According to a register of active volcanoes compiled by scientists from the University of North Carolina, it was found that out of 1,500 dangerous craters, 50 erupt and 11 are of special concern. Oddly enough, the Icelandic volcano Eyjafjallajokull, whose eruption paralyzed the sky over all of Europe for several days, is considered a “supporting character” in the world.
In just three days, it released 140 million cubic meters of gas and dust into the atmosphere. The column of smoke rose to a height of 10 km, in which the air is so electrified that incredible lightning can be observed every 15 minutes. 
In the list of the most dangerous volcanoes, scientists included the Philippine Pinatubo, which in 1991 released so much gas and ash into the atmosphere that changes were observed in the planet’s climate over the next two years. Also included here are the Italian volcanoes Stromboli and Etna. 
As the Italian newspaper La Repubblica reports, according to the European Space Agency, up to 500 million people live in the immediate vicinity of volcanoes. 90% of the 1,500 active volcanoes are concentrated in the 40,000-kilometer "ring of fire" in the Pacific Ocean. 
The publication recalled that a week ago the deepest volcanic eruption took place at a depth of 1,500 meters under water in the area of Fiji and Samoa. To observe the volcano, it was necessary to construct a camera that could withstand the melting temperature of lead. But the “coldest” vent is located above the ice shell in the Antarctic region. 
Eruptions usually begin with deep "breathing". The earth around the volcano seems to be retracted. Then the mountain begins to tremble, special sensors record the shaking of the soil. Then there is a dull sound that comes from the depths. 
However, the most dangerous volcanic eruption could happen very soon, scientists worry. The recently awakened Eyjafjallajökull is not so scary (his behavior already seems stable). However, the Katla volcano, located 20 km away, is of concern: it is five times larger and 100 times more powerful than Eyjafjallajokull, capable of erupting up to a billion cubic meters of lava per second. Data obtained from observation equipment indicate that the volcano will soon awaken. A rapid eruption is also indicated by a change in the direction of flow of local rivers.
“History indicates that it is very rare that Eyjafjallajökull comes to life without awakening the Katla volcano,” says a report from the Global Alliance for Disaster Reduction at the University of North Carolina. 
In the event of an eruption, scientists predict, we can expect a phenomenon called “volcanic winter”: a cloud of ash reflects the sun’s rays at a height, preventing them from reaching the surface of the earth.
Experts see the reason for such massive manifestations of volcanic force in the melting of ice, which probably weakened the pressure of the surface layers of the Earth, allowing magma to rise to the top.
"We expect more frequent and more powerful eruptions in Iceland in the coming years. Global warming is leading to melting of the ice. This phenomenon also affects the movement of magma under the surface of the Earth," explained geologist Freysteinn Sigmundsson. 
But the current eruption is not capable of affecting the Earth's climate, even if someone believes that the cloud released by the volcano could help lower the average temperature on the planet. Because the Icelandic volcano is much weaker than the Philippine one, which ranks 6th out of 8 possible. 
"We don't expect anything like this from Eyjafjallajokull. Its eruption level is too low to influence the climate," explained Olav Hija from the Norwegian Institute of Meteorology.
At the same time, it is possible that in the next 12-14 months Northern Europe will observe unusual sunsets of an intensely red color. 
In ancient times, volcanoes were the tools of the gods. These days they pose a serious danger to settlements and entire countries. Not a single weapon in the world has been given such power on our planet - to conquer and pacify a raging volcano.
Now means mass media, cinema and some writers fantasize about the future events 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 the state of 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, has attributed magical properties to the mountain, which is capable of spewing fire. The most famous novel that described an active volcano is “The Lord of the Rings” (where it was called “the lonely mountain”). The professor was right about this phenomenon.
No one can look at mountain ranges up to several hundred meters high without respecting the ability of our planet to create such magnificent and dangerous natural objects. These giants have a special charm that can be called magic.
So, if we discard the fantasies of writers and the folklore of our ancestors, then everything will become simpler. From the point of view of geographical definition: a volcano (vulkan) is a rupture in the crust of any planetary mass, in our case the Earth, due to which volcanic ash and gas accumulated under pressure along with magma escape from the magma chamber, which is located under the 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 subsequently appeared. Therefore, volcanism accompanies modern life.
How do they arise? On planet earth, the main cause of formation is the earth's crust. The fact is that above the earth’s core there is a 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 - natural protection from solar radiation.
However, the earth's surface itself, although solid, is not solid, but is divided into seventeen large tectonic plates. As they move, they converge and diverge; it is because of the movement that ruptures occur at the places where the plates touch, and this is how volcanoes arise. It is not at all necessary that this happens on continents; at the bottom of many oceans there are also similar gaps.
Structure of the volcano
A similar object forms on the surface as 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.
Schoolchildren see a drawing of such a representation high school on the pages of a geography textbook.
The structure of the “fire” mountain itself is simple and in cross-section looks like this:
- crater - tip;
- vent – a cavity inside a mountain through which magma rises;
- magma chamber - a pocket at the base.
Depending on the type and form of formation of the volcano, some structural element may be missing. This option is classic, and many volcanoes should be considered in this context.
Types of volcanoes
The classification is applicable in two directions: by type and form. Since the movement of lithospheric plates is different, the rate of cooling of magma varies.
Let's first look at the types:
- active;
- sleeping;
- extinct.
Volcanoes come in different forms:
The classification would not be complete if we did not take into account the relief forms of the volcano crater:
- caldera;
- volcanic plugs;
- lava plateau;
- tuff cones.
Eruption
An ancient force, like the planet itself, 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 residents of some cities. It is better not to get into a situation where a volcano is erupting.
On average, 50 to 60 eruptions occur on the planet in one year. At the time of writing, about 20 ruptures are flooding the surrounding area with lava.
The algorithm of actions may change, but this depends on the accompanying weather conditions.
In any case, the eruption occurs in four stages:
- Silence. Large eruptions show that it is generally quiet until the first explosion occurs. There is nothing to indicate the coming danger. A series of small tremors can only be measured by instruments.
- Lava ejection 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 Helens in May of the eighties of the last century. Lava, the temperature of which can reach one and a half thousand degrees during an eruption, killed all living things at a distance of six hundred kilometers.
- Lahar. If you are unlucky, it may rain at the eruption site, as happened in the Philippines. In such situations, a continuous stream is formed consisting of 20% water, the remaining 80% rock, ash and pumice.
- "Concrete". The conventional name is the hardening of magma and ash caught under a rain stream. A similar mixture destroyed more than one city.
The eruption is an extremely dangerous phenomenon; over half a century it has killed more than twenty scientists and several hundred civilians. Right now (at the time of writing) the Hawaiian Kilauea continues to destroy the island.
The largest volcano in the world
Mauna Loa is the most high volcano on the ground. 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 year 84 of the last century. However, in 2004 he showed the first signs of awakening.
If there is the largest one, then there is also the smallest one?
Yes, it is located in Mexico in the town of Pueblo and is called Coshcomate, 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. About four hundred of them are found in the Pacific Ocean's "Ring of Fire."
Eruption of the Guatemalan volcano Fuego
Perhaps someone will be interested list of active volcanoes:
- on the territory of Guatemala - Fuego;
- on the Hawaiian Islands - Kilauea;
- within the border of Iceland – Lakagigar;
- in the Canary Islands - La Palma;
- on the Hawaiian Islands - Loihi;
- on the Antarctic island - Erebus;
- Greek Nisyros;
- Italian volcano Etna;
- on Caribbean island Montserrat – Soufrière Hills;
- Italian mountain in the Tyrrhenian Sea - Stromboli;
- and the most famous 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, zero activity of a particular mountain does not guarantee safety. More than once, giants that had fallen asleep for many years suddenly showed signs of activation. This happened 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, you just have to imagine what a monstrous force lurks there, in the depths of the mountain. However, there is 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.
Most powerful explosion may result from the eruption of a mountain of colossal proportions. Volcanologists call this kind of “fire” mountains a supervolcano. On the activity scale, such formations should occupy a level of at least eight.
Volcano Taupo in New Zealand
There are four of these in total:
- Indonesian supervolcano of Sumatra-Toba island.
- Taupo is located in New Zealand.
- Serra Galan in the Andean mountains.
- 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 eruption of Pinatubo in 91 (20th century), which lasted more than a year and reduced the temperature of the earth 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 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. Currently active. Killed more than 100 people, over a thousand more remain at risk (2018);
- the deepest eruption to date occurred at a depth of 1200 meters - Mount West Mata, near the island of Fiji, Lau River basin;
- the temperature in a pyroclastic flow can be more than 500 degrees Celsius;
- The last supervolcano erupted on the planet about 74,000 years ago (Indonesia). Therefore, we can say that no person has ever experienced such a catastrophe;
- Klyuchevsky on the Kamchatka Peninsula is considered the largest active volcano in the Northern Hemisphere;
- ash and gases emitted 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 there on earth
There are not too many crustal ruptures in Russia. From a school geography course we know about Klyuchevsky volcano.
In addition to him, on the beautiful planet there are about six hundred active ones, as well as a thousand extinct and sleeping ones. It is difficult to determine the exact number, but their number does not exceed two thousand.
Conclusion
Humanity should respect nature and remember that it has more than one and a half thousand volcanoes in its arsenal. And let as few people as possible witness such a powerful phenomenon as an eruption.
Volcanic activity is a regular and stark reminder that the planet we live on has an ever-changing geology. Located along the edges of tectonic plates, the volcano erupts through fissures, releasing boiling magma, ash and gases from beneath the earth's surface to explode in response to changes in the alignment of the tectonic plates.
The catastrophic nature of erupting volcanoes in many ancient civilizations was attributed to the violent mood swings of the gods. We now have a more scientific understanding volcanic eruptions, but it can still be unpredictable and dangerous. We present to your attention the ten active and most dangerous volcanoes in the world.
10. Mauna Loa, Hawaii
This volcano in Hawaii has been active for 700,000 years. Fortunately, many of the eruptions are slow, but sometimes the lava flows become fast and pose a danger to nearby towns and villages. There is also the possibility of dangerous earthquakes.
9. Taal, Philippines
The volcano is located on the island of Luzon in the center of Taal Lake. Its proximity to Manila makes it a constant threat to its more than 1.6 million residents. Since 1572, the volcano has erupted 33 times. Visitors are encouraged to view the volcano from afar, although many tourists do not adhere to this recommendation.
8. Ulawun, Papua New Guinea
Ulavun Volcano is one of the most active on the planet. It has had 22 major eruptions recorded since the 1700s, and residents of nearby areas report regularly seeing minor eruptions. The structural integrity of Ulawun is questionable; if collapse occurs, the eruption could destroy hundreds of square kilometers of land.
7. Nyiragongo, Democratic Republic of Congo
This dramatic volcano has impressive lava lakes near its crater. These lakes come and go, sometimes with quite devastating consequences. In 1977, an eruption occurred in which lava had a speed of 97 km/h and destroyed nearby villages, killing and injuring thousands of people. 147 people died in the 2002 eruption, and another 120,000 lost their homes.
6. Merapi, Indonesia
Volcano Merapi is considered the most active in Indonesia, and it has produced a record amount of lava. Measuring flow only, Merapi stands out as the most active volcano on the planet. It has been active for at least 10 thousand years. A review of the 2010 eruption recorded 353 dead people, and more than 320 thousand people were left homeless.
5. Galeras, Colombia
This volcano is located near the border of Ecuador. It erupts frequently and has been active for an impressively long time. Scientists estimate that the volcano has been erupting for one million years or more. The first recorded eruption was in 1580, and between 1978 and 1988, Galeras was temporarily dormant. Once active again, it behaves menacingly, erupting almost every year since the start of the new millennium. The town of Pasto on the eastern slope of Galeras is home to 450 thousand inhabitants.
4. Sakurajima, Japan
In the list of active volcanoes, Sakurajima is known as the "Vesuvius of the East", referring to its high activity. It is separated from mainland Japan, but lava flows from the 1914 eruptions have effectively created a bridge of land connecting it to the rest of Japan. Sakurajima produces thousands of small eruptions every year. If a major eruption occurs, 700,000 residents in the city of Kagoshima will be in danger.
3. Popocatepetl, Mexico
Popocatepetl is located just 56 km from Mexico City and broke out recently, in 2000. Forty-one thousand people would have been in danger of losing their lives if they had not been evacuated in time. Nine million people live within the blast radius. If a major eruption ever occurs, it will be a disaster. Therefore, Popocatepetl is one of the most dangerous volcanoes on the planet, and the most active.
2. Vesuvius, Italy
Vesuvius is one of the most famous volcanoes in the world. Anyone who studied history at school knows about the famous catastrophic eruption in 79 AD. e., which destroyed the cities of Herculaneum and Pompeii. Volcanic ash has preserved the two sites, making them one of the most famous archaeological sites on earth. Vesuvius erupts cyclically, approximately every 20 years. The last recorded eruption dates back to 1944, so the next eruption is not far off. Three million people are not only within the blast radius, but also close to the crater. This is another volcano that poses a serious danger to an incredible number of people.
1. Yellowstone Volcano, USA
The number one active volcano on our list is the Yellowstone Caldera. Active volcanic caldera in National Park attracts about three million visitors a year. Its geysers and hot springs are beautiful, but they are also potentially deadly. Yellowstone is a supervolcano. Indeed, the famous major supervolcano eruption occurred at Yellowstone 640,000 years ago. If Yellowstone exploded, it is estimated that 87,000 people would be killed instantly. The entire western United States will be devastated, and the ash will impact the environment and health of people across the country and the world. The explosion would be a global catastrophe of unprecedented proportions, and there is no way to predict how far its effects will spread.
We no longer associate volcanic explosions with the whims of angry gods, but we believe that it is necessary to treat them with respect, at least we must, to protect the people who live within the radius of possible action. The amount of damage from volcanoes can be enormous. The best geologists have come to understand volcanoes and have determined that it is better to predict their explosions and protect large populated areas.
10 largest and most dangerous volcanoes on Earth.
A volcano is a geological formation that arose due to the movement of tectonic plates, their collision and the formation of faults. As a result of collisions between tectonic plates, faults form and magma comes to the surface of the Earth. As a rule, volcanoes are a mountain at the end of which there is a crater, which is where lava comes out.
Volcanoes are divided into:
- active;
- sleeping;
- extinct;
Active volcanoes are those that erupted in the near future (approximately 12,000 years)
Dormant volcanoes are volcanoes that have not erupted in the near future, but their eruption is practically possible.
Extinct volcanoes include those that have not erupted in the near historical future, but the top has the shape of a crater, but such volcanoes are unlikely to erupt.
List of the 10 most dangerous volcanoes on the planet:
1. (Hawaii Islands, USA)
Located in the islands of Hawaii, it is one of the five volcanoes that make up the islands of Hawaii. This is the most big volcano in the world in terms of volume. It contains more than 32 cubic kilometers of magma.
The volcano was formed about 700,000 years ago.
The volcano's last eruption occurred in March 1984, and it lasted for more than 24 days, causing enormous damage to people and the surrounding area.
2. Taal Volcano (Philippines)
The volcano is located on the island of Luzon, part of the Philippine Islands. The crater of the volcano rises 350 meters above the surface of Lake Taal and is located almost in the center of the lake.
The peculiarity of this volcano is that it is located in the crater of a very old extinct mega volcano, now this crater is filled with lake water.
In 1911, the most powerful eruption of this volcano occurred - then 1335 people died, within 10 minutes all life around the volcano died at a distance of 10 km.
The last eruption of this volcano was observed in 1965, which resulted in 200 casualties.
3. Volcano Merapi (Java Island)
The name of the volcano is literally Mountain of Fire. The volcano has been erupting systematically for the last 10,000 years. The volcano is located near the city of Yogyakarta, Indonesia, the city's population is several thousand people.
It was the most active volcano among the 130 volcanoes in Indonesia. The eruption of this volcano was believed to have led to the decline of the Hindu Kingdom of Matarama. The peculiarity and horror of this volcano is the speed of spread of magma, which is more than 150 km/hour. The volcano's last eruption occurred in 2006 and claimed 130 lives and made more than 300,000 people homeless.
4. Volcano Santa Maria (Guatemala)
This is one of the most active volcanoes of the 20th century.
It is located at a distance of 130 kilometers from the city of Guatemala, and is located in the so-called Pacific. Ring of Fire. The Santa Maria crater was formed after its eruption in 1902. About 6,000 people died then. The last eruption occurred in March 2011.
5. Ulawun Volcano (Papua - New Guinea)
The Ulawun volcano, located in the New Guinea region, began erupting at the beginning of the 18th century. Since then, eruptions have been recorded 22 times.
In 1980, the largest volcanic eruption occurred. The ejected ash covered an area of more than 20 square kilometers.
Now this volcano is the highest peak in the region.
The last volcanic eruption occurred in 2010.
6. Galeras Volcano (Colombia)
The Galeras Volcano is located near the border of Ecuador in Colombia. One of the most active volcanoes in Colombia, it has erupted systematically over the past 1000 years.
The first documented volcanic eruption occurred in 1580. This volcano is considered the most dangerous because of its sudden eruptions. Along the eastern slope of the volcano is the city of Paphos (Pasto). Paphos is home to 450,000 people.
In 1993, six seismologists and three tourists died during a volcanic eruption.
Since then, the volcano has erupted every year, claiming thousands of lives and making many people homeless. The last volcanic eruption occurred in January 2010.
7. Sakurajima Volcano (Japan)
Until 1914 this volcanic mountain was located on a separate island in close proximity to Kyushu. After the volcano erupted in 1914, a lava flow connected the mountain to the Ozumi Peninsula (Japan). The volcano was named Vesuvius of the East.
He serves as a threat to the 700,000 people of Kagoshima City.
Since 1955, eruptions have occurred every year.
The government even built a refugee camp for the people of Kagoshima so they could find shelter during the volcanic eruption.
The last eruption of the volcano occurred on August 18, 2013.
8. Nyiragongo (DR Congo)
It is one of the most active, active volcanoes in the African region. The volcano is located in the Democratic Republic of the Congo. The volcano has been monitored since 1882. Since the start of observations, 34 eruptions have been recorded.
A crater in the mountain serves as a holder for magma fluid. In 1977, a major eruption occurred, neighboring villages were burned by streams of hot lava. The average speed of the lava flow was 60 kilometers per hour. Hundreds of people died. The most recent eruption occurred in 2002, leaving 120,000 people homeless.
This volcano is a caldera, a formation of a pronounced round shape with a flat bottom.
The volcano is located in Yellow national park U.S.A.
This volcano has not erupted for 640,000 years.
The question arises: How can it be an active volcano?
There are claims that 640,000 years ago, this super volcano erupted.
This eruption changed the terrain and covered half of the United States in ash.
According to various estimates, the volcanic eruption cycle is 700,000 - 600,000 years. Scientists expect this volcano to erupt at any time.
This volcano could destroy life on Earth.
Volcanoes are geological formations on the surface of the Earth's crust or the crust of another planet where magma comes to the surface, forming lava, volcanic gases, rocks (volcanic bombs) and pyroclastic flows.
The word “volcano” comes from ancient Roman mythology and comes from the name of the ancient Roman god of fire, Vulcan.
The science that studies volcanoes is volcanology and geomorphology.
Volcanoes are classified by shape (shield, stratovolcanoes, cinder cones, domes), activity (active, dormant, extinct), location (terrestrial, underwater, subglacial), etc.
Volcanic activity
Volcanoes are divided depending on their degree volcanic activity active, sleeping, extinct and dormant. An active volcano is considered to be a volcano that erupted during a historical period of time or in the Holocene. The concept of active is quite inaccurate, since a volcano with active fumaroles is classified by some scientists as active, and by others as extinct. Dormant volcanoes are considered to be inactive volcanoes where eruptions are possible, and extinct volcanoes are considered to be those where they are unlikely.
However, there is no consensus among volcanologists on how to define an active volcano. The period of volcanic activity can last from several months to several million years. Many volcanoes exhibited volcanic activity tens of thousands of years ago, but are not considered active today.
Astrophysicists, from a historical perspective, believe that volcanic activity, caused, in turn, by the tidal influence of other celestial bodies, can contribute to the emergence of life. In particular, it was volcanoes that contributed to the formation of the earth's atmosphere and hydrosphere, releasing significant amounts of carbon dioxide and water vapor. Scientists also note that too active volcanism, such as on Jupiter's moon Io, can make the planet's surface uninhabitable. At the same time, weak tectonic activity leads to the disappearance of carbon dioxide and sterilization of the planet. “These two cases represent potential boundaries for planetary habitability and exist alongside the traditional parameters of habitable zones for systems of low-mass main sequence stars,” the scientists write.
Types of volcanic structures
In general, volcanoes are divided into linear and central, but this division is arbitrary, since most volcanoes are confined to linear tectonic faults (faults) in the earth’s crust.
Linear volcanoes or fissure-type volcanoes have extensive supply channels associated with a deep split in the crust. As a rule, basaltic liquid magma flows out of such cracks, which, spreading to the sides, forms large lava covers. Along the cracks, gentle spatter shafts, wide flat cones, and lava fields appear. If the magma has a more acidic composition (higher silicon dioxide content in the melt), linear extrusive ridges and massifs are formed. When explosive eruptions occur, explosive ditches can appear tens of kilometers long.
The shapes of central-type volcanoes depend on the composition and viscosity of the magma. Hot and easily mobile basaltic magmas create vast and flat shield volcanoes (Mauna Loa, Hawaiian Islands). If a volcano periodically erupts either lava or pyroclastic material, a cone-shaped layered structure, a stratovolcano, appears. The slopes of such a volcano are usually covered with deep radial ravines - barrancos. Volcanoes of the central type can be purely lava, or formed only by volcanic products - volcanic scoria, tuffs, etc. formations, or be mixed - stratovolcanoes.
There are monogenic and polygenic volcanoes. The former arose as a result of a single eruption, the latter as a result of multiple eruptions. Viscous, acidic in composition, low-temperature magma, squeezed out of the vent, forms extrusive domes (Montagne-Pelé needle, 1902).
In addition to calderas, there are also large negative forms of relief associated with subsidence under the influence of the weight of erupted volcanic material and a pressure deficit at depth that arose during the unloading of the magma chamber. Such structures are called volcanotectonic depressions. Volcanotectonic depressions are very widespread and often accompany the formation of thick strata of ignimbrites - volcanic rocks of acidic composition, having different genesis. They are lava or formed by sintered or welded tuffs. They are characterized by lens-shaped segregations of volcanic glass, pumice, lava, called fiamme, and a tuff or tofo-like structure of the main mass. As a rule, large volumes of ignimbrites are associated with shallow magma chambers formed due to the melting and replacement of host rocks. Negative relief forms associated with central-type volcanoes are represented by calderas - large rounded failures several kilometers in diameter.
Classification of volcanoes by shape
The shape of a volcano depends on the composition of the lava it erupts; Five types of volcanoes are usually considered:
- Shield volcanoes, or "shield volcanoes". Formed as a result of repeated ejections of liquid lava. This form is characteristic of volcanoes that erupt low-viscosity basaltic lava: it flows for a long time both from the central vent and from the side craters of the volcano. Lava spreads evenly over many kilometers; Gradually, a wide “shield” with gentle edges is formed from these layers. An example is the Mauna Loa volcano in Hawaii, where lava flows directly into the ocean; its height from its base on the ocean floor is approximately ten kilometers (while the underwater base of the volcano is 120 km long and 50 km wide).
- Cinder cones. When such volcanoes erupt, large fragments of porous slag are piled up around the crater in layers in the shape of a cone, and small fragments form sloping slopes at the foot; With each eruption the volcano gets higher. This is the most common type of volcano on land. They are no more than a few hundred meters in height. An example is the Plosky Tolbachik volcano in Kamchatka, which exploded in December 2012.
- Stratovolcanoes, or "layered volcanoes". Periodically erupt lava (viscous and thick, quickly solidifying) and pyroclastic matter - a mixture of hot gas, ash and hot stones; as a result, deposits on their cone (sharp, with concave slopes) alternate. Lava from such volcanoes also flows out of cracks, solidifying on the slopes in the form of ribbed corridors that serve as the support of the volcano. Examples - Etna, Vesuvius, Fuji.
- Dome volcanoes. They are formed when viscous granite magma, rising from the depths of the volcano, cannot flow down the slopes and hardens at the top, forming a dome. It clogs its mouth, like a cork, which over time is expelled by the gases accumulated under the dome. Such a dome is now forming over the crater of Mount St. Helens in the northwestern United States, formed during the 1980 eruption.
- Complex (mixed, composite) volcanoes.
Eruption
Volcanic eruptions are geological emergencies that can lead to natural disasters. The eruption process can last from several hours to many years. Among the various classifications, general types of eruptions are distinguished:
- Hawaiian type - emissions of liquid basaltic lava, often forming lava lakes, which should resemble scorching clouds or red-hot avalanches.
- Hydroexplosive type - eruptions that occur in shallow conditions of oceans and seas are characterized by the formation large quantity steam generated by the contact of hot magma and sea water.
Post-volcanic phenomena
After eruptions, when the activity of the volcano either stops forever, or it “dormants” for thousands of years, processes associated with the cooling of the magma chamber and called post-volcanic processes persist on the volcano itself and its surroundings. These include fumaroles, thermal baths, and geysers.
During eruptions, a volcanic structure sometimes collapses with the formation of a caldera - a large depression with a diameter of up to 16 km and a depth of up to 1000 m. As the magma rises, the external pressure weakens, associated gases and liquid products escape to the surface, and a volcanic eruption occurs. If ancient rocks, and not magma, are brought to the surface, and the gases are dominated by water vapor formed when groundwater is heated, then such an eruption is called phreatic. 
Lava that rises to the earth's surface does not always reach this surface. It only raises layers of sedimentary rocks and hardens in the form of a compact body (laccolith), forming a unique system of low mountains. In Germany, such systems include the Rhön and Eifel regions. In the latter, another post-volcanic phenomenon is observed in the form of lakes filling the craters of former volcanoes that failed to form a characteristic volcanic cone (the so-called maars).
Heat sources
One of the unresolved problems of volcanic activity is determining the heat source necessary for local melting of the basalt layer or mantle. Such melting must be highly localized, since the passage of seismic waves shows that the crust and upper mantle are usually in a solid state. Moreover, the thermal energy must be sufficient to melt huge volumes of solid material. For example, in the USA in the Columbia River basin (Washington and Oregon states) the volume of basalts is more than 820 thousand km³; the same large strata of basalts are found in Argentina (Patagonia), India (Deccan Plateau) and South Africa (Great Karoo Rise). Currently there are three hypotheses. Some geologists believe that the melting is caused by local high concentrations of radioactive elements, but such concentrations in nature seem unlikely; others suggest that tectonic disturbances in the form of shifts and faults are accompanied by the release of thermal energy. There is another point of view, according to which the upper mantle under conditions of high pressure is in a solid state, and when, due to fracturing, the pressure drops, it melts and liquid lava flows through the cracks.
Areas of volcanic activity
The main areas of volcanic activity are South America, Central America, Java, Melanesia, Japanese islands, Kurile Islands, Kamchatka, northwestern USA, Alaska, Hawaiian Islands, Aleutian Islands, Iceland, Atlantic Ocean.
Mud volcanoes
Mud volcanoes are small volcanoes through which it is not magma that comes to the surface, but liquid mud and gases from the earth's crust. Mud volcanoes are much smaller in size than ordinary ones. Mud typically comes to the surface cold, but the gases emitted by mud volcanoes often contain methane and can ignite during the eruption, creating what looks like a miniature volcano eruption.
In our country, mud volcanoes are most common on the Taman Peninsula; they are also found in Siberia, near the Caspian Sea and in Kamchatka. On the territory of other CIS countries, the most mud volcanoes are in Azerbaijan; they are found in Georgia and Crimea.
Volcanoes on other planets
Volcanoes in culture
- Painting by Karl Bryullov “The Last Day of Pompeii”;
- Movies "Volcano", "Dante's Peak" and a scene from the film "2012".
- The volcano near the Eyjafjallajökull glacier in Iceland during its eruption became the subject of a huge number of humorous programs, television news stories, reports and folk art discussing events in the world.
(Visited 2,665 times, 1 visits today)
