Volcanic eruptions. Memo on the actions of the population during volcanic eruptions and ash emissions

A VOLCANO is a geological formation that occurs above channels and cracks in the earth's crust, along which molten rocks (lava), ash, hot gases, water vapor and rock debris erupt onto the earth's surface. There are active, dormant and extinct volcanoes, and in shape - central, erupting from the central outlet, and fissure, the apparatus of which has the form of gaping fissures and a number of small cones.

Modern volcanoes are located along large faults and tectonically mobile regions. Danger to humans is represented by flows of magma (lava), falling stones and ash ejected from the crater of a volcano, mud flows and sudden flash floods. A volcanic eruption can be accompanied by an earthquake.

HOW TO PREPARE FOR A VOLCANO Eruption

Watch out for warnings about a possible volcanic eruption. You will save your life if you leave dangerous territory in time. Close all windows, doors and smoke dampers when you receive an ash warning. Put cars in garages. Place animals indoors. Stock up on self-powered lighting and heat sources, water, food for 3-5 days.

When you are in the area of \u200b\u200bthe volcano, observe your own safety measures: in the immediate vicinity of the volcano, an excess of the maximum permissible gas concentration during vapor-gas emissions can be observed. When approaching a volcano, there is a possibility of falling into ash falls, which can lead to allergic reactions, ash getting into the mechanisms of cars and their failure.

HOW TO ACTION DURING A VOLCANO Eruption

Protect your body and head from rocks and ash. Volcanic eruptions can be accompanied by violent floods, mudflows, flooding, so avoid river banks and valleys near volcanoes, try to stay in high places so as not to get into the flood or mudflow zone.

Rules of conduct for ash fall:

if ash is inhaled and gets into the lungs, allergic reactions are possible, therefore, if ash falls, it is necessary to close doors and windows, try not to go outside without needing to;

if ash will penetrate into the home, family members should wear respirators or gauze bandages, or breathe through a towel;

cover the computer, stereo system and other equipment with plastic wrap or thick cloth and do not use during the ash fall;

if you worked outside during an ash fall, do not bring clothes into the house.

HOW TO ACTION AFTER VOLCANO Eruption

Cover your mouth and nose with a gauze bandage to prevent inhalation of ash. Wear safety glasses and clothing to avoid burns. Do not try to drive the car after the ash has fallen out - it will damage it.

After ashfall, you must:

put on a respirator and goggles before cleaning the house from ash;

clean the roof, gutters and other areas of the house where ash may have accumulated to prevent overloading and destruction;

renew the supply of necessary items that you should have in case of ashfall.

It is recommended to refrain from hiking to the foot of erupting volcanoes, this can threaten your life, since in the immediate vicinity of the volcano, the maximum permissible gas concentration may be exceeded during vapor-gas emissions.

Volcano- the place where the red-hot substance of the earth's interior - magma - breaks out to the surface.

The interior of the Earth is constantly in a heated state. Molten rocks or magma accumulate at depths of 10 to 30 km. During tectonic processes, cracks form in the earth's crust. Magma rushes along them to the surface under the pressure of water and gas vapors, when it comes out to the surface, magma pours out in the form of lava. From the vapors and gases released into the atmosphere, sediments of volcanic rock, called tephra, settle to the ground.

According to the degree of activity, volcanoes are classified into active, dormant and extinct. The active ones include those that erupted in historical time. The extinct ones, on the contrary, did not erupt. Dormant ones are characterized by the fact that they periodically manifest themselves, but it does not come to an eruption.

Several hundred active volcanoes are currently known around the globe. Most of them are located on the shores of the Pacific Ocean, including in Russia in Kamchatka and the Kuril Islands.

The most dangerous phenomena accompanying volcanic eruptions:

 lava flows,

 fallout of tephra,

 volcanic mud flows,

 volcanic floods,

 scorching volcanic cloud,

 volcanic gases,

 volcanic ash ejection.

Lava flows - these are molten rocks with a temperature of about 1000 0C. The flow rate usually does not exceed 1 km / h.

Tephra consists of fragments of solidified lava. Its loss leads to the destruction of animals, plants, and in some cases to the death of people.

Mud streams - These are thick layers of ash on the slopes of the volcano, which are in an unstable position. When new portions of ash fall on them, they slide down the slope. In some cases, ash becomes saturated with water, resulting in volcanic mud flows. Their speed can reach several tens of kilometers per hour. Due to the high speed of movement, it is difficult to carry out rescue operations and evacuate the population.

Volcanic floods ... When glaciers melt during volcanic eruptions, huge amounts of water can form very quickly, leading to floods. For example, the height of the summit, where the main crater of the Klyuchevskaya Sopka volcano in Kamchatka is located, is 4750 m.At this height, powerful glaciers are formed, which at strong eruptions melt, and then rushing streams of water rush from the mountain.

Scorching volcanic cloud ... It is a mixture of hot gases and tephra. Its damaging effect is due to the appearance of a shock wave (strong wind), propagating at a speed of up to 40 km / h, and a heat roll with a temperature of up to 1000 0С.

Volcanic gases ... Eruptions are always accompanied by the release of gases mixed with water vapor - a mixture of sulphurous and sulfuric oxides, hydrogen sulphide, hydrochloric and hydrofluoric acids in a gaseous state, as well as carbon dioxide and carbon monoxide in high concentrations that are fatal to humans. The release of these gases can continue for a very long time, even after the volcano has stopped ejecting lava and ash.

An intense release of volcanic ash impairs visibility, creates a great danger for aviation flights (ash ingress into the engine), in large quantities ash accumulates on rooftops.

Protective measures:

 Choosing a place of residence at a distance from active volcanoes.

 Evacuation of the population.

 Impact on the lava flow: deflection of the flow, dividing it into several small ones, cooling, creating barriers.

 Breaking the crater wall (by bombardment) and directing the lava flow in a safe direction.

 Deviation in a safe direction of mud flows.

 Dumping volcanic ash from rooftops.

Question. Landslides, landslides, mudflows, avalanches.

Mud - a rapid, turbulent mud or mud-stone stream, consisting of a mixture of water, sand, clay and rock debris, which suddenly appears in the basins of small mountain rivers. The reason for its occurrence is intense and prolonged downpours, rapid melting of snow or glaciers, breakthrough of water bodies, less often earthquakes, volcanic eruptions.

Possessing a large mass and high speed of movement (up to 40 km / h), mudflows destroy buildings, roads, power lines, lead to the death of people and animals. A steep front of a mudflow wave with a height of 5 to 15 m forms the "head" of a mudflow (the maximum height of a mud flow shaft can reach 25 m), the length of mudflow channels ranges from several tens of meters to several tens of kilometers.

Mudflows are especially active in the North Caucasus. Due to the negative role of the anthropogenic factor (destruction of vegetation, development of quarries, etc.), mudflows began to develop on the Black Sea coast of the North Caucasus (Novorossiysk region, Dzhubga - Tuapse - Sochi section).

Protective measures:

 Strengthening mountain slopes (planting forests);

 Anti-mudflow dams, dams, ditches;

 Periodic descent of water from mountain reservoirs;

 Construction of protective walls along river beds;

 Reducing the rate of snow melting in the mountains by creating smoke screens.

 Catching mud flows into special pits located in river beds.

 Effective warning and warning system.

Collapse - this is a rapid separation (separation) and a fall in the mass of rocks (earth, sand, clay stones) on a steep slope due to the loss of stability of the slope, weakening of the connectivity, integrity of rocks.

The collapse occurs under the influence of weathering processes, movement of ground and surface water, washout or dissolution of rocks, soil vibrations. landslides most often occur during rains, melting snow, during blasting and construction work.

The striking factors of the collapse are the fall of heavy masses of rocks that can damage, crush even strong structures or fill them with soil, blocking access to them. Another danger of landslides is the possible damming of rivers and the collapse of the shores of lakes, the waters of which, in the event of a breakthrough, could cause floods or mud flows.

Signs of a possible collapse are numerous cracks in sheer rocks, overhanging blocks, the appearance of individual fragments of rocks, blocks, separated from the main rock.

Landslide - sliding displacement of rock masses down the slope under the influence of gravity; arises, as a rule, due to slope washout, waterlogging, seismic shocks and other factors.

The causes of landslides can be the following factors.

1. Natural:

earthquakes;

waterlogging of slopes with precipitation;

increase in slope steepness as a result of water washout;

weakening of the strength of hard rocks during weathering, leaching or leaching

the presence of softened clays, quicksands, fossil ice in the soil:

2. Anthropogenic:

deforestation and shrubs on the slopes. Moreover, deforestation can occur much higher than the place of the future landslide, but the water will not be retained by the plants at the top, as a result of which the soil becomes waterlogged far below;

blasting operations, which are, in fact, a local earthquake and contribute to the development of cracks in the rocks;

plowing slopes, excessive watering of orchards and vegetable gardens on the slopes;

destruction of slopes by foundation pits, trenches, road cuts,

clogging, clogging, blockage of groundwater outlets;

construction of housing and industrial facilities on the slopes, which leads to destruction of the slopes, an increase in gravity directed down the slope.

The damaging factor of landslides are heavy masses of soil, filling or destroying everything in its path. Therefore, the main indicator of a landslide is its volume, measured in cubic meters.

Unlike landslides, landslides develop much more slowly, and there are many signs that allow early detection of an incipient landslide.

Signs of an incipient landslide:

breaks and cracks in the ground, on the roads;

violation and destruction of underground and ground communications;

displacement, deviation from the vertical of trees, poles, supports, uneven tension or wire breakage;

curvature of the walls of buildings and structures, the appearance of cracks on them;

change in water level in wells, wells, in any water bodies.

Landslide prevention measures include: monitoring the condition of slopes; analysis and forecasting of the possibility of landslides; carrying out complex engineering protective works; training of people living, working and having a rest in the danger zone, the rules of life safety.

Snow avalanches arise as a result of the accumulation of snow on mountain peaks during heavy snowfalls, strong blizzards with a sharp drop in air temperature. Avalanches can also descend during the formation of deep rime, when a loose layer (snow-quicksand) appears in the thickness of the snow.

Snow avalanches are annually observed in the mountainous regions of the North Caucasus, Sakhalin, Kamchatka, Magadan region, in the Khibiny, in the Urals.

Most avalanches descend along specific trays - narrow hollows on steep mountain slopes. Along these hollows, 200–300, and sometimes up to 500 thousand tons of snow can simultaneously fall.

In addition to trough avalanches, there are main and jumping avalanches. The main avalanches slide off the mountain slopes in undefined places, as a rule, they are small and do not pose a particular danger. Jumping avalanches are trough avalanches that meet “springboards” on their way and “jump” over them with great force, acquiring an increasing speed of movement, and as a result, the force of destruction increases.

Quite often, avalanches occur suddenly and begin their initial movement silently. When avalanches move in narrow mountain gorges, an air wave growing in strength moves ahead of them, bringing even greater destruction in comparison with the falling mass of snow. The repeated avalanches leave deep footprints in the mountainous landscape. Avalanches often fall into river beds and block them, forming dams for a long time.

Avalanche danger is caused by abrupt weather changes, heavy snowfalls, heavy blizzards, and rains. To prevent avalanche danger, there is a special mountain avalanche service.

Catastrophic snow avalanches in the world occur on average at least once every two years, and in some mountainous regions - at least once every 10–12 years.

When people get caught in an avalanche, it should be remembered that a person, being covered with avalanche snow, can stay alive for only a few hours, and the chance of survival is higher, the thinner the layer of snow above him. Among people who have been in an avalanche for no more than 1 hour, up to 50% can survive, after 3 hours the probability of surviving does not exceed 10%. Therefore, work to rescue people caught in an avalanche should begin even before the arrival of the rescue team.

When a covered one is found, first of all, the head is freed, the mouth, nose, ears are cleared of snow; then, carefully (taking into account the possibility of fractures), they remove it from under the snow, transfer it to a place protected from the wind, wrap it in dry clothes, give a hot drink, and in the absence of signs of life, proceed to artificial ventilation and other resuscitation measures.

D actions of the population under the threat of landslides, landslides, mudflows

The population living in landslide, mudflow and landslide-prone zones should know the foci, possible directions of movement and the main characteristics of these dangerous phenomena. The population of mountainous regions is obliged to strengthen their homes and territories on which they were built, as well as to participate in the construction of protective hydraulic engineering and other protective engineering structures.

The population is alerted about natural disasters through sirens, radio and television broadcasts, as well as through local warning systems that directly link the hydrometeorological service unit with settlements in hazardous areas.

Before leaving the house or apartment during the evacuation, it is necessary to remove the property from the yard or balcony into the house, the most valuable property that cannot be taken with you, the doors, windows, ventilation and other openings must be tightly closed from the effects of moisture and dirt, the electricity must be turned off , gas and water.

Flammable and toxic substances should be taken out of the house and, if possible, buried in a hole or hidden in a cellar.

In all other respects, citizens must act in accordance with the procedure established for an organized evacuation.

If there was no warning about the danger or it was made just before the natural disaster, then residents, not caring about property, should quickly go to a safe place. Natural places for salvation from mudslides or landslides are mountain slopes and hills, which are not prone to landslide, landslide process or flooding by mudflows. When climbing safe slopes, you should not use valleys, gorges and excavations, since side channels of the main mudflow can form in them.In the case when people, buildings and structures find themselves on the surface of a moving landslide area, leave the premises and move upwards as much as possible, being careful when braking a landslide of stones, fragments of structures, earthen ramparts, and talus rolling down from its rear part. When a fast moving landslide is stopped, a strong shock is possible. This poses a great danger to people on the landslide.

Question. Wind speed classification. Definition of the concept of "storm". Types of storms. Definitions of the terms "hurricane", "cyclone" and "tornado". Types of hurricanes

Wind is the movement of air parallel to the earth's surface, resulting from an uneven distribution of heat and atmospheric pressure and directed from a high to a low pressure zone.

Many words are used to denote the movement of the wind: tornado, storm, hurricane, storm, typhoon, cyclone and many local names. To systematize them all over the world, they use the Beaufort scale, which makes it possible to very accurately assess the strength of the wind in points (from 0 to 12) by its effect on ground objects or by the roughness of the sea. This scale is also convenient in that it allows, according to the features described in it, to quite accurately determine the wind speed without instruments.

From the group of meteorological and agrometeorological phenomena of natural origin, extremely dangerous natural disasters are storms (storms), hurricanes (typhoons), tornadoes (tornadoes), cyclones, which are extremely fast and strong, often catastrophic air movement that causes the destruction of buildings, death of people and animals.

The wind speed is distinguished: weak wind - up to 5 m / s, strong - up to 10 m / s, very strong 15-18 m / s, storm (storm) - 18-29 m / s, hurricane (typhoon) - over 29 m / s, sometimes reaching 120-210 m / s.

Storm - very strong and prolonged wind, causing great destruction on land and roughness at sea (storm). Depending on the season and the involvement of various particles in the air flow, dust, dust-free, snow and squall storms are distinguished.

Dust (sand) storms accompanied by the transfer of large quantities of soil and sand particles. They arise in deserts, semi-desert and plowed steppes and are capable of transferring millions of tons of dust over hundreds of kilometers and filling up areas of several thousand kilometers.

In Russia, the border of the spread of such storms goes through the Saratov and Samara regions, the cities of Ufa and Orenburg, the foothills of Altai.

Dustless storms characterized by the absence of dust entrainment into the air flow and a relatively smaller scale of destruction and damage.

Snow storms occur in winter and move huge masses of snow through the air. Their duration is from several hours to several days. They have a relatively narrow band of action. They are more often in Siberia.

Squall storm characterized by an almost sudden onset, the same quick end, a short duration of action and a huge destructive force.

Hurricane is a vortex with a huge speed of movement of air masses and low atmospheric air pressure in the central part. Air speed can exceed 120 m / s in an area with a diameter of 500–1000 km and a height of up to 10–12 km. Hurricanes occur in areas of contact between warm and cold air masses with the most pronounced temperature contrasts and are accompanied by strong cloudiness, heavy rains, thunderstorms and hail. Hurricanes have different names: in the Philippines, begvis; in Australia - willy-willy; hurricanes in North America.

Most often hurricanes occur in regions with tropical climates, where they are most destructive. Powerful hurricanes destructive force in some cases can be equated with earthquakes. In Russia, the most likely region for hurricanes is the Pacific coast. At the same time, hurricane winds and heavy torrential rains are often observed in the coastal regions of the Arctic seas, the seas of the Far East, the Black Sea, as well as in the regions of the Volga region and the republics of the North Caucasus. Hurricanes often cause floods as a result of intense rainfall, which took place in the Primorsky Territory. As a result of hurricanes, structures are destroyed, fires break out, people die, a huge number of the population needs medical care.

Cyclone- a giant atmospheric vortex, in which the pressure decreases towards the center, air currents circulate around the center counterclockwise (in the Northern Hemisphere) or clockwise - in the Southern Hemisphere.

Cloudy weather prevails during the cyclone. The greatest danger is represented by tropical cyclones with storm and hurricane winds and the force of air movement, respectively, 9 and 12 on the Beaufort scale. The wind speed with a strong upward movement sometimes reaches 70 m / s, and its individual gusts - 100 m / s, dense continuous clouds develops with heavy rainfall (up to 1000 mm per day or more) and thunderstorms.

In Southeast Asia, tropical cyclones are called typhoons, and in the Caribbean, hurricanes. During thunderstorms, atmospheric vortices often arise, spreading down to the very surface of the earth. Their diameter can be tens of meters above the sea and hundreds above land. Such a whirlwind is called a tornado (a thrombus in Western Europe, a tornado in the USA).

Tornadois the most destructive atmospheric phenomenon. It is a huge vortex with a vertically directed axis of rotation, resembling a funnel with a "trunk" extended upward. The air in a tornado rotates at a speed of several tens of meters per second, simultaneously rising in a spiral to an altitude of 800-1500 m. The tornado travels 40-60 km, moving with the cloud, accompanied by thunderstorms, rainstorms, hail, is capable of causing great destruction.

Tornadoes are formed when the atmosphere is unstable, when the air in its lower layers is very warm, and in the upper layers it is cold, while a powerful vertical movement of air masses occurs. Inside the vortex flow, a low atmospheric pressure is formed, so the tornado draws in dust, water and all objects on the way of its movement like a giant vacuum cleaner, lifting them high up and carrying them over long distances.

Protective measures after receiving a "storm warning":

 Alerting the population about the time of the hurricane approach.

 Transition to safe modes of operation of various industries.

 Reduction of stocks of hazardous substances at enterprises, increasing the reliability of their storage.

 Preparation of shelters, basements to protect the population.

 Partial evacuation of the population.

 Increasing the security of buildings, structures and other human habitats (close windows, doors, ventilation openings, cover glass, windows and shop windows, protect with shutters and shields).

 Fix fragile structures and objects or remove, free the balconies from things.

 Creation of supplies of food and water, items to ensure life.

When volcanic eruptions emit gases, liquids and solids at high temperature and high velocity. This often becomes the cause of the destruction of buildings and the death of people.

The constant rumble and rumble, reminiscent of an artillery cannonade, a column of ash thrown at a great height make an indelible impression.

As told correspondent G. Vdovin about the Kamchatka eruption in mid-December 2012: ".. The sound is as if some giants are loading giant metal sheets, all the time dropping them ..."

Lava flow, rain of hot debris and steam have tremendous destructive power.

The only defense against volcanoes is a general evacuation, so the population must be familiar with the evacuation plan and implicitly obey the authorities if necessary.

If evacuation is not required, follow these simple safety measures:

* don't panic, stay at home by closing doors and windows
* if anyone needs help, then leave the house wearing warm clothes, preferably non-flammable (not made of synthetics), protecting your nose and mouth with a damp cloth
* do not hide in basements, so as not to be buried under a layer of mud
* stock up on water
* make sure that the falling of hot stones does not cause fires, which should be extinguished immediately
* as soon as possible - clean the roofs from ash

Of course, the manifestation of this element is an extremely rare phenomenon. However, not a few inhabitants of the planet Earth live on a "powder keg".

And for recent times a lot happened volcanic eruptions in different parts of our planet.

Indonesia - here the volcano continues to remind of itself Sinabung …
Sicily, where the next eruption of Mount Etna still keeps residents of the surrounding districts at bay ...

Volcano Karymsky on the Kamchatkathrew a column of ash to a height of 3 km…
AND guatemalan Fuego continues to rage to this day. In just a day, one of the local observation stations recorded up to 8-14 eruptions hourly. This indicates a fairly high degree of lava activity inside the mountain ...

Like others natural disasters, a volcanic eruption often happens unexpectedly and a person has no choice but to respond promptly to this incident. The danger posed by active volcano, is inversely proportional to the distance to the crater. That is, those who live close to the smoking mountain should worry most of all.

Most powerful eruptions accompanied by earthquakes, which, as it were, warn all living things around that danger is very likely in the near future. It is in such a situation that emergency services alert the population about a potential volcanic eruption, hinting thereby to pack up and move out.

So, what are the basic rules of behavior during a volcanic eruption?

1. If you live in close proximity to a volcano, constantly monitor the messages about its condition, prepare a hot backpack with the most necessary things and documents. He must always be ready.

2. When you receive a warning about an eruption or possible subsequent complications (flood, mudflow), preserve your home, collect all the most necessary things and look for a shelter, preferably away from fire-breathing, ash-erupting, lava slopes until better times, until the danger of a volcanic eruption passes.

3. If you did not have time to fly to the other end of the world and the eruption took you by surprise, be sure to protect your body and head from ash and stones. The head will be protected by almost everything, from wooden structures to cardboard, a gauze bandage or a respirator will take care of breathing. Well, if you are 100% prepared, you can take out your trophy gas mask, but remember that it is very difficult to recognize you in this form.

4. Volcanic eruptions are often accompanied by floods, mudflows, flooding. Therefore, avoid river valleys, especially near a volcano, try to climb as high as possible so as not to become a victim of water flows or mudflows.

5. If during a volcanic eruption you leave the danger zone by transport, choose a route opposite to the direction of the wind. This will help you avoid an unpleasant date with ash later on.

6. Average speed of lava movement - 40 km / h. It's quite possible to escape from this hot thing. As in the case of ash, it is worth choosing a direction of movement perpendicular to the flow.

7. If health is dear to you, wear as much warm clothes as possible. This will protect your body from acid, which will be produced in large quantities as a result of the SO2 reaction with the environment.

8. After the eruption, do not rush to return to your home. Messages of emergency services should serve as a signal. If possible, spend a few days away from the area affected by the volcanic eruption.

9. Upon returning to your home, try not to open the windows for as long as possible (2-3 weeks), until the ash has completely disappeared from environment... Remember to protect your respiratory system.

Plan

Introduction

1. Definition of emergency

2. Volcano

2.1. Volcanic eruptions

2.2. Danger to humans during a volcanic eruption

2.3. Actions for a volcanic eruption :

INTRODUCTION

Modern man throughout his life he is in various environments: social, industrial, local (urban, rural), household, natural, etc.

A person and his environment form a system consisting of many interacting elements, which has an orderliness within certain boundaries and has specific properties. Such interaction is determined by many factors and affects both the person himself and the corresponding environment of his habitat. This influence can be, on the one hand, positive, on the other - at the same time negative (negative).

The negative impact of environmental factors is manifested mainly in emergency situations. These situations can result from both natural Disastersand human production activities. In order to localize and eliminate negative impactsarising in emergency situations, special services are created, legal bases are developed and material resources are created for their activities. It is of great importance to educate the population on the rules of behavior in such situations, as well as to train special personnel in the field of life safety.

1. DEFINITION OF EMERGENCY

EMERGENCY - this is the situation in a certain area, resulting from an accident, dangerous natural phenomenon, catastrophe, natural or other disaster, which may or has resulted in human casualties, damage to human health or the environment, as well as significant material losses and disruption of living conditions.

Emergencies are classified by the nature of the source and by the magnitude.

Consider an emergency - a volcanic eruption.

2. VOLCANO Is a geological formation that appears above channels and cracks in the earth's crust, along which molten rocks (lava), ash, hot gases, water vapor and rock fragments are erupted onto the earth's surface. There are active, dormant and extinct volcanoes, and in shape - central, erupting from the central outlet, and fissure, the devices of which have the form of gaping fissures and a number of small cones. The main parts of the volcanic apparatus:

· Magma chamber (in the earth's crust or upper mantle);

· Vent - outlet channel through which magma rises to the surface;

· Cone - an elevation on the surface of the Earth from the products of a volcanic ejection;

· Crater - a depression on the surface of a volcano's cone.

2.1 Volcanic eruptions

Volcanic eruptions are a sufficiently dangerous geological phenomenon. The processes occurring in the earth's thickness and causing eruptions have not yet been fully understood.

It is generally accepted that top part The mantle is in a state close to molten; therefore, even a slight decrease in pressure leads to its complete melting. Molten rock (magma), being lighter than the surrounding rocks, slowly rises to the surface of the earth. Most often this occurs along faults crust.
The second reason causing eruptions is the presence of local radioactive sources. The few continental volcanoes located far from the boundaries of the lithospheric plates are caused by just such local sources of radioactive heat or hot spots in the mantle.

During eruptions, the following is most often observed: deformation and shaking of the earth's surface; emission, fallout of eruption products; movement of lava, mud, stone flows; gravitational displacement of rocks. Breaks out into the atmosphere a large number of vapors and gases, leading to chemical pollution of the environment, with the potential danger of large-scale fires. Often, lakes are formed in craters during a dormant period, then during an eruption, water-mud flows represent the main danger, even greater than lava flows (due to high speeds of movement along the slopes).

Most often, volcanic eruptions begin with the release of a column of black smoke or ash from the crater up to 5 km high, which quickly spreads into the air in the form of a huge cloud; cracks appear on the slopes and on the crater, through which suffocating gases or hot water are released.

This is usually followed by a heavy thunderstorm rain. At the same time, large and small red-hot fragments of rocks are thrown out of the crater, ash falls from the clouds, which covers the slopes of the volcano and the surrounding area.
Then the eruption of lava from the mouth of the volcano begins.

Over millions of years, lava layers form volcanic mountains... They are often quite tall and cone-shaped with a crater at the top. Many volcanoes are found on the seabed.

Volcanoes are formed seismically active zones the earth's crust. The lithosphere is split into huge blocks, or plates. Under the pressure of powerful underground forces, these plates move continuously. In some places, their movement leads to the emergence of mountain ranges, in other edges of the plates are drawn into deep depressions.

Lava types. The temperature of the lava can reach 1000 ° C, and the flow velocity is 165 m / s. Not all volcanoes erupt in the same way. The nature of the eruption is determined by the types of gases and the amount of water contained in the magma.

The Hawaiian, or thyroid, type of volcano is characterized by a calm nature of eruptions. Red-hot liquid and flowing lava pours out of the crater. The gases contained in the magma easily escape outside, throwing out fiery fountains of shop lumps. This type of eruption is named for two hawaiian volcanoes - Mauna Loa and Kilauea.

With the strombolian type, gases are released into the atmosphere by small explosions. With each explosion, hot lumps of semi-liquid lava fly into the air, which fall to the ground with bombs and roll down the slopes, turning into a real rockfall. This type is named for the Italian volcano Stromboli, which erupts regularly to this day.

Vulcan type. Italian mountain Vulcano gave its name to a much more dangerous type of eruption. The volcanic eruption scatters huge chunks of lava several kilometers from the crater. The very viscous magma prevents the free escape of gases, and they accumulate inside under such tremendous pressure that powerful explosions are heard from time to time.

The Plinian type is considered the most explosive.

Deadly dust. During Plinian eruptions, the underground forces that broke free are able to overcome the sound barrier and throw out huge columns of ash, stones and gases, reaching a height of 30 km. These debris, called pyroclasts, burst into small particles in the air, covering everything in a thick layer of deadly dust.

Sometimes a Plinian eruption reaches such power that it destroys the volcano itself. At best, the walls of the main vent sink inward, forming side craters, or calderas ("boiling cauldron" in Spanish).

Volcanoes are divided into active, asleep and extinct .

To the asleep Volcanoes belong to the eruptions of which there is no information, but they have retained their shape and local earthquakes occur under them.

Extinct volcanoes - these are various volcanoes without any volcanic activity.

Volcanic eruptions are long-term or short-term. The products of the eruption (gaseous, liquid and solid) are thrown out to an altitude of 1-5 km and transported over long distances. The concentration of volcanic ash is sometimes so great that darkness sets in, similar to night. The volume of the erupted lava reaches tens of cubic kilometers.

2.2 Danger to humans during volcanic eruption

Danger to humans is represented by flows of magma (lava), falling stones and ash ejected from the crater of a volcano, mud flows and sudden flash floods. A volcanic eruption can be accompanied by an earthquake. The striking factors in volcanic eruptions are: shock wave; flying fragments, stones, trees, parts of structures; ash; volcanic gases; lava moving along the slope at a speed of up to 80 km / h and burning everything in its path.

Secondary damaging factors: tsunamis, fires, explosions, floods and landslides. Most often, people and animals in areas of volcanic eruptions die from injuries, burns of the upper respiratory tract, asphyxiation and eye damage. In areas of volcanic eruptions, epidemiological surveillance is established.

2.3 Actions for a volcanic eruption :

Having received a warning about a possible volcanic eruption, leave the dangerous territory in time.

You need to get away from the lava flows by the shortest path, that is, perpendicular to the direction of their movement

If escape does not help (the average flow rate of hot magma is about 40 kilometers per hour, so it is quite possible to leave it, but here you also need to soberly assess your chances, if the lava catches up with you, then you are covered), then instantly look for a shelter, not a basement type, although a cave located on a hill can pass for it. If this is not possible, stock up on self-powered lighting and heat sources, water, food for 3-5 days;

Close all windows, doors and smoke dampers. Move the animals indoors. Use a moistened gauze bandage to protect the respiratory tract from ash;

Wear safety glasses and clothing to protect your body and head from stones, ash, burns; Dress as if it is 50 degrees below zero outside, several layers of dense (overcoat, cotton blankets, etc.), preferably non-combustible clothing, will protect you from SO2, or rather from acid, which sulfur dioxide will form in huge quantities.

Avoid river banks and valleys near volcanoes, try to stay in high places, as flooding and mudflows are possible.

If you're lucky and your home has survived the devastating aftermath of a volcanic eruption, get ready to spend the next few days, and maybe the entire week. Do not open windows for as long as possible.

List of used literature

1. Emergencies and protection from them.

Comp. A. Bondarenko. Moscow, 1998

2. Emergencies.

Energy: economics, technology, ecology, 2000

3. Causes and consequences of natural disasters and catastrophes.

Meshkov N. Fundamentals of the safety of life. 1998 year

4. Safety problems in emergency situations. 1999 year