Cooling of lava. What happens when a person falls into a lava flow? What happens when lava cools?
Types of volcanoes and lava have fundamental differences that make it possible to distinguish several main types from them.Types of volcanoes
- Hawaiian type of volcanoes. These volcanoes do not exhibit significant release of vapors and gases; their lava is liquid.
- Strombolian 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 wavy.
- Volcanoes like Vesuvius characterized by more viscous lava, vapors, gases, volcanic ash and other solid eruption products are released abundantly. As lava cools, it becomes blocky.
- 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 During an eruption, they calmly and abundantly pour out only liquid lava. These are the volcanoes of the Hawaiian Islands. The Hawaiian volcanoes, whose bases lie on the ocean floor at a depth of approximately 4,600 meters, were undoubtedly the result of powerful underwater eruptions. The strength of these eruptions can be judged by the fact that the absolute height of the extinct volcano Mauna Kea (i.e., the “white mountain”) reaches from the ocean floor 8828 meters (relative height of the 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, at a depth of 300 meters, lies a seething lava lake. During eruptions, powerful lava fountains are formed on it, up to 280 meters high, with a diameter of approximately 30 meters. Kilauea Volcano. Droplets of liquid lava thrown to such a height are stretched in the air into thin threads, called by the indigenous population “the hair of Pele” - the goddess of fire of the ancient inhabitants of the Hawaiian Islands. Lava flows during the Kilauea eruption sometimes reached enormous sizes - up to 60 kilometers in length, 25 kilometers in width and 10 meters in thickness.Strombolian type of volcanoes
Strombolian type of volcanoes emitting mainly only 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).
Volcano Stromboli on the island of the same name. At night, the reflection of its fiery vent in a column of vapors and gases, clearly visible at a distance of up to 150 kilometers, serves as a natural beacon for sailors. Another natural lighthouse in Central America off the coast of El Salvador is the Tsalko volcano, which is widely known among sailors all over the world. Gently every 8 minutes it emits a column of smoke and ash, rising 300 meters. Against a dark tropical sky, it is effectively illuminated by the crimson glow of lava. Volcanoes like Vesuvius
The most complete picture of an eruption is provided by volcanoes of the type. A volcanic eruption is usually preceded by a strong underground rumble that accompanies the impacts and tremors of earthquakes. Choking gases begin to be released from cracks on the slopes of the volcano. The release of gaseous products - water vapor and various gases (carbon dioxide, sulfur dioxide, hydrochloride, hydrogen sulfide and many others) increases. They are released not only through the crater, but also from fumaroles (fumarole is a derivative of the Italian word "fumo" - smoke). Plumes of steam along with volcanic ash rise several kilometers into the atmosphere. Masses of light gray or black volcanic ash, representing tiny pieces of solidified lava, are carried for thousands of kilometers. The ashes of Vesuvius, for example, reach Constantinople and North America. Black clouds of ash obscure the sun, turning a bright day into a dark night. Strong electrical voltage from the friction of ash particles and vapors manifests itself in electrical discharges and thunderclaps. Vapors raised to a considerable height condense into clouds, from which streams of mud pour out instead of rain. Ejected from the crater of a volcano volcanic sand, stones of various sizes, as well as volcanic bombs - rounded pieces of lava frozen in the air. Finally, lava appears from the crater of the volcano, which rushes down the mountainside like a fiery stream.A volcano of the same type - Klyuchevskaya Sopka
This is how the picture of the eruption of a volcano of this type - Klyuchevskaya Sopka on October 6, 1737, is conveyed (more details:), the first Russian explorer of Kamchatka, Acad. S. P. Krasheninnikov (1713-1755). He took part in the Kamchatka expedition while still a student at the Russian Academy of Sciences in 1737-1741.The whole mountain seemed like a hot stone. The flames, which were visible inside it through the crevices, sometimes rushed down like rivers of fire, with a terrible noise. In the mountain one could hear thunder, a crash and, as if by strong bellows, swelling, from which all nearby places trembled.A modern observer gives an unforgettable picture of the eruption of the same volcano on the night of New Year 1945:
A sharp orange-yellow cone of flame, one and a half kilometers high, seemed to pierce the clouds of gases that rose in a huge mass from the crater of the volcano to approximately 7000 meters. From the top of the fiery cone, hot volcanic bombs fell in a continuous stream. 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 clots of lava that have taken a certain form. They acquire a round or spindle-shaped shape by rotating during flight.
- Volcanic bomb of spherical shape - a sample from Vesuvius;
- Trass - porous trachytic tuff - specimen from Eichel, Germany;
- Volcanic fusiform bomb sample forms from Vesuvius;
- Lapilli - small volcanic bombs;
- Encrusted volcanic bomb - specimen from Southern France.
Peleian type of volcanoes
Peleian type of volcanoes presents an even more terrible picture. As a result of a terrible explosion, a significant part of the cone suddenly sprays into the air, covering it with an impenetrable haze sunlight. This was the eruption. The Japanese volcano Bandai-San also belongs to this type. For more than a thousand years it was considered extinct, and suddenly, in 1888, a significant part of its 670-meter-high cone flies into the air.
Volcano Bandai-san. The awakening of the volcano from a long rest was terrible: the blast wave uprooted trees and caused terrible destruction. The atomized rocks remained in the atmosphere in a dense veil for 8 hours, blocking out the sun, and the bright day gave way to a dark night... There was no release of liquid lava.This type of volcanic eruption of the Peleian type is explained by presence of very viscous lava, preventing the release of vapors and gases accumulated under it.
Rudimentary forms of volcanoes
In addition to the listed types, there are rudimentary forms of volcanoes, when the eruption was limited to the breakthrough of only vapors and gases to the surface of the earth. These rudimentary volcanoes, called “maars,” are found in Western Germany near the Eifel. Their craters are usually filled with water and in this respect the maars are similar to lakes, surrounded by a low rampart of rock fragments ejected by a volcanic explosion. Rock fragments also fill the bottom of the maar, and deeper the ancient lava begins. The richest diamond deposits in South Africa, located in ancient volcanic channels, are, by their nature, apparently formations similar to maars.Lava type
Based on silica content, they are classified acidic and basic lavas. In the former, its amount reaches 76%, and in the latter it does not exceed 52%. Acidic lavas They are distinguished by their light color and low specific gravity. They are rich in vapors and gases, viscous and inactive. When cooled, they form so-called block lava.
Basic lavas, on the contrary, are dark in color, fusible, low in gases, have high mobility and significant specific gravity. When cooled, they are called "wavy lavas." 
Lava of Vesuvius volcano
By chemical composition lava is different not only at volcanoes various types, but also at the same volcano depending on the periods of eruptions. For example, Vesuvius V modern times pours out light (acidic) trachytic lavas, more ancient part The volcano, the so-called Somma, is composed of heavy basaltic lavas.Lava movement speed
Average lava movement speed- five kilometers per hour, but in some cases the liquid lava moved at a speed of 30 kilometers per hour. The spilled lava soon cools and a dense slag-like crust forms 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 while the lava flow is moving. However, inside the lava remains at a high temperature for a long time: metal rods lowered into cracks of the cooling lava flow quickly melt. Under the outer crust for a long time The slow movement of lava is still ongoing - it was noted in a flow 65 years ago, while traces of heat were detected in one case even 87 years after the eruption.Lava flow temperature
Seven years after the 1858 eruption, the lava of Vesuvius still contained temperature at 72°. The initial temperature of the lava was determined for Vesuvius to be 800-1000°, and the lava of the Kilauea crater (Hawaii Islands) was 1200°. In this regard, it is interesting to see 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 onto the moving crust of the lava flow at the risk of their lives. They had asbestos boots on their feet, which did not conduct heat well. Although it was cold November and it was blowing strong wind, however, even in asbestos boots, the feet still became so hot that one had to alternately stand on one foot or the other so that the sole would cool down at least a little. The temperature of the lava crust reached 300°. Brave researchers 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°. After measuring the temperature of the lava and taking a gas sample, they safely jumped onto the frozen side of the lava flow.Due to the poor thermal conductivity of the lava crust, the air temperature above the lava flow changes so little that trees continue to grow and bloom even on small islands bordered by arms of a fresh lava flow. Lava outpouring occurs not only through volcanoes, but also through deep cracks in the earth's crust. In Iceland there are lava flows frozen between layers of snow or ice. Lava, filling cracks and voids in the earth's crust, can maintain its temperature for many hundreds of years, which explains the presence hot springs in volcanic areas.
Volcanic lava is called the blood of the Earth. It is an integral companion of eruptions and each volcano has its own composition, color and temperature.
1. Lava is magma that flows out of a volcanic vent during an eruption. Unlike magma, it does not contain gases, since they escape during explosions.
2. Lava began to be called “lava” only after the eruption of Vesuvius in 1737. Geologist Francesco Serao, who was researching the volcano in those years, initially called it “labes”, which means “collapse” in Latin, and later the word acquired its modern meaning.
3. Different volcanoes have different lava compositions. Most often it is composed of basalts and differs slow flow, like batter.
Basaltic lava at Kilauea Volcano
4. The most liquid lava, resembling water, contains potassium carbonates and is found only on.
5. In the depths of the Yellowstone supervolcano there is rhyolite magma, which has an explosive nature.
6. The most dangerous lava is corium, or lava-like fuel contained in nuclear reactors. It is a fusion of the contents of the reactor with concrete, metal parts and other debris that is generated as a result of a nuclear crisis.
7. Despite the fact that corium has a technical origin, its flows are under Chernobyl nuclear power plant outwardly resemble cooled basalt flows.
8. The most unusual in the world is the so-called “ blue lava"on the Ijen volcano in Indonesia. In fact, the brightly glowing streams are not lava, but sulfur dioxide gas, which, when released from the vents, turns into a liquid state and glows blue.
9. You can determine its temperature by the color of lava. Yellow and bright orange are considered the hottest and have a temperature of 1000 °C and above. Dark red is relatively cool, with temperatures ranging from 650 to 800 °C.
10. The only black lava is found in the Tanzanian volcano Ol Doinyo Lengai. As mentioned above, it consists of carbonates, which give it a dark tint. The lava flows at the summit are quite cool, with a temperature of no more than 540 °C. When cooled, they become silvery in color, creating bizarre landscapes around the volcano.
11. On the Pacific Ring of Fire, volcanoes erupt mainly silicon lava, which has a viscous consistency and solidifies in the mouth of the mountain, stopping its eruption. Subsequently, under pressure, the frozen plug is knocked out of the crater, resulting in a powerful explosion.
12. According to research, in the early days of its existence, our planet was covered with lava oceans, layered in structure.
13. When lava flows down slopes, it cools unevenly, so sometimes lava tubes form inside the flows. The length of these tubes can reach several kilometers, and the width inside is 14–15 meters.
Origin of lava
Lava is formed when a volcano erupts magma onto the Earth's surface. Due to cooling and interaction with gases included in 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, the 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 influx of mantle material.
Volcanoes that operate along oceanic ridges (such as the Hawaiian ridge) erupt predominantly basaltic material, such as Aa lava. These volcanoes are probably associated with shallow earthquakes, the depth of which does not exceed 70 km. Because basaltic lavas are found both on continents and along ocean ridges, geologists hypothesize that there is a layer just below the Earth's crust from which basaltic lavas come.
However, it is unclear why in some areas both andesites and basalts are formed from mantle material, while in others only basalts are formed. If, as is now believed, the mantle is indeed ultramafic (enriched in iron and magnesium), then lavas derived from the mantle should have a basaltic rather than andesitic composition, since andesite minerals are absent in ultramafic rocks. This contradiction is resolved by the theory of plate tectonics, according to which the oceanic crust moves under island arcs and melts at a certain depth. These molten rocks erupt in the form of andesite lavas.
Types of lava
Lava varies from volcano to volcano. 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 along the ground like water. The temperature of 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. Solidified carbonate lavas are soft and brittle and easily dissolve in water. Carbonate lava flows only from the Oldoinyo Lengai volcano in Tanzania.
Silicon lava
Silicon lava is most typical for the volcanoes of the Pacific Ring of Fire; such lava is usually very viscous and sometimes solidifies in the crater 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 powerful 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 silicon lavas can form black volcanic glass. Such glass is obtained when the melt cools quickly 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 - from aluminum oxide, iron, magnesium and other metals. This lava is very mobile and can flow at a speed of 2 m/s (the speed of a fast walking person). It has a high temperature of 1200-1300 °C. Basaltic lava flows are characterized by a small thickness (a few meters) and a large length (tens of kilometers). The color of hot lava is yellow or yellow-red.
Literature
- Natela Yaroshenko Fiery youth of volcanoes // Encyclopedia of natural wonders. - London, New York, Sydney, Moscow: Reader's Digest, 2000. - pp. 415-417. - 456 s. - ISBN 5-89355-014-5
Notes
see also
Links
- Metamorphoses of lava on the website of the magazine “Around the World”
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Synonyms:See what "Lava" is in other dictionaries:
Lavash, oh, I eat... Russian word stress
Dictionary Dahl
Women a different mixture of molten rocks flowing from the mouth of the fire mountains; swimmer II. LAVA female a bench, a blank, fixed bench, a board for a seat along the wall; sometimes a bench, a portable board with legs; | south., nov., yarosl.... ... Dahl's Explanatory Dictionary
- (Spanish lava flowing rain stream). Molten material erupted by volcanoes. Dictionary foreign words, included in the Russian language. Chudinov A.N., 1910. LAVA is a substance ejected from a vent by a volcano. A complete dictionary of foreign words... Dictionary of foreign words of the Russian language
Production, mass, face, reach, structure, attack, magma Dictionary of Russian synonyms. lava noun, number of synonyms: 20 aa lava (2) at... Synonym dictionary
LAVA, molten rock, or MAGMA, reaching the surface of the Earth and flowing through volcanic vents in streams or sheets. There are three main types of lava: bubbly, like pumice; glassy, like obsidian; Equal-grained. By… … Scientific and technical encyclopedic dictionary
Ushakov's Explanatory Dictionary
1. LAVA1, lava, female. (Italian lava). 1. Molten fiery liquid mass ejected by a volcano during an eruption. 2. transfer Something grandiose, fast, steadily moving, sweeping away everything along the way. “We are marching on a revolutionary path.” Mayakovsky... Ushakov's Explanatory Dictionary
1. LAVA1, lava, female. (Italian lava). 1. Molten fiery liquid mass ejected by a volcano during an eruption. 2. transfer Something grandiose, fast, steadily moving, sweeping away everything along the way. “We are marching on a revolutionary path.” Mayakovsky... Ushakov's Explanatory Dictionary
1. LAVA1, lava, female. (Italian lava). 1. Molten fiery liquid mass ejected by a volcano during an eruption. 2. transfer Something grandiose, fast, steadily moving, sweeping away everything along the way. “We are marching on a revolutionary path.” Mayakovsky... Ushakov's Explanatory Dictionary
1. LAVA, s; and. [ital. lava] 1. Molten mineral mass erupted by a volcano. 2. whom what or what. An uncontrollably moving mass (people, animals, etc.). ◁ Lava, in the sign. adv. Spread like lava (in a continuous stream). Lava, oh, oh; (1 digit... encyclopedic Dictionary
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 become the subject of a number of studies and scientific works. This can be explained by the fact that it is its frozen flows that represent almost the only source of information regarding the state of the Earth’s interior.
General concept
First, you need to figure out what lava is in the modern sense? Scientists call it the material in a 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. They are the ones who move the hot material towards the cracks in the bark. However, not all of the liquid erupts to the surface. Speaking about the meaning of the word “lava”, it should be noted that this concept applies only to the spilled part of the matter.
Basalt lava
The most common type on our planet is basaltic lava. Most of all the geological processes that 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 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. As studies show, in the future they move much faster in the so-called “hot pursuit”. Basaltic lava from the volcano is thin. It flows quite far (up to several tens of kilometers from the crater). It should be noted that this variety is typical for both land and ocean.
Acidic lava
In the case when the substance contains 63% or more silica, it is called acidic lava. The heated material is very viscous and practically incapable of flow. The speed of the flow often does not even reach several meters per day. The temperature of the substance 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 becomes highly saturated with gas, it boils and becomes mobile. After being ejected 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 whose density 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 of this 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 coldest 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 just a few hours of being on the outside it becomes lighter, and after a few months it turns completely white.
conclusions
To summarize, we should focus on the fact that one of the most pressing geological problems is associated with lava. It lies in the fact that this substance heats up the bowels of the earth. Foci 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 a clear 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 the global process, driving force which is hidden very deep underground.
When volcanoes erupt, hot molten rocks - magma - pour out. In air, the pressure drops sharply, and the magma boils - gases leave it.
The melt begins to cool. In fact, only these two properties – temperature and “carbonation” – distinguish lava from magma. Over the course of a year, 4 km³ of lava spills across our planet, mainly at the bottom of the oceans. Not so much, on land there were regions filled with a lava layer 2 km thick.
The initial temperature of the lava is 700–1200°C and higher. Dozens of minerals and rocks are melted in it. They include almost all known chemical elements, but most of all silicon, oxygen, magnesium, iron, aluminum.
Depending on the temperature and composition, lava has different colors, viscosity and fluidity. Hot, it's shiny bright yellow and orange; cooling down, it turns red and then black. It happens that blue lights of burning sulfur run above the lava flow. And one of the volcanoes in Tanzania erupts black lava, which, when frozen, becomes like chalk - whitish, soft and brittle.
The flow of viscous lava is slow and flows barely (a few centimeters or meters per hour). Along the way, hardening blocks are formed in it. They slow down traffic even more. This kind of lava solidifies in mounds. But the absence of silicon dioxide (quartz) in lava makes it very liquid. It quickly covers vast fields, forms lava lakes, rivers with a flat surface, and even “lava falls” on cliffs. There are few pores in such lava, since gas bubbles easily leave it.
What happens when lava cools?
As the lava cools, the molten minerals begin to form crystals. The result is a mass of compressed grains of quartz, mica and others. They can be large (granite) or small (basalt). If cooling proceeds very quickly, a homogeneous mass is obtained, similar to black or dark greenish glass (obsidian). 
Gas bubbles often leave many small cavities in viscous lava; This is how pumice is formed. Different layers of cooling lava flow down the slopes with at different speeds. Therefore, long, wide voids are formed inside the flow. The length of such tunnels sometimes reaches 15 km.
Slowly cooling lava forms a hard crust on the surface. It immediately slows down the cooling of the mass lying below, and the lava continues to move. In general, cooling depends on the massiveness of the lava, initial heating and composition. There are known cases when, even after several years (!), lava still continued to crawl and ignited branches stuck into it. Two massive lava flows in Iceland remained warm centuries after the eruption.
Lava from underwater volcanoes usually hardens in the form of massive “pillows”. Due to rapid cooling, a strong crust forms on their surface very quickly, and sometimes gases rupture them from the inside. The fragments scatter over a distance of several meters.
Why is lava dangerous for people?
The main danger of lava is its heat. It literally burns living beings and buildings along the way. Living things die without even coming into contact with it, from the heat with which it radiates. True, high viscosity inhibits the flow rate, allowing people to escape and preserve valuables.
But liquid lava... It moves quickly and can cut off the path to salvation. In 1977, during the night eruption of Mount Nyiragongo in Central Africa. The explosion split the crater wall, and lava gushed out in a wide stream. Very fluid, it rushed at a speed of 17 meters per second (!) and destroyed several sleeping villages with hundreds of inhabitants.
The damaging effect of lava is aggravated by the fact that it often carries clouds of toxic gases released from it, a thick layer of ash and stones. It was this kind of flow that destroyed the ancient Roman cities of Pompeii and Herculaneum. A meeting of hot lava with a body of water can result in a disaster - the instantaneous evaporation of a mass of water causes an explosion. 
Deep cracks and gaps form in the flows, so you need to walk on cold lava carefully. Especially if it is glassy - sharp edges and debris hurt painfully. Fragments of cooling underwater “pillows” described above can also injure overly curious divers.
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