Essentially, a volcano is a hole in the earth's crust. When a volcano erupts from the depths of the Earth, hot rocks erupt to the surface through this hole. Volcanoes that are often active are called active. Volcanoes that may become active in the future are called dormant. An extinct volcano is a volcano whose activity has ceased forever.
Where are the volcanoes?
There are approximately 840 active volcanoes in the world. Usually there are only 20-30 eruptions per year. Most volcanoes are located near the edges of the giant plates that together make up the outer layers of the Earth. An earthquake occurs every 30 seconds in the world, and only a few of them pose a real danger.
Structure of the volcano
For those who want to find out what the volcano is made of, we advise you to study the following images in detail and carefully:
What is the largest volcano in the world?
The largest volcano in the world is Mauna Loa in Hawaii in the USA, the dome of which is 120 km long and 50 km wide. Volcano Lo'ihi is an active volcano off the Hawaiian Islands. It goes under water for 900 m and will rise to the surface in the period from 10 thousand to 100 thousand years. You can see this volcano in the photo below:
What are high-speed waves called?
Speed waves are deep seismic waves traveling through the earth at speeds of thousands of km/h. They are much faster than sound.
What is the greatest lava?
In Iceland in 1783 there was a very strong fissure eruption. At the same time, the red-hot one spread over a distance of 65-70 km.When did people walk on the sea?
The Kat Mai volcano in Alaska, USA, erupted so much floating pumice in 1912 that people walked on the sea.
How many active volcanoes are there on earth?
There are currently approximately 1,300 active volcanoes on land. There are also many of them under water, but their number fluctuates, as some cease their activity, while others arise. Every dormant volcano can suddenly explode. Consequently, those volcanoes that have been active at least once over the past 10 thousand years are considered active.
What is a volcanic eruption? Volcanic eruptions are a series of cannon-like explosions. They continue at intervals of hours and minutes, and occur as a result of the accumulation of a large volume of gas under the lava. During such eruptions, parts of the crater fly off, the size of which can reach the size of a bus.
What is a Plinian eruption?
When the hot gas is saturated with gas and fills the volcano, its crater explodes, throwing it out at twice the speed. The eruption is so violent that the magma breaks up into tiny pieces, and within a few hours the ground may be covered in a layer of ash. The eruption in 79 had the same character. At the same time, the Roman writer Pliny could not escape, so this type of eruption is Plinian.What is the Stomboli eruption?
If the magma is liquid enough, a crust can form above the lava lake in the volcano's crater. At the same time, large gas bubbles float out and explode the shell, splashing out volcanic bombs from the floor of molten lava and lava debris. This type of eruption is Strombolian from the Italian volcanic island of Stromboli.What was the most powerful volcanic eruption?
The most powerful volcanic eruption occurred approximately 20 thousand years ago, when the Toba volcano raged on the island of Sumatra in Indonesia. A 100 km crater formed in its center, and the other part of the island was buried under a layer of volcanic rock more than 300 m thick.
Why did Pompeii perish?
Throughout human history, volcanoes have been dangerous for people living near them. In 79 AD, the Roman city of Pompeii was razed to the ground by the erupting volcano Vesuvius. Even today the strongest eruptions cause harm to people.
When did the legend of Atlantis originate?
Around 1645 BC. e. The Greek island of Santorini exploded. As a result, the Minoan civilization was destroyed. This fact served as the beginning of the legend about the missing continent of Atlantis.
Useful information about volcanoes, geysers, photos of volcanoes
The most dangerous and unpredictable objects on the earth's surface are volcanoes- geological formations that arise above cracks in the earth’s crust, through which hot magma erupts into the earth, burning all living things in its path, hot and fragments of rocks.
In this case, volcanoes are divided into active fallen asleep and extinguished. Erupted magma is called lava. At times it slowly pours out of cracks, and at other times the volcano erupts in an explosion of steam, ash, dust and volcanic ash. It is these processes that lead to consequences that do not benefit people. Man today has no means to resist a volcanic eruption other than escape.
What are pyroclastic flows? When a volcano's crater is exposed, it breaks up the rocks and creates enormous amounts of debris, ash and pumice - pyroclastic materials. During eruptions, they are the first to rise up the vent. After the hole expands, magma begins to pour out of it. In this case, the pyroclastic cloud becomes so thick that it cannot mix with the air to rise upward. Because of this, it flows out as hot pyroclastic flows that move at enormous speeds reaching 200 km/h. They can cover the territory with eruption products.
What types of volcanoes are there?
Where tectonic plates move apart, magma flows through the gaps, forming fissure volcanoes. Rapidly solidified thick lava forms mound volcanoes. During powerful volcanic eruptions, a caldera crater occurs. Water often flows into it, and then a lake is formed. The most specific are stratovolcanoes, which are composed alternately of layers of lava and ash.
Lava erupting from focal and fissure volcanoes is usually fluid. As it cools, it creates basaltic rocks such as basalt, gabbro and dolerite. In situ it becomes rocks such as andesite, trachyte and rhyolite.
Formations from volcanic eruptions
Basalt columns. A dense flow of lava, when hardened, can break into hexagonal basalt columns, reminiscent of those at the Great Dyke in Northern Ireland.
Pahoehoe lava. Sometimes rocks on the surface quickly harden, creating a thin crust over the still viscous and hot lava. If the crust is several centimeters thick, then it cools down to such an extent that you can walk on it. However, if the lava continues to flow, the crust begins to wrinkle. The Hawaiians nicknamed this lava “pahoehoe,” which means “wavy.”
Lava aa. If lava rapidly solidifies into a rough mass, it is called "aa". During underwater volcanic eruptions, such as at mid-ocean ridges, the water instantly cools and breaks the lava into small, smooth particles called “pillows.”
Focal volcanoes. Most volcanoes lie along crustal plate boundaries, as they sit above a single accumulation of magma flowing to the surface. Even when the plate moves, such a source continues to remain in place, burning and burning through it at various points, forming a chain of volcanoes.
What kind of lava can volcanoes have?
Volcanoes can erupt lava of two types: aa-lavu And wavy lava.
Aa-lava is thicker and petrifies sharp rocks - volcanic slag.
Wavy lava is lava that is more fluid and rich in gases. When hardened, it creates rocks with a smooth surface, and sometimes flows down to form long stalactites. The clouds of ash emitted are lava powder.
How geysers appear
Hot spots and geysers are formed by boiling magma. When it leaks, rainwater seeps underground and encounters hot magma. Due to the pressure, its temperature will increase, and then the magma will rise again. If, when rising up, hot water mixes with cold water, it flows to the surface in the form of hot water. If it encounters an obstacle on its way, it remains under pressure and then splashes out in a strong stream called a geyser.
Eruption force
volcanoes can explode more powerfully than an atomic bomb. As a rule, this happens if the magma thickens and becomes so viscous that it plugs the volcano's mouth. Inside it, the pressure gradually increases until the magma dislodges such a plug. The strength of the eruptions is measured by the amount of ash that was thrown into the air. As magma flows underground, it takes on a variety of forms thanks to rocks. Typically, flowing magma flows into cracks within rocks, a process called conformable intrusion. In this case, saucer-shaped rocks are formed, such as lopoliths, lens-shaped ones - phacolites, or flat ones - sills. Viscous magma can push rock hard enough to create cracks, a process called unconformity intrusion.
Eruption forecast. How realistic?
It is extremely difficult to predict the time when the volcano will wake up. Hawaii's eruptions are quite calm, frequent and relatively predictable, but most natural ones are difficult to predict. A tiltmeter is used as one of the means to determine an upcoming eruption. It is a device for determining the steepness of the slopes of a volcano. If it increases, the magma located in the center of the volcano swells and an eruption may occur. But it should be remembered that such changes are only shortly before the eruption, making this type of forecasting dangerous.
6.1.Types of volcanoes
Each active volcano has its own individual characteristics. Moreover, there are no two completely identical volcanoes, just as among the multimillion-dollar population of our planet there are no two completely identical people. However, volcanoes can be grouped into groups with similar features.
For example, there are three types of volcanoes:
Area volcanoes. Currently, such volcanoes do not occur, or one might say do not exist. Since these volcanoes are confined to the release of a large amount of lava onto the surface of a large area; that is, from here we see that they existed in the early stages of the development of the earth, when the earth’s crust was quite thin and in some areas it could be completely molten.
Fissure volcanoes . They manifest themselves in the outpouring of lava onto the earth's surface along large cracks or splits. At certain periods of time, mainly at the prehistoric stage, this type of volcanism reached quite a wide scale, as a result of which a huge amount of volcanic material - lava - was carried to the surface of the Earth. Powerful fields are known in India on the Deccan Plateau, where they covered an area of 5. 10 5 km 2 with an average thickness of 1 to 3 km. Also known in the northwestern United States and Siberia. At that time, basaltic rocks from fissure eruptions were depleted in silica (about 50%) and enriched in ferrous iron (8-12%). The lavas are mobile, liquid, and therefore could be traced tens of kilometers from the place of their outpouring.
The thickness of individual flows was 5-15 m. In the USA, as well as in India, many kilometers of strata accumulated; this happened gradually, layer by layer, over many years. Such flat lava formations with a characteristic stepped relief form are called plateau basalts or traps.
Currently, fissure volcanism is widespread in Iceland (Laki volcano), Kamchatka (Tolbachinsky volcano), and on one of the islands of New Zealand. The largest lava eruption on the island of Iceland along the giant Laki fissure, 30 km long, occurred in 1783, when lava reached the surface for two months. During this time, 12 km 3 of basaltic lava poured out, which flooded almost 915 km 2 of the adjacent lowland with a layer 170 m thick. A similar eruption was observed in 1886 on one of the islands of New Zealand. For two hours, 12 small craters with a diameter of several hundred meters were active over a distance of 30 km. The eruption was accompanied by explosions and the release of ash, which covered an area of 10 thousand km 2, near the crack the thickness of the cover reached 75 m. The explosive effect was intensified by the powerful release of vapors from the lake basins adjacent to the crack. Such explosions caused by the presence of water are called phreatic. After the eruption, a graben-shaped depression 5 km long and 1.5-3 km wide formed in place of the lakes.
Central type. This is the most common type of volcanic magmatism. It is accompanied by the formation of cone-shaped volcanic mountains; their height is controlled by hydrostatic forces. The point is that the height h , to which liquid lava with a density of p l , from the primary magma chamber, is due to the pressure on it of the solid lithosphere with a thickness H and density p s . This relationship can be expressed by the following equation:
ghp s = gHp l
Where, g - acceleration of gravity.
( h - H )/ H =( p s - p l )/ p s
Expression<h - H > and is the height of the volcanic mountain h ; attitude ( p s - p l )/ p s can be expressed as a certain density coefficient j , then h = jH . Since this equation connects the height of the volcano with the thickness of the lithosphere through a certain density coefficient, which is different for different regions, this means that the height of the volcano is different in different regions of the globe.
Summarizing data on the activity of central-type volcanoes, scientists proposed classifying volcanoes according to the nature of their activity (Fig. 1).
To the Hawaiian type eruptions include Mauna Loa, Kilauea on the Hawaiian Islands, some volcanoes in Iceland, Nyamlyagira and Niragongo in Africa. In many ways, Plosky Tolbachik in Kamchatka is close to the Hawaiian type. The activity of these volcanoes is characterized by a calm, explosion-free outpouring of flowing basaltic lava and the absence of powerful releases of gases and steam. When the crater overflows, the lava overflows and flows down the slopes, forming long streams. The slopes of this type of volcanoes are very gentle; their shape resembles a giant shield, which is why they are also called shield volcanoes.
According to the activity of the Stromboli volcano, strombolian type eruptions. The basaltic lava of these volcanoes is somewhat more viscous than that of Hawaiian ones, but is still quite mobile. Volcanic gases are released from it with explosions, forming swirling volcanic bombs. There is no or very little ash. Conical volcanoes with a truncated top consist of interlayered lavas and products of explosive activity, i.e. They are typical layered volcanoes (stratovolcanoes).
For Vulcan type eruptions, as exemplified by the Vulcano volcano on the Aeolian Islands, are characterized by viscous andesite-basaltic lava, which releases gases with difficulty. Often lava clogs the crater of a volcano. Gases accumulate under the volcanic plug and burst out with great force, throwing out bombs, lapilli and ash. Pieces of viscous lava cannot curl in the air, but when cooled they crack, taking on the appearance of a bread crust. During eruptions, lava is also released in the form of short streams. Solidified lava has a blocky surface.
Vesuvian type eruptions are close to the Vulcan one, but differ from it in very strong explosive activity. Volcanic eruptions of this type are caused by lava that is somewhat more acidic, with more silica, and therefore more viscous. Gases and vapors accumulating under the lava plug burst upward, throwing out large amounts of ash, lapilli and bombs. The characteristic shape of bombs is in the form of flat cakes and loaves with a cracked surface (twisted shapes are not formed due to the viscous state of the lava). Lava flows are short and usually irregular in shape. By type of structure, volcanoes belong to stratovolcanoes. The Vesuvian type includes Vesuvius and Etna in Italy, and many volcanoes of Kamchatka and the Kuril Islands.
Plinian type The eruption is a further development of the Vesuvian one. It is characterized by strong explosions of upward gas, which rises to a height of several kilometers, and then forms an expanding cloud, shaped like the crown of an Italian pine tree. Strong explosions lead to the destruction of the volcanic cone.
Features of volcanic eruptions Peleian type(from the name of the Mont Pele volcano) are due to the very high viscosity of the ejected lava, which, when solidified, firmly clogs the crater of the volcano. Gases at depth develop enormous pressure, and at the end there is a colossal explosion with the release of huge amounts of ash, bombs and gases. This highly heated gas cloud with a temperature of up to 700 0 C, filled with stone material, rapidly rolls down the slope of the volcano, bringing with it destruction and death. At the same time, the cloud grows upward into a huge curly column. Such highly heated clouds of ash and gas are called scorching clouds. Peleian-type volcanoes, in addition to Mont Pele, include Katmai in Alaska, Bezymianny in Kamchatka, and others.
Finally, eruptions are distinguished bandaisan type(Bandai-san is one of the large Japanese volcanoes), which is characterized by purely explosive activity, without lava coming out in the form of flows or domes to the surface. The crater of the volcano is closed with viscous lava, which does not allow gases and vapors to escape. Then, at a certain moment, a powerful explosion occurs, as a result of which the entire volcano collapses and a mass of frozen lava is thrown out. Fresh lava does not come to the surface. This includes Krakatoa in Indonesia, as well as some other volcanoes.
The types of activity considered include volcanoes of the central type, which reign supreme in the modern period of the Earth’s life. But in past geological eras, fissure-type eruptions were also widespread, which are characterized by the outpouring of lava from cracks gaping in the earth's crust. Currently, eruptions of this kind are occurring in Iceland, which is why fissure volcanoes are also called volcanoes Icelandic type.
One should not think that one and the same volcano operates in only one type. Volcanoes go through a certain path of development during their lives, so the nature of their activity also changes. The action of a certain type of volcano is essentially temporary, although it covers periods of time of many tens and even hundreds of thousands of years. Changes in the type of eruption are caused by changes in the composition of magma coming from the depths of the Earth, and the thermal regime. So, for example, Vesuvius in historical times erupted according to the Stromboli, Vulcano, Plinian type and threw out scorching clouds.
6.2.Structure of volcanoes(Fig. 2)
The roots of the volcano, i.e. its primary magma chamber is located at a depth of 60-100 km in the asthenospheric layer. In the earth's crust at a depth of 20-30 km there is a secondary magma chamber, which directly feeds the volcano through the crater. The volcanic cone is composed of products of its eruption. At the top there is a crater - a bowl-shaped depression that sometimes fills with water. The diameters of the craters can be different, for example, at Klyuchevskaya Sopka - 675 m, and at the famous volcano Vesuvius, which destroyed Pompeii - 568 m. After the eruption, the crater is destroyed and a depression with vertical walls is formed - a caldera. The diameter of some calderas reaches many kilometers, for example, the caldera of the Aniakchan volcano in Alaska is 10 km.
6.3.Eruption products
When a volcano erupts, products of volcanic activity are released, which can be liquid, gaseous and solid.
Gaseous, or volatile play an important role in volcanic activity. During the crystallization of magma at depth, the released gases raise the pressure to critical values and cause explosions, throwing clots of hot liquid lava to the surface. Also, during volcanic eruptions, powerful gas jets are released, creating huge mushroom clouds in the atmosphere. Such a gas cloud consisting of droplets of molten (over 700 0 C) ash and gases, formed from cracks of the Mont Pelee volcano, in 1902, destroyed the city of Saint-Pierre and 28,000 of its inhabitants.
The composition of gases and their concentration within a single volcano vary greatly from place to place and over time. They depend on temperature, and in the most general form on the degree of degassing of the mantle, and the type of earth’s crust. According to Japanese scientists, the dependence of the composition of volcanic gases on temperature is as follows:
Temperature, 0 C Composition of gases (without water)
1200-800 HCl, CO 2, H 2 O, H 2 S, SO
800-100 HCl, SO 2, H 2 S, CO 2, N 2, H 2
100-60 H 2 , CO 2 , N 2 , SO 2 , H 2 S
60 CO 2 , N 2 , H 2 S
The nature of the release of gases depends on the composition and viscosity of the magma, and the rate of separation of gases from the melt determines the type of eruption.
Liquid- characterized by temperatures in the range of 600-1200 0 C. It is represented by lava.
The viscosity of lava is determined by its composition and depends mainly on the content of silica or silicon dioxide. When its value is high (more than 65%), lava is called sour , they are relatively light, viscous, inactive, contain a large amount of gases, and cool slowly. A lower silica content (60-52%) is typical for average lava; They, like acidic ones, are more viscous, but they are usually heated more strongly (up to 1000-1200 0 C) compared to acidic ones (800-900 0 C). Basic lavas contain less than 52% silica and are therefore more liquid, mobile, and free-flowing. When they harden, a crust forms on the surface, under which further liquid movement occurs.
Solid products include volcanic bombs, lapilli, volcanic sand and ash. At the moment of the eruption, they fly out of the crater at a speed of 500-600 m/s.
Volcanic bombs- large pieces of hardened lava ranging in diameter from several centimeters to 1 m or more, and in mass reaching several tons (during the eruption of Vesuvius in 79, volcanic bombs ‘tears of Vesuvius’ reached tens of tons). They are formed during an explosive eruption, which occurs when the gases contained in it are quickly released from the magma. Volcanic bombs come in 2 categories: 1st, which arose from lava that was more viscous and less saturated with gases; they retain their correct shape even when hitting the ground due to the hardening crust formed when they cool. 2nd, formed from more liquid lava, during flight they acquire the most bizarre shapes, which become even more complex upon impact. Lapilli(lat. “lapillus” - small stone) - relatively small fragments of slag 1.5-3 cm in size, having various shapes. Volcanic sand- consists of relatively small lava particles ( 0.5 cm). Even smaller fragments, 1 mm or less in size, form volcanic ash, which, settling on the slopes of a volcano or at some distance from it, forms volcanic tuff. Powerful ash emissions, reducing solar radiation, cause a drop in temperature. Thus, the eruption of the El Chichon volcano in Mexico in 1982 led to a decrease in the average temperature on the globe by 2.5 0 C. A cooling also occurred after the eruption of Mount Pinatubo in 1991 in the Philippines.
6.4.Volcanoes in the service of humans(Fig.3)
The internal energy of the Earth, with which the activity of volcanoes is associated, is not yet subject to human control, and therefore we cannot yet get rid of this formidable phenomenon. But people find different means to reduce this danger. Moreover, man has learned to benefit from his “terrible neighbor.”
First of all, it should be noted that the volcanic forces of the Earth contain enormous energy. The heat consumption associated with eruptions and hot springs, according to scientists, is approximately 8.4 . 10 17 to 31.5 . 10 18 j in year.
The thermal energy of volcanoes has long been widely used in Iceland, a country of eternal ice that has no fuel reserves. It is also the cheapest energy available.
Hot volcanic water is widely used in Japan. It heats houses, warms the soil in rice fields and vegetable gardens, and due to its significant content of ammonium and phosphorus salts, it is used as a fertilizer.
Hot water is not only a source of heat and various chemical compounds. Many of them contain substances that have medicinal properties. For example, it has been established that the hot waters of many springs in Kamchatka and the Kuril Islands are not inferior in their balneological properties to the mineral waters of famous resorts. Thus, in Kamchatka, the waters of the Nalachevo springs, containing arsenic, gained great fame. Hot volcanic waters are used in the treatment of many diseases, including rheumatism, various diseases of the joints, nervous system, etc.
Modern volcanic activity is accompanied by the formation of a number of mineral deposits, some of which appear before human eyes. For example, gas jets released from the depths are so saturated with sulfur dioxide and hydrogen sulfide that sulfur mounds appear at their exit to the surface. Active volcanoes are also associated with the formation of ammonia, boric acid and other chemical compounds.
In ancient volcanoes, whose volcanic structures are more or less destroyed and under which there are no longer pockets of lava at depth, another complex of minerals is found. These are mainly metal ores, including mercury, silver, antimony, etc., sulfur deposits and, of course, lavas themselves as a building material. Underwater eruptions produce deposits of Iceland spar (a valuable material for the manufacture of optical instruments), and sometimes manganese and iron.
The formation of diamond is associated with a special type of magmatic activity at enormous depths (in its explosive nature, adjacent to volcanic phenomena).
Everything we have learned about volcanoes suggests that their activity can be used in a variety of ways. Moreover, in some cases these opportunities turn out to be completely unexpected. For example, Sahara researchers raised the question of using extinct volcanoes to...increase the amount of rainfall. At first glance, the proposal seems simply strange. However, there is a connection between rainfall and volcanic activity in the Sahara. The fact is that in the recent past, in the desert climate in the Sahara, volcanoes were active, and then there were many lakes in these parts. Therefore, it is assumed that the currently observed sharp decrease in humidity is associated with the cessation of volcanic eruptions. On the other hand, data on modern volcanic activity show that volcanic eruptions are usually accompanied by heavy precipitation. Hence the natural conclusion about the possibility of climate humidification by artificially renewing the activity of extinct volcanoes, for example, with the help of atomic energy.
6.5. Volcanic activity on the Moon
Relatively recently (with the beginning of space exploration) it became known that volcanism is a cosmic phenomenon, that it is inherent in all planets of the solar system. What we know most about is the volcanism of the Moon. There are 517 large and many smaller craters known on the visible side of the Moon.
On the night of November 3, 1958, Soviet astronomers N.A. Kozyrev and V.E. Ezersky recorded the eruption of volcanic gases from one of the lunar craters. Later, they discovered fumarole (“fumo” smoke) activity in another crater. This shows that volcanoes on the Moon continue to operate today.
7.Scientific methods and research tools
One of the methods of scientific research is photogrammetry. Photogrammetry is traditionally divided into two main areas: 1 – ground-based photogrammetry (phototopography); 2 – aerial photogrammetry (aerial phototopography, aerial photogeodesy) and involves the study of objects and phenomena using their photographic images obtained by specialized cameras (phototheodolites, aerial cameras, etc.) from points on the earth’s surface or using aircraft.
In recent decades, new photogrammetry methods have developed rapidly, based on the ability to visualize the results of remote sensing performed outside the visible range of the electromagnetic spectrum. Some of the new trends in remote sensing would be extremely useful for studying the volcanoes of Kamchatka and the Kuril Islands. For example, radar photogrammetry - because it is completely free from weather conditions, which, as is known, are the main obstacle to studying the volcanoes of Kamchatka and the Kuril Islands in the visible range. Photogrammetry of infrared (IR) images obtained using modern thermal imagers and thermal IR scanners could provide important additional materials in the study of volcanic eruptions and their precursors. But at the Institute of Volcanology, Far Eastern Branch of the Russian Academy of Sciences, it was the methods of traditional photogrammetry that received the greatest development and application, and only because the tools, instruments and technologies for research in this direction turned out to be the most accessible. Precise geometric characteristics and dynamic parameters of volcanic eruptions, determined by photogrammetry methods, make it possible to objectively judge the nature and scale of the events occurring and contribute to a correct understanding of the mechanism of eruptions.
And the complex of volcanological studies used on the R/V “Vulcanologist” when studying the underwater volcanoes of the Kuril island arc included echo sounding, hydromagnetic survey (HMS), sampling of bottom sediments, etc. as mandatory methods. In a number of cruises, heat flow measurements were carried out, continuous gas-hydrochemical profiling and hydrochemical studies.
When conducting geophysical research, a unified ship time service was used. It made it possible to synchronize the operation of various measuring equipment and bring the measurement results to common coordinates of time and space.
There are many other methods for studying volcanoes, but we will not go into details, because this is not the main topic of the work.
8. Connections with other problems and tasks
After the accumulation of extensive knowledge and the development of special methods for studying volcanoes, the independent science of volcanology arose. Volcanology is closely related to such sciences as geology, petrography, mineralogy, geochemistry, hydrogeology, geophysics, thermodynamics and partly astronomy.
In volcanology, precise calculations and experiments are increasingly being used, so before our eyes it is turning into an exact science. And if earlier collections of articles by volcanologists were to some extent, in the words of one non-volcanologist, “magazines illustrated with clouds of smoke,” now a large role in them is given to precise research based on data from physical chemistry, geophysics, and mathematical calculations , modeling of volcanic phenomena, etc.
Volcanology has developed a new direction, called “volcano-physics,” - the quantitative study of eruption phenomena, the study of deep parts of volcanic apparatuses using geophysical methods, and the establishment of connections between external volcanic phenomena and processes at great depths.
Volcanologists have adopted the achievements of modern technology. In the crater of the Avachinsky volcano, automatic sensors are installed that record the temperature of the volcano. Thanks to them, Kamchatka volcanologists can, without going up to the crater, constantly monitor how the volcano “feels”. Scuba gear is being replaced by underwater vessels and bathyscaphes, which make it possible to study manifestations of underwater volcanism for a long time and at great depths.
9. The place of this topic in the curricula and topics of the GHF
This topic is studied a little in the first year of the GHF. They also teach a course in paleovolcanology for undergraduates (Litasov Yu.D., 36 hours). Paleovolcanology - branch of geology that studies volcanic activity of past geological eras. The main subject of paleovolcanology is ancient volcanic structures (calderas, remains of volcanic shields, etc.) and their roots (through which magma rose to the earth's surface), going deep into the Earth and, unlike modern volcanoes, accessible for direct study on erosion sections of ancient folded structures.
10.Conclusion
No matter how implausible it may sound, I enjoyed writing this course work.
I don’t even know if I managed to summarize the knowledge I received and whether I “told” everything that was intended under this topic. I hope so. But I definitely achieved my goal, I learned a lot about volcanoes that I didn’t even know about. For example, everyone knows that there are craters on the Moon, but I didn’t know that they also erupt. That volcanic activity can be influenced by cosmic forces. And much more.
The difficulties in completing the work were the lack of time (if there was more time, it would be possible to better formulate my thoughts and ideas) and the fact that in the NSU library books on this topic were presented in one or two copies and had already been sorted out before me , so most of the books were taken to the JIGGM SB RAS.
11.References
3) Gushchenko I.I. Volcanic eruptions around the world. –M.: Nauka, 1979. (302 pages)
4) Lebedinsky V.I. Volcanoes are a formidable natural phenomenon. –M.: Academy of Sciences of the Ukrainian SSR, 1963. (108 pp.)
5) Lebedinsky V.I. Volcanoes and man. – M.: Nedra, 1967. (204 pages)
(from Latin fluidus - fluid) -..1) liquid and gaseous, easily mobile components of magma or gas-saturated solutions circulating in the depths of the earth. It is assumed that the fluid composition is dominated by superheated water vapor, fluorine, chlorine, carbon dioxide and many other substances are present... Abstract >> Geography
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Abstract >> BiologyThe earth's crust. Linear volcanoes or volcanoes cracked type, have extended... and liquid products break to the surface and happens eruption volcano. If on... -stratigraphic conditions. Peculiarities buildings structures determine the variety of relief...
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The ancient Romans, watching black smoke and fire bursting into the sky from the top of the mountain, believed that before them was the entrance to hell or to the domain 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 in the Hawaiian archipelago, awoke back in 1983 and its activity still does not stop). After which the craters of volcanoes are able to freeze for several decades, only to then remind of themselves again with a new eruption.
Although, of course, there are also geological formations whose work was completed in the distant past. Many of them still retain the shape of a cone, but there is no information about exactly how their eruption occurred. Such volcanoes are considered extinct. As an example, Kazbek can be cited, since ancient times covered with shining glaciers. And in Crimea and Transbaikalia there are heavily eroded and destroyed volcanoes that have completely lost their original shape.
What types of volcanoes are there?
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, this division is very approximate, since most of them are classified as linear tectonic faults in the earth’s crust.
In addition, there are also shield-shaped and dome structures of volcanoes, as well as so-called cinder cones and stratovolcanoes. By activity they are defined as active, dormant or extinct, and by location - as terrestrial, underwater and subglacial.
How do linear volcanoes differ from central ones?
Linear (fissure) volcanoes, as a rule, do not rise high above the surface of the earth - they have the appearance of cracks. The structure of volcanoes of this type includes long supply channels associated with deep splits in the earth's crust, from which liquid magma of basaltic composition flows. It spreads in all directions and, when solidified, 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, extending several tens of kilometers. In addition, the structure of the volcanoes along the fissures is decorated with gentle shafts, lava fields, spatter and flat wide cones, radically changing the landscape. By the way, the main component of Iceland's relief is lava plateaus, which arose in this way.
If the composition of the magma turns out to be more acidic (increased content of silicon dioxide), then extrusive (i.e. squeezed out) shafts with a loose composition grow around the mouth of the volcano.
The structure of central type volcanoes
A central type volcano is a cone-shaped geological formation, which is crowned on top by a crater - a depression shaped like a funnel or bowl. It, by the way, gradually moves upward as the volcanic structure itself grows, and its size can be completely different and measured in both meters and kilometers.
A vent leads deep into the crater, through 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 to the top, it pours out onto the surface of the earth in the form of lava.
An eruption is usually accompanied by the release of small sprays of magma, which 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 tend to be flat in shape and have a large circumference. An example of these types of volcanoes is the geological formation located in 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 grows higher with each eruption. An example is the Plosky Tolbachik volcano that exploded in December 2012 in Kamchatka.
Structural features of dome and stratovolcanoes
And the famous Etna, 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 matter, which is a mixture of hot gas, hot stones and ash.
As a result of such emissions, these types of volcanoes have sharp cones with concave slopes, in which these deposits alternate. And lava flows from them not only through the main crater, but also from cracks, solidifying on the slopes and forming ribbed corridors that serve as 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, plugs the vent and is expelled by 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 are usually cone-shaped. But sometimes, during an eruption, the walls of such a volcanic structure collapse, and calderas are formed - huge depressions that can reach a depth of thousands of meters and a diameter of up to 16 km.
From what was said earlier, you remember that the structure of volcanoes includes a huge vent through which molten magma rises during an eruption. When all the magma is on top, a huge void appears inside the volcano. It is precisely into this 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 remains of the crash.
The largest caldera today is the Toba caldera, located in (Indonesia) and completely covered with water. The lake formed in this way has very impressive dimensions: 100/30 km and a depth of 500 m.
What are fumaroles?
Volcanic craters, their slopes, foothills, and the crust of cooled lava flows are often covered with cracks or holes from which hot gases dissolved in the magma escape. They are called fumaroles.
As a rule, thick white steam billows over large holes because magma, as already mentioned, contains a lot of water. But besides this, fumaroles also serve as a source of release of carbon dioxide, all kinds of sulfur oxides, hydrogen sulfide, hydrogen halides and other chemical compounds that can be very dangerous for humans.
By the way, volcanologists believe that the fumaroles included in the structure of the volcano make it safer, since 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.
Such a volcano includes the famous one, which is located near Petropavlovsk-Kamchatsky. The smoke billowing above it can be seen tens of kilometers away in clear weather.
Volcanic bombs are also part of the structure of Earth's volcanoes
If a long-dormant volcano explodes, then during the eruption the so-called volcanoes fly out of its crater. 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 lava is liquid and does not have time to cool sufficiently in the air, a volcanic bomb that falls to the ground turns into a cake. And low-viscosity basaltic lavas rotate in the air, thereby taking on a twisted shape or becoming like a spindle or pear. Viscous - andesitic - pieces of lava after falling become like a bread crust (they are round 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 N.V. Koronovsky pointed out in the book “Fundamentals of Geology,” which examines 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 considered serious milestones in the history of mankind, because at this 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, the Minoan civilization died in 15 or 16 century BC).
In 79 AD e. Vesuvius erupted near Naples, burying the cities of Pompeii, Herculaneum, Stabia and Oplontium under a seven-meter layer of ash, leading to the death of thousands of inhabitants.
In 1669, several eruptions of Mount Etna, as well as in 1766, of Mayon Volcano (Philippines) led to terrible destruction and the death of many thousands of people under lava flows.
In 1783, the Laki volcano exploded in Iceland, causing a drop in temperature that led to crop failure and famine in Europe in 1784.
And on the island of Sumbawa, who woke up in 1815, the next year left the entire Earth without a summer, lowering the world temperature by 2.5 °C.
In 1991, a volcano in the Philippines also temporarily lowered it with its explosion, albeit by 0.5 °C.
Since ancient times, people have seen black clouds, fire, and fiery stones sometimes bursting out of it.
The ancient Romans believed that this island was the gateway to hell, and that Vulcan, the god of fire and blacksmithing, lived here. By the name of this god, these began to be called volcanoes.
A volcanic eruption can last for several days or even months. After a strong eruption, the volcano returns to a state of rest for several years and even decades. Such volcanoes are called valid.
There are volcanoes that erupted in times long past. Some of them have retained the shape of a beautiful cone. People have no information about their activities. They are called extinct, as, for example, in the Caucasus, Elbrus and Kazbek, the peaks of which are covered with sparkling, dazzling white. In ancient volcanic areas, deeply destroyed and eroded volcanoes are found. In our country such regions are Crimea, Transbaikalia and other places.
Volcanoes are usually cone-shaped with slopes that are gentler at their bases and steeper at their summits.
If you climb to the top of an active volcano during its calm state, you can see a crater - a deep depression with steep walls, similar to a giant bowl. The bottom of the crater is covered with fragments of large and small stones, and jets of gas and steam rise from cracks in the bottom and walls of the crater. Sometimes they calmly emerge from under stones and from cracks, sometimes they burst out violently, with hissing and whistling. The crater is filled with suffocating; rising up, they form a cloud at the top of the volcano. The volcano can quietly smoke for months and years until an eruption occurs. This event is often preceded by ; An underground rumble is heard, the release of vapors and gases intensifies, clouds thicken over the top of the volcano.
Then, under the pressure of gases escaping from the bowels of the earth, the bottom of the crater explodes. Thick black clouds of gases and water vapor mixed with ash are thrown out thousands of meters, plunging the surrounding area into darkness. With an explosion and roar, pieces of red-hot stones fly from the crater, forming giant sheaves of sparks. Ash falls from black, thick clouds onto the ground, and sometimes torrential rains fall, forming streams of mud that roll down the slopes and flood the surrounding area. The flash of lightning continuously cuts through the darkness. The volcano rumbles and trembles, molten fiery liquid lava rises through its mouth. It seethes, overflows over the edge of the crater and rushes in a fiery stream along the slopes of the volcano, burning and destroying everything in its path.
During some volcanic eruptions, lava does not flow. Volcanic eruptions also occur at the bottom of seas and oceans. Sailors learn about this when they suddenly see a column of steam above the water or “stone foam” floating on the surface - pumice. Sometimes ships encounter unexpectedly appeared shoals formed by new volcanoes at the bottom. Over time, these shoals - igneous masses - are eroded by sea waves and disappear without a trace.
Some underwater volcanoes form cones that protrude above the surface of the water in the form of islands.
For a very long time people could not explain the causes of volcanic eruptions. This natural phenomenon terrified people. However, the ancient Greeks and Romans, and later the Arabs, concluded that in the bowels of the Earth there is a large sea of underground fire. The disturbances of this sea cause volcanic eruptions on the surface of the Earth.
At the end of the last century, a special science separated from geology - volcanology. Now volcanological stations are being organized near some active volcanoes - observatory, where scientists conduct constant observations of volcanoes. We have such a volcanological station set up in Kamchatka in the village of Klyuchi. When one of the volcanoes begins to act, volcanologists immediately go to the volcano and observe the eruption.
By studying volcanic lava, you can understand how molten material turned into solid rock.
Volcanologists also study extinct and destroyed ancient volcanoes. The accumulation of such observations and knowledge is very important for geology.
Ancient destroyed volcanoes, active tens of millions of years ago and almost level with the surface of the Earth, help scientists recognize how molten masses located in the bowels of the Earth penetrate into the solid earth's crust and what results from their contact with rocks. Usually, at the points of contact, due to chemical processes, mineral ores are formed - deposits of iron, zinc and other metals.
Jets of steam in the craters of volcanoes, which are called fumaroles, carry with them some substances in a dissolved state. Sulfur, ammonia, and boric acid, which are used in industry, are deposited along the cracks of the crater and around such fumaroles.
Volcanic ash and lava contain many compounds of the element potassium and become very fertile soils. Gardens are planted on such soils or the land is used for field cultivation. Therefore, although it is unsafe to live in the vicinity of volcanoes, villages or cities almost always grow there.
Why do volcanic eruptions occur and where does such enormous energy come from within the globe?
The discovery of the phenomenon of radioactivity in some chemical elements, especially uranium and thorium, suggests that heat accumulates inside the Earth from the decay of radioactive elements. The study of atomic energy further supports this view.
The accumulation of heat in the Earth at great depths heats up the substance. Earth. The temperature rises so high that this substance should melt, but under the pressure of the upper layers of the earth's crust it is kept 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 cracks formed, the hot masses pass from a solid state to a liquid state.
A mass of molten rock, saturated with gases, formed deep in the bowels of the Earth is called. Under strong pressure from the released gases, melting the surrounding rocks, it makes its way and forms a vent, or channel, of the volcano.
The released gases explode by clearing a path along the vent, breaking apart solid rocks and throwing pieces of them to great heights. This phenomenon always precedes the outpouring of lava and is always accompanied by earthquakes in the vicinity of the volcano.
Just as something dissolved in a fizzy drink tends to come out when you uncork a bottle, forming foam, so in the crater of a volcano the foaming magma is rapidly ejected by the gases released from it, spraying and tearing the red-hot mass into pieces.
Having lost a significant amount of gas, magma pours out of the crater and flows like lava along the slopes of the volcano.
If magma in the earth's crust does not find its way to the surface, then it hardens in the form of veins in cracks in the earth's crust. It happens that molten magma solidifies underground over a large area and forms a huge homogeneous body that expands deeper. Its dimensions can reach hundreds of kilometers in diameter. Such frozen bodies embedded in the earth's crust are called batholiths.
Sometimes magma penetrates along a crack, lifts the layers of the earth like a dome and freezes in a shape similar to a loaf of bread. This kind of education is called laccolith.
Lava varies in content and can be liquid or thick. If lava is liquid, then it spreads quickly enough, forming on its way Lavaiadas. The gases that escape from the crater throw out hot fountains of lava, the splashes of which freeze into stone drops - lava tears. Thick lava flows quite slowly, breaks into blocks that pile on top of each other. If clots of such lava rotate during takeoff, they take the form of a spindle or ball. Such frozen pieces of lava of different sizes are called volcanic bombs. If lava, overflowing with gases, hardens, then stone foam forms - pumice. Pumice is very light and floats on water, and during underwater eruptions it floats to the sea surface. The pea- or hazelnut-sized fragments of lava ejected during an eruption are called lapilli. There is even finer igneous material - volcanic ash. It falls on the volcanic slopes and travels over very long distances, gradually turning into tuff. Tuff is a very light, porous material, it saws easily. It comes in various colors.
Several dozen active volcanoes are currently known on the globe. Most of them are located along the shores of the Pacific Ocean, including our volcanoes in Kamchatka.
When most people hear the word “volcano,” they think of Vesuvius, Fuji, or the volcanoes of Kamchatka—elegant, cone-shaped mountains.
In fact, there are other types of volcanoes that are completely different from the ones we are used to. We've already talked about it.
Now let's look at another type of volcanism - fissure.
Eruption of the Plosky Tolbachik volcano (photo from your-kamchatka.com)
The role of volcanoes in the development of life on Earth is significant. According to some hypotheses, the first living organisms arose around underwater volcanoes; volcanoes were able to melt the icy Earth and cause the spring of life 700 million years ago; volcanoes in Siberia “helped” begin the era of dinosaurs, and volcanoes in India helped end it. A volcano in Indonesia almost destroyed the human race, and a volcano in Yellowstone covered half of the modern United States with ash several times.
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How does a typical volcano form? Many of them are located in areas where tectonic plates collide. Examples are volcanoes in the “ring of fire” around the Pacific Ocean: in Kamchatka, Japan, Indonesia, New Zealand, and on the Pacific coast of North and South America.
When an oceanic tectonic plate collides with a continental plate, the oceanic plate moves downward as it is denser and heavier due to its chemical composition. In this case, the impurities contained in the ocean plate (in particular, water) are heated and begin to seep upward through the mantle under the continental plate. Oddly enough, this causes the solid matter in the upper layer of the mantle to melt and turn into magma. This occurs for the same reason that snow melts when salt is sprinkled on it: contamination of the solid with impurities lowers the melting point. Due to the large amount of gases dissolved in the magma and under high pressure, the magma rises and causes a volcanic eruption.
Volcanoes also form where plates diverge, for example, along the Great Rift Valley at the border of the African and Arabian tectonic plates.
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Erta Ale volcano in Ethiopia. (photo - Mikhail Korostelev)
As a result of this divergence, after a few million years, the modern territory of Somalia, Tanzania and Mozambique in eastern Africa will separate from the continent and a new ocean will arise in the middle of Africa.
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Kilimanjaro is a volcano in northeastern Tanzania, the highest peak in Africa.
Moreover, most of the places where plates diverge are not on the continent, but underwater, along mid-ocean ridges. It was in these places that one of the main biological discoveries of the twentieth century was made - the ecological systems of hydrothermal vents.
In the 1990s, German scientist Günter Wachtershauser proposed a hypothesis for the origin of life around hydrothermal vents, which was called the “iron and sulfur world.” According to this hypothesis, life on Earth was generated not by the Sun, but by the energy of volcanoes, and at the initial stage, even before the appearance of proteins and DNA, it used hydrogen sulfide, hydrogen cyanide, iron, nickel and carbon monoxide.
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Underwater volcano eruption
A couple of billion years later, volcanoes helped life on Earth once again. In the 1950s and 1960s, geologists Sir Douglas Mawson and Brian Harland found fossil evidence of a glacier that covered tropical latitudes between 850 and 630 million years ago. The researchers suggested that the Earth went through a period when it was completely covered in ice. This hypothesis is called Snowball Earth. Mawson and Harland were objected to by the Russian climatologist Mikhail Budyko, who made calculations and showed that there would be no one to defrost the frozen Earth, since the ice would reflect the sun's rays into outer space and the Earth would remain a “snowball” forever. Only in 1992, the American Joseph Lynn Kirschvink substantiated the assumption that the Earth was thawed by the greenhouse effect from gases released into the atmosphere by volcanoes. After this, real spring came on Earth: large multicellular animals of the Ediacaran and Cambrian periods arose.
Magmatism(Magmatism) - geological processes associated with the formation of magma, its movement in the earth's crust and its outpouring to the surface, including the activity of volcanoes (volcanism).
Volcanism(Volcanism; Vulcanism; Vulcanicity) - a set of processes and phenomena caused by the movement of magma in the upper mantle, the earth’s crust and its penetration from the depths of the Earth to the earth’s surface. A typical manifestation of volcanism is the formation of igneous geological bodies during the introduction of magma and its solidification in sedimentary rocks, as well as the outpouring of magma (lava) onto the surface with the formation of specific landforms (volcanoes).
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Karymsky Volcano is one of the most active volcanoes in Kamchatka
“Volcanism is a phenomenon due to which, during geological history, the outer shells of the Earth were formed - the crust, hydrosphere and atmosphere, i.e., the habitat of living organisms - the biosphere” - this opinion is expressed by the majority of volcanologists, however, this is far from the only idea about the development of geographical shells.
According to modern concepts, volcanism is an external, so-called effusive form of magmatism - a process associated with the movement of magma from the interior of the Earth to its surface. At a depth of 50 to 350 km, pockets of molten matter - magma - form in the thickness of our planet. Along areas of crushing and fractures of the earth's crust, magma rises and pours out onto the surface in the form of lava (it differs from magma in that it contains almost no volatile components, which, when pressure drops, separate from the magma and go into the atmosphere. With these outpourings of magma on the surface, volcanoes.
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Fuji is the highest mountain peak (3776 m) in Japan. It is a volcano with a crater with a diameter of about 500 meters and a depth of up to 200 meters. The most destructive eruptions occurred in 800, 864 and 1707.
Currently, over 4 thousand have been identified around the globe. volcanoes.
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From here
TO current include volcanoes that have erupted and exhibited solfataric activity (the release of hot gases and water) over the last 3500 years of the historical period. In 1980 there were 947 of them.
TO potentially active These include Holocene volcanoes that erupted 3500-13500 years ago. There are approximately 1343 of them.
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Mount Ararat is a volcano that is considered extinct. In fact, it, like other volcanoes of the Caucasus that exhibited volcanic activity in the late Quaternary: Ararat, Aragats, Kazbek, Kabardzhin, Elbrus, etc., is potentially active. In the central sector of the North Caucasus, eruptions of the Elbrus volcano were repeatedly observed in the late Pleistocene and Holocene.
TO conditionally extinct volcanoes are considered to be inactive in the Holocene, but have retained their external forms (younger than 100 thousand years old).
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Shasta is an extinct volcano in the southern Cascade Mountains in the United States.
Extinct volcanoes significantly reworked by erosion, dilapidated, showing no activity during the last 100 thousand. years.
Fissure volcanoes manifest themselves in the outpouring of lava onto the earth's surface along large cracks or splits. At certain periods of time, mainly at the prehistoric stage, this type of volcanism reached quite a wide scale, as a result of which a huge amount of volcanic material - lava - was carried to the surface of the Earth. Powerful fields are known in India on the Deccan Plateau, where they covered an area of 5,105 km2 with an average thickness of 1 to 3 km. Also known in the northwestern United States and Siberia. At that time, basaltic rocks from fissure eruptions were depleted in silica (about 50%) and enriched in ferrous iron (8-12%). The lavas are mobile, liquid, and therefore could be traced tens of kilometers from the place of their outpouring. The thickness of individual streams was 5-15m. In the USA, as well as in India, many kilometers of strata accumulated, this happened gradually, layer by layer, over many years. Such flat lava formations with a characteristic stepped relief form are called plateau basalts or traps.
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Trap basalts in the upper Colorado River.
Siberian Traps - one of the largest trap provinces is located on the East Siberian Platform. Siberian traps poured out at the boundary of the Paleozoic and Mesozoic, Permian and Triassic periods. At the same time, the largest (Permian-Triassic) extinction of species in the history of the Earth occurred. They are developed over an area of about 4 million km², the volume of erupted melts amounted to about 2 million km³ of effusive and intrusive rocks.
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The Putorana plateau is composed of trap basalts. Waterfall on the Putorana plateau. (Author - Sergey Gorshkov)
250 million years ago, at the border of the Paleozoic and Mesozoic eras, massive lava eruptions occurred in the territory of a volcanic province called the Siberian Traps, centered in the area of modern Norilsk. Over the course of several hundred thousand years, 2 million cubic kilometers of lava spread over an area of about 4 million square kilometers. At the same time, the largest extinction event in Earth's history occurred, destroying 96% of marine and about 70% of terrestrial animal species. One theory is that the mass extinction was caused by a "volcanic winter." First, volcanic dust polluted the atmosphere, causing global cooling and a lack of light for plants. At the same time, sulfurous volcanic gases caused acid rain from sulfuric acid, which destroyed plants on land and shellfish in the sea. Then global warming occurred due to the emitted carbon dioxide and the greenhouse effect.
After every major extinction event, new species flourish. After the extinction of Paleozoic species, dinosaurs became the favorites. In turn, dinosaurs went extinct 65 million years ago. For a long time, the extinction of dinosaurs was explained by the collision of the Earth with an asteroid that fell in the Yucatan Peninsula in southern Mexico. But according to new research by Gerta Keller from Princeton and Thierry Adatte from Switzerland, the main cause of the death of dinosaurs was the Deccan Traps - volcanoes that flooded half of the territory of modern India with lava over 30 thousand years and also caused a “volcanic winter”.
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Deccan Plateau (Deccan Plateau or Southern Plateau), which covers the territory of almost all of South India
The Deccan Plateau is a large trap province located in Hindustan and makes up the Deccan Plateau. The total thickness of basalts in the center of the province is more than 2,000 meters; they are developed over an area of 1.5 million km². The volume of basalts is estimated at 512,000 km3. The Deccan Traps began to flow at the Cretaceous-Paleogene boundary, and are also associated with the Cretaceous-Paleogene extinction event, which wiped out dinosaurs and many other species.
Scientists knew that the series of eruptions that created the Deccan Trap Province occurred near the Cretaceous-Paleogene boundary, which is when the mass extinction occurred. Now, after studying rocks in India and marine sediments from this era, they claim that they have for the first time been able to clearly link volcanism on the Deccan Plateau and the death of the dinosaurs.
The most powerful phase of the period of volcanism in the Deccan ended when the mass extinction had already begun. At the same time, climate-changing carbon dioxide and sulfur dioxide were released from these volcanoes (the lava from which spread over many hundreds of kilometers, forming layers of basalt two kilometers thick) was emitted 10 times more than when the asteroid hit Yucatan.
Scientists also managed to explain the delay in the sharp rise in the development of marine creatures (which is clearly visible in marine fossils after the Cretaceous-Paleogene boundary). The fact is that the last surge of volcanism in the Deccan occurred 280 thousand years after the extinction. This delayed the restoration of the number of microorganisms in the seas.
Currently, fissure volcanism is widespread in Iceland (Laki volcano), Kamchatka (Tolbachinsky volcano), and on one of the islands of New Zealand. The largest lava eruption on the island of Iceland along the giant Laki fissure, 30 km long, occurred in 1783, when lava reached the surface for two months. During this time, 12 km 3 of basaltic lava poured out, which flooded almost 915 km 2 of the adjacent lowland with a layer 170 m thick. A similar eruption was observed in 1886. on one of the islands of New Zealand. For two hours, 12 small craters with a diameter of several hundred meters were active over a 30 km segment. The eruption was accompanied by explosions and the release of ash, which covered an area of 10 thousand km2, near the fissure the thickness of the cover reached 75 m. The explosive effect was enhanced by the powerful release of vapors from the lake basins adjacent to the crack. Such explosions, caused by the presence of water, are called phreatic. After the eruption, a graben-shaped depression 5 km long and 1.5-3 km wide formed in place of the lakes.
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The total volume of erupted pyroclastics was 1 km3, lava - 1.2 km3, total - 2.2 km3. It was the largest basaltic eruption in the Kuril-Kamchatka volcanic belt in historical times, one of fifteen eruptions of the 20th century, the volume of products of which exceeded 1 million cubic meters. km., one of the six large fissure eruptions observed in the world in historical times. Thanks to intensified systematic research, the Great Fissure Tolbachik Eruption is currently one of the three most studied large volcanic eruptions.
The lavas that caused such large-scale events in the past are represented by the most common type on Earth - basalt. Their name indicates that they subsequently turned into a black and heavy rock - basalt.
Vast basalt fields (traps) hundreds of millions of years old hide still very unusual forms. Where ancient traps come to the surface, as, for example, in the cliffs of Siberian rivers, you can find rows of vertical 5- and 6-sided prisms. This is a columnar separation that is formed during the slow cooling of a large mass of homogeneous melt. Basalt gradually decreases in volume and cracks along strictly defined planes. Sounds familiar, doesn't it?
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Israel. Zawitan River. Prism pools. (and this is already mine)
The Golan Heights (Ramat HaGolan) are part of a basalt plateau of volcanic origin, with a total area of 35,000 sq. km. Geologists believe that the age of the Golan is about one and a half million years.
Bordering the Jordan Basin in the west, the Golan Plateau in the east reaches the Nahal Rakkad canyon (a tributary of the Yarmouk River) and a chain of high hills (Hermon spurs), descending from north to south from 1000 m to 350 m above sea level. Several dozen extinct volcanoes (including Avital, Varda and Hermonit, over 1200 m above sea level), some with intact and deformed craters, covered the plateau and adjacent areas with lava in recent geological times, giving rise to a characteristic landscape of black basaltic rocks and brown tuff (volcanic emissions) lying on top of sedimentary chalk and limestone rocks. Running mainly to the west and densely covered with bushes along the banks, the streams washed deep gorges into the soil, often with waterfalls on the ledges.
And the basalt plateau spilled over other rocks, and ledges, and waterfalls. and prisms in rivers - well, they are very suitable for fissure volcanism. P.S. All photographs illustrating the text were found on the Internet. Where she knew, she indicated the exact authorship.
