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Volcanoes of the world: active and extinct volcanoes. Volcanoes

Many times on television and in films we have seen terrible pictures of volcanic eruptions: the sky covered with huge clouds of ash, hot lava flows, deadly stone bombs flying from the sky, rivers overflowing their banks, rockfalls - all this amazes the imagination.


Let's figure out why all this end of the world is happening.

What is a volcano?

“It’s a no brainer what it is,” someone will say. Maybe some hedgehogs advanced in volcanology don’t need any explanation, but we’ll try to figure it out.

The first thing that comes to mind is that a volcano is a mountain. But not a simple mountain, but one spitting out all sorts of magmas, lavas, ashes, slags and the like. The name immediately comes to mind, firmly etched into it - Eyjafjallajökull, the bearer of which caused the whole world to go “dark” in 2010.

So, a volcano is a geological formation on the surface of the Earth (or another planet), where magma comes to the surface and, turning into lava, creates all sorts of disgrace. This terrible and, at the same time, beautiful process in its titanic grandeur is called an eruption.

Why do eruptions occur?

Let's try to answer this question clearly. The fact is that the Earth is a young planet (what, really, four and a half billion years is zilch), a teenager, one might say. Which one the main problem among teenagers? That's right - acne. Here is the answer to your question.

And if we speak seriously and with a scientific expression on our face, then all eruptions occur for one reason - magma breaks through a layer of the earth’s crust. This can happen due to a break in the crust, or it can be caused by the approach of one or another to the Earth, with their attraction forcing the magma to put more pressure on the earth’s crust. There may be some other reasons, hitherto hidden from the inquiring minds of volcanologists.


One of the mysteries that men in white coats puzzle over to this day is the source of heat sufficient to melt the huge masses of basalt that make up the crust. Three hypotheses claim to provide a rational explanation for the appearance of heat sources of such power.

Some of the above-mentioned men believe that radioactive elements gathered together are to blame. Others object: “Well, where can they get them in such volumes?! No, tectonic shifts and faults are to blame!” Still others glance slyly at one and the other, and, pinching the ends of their thin mustache or beard, quietly but forcefully object: “Eh, no, colleagues. If only everything were so simple... We have reason to believe that the culprit is the so-called phase transition, which occurs due to the fact that the mantle, which is usually in a solid state under high pressure conditions, due to a fault and the naturally subsequent decrease in pressure turns into a liquid state, releasing this transition a colossal amount of thermal energy. Definitely!"

Why is a volcanic eruption dangerous?

This is something that any hedgehog can understand, even those without a volcanological background. To not understand this, you need to reach the level of stupidity of the possum brothers Crash and Eddie from " Ice Age" In the fourth part of the cartoon, they reveal to the mole Louis that the secret of their carelessness in the conditions of a terrible cataclysm lies precisely in this...

Well, if anyone doesn’t understand, we’ll explain... It’s not difficult for us...

When a volcano erupts, lava flows out of it. It's very beautiful, but you can't take it in your hands - you'll get burned. It's better not to approach her at all. And there are also large hot pebbles flying from the volcano far, far away. It will be very painful and hot if they get hit.


If it's on the head, that's it. And volcanoes smoke very strongly - you can suffocate. And sometimes they smoke for so long that you can even freeze, because the smoke does not allow the sun to warm us.

Classification of volcanoes

There are three main criteria by which volcanoes are classified - shape, activity and location.

According to their shape, volcanoes are divided into shield, dome, stratovolcanoes and cinder cones; according to activity - active, dormant and extinct; by location - underground, underwater and subglacial.

We will not analyze the features of each of these types, since this will go beyond the scope of an educational article and will take a little time treatise.

What to do during a volcanic eruption?

Lava has a movement speed of about 40 km/h. If you have a car and you are sure that you will not get stuck in a traffic jam, burn rubber before it’s too late, taking with you something to drink and something to eat. Don't let the ash get under the hood - the engine will stall.

If there is a traffic jam, and you are running with a backpack, push as hard as you can, first putting on thick clothes and taking gauze bandages to protect against gases. You need to take grub and other necessities with you for approximately 5 days.


Do not go down into the lowlands - flooding is possible during an eruption. When there are rockfalls, sit with your back to them, covering your head with your hands. If possible, protect your back with something like boards or plywood. Place the children in front of you.

If you don’t have a level in running, you’re at home, but you don’t want to go outside, close all the windows, doors and ventilation holes, climb to the very top and wait for it to blow by. We are waiting for what will blow by, standing - there are gases near the floor that will knock you out.

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 earth's crust there is a hole, crack or weakness. 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 next to 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. 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 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 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.

Despite their deadly nature, various volcanoes have long attracted people. Previously, people were attracted by fertile soils, enriched with minerals and trace elements due to the activity of volcanoes, now tourists are attracted by the beauty and majesty of these natural sites.

Where are the largest volcanoes on the world map?

Most of the modern active volcanoes are located in Pacific volcanic ring- the area in which the largest number of eruptions and 90% of earthquakes on our planet occur.

The second most powerful seismic zone is the Mediterranean fold belt, which stretches from the Indonesian islands to.

The strongest eruption in history

The most destructive eruption in terms of its consequences is considered to be the catastrophe that occurred in 1883 during the explosion Krakatoa volcano located in . During this cataclysm, more than 36 thousand people died, more than 165 cities and villages were completely destroyed, and ash was released to a height of 70 kilometers.

The force of the explosion during the eruption exceeded the force of a nuclear bomb over Hiroshima by 10 thousand times. Most deaths are a consequence of huge tsunami caused by the eruption. The island on which Krakatoa was located was almost completely destroyed during the disaster. The sound of the explosion spread over a distance of 5 thousand kilometers from the epicenter of the disaster.

Earth's Greatest Active Volcanic Mountains

The largest active volcanoes in the world by volume:

  • Mauna Loa, Hawaii, with a volume of 80 thousand cubic kilometers;
  • Kilimanjaro(Tanzania), which is considered dormant but could potentially become active, has a volume of 4,800 cubic kilometers;
  • Volcano Sierra Negra, located in the Galapagos Islands (Ecuador) has a volume of 580 cubic kilometers.

Which country has the largest source of lava?

In terms of size, there is no equal to the Hawaiian volcano Mauna Loa, which has a volume of 80 thousand cubic kilometers. The title of the highest is disputed by 2 volcanoes from South America:

  1. Llullaillaco, located on the border of Argentina and Chile with an altitude of more than 6 thousand meters;
  2. Cotopaxi, located in Ecuador with an altitude of 5897 meters.

Description with names

There are between 1000 and 1500 active volcanoes on our planet. Many of them are located near densely populated areas and pose a threat to human life. The most dangerous volcanoes, which are under special surveillance, are included in UN Decade Volcanoes list.

Merapi

Merapi, which means in Indonesian "mountain of fire", recognized as one of the most dangerous volcanoes in Asia. It is located in the south of the island of Java in Indonesia, and its peak rises to a height of 3 thousand meters.

Significant eruptions of Merapi occur at intervals of approximately 7 years; throughout its history, Merapi has repeatedly caused the death of many people. In 1930, the eruption killed 1,400 people, and in 2010 more than 350 thousand people had to be evacuated, killing 353 island residents.

Located near Merapi Yogyakarta city, in the agglomeration of which more than 2 million people live. Due to its activity and danger to human life, Merapi is included in the list of Volcanoes of the Decade.

Sakurajima

Sakurazdima Volcano (Japan) is located on Kyushu island, its peak rises to a height of 1110 meters. The first eruption recorded by chronicles occurred in 963, and the most powerful one dates back to 1914, but thanks to the tremors that preceded it, most of the local residents managed to evacuate, and “only” 35 people died.

Since the mid-20th century, the volcano has been constantly active. Happen every year thousands of small explosions and ash emissions.

In 2013, there was a large ash emission reaching a height of 4000 meters.

Sakurajima is also on the list of Volcanoes of the Decade.

Aso

Volcano Aso is also located on Kyushu island in Japan. The highest point of Aso is at an altitude of 1592 meters. During the period of observation of the volcano, about 165 large and medium eruptions occurred, many of which resulted in human casualties.

The last time people died as a result of a volcanic eruption was in 1979, when 3 people died and 11 were injured. But Aso is dangerous not only for its eruptions, poisonous volcanic gas fumes They regularly poison tourists who try to conquer Aso. The last such incident occurred in 1997, when two climbers died.

Last eruption Aso was noted in 2011, ash emission occurred to a height of up to 2 kilometers.

If you travel by plane, then you will be interested, from which you will find out how the seats on the plane are located and which ones are the most comfortable.

Nyiragongo

Nyiragongo is located in the territory DR Congo in the Virunga mountain system (Africa). In the crater of the volcano there is the world's largest lava lake, the depth of which can reach 3 kilometers. In 1977, the crater wall ruptured, causing a large flow of lava into the surrounding area, ultimately killing 70 people.

During observations of Nyiragongo since 1882, it was recorded 34 major volcanic eruptions. A feature of the Nyiragongo eruptions is the extremely rapid flow of lava, reaching speeds of 100 kilometers per hour. During a major eruption in 2002, 400 thousand residents of the city of Goma, located near the volcano, were evacuated. Nevertheless, 147 of them died as a result of this cataclysm, and the city itself suffered significant damage.

All these factors make Nyiragongo one of the the most dangerous volcanoes on the planet, for which he was rightly included in the list of Volcanoes of the Decade.

Galeras

The Galeras volcano is located in Colombia near the city of Pasto, whose population is more than 400 thousand people. Its height exceeds 4200 meters. Due to its danger, Galeras was included in the list of Volcanoes of the Decade, representing greatest threat in foreseeable future.

It is believed that over the past 7,000 years, Galeras has experienced at least 6 major eruptions, the last of which was recorded in 1993.

Mauna Loa

The Mauna Loa volcano is located on Hawaiian Islands belonging to the United States of America. This giant volcano occupies more than half the area of ​​Hawaii, the height of the peak above sea level is 4169 meters, but most of the volcano is located under water. Together with the underwater part, its height from base to top reaches 9170 meters, which exceeds the height of Everest.

Mauna Loa erupts according to what is called Hawaiian type with an outpouring of lava, but without explosions and large ash emissions. Observations of the volcano have been carried out only since 1832, but during this time 39 major eruptions of Mauna Loa have been recorded. This volcano was included in the list of Volcanoes of the Decade due to the huge lava flows accompanying the eruption and the densely populated area in its immediate vicinity.

The summit of the volcano and its slopes were included in the list World Heritage UNESCO.

Colima

The most active volcano in Central America located in the state of Jalisco. Thanks to her activity, Colima received the nickname "little Vesuvius", its height exceeds 3800 meters.

Over the past 450 years, more than 40 large and medium-sized volcanic eruptions have been recorded, the last of which occurred on September 12, 2016. More than 400 thousand people live near Colima, making it America's most dangerous volcano. For this reason, the volcano was included in the list of Volcanoes of the Decade.

And you will learn about the largest cities in the world - the most densely populated, the longest, and others.

Vesuvius

The most famous volcano in the world is located on the Apennine Peninsula in. The lonely peak of Vesuvius, 1281 meters high, rises above the vast fields of the province of Campania and is part of the Apennine mountain system.

Located just 15 kilometers from Naples, Vesuvius has repeatedly gone down in history with its catastrophic eruptions; about 80 major ones alone were recorded. In 79 AD, the most destructive eruption of Vesuvius, during which famous cities perished:

  • Pompeii;
  • Oplontis;
  • Herculaneum;
  • Stabiae.

It is believed that at least 16 thousand people died during this disaster.

In 1944, the last eruption of Vesuvius occurred, during which cities were destroyed Weight And San Sebastiano, 27 people became victims. Since then, Vesuvius has not shown strong activity, but the danger of a new eruption always remains. Vesuvius is one of the main attractions of the province of Campania and its visit is included in the excursion tour when traveling to Naples.

Etna

Another famous volcano in Italy is located in the east of the island of Sicily and is the highest volcano, rising to a height of 2329 meters. Etna erupts several times a year. History has recorded several major eruptions of this volcano that led to devastating consequences:

  1. Was destroyed in 122 AD Catania city;
  2. In 1169, during the large-scale eruption of Etna, they died 15 thousand people;
  3. In 1669, Catania suffered again, houses were destroyed 27 thousand people;
  4. In 1928, the ancient Maskali city.

Despite the danger of the volcano, the inhabitants of the island continue to settle on its slopes. The reason for this is fertile soil, enriched with minerals and trace elements contained in cooled lava flows and ash.

Etna is one of the main natural attractions of Sicily; tourists from all over the world come to see the volcano and climb to its top.

Popocatepetl

Volcano Popocatepetl, or El Popo as they affectionately call him local residents, is located in Mexico, 70 kilometers from the capital of this country, Mexico City. The height of the volcano is almost 5500 meters. Popocatépetl has erupted more than 15 times over the past 500 years, with the most recent one occurring as recently as 2015. An extinct volcano is located near Popocatepetl. Iztaccihuatl.

A trip to these volcanoes is an integral part of the excursion program when visiting Mexico City.

Klyuchevskaya Sopka

The highest volcano in Eurasia is located on the Kamchatka Peninsula and is considered the most famous of the many volcanoes of Kamchatka. The highest point outside the Caucasus Mountains reaches an altitude of 4750 meters. It is the most active volcano in Eurasia, with an average of almost every year. The last significant eruption occurred in 2013, the height of the ash emission was 10-12 kilometers. The eruption was accompanied by mud flows and ashfall.

Cotopaxi

The active Cotopaxi volcano is located in South America on the territory of the state Ecuador part of the Andes mountain system. The height of the peak of Cotopaxi is 5897 meters. In the entire history of observations, 86 eruptions have been recorded, the largest of which led to the complete destruction of the city of Latacunga in 1786. Last Activity Cotopaxi was discovered in 1942, after which the volcano remains dormant.

Famous extinct giants

In addition to active volcanoes, there are many extinct volcanoes on our planet that do not exhibit volcanic activity.

Supreme

The tallest extinct volcano on the planet, Aconcagua, is located in Argentina and is part of the Andes mountain system. Aconcagua is not only the highest extinct volcano in the world, but also the highest peak in the Americas, Western and Southern Hemispheres. The height of Aconcagua exceeds 6950 meters.

Sleeping giants

Many extinct volcanoes are now considered simply mountains, although some of them could potentially “wake up” and begin to become active. Such volcanoes, which may become active in the future, are called "sleeping".

  • Famous Mount Kilimanjaro in Tanzania (Africa) is a dormant volcano that is not active. Scientists believe that one day Kilimanjaro may wake up, then this potential volcano will become one of the highest in the world, because the height of Kilimanjaro is 5895 meters above sea level.

    • Colossal supervolcano Yellowstone was considered extinct, but scientists have found that there is little activity in it, so now Yellowstone is classified as a dormant volcano. The giant last erupted almost a million years ago.

    It is believed that if Yellowstone wakes up, a potential eruption will become one of the largest disasters in the history of the Earth, every third inhabitant of the planet will die, and several US states will be completely destroyed.

    Yellowstone eruption will provoke many earthquakes, giant tsunami waves and other volcanic eruptions, which will affect almost every inhabitant of the planet. The ash ejected by the volcano will cover the surface of the earth from the sun for a year and a half, and a volcanic winter will occur throughout the planet.

    However, not all scientists believe that the consequences of this cataclysm will be so serious. In any case, the eruption of this volcano remains one of the main potential threats to humans.

  • The largest extinct volcano in Russia is 5642 meters. It is located on the border of the republics of Kabardino-Balkaria and Karachay-Cherkessia. Refers to the list of the highest peaks in six parts of the world. Scientists consider the activity of the volcano not so much completed as fading.
  • The largest volcano of our time cannot be visited and is very difficult to see, since it is located under water. Array Tamu located at the bottom of the Pacific Ocean and is located approximately 1,600 kilometers east of the Japanese Islands. Its dimensions are 650 by 450 kilometers; in scale, the array is one of the largest not only on Earth, but in the entire solar system. The last volcanic eruption occurred 140 million years ago.
  • Dormant volcanoes Big and Small Ararat are now located on the territory and belong to the category of volcanoes that do not exhibit volcanic activity. The peak of Mount Great Ararat, reaching 5165 meters, is highest point Turkey.
  • One of the highest peaks of the Caucasus, Mount Kazbek is also an extinct volcano. Kazbek is located on the border with Russia, the top point of the mountain is located at an altitude of more than 5 kilometers. During research, volcanic ash from an eruption that allegedly occurred 40 thousand years ago was found in one of the Kazbek caves.

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Watch a video about these and other volcanoes in the world:

VOLCANOES
separate elevations above channels and cracks in the earth's crust, along which eruption products are brought to the surface from deep magma chambers. Volcanoes usually have the shape of a cone with a summit crater (from several to hundreds of meters deep and up to 1.5 km in diameter). 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.


MAIN TYPES OF VOLCANOES The extrusive (lava) dome (left) has a rounded shape and steep slopes cut by deep grooves. A plug of frozen lava may form in the crater of a volcano, which prevents the release of gases, which subsequently leads to an explosion and destruction of the dome. The steeply inclined pyroclastic cone (right) is composed of alternating layers of ash and slag.




Active volcanoes include those that erupted in historical times or showed other signs of activity (emission of gases and steam, etc.). Some scientists consider active volcanoes that are reliably known to have erupted within the last 10 thousand years. For example, the Arenal volcano in Costa Rica should be considered active, since archaeological excavations parking primitive man Volcanic ash was discovered in the area, although the first eruption in human memory occurred in 1968, and before that there were no signs of activity. see also VOLCANISM.





Volcanoes are known not only on Earth. Images taken from spacecraft reveal huge ancient craters on Mars and many active volcanoes on Io, a moon of Jupiter.
VOLCANIC PRODUCTS
Lava is magma that flows onto earth's surface during eruptions, and then hardens. Lava eruptions can come from the main summit crater, a side crater on the side of the volcano, or from fissures associated with a volcanic chamber. It flows down the slope as a lava flow. In some cases, lava outpourings occur in rift zones of enormous extent. For example, in Iceland in 1783, within the chain of Laki craters, stretching along a tectonic fault for a distance of approx. 20 km, there was an outpouring of VOLCANA 12.5 km3 of lava, distributed over an area of ​​VOLCANA 570 km2.



Composition of lava. The hard rocks formed when lava cools contain mainly silicon dioxide, oxides of aluminum, iron, magnesium, calcium, sodium, potassium, titanium and water. Typically, lavas contain more than one percent of each of these components, and many other elements are present in smaller quantities.
There are many types of volcanic rocks, varying in chemical composition. Most often there are four types, the membership of which is determined by the content of silicon dioxide in the rock: basalt - 48-53%, andesite - 54-62%, dacite - 63-70%, rhyolite - 70-76% (see table). Rocks that contain less silicon dioxide contain large amounts of magnesium and iron. When lava cools, a significant part of the melt forms volcanic glass, in the mass of which individual microscopic crystals are found. The exception is the so-called phenocrystals are large crystals formed in magma in the depths of the Earth and brought to the surface by a flow of liquid lava. Most often, phenocrysts are represented by feldspars, olivine, pyroxene and quartz. Rocks containing phenocrysts are usually called porphyrites. The color of volcanic glass depends on the amount of iron present in it: the more iron, the darker it is. Thus, even without chemical analysis, one can guess that a light-colored rock is rhyolite or dacite, a dark-colored rock is basalt, and a gray rock is andesite. The type of rock is determined by the minerals visible in the rock. For example, olivine, a mineral containing iron and magnesium, is characteristic of basalts, and quartz is characteristic of rhyolites. As the magma rises to the surface, the released gases form tiny bubbles with a diameter often up to 1.5 mm, less often up to 2.5 cm. They are stored in the solidified rock. This is how bubbly lavas are formed. Depending on the chemical composition Lavas vary in viscosity, or fluidity. At high content Silicon dioxide (silica) lava is characterized by high viscosity. Viscosity of magma and lava in to a large extent determines the nature of the eruption and the type of volcanic products. Liquid basaltic lavas with low silica content form extensive lava flows more than 100 km long (for example, one lava flow in Iceland is known to stretch for 145 km). The thickness of lava flows is usually from 3 to 15 m. More liquid lavas form thinner flows. Flows 3-5 m thick are common in Hawaii. When the surface of a basalt flow begins to solidify, its interior may remain liquid, continuing to flow and leaving behind an elongated cavity, or lava tunnel. For example, on the island of Lanzarote (Canary Islands) a large lava tunnel can be traced for 5 km. The surface of a lava flow can be smooth and wavy (in Hawaii, such lava is called pahoehoe) or uneven (aa-lava). Hot lava, which is highly fluid, can move at speeds of more than 35 km/h, but more often its speed does not exceed several meters per hour. In a slow-moving flow, pieces of the solidified upper crust may fall off and be covered by lava; As a result, a zone enriched with debris is formed in the near-bottom part. When lava hardens, columnar units (multifaceted vertical columns with a diameter of several centimeters to 3 m) or fracturing perpendicular to the cooling surface are sometimes formed. When lava flows into a crater or caldera, a lava lake forms and cools over time. For example, such a lake formed in one of the craters of the Kilauea volcano on the island of Hawaii during the eruptions of 1967-1968, when lava entered this crater at a speed of 1.1 * 10 6 m3/h (part of the lava subsequently returned to the crater of the volcano). In neighboring craters, within 6 months the thickness of the crust of solidified lava on lava lakes reached 6.4 m. Domes, maars and tuff rings. Very viscous lava (most often of dacite composition) during eruptions through the main crater or side cracks does not form flows, but a dome with a diameter of up to 1.5 km and a height of up to 600 m. For example, such a dome was formed in the crater of Mount St. Helens (USA) after an exceptionally strong eruption in May 1980. The pressure under the dome can build up, and weeks, months or years later it can be destroyed by the next eruption. IN separate parts In the dome, magma rises higher than in others, and as a result, volcanic obelisks protrude above its surface - blocks or spiers of solidified lava, often tens and hundreds of meters high. After the catastrophic eruption of the Montagne Pelee volcano on the island of Martinique in 1902, a lava spire formed in the crater, which grew by 9 m per day and as a result reached a height of 250 m, and collapsed a year later. On the Usu volcano on Hokkaido (Japan) in 1942, during the first three months after the eruption, the Showa-Shinzan lava dome grew by 200 m. The viscous lava that composed it made its way through the thickness of the previously formed sediments. Maar is a volcanic crater formed during an explosive eruption (most often with high humidity of the rocks) without the outpouring of lava. A ring shaft of debris ejected by the explosion is not formed, unlike tuff rings - also explosion craters, which are usually surrounded by rings of debris products. The debris released into the air during an eruption is called tephra, or pyroclastic debris. The deposits they form are also called. Fragments of pyroclastic rocks are different sizes . The largest of them are volcanic blocks. If the products are so liquid at the time of release that they solidify and take shape while still in the air, then the so-called. volcanic bombs. Material smaller than 0.4 cm in size is classified as ashes, and fragments ranging in size from a pea to a walnut are classified as lapilli. Hardened deposits composed of lapilli are called lapilli tuff. There are several types of tephra, differing in color and porosity. Light-colored, porous, non-sinking tephra is called pumice. Dark vesicular tephra, consisting of lapilli-sized units, is called volcanic scoria. Pieces of liquid lava that remain in the air for a short time and do not have time to completely harden form splashes, often forming small spatter cones near the outlets of lava flows. If this spatter sinteres, the resulting pyroclastic deposits are called agglutinates. A mixture of very fine pyroclastic material and heated gas suspended in the air, ejected from a crater or fissures during an eruption and moving above the ground surface at a speed of 100 km/h VOLCANOES, forms ash flows. They spread over many kilometers, sometimes crossing waters and hills. These formations are also known as scorching clouds; they are so hot that they glow at night. Ash flows may also contain large debris, incl. and pieces of rock torn out from the walls of a volcano. Most often, scorching clouds are formed when a column of ash and gases ejected vertically from a vent collapses. Under the influence of gravity, counteracting the pressure of the erupting gases, the edges of the column begin to settle and descend down the slope of the volcano in the form of a hot avalanche. In some cases, scorching clouds appear along the periphery of a volcanic dome or at the base of a volcanic obelisk. It is also possible for them to be released from the ring cracks around the caldera. Ash flow deposits form the ignimbrite volcanic rock. These flows transport both small and large fragments of pumice. If ignimbrites are deposited thick enough, the internal horizons can be so hot that the pumice fragments melt to form sintered ignimbrite, or sintered tuff. As the rock cools, columnar formations may form in its interior, which are less clear-cut and larger than similar structures in lava flows. Small hills consisting of ash and blocks of various sizes are formed as a result of a directed volcanic explosion (as, for example, during the eruptions of Mount St. Helens in 1980 and Bezymyanny in Kamchatka in 1965).
Directed volcanic explosions are quite a rare event. The deposits they create are easily confused with the clastic deposits with which they are often adjacent. For example, during the eruption of Mount St. Helens, an avalanche of rubble occurred immediately before the directed explosion.
Underwater volcanic eruptions. If there is a body of water above the volcanic source, during the eruption the pyroclastic material is saturated with water and spreads around the source. This type of deposit, first described in the Philippines, was formed as a result of the 1968 eruption of Taal Volcano, located at the bottom of the lake; they are often represented by thin wavy layers of pumice.
We sat down. Volcanic eruptions may be associated with mudflows or mud-stone flows. They are sometimes called lahars (originally described in Indonesia). The formation of lahars is not part of the volcanic process, but one of its consequences. On the slopes of active volcanoes, loose material (ash, lapilli, volcanic debris) accumulates in abundance, ejected from volcanoes or falling from scorching clouds. This material is easily involved in the movement of water after rains, when ice and snow melt on the slopes of volcanoes or when the sides of crater lakes break through. Mud streams rush down the riverbeds at great speed. During the eruption of the Ruiz volcano in Colombia in November 1985, mudflows moving at speeds above 40 km/h carried more than 40 million m3 of debris onto the foothill plain. At the same time, the city of Armero was destroyed and approx. 20 thousand people. Most often, such mudflows occur during an eruption or immediately after it. This is explained by the fact that during eruptions, accompanied by the release of thermal energy, snow and ice melt, crater lakes break through and drain, and slope stability is disrupted. The gases released from the magma before and after the eruption look like white streams of water vapor. When tephra is mixed with them during an eruption, the emissions become gray or black. Low gas emissions in volcanic areas can continue for years. Such releases of hot gases and vapors through openings at the bottom of the crater or the slopes of the volcano, as well as on the surface of lava or ash flows, are called fumaroles. Special types of fumaroles include solfataras, containing sulfur compounds, and mofets, in which carbon dioxide predominates. The temperature of fumarole gases is close to the temperature of magma and can reach 800 ° C, but it can also drop to the boiling point of water (VOLCANOES 100 ° C), the vapors of which serve as the main component of fumaroles. Fumarole gases originate both in shallow near-surface horizons and at great depths in hot rocks. In 1912, as a result of the eruption of the Novarupta volcano in Alaska, the famous Valley of Ten Thousand Smokes was formed, where on the surface of volcanic emissions an area of ​​approx. 120 km2, many high-temperature fumaroles arose. Currently, only a few fumaroles with fairly low temperatures are active in the Valley. Sometimes white streams of steam rise from the surface of a lava flow that has not yet cooled; most often it is rainwater heated by contact with a hot lava flow.
Chemical composition of volcanic gases. The gas released from volcanoes consists of 50-85% water vapor. Over 10% is carbon dioxide, approx. 5% is sulfur dioxide, 2-5% is hydrogen chloride and 0.02-0.05% is hydrogen fluoride. Hydrogen sulfide and sulfur gas are usually found in small quantities. Sometimes hydrogen, methane and carbon monoxide are present, as well as small amounts of various metals. Ammonia was found in gas emissions from the surface of a lava flow covered with vegetation. Tsunamis are huge sea waves, associated mainly with underwater earthquakes, but sometimes caused by volcanic eruptions on the ocean floor, which can cause the formation of several waves, occurring at intervals of several minutes to several hours. The eruption of the Krakatoa volcano on August 26, 1883 and the subsequent collapse of its caldera was accompanied by a tsunami over 30 m high, causing numerous casualties on the coasts of Java and Sumatra.
TYPES OF ERUPTIONS
Products arriving at the surface during volcanic eruptions vary significantly in composition and volume. The eruptions themselves vary in intensity and duration. The most commonly used classification of eruption types is based on these characteristics. But it happens that the nature of eruptions changes from one event to another, and sometimes during the same eruption. The Plinian type is named after the Roman scientist Pliny the Elder, who died in the eruption of Vesuvius in 79 AD. Eruptions of this type are characterized by the greatest intensity (eruptions are thrown into the atmosphere to a height of 20-50 km). a large number of ash) and occur continuously over several hours and even days. Pumice of dacite or rhyolite composition is formed from viscous lava. Products of volcanic emissions cover a large area, and their volume ranges from 0.1 to 50 km3 or more. An eruption may result in the collapse of a volcanic structure and the formation of a caldera. Sometimes an eruption produces scorching clouds, but lava flows are not always formed. Fine ash strong wind at speeds of up to 100 km/h it spreads over long distances. Ash emitted in 1932 by the Cerro Azul volcano in Chile was discovered 3,000 km away. The strong eruption of Mount St. Helens (Washington, USA) on May 18, 1980, when the height of the eruptive column reached 6000 m, also belongs to the Plinian type. During 10 hours of continuous eruption, approx. 0.1 km3 of tephra and more than 2.35 tons of sulfur dioxide. During the eruption of Krakatoa (Indonesia) in 1883, the volume of tephra was 18 km3, and the ash cloud rose to a height of 80 km. The main phase of this eruption lasted approximately 18 hours. An analysis of the 25 most violent historical eruptions shows that the quiet periods preceding Plinian eruptions averaged 865 years.
Peleian type. Eruptions of this type are characterized by very viscous lava, which hardens before leaving the vent with the formation of one or several extrusive domes, the squeezing of the obelisk above it, and the emission of scorching clouds. The 1902 eruption of the Montagne-Pele volcano on the island of Martinique belonged to this type.
Vulcan type. Eruptions of this type (the name comes from the island of Vulcano in the Mediterranean Sea) are short-lived - from a few minutes to a few hours, but recur every few days or weeks for several months. The height of the eruptive column reaches 20 km. The magma is fluid, basaltic or andesitic in composition. The formation of lava flows is typical, and ash emissions and extrusive domes do not always occur. Volcanic structures are built from lava and pyroclastic material (stratovolcanoes). The volume of such volcanic structures is quite large - from 10 to 100 km3. The age of stratovolcanoes ranges from 10,000 to 100,000 years. The frequency of eruptions of individual volcanoes has not been established. This type includes the Fuego volcano in Guatemala, which erupts every few years; basaltic ash emissions sometimes reach the stratosphere, and their volume during one of the eruptions was 0.1 km3.
Strombolian type. This type is named after the volcanic island. Stromboli in the Mediterranean Sea. The Strombolian eruption is characterized by continuous eruptive activity over several months or even years and a not very high height of the eruptive column (rarely above 10 km). There are known cases when lava was splashed within a 300 m radius of VOLCANA, but almost all of it returned to the crater. Lava flows are typical. Ash covers have a smaller area than during Vulcan-type eruptions. The composition of eruption products is usually basaltic, less often - andesitic. The Stromboli volcano has been active for more than 400 years, the Yasur volcano on Tanna Island (Vanuatu) in the Pacific Ocean has been active for more than 200 years. The structure of the vents and the nature of the eruptions of these volcanoes are very similar. Some Strombolian-type eruptions produce cinder cones composed of basaltic or, less commonly, andesitic scoria. The diameter of the cinder cone at the base ranges from 0.25 to 2.5 km, the average height is 170 m. Cinder cones are usually formed during a single eruption, and volcanoes are called monogenic. For example, during the eruption of the Paricutin volcano (Mexico) during the period from the beginning of its activity on February 20, 1943 to the end on March 9, 1952, a cone of volcanic slag 300 m high was formed, the surrounding area was covered with ash, and the lava spread over an area of ​​18 km2 and destroyed several populated areas .
Hawaiian type eruptions are characterized by outpourings of liquid basaltic lava. Fountains of lava ejected from cracks or faults can reach a height of 1000 and sometimes 2000 m. Few pyroclastic products are ejected; most of them are splashes falling near the source of the eruption. Lavas flow from fissures, holes (vents) along a fissure, or craters, sometimes containing lava lakes. When there is only one vent, the lava spreads radially, forming a shield volcano with very gentle slopes - up to 10° (stratovolcanoes have cinder cones and slope steepness of about 30°). Shield volcanoes are composed of layers of relatively thin lava flows and do not contain ash (for example, the famous volcanoes on the island of Hawaii - Mauna Loa and Kilauea). The first descriptions of volcanoes of this type relate to volcanoes in Iceland (for example, the Krabla volcano in northern Iceland, located in the rift zone). The eruption of the Fournaise volcano on Reunion Island in the Indian Ocean is very close to the Hawaiian type.
Other types of eruptions. Other types of eruptions are known, but they are much less common. An example is the underwater eruption of the Surtsey volcano in Iceland in 1965, which resulted in the formation of an island.
SPREAD OF VOLCANOES
The distribution of volcanoes across the surface of the globe is best explained by the theory of plate tectonics, according to which the Earth's surface consists of a mosaic of moving lithospheric plates. When they move in the opposite direction, a collision occurs, and one of the plates sinks (moves) under the other in the so-called. subduction zone, where earthquake epicenters are located. If the plates move apart, a rift zone forms between them. Manifestations of volcanism are associated with these two situations. Subduction zone volcanoes are located along the boundaries of subducting plates. The oceanic plates that form the floor of the Pacific Ocean are known to subduct beneath continents and island arcs. Subduction areas are marked in the topography of the ocean floor by deep-sea trenches parallel to the coast. It is believed that in zones of plate subduction at depths of 100-150 km, magma is formed, and when it rises to the surface, volcanic eruptions occur. Since the plunging angle of the plate is often close to 45°, volcanoes are located between the land and the deep-sea trench at a distance of approximately 100-150 km from the axis of the latter and in plan form a volcanic arc that follows the contours of the trench and coastline. There is sometimes talk of a "ring of fire" of volcanoes around the Pacific Ocean. However, this ring is intermittent (as, for example, in the region of central and southern California), because subduction does not occur everywhere.




THE GREATEST MOUNTAIN OF JAPAN FUJIYAMA (3776 m above sea level) is the cone of a “dormant” volcano since 1708, covered with snow for most of the year.


Rift zone volcanoes exist in the axial part of the Mid-Atlantic Ridge and along the East African Rift System. There are volcanoes associated with “hot spots” located inside plates in places where mantle plumes (hot magma rich in gases) rise to the surface, for example, the volcanoes of the Hawaiian Islands. It is believed that the chain of these islands, stretched in westward, was formed during the westward drift of the Pacific Plate while moving over a “hot spot”. Now this “hot spot” is located under the active volcanoes of the island of Hawaii. Towards the west of this island, the age of the volcanoes gradually increases. Plate tectonics determines not only the location of volcanoes, but also the type of volcanic activity. The Hawaiian type of eruptions predominates in areas of “hot spots” (Fournaise volcano on Reunion Island) and in rift zones. Plinian, Peleian and Vulcanian types are characteristic of subduction zones. There are also known exceptions, for example, the Strombolian type is observed in various geodynamic conditions. Volcanic activity: recurrence and spatial patterns. Approximately 60 volcanoes erupt annually, and about a third of them erupted in the previous year. There is information about 627 volcanoes that have erupted over the past 10 thousand years, and about 530 in historical time, and 80% of them are confined to subduction zones. The greatest volcanic activity is observed in the Kamchatka and Central American regions, with quieter zones in the Cascade Range, the South Sandwich Islands and southern Chile.
Volcanoes and climate. It is believed that after volcanic eruptions, the average temperature of the Earth’s atmosphere drops by several degrees due to the release of tiny particles (less than 0.001 mm) in the form of aerosols and volcanic dust (while sulfate aerosols and fine dust enter the stratosphere during eruptions) and remains so for 1 -2 years. In all likelihood, such a decrease in temperature was observed after the eruption of Mount Agung on Bali (Indonesia) in 1962.
VOLCANIC HAZARD
Volcanic eruptions threaten human lives and cause property damage. After 1600, as a result of eruptions and associated mudflows and tsunamis, 168 thousand people died, and 95 thousand people became victims of disease and hunger that arose after the eruptions. As a result of the eruption of the Montagne Pelee volcano in 1902, 30 thousand people died. As a result of mudflows from the Ruiz volcano in Colombia in 1985, 20 thousand people died. The eruption of the Krakatoa volcano in 1883 led to the formation of a tsunami that killed 36 thousand people. The nature of the danger depends on the action of various factors. Lava flows destroy buildings, block roads and agricultural lands, which are excluded from economic use for many centuries until new soil is formed as a result of weathering processes. The rate of weathering depends on the amount of precipitation, temperature, runoff conditions and the nature of the surface. For example, on the wetter slopes of Mount Etna in Italy, agriculture on lava flows resumed only 300 years after the eruption. As a result of volcanic eruptions, thick layers of ash accumulate on the roofs of buildings, which threatens their collapse. The entry of tiny ash particles into the lungs leads to the death of livestock. Ash suspended in the air poses a danger to road and air transport. Airports are often closed during ashfalls. Ash flows, which are a hot mixture of suspended dispersed material and volcanic gases, move at high speed. As a result, people, animals, plants die from burns and suffocation and houses are destroyed. The ancient Roman cities of Pompeii and Herculaneum were affected by such flows and were covered with ash during the eruption of Mount Vesuvius. Volcanic gases released by volcanoes of any type rise into the atmosphere and usually cause no harm, but some of them may return to the earth's surface in the form of acid rain. Sometimes the terrain allows volcanic gases (sulfur dioxide, hydrogen chloride or carbon dioxide) to spread near the surface of the earth, destroying vegetation or polluting the air in concentrations exceeding permissible limits. Volcanic gases can also cause indirect harm. Thus, the fluorine compounds contained in them are captured by ash particles, and when the latter fall onto the earth's surface, they contaminate pastures and water bodies, causing severe diseases in livestock. In the same way they can be contaminated open sources water supply to the population. Mud-stone flows and tsunamis also cause enormous destruction.
Eruption forecast. To forecast eruptions, volcanic hazard maps are compiled showing the nature and distribution areas of products of past eruptions, and eruption precursors are monitored. Such precursors include the frequency of weak volcanic earthquakes; If usually their number does not exceed 10 in one day, then immediately before the eruption it increases to several hundred. Instrumental observations of the most minor surface deformations are carried out. The accuracy of measurements of vertical movements, recorded, for example, by laser devices, is VOLCANO 0.25 mm, horizontal - 6 mm, which makes it possible to detect a surface slope of only 1 mm per half kilometer. Data on changes in height, distance and slope are used to identify the center of heave preceding an eruption or surface subsidence after it. Before an eruption, the temperatures of the fumaroles increase, and sometimes the composition of volcanic gases and the intensity of their release change. The precursor phenomena that preceded most of the fairly fully documented eruptions are similar to each other. However, it is very difficult to predict with certainty exactly when an eruption will occur.
Volcanological observatories. To prevent a possible eruption, systematic instrumental observations are carried out in special observatories. The oldest volcanological observatory was founded in 1841-1845 on Vesuvius in Italy, then in 1912 the observatory on the Kilauea volcano on the island of Hawaii began operating and at about the same time several observatories in Japan. Monitoring of volcanoes is also carried out in the USA (including at Mount St. Helens), Indonesia at the observatory at the Merapi volcano on the island of Java, in Iceland, Russia by the Institute of Volcanology of the Russian Academy of Sciences (Kamchatka), Rabaul (Papua - New Guinea), on the islands of Guadeloupe and Martinique in the West Indies, and monitoring programs have been initiated in Costa Rica and Colombia.
Notification methods. Civil authorities, to whom volcanologists provide the necessary information, must warn about impending volcanic danger and take measures to reduce the consequences. The public warning system can be sound (sirens) or light (for example, on the highway at the foot of the Sakurajima volcano in Japan, flashing warning lights warn motorists about ash fall). Warning devices are also installed that are triggered by elevated concentrations of dangerous volcanic gases, such as hydrogen sulfide. Roadblocks are placed on roads in hazardous areas where an eruption is taking place. Reducing the dangers associated with volcanic eruptions. To mitigate volcanic hazards, they are used as complex engineering structures, absolutely simple ways. For example, during the 1985 eruption of Mount Miyakejima in Japan, lava flow front cooling was successfully used. sea ​​water. By creating artificial gaps in the hardened lava that limited the flows on the slopes of volcanoes, it was possible to change their direction. To protect against mud-stone flows - lahars - fencing embankments and dams are used to direct the flows into a certain channel. To avoid the occurrence of lahar, the crater lake is sometimes drained using a tunnel (Kelud volcano on Java in Indonesia). In some areas they install special systems tracking thunderclouds that could bring showers and activate lahars. In places where eruption products fall out, various shelters and safe shelters are built.
LITERATURE
Luchitsky I.V. Fundamentals of paleovolcanology. M., 1971 Melekestsev I.V. Volcanism and relief formation. M., 1980 Vlodavets V.I. Handbook of volcanology. M., 1984 Active volcanoes of Kamchatka, vol. 1-2. M., 1991

Collier's Encyclopedia. - Open Society. 2000 .

IN Ancient Rome The name Vulcan was borne by a mighty god, the patron of fire and blacksmithing. We call volcanoes geological formations on the surface of the land or on the ocean floor, through which lava emerges from the deep bowels of the earth to the surface.

Often accompanied by earthquakes and tsunamis, eruptions large volcanoes had a significant impact on human history.

Geographical object. The importance of volcanoes

During a volcanic eruption, magma emerges through cracks in the earth's crust to the surface, forming lava, volcanic gases, ash, volcanic rocks and pyroclastic flows. Despite the danger that these powerful natural objects, it was thanks to the study of magma, lava and other products of volcanic activity that we were able to gain knowledge about the structure, composition and properties of the lithosphere.

It is believed that thanks to volcanic eruptions, protein forms of life were able to appear on our planet: the eruptions released carbon dioxide and other gases necessary for the formation of the atmosphere. And volcanic ash, settling, became an excellent fertilizer for plants due to the potassium, magnesium and phosphorus it contained.

The role of volcanoes in regulating the climate on Earth is invaluable: during an eruption, our planet “releases steam” and cools, which largely saves us from the consequences of global warming.

Characteristics of volcanoes

Volcanoes differ from other mountains not only in their composition, but also in their strict external outlines. From the craters at the top of the volcanoes, deep narrow ravines formed by flows of water stretch down. There are also entire volcanic mountains formed by several nearby volcanoes and the products of their eruptions.

However, a volcano is not always a mountain breathing fire and heat. Even active volcanoes can appear as straight-line cracks on the surface of the planet. There are especially many such “flat” volcanoes in Iceland (the most famous of them, Eldgja, is 30 km long).

Types of volcanoes

Depending on the degree of volcanic activity there are: current, conditionally active And extinct (“dormant”) volcanoes. The division of volcanoes by activity is very arbitrary. There are cases when volcanoes, considered extinct, began to exhibit seismic activity and even erupt.

Depending on the shape of volcanoes there are:

  • Stratovolcanoes- classic “fire mountains” or volcanoes of the central type, cone-shaped with a crater at the top.
  • Volcanic fissures or fissures- fractures in the earth's crust through which lava comes to the surface.
  • Calderas- depressions, volcanic cauldrons formed as a result of the failure of a volcanic peak.
  • Panel- so called because of the high fluidity of the lava, which, flowing for many kilometers in wide streams, forms a kind of shield.
  • Lava domes - formed by the accumulation of viscous lava above the vent.
  • Cinder or tephra cones- have the shape of a truncated cone, consist of loose materials (ash, volcanic stones, blocks, etc.).
  • Complex volcanoes.

In addition to land-based lava volcanoes, there are underwater And mud(they spew out liquid mud, not magma) Underwater volcanoes are more active than land-based ones; 75% of the lava erupted from the bowels of the Earth is released through them.

Types of volcanic eruptions

Depending on the viscosity of lavas, the composition and amount of eruption products, there are 4 main types of volcanic eruptions.

Effusive or Hawaiian type- a relatively calm eruption of lava formed in craters. The gases released during an eruption form lava fountains from drops, threads and lumps of liquid lava.

Extrusion or dome type- is accompanied by the release of gases in large quantities, leading to explosions and the emission of black clouds from ash and lava debris.

Mixed or Strombolian type- abundant lava output, accompanied by small explosions with ejections of pieces of slag and volcanic bombs.

Hydroexplosive type- typical for underwater volcanoes in shallow water, accompanied by a large amount of steam released when magma comes into contact with water.

The largest volcanoes in the world

The tallest volcano in the world Ojos del Salado, located on the border of Chile and Argentina. Its height is 6891 m, the volcano is considered extinct. Among the active "fire mountains" the highest is Llullaillaco- volcano of the Chilean-Argentine Andes with a height of 6,723 m.

The largest (among terrestrial) volcano in terms of area occupied is Mauna Loa on the island of Hawaii (height - 4,169 m, volume - 75,000 km 3). Mauna Loa also one of the most powerful and active volcanoes in the world: since its “awakening” in 1843, the volcano has erupted 33 times. The most big volcano the planet is a huge volcanic massif Tamu(area 260,000 km2), located at the bottom of the Pacific Ocean.

But the most powerful eruption ever historical period produced "low" Krakatoa(813 m) in 1883 in the Malay Archipelago in Indonesia. Vesuvius(1281) - one of the most dangerous volcanoes world, the only one active volcano continental Europe - located in southern Italy near Naples. Exactly Vesuvius destroyed Pompeii in 79.

In Africa the most high volcano is Kilimanjaro (5895), and in Russia - a double-peaked stratovolcano Elbrus (North Caucasus) (5642 m - western peak, 5621 m - eastern).