Parting

Boiling temperature of lava. Types of volcanic eruptions. Long lasting effects of a volcanic eruption

When volcanoes erupt, hot molten rocks are poured out - magma. In air, the pressure drops sharply, and the magma boils - gases leave it.

The melt begins to cool. In fact, it is only these two properties - temperature and "carbonation" - that lava differs from magma. For a year on our planet, mainly at the bottom of the oceans, 4 km³ of lava spills. 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°С 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 temperature and composition, lava comes in different colors, viscosities, and fluidity. Hot, she is brilliant bright yellow and orange; cooling, it turns red, and then black. It happens that blue lights of burning sulfur run over 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 clumsy, barely flows (several centimeters or meters per hour). Hardening blocks form in it along the way. They slow down even more. Such lava freezes in mounds. But the absence of silicon dioxide (quartz) in lava makes it very liquid. It quickly covers vast fields, forms lava lakes, flat-surfaced rivers, 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 the cooling went 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 at different speeds. Therefore, long wide voids are formed inside the stream. The length of such tunnels sometimes reaches 15 km.

Slowly cooling lava forms a hard crust on the surface. That 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 cases when even after a few years (!) the lava still continued to creep and ignited the branches stuck into it. Two powerful lava flows in Iceland remained warm for centuries after the eruption.

The lava of underwater volcanoes usually solidifies in the form of massive "pillows". Due to rapid cooling, a strong crust forms on their surface very quickly, and sometimes gases tear them apart 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 high temperature. It literally burns living creatures and buildings on the way. The living dies, without even coming into contact with it, from the heat with which it exudes. True, high viscosity restrains the flow rate, allowing people to escape, to save valuables.

But liquid lava ... It moves quickly and can cut off the path to salvation. In 1977, during the nighttime eruption of the Nyiragongo volcano in Central Africa. The explosion cracked the wall of the crater, 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 poisonous gases released from it, a thick layer of ash and stones. It was this stream that destroyed the ancient Roman cities of Pompeii and Herculaneum. A catastrophe can turn into a meeting of red-hot lava with a reservoir - the instantaneous evaporation of a mass of water causes an explosion.

Deep cracks and dips form in the flows, so you have to be careful when walking on cold lava. Especially if it is vitreous - sharp edges and fragments hurt painfully. Fragments of cooling underwater "pillows", described above, can also injure overly curious divers.

» Lava Movement

The speed of lava movement is different, depending on its density and on the slope of the area where it makes its way. Relatively small lava flows pouring down steep slopes move forward extremely rapidly; the stream thrown out 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. traveled 8 miles during this time. Especially liquid lavas are released by open basaltic volcanoes of the island of Hawaii; they are so mobile that they form real lava falls on cliffs and can move with the slightest slope of the soil, even in G. It has been repeatedly observed how these lavas traveled 10-20 and even 30 km per hour. But such rapidity of movement is, in any case, one of the exceptions; even the lava observed by Scrope in 1822 and which, within 15 minutes, managed to descend from the edge of the crater of Vesuvius to the foot of the cone, is far from ordinary. On Etna, the movement of lava is already 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.

Lava flowing out of the volcano in a molten state has a white-hot luster and retains it for a long time inside the crater: this can be clearly seen where, due to cracks, deep parts of the stream are exposed. Outside the crater, the lava cools rapidly, and the flow is soon covered with a hard crust, consisting of a dark slag mass; within a short time it becomes so strong that a person can safely walk on it; sometimes on such a crust, covering a still moving stream, one can climb to the point where the lava flows out. Solid slag crust forms something like a pipe, inside which a 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 further along it, being covered in front by a new slag shell. This phenomenon does not occur only with very fast lava movement; in other cases, by dropping and moving the slag, a layer of solidified lava is formed, along which the flow moves. The latter presents a rare sight: the front of his Machine Scrope compares to a huge heap of coals, which, under the influence of some pressure from behind, are heaped on top of each other. Its movement is accompanied by a noise like that of pouring metal; this noise is due to the friction of individual lumps of lava, their fragmentation and contraction.

The hard crust of a lava flow usually does not present a flat surface; it is covered with many cracks through which liquid lava sometimes flows; blocks formed as a result of the 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 is the form of the so-called wavy lava, which is observed less often, but is well known to every visitor to Vesuvius. The road from Rezina to the observatory was laid for a considerable distance along such a lava; the latter was thrown out by Vesuvius in 1855. The cover of such streams does not break into pieces, but is a continuous mass, the uneven surface of which, with its peculiar appearance, resembles intestinal plexuses.

Lava is a hot molten mass of rocks that is ejected to the surface of the Earth during volcanic eruptions. Depending on the species, lava can be liquid or viscous, of different colors and temperatures.

In fact, the volcano erupts magma from the upper mantle at a depth of about 700 km, but during the eruption it cools down, and its gases escape, which changes its properties. When lava solidifies, various effusive rocks are formed.

In Latin, "labes" means collapse or fall. Hence the word "lava" in Italian and its use in Russian.

Types of lava

Different volcanoes erupt lava with different characteristics.

Carbonate lava is the coldest and most liquid, flowing like water. It is black or dark brown when erupted, but becomes lighter when exposed to air until it turns almost white.
Silicon lava is very viscous and for this reason it sometimes freezes in the vent of the volcano and blows it up. Therefore, when the eruption is restored, there is a strong explosion. Hot silicon lava of dark or black-red color. It flows at a speed of several meters a day and after solidification turns black.
Basalt lava has the highest temperature and is very mobile. It can flow at a speed of 2 m / s, due to which a small layer can spread over tens of kilometers. It has a yellow or yellow-red color.

You learned what lava is, but also read the article

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 4,600 meters, undoubtedly occurred as a 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. "white mountain") reaches from the bottom of the ocean 8828 meters (relative height of the volcano 4228 meters). The most famous are Mauna Loa, otherwise the "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 bubbling 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. Another natural lighthouse is widely known among sailors all over the world, in Central America off the coast of El Salvador - the Tsalco volcano. 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

The most complete picture of the eruption is given by volcanoes of the 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 emitted not only through the crater, but also from the fumaroles (fumarole is a derivative of the 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 a dark night. Strong electrical stress from the friction of ash particles and vapors is manifested 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 a certain shape. They acquire a rounded or spindle-shaped shape by rotating during flight.

Volcanic bomb of spherical shape - a sample from Vesuvius;
Trass - porous trachyte tuff - specimen from Eichel, Germany;
Spindle-shaped volcanic bomb - a sample from Vesuvius;
Lapilli - small volcanic bombs;
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 of a terrible explosion, a significant part of the cone is suddenly sprayed into the air, covering the sunlight with an impenetrable haze. 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.

Bandai-san volcano. 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 was replaced by a dark night ... No liquid lava was released.

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, seem to be maar-like in nature.

lava type

Silica content is classified lavas acidic and basic. In the first, its amount reaches 76%, and in the second, it does not exceed 52%. 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

The chemical composition of lava is different not only for volcanoes of different types, but also for the same volcano, depending on the periods of eruptions. For example, Vesuvius in modern times, it pours out light (acidic) trachytic lavas, while the more ancient part of the volcano, the so-called Somme, is composed of heavy basaltic lavas.

lava movement speed

Medium lava movement speed- five kilometers per hour, but in some 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 a cold November and a strong wind was blowing, however, even in asbestos boots, the legs still got so hot that they had to alternately stand on one or the other foot in order to cool the sole 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 °. 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 fresh lava flow. The outpouring of lava occurs not only through volcanoes, but also through deep cracks in the earth's crust. Iceland has lava flows frozen between layers of snow or ice. Lava filling the cracks and voids of the earth's crust can maintain its temperature for many hundreds of years, which explains the presence of hot springs in volcanic areas.

In today's article, we will look at the types of lava by temperature and its viscosity.

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

The outer shell of the globe is the earth's crust, beneath which lies a hot, liquid layer called the mantle. Red-hot magma through cracks in the earth's crust, makes its way up.

The entry points of red-hot magma into the earth's surface are called "hot spots", which means hot spots in translation.

(pictured left). This usually occurs within the boundaries between tectonic plates and gives rise to entire volcanic chains.

What is the temperature of lava?

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

Liquid lava has the highest temperature, more than 950C, 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 spewing 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 frozen rounded blocks, with a broken crust.

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

Below we will give you some photos of red-hot lava.