Snow avalanches are one of the most Snow avalanches. Sloping slope

One of the most terrible avalanches in the history of mankind came down from Mount Huascaran (Peru) about half a century ago: after an earthquake, a huge mass of snow fell from its slopes and rushed down at a speed exceeding three hundred kilometers per hour. Along the way, it broke off part of the underlying glacier, and also carried sand, rubble, and blocks with it.

Avalanche season is approaching. What hazards and factors do you need to consider when snowmobiling or skiing around Longyearbyen? For the first time, avalanches have been observed for more than three years in the Longyearbyen region. These new observations are timely and important for advancing our understanding of how snow affects the high arctic landscape here in Svalbard. In the last ten years alone, avalanches have caused five deaths.

The project was initiated with the aim of observing cold-slope processes in the Longyearbyen region and their impacts on transport and infrastructure, in order to use this knowledge to evaluate their responses to future climate change projections. Snow avalanche observations were carried out in about 17 km 2 large area around Longyearbyen, around the most used snowmobile "Small Circle" here in the center of Svalbard.

In the path of the snow flow there was also a lake, the water from which, after a tremendous force of impact, splashed out and, adding water to the rushing mass, formed a mudflow. The avalanche stopped only after it had covered a distance of seventeen kilometers and completely demolished the village of Ranairka and the city of Yungai, killing about twenty thousand people: only a few hundred local residents managed to escape.

Figure 1: The farthest fault location of all 423 avalanches, indicated by points along the "Small Circle" snowmobile trail. The colors of the dots distinguish between avalanche types. What types of snow avalanches should we watch out for? A unique feature of the avalanche regime in the Longyearbyen region is that almost half of all snow avalanches are cornice avalanches.

Because of big mountains plateau huge snowdrifts, the so-called cornices, grow along the top of the plateau. These cornices can collapse and their impact on the slope below causes an avalanche. We therefore recommend staying away from slopes that have cornices at the top, such as the Gryvefjellet slope above Nyben.

An avalanche is formed by snow, ice and rocks after they begin to slide down steep mountain slopes at an ever-increasing speed (from 20 to 1000 m/s), capturing new portions of snow and ice, increasing their volume. Considering that the impact force of the elements often amounts to tens of tons per square meter, an avalanche sweeps away everything in its path. It stops only at the bottom, having reached gentle sections of the slope or finding itself at the bottom of the valley.

Avalanches of powdery, dry recent snow

When is the most dangerous time of winter? The timing of snow avalanche activity varies between Svalbard and other locations at more southern latitudes. Snow cover only builds very slowly, due to the low amount of precipitation that Svalbard usually receives. Thus, it will take some time in winter before a uniform snow cover is established on the slopes, allowing the release of an avalanche.

Avalanche danger in the Sakhalin region

This is also due to extreme differences in lighting conditions. Once the sun returns with 24 hours of daylight after polar night, an avalanche begins. During these very cold and stable periods of high pressure in the spring, avalanche activity is again reduced to a minimum. In cold conditions, snow does not deform as quickly as in warmer conditions. Thus, direct insolation enhances the release of a snow avalanche.

Avalanches form only in areas where there are no forests, the trees of which could slow down and prevent the snow from gaining the required speed.

The snow cover begins to move after the thickness of the freshly fallen snow begins to be at least thirty centimeters (or the layer of old snow exceeds seventy), and the steepness of the mountain slope ranges from fifteen to forty-five degrees. If the layer of fresh snow is about half a meter, the probability of snow melting in 10-12 hours is incredibly high.

It passed through the road to Nyben and destroyed the coal transportation system, which survives as cultural heritage on the slope. The left cornice fall avalanche was artificially released when explosives were deployed to detach the cornice. Are we safe on snowmobile tours in the terrain? In most cases, yes, unless your tour group is staying for an extended period in a narrow valley or ravine, as this will be typical snow avalanche terrain. So stick to a higher area where you can view the surrounding area.

It is impossible not to mention the role of old snow in the formation of avalanches in the mountains. It forms an underlying surface that allows freshly fallen precipitation to slide over it unhindered: old snow fills all the unevenness of the soil, bends bushes to the ground, forming a perfectly smooth surface (the larger its layer, the fewer rough obstacles that can stop the snow from falling).

From this point of view, traditional is also much better. Most snowmobile trails follow flat terrain in the valley floors, and we observed most avalanches stopping at 25°. The snowmobile route through Todalen was buried in three places, in one area with 12 meters of avalanche snow. Both extreme events occurred due to very slow passage of low pressure systems, resulting in several days of above-zero temperatures and a 100-year period of rain.

Three avalanches crossed the track on snowmobiles, the furthest of them buried the snow moving track with 12 meters of compact avalanche snow. How is the weather effect of an avalanche on Svalbard? These periods had at least five releases and lasted from one to 12 days.

Therefore, especially after these snowstorms, riding conditions may be good, but avalanche conditions are quite dangerous. During or immediately after such snowstorms, you may also see several avalanche slabs. Shale avalanches are released due to increased snow loading on a weak snow layer, which consequently collapses. So it's special interesting guy snow avalanche because it tells us about weaknesses in the snowpack and the meteorological cause that increases the load or weight.

What should we pay attention to when skiing? The landscape around Longyearbyen is generally very dry, with precipitation of no more than 200 mm each year. This is due to wind snow redistribution, which plays a very important role in the spatial variability of snow depth as well as snow stability. The further down such a weak layer of snow is buried in the snow, or in other words, covered by wind, accumulated snow, the more difficult it is to cause a crack in it when skiing.

The most dangerous periods when snow falls occur are considered to be winter and spring (about 95% of cases are recorded at this time). A snowfall is possible at any time of the day, but more often this event occurs during the day. The occurrence of landslides and avalanches is primarily influenced by:

  • Snowfall or concentration of huge amounts of snow on mountain slopes;
  • Weak adhesive force between new snow and the underlying surface;
  • Warming and rain, resulting in the formation of a slippery layer between snow precipitation and the underlying surface;
  • Earthquakes;
  • Sudden change temperature regime(sharp cooling after unexpected warming, which makes it possible for fresh snow to slide comfortably over the formed ice);
  • Acoustic, mechanical and wind effects (sometimes a scream or clap is enough to set the snow in motion).

Sweeping everything out of the way

Freshly fallen snow precipitation is held on the slope due to the friction force, the magnitude of which depends primarily on the angle of the slope and the moisture content of the snow. A collapse begins when the pressure of the snow mass begins to exceed the force of friction, resulting in the snow coming into a state of unstable equilibrium.

It should be noted that snowmobiles, due to their weight, can impact deeper parts of the snowpack and thus can more easily release an avalanche on a deeply buried weekly layer. A snowmobile also travels through much more terrain in a shorter time, making it more likely to hit a weak spot in the snowpack.

These events are clearly determined by extreme meteorological conditions, and not by an increase in average annual air temperature. Therefore, the frequency and duration of passages of the low pressure system in Svalbard are of great interest. Surprisingly, Zahn and von Storch modeled a decline in North Atlantic polar lows associated with future climate warming. We can therefore expect Svalbard to see less low-lying systems, and therefore fewer snowstorms and therefore fewer snow avalanche cycles.

As soon as the avalanche begins to move, a pre-avalanche air wave is formed, which clears the path for the avalanche, destroying buildings, filling up roads and paths.


Before the snow falls, a dull sound is heard high in the mountains, after which from the top down to high speed a huge cloud of snow rushes in, taking with it everything that gets in its way. It rushes without stopping, gradually picking up pace, and stops no sooner than it reaches the bottom of the valley. After this, a huge layer of snow dust shoots high into the sky, forming a continuous fog. When the snow dust falls, dense piles of snow open before your eyes, in the middle of which you can see branches, remains of trees, and boulders.

Avalanche danger in the Ural District

However, we don't know how strong these smaller amounts of low pressure are. We can conclude, however, that as the number of meteorological snow avalanche events decreases, cornice fall avalanches will become even more dominant. We wish you all a pleasant winter season here in Svalbard. If you would like to explore our findings, here are links to our scientific journals related to the topics of this short article.

"High Arctic maritime snow climate" in Central Svalbard. Relative meteorological variables to the natural slab avalanche regime in High Arctic Svalbard. Meteorology, topography and snow conditions causing extreme average winter slush and wet slab avalanches in high altitude maritime Svalbard.

How dangerous are avalanches?

According to statistics, it is the collapse of snow that causes fifty percent of accidents in the mountains, and often causes the death of climbers, snowboarders, and skiers. An avalanche coming down can simply throw a person off the slope, which is why he can break during the fall, or cover him with such a thick layer of snow and cause death from cold and lack of oxygen.

Permafrost and periglacial processes. One of the worst positions to find yourself is getting stuck in an avalanche. Death is a very likely factor when you are caught in a snow slide. 90 percent of these unfortunate events occur while a person is on a mountain with snow or skiing, snowboarding or snowmobiling, so this is something to consider the next time you decide to undertake a snow activity.

Sloping slope

An avalanche is simply a rapid flow of snow down a slope. This occurs in the starting area when the forces on the snow are too heavy for its base. The lower they go down the slope, the more they grow in mass because it accumulates more snow as it goes down.

A snowfall is dangerous because of its mass, often amounting to several hundred tons, and therefore, covering a person, often leads to suffocation or death from painful shock caused by broken bones. In order to warn people about the approaching danger, a special commission developed a system for classifying the risks of avalanches, the levels of which are indicated by flags and posted at ski resorts and resorts:

Even though snowpack is usually made up of air and snow, it can accumulate a lot more things going downhill, such as ice, rocks, trees and more on the slope, making it extremely dangerous for hikers on the mountain.

Avalanches are not rare or random events that occur once in a specific area. They usually occur in winter or spring, but movements in the glacier can cause avalanches at any time. In mountainous areas, snow slides are one of the most dangerous natural hazards to life and property because they are capable of destroying almost everything in their path with huge amounts of snow at high speeds.

  • The first level (minimum) - the snow is stable, so a collapse is possible only as a result of a strong impact on the snow masses on very steep slopes.
  • Second level (limited) - the snow on most slopes is stable, but in some places it is a little unstable, but, as in the first case, large avalanches will occur only due to a strong impact on the snow masses;
  • The third level (medium) - on steep slopes the layer of snow is weakly or moderately stable, and therefore an avalanche can form with little impact (sometimes an unexpected large snowfall is possible);
  • Fourth (high) - the snow on almost all slopes is unstable and an avalanche occurs even with a very weak impact on the snow masses, while a large number of medium and large unexpected avalanches may occur.
  • Level five (very high) – the likelihood of a huge number of large landslides and avalanches, even on non-steep slopes, is extremely high.

Safety precautions

To avoid death and not to be buried under a thick layer of snow, every person going to the mountains on vacation while there is snow there must learn the basic rules of behavior when a deadly stream descends.

The ten deadliest avalanches in history

Avalanche facts and information. While rescuers were trying to pull them out, another unexpected avalanche appeared and wiped them out. One of the most ironic cases is that in Wellington, Washington, three trains carrying 119 people were held up at the station so they would not have to travel in bad weather. Unfortunately, the avalanche defeated the entire purpose of the stop when it swept the trains down a 150-foot cliff. No one survived the avalanche, however 4 people who were away returned home only to have their entire community, homes and friends destroyed. These events were caused warm streams air, combining with polar air currents, causing much more precipitation than the area could reach. Spurred by a blizzard of wind and snow, the Laval avalanche in the Himalayas buried 200 people under 20 feet of snow. It was the only avalanche in the Himalayas to be in the top ten most dangerous avalanches in the world. Leaving only 50 people alive, the avalanche in Ranrahirka, Peru occurred several years before the Great Peruvian Earthquake. Part of the Allalin glacier broke and fell onto the construction site, destroying everything in its path. This avalanche caused numerous fires, which led to the destruction of the city. . Although people usually cause avalanches, they obviously happen in other ways too.

If an avalanche warning has been announced during your stay at the base, it is advisable to refrain from hiking in the mountains. If there was no warning, then before leaving the base and hitting the road, you need to take into account the forecast of the risk of snow melting, as well as find out as much as possible about the mountains in which the risk of avalanches is maximum and avoid dangerous slopes (this simple rule of behavior is quite capable of saving life).

They can occur when there is increased snowfall load. Melting from solar radiation is another natural way in which avalanches occur. Rain, icefall, falling rocks, and earthquakes also trigger avalanches, depending on the circumstances. It is always important that you pay attention to weather reports if you plan to perform any snow operations where there is a possibility that an avalanche may occur.

There are various avalanches, which are classified according to the characteristics of the avalanche. Knowing which areas are prone to which types of avalanches can be helpful when planning a ski trip or any activity that involves mountain snow. In steep areas there are scanty snow avalanches. They are usually found in snow that has just fallen. Additionally, they can occur in old surface snow that has been wetted by heavy solar radiation. False snow avalanches usually start at a point on a slope and expand as they move downhill, using more snow.

If heavy snowfalls were recorded before going to the mountains, it is better to postpone the hike for two or three days and wait for the snow to fall, and if there are no avalanches, wait until it settles. It is also very important not to go to the mountains alone or together: it is advisable to stay in a group. This will always provide avalanche insurance, for example, if the group members are tied with avalanche tape, this will make it possible to detect a companion covered in snow.

Before going out into the mountains, it is advisable to take with you an avalanche transceiver, which will make it possible to find a person caught in an avalanche.

It is very important not to forget to take your mobile phone with you (it has already saved more than one person’s life). It is also a good idea to take special avalanche backpacks, which have a system of inflatable cushions that make it possible for a person caught in an avalanche to “float up”.

In the mountains you need to move only along roads and paved paths of valleys and along mountain ridges, and it is very important to remember that you cannot drive onto steep snow-covered slopes, cross them across them, or move in a zigzag. It is also forbidden to step on snow cornices, which are accumulations of dense snow in the form of a canopy on the leeward side of a sharp ridge (they may well collapse suddenly and cause an avalanche).

If it is not possible to go around a steep slope, before overcoming it, you need to make sure that the snow cover is stable. If it begins to sink under your feet and begins to make a hissing sound, you need to go back and look for another road: the likelihood of an avalanche is high.

Trapped in snow

If an avalanche has fallen high and there is time to do something, it is very important to remember one of the basic rules of behavior when an avalanche is rushing towards you: you need to move out of the path of the rushing stream to a safe place, moving not down, but horizontally. You can also hide behind a ledge, preferably in a cave, or climb onto a hill, a stable rock or a strong tree.

Under no circumstances should you hide behind young trees, as snow can break them.

If it so happens that you were unable to escape from an avalanche, one of the rules of conduct states that you need to immediately free yourself from all things that will be pulled into the rushing stream and hinder your movements: a backpack, skis, poles, an ice ax. You must immediately begin to sharply make your way to the edge of the stream, doing everything possible to stay at the top, and if possible, catch on a tree, stone, or bush.

If the snow still covers your head, then you need to cover your nose and mouth with a scarf or hat to prevent snow from getting there. After which you need to group: turning in the direction of the movement of the snow flow, take a horizontal position and pull your knees to your stomach. After this, by rotating your head in a circular motion, remember to create as much free space in front of your face as possible.


As soon as the avalanche stops, you need to try to get out on your own or at least push your hand up so that rescuers notice it. Screaming while under snow cover is useless, since the sound is transmitted very weakly, so such efforts only weaken the strength (sound signals should only be given when the steps of rescuers are heard).

It is important not to forget the rules of behavior in the snow: you need to remain calm and under no circumstances panic (screams and meaningless movements will deprive you of strength, warmth and oxygen). Don’t forget to move, otherwise a person squeezed in the thick snow will simply freeze, for the same reason you need to do everything to avoid falling asleep. The main thing is to believe: there are cases when living people were found under snow cover even on the thirteenth day.

Mountains are undoubtedly one of the most beautiful and mesmerizing panoramas on Earth. Many strive to conquer the majestic peaks, not fully realizing how severe such beauty is. That is why, when deciding to take such a brave step, extreme sports enthusiasts must be prepared for difficulties in all their manifestations.

Mountains represent a rather dangerous and complex terrain, in the vastness of which there is a constant mechanism of gravity, so destroyed rocks move and form plains. Thus, mountains eventually turn into small hills.

There can always be danger in the mountains, so you need to undergo special training and be able to act in extreme situations.

Avalanche detection

Snow avalanches are one of the most devastating, dangerous destructive phenomena of nature.

A snow avalanche is a rapid, sudden, minute-long process of moving snow and ice along mountain slopes, occurring under the influence of gravity, the water cycle and many other atmospheric and natural factors. This phenomenon most often occurs in the winter/spring period, much less often in summer/autumn, mainly at high altitudes.

It is always worth remembering that the harbinger of an avalanche is primarily weather conditions. Hiking in the mountains in bad weather: snowfall, rain, strong wind - is quite dangerous.

Most often, a snow avalanche occurs lasting about a minute, while covering a distance of about 200–300 meters. It is extremely rare to be able to hide or run away from an avalanche and only if it has become known at least 200–300 meters away.

The avalanche mechanism consists of the sloping slope, the avalanche body and gravity.

Sloping slope

Slope level, surface roughness in a big way influence avalanche danger.

A slope of 45–60° usually does not pose a danger, since during snowfalls it is gradually unloaded. Despite this, such places, under certain weather conditions can create avalanche accumulations.

Snow will almost always fall from a slope of 60–65°; in addition, this snow can linger on convex areas, creating dangerous blows.

Slope 90° - the collapse is a real snow avalanche.

Avalanche body

Formed from accumulations of snow during an avalanche, it can crumble, roll, fly, or flow. The type of movement directly depends on the roughness of the lower surface, the type of snow accumulation, and swiftness.

The types of avalanches based on the movement of snow accumulations are divided:

  • to streaming;
  • cloudy;
  • complex.


Gravity

Acts on a body on the surface of the Earth, directed vertically downwards, being the main moving force that promotes the movement of snow accumulations along the slope to the foot.

Factors influencing the occurrence of an avalanche:

  • type of matter composition - snow, ice, snow+ice;
  • connectivity - loose, monolithic, layered;
  • density - dense, medium density, low density;
  • temperature - low, medium, high;
  • thickness - thin layer, medium, thick.

General classification of avalanches

Avalanches of powdery, dry recent snow

Such an avalanche usually occurs during heavy snowfall or immediately after it.

Powder snow is fresh, light, fluffy snow made up of tiny snow flakes and crystals. The strength of snow is determined by the rate of increase in its height, the strength of its connection with the ground or previously fallen snow. It has quite high fluidity, which makes it possible to easily flow around various obstacles. In different cases they can reach speeds of 100–300 km/h.


Avalanches caused by snowstorms

This convergence is the result of snow being transported by a blizzard. Thus, snow is transferred to mountain slopes and negative landforms.

Avalanches of dense dry powder snow

They arise from snow a week or more old, which during this time is compressed and becomes much denser than freshly fallen snow. Such an avalanche moves more slowly, partially turning into a cloud.

Avalanches

They grow after the collapse of snow cornice blocks, which sets them in motion large volume snow.

Dust avalanches

An avalanche is characterized by a huge cloud or a thick coating of snow on trees and rocks. It is created when dry, powdery recent snow melts. The dust avalanche sometimes reaches speeds of 400 km/h. Risk factors are: snow dust, strong shock wave.

Avalanches are layered

They arise through the melting of sheet snow and reach speeds of 200 km/h. Of all snow avalanches, they are the most dangerous.


Avalanches of hard stratified snow

The flow is formed by the descent of solid layers of snow over a weak, loose layer of snow. They consist predominantly of flat snow blocks resulting from the destruction of dense formations.

Soft formation avalanches

A snow flow is formed by the descent of a soft layer of snow along the underlying surface. This type of avalanche is created from wet, settled dense or moderately bound snow.

Avalanches of monolithic ice and ice-snow formations

At the end of winter, snow deposits remain in the mountains, which, under the influence of external factors, become much heavier, turning into firn, which eventually turns into ice.

Firn is snow cemented by frozen water. Formed by changes or temperature fluctuations.

Complex avalanches

Consist of several parts:

  • flying cloud of dry snow;
  • a dense flow of layered, loose snow.

They occur after a thaw or a sharp cold snap, which is the result of snow accumulation and its separation, thereby forming a complex avalanche. This type of avalanche has catastrophic consequences and can destroy a mountain settlement.

Avalanches are wet

They are formed from snow accumulations with the presence of bound water. Occur during the period of accumulation of moisture in snow masses, which occurs during precipitation and thaw.

Avalanches are wet

They arise due to the presence of unbound water in snow accumulations. Appear during a thaw with rain and warm wind. They can also occur by sliding of a wet snow layer over the surface of old snow.

Mudflow-like avalanches

They arise from snow formations with big amount moisture, the moving mass of which floats in a large volume of unbound water. They are the result of long thaws or rains, as a result of which the snow cover has a large excess of water.

The types of avalanches presented are quite dangerous, rapid flows, so you should not think that some are safer than others. Basic safety rules must always be followed.

Avalanche safety

The term avalanche safety refers to a set of actions aimed at protecting and eliminating the tragic consequences of avalanches.

As practice shows, in most accidents, extreme sports enthusiasts themselves are to blame, who, without calculating their own strengths, themselves violate the integrity and stability of the slopes. Unfortunately, fatalities occur every year.

The main rule for safe crossing mountain ranges is complete knowledge of the territory being traversed, with all the dangers and obstacles, so that in an extreme situation one can calmly and carefully leave the dangerous section of the route.

People going to the mountains should know basic rules avalanche safety, know how to use avalanche equipment, otherwise the likelihood of falling under a snowfall and death is very high. The main equipment is avalanche shovels, beepers, avalanche probes, a float backpack, maps, and medical equipment.

Before going to the mountains, it will be useful to take courses on rescue work in case of a collapse, first aid, and making the right decisions to save life. Also an important step is mental training and ways to overcome stress. You can learn this in courses to practice techniques for saving people or yourself.

If a person is a beginner, it will be useful to read books about avalanche safety, which describe different situations, moments, and stages of overcoming them. For a greater understanding of avalanches the best option will personal experience, obtained in the mountains in the presence of an experienced teacher.

Avalanche Safety Basics:

  • psychological attitude and preparation;
  • mandatory visit to the doctor;
  • listening to instructions on avalanche safety;
  • taking with you a sufficient amount of food, small in volume, a spare pair of clothes, shoes;
  • thorough study of the route and upcoming weather conditions;
  • taking a first aid kit, flashlight, compass, equipment on a hike;
  • going to the mountains with an experienced leader;
  • studying information about avalanches in order to have an idea of ​​the degrees of avalanche safety in case of a landslide.


A list of avalanche equipment that you need to be able to work with confidently, quickly, for your own safety and to save victims:

  • tools for searching for victims: transmitter, avalanche ball, beeper, radar, avalanche shovel, avalanche probe, other necessary equipment;
  • tools for checking snow flooring: saw, thermometer, snow density meter and others;
  • tools for rescuing victims: backpacks with inflatable cushions, avalanche breathing apparatus;
  • tools for transporting victims, as well as medical equipment: bags, stretchers, backpacks.

Avalanche slopes: precautions

To avoid getting caught in an avalanche or if there is a high probability of an avalanche situation, you need to know several important rules on avalanche safety and ways of prevention.

  • move on safe slopes;
  • do not go into the mountains without a compass, know the basics of wind direction;
  • move along elevated places, ridges, which are more stable;
  • avoid slopes with snow cornices hanging above them;
  • return along the same road that they walked forward;
  • keep an eye on top layer slope;
  • do tests for the strength of snow cover;
  • fasten the belay well and reliably on the slope, otherwise an avalanche can drag a person with it;
  • take spare batteries for your phone and flashlight on the road, and also have the numbers of all nearby rescue services in your mobile phone’s memory.

If a group or a certain number of people still find themselves under an avalanche, you need to call rescuers, immediately starting the search yourself. In such a situation, the most necessary tools will be an avalanche probe, beeper, and shovel.

Every person who goes to the mountains should have an avalanche probe. This tool performs the function of probing snow during search work. It is a disassembled rod, two to three meters long. During safety courses, a mandatory item is the assembly of an avalanche probe, so that if an extreme situation arises, it can be assembled in the shortest possible time.

An avalanche shovel is indispensable when searching for victims and is necessary for digging out snow. It is more effective when combined with an avalanche probe.

A beeper is a radio transmitter that can be used to track a person covered in snow.

Only with coordinated, quick actions can a comrade be saved. After thorough avalanche safety instruction, a person will be mentally and physically ready to help others.

As a result, I would like to emphasize that hiking in the mountains cannot be carried out with bad weather, in the evening or at night, when crossing a dangerous area, you must definitely use rope belay, be sure to have beepers, flashlights, avalanche shovels and avalanche probes in your arsenal. Some of these tools must necessarily be 3–4 m in length.

By observing all the rules and following the instructions, a person will protect himself from harmful consequences and return home safely.

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