Volcanoes and types of volcanic eruptions presentation. Presentation "Volcanoes". Scheme of the structure of the stratovolcano

Depending on the amount of gases, their composition and temperature, three main forms of eruptions are distinguished: effusive, explosive and extrusive.

If gases are released from the magma relatively calmly, an outpouring occurs - lava effusion.

When gases separate quickly, instantaneous boiling of the melt occurs and the magma bursts with expanding gases.

bubbles causing a powerful explosive eruption - explosion.

If the magma is viscous and its temperature is low, then

the melt is slowly squeezed onto the surface -

magma extrusion.

Types of volcanoes

The Hawaiian type is a very liquid, highly mobile basaltic lava that forms huge flat shield volcanoes. There are no explosions. Lava lakes are frequent, gushing to heights of hundreds of meters. Lava flows spread over tens of kilometers.

Strombolian type - a more viscous basic lava, which is ejected by explosions from the vent, forming relatively short and more powerful flows. The Stromboli volcano regularly throws a “charge” of bombs and pieces of hot slag into the air.

Fissure (A) and

panel central (B) types

Stratovolcano

Scheme of the structure of the stratovolcano

1 - caldera at the top, 2 - summit cone, 3 - side lava volcanoes, 4 - extrusive cone on a slope, 5-

main volcanic cone with alternating lava flows and tuff covers, 6 - earlier acidic tuffs in a volcanotectonic basin, 7 - peripheral magma chamber.

Types of volcanoes

The Plinian type (Vesuvian) eruption was named after the Roman scientist Pliny the Elder, who died in the eruption of Vesuvius in 79 AD. e., which destroyed three big cities- Herculaneum, Stabia and Pompeii.

Powerful, often sudden explosions are accompanied by the release of huge amounts of tephra, forming ash and pumice flows. Pompeii and Stabia were buried under tephra, and Herculaneum was littered with mud-stone flows.

As a result of the explosions, the magma chamber was empty, the top part of Vesuvius collapsed and a caldera was formed, in which a hundred years later a new volcanic cone - modern Vesuvius.

Types of volcanoes

Plinian eruptions are very dangerous and occur suddenly, often without any preliminary preparation.

The grandiose explosion in 1883 of the Krakatoa volcano in the Sunda Strait between the islands of Sumatra and Java belongs to the same type. The sound was heard at a distance of up to 5000 km, and volcanic ash reached almost a hundred kilometers altitude. The eruption was accompanied by a tsunami in 25-40 m, in which about 40,000 people died in coastal areas. A giant caldera formed on the site of the Krakatoa group of islands.

Formation of lakes in calderas

Types of volcanoes

Peleian type - the formation of enormous hot avalanches or scorching clouds, as well as the growth of extrusive domes of extremely viscous lava.

On the Mont Pelee volcano ( Martinique Island, Lesser Antilles) On May 8, 1902, the top of a dormant volcano was destroyed by an explosion. A giant heavy “scorching” cloud bursting out of the crater instantly destroyed the city of Saint-Pierre with 40,000 inhabitants. It consisted of a suspension in the hot air of hot fragments of ash, pumice, crystals, and volcanic rocks. Possessing high density, the cloud rushed down the slope of the volcano at high speed.

After the eruption, an extrusive “needle” of viscous magma began to emerge from the vent, which, having reached a height of 300 m, soon collapsed.

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 clouds of ash, they argued, were smoke from his forge, and the splashes of lava were sparks from his anvil. They called this island "Vulcano" - from the Latin word "Volcano".


Vulcan (Greek - Hephaestus). In Greek and Roman mythology, he is the god of fire and a blacksmith who forged weapons for many gods and heroes. He was a teacher ancient man and taught him 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 The mouth of Vesuvius opened the smoke, a cloud of flames gushed out, It developed widely, like a battle flag. The earth is shaking from the shaky columns. Idols are falling! The people, driven by fear, in crowds, old and young, under the inflamed dust, under the rain of stones, flee from the city. A.S. Pushkin VOLCANOES Are silent extinct volcanoes, ash falls to the bottom. Giants rest there after committing evil. B. Akhmadulina Volcanoes are blown up. The Ocean is defeated... Arthur Rimbaud




The structure of a volcano A typical volcano is a hill with a pipe running through its thickness, called a volcano vent, and a magma chamber (an area where magma accumulates) from which the vent rises. When high pressure is created in a magma chamber, a mixture of magma and hard rocks - lava - rises up the vent and is thrown into the air. This phenomenon is called a volcanic eruption.












Ash is the finest volcanic product, having the appearance of a powdery mass. During explosive eruptions, it is thrown onto the surface of the earth with a volume often of many cubic kilometers and rises in the form of a cloud cloud to a height of several tens of kilometers. Thick deposits of ash, covering the slopes and foothills of volcanoes in layers of many meters, destroy large forests and even cities. Ash is the finest volcanic product, having the appearance of a powdery mass. During explosive eruptions, it is thrown onto the surface of the earth with a volume often of many cubic kilometers and rises in the form of a cloud cloud to a height of several tens of kilometers. Thick deposits of ash, covering the slopes and foothills of volcanoes in layers of many meters, destroy large forests and even cities.


On the left, on the right - bombs like bread crusts, in the middle - in the form of a spindle. Volcanic bombs have an unusually wide variety of shapes and sizes among fragmental material. 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 volcanoes are those that are currently erupting or erupting periodically, at certain intervals. If magma does not pour out, but the volcano “smoke” or “smokes,” then it is also considered active. Dormant Volcanoes are considered to have fallen asleep if they were active during a historical period of time and have retained their shape; weak tremors and earthquakes periodically occur in their depths. Extinct Extinct are volcanoes that were active once in the distant past; they have blurred and destroyed cones




Hawaiian type On the main island of Hawaii is Mauna Loa volcano. Its characteristic feature is that basaltic melts flow here relatively calmly, without explosions. The melt is weakly saturated with gases and has low viscosity, although unusually spectacular lava fountains sometimes appear. As a result of such an eruption, the volcano has very gentle slopes on which several craters are located.


Stromboli type Although the melt here is basaltic, that is, it has a basic composition, it has some viscosity. Therefore, there is an alternation of outpourings of lava flows and explosions. Explosions release bombs, lapilli, ash and basalt slag. Stromboli - a volcano of the Aeolian Islands - is notable for the fact that it is constantly active, being a unique, unusually bright beacon Mediterranean Sea


Type Vulcano The volcano of the island of Vulcano, located in the Aeolian Islands, is also very famous. It is characterized by the eruption of relatively acidic volcanic products (andesite-dacite). Due to the high viscosity of the melt, the volcano's crater becomes clogged. The accumulated vapors and gases explode this plug and, together with other finely crushed particles various forms and sizes throw them to great heights. That's what they often say: Vulcan-type explosive eruptions.


Vesuvian type Named by name famous volcano Vesuvius, located in Italy, near Naples. The ancient Roman scientist Pliny the Younger described it very colorfully, and therefore this type of eruption is often called Plinian. This type is characterized by strong explosive eruptions due to periodic blockage of the volcano's vent, as well as the subsequent outpouring of lava flows.


Pompeii disappeared under a 7-8 meter layer of ash and rubble, which continuously 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 start of the eruption, the sun appeared for the first time, illuminating three dead city. On August 24, 1979, people paid with their lives for their carelessness: suddenly in the blue sky above Gulf of Naples a lava plug shot up, tightly plugging the mouth of the Vesuvius crater for many millennia.




The inhabitants of Pompeii, buried under the ash, died of suffocation. However, the caverns in the layer of hardened ash, where their bodies had previously been located, retained the shape and posture of the unfortunates for many years. When these caverns were filled with gypsum mortar, people saw sculptural images of the dead. Cast of a suffocating woman, preserved in ashes Sculptural images of the dead Cast of a dog


Pelée type The Mont Pelée (Bald Mountain) volcano, which gives its name to the next type of eruption, is located on the island of Martinique (Less Antilles V Atlantic Ocean). It is characterized by hot ash clouds and the growth of domes in the crater of the volcano. For the first time, a directed explosion was observed here, covering a large area.






An "active" volcano is a volcano that is erupting recent years Most of the Earth's active volcanoes are located in only a few countries












The large fissure Tolbachik eruption is considered one of the largest known basaltic eruptions in the Kuril-Kamchatka belt. The eruption lasted almost a year and a half (July December 1976). The height of the jet of hot gases reached a height of 2.5 km, and the ash cloud reached 12 km. As a result of the eruption, 4 cones of the New Tolbachin volcanoes were formed, and the huge forested area around them turned into a scorched desert. Over the years that have passed since then, the cones have not had time to cool completely, so standing at the top of the cone, you feel the heat coming from below. The ash desert is gradually being reclaimed 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 arose when eruption centers moved along cracks; volcanic ridges that arose when eruption centers moved along cracks; calderacaldera volcanoes; volcanoes with sommavolcanoes with somma that arose within calderas after their renewal; dome volcanoes.


Underwater volcanic activity Guyots Guyots [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 Pacific Ocean. There are also some G. in the Atlantic and Indian Oceans. The mountain peaks are located at depths from 200 to 2000 m. It is believed that the leveling of the mountain peaks is the result of abrasion. Since abrasion affects only to a depth of about m, it is assumed that most of the mountains experienced subsidence along with the ocean floor that forms 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 chemicals. Volcanic material - pumice - is included in some toothpastes. Sapphires, zircons, copper, silver, gold - all this can be mined from volcanic rocks. Some of the largest diamonds were also found in them.


Volcanoes of the Universe Nameless volcano in the area north pole Io (moon of Jupiter). Galileo (an artificial probe) photographed the eruption of this volcano; a column of dust rose to a height of about 430 km. An even higher column of ash and dust was also spotted - rising to a height of more than 480 km. Using the equipment installed on Galileo, it was possible to determine the composition of the volcanic ejecta. These were particles that resembled snowflakes, made up of sulfur dioxide molecules.


Technological map Task 1

I want to know


What is a volcano ?

  • Volcano- (from Latin vulcanus - fire, flame), a conical mountain from the neck of which hot gases, steam, ash, debris are emitted rocks, as well as powerful streams of hot lava that spread over the surface of the earth.
  • A volcano is a geological formation on the surface of the earth’s crust or the crust of another planet, where magma comes to the surface, forming lava, volcanic gases, and stones.
  • Volcanoes are conical mountains formed by the products of their eruptions.

Technological map Task 2.

Volcano is…………………………………………………………………………………...

…………………………………………………………………………………………………… ...

………………………………………………………………………………………………… .....



Structure of the volcano

  • A magma chamber is a place under the earth's crust,

where magma collects.

  • A volcanic vent is a channel through which magma rises.
  • A volcano crater is a bowl-shaped depression at the top of a mountain.
  • Lava is erupted magma.

Technological map Task 3 Complete the diagram "Structure of a volcano"



Eruption- this is the release of molten matter from the Earth’s crust and mantle to the surface of the planet, called magma .



Historical catastrophe of volcanic origin

K. Bryullov “The Last Day of Pompeii”





Causes of volcanic eruptions

Earthquake;

Pressure drop in the magma chamber. And with a sudden decrease in pressure, the magma melts, the gases expand and rush out.


Signs of a volcanic eruption

Almost always a volcanic eruption can be predicted. The most characteristic signs of the “awakening” of a volcano are:

  • - increased release of gases and

mineral waters on it

  • - temperature increase;
  • - underground hum.

Types of volcanic eruptions

If gases are released from the magma relatively calmly, then it flows to the surface, forming lava flows. This eruption was called effusive.


If gases are released quickly, an instantaneous boiling of the magmatic melt occurs and it bursts with expanding gas bubbles.

Something powerful is happening.

explosive eruption

which received

Name explosive.


If the magma is very viscous and its temperature is low, then it is slowly squeezed out to the surface. Such an eruption is called extrusive.


Types of volcanoes

Most common central type volcanoes is a hill, mountain or hill with a depression at the top – crater , from which magma comes to the surface. Ejected during a volcanic eruption

rock fragments from it,

ash, poured lava

remain on its slopes.

The height of the mountain increases -

Xia, and with it the crater

moves higher and higher


Another type of volcano is linear or fissure . Their occurrence is associated with the rise of liquid basaltic magma along a crack in the earth's crust. Liquid lava spreads over vast areas, forming lava sheets. Such a volcano looks like a crack on the surface of the Earth.



Active volcanoes

Krakatoa

Fujiyama

Klyuchevskaya Sopka


Extinct volcanoes

Kilimanjaro




TEST

1. Geological formation that appears above channels and cracks in the earth’s crust, through which ash, lava, hot gases, water vapor, and rock fragments are erupted onto the earth’s surface

a) earthquake

b) seaquake

c) volcano

2. The word “volcano” comes from the name of the ancient Roman god:

a) the underworld

3.Find two reasons for a volcanic eruption

a) flood

b) earthquake

c) pressure drop in the magma chamber

d) tsunami

4. Find three signs of a volcanic eruption

a) increased release of gases and mineral waters;

b) increase in temperature;

c) underground hum.

d) decrease in temperature

5. Choose the wrong classification of volcanoes a) by shape b) by the amount of erupted lava c) by activity

d) by location

Answers to the test

3 - b, c

4 - a, b, c


Homework

Chapter 2, paragraph 5, tasks from the technological map Creative task:

(by choice and desire)

make a model of a volcano;

make a selection of facts about the volcanic eruption

  • 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 among people, and the tragic consequences of eruptions forced them to study this element.
  • Volcano formation
  • When a magma chamber forms in the depths of the Earth, molten liquid magma presses from below on the tectonic plate with such force that it begins to crack. Magma rushes upward along cracks and faults, melting the rock and widening the cracks. This creates an exit channel. It passes through the center of the volcano, through which molten magma pours out from the crater of the volcano out in the form of fiery liquid lava. The products of the eruption - pumice, lava, tuffs - 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 crater of the volcano - the opening of the outlet channel through which ash, hot gases and water vapor, lava and rock fragments erupt. Volcano vents can be gaping, empty, or filled with molten lava. If lava hardens in a crater, a solid plug is formed, which can only be broken through by a strong volcanic eruption, resulting in a powerful explosion.
  • Types of volcanoes
  • Active volcanoes
  • Volcanoes spew out molten rock, ash, gases, and rocks from time to time. This happens because deep below them there is a magma chamber, similar to a huge furnace in which rock melts, turning into fiery liquid lava.
  • Those volcanoes are also considered active if there is any evidence of eruptions in human history.
  • Extinct volcanoes
  • Inactive volcanoes were active only in prehistoric times. The hearth beneath them has long gone out, and they themselves are so badly destroyed that only geological research reveals traces of ancient volcanic activity.
  • Dormant volcanoes
  • Dormant volcanoes have not erupted in historical times, but a catastrophic eruption may begin at any moment, because the magma chamber beneath them has not gone 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 gush out. The longer a dormant volcano remains dormant, the more dangerous it is: the power of its explosive awakening can be catastrophic.
  • Types of eruptions
  • Explosive eruptions
  • A volcano explosion occurs when volcanic gases are released from thick magma. During such eruptions, mountain tops are destroyed and millions of tons of ash are thrown into the sky to great heights.
  • Ash, gases and steam rise tens of kilometers into the sky in the form of curly clouds.
  • Effusive eruptions
  • During an effusive volcanic eruption, liquid lava flows freely to form lava flows and sheets
  • Extrusive eruptions
  • Ejected from the crater of a volcano great amount burning gases and hot lava dust. Spreading around the volcano with tremendous speed, this scorching cloud burns everything over a very large area with lightning speed.
  • Eruption products
  • Everything that comes out of the bowels of the Earth during volcanic eruptions is called eruption products.
  • They are liquid, solid and gaseous.
  • The liquid products of an eruption include lava.
  • Lava- this is magma that spills onto the surface of the earth
  • Types of lava flow.
  • It has a smooth or slightly wrinkled surface and is composed of liquid lava. When hardened, such lava forms a flat, smooth surface, sometimes with long wriggling wrinkles in the form of snakes and thick ropes. It is often called “rope lava.”
  • It 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 had time to cool. The upper hardened layer of lava resembles piles of slag, which is formed from the combustion of coal.
  • Lava flow "ah-ah"
  • Pa-hoe-hoe lava flow
  • Pyroclasts
  • Rock fragments that are thrown out 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 freely and do not threaten explosions. Gases can foam even viscous magma, forming porous pumice, disperse 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 crater of a volcano hundreds of meters away.
  • Volcanoes in Kamchatka
  • Bezymyanny Volcano
  • Bezymyanny volcano is located near Klyuchevaya Sopka. It was considered extinct, and the power of its awakening was gigantic. On March 30, 1956, a terrible explosion destroyed the entire upper part of the volcano. Clouds of ash shot up almost 40 km, from
  • From the vent, a powerful stream of hot gas, volcanic sand and ash burst out, 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 within a radius of 45 km from the volcano during the hours of the eruption.
  • Tolbachinskaya Sopka
  • Volcano Tolbachik - very active volcano. At its peak, 3085 m high, there was a huge caldera with a crater 300 m in diameter and 150 meters deep. From time to time there appeared in the crater small lake hot lava. In 1975-1976, an Icelandic-type fissure eruption occurred. It lasted continuously for 520 days.
  • For very a short time Many cracks more than a kilometer long 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 death of 2,000 people when huge amounts of lava were ejected from its crater.
  • Volcano Mayon
  • Mayon's longest eruption occurred in 1897. It lasted from June 23 to June 30 and claimed 400 lives.
  • Volcanoes of the Mediterranean
  • Volcano Stromboli
  • In the south of Italy, near the island of Vulcano. Located volcano island Stromboli. He has a very restless character, and he has been acting for several millennia almost without interruption. From time to time, explosions occur in its crater, and hot slag and volcanic bombs fly up 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 since the fifteenth century there have already been 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 a height of 818 m and a length of 25 km.
  • June 8, 1783.
  • Not far from the town of Vatnajo-kull in the southeast of Iceland, a powerful eruption of the Laki volcano began. It lasted 8 months, the length of the flow of lava that came to light 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.
  • Volcano Laki
  • Volcanoes of Africa
  • Mount Kilimanjaro
  • Kilimanjaro is volcanic mountain range in east Africa
  • The massif consists of three peaks - Kibo, Mawenzi and Shira. The Mawenzi and Shira volcanoes have long been extinct, and Kibo continues to smoke volcanic gases through openings on the slopes.
  • Volcanoes of the Pacific Ocean
  • Mount St. Helens
  • IN North America, in the Cordillera, Mount St. Helens is perhaps the lowest among 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 claimed the lives of 62 people.
Working with a geographic map
  • Show the following volcanoes on the map:
  • Nameless, Tolbachik Sopka, Mayon, Stromboli, Lucky, Kilimanjaro, St. Helens
  • Show on the map the volcanoes that erupted in the last year
  • Questions about the material covered
  • 1.What types of volcanoes are there?
  • 3.What types of eruptions do you know?
  • 5.What are the products of the eruption?
  • 2.How are volcanoes formed?

 

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