The volcano in the picture below is called a composite volcano because it consists of alternating layers of lava and ash. Over long periods of time they formed a cone with steep slopes.

1. The place under the earth's crust where magma collects is called a magma chamber or volcanic chamber.

2. Vent - the main channel in the middle of the volcano;

3. Dike - a channel filled with magma, going from the vent to the surface;

4. Layers of ash and lava;

5. A hole at the very top of a volcano, called a crater;

6. Dust, ashes and gases;

7. Pieces of lava, called volcanic bombs.

The majestic cone on the surface of the Earth is only the tip of the volcano. No matter how big the volcano seems, its surface part is very small compared to the underground part, where the magma comes from. The cone of the volcano is composed of the products of its eruption. At the top is a crater - a bowl-shaped depression, sometimes filled with water.

The volcano is fed through an opening called the main channel or vent. Gases come out through the vent, as well as rock fragments and melts that have risen from the depths, which gradually form a relief on the surface of the volcano. Tied to the vent whole system volcanic cracks, side channels and magma chambers located from one to tens of kilometers from the Earth's surface. The primary magma chamber is located at a depth of 60-100 km, and the secondary magma chamber, which directly feeds the volcano, is at a depth of 20-30 km. As magma moves toward the surface, significant changes occur in it.

There are small volcanoes, the cone of which rises from the surface of the Earth by several hundred meters. There are huge, reaching 3000-5000 m in height. The largest volcano on the planet Mauna Loa is located on the island of Hawaii. It rises to 4170 m above sea level, and its sole rests at a depth of 5000 m. As a result, its height is more than 9 km.

Causes of eruptions. Numerous chemical, physical, geological factors can be among the causes of volcanic eruptions. Therefore, eruptions are not always easy to predict.

If a bottle with a carbonated drink is shaken before opening, then the gas dissolved in the drink tends to escape when the bottle is opened, forming foam. Similarly, in the vent of a volcano, foaming magma is ejected by the gases released from it. Under pressure, it rises through cracks in the earth's crust and rushes into the mouth of the volcano to erupt from the crater. Having lost a significant amount of gas, magma pours out of the crater and already like lava flows along the slopes of the volcano.

Why do volcanic eruptions occur? The heat accumulated in the depths of the Earth heats up the substance of the earth's core. Its temperature is so high that this substance would have to melt, but under the pressure of the upper layers of the earth's crust, it is held in a solid state. In those places where the pressure of the upper layers weakens due to the movement of the earth's crust and the formation of cracks, the red-hot masses pass into a liquid state. A mass of molten rock (magma), saturated with gases, under strong pressure, melts the surrounding rocks, making its way up. It happens that the vent is already clogged with solidified lava like a plug, which creates conditions for pressure to increase until it is high enough to push out this plug. The penetration of surface water, as well as the physical and chemical processes occurring in the magma itself, also create the conditions under which a volcanic eruption can occur.

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The ancient Romans, watching how black smoke and fire burst 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, the Kilauea volcano located on the Hawaiian archipelago woke up back in 1983 and still does not stop its work). 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 kicked 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

The central volcanoes described above have, as a rule, the shape of a cone. 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. It is precisely in it that the top and walls of a volcanic mountain can fall, forming on the earth's surface vast cauldron-shaped depressions with a relatively flat bottom, bordered by the remnants of the crash.

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 of a giant volcano, 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.

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In ancient times, volcanoes were the tools of the gods. Today, they pose a serious danger to settlements and entire countries. Not a single armament of the world has been given such power on our planet - to conquer and pacify a raging volcano.

Now the media, cinema and some writers are fantasizing about the future of the famous park, the location of which is known to almost everyone who is interested in modern geography - we are talking about a national park in Wyoming. Undoubtedly, the most famous supervolcano in world history of the last two years is Yellowstone.

What is a volcano

For many decades, literature, especially in fantasy stories, attributed to grief that is capable of spewing flames magical properties. Most famous novel, which described an active volcano - "The Lord of the Rings" (there it was called "lonely mountain"). The professor was right about this phenomenon.

No one can look at mountain ranges up to several hundred meters high without respect for the abilities of our planet to create such magnificent and dangerous natural objects. There is a special charm in these giants, which can also be called magic.

So, if we discard the fantasies of writers and the folklore of ancestors, then everything will become easier. From the point of view of a geographical definition: a volcano (vulkan) is a break in the crust of any planetary mass, in our case the Earth, due to which volcanic ash and gas accumulated under pressure, together with magma, breaks out of the magma chamber, which is located under a solid surface. At this moment, an explosion occurs.

Causes

From the very first moments, the Earth was a volcanic field, on which trees, oceans, fields and rivers later appeared. Therefore, volcanism accompanies modern life.

How do they arise? On the Earth main reason education is the earth's crust. The fact is that above the earth's core is the liquid part of the planet (magma), which is always moving. It is thanks to this phenomenon that there is a magnetic field on the surface - a natural protection from solar radiation.

However, the earth's surface itself, although solid, is not solid, but is divided into seventeen large tectonic plates. When moving, they converge and diverge, it is because of the movement at the points of contact of the plates that breaks occur, and volcanoes arise. It is not at all necessary that this happens on the continents; there are similar gaps at the bottom of many oceans.

The structure of the volcano

A similar object forms on the surface as the lava cools. It is impossible to see what is hidden under many tons of rock. However, thanks to volcanologists and scientists, it is possible to imagine how it works.

A drawing of such a representation is seen by schoolchildren high school in the pages of a geographical textbook.

By itself, the device of the "fiery" mountain is simple and in the context it looks like this:

• crater - top;
• vent - a cavity inside a mountain, magma rises along it;
• the magma chamber is a pocket at the base.

Depending on the type and form of formation of the volcano, some element of the structure may be absent. This option is classical, and many volcanoes should be considered in this particular section.

Types of volcanoes

Classification is applicable in two directions: by type and form. Since the movement of lithospheric plates is different, the rate of cooling of magma also varies.

Let's look at the types first:

• operating;
• sleeping;
• extinct.

Volcanoes come in many forms:

The classification would not be complete if we do not take into account the relief forms of the crater of volcanoes:

• caldera;
• volcanic plugs;
• lava plateau;
• tuff cones.

Eruption

As ancient as the planet itself, a force that can rewrite the history of an entire country is an eruption. There are several factors that make such an event on earth the deadliest for the inhabitants of some cities. It is better not to get into a situation when a volcano erupts.

On average, 50 to 60 eruptions occur on the planet in one year. At the time of writing, about 20 ruptures are flooding the neighborhood with lava.

Perhaps the algorithm of actions is changing, but it depends on the accompanying weather conditions.

In any case, the eruption occurs in four stages:

1. Silence. Large eruptions show that, until the moment of the first explosion, it is usually quiet. Nothing indicates the coming danger. A series of small shocks can only be measured by instruments.
2. Ejection of lava and pyroclastite. A deadly mixture of gas and ash at a temperature of 100 degrees (reaches 800) Celsius is capable of destroying all life within a radius of hundreds of kilometers. An example is the eruption of Mount Helena in May of the eighties of the last century. Lava, the temperature of which can reach one and a half thousand degrees during the eruption, killed all life at a distance of six hundred kilometers.
3. Lahar. If you are not lucky, then it may rain at the site of the eruption, as it was in the Philippines. In such situations, a continuous stream is formed, 20% consisting of water, the remaining 80% - rock, ash and pumice.
4. "Concrete". The conditional name is the hardening of magma and ash that fell under the rain stream. Such a mixture destroyed more than one city.

The eruption is an extremely dangerous phenomenon, for half a century it has killed more than twenty scientists and several hundred civilians. Right now (as of this writing), the Hawaiian Kilauea continues to destroy the island.

The largest volcano in the world

Mauna Loa is the highest volcano on earth. It is located on the island of the same name (Hawaii) and rises 9 thousand meters from the ocean floor.

His last awakening took place in the 84th year of the last century. However, in 2004 he showed the first signs of awakening.

If there is the largest, then there is also the smallest?

Yes, it is located in Mexico in the town of Pueblo and is called Catscomate, its height is only 13 meters.

active volcanoes

If you open a world map, then with a sufficient level of knowledge, you can find about 600 active volcanoes. Approximately four hundred of them are found in the "ring of fire" of the Pacific Ocean.

Eruption of the Guatemalan volcano Fuego

Perhaps someone will be interested list of active volcanoes:

• in the territory of Guatemala - Fuego;
• in the Hawaiian Islands - Kilauea;
• within the borders of Iceland - Lakagigar;
• in the Canary Islands - La Palma;
• in the Hawaiian Islands - Loihi;
• on the Antarctic island - Erebus;
• Greek Nisyros;
• the Italian volcano Etna;
• on the Caribbean island of Montserrat - Soufrière Hills;
• Italian mountain in the Tyrrhenian Sea - Stromboli;
• and the most eminent Italian - Mount Vesuvius.

Extinct volcanoes of the world

Volcanologists sometimes cannot say for sure whether a natural object is extinct or dormant. In most cases, the zero activity of a particular mountain does not guarantee safety. More than once, the giants who had fallen asleep for many years suddenly showed signs of activation. This was the case with the volcano near the city of Manila, but there are many similar examples.

Mount Kilimanjaro

Below are just some of the extinct volcanoes known to our scientists:

• Kilimanjaro (Tanzania);
• Mt Warning (in Australia);
• Chaine des Puys (in France);
• Elbrus (Russia).

The most dangerous volcanoes in the world

The eruption of even a small volcano looks impressive, one has only to imagine what a monstrous force lurks there, in the depths of the mountain. However, there are clear data that volcanologists use.

Through long observations, a special classification of potentially dangerous volcanic mountains was created. The indicator determines the impact of the eruption on the surrounding areas.

The most powerful explosion can follow from the eruption of a mountain of colossal proportions. Volcanologists call this kind of "fiery" mountains a supervolcano. On the scale of activity, such formations should occupy a level not lower than the eighth.

Taupo volcano in New Zealand

There are four of them in total:

1. Indonesian supervolcano of Sumatra-Toba island.
2. Taupo is located in New Zealand.
3. Serra Galan in the Andes mountains.
4. Yellowstone in the North American park of the same name in Wyoming.

We have collected the most interesting facts:

• the largest (in terms of duration) is the Pinatubo eruption of 91 years (20th century), which lasted more than a year and lowered the earth's temperature by half a degree (Celsius);
• the mountain described above threw 5 km 3 of ash to a height of thirty-five kilometers;
• the largest explosion occurred in Alaska (1912), when the Novarupta volcano became more active, reaching a level of six points on the VEI scale;
• the most dangerous is Kilauea, which has been erupting for thirty years since 1983. Active on this moment. Killed more than 100 people, more than a thousand remain under threat (2018);
• the deepest eruption to date occurred at a depth of 1200 meters - Mount West Mata, near the island of Fiji, the basin of the Lau River;
• the temperature in the pyroclastic flow can be over 500 degrees Celsius;
• the last supervolcano erupted on the planet about 74,000 years ago (Indonesia). Therefore, it can be said that not a single person has yet experienced such a catastrophe;
• Klyuchevsky on the Kamchatka Peninsula is considered the largest active volcano in the Northern Hemisphere;
• ash and gases erupted by volcanoes can color sunsets;
• the volcano with the coldest lava (500 degrees) is called Ol Doinyo Langai and is located in Tanzania.

How many volcanoes are on earth

There are not too many breaks in the earth's crust in Russia. From the school geography course it is known about the Klyuchevskoy volcano.

In addition to him, there are about six hundred active ones on the beautiful planet, as well as a thousand extinct and sleeping ones. It is difficult to establish the exact number, but their number does not exceed two thousand.

Conclusion

Mankind should respect nature and remember that it is armed with more than one and a half thousand volcanoes. And let as much as possible less people will witness such a powerful phenomenon as an eruption.