What system does the volcano belong to? What is a volcano? Where is the largest volcano located? What is a volcanic eruption

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

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

The science that studies volcanoes is volcanology, geomorphology.

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

Volcanic activity

Volcanoes are divided according to the degree volcanic activity on active, sleeping, extinct and dormant. An active volcano is considered to be a volcano that erupted in a historical period of time or in the Holocene. The concept of active is rather inaccurate, since a volcano that has active fumaroles is classified by some scientists as active, and some as extinct. Dormant volcanoes are considered inactive, on which eruptions are possible, and extinct - on which they are unlikely.

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

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

Types of volcanic structures

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

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

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

There are monogenic and polygenic volcanoes. The first arose as a result of a single eruption, the second - multiple eruptions. Viscous, acidic, low-temperature magma, squeezing out of the vent, forms extrusive domes (Montagne-Pele's needle, 1902).

In addition to calderas, there are also large negative landforms associated with sagging under the influence of the weight of erupted volcanic material and a pressure deficit at depth that arose during the unloading of the magma chamber. Such structures are called volcano-tectonic depressions. Volcano-tectonic depressions are very widespread and often accompany the formation of thick strata of ignimbrites - acidic volcanic rocks of different genesis. They are lava or formed by baked or welded tuffs. They are characterized by lenticular segregations of volcanic glass, pumice, lava, called fiamme, and a tuff or tof-like structure of the groundmass. As a rule, large volumes of ignimbrites are associated with shallow magma chambers formed due to melting and replacement of host rocks. Negative landforms associated with volcanoes of the central type are represented by calderas - large rounded failures, several kilometers in diameter.

Classification of volcanoes by shape

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

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

Eruption

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

• Hawaiian type - ejections of liquid basalt lava, lava lakes often form, should resemble scorching clouds or hot avalanches.
• Hydroexplosive type - eruptions occurring in the shallow waters of the oceans and seas are distinguished by the formation a large number steam generated by the contact of red-hot magma and sea water.

Post-volcanic phenomena

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

During eruptions, sometimes a collapse of a volcanic structure occurs 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. When magma rises, the external pressure weakens, the gases and liquid products associated with it break out to the surface, and the volcano erupts. If the ancients are brought to the surface rocks, and not magma, and water vapor, formed during heating, predominates among the gases groundwater, then such an eruption is called phreatic.

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

Heat sources

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

Areas of volcanic activity

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

mud volcanoes

mud volcanoes- small volcanoes through which not magma comes to the surface, but liquid mud and gases from the earth's crust. Mud volcanoes are much smaller than ordinary volcanoes. The mud usually comes to the surface cold, but the gases erupted by mud volcanoes often contain methane and can ignite during the eruption, creating a picture similar to a miniature eruption of an ordinary volcano.

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

Volcanoes on other planets

Volcanoes in culture

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

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Translated from Latin "volcano" means "flame, fire". In the bowels of the planet, due to the very high temperature, rocks are melted with the formation of magma. In this case, a huge amount of gaseous substances is released, which increases the volume of the melt and its pressure on the surrounding solid rocks. Magma rushes to areas with less pressure upward towards the Earth's surface. Cracks in the earth's crust are filled with heated liquid rocks, layers of the earth's crust are torn and rise. Partially, magma solidifies in the earth's crust with the formation of igneous veins and laccoliths. The rest of the hot magma comes to the surface during volcanic eruptions, in the form of lava, volcanic ash, gases, hardened lava ingots, rock fragments. The term "volcanism" refers to the movement of molten magma from the deep layers of the Earth to the land surface or the ocean floor.

In the structure of each volcano, a channel is distinguished through which lava moves. This so-called vent usually ends in a crater - a funnel-shaped extension. The diameter of the craters varies from hundreds of meters to several kilometers. For example, the diameter of the Vesuvius crater is more than 0.5 km. Excessively large craters are called calderas. Thus, the caldera of the Uzon volcano, which is located in Kamchatka, has a diameter of 30 km.

Lava and eruptions

The height and shape of volcanoes is determined by the viscosity of the lava. If the lava is liquid and flows quickly, a cone-shaped mountain will not form, for example, the Kilauza volcano on Hawaiian Islands. The crater of this volcano looks like a rounded lake with a diameter of about 1 km. The crater is filled with hot liquid lava, and its level at times rises, then falls, sometimes splashing over the edge.

Most volcanoes are characterized by viscous lava, which, when cooled, forms a volcanic cone. The structure of such a cone is usually layered. On this basis, it can be judged that the eruptions were carried out repeatedly, due to which the volcano grew gradually with each ejection of lava.

The height of volcanic cones is different and can range from tens of meters to several kilometers. A very high volcano in the Andes - Aconcagua (6960 m) is widely known.

There are about 1,500 volcanoes all over the Earth, among them there are both active and extinct. For example, Klyuchevskaya Sopka in Kamchatka, Elbrus in the Caucasus, Kilimanjaro in Africa, Fujiyama in Japan, etc.

Overwhelming majority active volcanoes located along the perimeter of the Pacific Ocean. They make up the Pacific Ring of Fire. The Mediterranean-Indonesian belt is also considered a zone of active volcanism. For example, there are 28 active volcanoes in Kamchatka, and there are more than 600 in total. There is a certain regularity in the location of active volcanoes. They are localized in mobile areas of the earth's crust - in seismic belts.

In the ancient geological epochs of our planet, volcanism was more active than at present. In addition to typical (central) eruptions, fissure eruptions were also noted. From huge faults in the earth's crust, tens and hundreds of kilometers long, bubbling lava was thrown to the surface. In this case, the formation of lava covers, both continuous and discontinuous, took place. These covers leveled the terrain. The thickness of the lava layer could reach 2 km. Such processes led to the formation of lava plains. These include some sections of the Central Siberian Plateau, the Armenian Highlands, the Deccan Plateau in India, and the Columbia Plateau.

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There are volcanoes on land and under water, there are active and "sleeping" - extinct.
VOLCANOES
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individual 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 (several to hundreds of meters deep and up to 1.5 km in diameter). During eruptions, sometimes a collapse of a volcanic structure occurs 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. When magma rises, the external pressure weakens, the gases and liquid products associated with it break out to the surface and the volcano erupts. If ancient rocks, and not magma, are brought to the surface, and water vapor, formed during the heating of groundwater, predominates among the gases, then such an eruption is called phreatic.

ACTIVE VOLCANOES OF THE EARTH An active volcano is considered to have erupted in historical time. In total, approximately 2500 eruptions of 500 such volcanoes are known. The map shows some of the most famous volcanoes, as well as those mentioned in the text.

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

A SHIELD VOLCANO (left) with a large crater (caldera), and a thin layer of hardened lava on the surface. Lava outpourings can come from a summit crater or through cracks in slopes. Collapse craters are found inside the caldera, as well as on the slopes of the shield volcano. A STRATOVOLCANO CONE (right) consists of alternating layers of lava, ash, cinders, and larger debris. A cinder cone is shown on the slope of the volcano.
Active volcanoes include volcanoes that erupted in historical time or showed other signs of activity (emission of gases and steam, etc.). Some scientists consider active those volcanoes, which are reliably known to have erupted within the last 10 thousand years. For example, the Arenal volcano in Costa Rica should have been classified as active, since at archaeological excavations volcanic ash was discovered in the area, although for the first time in human memory, its eruption occurred in 1968, and before that there were no signs of activity. See also VOLCANISM.

Eruption of Mount Etna in Sicily, one of the most famous volcanoes peace. Since 1500, more than 100 of its eruptions have been recorded.

ARARAT - dormant volcano on the Armenian Highlands in Turkey, consisting of two cones merged at the bases - Greater and Lesser Ararat.

The most typical representation of a volcano is a mountain in the form of a cone with shimmering lava and poisonous gases erupting from a crater at the top. But this is only one of many types of volcano, and the characteristics of other volcanoes can be much more complex.

The structure and behavior of a volcano depends on many factors. Many volcano peaks are formed by lava cones rather than craters. Thus, volcanic materials (lava, or magma that has escaped from the depths, and ash) and gases (mainly steam and magma gases) can escape anywhere on the surface. .

Types of volcanoes

1. Vent crack

This is a view of a volcano with a flat fault at the top in the form of a line, through which lava erupts.

2. Shield Volcano

This type of volcano is named because of its wide shield-like profile, formed by the eruption of inviscid lava, which can spread over long distances from the fissure, but this does not generally lead to catastrophic consequences. Non-viscous lava does not contain much silicon oxide, so shield volcanoes are found mainly in the ocean and not on continents.

3. Cryptovolcanoes

Cryptovolcanoes form when viscous lava works its way up and causes a lava cone to form. The volcanic eruption on Saint Helena in 1980 was an example of a cryptovolcano. The lava was under tremendous pressure and formed a lava dome at the top of the mountain, which was unstable and therefore moved down the northern slope.

4. Cinder cone

Volcanic or cinder cones are formed as a result of the eruption of small pieces of cinder and pyroclasts (both formations look like small cylinders, which gave the name to the volcano), forming around the hydrothermal corridor. The eruption takes place for quite a short time and forms a cone-shaped hill 30-40 meters high. Most cinder cones erupt only once. They may form as end hydrothermal corridors on big volcanoes or form on their own. Paricutin in Mexico and Sunset Crater in Arizona are examples of cinder cones. In New Mexico, about 60 cinder cones were formed in the Caja del Río volcanic field.

5. Stratovolcanoes

Stratovolcanoes, or as they are also called composite volcanoes, are characterized as high conical structures consisting of layers of lava and other products of a volcanic eruption, the so-called layers - strata - which gave the name this species volcanoes. Stratovolcanoes are formed from slag, ash and lava. As a result of volcanic activity, slag and ash settle on the top of the mountain in layers (ash over slag), and lava flows down the ash layer, where it cools and hardens, then the process repeats. Typical examples of stratovolcanoes are Mount Fiji in Japan, Mawon Volcano in the Philippines, and Mount Vesuvius and Stromboli in Italy.

6. Lava dome

Lava domes are formed during the eruption of inviscid lava. Sometimes they form in the crater of a volcano that erupted some time ago, as on Mount Saint Helena, but they can also form independently of previous eruptions, as in the case of Lassen Peak. Like stratovolcanoes, they are accompanied by violent explosive eruptions, but their lava generally does not extend far from the hydrothermal corridor.

7. Supervolcanoes

A supervolcano is usually characterized by a caldera spread over a vast area, which can potentially pose a huge danger, sometimes even on a continental scale. Eruptions of such volcanoes can be the cause of severe global cooling, lasting several years in a row, as a result of huge masses of sulfur and ash entering the atmosphere. A supervolcano is the most dangerous type of volcano. Examples include the Yellowstone Caldera in national park Yellowstone and Valles Caldera in New Mexico, Lake Taupo in New Zealand, Lake Toba in Sumatra and Ngorongoro Crater in Tanzania, Krakatoa near Java and Sumatra. A difficult task for volcanologists is to determine the boundaries of the huge calderas of supervolcanoes, the territory of which has increased over the centuries. Huge regions volcanic origin are also characterized as supervolcanoes if they are covered by huge layers of erupted basaltic lava, but they are considered incapable of volcanic activity.

8 Underwater Volcanoes

It is well known that underwater volcanoes are located on the ocean floor. Some of them are active great depths, can be determined visually from the eruption of steam and rocks above sea level. However, many are at great depths, where huge masses of water prevent steam and gases from erupting to the surface. However, it is possible to determine the activity of such volcanoes using underwater vehicles and the discoloration of the water on the surface, which occurs due to the chemical processes of combining water with erupting gases.

Pumice can also be the product of an eruption. However, even major eruption does not disturb the surface of the ocean in any way due to the rapid cooling process of the products of the eruption in the water, in relation to the gases in the atmosphere, the water also reduces the rate of spread of volcanic materials. Submarine volcanoes often form columns above a hydrothermal corridor. Such columns can become so high that they can appear above the surface of the oceans and form new islands. Lava under water forms in the form of balls, which is typical characteristic underwater volcanoes. Hydrothermal corridors are often adjacent to such volcanoes and even support a separate ecosystem built on walls of molten minerals.

9. Mud volcanoes

Mud volcanoes are small volcanoes through which not magma comes to the surface, but liquid mud and gases from the earth's crust. Mud volcanoes are much smaller than ordinary volcanoes. The mud usually comes to the surface cold, but the gases erupted by mud volcanoes often contain methane and can ignite during the eruption, creating a picture similar to a miniature eruption of an ordinary volcano. The largest mud volcanic structure is 10 kilometers in diameter and about 700 meters high.

10. Subglacial volcanoes

Subglacial volcanoes form under ice caps. Erupted lava flows over large lava boulders and basaltic tuff that were formed from previous volcanic eruptions. During such eruptions, the ice caps melt and the lava at the top goes down, leveling the surface and forming a flat top. Such a volcano is also called flat-topped or thuy. Typical examples are the mountains of Iceland, as well as British Columbia. The flat tops of volcanoes were first explored there, in the area of ​​the Tuya River and the Tuya Range in northern British Columbia. Tuya Butte - the natural landscape was first explored by volcanologists and gave its name to this group of volcanoes. Also recently formed national park Tuya Mountains in the northern area of ​​Lake Tuya and south of the Jennings River near Yukon Territory to protect the rare landscape of Arena volcanoes. Currently, such volcanoes are not found, or one might say they do not exist.

11. Fissure Volcanoes

They are manifested in the outpouring of lava onto the earth's surface along large cracks or splits. In certain periods of time, mainly at the prehistoric stage, this type of volcanism reached a rather large scale, as a result of which a huge amount of volcanic material, lava, was brought to the surface of the Earth. Powerful fields are known in India on the Deccan Plateau, where they covered an area of ​​5.105 km2 with an average thickness of 1 to 3 km. Also known in the northwestern United States, in Siberia. At that time, basaltic rocks of fissure eruptions were depleted in silica (about 50%) and enriched in ferrous iron (8-12%). The lavas are mobile, liquid, and therefore can be traced for tens of kilometers from the place of their outpouring. The power of individual streams was 5-15m. In the United States, as well as in India, many kilometers of strata accumulated, this happened gradually, layer by layer, over many years. Such flat lava formations with a characteristic stepped topography are called plateau basalts or traps. Currently, fissure volcanism is widespread in Iceland (Laki volcano), Kamchatka (Tolbachinsky volcano), and on one of the islands of New Zealand. The largest lava eruption on the island of Iceland along the giant Laki fissure, 30 km long, occurred in 1783, when lava entered the day surface for two months.

The ancient Romans, watching black smoke and fire bursting from the top of the mountain into the sky, believed that they had an entrance to hell or to the possessions of Vulcan, the god of blacksmithing and fire. In honor of him, fire-breathing mountains are still called volcanoes.

In this article, we will figure out what the structure of the volcano is and look into its crater.

Active and extinct volcanoes

There are many volcanoes on Earth, both dormant and active. The eruption of each of them can last days, months, or even years (for example, located on the Hawaiian archipelago Kilauea volcano woke up back in 1983 and still his work does not stop). After that, the craters of volcanoes are able to freeze for several decades, in order to then again remind themselves of themselves with a new ejection.

Although, of course, there are also such geological formations, the work of which was completed in the distant past. At the same time, many of them have still retained the shape of a cone, but there is no information about exactly how their eruption took place. Such volcanoes are considered extinct. As an example, Kazbek can be cited, since ancient times covered with shining glaciers. And in the Crimea and Transbaikalia there are heavily eroded and destroyed volcanoes that have completely lost their original shape.

What are volcanoes

Depending on the structure, activity and location, in geomorphology (the so-called science that studies the described geological formations), separate types of volcanoes are distinguished.

In general, they are divided into two main groups: linear and central. Although, of course, such a division is very approximate, since most of them are attributed to linear tectonic faults in the earth's crust.

In addition, there is also a shield-like and domed structure of volcanoes, as well as the so-called cinder cones and stratovolcanoes. By activity, they are defined as active, dormant or extinct, and by location - as terrestrial, underwater and subglacial.

What is the difference between linear volcanoes and central volcanoes?

Linear (fissure) volcanoes, as a rule, do not rise high above the earth's surface - they look like cracks. The structure of volcanoes of this type includes long supply channels associated with deep cracks in the earth's crust, from which liquid magma, which has a basalt composition, flows out. It spreads in all directions and, while solidifying, forms lava covers that erase forests, fill depressions, and destroy rivers and villages.

In addition, during the explosion of a linear volcano, explosive ditches may appear on the earth's surface, having a length of several tens of kilometers. In addition, the structure of volcanoes along the fissures is decorated with gently sloping ridges, lava fields, splashes and flat wide cones that radically change the landscape. By the way, the main component of the relief of Iceland is the lava plateaus that arose in this way.

If the composition of the magma turns out to be more acidic (increased content of silicon dioxide), then extrusive (ie squeezed out) swells with a loose composition grow around the mouth of the volcano.

The structure of volcanoes of the central type

A volcano of the central type is a cone-shaped geological formation that crowns a crater on top - a depression shaped like a funnel or bowl. By the way, it gradually moves up as the volcanic structure itself grows, and its size can be completely different and measured both in meters and in kilometers.

Deep into the vent leads, along which magma rises up into the crater. Magma is a molten fiery mass that has a predominantly silicate composition. It is born in the earth's crust, where its hearth is located, and having risen upward, in the form of lava, it pours onto the surface of the earth.

An eruption is typically accompanied by the ejection of fine magma spurts that form ash and gases, which, interestingly, are 98% water. They are joined by various impurities in the form of flakes of volcanic ash and dust.

What determines the shape of volcanoes

The shape of a volcano largely depends on the composition and viscosity of the magma. Easily mobile basaltic magma forms shield (or shield-like) volcanoes. They are usually flat and have a large circumference. An example of such types of volcanoes is the geological formation located on the Hawaiian Islands and called Mauna Loa.

Cinder cones are the most common type of volcano. They are formed during the eruption of large fragments of porous slag, which, piling up, build a cone around the crater, and their small parts form sloping slopes. Such a volcano becomes higher with each eruption. An example is the Plosky Tolbachik volcano that exploded in December 2012 in Kamchatka.

Features of the structure of domed and stratovolcanoes

And the famous Etna, Mount Fuji and Vesuvius are examples of stratovolcanoes. They are also called layered, since they are formed by periodically erupting lava (viscous and quickly solidifying) and pyroclastic substance, which is a mixture of hot gas, hot stones and ash.

As a result of such ejections, these types of volcanoes have sharp cones with concave slopes, in which these deposits alternate. And the lava flows from them not only through the main crater, but also from cracks, while solidifying on the slopes and forming ribbed corridors that serve as a support for this geological formation.

Dome volcanoes are formed with the help of viscous granite magma, which does not flow down the slopes, but solidifies at the top, forming a dome, which, like a cork, clogs the vent and is knocked out by the gases accumulated under it over time. An example of such a phenomenon is the dome that forms over Mount St. Helens in the northwestern United States (it formed in 1980).

What is a caldera

described above central volcanoes are usually cone shaped. But sometimes, during an eruption, the walls of such a volcanic structure collapse, and calderas are formed - huge depressions that can reach a depth of thousands of meters and a diameter of up to 16 km.

From what was said earlier, you remember that the structure of volcanoes includes a huge vent, along which molten magma rises during an eruption. When all the magma is on top, a huge void appears inside the volcano. That's it, and the top and walls can fall into it. volcanic mountain, forming extensive cauldron-shaped depressions with a relatively flat bottom, bordered by the remains of the wreck, on the earth's surface.

The largest to date is the Toba caldera, located on (Indonesia) and completely covered with water. The lake formed in this way has a very impressive size: 100/30 km and a depth of 500 m.

What are fumaroles

The craters of volcanoes, their slopes, foot, as well as the crust of cooled lava flows are often covered with cracks or holes, from which hot gases dissolved in magma burst out. They are called fumaroles.

As a rule, thick white steam swirls over large holes, because magma, as already mentioned, contains a lot of water. But besides it, fumaroles also serve as a source of emissions for carbon dioxide, all kinds of sulfur oxides, hydrogen sulfide, hydrogen halide and other chemical compounds that can be very dangerous for humans.

By the way, volcanologists believe that the fumaroles that make up the structure of the volcano make it safer, since the gases find a way out and do not accumulate in the depths of the mountain to form a bubble that will eventually push the lava to the surface.

The famous volcano, which is located near Petropavlovsk-Kamchatsky, can be attributed to such a volcano. The smoke swirling above it is visible in clear weather for tens of kilometers.

Volcanic bombs are also part of the structure of the Earth's volcanoes

If a long-dormant volcano explodes, then during the eruption, so-called They fly out of its mouth. They consist of fused rocks or fragments of lava frozen in the air and can weigh several tons. Their shape depends on the composition of the lava.

For example, if the lava is liquid and does not have time to cool enough in the air, a volcanic bomb that has fallen to the ground turns into a cake. And basalt low-viscosity lavas rotate in the air, taking on this twisted shape or becoming like a spindle or a pear. Viscous - andesitic - pieces of lava become after falling like a bread crust (they are rounded or multifaceted and covered with a network of cracks).

The diameter of a volcanic bomb can reach seven meters, and these formations are found on the slopes of almost all volcanoes.

Types of volcanic eruptions

As Koronovsky N.V. pointed out in the book "Fundamentals of Geology", which considers the structure of volcanoes and types of eruptions, all types of volcanic structures are formed as a result of various eruptions. Among them, 6 types stand out in particular.

When did the most famous volcanic eruptions occur?

The years of volcanic eruptions can, perhaps, be attributed to serious milestones in the history of mankind, because at that time the weather changed, a huge number of people died, and even entire civilizations were erased from the Earth (for example, as a result of the eruption giant volcano perished Minoan civilization in the 15th or 16th century. BC e).

In 79 A.D. e. near Naples, Vesuvius erupted, burying the cities of Pompeii, Herculaneum, Stabia and Oplontius under a seven-meter layer of ash, leading to the death of thousands of inhabitants.

In 1669, several eruptions of the Etna volcano, as well as in 1766 - the Mayon volcano (Philippines) led to terrible destruction and death under lava flows of many thousands of people.

In 1783, the volcano Laki, which exploded in Iceland, caused a drop in temperature, which led in 1784 to crop failure and famine in Europe.

And on the island of Sumbawa, who woke up in 1815, the next year he left the whole Earth without summer, lowering the temperature in the world by 2.5 ° C.

In 1991, a volcano from the Philippines, with its explosion, also temporarily lowered it, however, already by 0.5 ° C.