Avalanche phenomenon

Avalanche is a kind of surface ice and snow migration process that all snow-capped mountains have. They keep sliding down the hillside from the height of the mountain under the action of gravity. When they collapse, the speed can reach 20-30m/s and the volume can reach hundreds of cubic meters, thousands of cubic meters or even more. Avalanches move downward from a height with great potential energy, such as falling or sliding down from a height of 6000 meters, so they are extremely fast and even form an air cushion layer. If you are lucky enough to lie under it, you may be left in place without being hit by it when it "floats" over you or "flies" out of date. Of course, due to the rapid impact, a strong air billow will be formed at its front end, so sometimes the avalanche itself has not arrived, and air billow has washed away all the obstacles on the road.

The formation and development of avalanche can be divided into three parts, namely, formation area, passing area and accumulation area.

The formation area is mostly in the upper part of the mountain, where there is much and thick snow. For example, high snow eaves, snow slopes with a slope of more than 50-60 degrees and the lower end of suspended glaciers are all areas where avalanches form, which experienced mountain explorers should see. The avalanche passing area is just below the formation area, and it is often a straight U-shaped groove from top to bottom. Because avalanches often pass by, the groove is still very smooth, basically without ups and downs and obstacles. It can be several hundred meters long, 20-30 meters wide or a little larger, but it can't be too wide, otherwise the falling snow and ice will not be concentrated and a big avalanche will not form. The accumulation area is also directly below the stratigraphic area, where the avalanche stops due to the sudden slowdown of the slope at the foot of the mountain. From the landform, it is mostly conical, so it is also called collapse cone (or pile collapse).

Avalanches can be divided into dry avalanches, wet avalanches, powdery avalanches and massive avalanches, and their formation and occurrence have different geomorphological and climatic conditions. Generally speaking, as soon as the heavy snow stops, the snow on the mountain has not had time to melt, or the melted water has not penetrated into the snow below to form a freeze, and the snow is "dry" and "powdered". When this avalanche occurs, the large bottom layer of air mass is easy to form an air cushion layer. When the expedition encounters such an avalanche, people can be wrapped in the avalanche and fly with them.

Avalanches also have laws of time and space. As far as the mountains in China are concerned, the mountains in the southwest border, such as Himalayas, Nyainqentanglha Mountain and Hengduan Mountain, are mainly controlled by the Indian Ocean monsoon. Except the rainy season (May-65438+1October) and the dry season (165438+1October-April), there is abundant precipitation all year round, and there is more snowfall in winter and spring in the upper mountainous areas. In addition, influenced by the polar air mass of the Arctic Ocean, Tianshan Mountain and Altai Mountain have more precipitation in winter and spring, so there are more avalanches this season.

Avalanche observation and research station is a specialized agency of China Academy of Sciences, located in the middle of Tianshan Mountain. Winter snow and avalanches in the central Tianshan Mountains often block mountain roads. The frequent avalanches in Nyainqentanglha Mountain and Hengduan Mountain are also one of the important sources of modern glacier development. Of course, choosing the right climbing time in this area is more demanding. At the same time, in the mountainous areas such as Kunlun Mountain, Tanggula Mountain and Qilian Mountain, which are close to the inland of western China, there is relatively little precipitation, and there is no obvious difference between dry season and rainy season. There may be fewer avalanches, so it is more comfortable to choose a suitable climbing time. In addition, the relative heights of these inland mountains are relatively low, generally between 1000- 1500m, so the slopes of the mountains are relatively gentle. The Himalayas and Karakorum mentioned above are really high mountains and deep valleys, with a relative height of 3,000-4,000 meters or even 5,000-6,000 meters. So the hillside is steep, and the possibility and potential energy of avalanche are greater.

Avoid avalanches

In order to reduce the hazards caused by avalanches, mountain explorers should take some necessary measures.

First of all, explorers should correctly judge whether there are avalanche traces on the mountaineering route. Attention should be paid to distinguish the three sections that constitute an avalanche, and whether there are streaks left by falling snow masses on the snow surface. Avoid the avalanche area when marching. When it is really unavoidable, take the cross route and never climb along the avalanche trough. During the period of 1957, when we climbed the mountain in Gongga Mountain, we traveled along the west side of the avalanche trough for a long time, which implied danger. When crossing, you should walk as fast as possible, and set up a special observation deck to keep an eye on the areas where avalanches may occur at any time. When there are signs of avalanches or avalanches have occurred, you should warn "avalanches" loudly so as to take self-help measures quickly.

When exploring high mountains, whether you choose hiking routes or camps, you should try to avoid leeward slopes. Because the leeward slope is easy to accumulate snow blown from the windward slope, it is also easy to have avalanches. When marching, try to follow the ridge line and walk at the highest point of the mountain to avoid the threat of avalanche. When choosing a marching route or camp, be wary that the flat land you choose may be a "trap". Because in steep mountainous areas, the avalanche accumulation area is most likely to be relatively flat.

Don't climb mountains after heavy snow 1-2 days. You should wait until the new snow collapses before climbing. Heavy snow is often accompanied by good weather, so we must give up good weather and wait for the avalanche to pass! This is a difficult choice, so we can only improvise and look at the specific situation. When it is really unavoidable, you should cross the avalanche area after 10 am. Because, at this time, the "early" sun has been shining on the snow-capped mountains for some time. If an avalanche occurs, it will happen before this time, which can also reduce the danger. In areas with frequent human activities, you can also actively "bomb" the snow in the avalanche formation area by shelling. Don't talk loudly when marching and resting in mountainous areas to reduce the avalanche caused by air vibration. In addition, in the process of marching, it is best to tie red cloth strips to each player to prevent avalanches.

Alpine exploration is a comprehensive activity, and any small negligence may lead to great disaster. Alpine exploration also needs to be calm, and sometimes you must have the courage to admit failure. Blind courage and anger are dangerous.