Description of the volcano. What are the volcanoes

Developments

On Earth there are about 1500 volcanoes, which can be activated at any time. They are formed when molten rocks, called magma, rise to the surface of the earth, and break through its thin layers. Streams of magma can remain underground for hundreds of years, and then abruptly escape to the surface. Below you can find some interesting facts about volcanoes.

1. Volcanic Pumice   - this is the only volcanic stone that floats on the surface of the water. Usually it is gray in color, with hollow holes that form when hot gases leave the stone when it cools.

2. The largest volcanoes   called supervolcanoes. Their eruptions can lead to appalling consequences: a fiery rain thousands of miles from the very volcano, global climate change due to the ingress of ash into the atmosphere. Usually eruptions of such volcanoes occur several times in 100,000 years. One of them is located in the Yellowstone National Park, and scientists say that it may be ready for the next eruption.

3. The largest eruption   occurred on the Indonesian island of Sumbawa: it was the volcano of Tambor. During the eruption, 100,000 people died. It is believed that Indonesia has the largest number of historically active volcanoes - 76.

4. Most of the volcanoes   appear on the edges of tectonic plates, which form the surface of the earth. But some volcanoes, like Yellowstone, are located in other "hot spots", where magma breaks from the depths.

5. In Iceland, the land of fire and ice, is the largest number of volcanoes in the mid-Atlantic Atlantic ridge. The recent explosion of Eyyafyatlayokutl turns pale in comparison with the eruption of Scapthara, which destroyed the food supplies of the island, and caused the famine that caused the death of a fifth of the population.

6. The eruption of the Pinatubo volcano in the Philippines in 1991 led to more severe consequences.   He threw out 22 million tons of sulfur dioxide, which girded the entire planet, and led to a drop in temperature by 0.5 degrees.

7. Volcanoes can grow:   When lava and ashes are collected, they add meters to the surface of the volcano.

8. Volcanoes can be extinct:   they get such a name in the event that scientists are sure that there will be no more eruptions. Those volcanoes, whose activity subsided only for a while, are called sleepers.

9. Sometimes during volcanic eruptions the walls that contain the magma are destroyed,   and a giant crater called the caldera is formed.

10. The largest volcano on earth   - Hawaiian Mauna Loa. Being one of the five volcanoes of the island, it rises to 4000 meters above sea level.

11. Volcanic eruptions make sunsets more colorful:   appear orange and coral shades. This is due to the fact that small particles of ash scatter the sun's rays.

Some scientists refer to active, and some - to extinct. Sleepers are considered to be inactive volcanoes, on which eruptions are possible, and extinct - on which they are unlikely.

At the same time, among volcanologists there is no common opinion how to determine the active volcano. The period of activity of the volcano 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 to be active.

Astrophysicists, historically, believe that volcanic activity, caused in turn by the tidal effect of other celestial bodies, can contribute to the emergence of life. In particular, volcanoes contributed to the formation of the Earth's atmosphere and the hydrosphere, throwing out a significant amount of carbon dioxide and water vapor. Scientists also note that too active volcanism, such as on a satellite Jupiter And about  , can make the surface of the planet uninhabitable. At the same time, weak tectonic activity leads to the disappearance carbon dioxide and sterilization of the planet. "These two cases represent the potential boundaries of the habitation of the planets and exist along with the traditional parameters of life zones for systems of low-mass main sequence stars," write the scientists.

Types of volcanic buildings

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

Linear  volcanoes or fissure-type volcanoes, have long supply channels associated with a deep crust split. As a rule, basaltic liquid magma flows from such cracks, which spreads to the sides and forms large lava covers. Along the cracks appear gently sloping shafts, wide flat cones, lava fields. If magma  has a more acidic composition (higher content of silicon dioxide in the melt), linear extrusive rolls and arrays are formed. When explosive eruptions occur, then explosive ditches with a length of tens of kilometers can occur.

Forms of volcanoes of the central type depend on the composition and viscosity of the magma. Hot and easily mobile basaltic  magmas create vast and flat panel  volcanoes Mauna Loa  , Mauna Kea, Hawaii). If the volcano periodically erupts that lava, then pyroclastic material  , there is a cone-shaped layered structure, stratovolcano. The slopes of such a volcano are usually covered by deep radial ravines  - barrantries. Volcanoes of the central type can be purely lava, or formed only volcanic products - volcanic slags, tuffs  etc., formations, or be mixed-stratovolcanoes.

Distinguished monogenic  and polygenic  volcanoes. The first arose as a result of a single eruption, the second - multiple eruptions. Viscous, acidic in composition, low-temperature magma, squeezing out of the vents, forms extrusive dome (needle Montagne Pele  , 1902).

• During eruptions, a volcanic eruption sometimes collapses with formation caldera  - a large cavity with a diameter of up to 16 km and a depth of up to 1000 m. With the ascent magma external pressure is weakened, associated gases and liquid products break out onto the surface, and volcanic eruptions occur. If ancient rocks are borne on the surface, and not magma, and water vapor, formed when groundwater is heated, is such a eruption phreatic.

  The lava that ascends to the earth's surface does not always come out on this surface. It only raises the layers of sedimentary rocks and freezes in the form of a compact body ( laccolith), forming a peculiar system of low mountains. In Germany, such systems include regions Ryon  and Eifel  . On the latter, there is another post-volcanic phenomenon in the form of lakes filling the craters of former volcanoes, which failed to form a characteristic volcanic cone (the so-called maars).

  Heat sources

  One of the unresolved problems in the manifestation of volcanic activity is the determination of the heat source necessary for the local melting of the basaltic layer or mantle. Such melting should be narrowly localized, since the passage of seismic waves indicates that the crust and the upper mantle are usually in a solid state. Moreover, the thermal energy must be sufficient for the melting of huge volumes of solid material. For example, in USA  in the river basin Colombia  (states Washington  and Oregon) the volume of basalts is more than 820 thousand km³; the same large basalt thicknesses are found in Argentina ( Patagonia), India (Dean plateau) and South Africa  (the elevation of the Big Karoo). At present there are three hypotheses  . Some geologists believe that 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 one more point of view according to which the upper mantle is in a solid state under high pressure conditions, and when the pressure drops due to crack formation, a so-called phase transition occurs-solid rocks of the mantle melt and a liquid lava outflows to the Earth's surface through cracks.

  Volcanic activity areas

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

  Mud volcanoes

  Underwater volcanoes

  At the bottom of the World Ocean, by the 21st century, about 10,000 submarine volcanoes were identified, identified and mapped.

  Extraterrestrial volcanoes

  Volcanoes are not only available Earth  , but also on other planets and their satellites. The second highest mountain  The solar system is martian  volcano Olympus  , the height of 21.2 km.

  On some satellites of the planets ( Enceladus  and Triton) in conditions of low temperatures, the erupting "magma" consists not of molten rocks, but of water and light substances. This type of eruptions can not be attributed to ordinary volcanism, because this phenomenon was called cryovolcanism.

  • AT 1963  as a result of eruptions underwater volcano  south Iceland  there was an island Surtsey.
  • Eruption Krakatoa  at Indonesia  at 1883  caused the loudest roar ever heard in history; sound was heard at a distance of more than 4800 km from the volcano. Atmospheric shock waves traveled the Earth seven times and for 5 days still were noticeable. The volcano killed more than 36,000 people, demolished 165 villages and damaged 132 more tsunami  , which followed the eruption). The eruptions of the volcano after 1927  formed a new volcanic island  entitled Anak-Krakatau  ("The Child of Krakatau").
  • Volcano Kilauea  , located in Hawaiian  The archipelago is the most active volcano at the moment. The volcano rises only 1.2 km above sea level, however its last prolonged eruption began in 1983  and continues to this day. Lava flows flow into the ocean for 11-12 km.
  • AT Taipei (Taiwan) an active volcano was discovered. Previously, it was believed that the last activity of the volcano in this area was more than 200 thousand years ago, but it turned out that the last activity was only 5000 years ago [ ] .
  • In 2010 eruption of a volcano near the Eyjafjadlayöküld glacier  caused the cancellation of more than 60 thousand flights throughout the Europe.
  • Perhaps the largest flow of basaltic lava on Earth is the volcanogenic plateau in river valleys Hi-Gol and Jom-Bolok with access to the valley of the Oka River Sayanskaya in Eastern Siberia  in the mountains East Sayan  ; the length of the L-shaped narrow basaltic plateau formed in the postglacial period 10-12 thousand years ago as a result of a fractured outpouring of lava is about 75 km. On the plateau are the volcanoes Peretolchina , Kropotkin  and Old.

  Eruptions

  XXI Century

  • 2013 December 13 - the volcano Nameless , Russia
  • 2011 June 12 - the volcano Nabro  , the state Eritrea
  • 2011 June 5 - the volcano Pueue  , the state Chile
  • 2011 May 21 - the volcano Grimsvotn  , Island Iceland
  • 2011 January 3 - the volcano Etna  , East Coast Sicily
  • 2010 October 26 - the volcano Merapi , Indonesia  , Island Java
  • 2010, March 21 - a volcano near the glacier Eyyafyadlayekyudl  , Island Iceland

  XX century

  • 2000 December, Mexico  , volcano Popocatepetl
  • 2000 On March 14, Russia  , Kamchatka, volcano Nameless
  • 1997 June 30, Mexico  , volcano Popocatepetl
  • 1991 10-15 June, Philippines  , Island Luzon  , volcano Pinatubo
  • 1985 November 14-16, Colombia  , volcano Nevado del Ruiz
  • 1982 29 March, Mexico  , volcano El Chichon
  • 1980 May 18, the United States, washington state  , volcano St. Helens
  • 1956 March 30, the USSR, The Kamchatka Peninsula  , volcano Nameless
  • 1951 January 21, New Guinea  , volcano Lamington
  • 1944 June, Mexico  , volcano Parikutin
  • 1944 March, Italy  , volcano Vesuvius
  • 1931 December 13-28, Indonesia  , Island Java  , volcano Merapi
  • 1911 January 30 - Philippines  , volcano Taal
  • 1902, October 24 - Guatemala, the volcano Santa Maria
  • 1902, May 8 - the island Martinique  , volcano Montagne Pele

  The largest volcanoes on Earth

  Name of the volcano	Location:	Height, m	Region
  Ojos del Salado	Chilean Andes	6893	South America
  Liulliaillaco	Chilean Andes	6723	South America
  San Pedro	Central Andes	6159	South America
  Cotopaxi	Equatorial Andes	5911	South America
  Kilimanjaro	The Masai Plateau	5895	Africa
  Misty	Central Andes (south Peru)	5821	South America
  Orizaba	Mexican Highlands	5700
  Elbrus	North Caucasus	5642	Europe
  Popocatepetl	Mexican Highlands	5455	North and Central America
  Sangai	Equatorial Andes	5230	South America
  Nevado del Tolima	North-West Andes	5215	South America
  Klyuchevskaya Sopka	kamchatka Peninsula	4850	Asia

1. There are three main types of volcanoes. The first include volcanoes erupting magma, the second include erupting magma and ashes and to the third type are volcanoes erupting just ashes.
2. May be active, asleep or extinct.
3. Volcanoes can grow. Some volcanoes can grow slowly, some grow very quickly. For example, the volcano Parakutin began erupting on February 20, 1943. By the end of the year, he grew to 336 meters in height. The volcano fell asleep in 1952, by that time it had grown by 424 meters. By geological standards, this is a very rapid growth.
4. Now in the world there are 20 active volcanoes. Last year there were 70 active volcanoes. Over the past decade, there are 160 active volcanoes. According to scientists over the past 10,000 years, more than 6,000 volcanoes operated.
5. Volcanoes are dangerous. The Krakatoa volcano, which woke up in 1883, caused a tsunami that killed more than 36,000 people. Vesuvius volcano in 79 AD, buried the cities of Pompeii and Herculaneum, destroying 16,000 people. The volcano Pele on the island of Martinique destroyed the city with 30,000 people in 1902.
6. The highest volcano in the solar system, is on Mars. This is the volcano Olympus. It has a height of 27 km, and 550 km across.
7. The highest volcano on Earth is in Hawaii, it's the Mauna Kea volcano. Its height is 4207 meters.
8. The most remote point from the center of the Earth is the volcano Chimborazo in Ecuador. Peak Everest is not the most remote point from the center of the Earth. Since the earth has the shape of a ball, but slightly flattened from the poles, the points on the equator are farther from the center of the earth. The Chimborazo volcano is very close to the equator of the Earth.
9. The word magma comes from the Greek word for dough.
10. The mouth at the top of the volcano is called the caldera, from the Spanish word meaning "pot".
11. The ancient Hawaiians buried the dead in the lava of volcanoes.
12. The only continent on which there is no active volcano is Australia.
13. The word of the volcano originally comes from the name of the Roman god of fire Vulcan.
14. The object with the largest volcanic activity in our solar system is the satellite of Jupiter Io. Due to high volcanic activity, its surface is constantly changing
15. Birds called maleo use the warmth of lava to incubate chicks.
16. The most dangerous volcano to date, this volcano Popocatepetl, nicknamed El Popo, which is only 33 km from El Popo, is still active, it will generate thousands of tons of gas and ash in the atmosphere daily.
17. The eruption of the Krakatoa volcano in Indonesia is believed to have produced 200 megatons of energy, equivalent to an energy of 15,000 nuclear bombs.
18. From the lava of the Kilauea volcano, you can pave the road around the Earth 3 times.
19. In 1935, the US Air Force bombed the lava flow in the Hawaiian city of Hilo. The flow slowed and stopped, but no one could prove that the reason for this was the bombardment.
20. Volcanoes are usually located at the meeting place of tectonic plates.
21. In the Pacific Ring of Fire, more than 75% of the world's volcanoes are located.
22. Volcanoes are found on the ocean floor and even in polar ice.
23. Volcanic gases contain water vapor, carbon dioxide, sulfur dioxide, hydrogen chloride, hydrogen fluoride and hydrogen sulfide.
24. Volcanic eruptions rise in the air to a height of 30 km.
25. Over the last century, volcanic eruptions several times led to a drop in the average temperature on Earth. The fall of the temperature is about half a degree, due to the fact that the volcanic ash reflects the sun's rays.
26. Pumice is a unique volcanic rock that can float in water. It is used as an abrasive and is sometimes used in beauty salons to remove dry skin.
27. High-mountain volcanic areas have some of the most fertile soils in the world.
28. Surtsey Island, one of the youngest islands in the world, was formed in 1963 as a result of an underwater volcanic eruption. The area of ​​the island is 1 square kilometer. The island is named after Surth, a fiery giant from Icelandic mythology.
29. During the eruption of the volcano Pele in 1902 on the island of Martinique in the Caribbean Sea, more than 30,000 people died. Only two people from all over the island survived: a shoemaker living on the edge of the island, and a prisoner who was locked in a dungeon chamber with thick stone walls.
30. Beaches with black sand in Iceland and Hawaii are formed from black volcanic glass.
31. On earth, more than 300 million people (almost 1 in 20) live in the shadow of active volcanoes, including Vesuvius in Italy, Mount Rainer in the USA, and Popocatepetl in Mexico.
32. In some volcanic areas, such as, the thermal energy of magma is used to generate electricity. This kind of energy is called geothermal.
33. In Japan, there are 10% of all volcanoes in the world.
34. Iceland consists almost entirely of volcanic rocks.
35. In Japan, a bath of warm volcanic sand is used to treat many diseases.

Volcanoes esst on land and is under water, there are active and "sleeping" - extinct.
VOLCANOES
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separate elevations above the canals and cracks in the earth's crust, through which the products of the eruption are discharged from the deep magmatic foci. Volcanoes usually have the form of a cone with a vertex crater (depth from several to hundreds of meters and a diameter of up to 1.5 km). During eruptions, a volcanic structure collapses with the formation of a caldera, a large hollow with a diameter of up to 16 km and a depth of up to 1000 m. When the magma is raised, the external pressure weakens, the gases and liquid products that are associated with it break away and a volcanic eruption occurs. If ancient rocks are borne on the surface, and not magma, and water vapor, formed by heating groundwater, prevails among gases, then this eruption is called phreatic.

OPERATING VOLCANOES OF THE EARTH A volcano erupting in historical time is considered to be active. A total of about 2,500 eruptions of 500 such volcanoes are known. On the map are some of the most famous, as well as the volcanoes mentioned in the text.

MAIN TYPES OF VOLCANOES The extrusive (lava) dome (on the left) has a rounded shape and steep slopes cut by deep furrows. In the crater of the volcano, a cork of frozen lava can form, which prevents the release of gases, which subsequently leads to explosion and destruction of the dome. The steeply pyroclastic cone (right) is composed of alternating interbeds of ash and slags.

SHIELD VOLCANO (left) with a large crater (caldera), and a thin layer of frozen lava on the surface. Lava outflows can occur from the crater at the top or through cracks on the slopes. Inside the caldera, as well as on the slopes of the shield volcano, there are craters of collapse. CONTRAST STRATOVULKANA (right) consists of alternating layers of lava, ash, slag and larger debris. A slag cone is shown on the slope of the volcano.
The active ones include volcanoes erupting in historical times or exhibiting other signs of activity (ejection of gases and steam, etc.). Some scientists consider active those volcanoes, which are reliably known that they erupted within the last 10 thousand years. For example, the active should include the Arenal Volcano in Costa Rica, since volcanic ash was found in archaeological excavations of the primitive man's site in the area, although the eruption occurred for the first time in people's memory in 1968, and before that there was no sign of activity. See also VOLCANISM.

ETHNA VOLCANO Eruption in Sicily, one of the most famous volcanoes in the world. After 1500, more than 100 eruptions were recorded.

ARARAT is an extinct volcano on the Armenian plateau in Turkey, consisting of two cones merging with bases - the Greater and Lesser Ararat.

We will try to answer this question, remembering that the god of fire of the ancient Romans was called Vulcan (in Greek mythology - Hephaestus). He forged armor in his smithy, which, according to legend, was inside a mountain in one of the Aeolian Islands near Sicily (in southern Italy). This island is called Vulcano, and clouds of smoke are continuously bursting from the depression at the top of the mountain. According to the Romans, it was the forge of the fire god. Therefore, the most common definition of a volcano is this: a hill, a hill or a hill with a depression at the top - a crater from which magma comes to the surface.

The most common volcanoes are of central type. Magma rises along a pipe-shaped channel - a vent that ends at the top with a cup-shaped depression - a crater (from the "crater" to the "cup"). The volcano erupts, discarded debris, ashes, spewed lava remain on its slopes. The height of the mountain increases, and with it the crater moves higher and higher. Often, from the main vent to the side of the secondary vents branch off, and then on the slope of the cone there are side craters.

The most characteristic example of volcanoes of the central type is stratovolcanoes (from Latin stratum - "layer"). Their cones with slightly concave slopes, such as Mount Fujii in Japan or Klyuchevskaya Sopka in Kamchatka, are composed of alternating layers of lava and loose material - ash, volcanic bombs, tuffs, etc. If volcanoes are formed only by loose products ejected during explosions, they are called bulk ones. Lava volcanoes consist of lava streams repeatedly overlapping each other. Such volcanoes have the form of an irregular cone and are smaller in height than other volcanoes. However, there are giant lava volcanoes - for example, in the Hawaiian islands - reaching a height of more than 9 km from the level of the ocean floor, with craters up to 2 km in diameter. The fact is that above the surface of the ocean rises only the upper part of the volcanoes, and the big part is hidden under water. In the craters of such volcanoes basaltic magma splashes and from time to time it pours out there in the form of very liquid lava flows. If the lava shells form a huge shell or shield around the volcano, then such volcanoes are called shields - for example, Mauna Kea, Mauna Loa, Kilauea in Hawaii.

Another type of volcanoes is linear, or fractured. Their occurrence is associated with the rise, as a rule, of liquid basaltic magma along a fissure in the earth's crust. Lava flows from it both ways. Liquid lava flows on a huge area, forming lava covers. A vivid example of a fracture type eruption is the breakthrough of basaltic magma along the Lucky crack in Iceland in 1783. The outlaid lava covered an area of ​​about 600 km 2. Frozen, the lava blocked the crack, but next to it new cracks began to form, from which again the basalts erupted.

Sometimes magma, rising on the vent of the volcano, is not able to break through the already lying and already frozen volcanic rocks. But the growing pressure of the gases finally "kicks out the cork" from the vents, and a powerful explosion occurs. The apical part of the volcano collapses, and a depression with steep walls - a caldera (from caldera - "cauldron") is formed. In the future, an extrusive dome from a very viscous magma can grow in the caldera. This happened in 1956 on the volcano Bezymyannom on Kamchatka; so it was on Vesuvius after the eruption in 79 AD.

In the Aegean Sea, about 100 km north of the island of Crete, is a small island of Santorini (St. Irene Island), part of the Cycladic island arc. Santorini was destined to not only become a magnificent geological monument, but also to uncover many of the secrets of the ancient history of the Mediterranean.

The modern island of Santorini is a paradise for tourists who attack its beaches in the hot summer months, sailing on numerous ships and yachts and landing on small planes (the island's airfield is very small). The island of Santorini (its other name is Fera, or Tire) together with several other small islands form a ring, inside of which is a lagoon with a diameter of up to 10 km. Santorini, the largest of the islands, has a length of 11 km, others - a smaller one. The unique feature of this group of islands is that their outer slopes facing the open sea are relatively shallow, while the inland ones facing the lagoon are vertical cliffs with a height of more than 100 m. And in the center of a blue lagoon surrounded by islands above the water rise two small islands - Paleo-Kameni and Neo-Kameni, formed by heaps of blocks of black and dark red lava, which gives them a gloomy color of some pristine stone chaos.



  If it were possible to "pump out" all the water from the lagoon, our gaze would open up to a gigantic bowl-the caldera-with a depth of up to 500 m / s with a volcanic cone in the center. All this is very similar (only in much larger sizes) to a double volcano - a cone inside a destroyed cone, when a new, smaller volcano grows in a vast caldera, as was the case with Vesuvius. In the walls of the caldera, there are hollow layers of lavas, loose tuffs and ash of gray and black colors. Above, they are covered with a thick, up to 40 m thick, layer of white pumice, which stands out clearly against the dark background of the rest of the rocks. This pumice is a testament to the great catastrophe that occurred in the Aegean Sea around 1520 BC. and ruined the famous Minoan civilization.
Let us recall the great discoveries of the German merchant and archaeologist Heinrich Schliemann, who believed in the ancient Greek myths and excavated Troy and the "golden-haired" Mycenaeans - the city of the legendary Agamemnon. The honor of discovering another center of civilization of the time (middle of the 2nd millennium BC) belongs to the English archaeologist Arthur Evans, who in 1900 discovered the ruins of a large city with the famous Knossos palace on the northern coast of Crete. The culture discovered by Evans was called Minoan in honor of the legendary Minos, the ruler of Crete.

In the early 30's. XX century. the Greek archaeologist Spiridon Marinitos, excavating the port of Amniss in Crete, which belonged to Minos and served as the sea gate of the Cretan capital of Knossos, found pumice wreckage in one of the houses. They had to get here from somewhere far away, because there were no young (in the geological sense) volcanoes on Crete. And then Marinatos, studying the volcanoes of Santorini and other islands, thought: could not the most powerful explosion of the volcano, located 100 km north of Crete, cause the destruction of the port of Amniss and Knossos? With great enthusiasm, Marinatos began to explore this problem, and he was blessed with happiness - he discovered an ancient civilization with an unusually high level of development, buried under a multimetre layer of ash and pumice, the pumice that so effectively crowns the black walls of the Santorini caldera.

At the Santorini cape, Akrotiri Marinitos unearthed the city with two- and three-story houses, which perfectly preserved the amazing frescoes, now exhibited in a special hall of the archaeological museum of Athens. The catastrophe occurred, as mentioned above, around 1520. BC, and after it the inhabitants no longer returned to the city. At the same time, the destruction of the centers of Minoan culture in Crete also applies. Perhaps a grand explosion or several explosions on Santo-Rin, which destroyed the summit part of a large volcano, could be accompanied by earthquakes and the strongest waves in the sea (tsunami), as well as powerful ash and pumice. The eruption essentially led to the decline of the Minoan culture. On the ruins of Minoan cities, later completely different tribes built their homes.

It is possible that the traditions of the so-called Deucalion Flood are also associated with this catastrophe. It is possible that Atlantis, this mysterious disappeared continent, mentioned by Plato, should be sought in the Aegean Sea and correlated with the legend

About her death with the catastrophic eruption of Santorini in the middle of the XVI century. BC. This is how the geological events and ancient history closely intertwined.
  Large calderas, formed in historical and prehistoric times, are known in many parts of the world. In the cascading mountains of the west of the USA, in the state of Oregon, there is the picturesque Kreiter Lake, which filled a 10-kilometer caldera with a slag cone-island in the center. After the catastrophic explosion in 1883, the caldera of Krakatau volcano in the Sunda archipelago was formed. In Kamchatka, too, there are calderas, within which new lava cones have grown.

There are much smaller, flat-bottomed depressions formed as a result of single, mainly gas explosions; they are not associated with large volcanoes. Usually their diameter is hundreds of meters (rarely more); hollows have a rounded shape, are occupied by lakes and are called Maars - from the name of the Maar in Germany. Such maars are found in the west of Germany, in the Eifel region; in the Swabian Jura in the foothills of the Alps (southern Germany), as well as in France (the uplands of the Auvergne region).

Volcanoes are not only on land; they are in the oceans and seas. Especially spectacularly the sudden appearance of volcanoes from the "sea depths". So at the end of September 1957 a new small island named Fail in the Azores archipelago sprang up a new Kapeliush volcano, "grown up" in two weeks up to a height of 200 m; its diameter at the base was more than 1 km. Subsequently, this volcano was washed out by waves.

Volcanic explosions under water at shallow depths or shallow beneath the surface of the earth, where groundwaters are found, are greatly amplified due to the fact that water, in contact with hot magma, evaporates instantly and is emitted in the form of powerful steam jets. Eruptions of this type are called phreatic (from the Greek "frear" - "well").

An eruption of this type occurred on November 14, 1963 in the Atlantic Ocean south of Iceland. It began with the ejections of black tuff, ash and volcanic bombs that formed the island of Surtsey. The eruption power indicated that the explosions increased due to the contact of magma with water. But when the cone with the crater grew so much that the ocean waters penetrated into it, the character of the eruption changed, became more moderate. In the following months and years, until 1967, more and more submarine volcanoes appeared in the area, as if strung along a line of an invisible underwater crack. They turned into islands, which later collapsed under the influence of ocean waves and disappeared.

In Central Japan, the Bandai volcano is located. July 15, 1888, after a thousand years of silence, due to the warming of groundwater, magma warmed up powerful phreatic explosions, and a cloud of ashes and tuffs reached a height of 6 km. Subsequently, the ashes were covered with an area of ​​100 km 2. In the 90's. XIX century. on it formed a large caldera, along the edges of which later grew new volcanoes.

Volcanic deposits tell us about the nature of eruptions of distant eras. In many parts of the world, huge layers of so-called rhyolites have been discovered; Volcanic rocks with a silica content of 65 to 75%. Deposits of rhyolites hundreds of meters thick occupy areas of hundreds and thousands of square kilometers. Often they lie in the vast cavities formed over a partially empty magmatic focus and resemble calderas. These volcanic rocks during the eruption behave like liquid lava, flooding and smoothing the uneven terrain. They consist of debris; under the microscope they usually clearly see ash flyers, sharp-angled fragments of crystals and pumice, closely welded, as if welded together. According to all the laws of geology, such a volcanic rock must be very viscous and unable to spread out from the centers of eruptions; but in reality everything was different.

The history of studying such volcanic rocks, called ignimbrites (from the Latin ignis - "fire", imber - "downpour"), is very long and confusing. But only in the 60-ies. XX century, the idea was expressed that they are formed from ash flows, i.e. from the mass of volcanic ash, which does not rise in the explosion above the vent of the volcano, but as though poured out across the crater and like a liquid rushing down even along a gentle slope. Essentially, it should be a heavy scorching cloud of red-hot ash, saturated with gas, the release of which supports the particles of ash, as it were; on an air cushion. Such ash streams are able to travel tens of kilometers from the site of their eruption. After the end of the movement, the smallest fragments, under the influence of still high temperature and their own weight, begin to cake together, forming a dense volcanic rock.

Eruptions of real ash streams were not observed during the time of human civilization, therefore volcanologists can only guess how they happened.