay in that formation until melted usually. Slab avalanches usually only occur between 35-45 degree slopes and on a concave slope. There are ways possible to test for an avalanche zone. These tests have been developed over the years by ski patrollers, avalanche safety, and seasoned mountaineers. Make sure whenever performing an avalanche test you are not in an area where you could possibly trigger or be in the path of an avalanche.
The most common test to use is the shear test. This test is used to diagnose the snowpack and possible dangers. Find a column of undisturbed snow 2-3 feet deep by 1 foot across. Remove soft and very soft snow from the top of the column. Cut the back of the column with a snow saw, but do not cut deeper than 1 + feet from the top of the column. Insert the shovel at the back of the column, and with both hands pull the shovel toward you until the actual column breaks. If the column breaks in a clean smooth manner, record the height of the failure, force required, and observe the crystals at that site. If the column fails to break, or produces an uneven shear, level the column above the height of the 1 + feet back cut, saw to 1 + feet from the new top and repeat. The easier it is to pull away the slab the more dangerous it is to ski. In order to get an accurate reading and idea of the snow pack the procedure must be performed a few times in different areas.
Another test used is called the Rutschblock test. This is pretty much a giant compression test. This test in particular will give you a good general idea of the slope you are inspecting. Single out a block of snow on a slope you plan to ski/snowboard/traverse in a safe location. The size of the block should be about 5 feet upslope, and 6 feet across the slope. The slope angle should be at least 25 degrees steep on untouched snow, with no natural anchors and an even snow pack. The back of the column can be cut with a ski, pole, large snow saw, or cord. If due to the conclusion of your shear test you find there are no weak layers you don t have to cut the block all the way down to dirt. After you have finished that, a skier with their skis on, steps on the block and applies enough pressure slowly until the block falls. Stability is rated by how much force it takes for a layer of snow to fail. The easier the block of snow slides, the more dangerous it is to ski. Even though these tests can help determine the snow stability they aren t the most accurate. Some avalanche experts have developed what they called a much more accurate snow test, however it has not been fully worked out yet.
The name of the test is the stuff block test. Since it was difficult to find enough information on this particular test I will give a short summary. First, you cut a hole in the snow on the slope your going to descend. Then, you make sure it is perfectly vertical. Next, you weigh exactly ten pounds of snow in a sack on a little portable scale. You must then take the sack and drop it from 10cm and check for stress cracks in the layers. Continue dropping the sack at 10cm increments until you reach 60cm. Checking after every drop for cracks. The specialist have broken the safety scale down to this; cracks below 30cm is dangerous, 40cm is the skiers call, above 40cm is relatively safe.
Even though reading about these tests in books and on the internet it doesn t mean you know what your doing. Its best to take an avalanche course where trained specialists show you what to do in actual avalanche environment. It s especially important to take an avalanche course particular to your area, since snow is different in depending on the mountains.