History of the name About 20 centuries ago, a mountainous island in the Mediterranean Sea near Sicily began to spew smoke and fire. Explaining this strange phenomenon, people believed that the forge of the Roman god Vulcan was located in the mountain. The ash clouds, they argued, were smoke from his forge, and the lava spray were sparks from an anvil. They called this islet "Vulcano" - from the Latin word "Volcano".
Volcano (Greek - Hephaestus). In Greek and Roman mythology, the fire god and blacksmith who forged weapons for many gods and heroes. He was a tutor ancient man and taught him how to use fire. He was lame from birth or as a result of being thrown from Olympus to earth by Jupiter in a fit of rage.
Poets about volcanoes Vesuvius mouth opened the smoke poured out in a club flame Widely developed like a battle banner. The earth is agitated from the staggering columns Idols are falling! The people, driven by fear, Crowds, old and young, under the inflamed ashes, Under the stone rain, flees out of the hail. A.S. Pushkin VOLCANOES The extinct volcanoes are silent, ash falls to their bottom. There the giants rest after the evil they have done. B. Akhmadulina Volcanoes are blown up. Defeated Ocean ... Arthur Rimbaud
The structure of the volcano A typical volcano is a hill with a pipe passing through its thickness, called a volcano vent, and with a magma chamber (an area of magma accumulation) from which the vent rises. When a high pressure is created in the magma chamber, a mixture of magma and hard stones - lava - rises up the vent and is thrown into the air. This phenomenon is called a volcanic eruption.
Ash is the smallest volcanic product in the form of a powdery mass. During explosive eruptions, it is thrown onto the earth's surface with a volume of often many cubic kilometers and rises in the form of a cloudy cloud to a height of several tens of kilometers. Powerful ash deposits covering the slopes and foothills of volcanoes in a multi-meter layer are destroying large forests and even cities. Ash is the smallest volcanic product in the form of a powdery mass. During explosive eruptions, it is thrown onto the earth's surface with a volume of often many cubic kilometers and rises in the form of a cloudy cloud to a height of several tens of kilometers. Powerful ash deposits covering the slopes and foothills of volcanoes in a multi-meter layer are destroying large forests and even cities.
Left, right - bombs like a bread crust, in the middle - in the form of a spindle. Volcanic bombs have an unusually wide variety of shapes and sizes among debris. They are formed from pieces of lava raised to a certain height by gases that are intensely released from the hot melt.
Volcanoes are divided into: Active Active - these are those volcanoes that are currently erupting or are observed periodically, at some intervals of time. If magma does not pour out, and the volcano "smokes" or "smokes", then it is also considered active. Asleep Volcanoes are considered to be asleep, which manifested their activity in a historical period of time and retained their shape; weak tremors and earthquakes periodically occur in their depths. Extinct Extinct - volcanoes that operated in the distant past; they have blurry and destroyed cones
Hawaiian type On the main island of Hawaii is the Mauna Loa volcano. Its characteristic feature is that basaltic melts pour out here relatively calmly, without explosions. The melt is weakly saturated with gases and has a low viscosity, although unusually spectacular lava fountains sometimes occur. As a result of such an eruption, the volcano has very gentle slopes, on which there are several craters.
Stromboli type Although the melt here is basaltic, that is, it has a basic composition, it has a certain viscosity. Therefore, there is an alternation of outpouring of lava flows and explosions. Explosions release bombs, lapilli, ash and basalt slag. Stromboli - the volcano of the Aeolian Islands - is notable for the fact that it constantly operates, being a kind, unusually bright lighthouse Mediterranean Sea
Volcano type The volcano of the island of Vulcano, located in the Aeolian Islands, is also quite famous. It is characterized by an eruption of relatively acidic volcanic products (andesite-dacites). Due to the high viscosity of the melt, clogging of the vent of the volcano occurs. The accumulated vapors and gases explode this plug and, together with other finely crushed particles of various shapes and sizes, throw them out to a great height. This is what they often say: explosive eruptions of the Vulcan type.
Vesuvian type Named by name famous volcano Vesuvius, located in Italy, near Naples. The ancient Roman scientist Pliny the Younger described it very colorfully, in connection with which this type of eruption is often called Plinian. This type is characterized by strong explosive eruptions due to periodic blockage of the volcanic vent, as well as the subsequent outpouring of lava flows.
Pompeii disappeared under a 7-8 meter layer of ash and rubble, which continually fell on the streets and houses. Herculaneum was flooded with hot lava and boiling mud. Stabia was almost completely destroyed. Only on August 27, three days after the beginning of the eruption, the sun first glimpsed, illuminating three dead city... August 24, 79 g people paid with their lives for their carelessness: suddenly into the blue sky above Gulf of Naples a lava plug shot up, for many millennia tightly plugging the mouth of the Vesuvius crater.
The inhabitants of Pompeii, buried under the ashes, died of suffocation. However, the caverns in the layer of solidified ash, where their bodies had previously been, retained the shape and postures of the unfortunate for many years. When these caverns were filled with plaster mortar, people saw sculptures of the dead. Cast of a suffocating woman, preserved in the ashes Sculptures of the deceased Cast of a dog
Pele type The Mont Pele volcano (Bald Mountain), which gave the name to the next type of eruption, is located on the island of Martinique (the Small Antilles v Atlantic Ocean). It is characterized by incandescent ash clouds and the growth of domes in the crater of the volcano. For the first time, a directional explosion was observed here, covering a large area.
An "active" volcano is an erupting volcano recent years Most of the Earth's active volcanoes are found in only a few countries.
The large fissure Tolbachik eruption is referred to as the largest known basaltic eruption in the Kuril-Kamchatka belt. The eruption lasted for almost a year and a half (July December 1976). The height of the jet of incandescent gases reached a height of 2.5 km, and an ash cloud - 12 km. As a result of the eruption, 4 cones of the New Tolbachik volcanoes were formed, and the vast forested area around them turned into a scorched desert. Over the years that have passed since then, the cones did not have time to cool down to the end, so when you stand not at the top of the cone, you feel the heat coming from the bottom. The ash desert is gradually being developed by lichens, dwarf willow and other pioneer plants.
The following morphological types of volcanoes are distinguished: cone-shaped - the result of frequent eruptions without strong explosions; shield, flat volcanoes - devices for the outpouring of liquid lavas volcanic ridges that have arisen when the outflow centers move along the cracks; volcanic ridges that have arisen when the outflow centers move along the cracks; caldera caldera volcanoes; volcanoes from the somma volcanoes from the somma that arose within the calderas after their renewal; dome volcanoes.
Guyot Guyot's underwater volcanic activity [named after the discoverer of the American geographer and geologist A. Guyot (Guyot; A. Guyot;)], isolated flat-topped volcanic seamounts. They are found in groups or in the form of single uplifts, mainly in the Pacific Ocean. Separate G. are also found in the Atlantic and Indian oceans. The peaks of G. are located at depths from 200 to 2000 m. It is believed that the alignment of the peaks of G. is the result of abrasion. Since abrasion affects only up to a depth of the order of m, it is assumed that the majority of G. experienced subsidence together with the oceanic bottom forming their base.
Volcanoes are very dangerous, but they also bring benefits to humans. Various igneous rocks are used as building materials and abrasives. The sulfur released by the volcano is part of many useful chemical substances... A volcanic material called pumice is found in some toothpastes. Sapphires, zircons, copper, silver, gold - all of these can be mined from volcanic rocks. Some of the largest diamonds were also found in them.
Volcanoes of the Universe A nameless volcano near the north pole of Io (moon of Jupiter). Galileo (artificial probe) photographed the eruption of this volcano, the dust column rose to an altitude of about 430 km. An even higher column of ash and dust was also seen - it rose to an altitude of more than 480 km. With the help of the equipment installed on the Galileo, it was possible to determine the composition of the volcanic outburst. They were snowflake-like particles composed of sulfur dioxide molecules.
geological formation arising above channels and cracks in earth crust, according to which on earth surface molten rocks (lava), hot gases, ash, water vapor and rock debris erupt
The main parts of the volcano
At the top of the volcano there is a deep depression - a crater. A vent goes into the crater - a channel through which liquid magma rises from the bowels of the Earth.
Types of volcanoes:
Active
- central volcanoes
- linear volcanoes
- Active volcano Etna
- Dormant Parinacota Volcano
Volcanoes are: active, dormant, extinct .
- Extinct Mount Fuji
- There are about 500 volcanoes on Earth. About 370 of them are located on the shores and island arcs The Pacific(Aleutian, Kuril, Japanese, Filipino, Sunda Islands) and on the outskirts of the continents of North America, Central America, in the Andes in the west South America. 9 active volcanoes are located in Antarctica. Several volcanic islands are found in Indian Ocean... There are only 45 of them in the Atlantic Ocean.
Volcanoes in Russia.
In Russia, Kamchatka, Kuriles and Sakhalin are at risk of volcanic eruptions. There are extinct volcanoes in the Caucasus.
- Hot lava flows (their speed is up to 100 km / h)
- Scorching avalanches (consisting of blocks, sand, ash and volcanic gases with a temperature of 700 degrees C)
- Clouds of ash and gases (thrown to a height of 15-20 km)
- Blast wave and scattering of debris
- Water and mud-stone flows (travel speed up to 90-100 km / h)
- Sharp climate fluctuations (greenhouse effect can be created)
Actions in the event of a volcanic eruption.
In the event of a volcanic eruption: 1 ) protect sensitive devices; 2) close the drinking water tanks; 3) follow the shelter; 4) periodically it is necessary to go out and sweep the ash from the roofs and shake it off the trees.
Actions in the event of a volcanic eruption in the immediate vicinity
- What are the types of volcano
- List the parts of the volcano
- Actions in the event of a volcanic eruption
Knowledge check
1) Tremors and vibrations of the earth's surface resulting from sudden displacements and ruptures in the earth's crust are called ...
Knowledge check
2. Of the listed consequences, indicate which of them relate to earthquakes:
a) scorching avalanches;
b) sinkholes and rise of the earth's surface;
d) industrial accidents;
f) sharp climate fluctuations;
Knowledge check
3 . Of the listed consequences, indicate which of them relate to volcanoes:
a) sinkholes and rise of the earth's surface;
b) scorching avalanches;
c) destruction of buildings and structures;
d) clouds of ash and gases;
e) blast wave and scatter of debris;
f) sharp climate fluctuations;
g) vibrations, shocks and cracks in the soil.
Knowledge check
4. What not to do during an earthquake:
a) stand near the windows
b) stand in the doorway;
c) hide in a cast iron bath;
d) use the elevator;
e) light matches, candles, use open fire;
f) approach dilapidated houses.
Knowledge check
5. Identify the types of earthquakes by origin:
a) tectonic;
b) active;
c) guided;
d) sleeping;
e) seaquake;
f) landslide.
Knowledge check
6. A geological formation that appears above channels and cracks in the earth's crust, along which molten rocks (lava), hot gases, ash, water vapor and rock debris erupt onto the earth's surface are called ...
Knowledge check
7. Define the types of volcanoes:
a) landslide;
b) active;
c) guided;
d) sleeping;
e) tectonic.
Examination
the answers
Grading criteria
1) Earthquake
20 points-19 points- "5"
18 points-15 points- "4"
14 points-10 points- "3"
Less than 10 points- "2"
- b, d, e, f
- And where
- In the event of a volcanic eruption in the immediate vicinity, protect your respiratory system and follow for cover.
- In 79 A.D. NS. the volcano Vesuvius suddenly awakened, which had not been active in historical time. A terrible catastrophe wiped out the cities of Pompeii, Herculaneum and Stabia from the face of the Earth, almost all of their inhabitants died.
- Volcanic eruptions remind us of the formidable and indomitable forces that are hidden in the bowels of the Earth.
- The mystery of the causes of volcanism has always aroused fear and keen interest in people, and the tragic consequences of eruptions forced them to explore this element.
- Volcano formation
- When a magma chamber forms in the bowels of the Earth, the molten liquid magma presses down on the tectonic plate with such force that it begins to crack. Along cracks and faults, magma rushes upward, melting the rock and expanding the cracks. This is how the excretory canal is formed. It passes in the center of the volcano, through which molten magma pours out from the crater of the volcano in the form of fiery liquid lava. The products of the eruption - pumice, lava, tuff - settle on the slopes of the volcano, forming a cone. At the top of the volcano there is a depression - a crater. At the bottom of the crater, you can see the mouth of the volcano - the opening of the outlet channel through which ash, hot gases and water vapors, lava and rock fragments are spewed out. The vents of the volcano can be gaping - empty or filled with molten lava. If the lava solidifies in the vent, then a solid plug is formed, which can only be pierced by a strong volcanic eruption, and a powerful explosion occurs.
- Types of volcanoes
- Active volcanoes
- Volcanoes occasionally spew molten rock, ash, gases, and rocks. This is because deep below them there is a magma chamber, similar to a huge furnace, in which the rock melts, turning into fiery liquid lava.
- Those volcanoes are also considered active if any evidence of their eruptions has survived in the history of mankind.
- Extinct volcanoes
- Extinct volcanoes were active only in prehistoric times. The hearth under them has long gone extinct, and they themselves are so badly destroyed that only the studies of geologists reveal traces of ancient volcanic activity.
- Dormant volcanoes
- Dormant volcanoes in historical time did not erupt, but at any moment their catastrophic eruption can begin, because the magma chamber under them has not died out. Dormant volcanoes show signs of life: they can smoke - smoke comes from their crater, gases and steam are released from cracks in the mountain, hot springs flow. The longer a dormant volcano is at rest, the more dangerous it is: the power of its explosive awakening can be catastrophic.
- Types of eruptions
- Explosive eruptions
- A volcanic explosion occurs when volcanic gases are released from thick magma. During such eruptions, the tops of the mountains are destroyed and millions of tons of ash are thrown into the sky to a great height.
- Ashes, gases and steam rise into the sky for tens of kilometers in the form of curly clouds.
- Effusive eruptions
- During an effusive volcanic eruption, liquid lava flows freely with the formation of lava flows and sheets
- Extrusive eruptions
- From the crater of the volcano, a huge amount of burning gases and hot lava dust are emitted. Spreading around the volcano with great speed, this scorching cloud instantly burns out everything over a very large area.
- Eruption products
- Everything that comes out of the bowels of the Earth during volcanic eruptions is called products of the eruption.
- They are liquid, solid and gaseous.
- Lava is a liquid eruption product.
- Lava is magma that poured out onto the surface of the earth
- Lava flow types.
- Has a smooth or slightly wrinkled surface and is composed of liquid lava. When solidified, such lava forms a flat, smooth surface, sometimes with long wriggling wrinkles in the form of snakes and thick ropes - ropes. Often it is called “rope lava”.
- Has an uneven surface with cracks. This lava is very thick and viscous, so the flow moves slowly. When the lava begins to cool, it cracks into pieces, but they continue to move like clockwork on the hot lava that has not yet cooled down. The upper solidified layer of lava resembles piles of slag that is formed from the combustion of coal.
- Lava flow "ah-ah"
- Lava flow "pa-hoe-hoe"
- Pyroclasts
- The fragments of rocks that are thrown by gases during volcanic eruptions are called pyroclasts
- Volcanic gases
- Volcanic phenomena are associated with the action of gases. If the magma is very liquid, gases are released unhindered and do not threaten explosions. Gases can foaming even viscous magma, forming porous pumice, pulverizing magma into small particles - volcanic ash and sand - and, combining with them, form a deadly scorching cloud.
- And finally, gases can scatter rock fragments from the volcano's mouth for hundreds of meters.
- Volcanoes in Kamchatka
- Bezymyanny volcano
- The Bezymyanny volcano is located near Klyuchevaya Sopka. He was considered extinct, and the power of his awakening was enormous. On March 30, 1956, a terrible explosion blew away the entire upper part of the volcano. Ash clouds shot up almost 40 km, from
- a powerful jet of hot gas, volcanic sand and ash escaped from the vents, which burned out all the vegetation for 25 km around the volcano. A lava dome began to grow from the craters. Now the base of this dome is 750 m, and the height is 320 m. Fortunately, despite all the fury of the eruption, no one died - not a single living soul was in the hours of the eruption within a radius of 45 km from the volcano.
- Tolbachinskaya Sopka
- Volcano Tolbachik - very active volcano... At its summit, 3085 m high, there was a huge caldera with a crater 300 m in diameter and 150 m deep. From time to time, a small lake of hot lava appeared in the crater. In 1975-1976, a fissure eruption of the Icelandic type occurred. It lasted 520 days continuously.
- In a very short time, many cracks more than a kilometer long were formed. All this was accompanied by the spilling and gushing of lava. During the eruption of Tolbachik, two cubic kilometers of volcanic products were thrown to the surface from the depths of the Earth. This is the largest known volcanic eruption in Kamchatka and the Kuril Islands.
- Volcano in the Philippines
- Mayon volcano, the most active on the island of Luzon. On October 23, 1776, it caused the deaths of 2,000 people when a huge amount of lava was thrown out of its crater.
- Mayon volcano
- The longest eruption of Mayon was observed in 1897. It lasted from 23 to 30 June and claimed 400 lives.
- Volcanoes of the Mediterranean
- Stromboli volcano
- In the south of Italy, near the island of Vulcano. Situated volcano island Stromboli - It has a very restless character and has been active for several millennia with almost no interruption. From time to time, explosions occur in its crater, and hot slag and volcanic bombs fly upward tens, and sometimes hundreds of meters, but lava usually does not flow from it.
- One of the most powerful eruptions of Stromboli was noted in 1930, and at the beginning of the fifteenth century there were already seven of them.
- Volcanoes of the Atlantic
- In the south of Iceland there is a volcanic mountain range Lucky, in which there are more than a hundred cones.
- The ridge reaches 818 m in height and 25 km in length.
- June 8, 1783.
- Not far from the town of Vatnajo-kull in the southeast of Iceland, the most powerful eruption of the Laki volcano began. It lasted 8 months, the length of the flow of the escaped lava was almost 70 kilometers, and the volume of this mass, moving at a speed of over 45 km / h, was equal to 12,000 cubic meters and occupied an area of 579 square kilometers.
- Lucky volcano
- Volcanoes of Africa
- Volcano kilimanjaro
- Kilimanjaro is volcanic mountain range in eastern Africa
- The massif consists of three peaks - Kibo, Mawenzi and Shira. The volcanoes Mawenzi and Shira have long gone extinct, and Kibo continues to smoke with volcanic gases through holes on the slopes.
- Volcanoes of the Pacific Ocean
- Volcano st helens
- V North America, in the Cordilleras, Mount St. Helens is perhaps the lowest among the other peaks - its height is only 2950 meters.
- On March 20, 1980, four powerful tremors shook the area, and on March 27, 47 tremors with a force of up to three points. At noon of the same day, a deafening explosion was heard near the very top.
- This monstrous explosion took the lives of 62 people.
- Show the following volcanoes on the map:
- Bezymyanny, Tolbachinskaya Sopka, Mayon, Stromboli, Lucky, Kilimanjaro, St. Helens
- Show on the map the volcanoes that have erupted over the past year
- Questions about the material covered
- 1. What are the volcanoes?
- 3. What types of eruptions do you know?
- 5. What are the products of the eruption?
- 2.How are volcanoes formed?
- 4. Give brief description each type of eruption.
The study of the features of volcanoes, the phenomenon of volcanism is engaged in volcanologists and geomorphologists.
Structure: hearth, vent, crater. A hearth is a place in the earth's crust or mantle. A vent is a channel through which magma rises. Crater - hole, funnel, bowl on top of a volcano mountain.
Volcanoes are classified by location, shape and activity.
By activity: extinct, dormant, active. This classification is rather arbitrary. The extinct ones have not erupted for over 1000 years: they preserve general form, crater, slopes are subject to changes. Sometimes they are active. Example: Mont Pele in Martinique, Valley of Volcanoes in Buryatia, Kalara volcanoes.
Sleepers are volcanoes in which the likelihood of eruption is higher than that of extinct ones. Some of them are called supervolcanoes - Toba in Sumatra, Taulo in New Zealand, Kamchatka volcanoes.
Active - main object interest of volcanologists, erupt frequently. They are located in the belts of young mountains, where mountain building continues. There is no consensus among scientists on how to accurately classify these geological formations. The most active volcanism: South and Central America, Hawaii, Japan, the Sunda Islands.
They are classified by location: subglacial, terrestrial, underwater. The types are distinguished by shape: dome, cinder cone, thyroid, stratovolcano, complex species.
On the basis of the general structure, formations of the central and linear types are distinguished. The former have a central channel through which lava comes to the surface. The second type is fractured, the channels through which the lava rises have an elongated shape. Scientists distinguish an areal type, but there are no such on Earth, at least in our time. They are believed to have existed when the planet was forming.
The eruption is considered emergency, a disaster. It can be an hour, a month, a year, several years. The consequences of the eruption: the formation of depressions, calderas, geysers, fumaroles. Low mountains and islands may appear. Lakes are formed in the craters.
Types of eruption: Hawaiian (basalt lava comes to the surface, accompanied by smoky clouds, fiery avalanches), hydroexplosive (a lot of steam is released, confined to water bodies).
A mud volcano is a formation, as a result of the activity of which mud, gases, and not magma, come to the surface. Found on the territory of Russia, Central Asia.
The largest formations: San Pedro, Cotopaxi, Ojos del Salado in the Andes, Elbrus in the Caucasus, Fujiyama in Japan, Etna and Vesuvius in Italy, Klyuchevskaya Sopka in Kamchatka.
Fixed not only on Earth. If on other planets Solar system and their companions.
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1.1. The Hawaiian type of eruption is characterized by a low (10, rarely 15) explosive index and represents a calm outpouring of liquid basaltic lava, accompanied by weak explosions. Basalt lava flows with characteristic wavy, rope (pakhoye-lavas) and small-block (aa-lavas) surfaces, interbedded with a small amount of pyroclastic material, occur at an angle of 2-3 °, rarely 5 °. Pyroclastic material is usually ejected in a liquid state, forming shaped bombs (spherical, ellipsoidal, pear-shaped, disk, tape, cylindrical, slag). The formation of slags is characteristic, which in the near-crater part are sintered into agglutinates. The thinnest material produced by explosions is tear-shaped ("Pele's tears") and hair-like ("Pele's hair") debris. It is possible to throw out crystals (crystal pillars) in the form of prepared plagioclase individuals up to 3-5 cm in diameter. The lava temperature is 1200–1100 ° С, the viscosity coefficient is 103–104 poise. 1.1. The Hawaiian type of eruption is characterized by a low (10, rarely 15) explosive index and represents a calm outpouring of liquid basaltic lava, accompanied by weak explosions. Basalt lava flows with characteristic wavy, rope (pakhoye-lavas) and small-block (aa-lavas) surfaces, interbedded with a small amount of pyroclastic material, occur at an angle of 2-3 °, rarely 5 °. Pyroclastic material is usually ejected in a liquid state, forming shaped bombs (spherical, ellipsoidal, pear-shaped, disk, tape, cylindrical, slag). The formation of slags is characteristic, which in the near-crater part are sintered into agglutinates. The thinnest material produced by explosions is tear-shaped ("Pele's tears") and hair-like ("Pele's hair") debris. It is possible to throw out crystals (crystal pillars) in the form of prepared plagioclase individuals up to 3-5 cm in diameter. The lava temperature is 1200–1100 ° С, the viscosity coefficient is 103–104 poise. This type is characteristic of the shield volcanoes of the Hawaiian Islands. Described for the volcanoes Nyiragongo (Africa), Plosky Tolbachik (Kamchatka), and the Southern Outburst BTTI (Kamchatka).
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1.3. The volcanic type of eruption is widespread and is usually combined with the Strombolian type. The composition of volcanic products is andesite and dacitic, less often basaltic andesite and rhyolite. In this type of eruption, heated, but not plastic, explosive material of various sizes is thrown out, and lava flows are rare. Lava flows are usually short with a blocky surface. The boulders are much larger than in the basaltic and basaltic andesite flows of the Strombolian eruptions. Characteristic are peculiar volcanic bombs - of the "bread crust" type, with a smooth, highly fractured surface. Explosive index 60-80 and more. The shape of the fragments is angular, their dimension ranges from silty (0.01 mm) to lumps with a diameter of 1 m and more, but ash (less than 2.0 mm) particles predominate, which are most often represented by angular (acute-angled) fragments of volcanic glass. Slag, as a rule, is absent. The admixture of foreign and resurgent material is more than 10%. 1.3. The volcanic type of eruption is widespread and is usually combined with the Strombolian type. The composition of volcanic products is andesite and dacitic, less often basaltic andesite and rhyolite. In this type of eruption, heated, but not plastic, explosive material of various sizes is thrown out, and lava flows are rare. Lava flows are usually short with a blocky surface. The boulders are much larger than in the basaltic and basaltic andesite flows of the Strombolian eruptions. Characteristic are peculiar volcanic bombs - of the "bread crust" type, with a smooth, highly fractured surface. Explosive index 60-80 and more. The shape of the fragments is angular, their dimension ranges from silty (0.01 mm) to lumps with a diameter of 1 m and more, but ash (less than 2.0 mm) particles predominate, which are most often represented by angular (acute-angled) fragments of volcanic glass. Slag, as a rule, is absent. The admixture of foreign and resurgent material is more than 10%. Ash material during volcano-strombolian explosions rises to a height of up to a few kilometers and, depending on the strength and direction of the wind, covers significant areas near the volcano. The finest material (10-15%), mainly vitroclastic, belongs to the outside of the volcanic edifice and is part of the soil-pyroclastic covers and volcano-terrigenous deposits. The ash of volcanic eruptions is not characterized by a porous, drop-like, melted form of fragments. So for the ash fragments of the Karymsky volcano of the eruptions of 1966, 1979. a shape close to isometric with angular protrusions of crystals was noted, but sharply angular shapes were not observed. According to EF Maleev (1982), the mineral composition of the ash changes as the particle size increases. In large fractions, the amount of crystals is 10-15%, and in small fractions - 40-45%, which is probably due to the separation of volcanic glass and its removal to separate areas. In the ashes, about 10% of resurgent and retroclastic debris, which, after weak explosions, again fell into the crater and, undergoing repeated heating, acquired a red color. The lava temperature is 1050–950 ° С, the viscosity coefficient is 105–106 poise. The prototype is described on the island of Vulcano in the Aeolian Islands group. The volcanic type of eruption is typical for the Avachinsky and Karymsky volcanoes (Kamchatka), widely manifested in combination with the Strombolian type at the Northern Outburst of the BTTI (Kamchatka).
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Slide Description:1.7. The phreatic (Bandaysan, ultravolcanic) type of eruption produces only explosive material in a cold and rarely hot state. A large amount of rock fragments of the basement of the volcano (75-100%) in the absence of juvenile material is characteristic. Phreatic eruptions can partially destroy the volcanic edifice, which leads to the accumulation of huge masses of coarse-detrital material of near-crater facies in the lower parts of the relief. Usually these are complex mixtures of lava and tuff fragments with differently oriented bedding. Explosiveness index 100. Rock debris is emitted by steam due to contact of superheated (thermal) waters with groundwater or when lava sinks in a volcano channel below the groundwater level. 1.7. The phreatic (Bandaysan, ultravolcanic) type of eruption produces only explosive material in a cold and rarely hot state. A large amount of rock fragments of the basement of the volcano (75-100%) in the absence of juvenile material is characteristic. Phreatic eruptions can partially destroy the volcanic edifice, which leads to the accumulation of huge masses of coarse-detrital material of near-crater facies in the lower parts of the relief. Usually these are complex mixtures of lava and tuff fragments with differently oriented bedding. Explosiveness index 100. Rock debris is emitted by steam due to contact of superheated (thermal) waters with groundwater or when lava sinks in a volcano channel below the groundwater level. The peculiarity of phreatic eruptions is a rapid (within several tens of seconds) increase in power, which usually does not decrease until the end of the eruption. The famous French volcanologist Garun Taziev observed in 1976 a similar phenomenon from start to finish (more than 30 minutes) on the Soufriere volcano (Guadeloupe island), thirteen eruptions of which were phreatic. The most famous example of this type is the eruption of the Bandai-San volcano (Japan, 1888). Phreatic explosions are also possible when lava flows enter the glaciers covering the slopes of stratovolcanoes. Thus, in July 1993, during the eruption of Klyuchevskoy volcano, the introduction of a lava flow into the Erman glacier was accompanied by a series of powerful phreatic explosions, which reached an altitude of 2-3 km (Fedotov et al., 1995). The above classification is clear, but is applicable mainly to simple eruptions. Complex eruptions can be characterized by several types of activity simultaneously. At the same time, they are so intertwined with each other that it can be difficult to break eruptions into segments with a certain type of activity. Thus, the unique Great Fissure Tolbachik eruption in Kamchatka (1975-1976) was characterized by the manifestation of elements of almost all types of activity: Vulcan, Strombolian, Peleian, Plinian and Hawaiian.
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