Where do volcanic eruptions occur? Volcanic eruptions are dangerous natural disasters for humans

Volcanic eruption diagram

When a volcano awakens and begins spewing streams of red-hot lava, one of the most amazing natural phenomena occurs. This happens when there is a hole, crack or weak spot in the earth's crust. Molten rock, called magma, rises from the depths of the Earth, where there are incredibly high temperatures and pressures, to its surface. The magma that flows out is called lava. Lava cools, hardens, and forms volcanic, or igneous, rock. Sometimes lava is liquid and flowing. It oozes from the volcano like boiling syrup and spreads over a large area. When such lava cools, it forms a hard cover of rock called basalt. With the next eruption, the thickness of the cover increases, and each new layer of lava can reach 10 m. Such volcanoes are called linear or fissure, and their eruptions are calm.

During explosive eruptions, the lava is thick and viscous. It pours out slowly and hardens near the crater of the volcano. With periodic eruptions of this type of volcano, a high conical mountain with steep slopes appears, the so-called stratovolcano.

The lava temperature can exceed 1000 °C. Some volcanoes emit clouds of ash that rise high into the air. Ash can settle near the volcano's mouth, and then an ash cone appears. The explosive force of some volcanoes is so great that huge blocks of lava the size of a house are thrown out. These "volcano bombs" fall near a volcano.

Along the entire mid-ocean ridge, lava seeps up from the mantle from many active volcanoes onto the ocean floor. From deep-sea hydrothermal vents located near volcanoes, gas bubbles and hot water with minerals dissolved in them erupt

An active volcano regularly spews lava, ash, smoke and other products. If there is no eruption for many years or even centuries, but in principle it can happen, such a volcano is called dormant. If a volcano has not erupted for tens of thousands of years, it is considered extinct. Some volcanoes emit gases and streams of lava. Other eruptions are more violent and produce huge clouds of ash. More often than not, lava oozes slowly onto the Earth's surface over a long period of time without any explosions occurring. It pours out from long cracks in the earth's crust and spreads, forming lava fields.

Where do volcanic eruptions occur?

Most volcanoes are located on the edges of giant lithospheric plates. There are especially many volcanoes in subduction zones, where one plate dives under another. When the lower plate melts in the mantle, the gases and fusible rocks it contains “boil” and, under enormous pressure, burst upward through cracks, causing eruptions.

Cone-shaped volcanoes, typical of land, look huge and powerful. However, they account for less than one hundredth of all volcanic activity on Earth. Most of the magma flows to the surface deep underwater through cracks in the mid-ocean ridges. If underwater volcanoes erupt large enough amounts of lava, their peaks reach the surface of the water and become islands. Examples are the Hawaiian Islands in the Pacific Ocean or the Canary Islands in the Atlantic.

Rainwater can seep through cracks in the rock into deeper layers, where it is heated by magma. This water comes to the surface again in the form of a fountain of steam, splashes and hot water. Such a fountain is called a geyser.

Santorini was an island with a dormant volcano. Suddenly, a monstrous explosion demolished the top of the volcano. Explosions followed day after day as sea water entered the crater containing molten magma. The island was practically destroyed by the last explosion. All that remains of it today is a ring of small islands.

Largest volcanic eruptions

1450 BC e., Santorini, Greece. The largest explosive eruption of ancient times.
79, Vesuvius, Italy. Described by Pliny the Younger. Pliny the Elder died in the eruption.
1815, Tambora, Indonesia. More than 90,000 human casualties.
1883, Krakatoa, Java. The roar could be heard 5000 km away.
1980, St. Helens, USA. The eruption was captured on film.

Volcanoes- These are geological formations on the surface of the Earth's crust or the crust of another planet, where magma comes to the surface, forming lava, volcanic gases, rocks (volcanic bombs) and pyroclastic flows.

The word “volcano” comes from ancient Roman mythology and comes from the name of the ancient Roman god of fire, Vulcan.

The science that studies volcanoes is volcanology and geomorphology.

Volcanoes are classified by shape (shield, stratovolcanoes, cinder cones, domes), activity (active, dormant, extinct), location (terrestrial, underwater, subglacial), etc.

Volcanic activity

Volcanoes are divided depending on the degree of volcanic activity into active, dormant, extinct and dormant. An active volcano is considered to be a volcano that erupted during a historical period of time or in the Holocene. The concept of active is quite inaccurate, since a volcano with active fumaroles is classified by some scientists as active, and by others as extinct. Dormant volcanoes are considered to be inactive volcanoes where eruptions are possible, and extinct volcanoes are considered to be those where they are unlikely.

However, there is no consensus among volcanologists on how to define an active volcano. The period of volcanic activity can last from several months to several million years. Many volcanoes exhibited volcanic activity tens of thousands of years ago, but are not considered active today.

Astrophysicists, from a historical perspective, believe that volcanic activity, caused, in turn, by the tidal influence of other celestial bodies, can contribute to the emergence of life. In particular, it was volcanoes that contributed to the formation of the earth's atmosphere and hydrosphere, releasing significant amounts of carbon dioxide and water vapor. Scientists also note that too active volcanism, such as on Jupiter's moon Io, can make the planet's surface uninhabitable. At the same time, weak tectonic activity leads to the disappearance of carbon dioxide and sterilization of the planet. “These two cases represent potential boundaries for planetary habitability and exist alongside the traditional parameters of habitable zones for systems of low-mass main sequence stars,” the scientists write.

Types of volcanic structures

In general, volcanoes are divided into linear and central, but this division is arbitrary, since most volcanoes are confined to linear tectonic disturbances (faults) in the earth's crust.

Linear volcanoes or fissure-type volcanoes have extensive supply channels associated with a deep split in the crust. As a rule, basaltic liquid magma flows out of such cracks, which, spreading to the sides, forms large lava covers. Along the cracks, gentle spatter shafts, wide flat cones, and lava fields appear. If the magma has a more acidic composition (higher silicon dioxide content in the melt), linear extrusive ridges and massifs are formed. When explosive eruptions occur, explosive ditches can appear tens of kilometers long.

The shapes of central-type volcanoes depend on the composition and viscosity of the magma. Hot and easily mobile basaltic magmas create vast and flat shield volcanoes (Mauna Loa, Hawaiian Islands). If a volcano periodically erupts either lava or pyroclastic material, a cone-shaped layered structure, a stratovolcano, appears. The slopes of such a volcano are usually covered with deep radial ravines - barrancos. Volcanoes of the central type can be purely lava, or formed only by volcanic products - volcanic scoria, tuffs, etc. formations, or be mixed - stratovolcanoes.

There are monogenic and polygenic volcanoes. The former arose as a result of a single eruption, the latter as a result of multiple eruptions. Viscous, acidic in composition, low-temperature magma, squeezed out of the vent, forms extrusive domes (Montagne-Pelé needle, 1902).

In addition to calderas, there are also large negative relief forms associated with subsidence under the influence of the weight of erupted volcanic material and a pressure deficit at depth that arose during the unloading of the magma chamber. Such structures are called volcanotectonic depressions. Volcanotectonic depressions are very widespread and often accompany the formation of thick strata of ignimbrites - volcanic rocks of acidic composition, having different genesis. They are lava or formed by sintered or welded tuffs. They are characterized by lens-shaped segregations of volcanic glass, pumice, lava, called fiamme, and a tuff or tofo-like structure of the main mass. As a rule, large volumes of ignimbrites are associated with shallow magma chambers formed due to the melting and replacement of host rocks. Negative relief forms associated with central-type volcanoes are represented by calderas - large rounded failures several kilometers in diameter.

Classification of volcanoes by shape

The shape of a volcano depends on the composition of the lava it erupts; Five types of volcanoes are usually considered:

Shield volcanoes, or "shield volcanoes". Formed as a result of repeated ejections of liquid lava. This form is characteristic of volcanoes that erupt low-viscosity basaltic lava: it flows for a long time both from the central vent and from the side craters of the volcano. Lava spreads evenly over many kilometers; Gradually, a wide “shield” with gentle edges is formed from these layers. An example is the Mauna Loa volcano in Hawaii, where lava flows directly into the ocean; its height from its base on the ocean floor is approximately ten kilometers (while the underwater base of the volcano is 120 km long and 50 km wide).
Cinder cones. When such volcanoes erupt, large fragments of porous slag are piled up around the crater in layers in the shape of a cone, and small fragments form sloping slopes at the foot; With each eruption the volcano gets higher. This is the most common type of volcano on land. They are no more than a few hundred meters in height. An example is the Plosky Tolbachik volcano in Kamchatka, which exploded in December 2012.
Stratovolcanoes, or "layered volcanoes". Periodically erupt lava (viscous and thick, quickly solidifying) and pyroclastic matter - a mixture of hot gas, ash and hot stones; as a result, deposits on their cone (sharp, with concave slopes) alternate. Lava from such volcanoes also flows out of cracks, solidifying on the slopes in the form of ribbed corridors that serve as the support of the volcano. Examples - Etna, Vesuvius, Fuji.
Dome volcanoes. They are formed when viscous granite magma, rising from the depths of the volcano, cannot flow down the slopes and hardens at the top, forming a dome. It clogs its mouth, like a cork, which over time is expelled by the gases accumulated under the dome. Such a dome is now forming over the crater of Mount St. Helens in the northwestern United States, formed during the 1980 eruption.
Complex (mixed, composite) volcanoes.

Volcanic eruption

Volcanic eruptions are geological emergencies that can lead to natural disasters. The eruption process can last from several hours to many years. Among the various classifications, general types of eruptions are distinguished:

Hawaiian type - emissions of liquid basaltic lava, often forming lava lakes, which should resemble scorching clouds or red-hot avalanches.
Hydroexplosive type - eruptions that occur in shallow conditions of oceans and seas are characterized by the formation of a large amount of steam that occurs when hot magma and sea water come into contact.

Post-volcanic phenomena

After eruptions, when the activity of the volcano either stops forever, or it “dormants” for thousands of years, processes associated with the cooling of the magma chamber and called post-volcanic processes persist on the volcano itself and its surroundings. These include fumaroles, thermal baths, and geysers.

During eruptions, a volcanic structure sometimes collapses with the formation of a caldera - a large depression with a diameter of up to 16 km and a depth of up to 1000 m. As the magma rises, the external pressure weakens, associated gases and liquid products escape to the surface, and a volcanic eruption occurs. If ancient rocks, and not magma, are brought to the surface, and the gases are dominated by water vapor formed when groundwater is heated, then such an eruption is called phreatic.

Lava that rises to the earth's surface does not always reach this surface. It only raises layers of sedimentary rocks and hardens in the form of a compact body (laccolith), forming a unique system of low mountains. In Germany, such systems include the Rhön and Eifel regions. In the latter, another post-volcanic phenomenon is observed in the form of lakes filling the craters of former volcanoes that failed to form a characteristic volcanic cone (the so-called maars).

Heat sources

One of the unresolved problems of volcanic activity is determining the heat source necessary for local melting of the basalt layer or mantle. Such melting must be highly localized, since the passage of seismic waves shows that the crust and upper mantle are usually in a solid state. Moreover, the thermal energy must be sufficient to melt huge volumes of solid material. For example, in the USA in the Columbia River basin (Washington and Oregon states) the volume of basalts is more than 820 thousand km³; the same large strata of basalts are found in Argentina (Patagonia), India (Deccan Plateau) and South Africa (Great Karoo Rise). Currently there are three hypotheses. Some geologists believe that the melting is caused by local high concentrations of radioactive elements, but such concentrations in nature seem unlikely; others suggest that tectonic disturbances in the form of shifts and faults are accompanied by the release of thermal energy. There is another point of view, according to which the upper mantle under conditions of high pressure is in a solid state, and when, due to fracturing, the pressure drops, it melts and liquid lava flows through the cracks.

Areas of volcanic activity

The main areas of volcanic activity are South America, Central America, Java, Melanesia, the Japanese Islands, the Kuril Islands, Kamchatka, the northwestern part of the USA, Alaska, the Hawaiian Islands, the Aleutian Islands, Iceland, and the Atlantic Ocean.

Mud volcanoes

Mud volcanoes are small volcanoes through which it is not magma that comes to the surface, but liquid mud and gases from the earth's crust. Mud volcanoes are much smaller in size than ordinary ones. Mud typically comes to the surface cold, but the gases emitted by mud volcanoes often contain methane and can ignite during the eruption, creating what looks like a miniature eruption of an ordinary volcano.

In our country, mud volcanoes are most common on the Taman Peninsula; they are also found in Siberia, near the Caspian Sea and in Kamchatka. On the territory of other CIS countries, the most mud volcanoes are in Azerbaijan; they are found in Georgia and Crimea.

Volcanoes on other planets

Volcanoes in culture

Painting by Karl Bryullov “The Last Day of Pompeii”;
Movies "Volcano", "Dante's Peak" and a scene from the film "2012".
The volcano near the Eyjafjallajökull glacier in Iceland during its eruption became the subject of a huge number of humorous programs, television news stories, reports and folk art discussing events in the world.

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Volcanic eruption- active volcanic activity, dangerous for any form of life, ejection of hot debris, ash, and outpouring of lava onto the earth's surface. A volcanic eruption can last from several hours to many years. During explosive eruptions, large amounts of debris are released: volcanic bombs (from the size of a pea to 2-3 meters), ash. As a result, the release of ash at high altitudes into the atmosphere affects the Earth's weather over a long period of time. During some eruptions, viscous magma solidifies in the crater of the volcano without erupting.

The volcano emits gases, liquids and solids with high temperatures. This often causes the destruction of buildings and loss of life. Lava and other hot erupted substances flow down the slopes of the mountain and burn out everything they meet on their way, causing innumerable casualties and staggering material losses. The only protection against volcanoes is general evacuation, so the population must be familiar with the evacuation plan and unquestioningly obey the authorities if necessary.

In August 1883, one of the most famous and powerful volcanic eruptions occurred in Indonesia on the island of Krakatau (altitude 800 m), the echoes of this event were heard even 3500 km away. in Australia, and for a whole year after the eruption the sky was decorated with extraordinary, colorful stains. 18 cubic kilometers of lava poured out and a huge wave, 35 meters high, swept away hundreds of coastal villages and cities in Java and Sumatra, killing 36 thousand people.

There are about 600 active volcanoes on Earth. The highest of them are in Ecuador (Cotopaxi - 5896 and Sangay - 5410 meters) and in Mexico (Popocatepetl - 5452 meters). Russia is home to the world's fourth highest volcano - Klyuchevskaya Sopka, 4,750 meters high. One catastrophic eruption occurred on May 8, 1902 on the island of Martinique in the Caribbean Sea. The day before, the Soufriere volcano woke up on a neighboring island, killing 2 thousand people. Residents of the town of Saint-Pierre in Martinique did not perceive this as a threat to themselves - only two thousand people were evacuated. And the next morning, three explosions rained down hot lava and ash on the town. The city burned completely, killing 30 thousand people.

Klyuchevskoy volcano

In the history of disasters, another terrible eruption - Vesuvius - occupies a special place. On August 24, 79, an explosion was heard over the Gulf of Neopolitan, which buried three cities under a layer of ash, lava and boiling mud: Pompeii, Herculaneum and Stabia. 10 thousand people died that day.

Almost all manifestations of volcanic activity are dangerous. The danger of boiling lava or bombs is self-evident. But no less terrible is the ashes that penetrate literally everywhere. Imagine a continuous gray-black snowfall that covers the streets and ponds, the doors of houses. Roofs collapsing under its weight. Pompeii died exactly like this: under a 7-8 meter layer of ash.

The volcano is dangerous not only during an eruption. The crater can hide boiling sulfur under its outwardly strong crust for a long time. Acidic or alkaline gases that resemble fog are also dangerous. However, even ordinary carbon dioxide kills all living things.
The Death Valley in Kamchatka (in the Valley of Geysers) accumulates carbon dioxide, which is heavier than air, and wolves, foxes, hares or birds often die when they find themselves in this lowland. It is interesting that a person can pass through such a trap without even noticing - if he finds himself above a layer of heavy gas.

Eruption of Mount Pinatubo

Modern science predicts volcanic eruptions quite accurately. Almost every active volcano has stations or instruments that allow you to monitor the life of the fiery mountain. The usual solution when there is a threat of disaster is to evacuate neighboring towns and cities. However, sometimes you manage to argue with the elements. For example, in 1983, on the slope of the famous Etna, it was possible to create a directional channel for lava with explosions, which saved nearby villages from the threat.

As a comforting example, we can cite the story of the struggle of the inhabitants of the Icelandic town of Veistmannaeyjar with their volcano, which woke up on January 23, 1973. About two hundred men who remained after the evacuation directed fire jets at the lava creeping towards the port. As the water cooled, the lava turned to stone. Powerful jets of sea water from a dredger that entered the port joined the fight. Then the pipelines were installed, most of the city and the port were saved, and no one was hurt. True, the fight against the volcano dragged on for almost six months.

Here are the measures to take when evacuation is not necessary:

do not panic, stay at home, closing doors and windows;
if anyone needs help, then leave the house wearing warm clothes, preferably non-flammable, protecting your nose and mouth with a dampened rag;
do not take refuge in basements, so as not to be buried under a layer of dirt;
do not use a car;
do not call, but receive information via radio;
stock up on water;
ensure that the fall of hot stones does not cause fires, which should be extinguished immediately; at the first opportunity, clear the roofs of ash;
invite specialists to check the stability of the building.

British scientists believe that humanity could die as a result of a gigantic volcanic eruption. As Stephen Self of the UK Open University said in an interview with LiveScience, there is no way to prevent a disaster. Geophysicists claim that some volcanoes are capable of eruptions hundreds of times more powerful than those ever observed. Cataclysms of this magnitude, however, have already occurred on Earth - long before the advent of civilization.

Yellowstone National Park

Earlier, American geologists discovered a relatively shallow meter-thick layer of volcanic ash in Yellowstone National Park. The culprit of its occurrence is considered to be an eruption of exceptional force that occurred approximately 620 thousand years ago. A monument to this event are giant craters - calderas, which were formed after the destruction of “devastated” volcanoes. The consequences of the giant eruption are detailed in a report presented to the UK government's natural disasters working group. Quite large areas are buried under a layer of lava, and dust and ash released into the atmosphere impede the access of sunlight to the earth's surface, which affects the global climate. As Michael Rampino from New York University showed in his study, the “super-eruption” of the Toba volcano on the island of Sumatra, which occurred 74 thousand years ago, led to a noticeable cooling and the death of three-quarters of the flora of the Northern Hemisphere.

A truly amazing sight is a volcanic eruption. But what is a volcano? How does a volcano erupt? Why do some of them spew out huge streams of lava at different intervals, while others sleep peacefully for centuries?

Externally, the volcano resembles a mountain. There is a geological fault inside it. In science, a volcano is a formation of geological rock located on the surface of the earth. Magma, which is very hot, erupts through it. It is magma that subsequently forms volcanic gases and rocks, as well as lava. Most of the volcanoes on earth were formed several centuries ago. Today, new volcanoes rarely appear on the planet. But this happens much less frequently than before.

How are volcanoes formed?

If we briefly explain the essence of the formation of a volcano, it will look like this. Under the earth's crust there is a special layer under strong pressure, consisting of molten rocks, it is called magma. If cracks suddenly begin to appear in the earth’s crust, then hills form on the surface of the earth. Through them, magma comes out under strong pressure. At the surface of the earth, it begins to break down into hot lava, which then solidifies, causing the volcanic mountain to become larger and larger. The emerging volcano becomes such a vulnerable spot on the surface that it spews volcanic gases onto the surface with great frequency.

What is a volcano made of?

In order to understand how magma erupts, you need to know what a volcano is made of. Its main components are: a volcanic chamber, a vent and craters. What is a volcanic source? This is the place where magma is formed. But not everyone knows what a volcano’s crater and crater are? A vent is a special channel that connects the hearth with the surface of the earth. A crater is a small bowl-shaped depression on the surface of a volcano. Its size can reach several kilometers.

What is a volcanic eruption?

Magma is constantly under intense pressure. Therefore, there is a cloud of gases above it at any time. Gradually they push hot magma to the surface of the earth through the crater of the volcano. This is what causes an eruption. However, just a short description of the eruption process is not enough. To see this spectacle, you can use the video, which you need to watch after you have learned what the volcano is made of. In the same way, in the video you can find out which volcanoes do not exist nowadays and what the volcanoes that are active today look like.

Why are volcanoes dangerous?

Active volcanoes pose a danger for a number of reasons. The dormant volcano itself is very dangerous. It can “wake up” at any time and begin to erupt streams of lava, spreading over many kilometers. Therefore, you should not settle near such volcanoes. If an erupting volcano is located on an island, a dangerous phenomenon such as a tsunami may occur.

Despite their danger, volcanoes can serve humanity well.

How are volcanoes useful?

During the eruption, a large amount of metals appears that can be used in industry.
The volcano produces the strongest rocks that can be used for construction.
Pumice, which appears as a result of the eruption, is used for industrial purposes, as well as in the production of stationery erasers and toothpaste.

Volcanic eruption diagram

The magma that flows out is called lava. Lava cools, hardens, and forms volcanic, or igneous, rock. Sometimes lava is liquid and flowing. It oozes from the volcano like boiling syrup and spreads over a large area. When such lava cools, it forms a hard cover of rock called basalt. With the next eruption, the thickness of the cover increases, and each new layer of lava can reach 10 m. Such volcanoes are called linear or fissure, and their eruptions are calm.

During explosive eruptions, the lava is thick and viscous.

It pours out slowly and hardens near the crater of the volcano. With periodic eruptions of this type of volcano, a high conical mountain with steep slopes appears, the so-called stratovolcano.

The lava temperature can exceed 1000 °C. Some volcanoes emit clouds of ash that rise high into the air.

Ash can settle near the volcano's mouth, and then an ash cone appears. The explosive force of some volcanoes is so great that huge blocks of lava the size of a house are thrown out.

These "volcano bombs" fall near a volcano.

Along the entire mid-ocean ridge, lava seeps up from the mantle from many active volcanoes onto the ocean floor.

From deep-sea hydrothermal vents located near volcanoes, gas bubbles and hot water with minerals dissolved in them erupt

An active volcano regularly spews lava, ash, smoke and other products.

If there is no eruption for many years or even centuries, but in principle it can happen, such a volcano is called dormant.

Volcanoes - how are they formed, why do they erupt and why are they dangerous and useful?

If a volcano has not erupted for tens of thousands of years, it is considered extinct. Some volcanoes emit gases and streams of lava. Other eruptions are more violent and produce huge clouds of ash.

More often than not, lava oozes slowly onto the Earth's surface over a long period of time without any explosions occurring. It pours out from long cracks in the earth's crust and spreads, forming lava fields.

Where do volcanic eruptions occur?

Cone-shaped volcanoes, typical of land, look huge and powerful.

However, they account for less than one hundredth of all volcanic activity on Earth. Most of the magma flows to the surface deep underwater through cracks in the mid-ocean ridges. If underwater volcanoes erupt large enough amounts of lava, their peaks reach the surface of the water and become islands.

Examples are the Hawaiian Islands in the Pacific Ocean or the Canary Islands in the Atlantic.

Santorini was an island with a dormant volcano. Suddenly, a monstrous explosion demolished the top of the volcano.

Explosions followed day after day as sea water entered the crater containing molten magma. The island was practically destroyed by the last explosion. All that remains of it today is a ring of small islands.

Largest volcanic eruptions

1450 BC e., Santorini, Greece. The largest explosive eruption of ancient times.
79, Vesuvius, Italy. Described by Pliny the Younger. Pliny the Elder died in the eruption.
1815, Tambora, Indonesia.
More than 90,000 human casualties.
1883, Krakatoa, Java. The roar could be heard 5000 km away.
1980, St. Helens, USA. The eruption was captured on film.

Introduction

1. Volcanoes of the Russian Federation

Volcanic eruptions

4. Signs of an upcoming eruption

6. Other threats associated with volcanic fallout

Conclusion

Sources of information

Introduction

Outwardly, every volcano is an elevation, not necessarily high.

The elevation is connected by a channel to a magma chamber at depth. Magma is a flattened mass consisting mainly of silicates. Magma, obeying certain physical laws, can rise together with water vapor and gases from the depths to the top. Overcoming obstacles on its way, magma pours out to the surface. Magma that flows to the surface is called lava. The release of vapors, gases, magma, and rocks from the crater of a volcano is a volcanic eruption.

Main parts of the volcanic apparatus:

— magma chamber (in the earth’s crust or upper mantle);

- vent - an outlet channel through which magma rises to the surface;

- cone - a hill on the Earth’s surface made of volcanic ejection products;

- crater - a depression on the surface of a volcano cone.

More than 200 million

earthlings live dangerously close to active volcanoes. Of course, they are exposed to a certain danger, but the degree of risk does not exceed the possibility of getting hit by a city resident’s car. It is estimated that over the past 500 years, about 200 thousand people have died as a result of volcanic eruptions in the world.

There are about 600 active volcanoes on earth.

The highest of them are in Ecuador (Cotopaxi - 5896 m and Sangay - 5410 m) and in Mexico (Popocatepetl - 5452 m). Russia is home to the world's fourth highest volcano, Klyuchevskaya Sopka, 4,750 m high.

The most catastrophic can be considered the generally low – 800 m – Indonesian volcano Krakatoa. On the night of August 26-27, 1883, after three terrible explosions on a small deserted island, the sky was covered with ash and 18 cubic meters of water poured out. kilometers of lava.

A huge wave (about 35 m) literally washed away hundreds of coastal villages and cities in Java and Sumatra. 36 thousand people died in this tragedy. volcano eruption ashfall

Volcanoes of the Russian Federation

Modern volcanic activity on the territory of the Russian Federation is almost entirely concentrated in the Kuril-Kamchatka island arc, where there are at least 69 active volcanoes. At the same time, potentially active or “dormant” volcanoes were discovered in a number of other areas of the country. First of all, this is the Greater Caucasus with the Elbrus and Kazbek volcanoes (last eruptions within 3-7 thousand years ago), the south of Eastern Siberia (Kropotkin volcano, active 500-1000 years ago), Chukotka (Anyuysky volcano, active in within the last millennium) and, possibly, the Baikal region.

Kamchatka and the Kuril Islands are a seismically unstable area that is part of the “ring of fire” of the Pacific Ocean.

Of the 120 volcanoes located here, about 39 are active - strong eruptions and earthquakes can be expected from the subsoil here.

In 1955, the Bezymyannaya hill erupted. In November, the volcano awakened and began to emit steam and ash. On November 17, in the village of Klyuchi (24 km from the hill) it was so dark that the electricity was not turned off all day.

On March 30, 1956, the Bezymianny volcano exploded. A cloud of ash rose from the crater to a height of 24 km. In the next 15 minutes, an even larger cloud was erupted to a height of 43 km.

Trees were torn out of the ground 24 km from the crater, fires broke out 30 km away, and mud flows extended over 90 km. The resulting wave was felt at a distance of up to 20 km from the crater.

After the eruption, the shape of the volcano completely changed, and its peak became 500 m lower. In place of its peak, a funnel was formed up to 2 km wide and up to 1 km deep.

In 1994, during the eruption of the Klyuchevskaya Sopka volcano, an ash cloud made it difficult for aircraft to fly at an altitude of 20,000 meters.

Almost all manifestations of volcanic activity are dangerous.

Lava and mud flows (lahars) can completely destroy settlements lying in their path.

Danger threatens people who find themselves near or between tongues of magma. No less terrible is the ashes that penetrate literally everywhere.

PHASES OF A VOLCANO ERUPTION

Water sources are filled with lava and ash, and roofs of houses collapse.

The volcano is dangerous not only during an eruption. The crater may conceal boiling sulfur under its apparently strong crust for a long time. Acidic or alkaline gases that resemble fog are also dangerous.

The Death Valley in Kamchatka (in the Valley of Geysers) accumulates carbon dioxide, which is heavier than air, and animals often die when they find themselves in this lowland.

Classification of volcanoes by shape

—Shield volcanoes are formed as a result of repeated ejections of liquid lava. This shape is characteristic of volcanoes that erupt low-viscosity basaltic lava: it flows from both the central crater and the slopes of the volcano.

Lava spreads evenly over many kilometers. Like, for example, on the Mauna Loa volcano in the Hawaiian Islands where it flows directly into the ocean.

—Slag cones eject from their vent only such loose substances as stones and ash: the largest fragments accumulate in layers around the crater.

Because of this, the volcano becomes higher with each eruption. Light particles fly away over a longer distance, which makes the slopes gentle.

—Stratovolcanoes, or “layered volcanoes,” periodically erupt lava and pyroclastic matter - a mixture of hot gas, ash and hot rocks. Therefore, deposits on their cone alternate. On the slopes of stratovolcanoes, ribbed corridors of solidified lava are formed, which serve as support for the volcano.

—Dome volcanoes are formed when granitic, viscous magma rises above the rim of a volcano's crater and only a small amount seeps out, flowing down the slopes.

Magma clogs the volcano's crater, like a cork, which the gases accumulated under the dome literally knock out of the crater.

3. Volcanic eruptions

Volcanic eruptions are geological emergencies that can lead to natural disasters.

The eruption process can last from several hours to many years. Among the various classifications, general types stand out:

Hawaiian type- emissions of liquid basaltic lava, often forming lava lakes. should resemble scorching clouds or red-hot avalanches.

Hydroexplosive type- eruptions that occur in shallow water conditions of oceans and seas are characterized by the formation of a large amount of steam that occurs when hot magma and sea water come into contact.

Signs of an upcoming eruption

– Increased seismic activity (from barely noticeable vibrations of lava to a real earthquake).

– “Grumbling” coming from the crater of the volcano and from underground.

– The smell of sulfur coming from rivers and streams flowing near the volcano.

– Acid rain.

– Pumice dust in the air.

– Gases and ash escaping from the crater from time to time.

Actions of people during a volcanic eruption

Knowing about the eruption, you can change the path of lava flows using special gutters and trays. They allow the flow to bypass dwellings and keep it in the right direction. In 1983, on the slope of the famous Etna, explosions succeeded in creating a directional channel for lava, which saved nearby villages from the threat.

Sometimes cooling the lava flow with water helps - this method was used by the inhabitants of Iceland when fighting the volcano that “awakened” on January 23, 1973.

About 200 men who remained after the evacuation directed fire jets at the lava creeping toward the port. As the water cooled, the lava turned to stone. It was possible to save most of the city of Veistmannaeyjar, the port, and no one was hurt.

True, the fight against the volcano dragged on for almost six months. But this is the exception rather than the rule: a huge amount of water was required, and the island was small.

How to prepare for a volcanic eruption

Watch for warnings about a possible volcanic eruption. You will save your life if you leave the dangerous territory in a timely manner. If you receive an ash warning, close all windows, doors and smoke dampers.

Place cars in garages. Keep animals indoors.

Stock up on self-powered sources of lighting and heat, water, and food for 3 to 5 days.

What to do during a volcanic eruption

At the first “symptoms” of a beginning eruption, you need to carefully listen to the messages of the Ministry of Emergency Situations and follow all their instructions.

It is advisable to urgently leave the disaster area.

What to do if an eruption catches you on the street?

1. Run towards the road, try to protect your head.

2. If you are driving a car, be prepared for the wheels to get stuck in a layer of ash. Don't try to save the car, leave it and get out on foot.

If a ball of hot dust and gases appears in the distance, save yourself by taking refuge in an underground shelter that is built in seismic zones, or dive into the water until the hot ball rushes on.

What measures should be taken if evacuation is not necessary?

Do not panic, stay at home, closing doors and windows.

2. When going outside, remember that you cannot wear synthetic clothes, as they can catch fire, and your clothes should be as comfortable as possible. The mouth and nose should be protected with a damp cloth.

3. Don't take refuge in the basement to avoid being buried under a layer of dirt.

Stock up on water.

5. Make sure that falling stones do not cause a fire. As soon as possible, clear the roofs of ash and extinguish any fire that occurs.

Follow the messages of the Ministry of Emergency Situations on the radio.

What to do after a volcanic eruption

Cover your mouth and nose with gauze to prevent inhalation of ash. Wear safety glasses and clothing to prevent burns. Do not try to drive a car after ash has fallen out - this will lead to its failure. Clear the roof of your house from ash to prevent it from being overloaded and destroyed.

Before it begins to erupt, a volcano trembles, swells, heats up and releases gas. Warned by these signs, volcanologists are trying to prevent a disaster and evacuate the population in advance. Volcanologists, armed with modern equipment, monitor the harbingers of an eruption.

Map of danger zones. To predict the future, you need to know the past well. Geologists and volcanologists reconstruct the history of a volcano.

They study previous eruptions, the damage they caused, and the direction of lava flows. This helps them create a map of danger zones: it indicates possible eruption products (blocks, ash), paths for ash and gas clouds, and residential areas that are at risk.

Harbingers of an eruption.

Most often, an eruption makes you aware of its approach. Thus, when magma rises to the surface, underground tremors (seismic vibrations) appear, which are not felt on the surface. The closer the eruption is, the more frequent the rhythm of these tremors becomes, sometimes reaching up to 100 tremors per hour. Then scientists install seismographs on the volcano to take measurements.

Sometimes this is a false alarm: seismic activity may not be accompanied by an eruption, and vice versa. Before an eruption, the volcano swells like a pie in the oven: it grows several centimeters, and sometimes several meters.

Thus, Mount St. Helens grew 200 meters before its eruption on May 18, 1980! In this case, volcanologists constantly measure the height of the peak, the deviation of the slopes, the size of cracks in the faults... They also measure the increase in the mountain using satellites. Finally, before the eruption, the gases appearing in the fumaroles located in the wells of the volcano heat up and their chemical composition changes. The temperature of underground water is also rising. Volcanologists are constantly taking samples and analyzing them.

Many volcanoes are monitored only when they threaten danger. But some, especially dangerous ones, are constantly monitored. Special observatories are located near them.

Due to a lack of funds, only thirty of the dangerous volcanoes are constantly under the control of scientists, while some volcanoes that have not erupted for a long time could wake up at any moment.

Naples, at the foot of Mount Vesuvius. For several decades now, Vesuvius has been under the close attention of scientists. In their opinion, this is the most dangerous volcano. Its last, rather weak, eruption occurred in 1944, but the subsequent one promises to be much more dangerous.

About 800,000 people live in the immediate vicinity of this sleeping monster and 3 million within a 30 km radius of it. Thanks to research into the 1663 eruption, which killed 4,000 people, experts have developed an evacuation plan. It will be put into action as soon as the first signs of an impending disaster appear.

Whenever volcanologists notice unusual signs that are harbingers of an eruption, they immediately alert the authorities.

They take samples of lava and slag and study them. Determine the possible type of eruption and its danger zones. If activity intensifies, authorities, following the advice of volcanologists, may begin evacuating the population.

Battle against the volcano. In their relationships with volcanoes, people very often lose. In 1992, the Italians tried to build a barrier 224 meters long and 21 meters high to block Etna's lava flows. However, the lava quickly broke through these barriers.

But another attempt was successful. Streams of lava flowed through a natural tunnel. After a directed explosion, its flow went underground, then a plug formed and the lava came to the surface. Another victory was won in Iceland, on the island of Eimey.

In 1973, the Eldfell volcano began to erupt.

Volcanic eruption

The residential area was evacuated, but lava flows threatened the port. This was a direct threat to fishing, the main local industry. Then rescuers, together with local residents, using powerful pumps, began to pour 12 million cubic meters of water per hour onto the lava flows. After three weeks of battle, the people were victorious: the lava flows were turned into the sea.

Natural disasters can be different, but one of the most dangerous is rightfully recognized. Every day, up to ten such emissions occur on the planet, many of which people do not even notice.

What is a volcano?

A volcano is a geological formation located on the crust. Where craters are located, magma comes out and forms lava, followed by gases and rock fragments.

The stone giant received its name from the ancient Roman god of fire, who bore the majestic name Vulcan.

Classification

Such mountains can be classified according to several criteria. So, for example, according to their form, these formations are divided into the following types:

Shield ones.
Stratovolcanoes.
Slag.
Cone-shaped.
Dome.

In addition, volcanoes can be identified depending on their location:

Ground.
Underwater.
Subglacial.

In addition, among ordinary people there is another, simple classification, which depends on the degree of volcanic activity:

Active. This formation is characterized by the fact that it erupted relatively recently.
This definition refers to a mountain that is currently inactive but may erupt in the future.
An extinct volcano is a tectonic formation that no longer has the ability to gush.

Why do volcanoes erupt?

Before you understand the products that come out of a volcano during an eruption, you need to know what this terrible phenomenon is and what its causes are.

An eruption means the release of lava flows to the surface, which is accompanied by the release of gases and ash. Volcanoes erupt due to a large amount of substances accumulated in the magma.

What comes out of a volcano during an eruption?

Magma is constantly under very high pressure, so gases always remain dissolved in it as a liquid. The molten rock, which is gradually pushed towards the surface by the onslaught of volatile substances, passes through cracks and enters the hard layers of the mantle. Here the magma quickly comes out.

It would seem that there should be no more questions about what appears during a volcanic eruption, because magma turns into lava and spills onto the surface. However, in fact, during an eruption, in addition to the indicated components, many different substances can reveal themselves to the world.

Lava

Lava is the most famous product released during active volcanic activity. This is what people most often point to when answering the question: “What comes out of a volcano during an eruption?” A photo of this hot substance can be seen in the article.

Lava masses are compounds of silicon, aluminum and other metals. There is also an interesting fact associated with it: it is known that it is the only earthly product in which all the elements found in the periodic table can be found.

Lava is hot magma that flows from the crater of a volcano and flows down its slopes. During the ascent, the composition of the underground guest constantly undergoes changes due to atmospheric factors. In addition, a large amount of gases that rise to the surface along with the magma make it bubbly.

The average is 1000 degrees, so it easily destroys all obstacles that come in its way.

Wreckage

It is no less interesting to consider what comes out during a volcanic eruption, other than lava. At the height of the process, huge fragments, which scientists call “tephra,” are thrown onto the surface of the earth.

Of the total mass, the largest fragments are distinguished, nicknamed “volcanic bombs”. These fragments are liquid products that freeze in the air during release. The size of such stones can vary: the smallest of them are similar to peas, and the largest exceed the size of a walnut.

Ash

Also, when answering the question “What comes out of a volcano?”, we must not forget about ash. It is this that often leads to catastrophic consequences, since it is released even during a minor eruption that cannot harm people.

Small ash particles spread through the air at enormous speeds - up to 100 kilometers per hour. Naturally, a significant amount of this substance can enter a person’s throat during breathing, so during an eruption you should cover your face with a scarf or a special respirator. The peculiarity of ash is that it is able to cross vast distances, even bypassing water and hills. These small particles are so hot that they constantly glow in the dark.

Gases

We should not forget that, among other things, a large amount of gases comes out of a volcano during an eruption. This volatile mixture consists of hydrogen, sulfur and carbon. Contains boron, bromic acid, mercury, and metals in small quantities.

All gases that are released during an eruption are white. And if tephra is mixed with the gases, the clouds take on a black tint. Often, it is by the black smoke coming from a volcanic crater that people determine that an eruption will occur soon and they need to evacuate.

In addition, you need to know what comes out of a volcano during an eruption, in addition to the substances listed above. This is a strong smell of hydrogen sulfide. So, for example, on some islands the volcanic spirit spreads over hundreds of kilometers.

A remarkable fact: a small amount of gas continues to be released from the volcano for several years after the eruption. Moreover, such emissions are very toxic, and when they get into the water with rain, they poison it and make it unfit for drinking.