Landslides, snow avalanches. Presentation for the lesson on the topic "avalanches" Download presentation snow avalanches

26.06.202327.05.2017

Avalanches occur when snow stability is disturbed on a slope under the influence of heavy snowfalls, snowstorms, rains, when the adhesion of the snow layer to the underlying surface decreases due to intensive snowmelt or at low temperatures of recrystallization of the snow mass.

Most often, avalanches descend in winter and spring; in the highlands, the danger exists throughout the year. The most dangerous are slopes of medium steepness. On such slopes, the snow cover is sufficient for the formation of avalanches.

On slopes steeper than 60 degrees, the likelihood of avalanches is low, because fresh snow slides down without accumulating. There have been cases of avalanches on slopes of just degrees.

Remember a few rules: stay away from snow ledges. A cornice is a thing like a balcony made of snow, which is formed by the action of the wind. The whole trouble is that, driving along the eaves from above, one may not even guess that this is a cornice until it comes off and turns into an avalanche;

Do not ski on slopes where cracks appear in the snow in front of the skis; if the slope is in any doubt, it is better to leave it alone altogether. But if this is not possible, then before leaving it is necessary to fasten all the clothes, if the skis are without brakes, with straps, then unfasten these straps;

If, nevertheless, the avalanche is already dragging you with it, try to “swim” as it were and stay as close to the surface as possible. If you are in depth, then cover your face with your hands in such a way that there is a supply of air for breathing and snow does not stuff into your nose and mouth;

When you feel that the movement has stopped, try sticking your hand up or at least something. If you can't tell where that top is, which it might be, try spitting. Saliva will flow, of course, down. It is useless to shout, save your strength, the snow dampens any sound very much, the main thing is not to worry - you will definitely be found and rescued.

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Lesson topic: OBZh lesson Grade 7

SNOW, SNOW, SNOW, SNOW... Freshly fallen snow seems to us as light as fluff, its cubic meter weighs only 50-60 kg. A cubic meter of packed snow already weighs 300-400 kg. Spring, saturated with water, the same cubic meter becomes almost twice as heavy.

SNOW - DANGER? YES! Why is snow dangerous? Avalanches Snow eaves and puffs Formation of icing and icicles. Hides dangers Hinders traffic Cause of ice

AVALANCHES Osov - snow landslide. It does not have a specific exit channel. Often a snow slope hundreds of meters long breaks off and slides down. Tray avalanches - carry snow along a strictly defined channel, treeless recesses in the slopes, flumes. Jumping avalanches - freely fall to the bottom of the valley through sheer sections of rocks or ice.

HOW AN AVALANCHES ARE BORN Causes of an avalanche: prolonged snowfall, intense snowmelt, earthquake, explosions causing shaking of mountain slopes and fluctuations in the air, human activity,

The development of an avalanche Loose snow slides over a layer of denser After accelerating, a mass of snow can rise into the air The avalanche picks up speed, sometimes reaching up to 350 km / h

Dry avalanches Dry avalanches are composed of loose snow and move especially fast. They begin with small snow landslides, but due to ground shaking and the occurrence of a shock wave, they quickly increase.

WHO DIES? The statistics of white death victims claims that almost half of them die under small avalanches that travel no more than 200 meters.

An avalanche can carry up to a million tons of snow from a slope and drive an air shock wave in front of it, which, like a bomb explosion, destroys everything in its path. Whoever meets her on the road will be crushed.

Most avalanche victims die very soon, as a snow wall rushing at a speed of 100 km / h and above creates a shock wave; it instantly clogs the lungs and airways of the victim with snow, and the person dies of suffocation. The survivors of this first onslaught are killed when they find themselves inside an avalanche that hurls them against rocks, trees, and other obstacles at great speed.

Victims suffocate or The deeper a person is buried under an avalanche, the less likely it is to get him out of there alive. After all, if a cubic meter of freshly fallen snow weighs only 60-70 kg, then the packed snow mass of an avalanche presses on the body with a weight of more than a ton, does not allow breathing and simply flattens a person. Many avalanche victims suffocate already under a meter layer of snow, as fresh air does not reach them. Therefore, rescuers advise in case of an accident, if possible, press your palms to your face in order to create at least a small space for air, and then the victim, if he is lucky, can hold out until the rescuers arrive. Victims suffocate or get crushed

The account goes on minutes People covered by an avalanche are searched by probes. This must be done quickly, because after 20 minutes half of the victims die. The chance of rescue is increased if rescuers and victims are equipped with "burrowed search devices" that send and receive signals.

WHAT SHOULD YOU KNOW? Avalanche-prone time Within 3-5 days after heavy snowfall Thaw after frost Strong wind In spring from 12 to 18 hours Signs of avalanche danger Slope steepness from 20 to 50 degrees Absence of trees and shrubs Signs of earlier avalanches “Katyshki” Snow cornices and ridges

AVALANCHE HAS OVERCOME Get rid of everything that can serve as a “sail” (skis, board, sticks) Do not resist the avalanche, but try to “swim” to the surface When slowing down, group up with your mouth closed After stopping, determine the top and start freeing up space without stretching your legs

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Landslides, snow avalanches. Grade 7 Completed by the teacher of OBZH MKOU "Naryshkinskaya secondary school" of the Teplo-Ogaryovsky district of the Tula region Kozyr Yuri Dmitrievich.

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The general condition for these natural hazards to occur is: Ground, rock, or snow begins to move down the slope. The territories of our country, where collapses and snow avalanches often occur: the North Caucasus, the Urals, the Sayans, Primorye, Kamchatka, Sakhalin.

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Collapse - the separation and fall of large masses of rocks on steep and steep slopes of mountains, river valleys and sea coasts, occurring mainly due to the weakening of the connectivity of rocks under the pressure of weathering processes, the activity of surface and groundwater. Types of landslides: Rockfalls. Soil collapses. Collapse of glaciers.

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Causes of landslides Mainly anthropogenic (up to 80%) improper work during construction and mining. Natural causes heavy rains.

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An avalanche is a rapid, sudden movement of snow and (or) ice down the steep slopes of mountains, posing a threat to human life and health, causing damage to economic facilities and the natural environment. Avalanches occur in the mountains. The descent of an avalanche is accompanied by the formation of an air pre-shock wave, which produces the greatest destruction.

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Factors affecting the occurrence of avalanches: A lot of snow. Slope, the slope of which exceeds 14 degrees (if the slope angle is 30 - 40 degrees, then an avalanche is inevitable). The presence of an open slope with a length of 100 - 500 meters.

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“Even in the last century, in the Alps, people covered with snow were helped to discover large strong St. Bernard dogs, named after the high-mountainous monastery of St. Bernard, where they were bred. Near Paris, at a special dog cemetery, a monument to St. Bernard Barry, who saved 40 people, was erected. These good-natured large dogs have found more than 2,000 people in the mountains. Now the St. Bernards have been replaced by East European Shepherds.”

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Text content of presentation slides: Snow avalanches Grade 7 Developed by OBZH teacher Elena Igorevna Koshkina Avalanche is a fast, sudden movement of snow and (or) ice down the steep slopes of mountains, posing a threat to human life and health, causing damage to economic facilities and the environment. Avalanches form on treeless mountain slopes, the slope of which is greater than 14°. This is a critical slope at which the snow constantly slides down. The avalanche starts when the layer of fresh snow is 30 cm or the thickness of the old snow is more than 70 cm. Avalanche speed can reach from 20 to 100 m/s. Thus, an avalanche is a mass of snow falling or sliding off the steep slopes of mountains and moving at an average speed of 20-30 m/s. The fall of a snow avalanche is accompanied by the formation of an air pre-avalanche wave, which produces the greatest destruction. The occurrence of avalanches is possible in all mountainous areas where snow cover is established. Avalanche-prone regions in Russia are the Kola Peninsula, the Urals, the North Caucasus, Eastern and Western Siberia, and the Far East. The formation of avalanches occurs in an avalanche focus, which is a section of a slope and its foot, within which an avalanche moves. The causes of an avalanche are prolonged snowfalls, intense snowmelt, and explosions during road construction. The impact force of a descending avalanche can reach from 5 to 50 tons per square meter. Descending avalanches can cause the destruction of buildings, engineering structures, cover roads and mountain paths with snow. Residents of mountain villages, tourists, climbers, geologists and other people who find themselves in the mountains and are captured by an avalanche can be injured and find themselves under a layer of snow. Protection of the population from the consequences of avalanchesForecasting is of great importance for protecting the population from the consequences of snow avalanches. For this, a special monitoring system operates. The data received from the monitoring system is processed and presented in the form of forecasts. Based on the forecasts received, preventive measures are planned and implemented. In conditions of the threat of avalanches, they organize control over the accumulation of snow in avalanche-prone directions, and cause artificial descent of emerging avalanches during the period of their least danger. Protective structures are being built in avalanche-prone directions, rescue equipment is being prepared and rescue work is being planned. The population is being warned about the danger of avalanches. Rules of conduct in avalanche zones Information about avalanches can be found in the search and rescue service of the EMERCOM of Russia. And if you are going to be in an avalanche zone, report your intentions (register) to the search and rescue service of the Russian Emergencies Ministry. Avoid places where avalanches are possible. They most often descend from slopes with a steepness of more than 30 °; if the slope is without shrubs and trees - with a steepness of more than 20 °. With a steepness of more than 45 °, avalanches come down almost every snowfall. When an avalanche comes down, if there is a decent distance from you to it, you need to quickly leave the avalanche path to a safe place or take cover behind a rock ledge, in a recess. If it is impossible to escape from an avalanche, get rid of all things and take a horizontal position; cover your mouth and nose with a mitten or scarf so as not to suffocate; in the snow mass, move your arms and legs (depict swimming) to stay on the surface; try to clear a layer of snow in front of you to make breathing easier. When the avalanche has stopped, try to move up. Do not lose your temper, do not fall asleep, save your strength, remember that they are looking for you (there are cases when people were rescued from under the avalanche on the fifth and even on the thirteenth day). Check yourself1. Where does the formation of avalanches occur?2. List the causes of avalanches.

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