Melting temperature of lava. Types of volcanic eruptions. Surface of the earth covered with volcanoes

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. The centers of earthquakes are located approximately at a depth of up to 700 km from the 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 oceanic crust moves under the 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 small thickness (a few meters) and long distance(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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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. Complete dictionary 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

» Lava movement

The speed of lava movement varies depending on its density and the slope of the terrain where it makes its way. Relatively small lava flows flowing down steep slopes move forward extremely quickly; a stream ejected by Vesuvius on August 12, 1805, rushed along the steep slopes of the cone with amazing speed and in the first four minutes made 5 ½ km, and in 1631 another stream of the same volcano reached the sea within one hour, i.e. walked 8 km at this time. Particularly liquid lavas are produced by open basaltic volcanoes on the island of Hawaii; they are so mobile that they form real lava falls on the cliffs and can move with the slightest slope of the soil, even in the mountains. It has been repeatedly observed how these lavas passed 10-20 and even 30 km per hour. But such speed of movement belongs, in any case, to the number of exceptions; even the lava that Scrope observed in 1822 and which managed to descend from the edge of the crater of Vesuvius to the foot of the cone within 15 minutes is far from ordinary. On Etna, lava movement is considered fast if it occurs at a speed of 1 km in 2-3 hours. Usually lava moves even more slowly and in some cases only moves 1 m per hour.

The lava flowing out of the volcano in a molten state has a white-hot sheen and inside the crater retains it for a long time: this can be clearly seen where, thanks to cracks, the deep parts of the flow are exposed. Outside the crater, the lava quickly cools, and the flow is soon covered with a hard crust consisting of a dark cinder mass; within a short time it becomes so strong that a person can calmly walk on it; sometimes along such a crust covering a still moving flow, you can climb to the place where the lava flows out. The solid slag crust forms something like a pipe, inside which the liquid mass moves. The front end of the lava flow is also covered with black, hard crust; with further movement, the lava presses this crust to the ground and flows along it further, becoming covered in front with a new slag shell. This phenomenon does not occur only when the lava moves very quickly; in other cases, by dumping and moving slag, a layer of solidified lava is formed, along which the flow moves. The latter presents a rare sight: the front part of it is compared by Pulet Scroop to a huge pile of coals, which, under the influence of some pressure from behind, are piled on top of each other. Its movement is accompanied by a noise similar to the ringing of spilling metal; this noise occurs due to the friction of individual lumps of lava, their fragmentation and contraction.

The hard crust of a lava flow usually does not have a flat surface; it is covered with many cracks through which liquid lava sometimes flows; blocks formed as a result of fragmentation of the original cover collide with each other, like ice floes during ice drift. It is difficult to imagine a wilder and more gloomy picture than that presented to us by the outer surface of a blocky lava flow. Even more peculiar are the forms of the so-called wavy lava, which is observed less frequently, but is well known to every visitor to Vesuvius. The road from Rezina to the observatory was laid over such lava for a considerable distance; the latter was thrown out by Vesuvius in 1855. The cover of such flows is not broken into pieces, but represents a continuous mass, the uneven surface of which, in its peculiar appearance, resembles intestinal plexuses.

In today's article we will look at the types of lava based on temperature and viscosity.

As you probably know, lava is molten rock that erupts from an active volcano onto the surface of the earth.

Outer shell globe– the earth’s crust, underneath it hides a hot, liquid layer called the mantle. Hot magma makes its way to the top through cracks in the earth's crust.

Entry points of hot magma into earth's surface called “hot spots”, which means hot spots

What is the temperature of the lava?

Lava has a temperature of 700 to 1200C. Depending on the temperature and composition, lava is divided into three types of fluidity.

Liquid lava has the highest temperature, more than 950C, and its main component is basalt. With such a high temperature and fluidity, lava can flow for several tens of kilometers before it stops and hardens. Volcanoes that erupt this type of lava are often very gentle, since it does not linger at the vent, but spreads around.

Lava with a temperature of 750-950C is andesitic. It can be recognized by its frozen round blocks with a broken crust.

Lava with the lowest temperature of 650-750C is acidic and very rich in silica. A characteristic feature This lava has slow speed and high viscosity. Very often, during an eruption, this type of lava forms a crust over the crater (pictured on the right). Volcanoes with this temperature and type of lava often have steep slopes.

Below we will show you some photos of hot lava.

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 has a 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 found 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.

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 can be different color, 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?

Main danger lava - her 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.

Lethal effect 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.