Types of volcanic eruptions. Eruption of ash streams. Scientific methods and means of research

The eruption is a spontaneous discharge of lava, ash, fire from the crater of a volcano or ejection of a column of steam and boiling water from the mouth of a geyser.

Eruption  - the process of volcanic eruption on the earth's surface of heated debris, ash, magma outpouring, which, pouring to the surface, becomes lava. A volcanic eruption can have a time period from a few hours to many years.

Volcanic eruptions are geological emergencies that can lead to natural disasters.

Types of volcanic eruptions

Types of volcanic eruptions, as a rule, are named after famous volcanoes, where characteristic behavior is observed. Eruptions of some volcanoes can have only one type during a certain period of activity, while others can demonstrate a whole sequence of types of eruptions. There are various classifications, among which are common for all types.

Hawaiian type

Eruption Hawaiian type can occur along cracks and faults, as during the eruption of the Mauna Loa volcano in Hawaii in 1950. They can also manifest themselves through the central muzzle, as in the eruption of the Kilauea Iki volcano Kilauea (Hawaii) in 1959.

This type is characterized by effusions of liquid, highly mobile basaltic lava forming huge flat shield volcanoes. Pyroclastic material is practically absent. During eruptions through cracks fountains of lava are thrown out through faults in the rift zone of the volcano and spread down the slope by streams of low power for tens of kilometers. When erupting through the central channel, the lava is ejected upwards by several hundred meters in the form of liquid pieces of "cake" type, creating shafts and spray cones. This lava can accumulate in old craters, forming lava lakes.

For the first time volcanoes of this type were described in Iceland (Krabla volcano in the north of Iceland, located in the rift zone). The type of eruption of the Fournez volcano on the island of Reunion is very close to Hawaiian.

Strombolian type

The Strombolian type (from Stromboli volcano on the Aeolian Islands to the north of Sicily) eruptions is associated with a more viscous main lava that is emitted by different bursts of force from the vent, producing relatively short and more powerful lava flows. When explosions are formed slag cones  and plumes of twisted volcanic bombs. The Stromboli volcano regularly throws out the "charge" of bombs and pieces (the last eruption of March 2007) of hot incandescent slag.

Plinian type

Plinian type (volcanic, vesuvian) eruptions received its name after the Roman scientist Pliny the Elder, who died during the eruption of Vesuvius in 79 AD. e., Destroyed three major Roman cities of Herculaneum, Stabia and Pompeii.

A characteristic feature of this type of eruption are powerful, often sudden explosions, accompanied by the release of a huge amount of tephra, which forms pumice and ash streams. Plinian eruptions are dangerous, since they occur suddenly, often without preliminary foreboding events. Major Plinian eruptions, such as the eruption of St. Helens volcano on May 18, 1980, or Pinatubo eruption in the Philippines on June 15, 1991, can throw ash and volcanic gases for tens of kilometers into the atmosphere. With the Plinian type of eruptions, rapidly moving pyroclastic flows often occur.

To this type of eruption is the grand explosion of the volcano Krakatau in the Sunda Strait between the islands of Sumatra and Java. The sound of the eruption was heard over 5014 km, and the post of volcanic ash reached almost 100 km. A huge wave - a tsunami, a height of 25 to 40 meters, from which 40,000 people died in the coastal areas. On the site of the islands of Krakatau, a giant caldera was formed.

Peleic type

Peleic type of eruptions is characterized by the formation of grandiose red-hot avalanches or scorching clouds, as well as the growth of extrusive domes of extremely viscous lava. The name of this type of eruption was received from the volcano Mont-Pele on the Martiniqa cautious in the group of small Antilles, where on May 8, 1902, the explosion of the summit of the dozing volcano was destroyed, and a hot heavy cloud burst from the vents destroyed the city of Saint-Pierre with 28,000 inhabitants . After the eruption a "needle" of viscous magma emerged from the vent, which reached a height of 300 meters, soon collapsed. Such an eruption occurred on March 30, 1956 in Kamchatka, where the peak of the Nameless Volcano was destroyed by a grand explosion. A cloud of ashes rose to a height of 40 km, and on the slopes of the volcano came the red-hot avalanches, which, melting the snow, gave rise to powerful mud flows.

Gas or phreatic type

Gas or phreatic type of eruptions (also used Bandaisan (Bandai) type), at which fragments of hard, ancient rocks are thrown into the air (the new magma does not erupt), is caused either by magmatic gases or is associated with superheated groundwater. Phreatic activity is usually weak, but there are strong manifestations, such as the eruption of the Taal volcano in the Philippines in 1965 and La Grande Soufriere on the island of Guadalupe.

Underground type

The subglacial type of eruptions is attributed to volcanoes located under the ice or glacier. Such eruptions can cause dangerous floods, lahars and ball lava. Only five such eruptions have been observed to date.

Eruption of ash streams

Eruptions of ash streams were widespread in the near geological past, but in the present they were not observed by man. To some extent, these eruptions should resemble scorching clouds or incandescent avalanches. The magmatic melt comes to the surface, which, boiling, bursts and the red-hot pumice lapilli, fragments of volcanic glass, minerals, surrounded by a red-hot gas shell, move with a great speed to a slope. A possible example similar eruptions may be the eruption of 1912 in the area of ​​the volcano Kathmai in Alaska, when from numerous cracks an ash stream, spreading about 25 km, flowed down the valley, having a thickness of about 30 m. The valley was called "Ten thousand fumes" because of the large number a pair that stood out for a long time from the central part of the stream. The volume of ash streams can reach tens and hundreds of cubic kilometers, which indicates a rapid emptying of the outbreaks with a melt of acidic composition.

Hydroexplosive eruptions

Hydroexplosive eruptions occur in the shallow waters of the oceans and seas. They are distinguished by the formation of a large amount of vapor arising from the contact of incandescent magma and sea water.

Icelandic type

The Icelandic type (from the volcanoes of Iceland) is characterized by the ejections of a very liquid basaltic lava containing pyroclastic material. As a rule, form flat shield volcanoes. Eruption occurs through cracks. (Hekla, Iceland). A historical example of an eruption of the Icelandic type was the eruption of Lucky in Iceland in 1782.

Type of thunder crack

This type was recorded during the eruption of the volcano on the island of Palma in 1915. Occurs on dome volcanoes. On the cracks that begin to go from the magma chamber, there is lava, but no longer viscous. When cracks reach the crater, explosive eruptions occur (with explosions).

1. Volcanism is an effusive magmatism. Volcanoes and their structure.

3. Eruption products - liquid, solid, gaseous. Types of lavas for chemistry and their differences in properties. Potpolcanic activity.

4. Regularities in the distribution of volcanoes. Features of volcanism of various structural and tectonic zones of the earth's crust.

Volcanism is an effusive magmatism. Volcanoes and their structure

Volcanism is understood as the outflow to the surface of lava, or the escape of gases, or the ejection of detrital material by the force of gases escaping from the magma that has not reached the surface of the Earth. The name of the volcano comes from the island of Vulcano in the southern part of the Aeolian Islands, where powerful eruptions have been known for a long time. Volcanoes act periodically. It is accepted to distinguish active, extinct and ancient volcanoes. Their distribution on the Earth is very uneven. The total number of active volcanoes on the continents is about 800 (79 underwater). A large part, for example, of 552 active volcanoes is located along the shores and islands of the Pacific Ocean. Extinct volcanoes are very many - for example, Elbrus in the Caucasus. This division should be considered conditional, because there is no certainty that some of the extinct volcanoes  will not resume their activities. There are 51 active volcanoes on the territory of Russia. All of them are located on the active continental margin in the limits of Kamchatka and the Kuril island arc.

In the 1st century BC. Strabo wrote that Elbrus is an active volcano, and now it is considered extinct. Extinct volcanoes often make themselves felt, for example the Fujiyama volcano operated in 864 and 1707. Vesuvius in 63 year gave a weak eruption, and in 79 the catastrophic. As a result of this eruption of the city of Pompey, Herculaneum and Stabia were buried under ashes up to 7 m high. Then the mud flows ( lahars) completed the burial of cities. A strong eruption of Vesuvius occurred also in 1631. The red-hot lava flow almost completely destroyed the city of Torre del Greco. Later, the largest eruption of Vesuvius occurred in 1906 and the last in 1944. Many volcanoes are gradually destroyed and smoothed out, but can later be reborn. New volcanoes may appear. So in 1943 in Mexico on a flat field the volcanic cone unexpectedly grew. About the ancient volcanoes can often be judged only by products of volcanic activity - volcanic selling.

The nature of the eruption of the magmatic melt depends on its composition, temperature, pressure, concentration of gases and other parameters. The movement and intensity of degassing of gases largely determine the eruption process lava  (lava is a magma devoid of gases). With a relatively quiet release of gases, an outflow occurs, effusion  lava flow. When the gases are separated quickly, instantaneous boiling of the melt takes place, and the magma explodes, explosive  eruption. If the magma is viscous and its temperature is low, then the melt is slowly squeezed out onto the surface, extrusion  magma.

All volcanoes can be attributed to one of two types - central(eruptions occur through the central outlets) and cracked(lava flows from a crack in the earth's crust). The central volcano represents a cone-like mountain with slopes up to 30 ° and more (Fig.). Each volcano has feed channel  and muzzle, along which the products of the eruption rise from below (Fig.). At the top of the mountain there is a cup- crater, which is the upper end of the volcano's mouth. In the periods between eruptions in the crater, water usually accumulates and a lake is formed.

Volcanoes of the central type are divided into monogenic and polygenic. Monogenic volcanoes are represented by relatively small cones, on top of which there is a crater. Complex polygenic volcanoes consist of several cones formed by lava flows and strata tephra  (ash). In the structure of cones of volcanoes, alternating effusive and explosive products are often observed. Such layered volcanoes are called stratovolcanoes  (stratum - layer).

Fig. . The eruption of the Klyuchevsky volcano (Kamchatka), the highest volcano in Europe and Asia. The eruption occurs at the bottom of a huge crater with a diameter of about 600 m (photo by Y. Demyanchuk).

Small craters inside the larger are called - boccia. The shape of the volcano, when there is a smaller volcano in the larger volcano, is called somma.If the crater reaches a large size, up to 15-20 km in diameter, then such a crater is called caldera. Calderas are of two types - failure, in which the volcanic structure is lowered into a magmatic chamber released after the eruption of magma (Fig.) and explosive(explosive) formed as a result of strong explosions and emissions of a large amount of solid material from the crater and the mouth of the volcano.

Fig. . The structure of volcanic apparatus: 1 - crater; 2 - side craters; 3 - muzzle (channel); 4 - somma; 5 - caldera; 6 - MAAR (according to GP Gorshkov, AF Yakushova, 1962).

Fig .. The origin of the caldera. The eruption begins, magma rushes to the surface (A, B), magma in the form of slag and tephra is released into the atmosphere, a free space (C) is formed under the cone, along which part of the cone (D) falls through the fault. Depression is filled with water and there is a caldera lake (E). From the work of Z. Kukala, 1985.

Volcanoes of central type include shield volcanoes.At them the lava spreading does not form a cone. It is clear that this can only be if the lava is not viscous, flowing. Some of the shield volcanoes reach enormous dimensions. For example, the Mauna Loa volcano in Hawaii reaches 110 km across. Close to volcanoes of the central type, so-called, maars and diatremes - monogenic volcanoes . Maara- Rounded hollows. They are more than 3 km in diameter and as deep as 0.5 km (Bayern). There are no lava flows or slags. At the depth of the maar, magmatic rocks are found. Most likely, maars are formed as a result of a one-act eruption in the form of an explosion. Diatreme- a vertically expanding upward circular channel (a breakthrough track to the surface of volcanic gases). The diameter of diatremes is up to 800 m. This channel, otherwise it is called explosion tube.They can be filled with specific breeds - kimberlites, which in some cases contain diamonds.

Fissure-type volcanoes are characterized by the fact that the outflow of lava predominantly of the main composition occurs along fissures. This type of volcano was widespread in past geological periods, currently found only in Iceland. Iceland belongs to the geologically active zone of our planet, so there are many active volcanoes on the island. The largest of them - Hekla erupted for the last time in 1991. Fissure-type volcanoes, as a rule, do not form ground structures. Most of these volcanoes are under water, the length of such cracks reaches several tens of kilometers.

Novosibirsk State University

Faculty of Geology and Geophysics

Department of Oil and Gas Geology

Bak Elena Petrovna

Course 1, group 5504

Course work

Abstractive Theme :

Volcanoes: types, structure, products of eruption

scientific adviser

LABEKINA Irina Alexeevna

Reviewer

Grinenko Maxim Igorevich

Novosibirsk

ANNOTATION

In this course work, materials on the theme "Volcanoes: types, structure, eruptions" are collected, and the causes of the process under consideration and its consequences are also described below. The work is written on the basis of a complex multilevel plan containing eleven basic points (including the introduction, conclusion and list of used literature), which include the goals and objectives of the research, as well as information about objects and subjects of research. It consists of 20 pages, on which are placed 3 figures (p.10,12 and 16 respectively). At the end of the course work (on page 20) there is a list of all used literature.

In the given course, the materials on the theme "Volcanoes: types, structure, products of eruption" are assembled. The work is written on the basis of the complex multilevel plan, containing eleven basic items (including introduction, conclusion and list of the used literature), including the purpose and research problem. It consists of 20 pages, on which 3 figures (page 10,12 and 16 accordingly). At the end of the course work (on page 20) there is a list of used literature.

Before a perusal of course I recommend to address to a TABLE of CONTENS

1.   Introduction .................................................... .................. 4

2. Formulation of the topic and problems ..................................... 5

3. Historical essay ................................................................. .6

4. Aims and objectives of the research ............ .. .............................. ..7

5. Objects and subject of research ... .. ......... ... ............... ...... 7

6. Modern knowledge in this field.

6.1. Types of volcanoes .............................. .......... ...... ...... 8

6.2. The structure of volcanoes ...................... .... ............... ...... 11

6.3. Eruption products .................................... ...... 13

6.4. Volcanoes in the service of man ............................... .14

6.5. Volcanic activity on the moon ......... .. ...... ...... .17

7. Scientific methods and means of research ............... .17

8. Links to other problems and challenges ........................ ...... .18

9. The place of this topic in the curricula and subjects of the NGF NGF ...... 18

10. Conclusion ...................................................... ................ 19

11. References ................................................................................. .20

1. Introduction

Choosing a topic for the course work, I was guided by such questions as: "What more would I like to know?" And at the same time "What will my classmates be interested in? ". And my choice was based on volcanoes.

On Earth, dozens of volcanoes erupt every year. Some of them reach catastrophic proportions, bringing untold calamities to people.

This peculiar and formidable phenomenon of nature in the past was incomprehensible to man and gave rise to fear and various superstitions. Now scientific and practical study of volcanoes makes it possible to know the composition of the deep layers of the Earth and to use lava, hot water, steam in the interests of man. But even today scientists can not predict the beginning of volcanic eruptions.

The manifestations of volcanism are one of the most characteristic and important geological processes that are of great importance in the history of the development and formation of the earth's crust. No region on Earth - whether a continent or an oceanic depression, a folded region or a platform - did not form without the participation of volcanism.

Volcanoes conceal secrets. And all the unknown always attracted humanity. And I was not an exception ...

2. Formulation of the topic and problems

In its most general form, it can be said that volcanoes  are geological formations that have arisen over cylindrical channels or cracks in the earth's crust through which hot lava erupts from the depths of the earth (differs from magma in that it almost does not contain volatile components which, when pressure falls, separate from magma and escape into the atmosphere)

volcanic ash, debris and hot gases. Depending on the relationship between erupting lava, ash, fragments of rocks and gases around the mouth, a volcanic structure forms in one form or another. With very strong explosions, when there are only huge disruptions, it does not even arise.

If you climb to the top of an active volcano during its tranquil state, you can see crater  (in Greek - a large bowl) - a deep cavity with steep walls, similar to a giant bowl. The bottom of the crater is covered with fragments of large and small stones, and jets and gases of steam rise from cracks on the bottom and walls of the crater. After the eruption, the crater is destroyed and a hollow with vertical walls is formed - caldera .

At present, over 4,000 people have been identified on the globe. volcanoes.

The active ones include volcanoes erupting and showing solfatar activity (release of hot gases and water) over the last 3500 years of the historical period. In 1980, there were 947 of them.

Potentially active volcanoes erupting 3500-13500 years ago. There are approximately 1343 of them.

To conventionally extinct volcanoes, they include those that did not show activity 3500-13500 years ago, but retained their external forms (age under 100 thousand years).

Extinct - volcanoes substantially reworked by erosion, dilapidated, not showing activity during the last 100 thousand years. However, such a division is arbitrary, since volcanoes, considered extinct, sometimes resume their activity suddenly. So it was, for example, with the volcano Bezymyannym in Kamchatka, which in 1955 quite unexpectedly began to erupt.

The location of volcanoes on Earth is not accidental, but obeys certain regularities. Volcanoes are confined to areas of the earth's crust with the least strength and maximum mobility. The same patterns can be traced in the distant geological past.

3. Historical essay

Mighty and majestic, gloomy and formidable in ancient times, incomprehensible pictures of volcanic eruptions made a strong impression on people, and the volcanoes caused superstitious fear and veneration.

There are many legends connected with volcanoes. In ancient Greece was the god of fire Hephaestus, the Greeks considered him to be the patron of the blacksmith's craft and a skilled blacksmith. Looking at the smoking top of the volcano on the island of Guyeru (in the group of the Aeolian Islands of the Mediterranean), they believed that there, in the depths of the mountain, Hephaestus forges weapons. Later, the Romans began to call the god of fire Vulcan (in Latin, vulcanus-fire, flame), and the island of Hyeru was renamed Vulcano.

The name "volcano" was subsequently applied to all the mountains that erupted in the fire, lava, ash.

The Catholic Church taught that volcanoes serve as a place of eternal punishment for sinners. And the inhabitants of Java believed that the volcano Sumbing is that "nail" by which the island is attached to the Earth.

Over time, people ceased to deify volcanic eruptions, began to study their nature. Already philosophers of the ancient world seriously thought about the causes of volcanic eruptions.

The first scientific hypothesis about the origin of volcanoes belongs to Aristotle. He assumed that "the earth contains in its bosom the sources of vitality and fire, hidden from the eyes of men; have many exits to the light - the outlet ducts of steam and fire, so Etna and Aeolovs (Lipari) islands spew "inflamed glandular earthen blocks."

Since the Renaissance, a systematic study of volcanism begins. In the various hypotheses put forward by scholars in subsequent centuries, there were many infidels, at times naive, but in general they all contributed to the development of the science of volcanoes. Nowadays an independent branch of geology has been created - volcanology, which studies the activity of volcanoes, their origin, products of eruptions, the regularities of placing volcanic mountains on the surface of the earth.

In the middle of the XIX century on the slope of the Vesuvius volcano in Italy, the world's first special volcanological observatory was created, the second was organized in 1911 in the Hawaiian Islands - on top of the Kilauea volcano.

Now such observatories exist in many countries (Indonesia, Japan, the Philippines, etc.).

In the USSR in 1935, a volcanological station named after Academician Levinson-Lessing was organized. It is located on Kamchatka, near the greatest volcano  THE USSR - Klyuchevskaya hills. In 1962, the second station was opened Avachinsky volcano, near Petropavlovsk-Kamchatsky.

Soviet volcanologists carried out a huge work on the study of volcanoes. The works of Academician A.N. Zavaritsky, Corresponding Member of the USSR Academy of Sciences B.Piip, Professors V.Vlodavets, G.S. Gorshkov, S. I. Naboko, A.E. Svyatlovskiy and others represent an invaluable contribution to science about the Earth.

4. Goals and objectives of research

The activity of many volcanoes is one of the most formidable phenomena of nature. Volcanic eruptions are often accompanied by disasters, the death of entire cities and villages, the destruction of huge material values.

For example, in 1883, when a volcanic island of Krakatau collapsed, a giant wave arose, destroying 36,000 people on the coast of the neighboring islands of Java and Sumatra. At the eruption of the volcano Tambor in Indonesia in 1815, according to one data, 57,925 people, on the other - about 92,000. At the same time, large areas of arable land on the island of Sumbawa, on which the volcano is located, and on the neighboring island of Lombok were destroyed.

Sometimes in connection with the eruption of volcanoes there are massive diseases. It is known that in the Congo during eruptions of volcanoes in rainy periods the population grasps a disease similar to dysentery; in reality it is a more serious and dangerous disease. When volcanic eruptions are released, gases saturated with HCl and SO2, which dissolve in rainwater and form acids. They enter water, and this water is then used for drinking by the population and causes severe illness.

The internal energy of the Earth, with which the activity of volcanoes is connected, is not subject to man. But people are taking different measures to reduce the disastrous consequences of the catastrophic activity of volcanoes. The easiest way would be to move away from dangerous places. But often people can not go far from volcanoes, especially on the Japanese, Philippine, Indonesian and other islands. At that time, timely information of the population about the resumption of volcano activity acquires particular importance. These activities are called passive protection. If the volcano has begun to act, then effective measures to protect people and property from ash falls, flows of fire lava and other dangerous phenomena of volcanic activity are used. For this purpose, special stations and observation posts are organized.

In some cases, an active protection against volcanic eruptions is possible. It consists of: 1) bombardment of moving lava flows and walls of craters through which lava flows through aviation or artillery; 2) in the creation of dams and other obstacles in the path of lava movement;

3) in carrying out of tunnels to craters for water descent of crater lakes.

5.Objects of direct observations and subject of research

In this course work, the object of research is volcanoes, and objects their types, structure and products of the eruption.

6. Current knowledge in this field

6.1. Types of volcanoes

Each active volcano has its own individual characteristics. Moreover, there are no two completely identical volcanoes, just as there are not two absolutely identical people among the multi-million population of our planet. However, volcanoes can be combined into groups with similar features.

For example, three types of volcanoes are distinguished:

1) Area volcanoes.   At present, such volcanoes do not occur, or one can say they do not exist. Since these volcanoes are confined to the exit of a large number of lava on the surface of a large area; ie from here we see that they existed at 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.

2) Fissured volcanoes.   They are manifested in the outpouring of lava on the earth's surface through large cracks or splits. In certain periods of time, mainly at the prehistoric stage, this type of volcanism reached a rather 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 cover an area of ​​5. 105 km2 with an average power of 1 to 3 km. Also known in the northwest of the USA, in Siberia. At that time, basalt rocks of fissures were depleted in silica (about 50%) and enriched in bivalent iron (8-12%). Lava mobile, liquid, and therefore traced to tens of kilometers from the site of its outpouring.

The power of the individual flows was 5-15 m. In the United States, as well as in India, many kilometers thick accumulated, this occurred gradually, after formation, for many years. Such flat lava formations with a characteristic stepped form of relief were called plateau basalts  or traps.

At present, fissure volcanism is widespread in Iceland (Lucky volcano), Kamchatka (Tolbachinsky volcano), and on one of the islands of New Zealand. The largest eruption of lava on the island of Iceland along the giant crack of Laki, 30 km in length, occurred in 1783, when the lava came to the surface for two months. During this time, 12 km3 of basaltic lava flowed, which flooded almost 915 km2 of adjacent lowlands with a layer of 170 m thick. A similar eruption was observed in 1886 on an island in New Zealand. Within two hours, at a distance of 30 km, there were 12 small craters with a diameter of several hundred meters. The eruption was accompanied by explosions and the release of ash, which covered an area of ​​10 thousand km2, 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, phreatic.  After the eruption in place of the lakes, a graben-like depression 5 km long and 1.5-3 km wide formed.

3) The central type.   This is the most common type of effusive magmatism. It is accompanied by the formation of cone-shaped volcanic mountains; their height is controlled by hydrostatic forces. The fact is that the height h,   on which liquid lava is capable of rising pl   , from the primary magmatic focus, is due to the pressure of a solid lithosphere H   and density ps . This relationship can be expressed by the following equation:

ghps = gHpl

where, g   acceleration of gravity.

( h- H) / H = ( ps - pl) / ps

Expression<h- H\u003e   and there is the height of the volcanic mountain 5 h ; attitudes ( ps - pl) / ps   can be expressed as a certain density coefficient j , then S h = jH . Since this equation connects the height of the volcano with the thickness of the lithosphere through a certain density coefficient, which for different regions is different, then the height of the volcano in different regions of the globe is different.

Summarizing data on the activity of volcanoes of the central type, scientists proposed to classify volcanoes according to the nature of their activity (Fig. 1).

Hawaiian type the eruptions include Mauna Loa, Kilauea in the Hawaiian Islands, some volcanoes of Iceland, Nemljagir and Niragongo in Africa. On many grounds, the Flat Tolbachik in Kamchatka is close to the Hawaiian type. The activity of these volcanoes is characterized by calm, without explosions, the outflow of flowing basaltic lava and the absence of powerful emissions of gases and vapor. When the crater overflows, the lava overflows over the edge and flows down the slopes, forming long streams. The slopes of this type of volcanoes are very flat, in shape they resemble a giant shield, so they are also called shield volcanoes.

According to the activity of the volcano Stromboli isolated strombolian type  eruptions. Basalt lava of these volcanoes is somewhat more viscous than Hawaiian, but still quite mobile. Volcanic gases are released from it with explosions, forming a swirling volcanic bomb. There is no ashes or very little. Volcanoes of conical shape with a truncated apex consist of interlacing of lavas and products of explosive activity. are typical layered volcanoes (stratovolcanoes).

For vulcan type  the volcanic eruptions, exemplified by the Volcano volcano on the Aeolian Islands, are characterized by a viscous andesite-basaltic lava, which hardly gives up gases. Often the lava closes the mouth of the volcano. The gases accumulate under the volcanic cork and break out with great force, throwing out bombs, lapilli and ash. Pieces of viscous lava in the air can not be twisted, but cracked on cooling, becoming a bread crust. During eruptions, lava also flows in the form of short streams. Frozen lava has a blocky surface.

The Vesuvian type  eruptions is close to Vulcan, but differs from it by very strong explosive activity. Volcanic eruptions of this type are caused by somewhat more acidic, with more silica, and therefore more viscous lava. The gases and vapors accumulating under the lava plug break through to the top, throwing out a large number of  Ashes, lapilli and bombs. The shape of bombs in the form of flat cakes and caravoys with a cracked surface is characteristic (twisted forms are not formed because of the viscous state of the lava). The streams of lavas are short, usually irregular in shape. Volcanoes of the type of structure belong to stratovolcanoes. Vesuvian type includes Vesuvius and Etna in Italy, many volcanoes of Kamchatka and the Kuril Islands.

Plinian type The eruption is the further development of the Vesuvian. It is characterized by strong explosions of the upward gas, which rises to a height of several kilometers, and then forms an expanding cloud, in shape resembling the crown of the Italian pine pine. Strong explosions lead to the destruction of the volcanic cone.

Features of volcanic eruptions peleic type  (from the name of the volcano Mont Pele) are due to the very high viscosity of the lava emitted, which, when frozen, firmly clogs the vent of the volcano. Gases at depth develop enormous pressure, and in the end there is a huge explosion with the release of a huge amount of ash, bombs and gases. This gas high-heated cloud with a temperature of up to 7000C, filled with stone material, swiftly slides down the slope of the volcano, carrying with it destruction and death. At the same time, the cloud grows upward with a huge curly pillar. Such high-heated clouds of ash and gas are called scorching clouds. Peleys volcanoes, besides Mont-Pele, include Katmai in Alaska, Nameless on Kamchatka, and others.

Finally, there are eruptions bandai-type  (Bandai-san is one of the major Japanese volcanoes), which is characterized by purely explosive activity, without the release of lava in the form of streams or domes on the surface. The crater of the volcano is covered with a 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 is destroyed and the mass of frozen lava is thrown out. Fresh lava does not come out to the surface. This includes Krakatau in Indonesia, as well as some other volcanoes.

The types of activity considered are volcanoes of a central type that dominate the modern period of the Earth's life. But in the past geological epochs, fracture type eruptions were also widespread, for which lava flows from the cracks in the earth's crust. Currently, eruptions of this kind occur in Iceland, therefore, volcanic fractures are also called volcanoes icelandic type.

It should not be thought that the same volcano acts on only one type. Volcanoes pass through a certain path of development during their lifetime, so the nature of their activity also changes. The action of a volcano according to a certain type is essentially temporary, although it covers time intervals 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. For example, in a historical time, Vesuvius erupted in the style of Stromboli, Vulcano, the Plinian, and threw out scorching clouds.

6.2.Construction of volcanoes  (Figure 2)

The roots of the volcano, i. its primary magmatic focus 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 magmatic focus, which directly feeds the volcano through the vent. The cone of the volcano is composed of the products of its eruption. At the top is a crater - a cup-shaped depression, which is sometimes filled with water. The diameters of the craters can be different, for example, in the Klyuchevskaya Sopka - 675 m, and a famous volcano  Vesuvius, who killed Pompey - 568m. After the eruption, the crater is destroyed and a depression is formed with vertical walls - the caldera. The diameter of some calderas reaches many kilometers, for example the caldera of Aniakchan volcano in Alaska is 10 km.

6.3.Products of the eruption

When a volcano erupts, products of volcanic activity are released that 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 out clots of hot liquid lava. Also, during the eruption of volcanoes, a powerful release of gas jets occurs, creating huge mushroom clouds in the atmosphere. Such a gas cloud consisting of droplets of molten (over 7,000 ° C) ash and gases formed from the cracks of the Mont-Pele 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 very much from place to place and in time. They depend on temperature, and in the most general form on the degree of degassing of the mantle, and the type of the earth's crust. According to Japanese scientists, the dependence of the composition of volcanic gases on temperature is as follows:

Temperature, 0С Composition of gases (without water)

1200-800 HCl, CO2, H2 O, H2 S, SO

800-100 HCl, SO2, H2 S, CO2, N2, H2

100-60 H2, CO2, N2, SO2, H2 S

60 CO2, N2, H2 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  - are characterized by temperatures in the range 600-12000С. It is represented by lava.

The viscosity of lava is due to its composition and depends mainly on the content of silica or silicon dioxide. At its high value (more than 65%), lavas are called sour ,   they are relatively light, viscous, slow-moving, contain a large number of gases, cool slowly. A smaller silica content (60-52%) is characteristic for averages  lavas; they are as acidic as the more viscous, but they are usually warmer (up to 1000-12000С) in comparison with acidic ones (800-9000С). Basic  lava contain less than 52% silica and therefore more liquid, mobile, freely flow. When they solidify, a crust forms on the surface, under which further fluid movement takes place.

Solid  products include volcanic bombs, lapilli, volcanic sand and ash. At the time of the eruption, they fly out of the crater at a speed of 500-600 m / s.

Volcanic bombs  - large pieces of hardened lava, a few centimeters to 1 m or more in size, and several times in mass (during the eruption of Vesuvius in 79 g., volcanic bombs 'tears of Vesuvius' reached tens of tons). They are formed during an explosive eruption, which occurs with the rapid release of magma from the gases contained in it. Volcanic bombs come in 2 categories: 1st, arising from a more viscous and less saturated with lava gases; they retain the correct shape even when striking the ground because of the hardening crust formed during their cooling. The 2 nd,  are formed from a more liquid lava, during flight they acquire the most bizarre forms, which are further complicated by impact. Lapilli  (Latin "lapillus" - small stone) - relatively small fragments of slag in size 1,5-3cm, having a variety of shapes. Volcanic sand  - consists of relatively small particles of lava (³ 0.5 cm). Even smaller fragments, with a size of 1 mm or less form volcanic ash, which settles on the slopes of the volcano or at some distance from it forms a volcanic tuff. Powerful emissions of ash, reducing solar radiation, cause a decrease in temperature. Thus, the eruption of the volcano El Chichon in Mexico in 1982 led to a decrease in the average temperature on the globe by 2.5 ° C. Cooling occurred after the eruption of the volcano Pinatubo in 1991 in the Philippines.

6.4. Volcanoes in the Service of Man  (Fig. 3)

The internal energy of the Earth, with which the activity of volcanoes is connected, is not yet subject to man, and therefore we can not yet get rid of this terrible phenomenon. But people find different means to reduce this danger. Moreover, a person 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 expense associated with eruptions and hot springs, according to scientists, is about 8.4 .   1017 to 31.5 . 1018 j  in year.

The thermal energy of volcanoes has long been used in Iceland, a country of perpetual ice that does not have fuel reserves. Also this is the cheapest energy.

Hot volcanic water is widely used in Japan. It is heated at home, the soil is warming in rice fields and vegetable gardens, and due to the considerable 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 is established that the hot waters of many sources of Kamchatka and the Kuril Islands are not inferior to the mineral waters of the famous resorts for their balneological properties. So, in Kamchatka, the waters of the Nalachev 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.

The current activity of volcanoes is accompanied by the formation of a number of mineral deposits, some of which appear in the eyes of a person. For example, gas streams emitted from the depths are so saturated with sulfur dioxide and hydrogen sulphide that sulfuric mounds emerge on the surface. FROM active volcanoes  The formation of ammonia, boric acid and other chemical compounds is also associated.

In ancient volcanoes, whose volcanic structures are more or less destroyed and under which there are no longer lava foci, another complex of minerals is encountered. Basically, these are metal ores, including mercury, silver, antimony, etc., sulfur deposits and, of course, lavas themselves construction material. With underwater eruptions, deposits of Iceland spar (a valuable material for the manufacture of optical instruments), and sometimes manganese and iron, occur.

With a special type of magmatic activity at great depths (due to its explosive nature adjacent to volcanic phenomena), the formation of a diamond is associated.

All that we have learned about volcanoes suggests that their activities can be used in a variety of ways. Moreover, in some cases, these opportunities are completely unexpected. For example, the researchers of the Sahara raised the issue of using extinct volcanoes for ... increasing the number of falling rains. At first glance, the proposal seems simply strange. However, there is a link between rain and volcanic activity in the Sahara. The thing is that in the recent past, in a desert climate in the Sahara volcanoes operated, and then in these parts there were many lakes. Therefore, it is assumed that the sharp decrease in humidity observed at the present time 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 abundant precipitation. Hence the natural conclusion about the possibility of humidifying the climate by artificially resuming the activity of extinct volcanoes, for example, using atomic energy.

6.5. Volcanic activity on the Moon

More recently (with the beginning of space exploration) it became known that volcanism is a cosmic phenomenon that is inherent in all the planets of the solar system. Most of all we know about the volcanism of the Moon. On the visible side of the Moon, there are 517 large and many smaller craters.

On the night of November 3, 1958, Soviet astronomers NA Kozyrev and VE Ezersky recorded the eruption of volcanic gases from one of the lunar craters. Later, they also discovered fumarolic ("fumo" -dym) activity in yet another crater. This shows that the volcanoes on the Moon continue to act now.

7. Scientific methods and means of research

One of the methods of scientific research is photogrammetry. Photogrammetry is traditionally divided into two main directions: 1 - ground photogrammetry (phototopography); 2 - aerial photogrammetry (aerial photography, aerial photogeodesy) and involves the study of objects and phenomena from their photographic images obtained by specialized cameras (phototiodolites, aerial cameras, etc.) from points on the earth's surface or with the use of aircraft.

Recent decades have seen rapid development of new methods of photogrammetry, based on the ability to visualize the results of remote studies performed outside the visible range of the electromagnetic spectrum. Some of the new areas of 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 are known to be the main obstacle for studying the volcanoes of Kamchatka and the Kuriles in the visible range. Photogrammetry of infrared (IR) images obtained with the help of modern thermal imagers and thermal IR scanners could provide important additional materials for studying volcanic eruptions and their precursors. But at the Institute of Volcanology of the Far Eastern Branch of the Russian Academy of Sciences, the methods of traditional photogrammetry were the most developed and applied, and only because the instruments, instruments and technologies of research in this direction were the most accessible. The precise geometric characteristics and dynamic parameters of volcanic eruptions, determined by the methods of photogrammetry, allow us to judge objectively the nature and scale of the events occurring, contribute to a correct understanding of the mechanism of eruptions.

And in the complex of volcanological studies used at the VIC "Vulkanologist" in studying the underwater volcanoes of the Kuril island arc, echo sounding, hydromagnetic sampling (HMS), sampling of bottom sediments, etc. were included as mandatory methods. In a number of flights, continuous gas hydrochemical profiling and hydrochemical studies.

When carrying out geophysical studies, a single service of ship time was used. It allowed to synchronize the work of various measuring instruments and to bring the results of measurements to the single coordinates of time and space.

There are many more methods for studying volcanoes, but we will not go into details, because this is not the main theme of the work.

8. Links to other problems and tasks

After the accumulation of extensive knowledge and the development of special methods for studying volcanoes, an independent science of volcanology arose. Volcanology is closely related to such sciences as geology, petrography, mineralogy, geochemistry, hydrogeology, geophysics, thermodynamics and, in part, astronomy.

In volcanology, exact calculations and experiments are increasingly being used, and it therefore turns into an exact science before our very eyes. And if before the collections of articles of volcanologists to some extent represented, in the words of one scientist - nevulcanologist, "magazines illustrated by smoke clubs", now they have a big role in the precise research based on the data of physical chemistry, geophysics, mathematical calculations , modeling of volcanic phenomena, etc.

Volcanology developed a new direction, called "volcano-physics," - a quantitative study of eruptive phenomena, the study of deep parts of volcanic apparatus by geophysical methods, the establishment of the connection of external volcanic phenomena with processes at great depths.

Volcanologists have adopted the achievements of modern technology. In the crater of the Avachinsky volcano, automatic sensors are installed, which record the temperature of the volcano. Thanks to them, Kamchatka volcanologists can, without getting up to the crater, constantly monitor how the volcano "feels" itself. To replace the aqualungs come underwater vessels and bathyscaphes, giving the opportunity for a long time and at great depth to study the manifestations of underwater volcanism.

9. Place the topic in the curricula and topics of the GEF

This topic is studied a little in the first year of the GGF. And also for masters are taught a course of paleovolcanology (Litasov Yu.D., 36 hours). Paleovulcanology -   The branch of geology that studies the volcanic activity of past geological epochs. The main subject of paleovolcanology consists of ancient volcanic structures (calderas, remains of volcanic shields, etc.) and their roots (according to which magma rose to the earth's surface), leaving deep into the Earth and, unlike modern volcanoes, accessible for direct study on erosion sections of ancient folded structures.

10. Conclusion

No matter how improbable it sounded, but I liked writing this term paper.

I do not even know whether I succeeded in generalizing the received knowledge and whether I "told" everything that was supposed under this topic. I hope so. But I definitely achieved my goal, I learned a lot about the volcanoes, which I did not even know about. For example, that on the moon there are craters known to everyone, but that they also erupt, I did not know. That the volcanic activity can be influenced by cosmic forces. And much more.

Difficulties in doing the work consisted of a lack of time (it would be more time, one could better formulate their thoughts and ideas) and that in the library of the NSU books on this topic were presented in one or two copies and had already been dismantled before me , so most of the books were taken in the JIIGM SB RAS.

11.List of Literature

3) Gushchenko I.I. Eruption of the volcanoes of the world. -M .: Science, 1979. (302 pages)

4) Lebedinsky VI Volcanoes are a formidable phenomenon of nature. -M .: Academy of Sciences of the Ukrainian SSR, 1963. (108 pages)

5) Lebedinsky VI Volcanoes and people. -M .: Nedra, 1967 (204 pages)

(from Latin fluidus - flowing) - .. 1) liquid and gaseous easily moving components of magma or solutions circulating in terrestrial depths saturated with gases. It is assumed that the composition of the fluids is dominated by superheated water vapor, fluorine, chlorine, carbon dioxide and many other substances are present ...