Naturally occurring, such as volcanoes. ...How and why volcanoes erupt

Volcanoes are geological formations on the surface of the earth's crust where magma comes to the surface, forming lava, volcanic gases, "volcanic bombs" and pyroclastic flows. The name “volcano” for this type of geological formation comes from the name ancient roman god fire "Vulcan".

Deep below the surface of our planet Earth, the temperature is so high that rocks begin to melt, turning into a thick, viscous substance - magma. The molten substance is much lighter than the solid rock around it, so the magma, as it rises, accumulates in so-called magma chambers. Eventually, some of the magma escapes to the Earth's surface through fissures in earth's crust- this is how a volcano is born - a beautiful, but extremely dangerous natural phenomenon, often bringing with it destruction and casualties.

The magma that escapes to the surface is called lava; it has a temperature of about 1000 ° C and flows rather slowly down the slopes of the volcano. Thanks not high speed, lava rarely causes human casualties, but lava flows cause significant destruction of any structures, buildings, and structures encountered along the path of these “rivers of fire.” Lava has very poor thermal conductivity, so it cools very slowly.

The greatest danger comes from stones and ash erupting from the crater of the volcano during an eruption. Hot stones, thrown into the air at great speed, fall to the ground, causing numerous casualties. Ashes fall to the ground like “loose snow”, and if people, animals, plants - everything dies from lack of oxygen.

This happened with the notorious city of Pompeii, developing and prospering, and destroyed by the eruption of Mount Vesuvius in a matter of hours. However, pyroclastic flows are rightfully considered the deadliest of all volcanic phenomena. Pyroclastic flows are a boiling mixture of solid and semi-solid rocks and hot gas flowing down the slopes of a volcano. The composition of the streams is much heavier than air, they rush down like snow avalanche, only hot, filled with toxic gases and moving at phenomenal, hurricane speed.

Classification of volcanoes

There are several classifications of volcanoes based on certain characteristics. For example According to the degree of activity, scientists divide volcanoes into three types: extinct, dormant and active..

Volcanoes that have erupted during a historical period of time and are likely to erupt again are considered active. Dormant volcanoes are those that have not erupted for a long time, but still have the potential to erupt. Extinct volcanoes are volcanoes that have ever erupted, but the likelihood of them erupting again is zero.

Classification According to the shape of the volcano, it includes four types: cinder cones, dome, shield volcanoes and stratovolcanoes.

The most common type of volcano on land, a cinder cone is made up of small fragments of solidified lava that escaped into the air, cooled, and fell near the vent. With each eruption, such volcanoes become higher.
Dome volcanoes form when viscous magma is too heavy to flow down the sides of a volcano. It accumulates at the vent, clogging it and forming a dome. Over time, gases knock out such a dome like a cork.
Shield volcanoes have the shape of a bowl or shield with gentle slopes formed by basaltic lava flows - traps.
Stratovolcanoes emit a mixture of hot gas, ash and rocks, as well as lava, which are alternately deposited on the volcano's cone.

Classification of volcanic eruptions

Volcanic eruptions are an emergency situation that is carefully studied by volcanologists to be able to predict the possibility and nature of eruptions in order to minimize the scale of the disaster.

There are several types of eruptions:

Hawaiian,
strombolian,
Peleian,
Plinian,
hydroexplosive.

Hawaiian is the calmest type of eruption, characterized by the release of lava with a small amount of gas, which forms a shield-shaped volcano. The Strombolian type of eruption, named after the Stromboli volcano, which has been continuously erupting for several centuries, is characterized by the accumulation of gas in the magma and the formation of so-called gas plugs in it. Moving upward along with the lava, reaching the surface, giant gas bubbles burst with a loud bang due to the difference in pressure. During an eruption, such explosions occur every few minutes.

The Peleian type of eruption is named after the most massive and destructive eruption of the 20th century. – Montagne Pelee volcano. The erupting pyroclastic flows killed 30,000 people in a matter of seconds. The Pelian type is characteristic of an eruption similar to the eruption of Mount Vesuvius. This type received its name from the chronicler who described the eruption of Vesuvius that destroyed several cities. This type is characterized by the ejection of a mixture of stones, gas and ash to a very high altitude - often the column of the mixture reaches the stratosphere. Volcanoes located in shallow waters in the seas and oceans erupt using the hydroexplosive type. In such cases, a large amount of steam is generated when the magma comes into contact with seawater.

Volcanic eruptions can create many dangers not only in the immediate vicinity of the volcano. Volcanic ash can pose a threat to aviation, posing a risk of failure of aircraft turbojet engines.

Large eruptions can also affect the temperature of entire regions: ash and sulfuric acid particles create areas of smog in the atmosphere and, in part, reflect sunlight, lead to cooling of the lower layers of the Earth’s atmosphere over a particular region, depending on the power of the volcano, the strength of the wind and the direction of movement of air masses.

Volcanic eruption diagram

When a volcano awakens and begins spewing streams of red-hot lava, one of the most amazing things happens. natural phenomena. This happens when there is a hole, crack or weakness. Molten rock, called magma, rises from the depths of the Earth, where incredible high temperatures and pressure on 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 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 ocean floor Many active volcanoes ooze lava as they rise from the mantle. From deep-sea hydrothermal vents located near volcanoes, gas bubbles and hot waters with minerals dissolved in them emerge.

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. Eruptions of others have more stormy character 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 the subduction zone, 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 enough large quantities lava, their peaks reach the surface of the water and become islands. Examples include the Hawaiian Islands in Pacific Ocean or 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 fell into a crater with 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 are geological formations that arise above cracks in the earth's crust. This is due to the fact that lava, gases and rock fragments can escape to the surface through them. This process is called “volcanic eruption”.

Why does this process occur?

Volcanic eruptions are caused by the layers of magma that lie underneath them. Under normal conditions, it is under great pressure, and comes out through cracks in the bark. For comparison, we can give the following example: if you shake a bottle of any carbonated drink and then open it, the contents will flow out very violently.

How do volcanoes erupt?

Warning signs of activity include volcanic earthquakes and loud noises. An eruption usually begins with the release of gases with cold lava particles, which are gradually replaced by hot debris. Sometimes this stage may be accompanied by an outpouring of lava. The height of the emission ranges from one to five kilometers (the highest column of matter occurred during the eruption of the Bezymyanny volcano in Kamchatka - forty-five kilometers). After this, the emissions are transported over distances of up to several tens of thousands of kilometers, and then settle on the Earth’s surface. Sometimes the concentration of ash can be so high that even sunlight cannot penetrate through it. During an eruption, there is an alternation of strong and weak lava emissions. After some time, a culminating paroxysm occurs - an explosion of maximum force, after which activity begins to decline. The consequences of a volcanic eruption are tens of cubic kilometers of spilled lava, as well as tons of ash that falls both onto the surface and into the atmosphere.

What groups are volcanoes divided into?

According to activity - extinct, asleep, active.
The shape of the cracks in the bark is central and fissure.
By appearance volcanoes - cone-shaped, dome-shaped, flat shield-shaped.

What are volcanic eruptions like?

This process can also be characterized from several sides. For example, in terms of time, eruptions can be long-lasting (up to several centuries!) and short-term (several hours). Eruption products can be solid (rocks), liquid (lava) and gaseous.

Types of eruptions

August 24‑25, 79 AD an eruption occurred that was considered extinct Vesuvius volcano, located on the shores of the Gulf of Naples, 16 kilometers east of Naples (Italy). The eruption led to the destruction of four Roman cities - Pompeii, Herculaneum, Oplontium, Stabia - and several small villages and villas. Pompeii, located 9.5 kilometers from the crater of Vesuvius and 4.5 kilometers from the base of the volcano, was covered with a layer of very small pieces of pumice about 5-7 meters thick and covered with a layer of volcanic ash. With the onset of night, lava flowed from the side of Vesuvius, everywhere fires started, and the ashes made it difficult to breathe. On August 25, along with an earthquake, a tsunami began, the sea retreated from the shores, and a black thundercloud hung over Pompeii and surrounding cities, hiding the Misensky cape and the island of Capri. Most of the population of Pompeii was able to escape, but about two thousand people died on the streets and in the houses of the city from poisonous sulfur dioxide gases. Among the victims was the Roman writer and scientist Pliny the Elder. Herculaneum, located seven kilometers from the crater of the volcano and about two kilometers from its base, was covered with a layer of volcanic ash, the temperature of which was so high that all wooden objects were completely charred. The ruins of Pompeii were accidentally discovered at the end of the 16th century, but systematic Excavations began only in 1748 and are still ongoing, along with reconstruction and restoration.

March 11, 1669 an eruption occurred Mount Etna in Sicily, which lasted until July of the same year (according to other sources, until November 1669). The eruption was accompanied by numerous earthquakes. Lava fountains along this fissure gradually moved downwards, and the largest cone formed near the city of Nikolosi. This cone is known as Monti Rossi (Red Mountain) and is still clearly visible on the slope of the volcano. Nikolosi and two nearby villages were destroyed on the first day of the eruption. In another three days, lava flowing south down the slope destroyed four more villages. At the end of March, two more major cities, and in early April lava flows reached the outskirts of Catania. Lava began to accumulate under the fortress walls. Some of it flowed into the harbor and filled it. On April 30, 1669, lava flowed through top part fortress walls. The townspeople built additional walls across the main roads. This made it possible to stop the advance of lava, but West Side the city was destroyed. The total volume of this eruption is estimated at 830 million cubic meters. Lava flows burned 15 villages and part of the city of Catania, completely changing the configuration of the coast. According to some sources, 20 thousand people, according to others - from 60 to 100 thousand.

October 23, 1766 on the island of Luzon (Philippines) began to erupt Mayon volcano. Dozens of villages were swept away and incinerated by a huge lava flow (30 meters wide), which flowed down the eastern slopes for two days. Following the initial explosion and flow of lava, Mayon Volcano continued to erupt for four more days, releasing large amounts of steam and watery mud. Grayish-brown rivers ranging from 25 to 60 meters wide fell down the slopes of the mountain within a radius of up to 30 kilometers. They completely swept away roads, animals, villages with people on their way (Daraga, Kamalig, Tobaco). More than 2,000 residents died during the eruption. Basically, they were swallowed up by the first lava flow or secondary mud avalanches. For two months, the mountain spewed ash and poured lava onto the surrounding area.

April 5-7, 1815 an eruption occurred Tambora volcano on the Indonesian island of Sumbawa. Ash, sand and volcanic dust were thrown into the air to a height of 43 kilometers. Stones weighing up to five kilograms were scattered over a distance of up to 40 kilometers. The Tambora eruption affected the islands of Sumbawa, Lombok, Bali, Madura and Java. Subsequently, under a three-meter layer of ash, scientists found traces of the dead kingdoms of Pecat, Sangar and Tambora. Simultaneously with the volcanic eruption, huge tsunamis 3.5-9 meters high were formed. Having flown away from the island, the water fell on neighboring islands and drowned hundreds of people. About 10 thousand people died directly during the eruption. At least 82 thousand more people died from the consequences of the disaster - hunger or disease. The ash that shrouded Sumbawa destroyed crops and buried the irrigation system; acid rain poisoned the water. For three years after the Tambora eruption, the entire Earth enveloped in a veil of particles of dust and ash, reflecting some sun rays and cooling the planet. The next year, 1816, Europeans felt the consequences of a volcanic eruption. It entered the annals of history as “the year without summer.” average temperature in the Northern Hemisphere fell by about one degree, and in some areas even by 3-5 degrees. The soil suffered from spring and summer frosts large areas crops, and famine began in many areas.

August 26-27, 1883 an eruption occurred Krakatoa volcano, located in the Sunda Strait between Java and Sumatra. Houses on nearby islands collapsed due to tremors. On August 27, at about 10 o'clock in the morning, a gigantic explosion occurred, an hour later - a second explosion of the same force. More than 18 cubic kilometers of rock debris and ash shot up into the atmosphere. The waves of the tsunami caused by the explosions instantly swallowed up cities, villages, and forests on the coasts of Java and Sumatra. Many islands disappeared under water along with the population. The tsunami was so powerful that it went around almost the entire planet. In total, 295 cities and villages were wiped off the face of the earth on the coasts of Java and Sumatra, over 36 thousand people died, and hundreds of thousands were left homeless. The coasts of Sumatra and Java have changed beyond recognition. On the coast of the Sunda Strait, fertile soil was washed away down to the rocky base. Only a third of the island of Krakatoa survived. In terms of the amount of water and rock moved, the energy of the Krakatoa eruption is equivalent to the explosion of several hydrogen bombs. Strange glow and optical phenomena persisted for several months after the eruption. In some places above the Earth, the sun appeared blue and the moon appeared bright green. And the movement of dust particles ejected by the eruption in the atmosphere allowed scientists to establish the presence of a “jet” stream.

May 8, 1902 Mont Pele volcano, located on Martinique, one of the islands Caribbean Sea, literally exploded into pieces - four strong explosions sounded, similar to cannon shots. They threw out a black cloud from the main crater, which was pierced by flashes of lightning. Since the emissions did not come through the top of the volcano, but through side craters, all volcanic eruptions of this type have since been called “Peleian”. Superheated volcanic gas, due to its high density and high speed of movement, spread above the ground itself, penetrated into all the cracks. A huge cloud covered the area of complete destruction. The second zone of destruction stretches another 60 square kilometers. This cloud, formed from super-hot steam and gases, weighed down by billions of particles of hot ash, moved at a speed sufficient to carry debris rocks and volcanic emissions, had a temperature of 700-980°C and was able to melt glass. Mont Pele erupted again on May 20, 1902, with almost the same force as on May 8. The Mont Pelee volcano, breaking into pieces, destroyed one of the main ports of Martinique, Saint-Pierre, along with its population. 36 thousand people died instantly, hundreds of people died from side effects. The two survivors became celebrities. Shoemaker Leon Comper Leander managed to escape within the walls of his own house. He miraculously survived, although he received severe burns to his legs. Louis Auguste Cypress, nicknamed Samson, was in a prison cell during the eruption and remained there for four days, despite serious burns. After being rescued, he was pardoned, soon he was hired by the circus and during performances he was shown as the only surviving resident of Saint-Pierre.

June 1, 1912 eruption began Katmai volcano in Alaska, for a long time was at rest. On June 4, ash material was released, which, when mixed with water, formed mud flows, on June 6, an explosion of colossal force occurred, the sound of which was heard in Juneau 1,200 kilometers away and in Dawson 1,040 kilometers from the volcano. Two hours later there was a second explosion of enormous force, and in the evening a third. Then, for several days, there was an almost continuous eruption of colossal amounts of gases and solid products. During the eruption, about 20 cubic kilometers of ash and debris escaped from the crater of the volcano. The deposition of this material formed a layer of ash ranging from 25 centimeters to 3 meters thick, and much more near the volcano. The amount of ash was so great that for 60 hours there was complete darkness around the volcano at a distance of 160 kilometers. On June 11, volcanic dust fell in Vancouver and Victoria at a distance of 2200 km from the volcano. IN upper layers atmosphere it spread throughout the entire territory North America and fell in large quantities in the Pacific Ocean. Whole year fine particles ash moved in the atmosphere. Summer across the planet turned out to be much colder than usual, since more than a quarter of the sun's rays falling on the planet were retained in the ash curtain. In addition, in 1912, amazingly beautiful scarlet dawns were celebrated everywhere. At the site of the crater, a lake with a diameter of 1.5 kilometers formed - the main attraction of the lake formed in 1980. National Park and Katmai Nature Reserve.

December 13-28, 1931 an eruption occurred volcano Merapi on the island of Java in Indonesia. Over two weeks, from December 13 to 28, the volcano erupted a stream of lava about seven kilometers long, up to 180 meters wide and up to 30 meters deep. The white-hot stream scorched the earth, burned the trees and destroyed all the villages in its path. In addition, both slopes of the volcano exploded, and erupted volcanic ash covered half of the island of the same name. During this eruption, 1,300 people died. The eruption of Mount Merapi in 1931 was the most destructive, but far from the last.

In 1976, a volcanic eruption killed 28 people and destroyed 300 houses. The significant morphological changes that took place in the volcano caused another disaster. In 1994, the dome that had formed in previous years collapsed, and the resulting massive release of pyroclastic material forced the local population to leave their villages. 43 people died.

In 2010, the number of victims from the central part of the Indonesian island of Java was 304 people. The list of dead included those who died from exacerbations of lung and heart diseases caused by ash emissions and other chronic diseases, as well as those who died from injuries.

November 12, 1985 eruption began Ruiz Volcano in Colombia, considered extinct. On November 13, several explosions were heard one after another. The power of the strongest explosion, according to experts, was about 10 megatons. A column of ash and rock debris rose into the sky to a height of eight kilometers. The eruption that began caused the instant melting of the vast glaciers and eternal snow lying on the top of the volcano. The main blow fell on the city of Armero, located 50 kilometers from the mountain, which was destroyed in 10 minutes. Of the 28.7 thousand residents of the city, 21 thousand died. Not only Armero was destroyed, but also a number of villages. The following were severely damaged by the eruption: settlements, like Chinchino, Libano, Murillo, Casabianca and others. Mudflows Oil pipelines were damaged and fuel supplies to the southern and western parts of the country were cut off. As a result of the sudden melting of the snow lying in the Nevado Ruiz Mountains, nearby rivers overflowed their banks. Powerful streams of water washed away car roads, demolished power line and telephone poles, destroyed bridges. According to the official statement of the Colombian government, as a result of the eruption of the Ruiz volcano, 23 thousand people died or went missing, about five thousand were seriously injured and maimed. About 4,500 residential buildings and administrative buildings were completely destroyed. Tens of thousands of people were left homeless and without any means of subsistence. Colombia's economy suffered significant damage.

June 10-15, 1991 an eruption occurred Volcano Pinatubo on the island of Luzon in the Philippines. The eruption began quite quickly and was unexpected, since the volcano became active after more than six centuries of hibernation. On June 12, the volcano exploded, throwing a mushroom cloud into the sky. Streams of gas, ash and rocks melted to a temperature of 980°C rushed down the slopes at speeds of up to 100 kilometers per hour. For many kilometers around, all the way to Manila, day turned into night. And the cloud and the ash falling from it reached Singapore, which is 2.4 thousand kilometers away from the volcano. On the night of June 12 and the morning of June 13, the volcano erupted again, throwing ash and flames 24 kilometers into the air. The volcano continued to erupt on June 15 and 16. Mud flows and water washed away houses. As a result of numerous eruptions, approximately 200 people died and 100 thousand were left homeless

The material was prepared based on information from open sources

A truly amazing sight - 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 so vulnerable spot on the surface, which 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, this may occur. dangerous phenomenon like a tsunami.

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

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 waters with minerals dissolved in them emerge.

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

Information sources

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 rise on the surface of the Earth from the products of volcanic ejection;

- 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 height 4750 m.

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 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

Contemporary volcanic activity in the area Russian Federation 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 Eastern Siberia(Kropotkin volcano, active 500-1000 years ago), Chukotka (Anyuysky volcano, active 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 Bezymyanny 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.

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. As, for example, on the Mauna Loa volcano on Hawaiian Islands where it flows straight 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 classified as geological emergency situations which 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 conditions of oceans and seas are characterized by the formation large quantity steam generated by the contact of hot magma and sea water.

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 directed channel for lava, which saved nearby villages from the threat.

Sometimes cooling helps lava flow water - 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 towards 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 things, 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 100 tremors per hour. Then scientists install seismographs on the volcano to take measurements.

Sometimes it's 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, changing their chemical composition. Temperature underground water also increases. 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.

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.