Life,  Tech

“White Demon” – Avalanche

  Since the beginning of this year, avalanches have occurred in many places around the world, causing casualties and property damage. Xue Beng is called a “white demon”, which makes people talk about it.
  The more serious avalanches in recent years have occurred in the Sarang Pass in Afghanistan. From February 9 to 11, 2010, more than 20 avalanches occurred in the local area, causing 3,500 meters of roads to be blocked, more than 160 people were killed, and more than 130 people were injured.
Snowy “Ghost Killer”

  Avalanches are the migration process of snow and ice on the surface of mountain slopes. When the cohesive force inside the snow cannot resist the gravity it receives, it slides down, causing a large amount of snow to collapse, which is an avalanche. Some places call it “snow landslide”, “snow quicksand”, “push mountain snow” and so on.

  Due to the effect of gravity, the avalanche speed can reach 20 to 30 meters per second; as the snow body continues to fall, its moving speed will increase rapidly, and when the avalanche speed is extremely high, it can reach 97 meters per second (generally grade 12 The speed of the wind is 32.6 meters per second). Studies have shown that there is always a contest between gravity and cohesion on snow-capped mountains. When this wrestling force reaches its maximum, even if the slightest force is exerted by the outside world, such as the running of animals, the rolling of stones, the wind, slight vibration, or even shouting in the valley, as long as the gravity is greater than the snow particles condense into The cohesion of the group is enough to trigger a catastrophic avalanche. Therefore, when climbing the snow mountain, it is forbidden for people to make loud noises. Overall, avalanches depend largely on human activities, and 90% of avalanches are caused by victims and their teams. This kind of avalanche is called “man-made leisure avalanche”. Skiing, hiking, or other winter sports enthusiasts often inadvertently become the “fuse” of an avalanche.
  Avalanches are one of the driving forces that shape mountain topography and landforms and affect mountain ecosystems. They are characterized by potentiality, suddenness, unpredictability, and great destructive power. They are listed as a serious natural disaster in snow-covered mountainous areas.
  Although avalanches tend to be sudden, there is a pattern to their occurrence: most avalanches occur when there is heavy snowfall, especially around snowstorms. At this time, the snow is very soft and less cohesive. Once a small piece of it is destroyed, the rest of the snow will have a chain reaction like dominoes and slide down rapidly. When the temperature rises, avalanches are also prone to occur. At this time, the surface of the snow melts, and the snow water penetrates into the depth of the snow layer drop by drop, which makes the originally solid snow loose, greatly reduces the cohesion and breaking strength between the snow layers, and makes it easy for snow layers to form cracks. slide. In particular, it should be noted that the domino effect of avalanches can be repeated, that is to say, if an avalanche occurs in a certain place, it may happen again in the near future. It all depends on the terrain characteristics of the hillside and certain climatic factors. Typically, the severity of an avalanche depends on the volume of snow, air temperature, direction of the slope, and especially the slope. The most severe avalanches usually occur on hillsides with slopes ranging from 25° to 50°. Mountains that are too steep are unlikely to receive enough snow, and slopes that slope too gently are less prone to avalanches.
  In addition, the occurrence of avalanches has regularity in space and time. Taking my country as an example, high mountains in the southwestern region, such as the Himalayas, Nyainqentanglha Mountains, and Hengduan Mountains, have more snowfall and snow accumulation in winter and spring on the upper parts of the mountains, and avalanches are prone to occur. Due to the influence of the polar air mass in the Arctic Ocean, the Tianshan Mountains and the Altai Mountains have more snowfall in winter and spring, and are also prone to avalanches.
eye-popping hazard

  Avalanches are a serious threat to climbers, local residents and tourists. According to statistics, people killed by avalanches account for more than 35% of all alpine deaths. In an avalanche moving at high speed, the pressure per square meter of the surface of the affected object is more than 40 tons, and no object can withstand such an impact. If people encounter an avalanche on an alpine expedition, they often end up with their entire army wiped out. On April 12, 1981, a piece of ice about the size of a house slipped from the glacier on the top of the Three Buddha Volcano in Alaska to the snow slope, triggering an avalanche, causing millions of tons of snow to roll down rapidly, killing buildings within 13 kilometers along the way. All were destroyed, and a powdery snow cloud 160 kilometers long was created.
  In fact, more terrifying than the avalanche itself is the air wave that forms in front of the avalanche. This air wave is similar to the shock wave produced by an atomic bomb explosion, and its impact and damage are more serious than the snow flow itself. The snow flow can drive the air waves forward. Wherever the air waves go, houses are destroyed, trees disappear, and people will suffocate to death. Sometimes, the avalanche body itself has not yet arrived, and the air wave has already washed away all obstacles on the way forward. In the Peruvian avalanche in 1970, the avalanche body advanced 14.5 kilometers in less than 3 minutes, with a speed close to 90 meters per second, which was much faster than that of a 12-level typhoon. The air wave caused by the avalanche rolled the rock debris on the ground into the sky, causing a “stone rain” in the area.
  In recent years, global climate change has become a hot topic of research and attention. Will global climate change have an impact on avalanches, resulting in an increase in the number, intensity and damage of avalanches? Regarding these issues, some experts have suggested that climate change and avalanches are still related to a longer time scale, such as decades or hundreds of years. Taking Yunnan as an example, on May 2, 2007, an avalanche occurred in Meili Snow Mountain Scenic Area. Experts from the National Climate Center and the Yunnan Climate Center believe that global warming is one of the culprits of the avalanche. Statistics show that the impact of global warming on Yunnan is relatively obvious. Since the 1990s, the average temperature in Yunnan has continued to rise, and the average temperature in the whole province has risen by 0.2°C; after 2001, the temperature increase has been even greater, reaching 0.6°C , the warming trend is obvious, which accelerates the melting of glaciers and snow mountains. It is true that the avalanche event in Meili Snow Mountain has a certain relationship with its own geological conditions, but the impact of global warming cannot be ignored. Statistics show that due to global warming, many glaciers and snow mountains in the world have melted.
Early warning and risk assessment

  Since avalanches are so harmful, are there any technical means to warn of avalanches?

  The study found that early warning of avalanche risk could be provided through satellite monitoring. While studying a typical Himalayan avalanche, scientists at the University of Aberdeen in the UK found that satellite imagery could help monitor avalanche threats in remote mountainous regions. The research team used satellite imagery to study the trajectories of two avalanche events that occurred in the same valley in the Himalayas in 2016 and 2021. Among them, an avalanche in 2021 hit a small mountain town in the Jemoli region of India, causing flash floods, destroying a large amount of infrastructure, and killing more than 200 people. Using satellite dataset modeling, it was found that the 2016 avalanche and subsequent seasonal avalanche deposits may have contributed to this severe 2021 avalanche. What’s more, the research team detected unusual surface movements on the glacier ahead of the 2016 avalanche, signaling an imminent avalanche threat. This discovery shows that similar risks in the future can be warned through satellite data analysis. Remote monitoring based on satellite imagery can effectively cover large areas, and it is possible to further predict large-scale dangerous avalanches by monitoring hanging glaciers. In other words, thanks to major developments in remote sensing satellite technology and the help and support of more available data, people can better understand how a large avalanche event can enhance the size of repeated avalanche events in the same valley. However, the research team stated that although field observations have been proven to be effective in predicting avalanches, such field observations are difficult to be popularized on a large scale due to the great difficulties and risks in operating in remote mountainous areas.

  After years of research, researchers at home and abroad have made great progress in the fields of avalanche formation mechanism, throwing distance, dynamic simulation, risk assessment and zoning, prevention and control. According to reports, in order to accurately monitor and warn avalanches, researchers have designed an avalanche monitoring and warning system based on modules such as GPS, ultrasonic pulses, and single-chip microcomputers. The system can improve the accuracy of monitoring results, make the early warning more intelligent, and effectively prevent the adverse effects of avalanches on human beings. Not only that, the system can also analyze and process the collected data after the avalanche occurs.
  Since automatic weather stations can provide real-time weather and snow depth data, such data can be used to assess the potential for avalanche occurrence. Automatic weather stations can be built around highways, mountain ski resorts, and other critical infrastructure. Through snow depth sensors or users’ own snow condition sensors, automatic weather stations can report snow conditions throughout the year and all day long.
  In addition to real-time monitoring, risk assessment of avalanche disasters can also be carried out, that is, a comprehensive analysis of the possibility and danger of avalanches in the region can be made. At present, domestic and foreign methods for assessing and distinguishing regional avalanche hazards mainly include: investigation and mapping of avalanche disaster points in the field, selecting different indicators to establish an avalanche risk assessment model, and carrying out avalanche zoning and mapping according to different risk levels. Researchers selected different avalanche risk evaluation factors to describe the avalanche risk in the establishment of avalanche risk models in different regions. However, the existing avalanche assessment methods lack the distinction between dry and wet avalanches, and the different causes and disaster-causing mechanisms of the two fundamentally affect the selection of risk assessment indicators. At the same time, because wet avalanches are more harmful to human beings, it is necessary to provide special disaster risk assessment methods, devices, electronic equipment and media for wet avalanche risks.
Prevention, rescue and self-help

  Although people have taken many measures to prevent avalanches, their damage is inevitable. Fortunately, people now have some preventive measures, such as launching artillery shells into dangerous areas to explode, triggering small avalanches in advance, and setting up special personnel to monitor and forecast avalanches.

  How to rescue people who encounter an avalanche is also a difficult problem. Those who encountered an avalanche were buried under the snow, almost isolated from the outside world, and their body temperature continued to drop over time. When the core temperature of the human body dropped below 32°C, some human organs would stop working. After being buried under the snow, the temperature of the extremities drops first, and people will feel numb in the extremities, and then other organs begin to cool down, eventually causing the heart to stop working. When buried for more than 15 minutes, the cold will affect the normal operation of body functions. Studies have found that if the buried time does not exceed 15 minutes, the survival rate of the person can reach 90%; if the buried time exceeds 45 minutes, the survival rate of the person is only 20% to 30%; if the person is buried for more than 2 hours, it is found , almost impossible to survive. Investigations show that those killed by avalanches are often not killed by stones, but by low temperature and lack of oxygen. Of course, the snow also contains life-saving oxygen, and ideally, if you are unfortunate enough to be buried, you should spread your arms and create a breathing space. In this way, the survival time can be effectively extended.
  Relevant information introduces an avalanche rescue system called LUCKY15. The system consists of an avalanche sensing device and an accompanying drone. When an avalanche occurs, the device can sense and determine where the avalanche occurred. Subsequently, the supporting drone took off immediately, flew to the lot and used thermal imaging technology to search for buried people. After the buried person is found, the drone will land on the ground and use the carried snow machine to remove the snow on the trapped person to ensure that the buried person can breathe freely within 15 minutes, and at the same time send a signal to the rescue team to inform the trapped person The location of buried personnel. When there is no avalanche, the drone will stop on the charging pile to charge. In addition, some of the latest snow suits and snow pants have RECCO technology chips. RECCO, short for Avalanche Rescue System, can be used to locate avalanche victims. Avalanche search and rescue operations can become more efficient thanks to the use of such devices and systems.
  For individuals, it is necessary to learn to deal with avalanches and escape by self-help in the correct way.
  First of all, the snow condition and its stability on the route should be estimated in advance. New snowfall and rising temperatures will lead to poor connectivity of the snow layer. Secondly, if you must go along the route where avalanches may occur, you should choose a cold and cloudy day with the temperature below freezing and no snowfall for a period of time;
  Crossing the route, you must not climb along the avalanche trough. Climbing snow-capped mountains in summer should start before dawn and leave the steep snow slopes before 10 am. Pay attention to the snow conditions under your feet. Be extra careful if there are cavities under the hard snow. At the same time, special attention should be paid to the orientation and slope of hillsides. Around 30°-55° north latitude, dry avalanches are more likely to occur on east and north slopes, and wet avalanches are more likely to occur on west and south slopes. Try to avoid staying on the leeward slope, because the snow blown from the windward slope is easy to accumulate on the leeward slope, causing avalanches. Finally, when you set off, you should bring avalanche signal transceivers, detection rods, shovels, helmets, avalanche airbags and other equipment. It is best to tie a red cloth strip on your body so that you can be easily spotted in case of distress.

By setting up an avalanche barrier, the speed of the avalanche can be reduced, and the amount of snow falling down can also be reduced

  If you encounter an avalanche, run towards the higher places on both sides, try to stay away from the snow flow; never run down, because you will be quickly submerged by the snow flow. In the process of escaping, you should throw away the heavy items on your body to speed up your escape. If there are trees, rocks or solid objects around, hold on tight and try not to get swept away by the snow current. If the avalanche has a large area and is very close, and you cannot get rid of it, you can hide behind the rocks nearby; if there is no shelter, you should lean forward and cover your face with your hands to prevent ice and snow from pouring into your throat and lungs and cause suffocation, which is also convenient for avalanches. Stop the movement of your hands; try to maintain a swimming position, keep yourself as close to the surface of the snow layer as possible, and lie on your back or head up. When buried by snow, one hand is raised above the head, which is convenient for judging the top and being rescued. It is necessary to distinguish the up and down direction through “saliva flow”, and then dig up and climb, trying to climb out of the snow or ice. Make room in front of your nose and mouth to breathe. If you cannot climb out of the snowdrift, reduce your activities, slow down your breathing, save your energy, and wait for rescue.

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