What does lava do. civil protection

Origin of lava

Lava is formed when a volcano erupts magma on the Earth's surface. Due to cooling and interaction with the gases that make up the atmosphere, magma changes its properties, forming lava. Many volcanic island arcs are associated with deep fault systems. Earthquake centers are located approximately at a depth of up to 700 km from the level earth's surface, that is, volcanic material comes from the upper mantle. On island arcs, it often has an andesitic composition, and since andesites are similar in composition to the continental crust, many geologists believe that the continental crust in these areas builds up due to the input of mantle matter.

Volcanoes that act along oceanic ridges (such as the Hawaiian ridge) erupt material of a predominantly basaltic composition, such as Aa lava. These volcanoes are probably associated with shallow earthquakes, the depth of which does not exceed 70 km. Since basaltic lavas are found both on continents and along oceanic ridges, geologists assume that there is a layer directly under the earth's crust from which basaltic lavas come.

However, it is not clear why both andesites and basalts are formed from mantle matter in some areas, and only basalts in others. If, as is now believed, the mantle is indeed ultramafic (rich in iron and magnesium), then the mantle-derived lavas must be basaltic, not andesitic, since andesite minerals are absent from ultramafic rocks. This contradiction is resolved by the theory of plate tectonics, according to which oceanic crust moves under the island arcs and melts at a certain depth. These molten rocks are poured out in the form of andesitic lavas.

Varieties of lava

The lava of different volcanoes is different. It differs in composition, color, temperature, impurities, etc.

carbonate lava

Half consists of sodium and potassium carbonates. This is the coldest and most liquid lava on earth, it flows over the earth like water. The temperature of the carbonate lava is only 510-600 °C. The color of hot lava is black or dark brown, but as it cools it becomes lighter, and after a few months it becomes almost white. Hardened carbonate lavas are soft and brittle, easily soluble in water. Carbonate lava flows only from the Oldoinyo Lengai volcano in Tanzania.

silicon lava

Silicon lava is most characteristic of the volcanoes of the Pacific ring of fire, such lava is usually very viscous and sometimes solidifies in the vent of the volcano even before the end of the eruption, thereby stopping it. A plugged volcano may swell a little, and then the eruption resumes, usually with a strong explosion. Lava contains 53-62% silicon dioxide. It has average speed flow (several meters per day), temperature 800-900 °C. If the silica content reaches 65%, then the lava becomes very viscous and clumsy. The color of hot lava is dark or black-red. Solidified silicic lavas can form black volcanic glass. Such glass is obtained when the melt cools rapidly, without having time to crystallize.

basalt lava

The main type of lava erupted from the mantle is characteristic of oceanic shield volcanoes. Half consists of silicon dioxide (quartz), half - aluminum oxide, iron, magnesium and other metals. This lava is very mobile and is capable of flowing at a speed of 2 m/s (the speed of a fast walking person). It has high temperature 1200-1300°C. Basalt lava flows are characterized by a small thickness (a few meters) and a large extent (tens of kilometers). The color of hot lava is yellow or yellow-red.

Literature

• Natela Yaroshenko Fiery youth of volcanoes // Encyclopedia of wonders of nature. - London, New York, Sydney, Moscow: Reader's Digest, 2000. - S. 415-417. - 456 p. - ISBN 5-89355-014-5

Notes

see also

Links

• Metamorphoses of lava on the site of the magazine "Vokrug Sveta"

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Synonyms:

See what "Lava" is in other dictionaries:

Lavash, ah, eat ... Russian word stress

Dictionary Dalia

Female a different mixture of molten rocks flowing from the mouths of fire mountains; floater II. LAVA for women a bench, a deaf, fixed bench, a seat board along the wall; sometimes a bench, a portable board with legs; | southern, novg., yarosl. ... ... Dahl's Explanatory Dictionary

- (Spanish lava current rain flow). Molten substance erupted by volcanoes. Dictionary foreign words included in the Russian language. Chudinov, A.N., 1910. LAVA, a substance ejected from a vent by a volcano. Complete dictionary foreign words... Dictionary of foreign words of the Russian language

Development, mass, slaughter, coverage, system, attack, magma Dictionary of Russian synonyms. lava n., number of synonyms: 20 aa lava (2) at ... Synonym dictionary

LAVA, molten rock, or MAGMA, reaching the surface of the Earth and flowing out through volcanic vents in streams or layers. There are three main types of lava: bubbly, like pumice; glassy, ​​like obsidian; even-grained. By… … Scientific and technical encyclopedic dictionary

1. LAVA1, lavas, women. (Italian lava). 1. Molten fiery liquid mass ejected by a volcano during an eruption. 2. trans. Something grandiose, fast, steadily moving, sweeping away everything in its path. "We're going revolutionary lava." Mayakovsky ... Explanatory Dictionary of Ushakov

Types of volcanoes and lava have fundamental differences that make it possible to distinguish several main types from them.

Volcano types

• Hawaiian type of volcanoes. These volcanoes do not have a significant release of vapors and gases, their lava is liquid.
• Stromboli type of volcanoes. These volcanoes also have liquid lava, but they emit a lot of vapors and gases, but do not emit ash; as the lava cools, it becomes undulating.
• Vesuvius-type volcanoes are characterized by more viscous lava, vapors, gases, volcanic ash and other solid products of the eruption are abundantly released. As the lava cools, it becomes lumpy.
• Peleian type of volcanoes. Very viscous lava causes strong explosions with the release of hot gases, ash and other products in the form of scorching clouds, destroying everything in its path, etc.

Hawaiian type of volcanoes

Hawaiian-type volcanoes calmly and abundantly pour out only liquid lava during the eruption. These are the volcanoes of the Hawaiian Islands.

The Hawaiian volcanoes, which lie at the bottom of the ocean, at a depth of approximately 4600 meters, were undoubtedly the result of powerful underwater eruptions. The strength of these eruptions can be judged by the fact that absolute height extinct volcano Mauna Kea (i.e. " white mountain") reaches from the bottom of the ocean 8828 meters ( relative height volcano 4228 meters).

The most famous are Mauna Loa, otherwise " high mountain"(4168 meters), and Kilauea (1231 meters).

Kilauea has a huge crater - 5.6 kilometers long and 2 kilometers wide. At the bottom of it, at a depth of 300 meters, lies a seething lava lake. During eruptions, powerful lava fountains up to 280 meters high are formed on it, with a diameter of approximately 30 meters.

Volcano Kilauea

Liquid lava droplets ejected to such a height are drawn in the air into thin threads, called by the indigenous population "Pele's hair" - the goddess of fire of the ancient inhabitants of the Hawaiian Islands. Lava flows during the eruption of Kilauea sometimes reached a huge value - up to 60 kilometers long, 25 kilometers wide and 10 meters thick.

Stromboli type of volcanoes

Stromboli type of volcanoes emitting mainly gaseous products. For example, the Stromboli volcano (900 meters high), on one of the Aeolian Islands (north of the Strait of Messina, between the island of Sicily and the Apennine Peninsula).

Stromboli volcano on the island of the same name

At night, the reflection of its fiery vent in a column of vapors and gases, perfectly visible at a distance of up to 150 kilometers, serves as a natural beacon for sailors.

Widely known among sailors around the world is another natural lighthouse, in Central America off the coast of El Salvador - the volcano Tsalko. Gently every 8 minutes, he throws out a column of smoke and ash, rising to 300 meters. In the dark tropical sky, it is spectacularly illuminated by the crimson reflection of lava.

Vesuvius-type volcanoes

Most complete picture eruptions give volcanoes of type . A volcanic eruption is usually preceded by a strong underground rumble that accompanies the impacts and tremors of earthquakes.

From the cracks on the slopes of the volcano, suffocating gases begin to be released. The release of gaseous products - water vapor and various gases (carbon dioxide, sulfur dioxide, hydrochloric, hydrogen sulfide and many others) is intensified. They are released not only through the crater, but also from fumaroles (fumarole is a derivative of Italian word"fumo" - smoke).

Puffs of steam, along with volcanic ash, rise several kilometers into the atmosphere. Masses of light gray or black volcanic ash, representing the smallest pieces of solidified lava, are carried thousands of kilometers. The ashes of Vesuvius, for example, reach Constantinople and North America.

Black puffs of ash cover the sun, turning a bright day into dark night. strong electrical voltage from the friction of ash particles and vapors, it manifests itself in electrical discharges and thunder.

Vapors raised to a considerable height thicken into clouds, from which streams of mud pour instead of rain. Volcanic sand, stones of various sizes, as well as volcanic bombs are ejected from the mouth of the volcano - rounded pieces of lava frozen in the air. Finally, lava appears from the mouth of the volcano, which rushes along the mountainside in a fiery stream.

Volcano of the same type - Klyuchevskaya Sopka

Here is how the picture of the eruption of a volcano of this type - Klyuchevskoy Sopka on October 6, 1737, (more details:), the first Russian explorer of Kamchatka, acad. S. P. Krasheninnikov (1713-1755). He participated in the Kamchatka expedition as a student of the Russian Academy of Sciences in 1737-1741.

The whole mountain seemed like a hot stone. The flame, which was visible inside it through the crevices, sometimes rushed down like fiery rivers, with a terrible noise. Thunder was heard in the mountain, crackling and swelling, as if with strong furs, from which all nearby places trembled.

An unforgettable picture of the eruption of the same volcano on the night of the new year, 1945, is given by a modern observer:

A sharp orange-yellow cone of flame, one and a half kilometers high, seemed to pierce into clubs of gases rising in a huge mass from the volcano's crater to about 7000 meters. Hot volcanic bombs fell in a continuous stream from the top of the fiery cone. There were so many of them that they gave the impression of a fabulous fiery blizzard.

The figure shows samples of various volcanic bombs - these are lava clots that have taken certain form. They acquire a rounded or spindle-shaped shape by rotating during flight.

1. Volcanic bomb spherical shape- sample from Vesuvius;
2. Trass - porous trachyte tuff - specimen from Eichel, Germany;
3. Fusiform Volcanic Bomb molds - sample from Vesuvius;
4. Lapilli - small volcanic bombs;
5. A crusted volcanic bomb, a specimen from southern France.

Peleian type of volcanoes

Peleian type of volcanoes paints an even more horrific picture. As a result terrible explosion a significant part of the cone is suddenly sprayed into the air, covering it with an impenetrable haze sunlight. Such was the eruption.

The Japanese volcano Bandai-San belongs to the same type. For more than a thousand years, it was considered extinct, and suddenly, unexpectedly, in 1888, a significant part of its cone 670 meters high takes off into the air.

The awakening of the volcano from its long dormancy was terrible:

the blast uprooted the trees and caused terrible destruction. The pulverized rocks remained in the atmosphere in a dense veil for 8 hours, covering the sun, and the bright day changed dark night... The release of liquid lava did not occur.

This kind of eruptions of volcanoes of the Peleic type are explained the presence of very viscous lava, which prevents the release of vapors and gases accumulated under it.

Rudimentary forms of volcanoes

Meet, in addition to the listed types, rudimentary forms of volcanoes, when the eruption was limited to a breakthrough to the surface of the earth only vapors and gases. These rudimentary volcanoes, called "maars", are found in West Germany near the city of Eifel.

Their craters are usually filled with water and in this respect the maars are like lakes surrounded by a low rampart of rock fragments ejected by a volcanic explosion. Fragments of rocks also fill the bottom of the maar, and already ancient lava begins deeper.

The richest diamond deposits in South Africa, located in ancient volcanic channels, by their nature, apparently, are formations similar to maars.

lava type

acidic lavas are distinguished by their light color and low specific gravity. They are rich in vapors and gases, viscous and inactive. When cooled, they form the so-called blocky lava.

Basic lavas, on the contrary, are dark in color, fusible, poor in gases, have high mobility and a significant specific gravity. When cooled, they are called "wavy lavas".

Vesuvius volcano lava

By chemical composition lava is different not only in volcanoes various types, but also near the same volcano, depending on the periods of eruption. For example, Vesuvius V modern time pours out light (acidic) trachytic lavas, more ancient part volcano, the so-called Somme, is composed of heavy basalt lavas.

lava movement speed

Medium lava movement speed- five kilometers per hour, but in individual cases liquid lava moved at a speed of 30 kilometers per hour.

The poured out lava soon cools down, forming a dense slag-like crust on it. Due to the poor thermal conductivity of lava, it is quite possible to walk on it, like on the ice of a frozen river, even during the movement of the lava flow. However, inside the lava retains a high temperature for a long time: metal rods lowered into the cracks of the cooling lava flow quickly melt.

Under the outer crust, the slow movement of lava continues for a long time - it was noted in the flow 65 years ago, while traces of heat were established in one case even 87 years after the eruption.

Lava flow temperature

The lava of Vesuvius, seven years after the 1858 eruption, kept more temperature at 72°. The initial temperature of the lava was determined for Vesuvius at 800-1000 °, and the lava of the Kilauea crater (Hawaiian Islands) - 1200 °.

In this regard, it is interesting to learn how two researchers from the Kamchatka volcanological station measured the temperature of the lava flow.

In order to carry out the necessary research, they jumped dangerously onto the moving crust of the lava flow. On their feet they wore asbestos boots, which did not conduct heat well. Although it was cold November and blew strong wind However, even in asbestos boots, the legs still got so hot that they had to alternately stand on one or the other leg in order for the sole to cool down at least a little. The temperature of the lava crust reached 300°. The brave explorers continued to work. Finally, they managed to break through the crust and measure the temperature of the lava: at a depth of 40 centimeters from the surface, it was 870 °.

The name "volcano" goes back to the name of the ancient Roman deity Vulcan, the patron of fire and blacksmithing. According to legend, it was on Mount Etna, which is still active and periodically erupting, that his workshop was located. Another curious legend explains the awakening of the volcano by a giant who is trying to get out of prison under the mountain, which leads to an eruption. In reality, everything is not so bizarre, but no less interesting and, perhaps, just as creepy as the idea that a warlike giant can live under a volcano.

From geography lessons at school, everyone remembers that under the solid earth's surface, called the crust, there is a layer of molten, incredibly hot rocks - the mantle. When in earth's crust cracks appear, igneous rocks from the upper layers of the mantle, which were under enormous pressure, like a mythical giant, rush out, making their way through the resulting fault. Already at the surface, magma is divided into:

• lava - the temperature of which varies from 500 to 1200 degrees Celsius
  volcanic gases
• ash

Since the main reason for coming to the surface igneous rocks this is the formation of cracks in the upper layer of the lithosphere due to shear tectonic plates, it is not surprising that majority active volcanoes is located in the so-called zone of the Pacific ring of fire, which is a kind of "poorly stitched seam" between continental plates. Rest active volcanoes, which around the world on this moment there are about 500, in the vast majority of cases they are confined to other fault zones of the earth's crust.

Eruption process

The structure of the volcano is quite simple, and its eruption is devoid of any mysticism, being only a consequence of the internal processes of our planet. The channel through which hot magma erupts from the center of the earth is called the mouth of a volcano. It is connected to the magma chamber - underground reservoir, which, as the name suggests, is filled with magma. During the eruption, a kind of "body" of the volcano begins to form around the vent, most often having the shape of a cone. It is made up of lava, ash and rocks. Above, where the magma finally finds its way out, is a crater, in most cases shaped like a funnel or just a depression. Sometimes cracks and side craters appear on the slopes of volcanoes, through which magma can also come out.

A volcanic eruption occurs when the pressure in the magma chamber becomes too high, and the gases that saturate the magma begin to rapidly rise upward, literally pushing it out. This process is somewhat reminiscent of shaking a soda bottle - if the cork in the neck does not hold well, then gases under high pressure knock out the cork, “pulling” water out of the bottle.

Classification of volcanoes

Classification by activity

Volcanoes themselves are classified according to several criteria, the most important of which is the degree of their volcanic activity, because it depends on this whether the volcano is potentially dangerous or not. So, according to the degree of activity, they are divided into only three types - active, sleeping and extinct.

Operating those volcanoes are considered, the eruptions of which have human evidence. These eruptions could have occurred ten, one hundred, one thousand or five thousand years ago, but since the period of volcano activity is quite long (in some cases it can reach several million years), they are usually referred to as active.

sleeping they call such volcanoes that have not erupted for a long time and may never erupt, but for them there is always such a chance.

The possibility of an eruption of an extinct volcano tends to zero. But at the same time, there are cases when a volcano, previously considered extinct, woke up and brought many troubles.

However, among scientists there is no consensus on this classification, just as there is no way to 100% reliably determine the degree of volcano activity.

Classification by type

The following way of classifying volcanoes divides them into two main types - linear and central.

Linear volcanoes are long fissures from which liquid erupts. basalt magma that forms real lava fields around the volcano. For example, the relief of Iceland was formed in this way.

The central volcanoes are, most often, precisely those cone-shaped elevations that our imagination draws for us when we hear the word "volcano".

Regardless of whether volcanoes are linear or central, they are usually classified according to their shape, which mainly depends on the composition of the magma they erupt.

• Shield volcanoes appear as a result of repeated eruptions of liquid basaltic magma, which spreads in all directions for many kilometers, forming a kind of shield, which gave them such a name.
• Stratovolcanoes are composed of alternating layers of thick, rapidly solidifying lava and pyroclastic material (a mixture of hot gas, rocks, and ash). These are the highest volcanoes and, perhaps, the most dangerous, since the high viscosity of the magma causes clogging of the crater, resulting in powerful and destructive explosions.
• Cinder cones are the most common type of volcanoes on land. They are formed as a result of heaps of porous slag rocks around the crater of the volcano. Most often, their height does not exceed several hundred meters.

Of course, it happens that some volcano cannot be attributed to one certain type. In this case, it is called complex (composite).

All these classifications make it possible to understand what, in fact, such a phenomenon as volcanism is, what people can expect from these fiery giants and how they can learn to coexist with them. Because of the extreme danger volcanic eruptions such a field of science as volcanology is very significant for the safety of mankind. At the same time, volcanoes are explored not only in order to predict their eruptions, but also in order to learn more about our planet, its origin, internal processes, the mysteries of the emergence and development of life. It is assumed that at some point volcanic activity made it possible for life to arise on Earth. And if this is true, then who knows what other secrets volcanoes hide in themselves.

People, for many centuries, were afraid of fire. Until humanity has learned to create and use it for good. But no one knew about it before. People were afraid of fire, let alone "lava", which is almost impossible to deal with. Of course, I always wanted to see lava, how it overflows and burns everything in its path, but this is very dangerous. Therefore, since it is almost impossible to see it, let me at least tell you what it is.

What is lava

Lava -liquid molten minerals, which are ejected to the ground during an eruption. Another name for lava is magma". When erupting, lava reaches 700–1100 degrees Celsius. It does not move very fast, but it is better not to approach it closer than 10 meters. When the lava still begins to solidify, then at first it turns red, and then black. This is how new mountains appear.

But, unfortunately, not everything is always so good. Usually the lava is viscous and during the time that it flows, people can take their things and run away. But there is liquid lava, which moves much faster. The fastest result recorded of all time was in 1977. Maximum the speed of the lava reached 17 meters per sec.kundu.

There are several types of lava:

What is an eruption and some facts

Eruption - volcanic ejection to earthhot debris, ashes, lava. The eruption is one of the most dangerous natural disasters, which can lead to the death of thousands of people.

Most famous city who suffered from a volcanic eruption Vesuvius, called Pompeii. This city was located in the ancient Rome, near Naples. Died during the eruption 2000 Human. Until now, fossilized corpses are found in the city and beyond. The eruption took place in 79 year of our era.

Yes, of course, the eruption of lava is a breathtaking sight. But is it worth it? One false step and you will suffer a painful death. Be careful. No matter how beautiful the lava looks, it is better not to approach it.

The question of what lava is has been of interest to many scientists for a long time. The composition of this substance, as well as its shape, speed of movement, temperature and other aspects have been the subject of a number of studies and scientific works. This can be explained by the fact that it is its frozen streams that are almost the only source of information regarding the state of the Earth's interior.

General concept

First you need to understand what lava is in modern understanding? Scientists call it the material in the molten state, located in the upper part of the mantle. While in the bowels of the earth, the composition of the substance is homogeneous, but as soon as it approaches the surface, the process of boiling begins with the release of gas bubbles. It is they who move the hot material towards the cracks in the crust. At the same time, not all liquid erupts to the surface. Speaking about the meaning of the word "lava", it should be noted that this concept applies only to the poured out part of matter.

basalt lava

The most common type on our planet is basalt lava. Most of all geological processes, which occurred on Earth many thousands of years ago, were accompanied by numerous eruptions of this particular type of hot substance. After it solidified, a black rock of the same name was formed. Half of the composition of basaltic lavas is magnesium, iron and some other metals. Due to them, the melt temperature reaches a mark of about 1200 degrees. At the same time, the lava flow moves at a speed of about 2 meters per second, which is comparable to a running person. Studies show that in the future they move much faster along the so-called "hot tracks". The basaltic lava from the volcano is notable for its small thickness. It flows quite far (up to several tens of kilometers from the crater). It should be noted that this species is characteristic of both land and ocean.

sour lava

In the case when the composition of the substance contains 63% or more silica, it is called acidic lava. The incandescent material is very viscous and practically unable to flow. The speed of the flow often does not even reach a mark of several meters per day. The temperature of the substance in this case is in the range from 800 to 900 degrees. Melts of this kind are associated with the formation of unusual rocks(ignimbrites, for example). If acidic lava is highly saturated with gas, it boils and becomes mobile. After ejection from the crater, it quickly flows back into the resulting depression (caldera). The consequence of this is the appearance of pumice - an ultra-light material, the density of which is less than that of water.

carbonate lava

Speaking about what lava is, many scientists still cannot determine the principle of formation of its carbonate variety. Part given substance includes sodium. It erupts from only one volcano on the planet - Oldoinyo Lengai, which is located in Northern Tanzania. Carbonate lava is the most liquid and cold of all existing species. Its temperature is approximately 510 degrees, and it moves along the slopes at the same speed as water. Initially, the substance has a dark brown or black color, but after a few hours of being outside it becomes lighter, and after a few months it turns completely white.

conclusions

Summing up, one should focus on the fact that one of the most acute geological problems is associated with lava. It lies in the fact that this substance warms up earth's interior. The centers of hot material rise to the earth's surface, after which they melt it and form volcanoes. Even the world's leading scientists cannot give an unambiguous answer to the question of what lava is. At the same time, we can say for sure that it is only a tiny part of global process, driving force which is hidden very deep underground.