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 of the volcanoes of the Pacific Ring of Fire. Such lava is usually very viscous and sometimes freezes in the crater of a 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. 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, half - from aluminum oxide, iron, magnesium and other metals. 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.

Magma- is a natural, most often silicate, hot, liquid melt that occurs in the earth’s crust or in the upper mantle, on great depths, and when cooled forms igneous rocks. Erupted magma is lava.

Types of magma

Basalt(mafic) magma appears to be more widespread. It contains about 50% silica, in significant amount aluminum, calcium, iron and magnesium are present, with less sodium, potassium, titanium and phosphorus. By chemical composition basaltic magmas are divided into tholeiitic (supersaturated with silica) and alkali-basaltic (olivine-basaltic) magma (undersaturated with silica, but enriched with alkalis).

Granite(rhyolite, acidic) magma contains 60-65% silica, it has a lower density, is more viscous, less mobile, and is more saturated with gases than basaltic magma.

Depending on the nature of the movement of magma and the place where it solidifies, two types of magmatism are distinguished: intrusive And effusive. In the first case, magma cools and crystallizes at depth, in the bowels of the Earth, in the second - on the earth's surface or in near-surface conditions (up to 5 km).

11.Igneous rocks

Igneous rocks are rocks formed directly from magma (a molten mass of predominantly silicate composition), as a result of its cooling and solidification. According to the conditions of formation, two subgroups of igneous rocks are distinguished: intrusive(deep), from the Latin word “intrusio” - implementation; effusive(outpoured) from the Latin word “effusio” - outpouring. Intrusive(deep) rocks are formed during the slow gradual cooling of magma embedded in the lower layers of the earth's crust, under conditions high blood pressure and high temperatures. The release of minerals from the magma substance as it cools occurs strictly in a certain sequence; each mineral has its own temperature of formation. First, refractory dark-colored minerals are formed (pyroxenes, hornblende, biotite, ...), then ore minerals, then feldspars, and the last one is released in the form of quartz crystals. The main representatives of intrusive igneous rocks are granites, diorites, syenites, gabbros, and peridotites. Effusive(extrusive) rocks are formed when magma cools as lava on or near the surface of the Earth's crust. In terms of their material composition, effusive rocks are similar to deep rocks; they are formed from the same magma, but under different thermodynamic conditions (pressure, temperature, etc.). On the surface of the earth's crust, magma in the form of lava cools much faster than at some depth from it. The main representatives of effusive igneous rocks are obsidians, tuffs, pumice, basalts, andesites, trachytes, liparites, dacites, rhyolites. Basic features effusive (outpoured) igneous rocks, which are determined by their origin and conditions of formation: Most soil samples are characterized by a non-crystalline, fine-grained structure with individual crystals visible to the eye; Some soil samples are characterized by the presence of voids, pores, and spots; in some soil samples there is some pattern in the spatial orientation of the components (color, oval voids, etc.). Differences between effusive rocks and intrusive rocks rocks from each other are determined by the conditions of their formation and the material composition of the magma, which is manifested in their different colors (light - dark) and composition of components. At the core chemical classification is the percentage of silica (SiO2) in the rock. According to this indicator, ultra-acidic, acidic, medium, basic and ultrabasic rocks are distinguished.

Scientists have been interested in lava for a long time. Its composition, temperature, flow speed, shape of hot and cooled surfaces are all subjects for serious research. After all, both erupting and frozen streams are the only sources of information about the state of the interior of our planet, and they constantly remind us of how hot and restless these interiors are. As for the ancient lavas, which turned into characteristic rocks, the eyes of specialists are aimed at them with special interest: perhaps, behind the bizarre relief, the secrets of catastrophes on a planetary scale are hidden.

What is lava? According to modern ideas, it comes from a center of molten material, which is located in the upper part of the mantle (geosphere surrounding the Earth's core) at a depth of 50-150 km. While the melt remains in the depths under high pressure, its composition is homogeneous. Approaching the surface, it begins to “boil”, releasing gas bubbles that tend upward and, accordingly, move the substance along cracks in the earth’s crust. Not every melt, otherwise known as magma, is destined to see the light. The same one that finds its way to the surface, pouring out into the most incredible forms, is called lava. Why? Not quite clear. In essence, magma and lava are the same thing. In the “lava” itself one hears both “avalanche” and “collapse”, which, in general, corresponds to the observed facts: the leading edge of flowing lava often really resembles a mountain collapse. Only it’s not cold cobblestones that roll down from the volcano, but hot fragments that fly off the crust of the lava tongue.

Over the course of a year, 4 km 3 of lava pours out of the depths, which is quite a bit, considering the size of our planet. If this number were significantly larger, the processes would begin global change climate, which has happened more than once in the past. IN last years scientists are actively discussing the next scenario of the end catastrophe Cretaceous period, approximately 65 million years ago. Then, due to the final collapse of Gondwana, in some places the hot magma came too close to the surface and erupted in huge masses. Its outcrops were especially abundant on the Indian platform, which was covered with numerous faults up to 100 kilometers long. Almost a million cubic meters of lava spread over an area of ​​1.5 million km 2. In some places the covers reached a thickness of two kilometers, which is clearly visible from the geological sections of the Deccan Plateau. Experts estimate that the lava filled the area for 30,000 years - fast enough for large portions of carbon dioxide and sulfur-containing gases to separate from the cooling melt, reach the stratosphere and cause a decrease in the ozone layer. The subsequent dramatic climate change led to mass extinction of animals at the border of the Mesozoic and Cenozoic eras. More than 45% of the genera of various organisms have disappeared from the Earth.

Not everyone accepts the hypothesis about the influence of lava flow on climate, but the facts are clear: global extinctions of fauna coincide in time with the formation of extensive lava fields. So, 250 million years ago, when a mass extinction of all living things occurred, powerful eruptions occurred in Eastern Siberia. The area of ​​lava covers was 2.5 million km 2, and their total thickness in the Norilsk region reached three kilometers.

Black blood of the planet

The lavas that caused such large-scale events in the past are represented by the most common type on Earth - basalt. Their name indicates that they subsequently turned into a black and heavy rock - basalt. Basaltic lavas are half made of silicon dioxide (quartz), half of aluminum oxide, iron, magnesium and other metals. It is the metals that provide the high temperature of the melt - more than 1,200°C and mobility - the basalt flow usually flows at a speed of about 2 m/s, which, however, should not be surprising: this average speed running man. In 1950, during the eruption of the Mauna Loa volcano in Hawaii, the fastest lava flow was measured: its leading edge moved through sparse forest at a speed of 2.8 m/s. When the path is paved, the following streams flow, so to speak, in hot pursuit much faster. Merging, lava tongues form rivers, in the middle reaches of which the melt moves at high speed - 10–18 m/s.

Basaltic lava flows are characterized by small thickness (a few meters) and long distance(tens of kilometers). The surface of flowing basalt most often resembles a bunch of ropes stretched along the movement of lava. It is called the Hawaiian word "pahoehoe", which, according to local geologists, does not mean anything other than a specific type of lava. More viscous basaltic flows form fields of sharp-angled, spike-like lava fragments, also called "aa lavas" in Hawaiian fashion.

Basaltic lavas are not only common on land; they are even more common in the oceans. The ocean floors are large slabs of basalt 5–10 kilometers thick. According to American geologist Joy Crisp, three-quarters of all lavas erupting on Earth each year come from underwater eruptions. Basalts constantly flow from the cyclopean ridges that cut through the ocean floors and mark the boundaries of lithospheric plates. No matter how slow the plate movement, it is accompanied by strong seismic and volcanic activity on the ocean floor. Large masses of melt coming from ocean faults do not allow the plates to become thinner, they are constantly growing.

Underwater basalt eruptions show us another type of lava surface. As soon as the next portion of lava splashes out to the bottom and comes into contact with water, its surface cools down and takes the form of a drop - a “pillow”. Hence the name - pillow lava, or pillow lava. Pillow lava forms whenever molten material enters a cold environment. Often during a subglacial eruption, when the flow rolls into a river or other body of water, the lava solidifies in the form of glass, which immediately bursts and crumbles into plate-like fragments.

Vast basalt fields (traps) hundreds of millions of years old hide even more unusual shapes. Where ancient traps come to the surface, as, for example, in the cliffs of Siberian rivers, you can find rows of vertical 5- and 6-sided prisms. This is a columnar separation that is formed during the slow cooling of a large mass of homogeneous melt. Basalt gradually decreases in volume and cracks along strictly defined planes. If the trap field, on the contrary, is exposed from above, then instead of pillars, surfaces appear as if paved with giant paving stones - “pavements of giants”. They are found on many lava plateaus, but the most famous are in the UK.

Neither heat, nor the hardness of solidified lava does not serve as an obstacle to the penetration of life into it. In the early 90s of the last century, scientists found microorganisms that settle in basalt lava that erupted at the bottom of the ocean. As soon as the melt cools down a little, the microbes “gnaw” passages in it and establish colonies. They were discovered by the presence in basalts of certain isotopes of carbon, nitrogen and phosphorus - typical products released by living beings.

The more silica in lava, the more viscous it is. The so-called medium lavas, with a silicon dioxide content of 53–62%, no longer flow as fast and are not as hot as basaltic lavas. Their temperature ranges from 800 to 900°C and their flow speed is several meters per day. The increased viscosity of lava, or rather magma, since the melt acquires all its basic properties at depth, radically changes the behavior of the volcano. From viscous magma, it is more difficult to release the gas bubbles accumulated in it. On approaching the surface, the pressure inside the bubbles in the melt exceeds the pressure on them outside and the gases are released with an explosion.

Typically, a crust forms at the leading edge of the more viscous lava tongue, which cracks and crumbles. The fragments are immediately crushed by the hot mass pressing behind them, but do not have time to dissolve in it, but harden like bricks in concrete, forming a rock with a characteristic structure - lava breccia. Even after tens of millions of years, lava breccia retains its structure and indicates that a volcanic eruption once occurred in this place.

In the center of Oregon, USA, there is the Newberry volcano, which is interesting because of its lavas of intermediate composition. Last time it became active more than a thousand years ago, and at the final stage of the eruption, before falling asleep, a lava tongue 1,800 meters long and about two meters thick flowed out of the volcano, frozen in the form of pure obsidian - black volcanic glass. Such glass is obtained when the melt cools quickly without having time to crystallize. Additionally, obsidian is often found on the periphery of a lava flow, which cools faster. Over time, crystals begin to grow in the glass and it turns into one of the acidic or intermediate rocks. That is why obsidian is found only among relatively young eruption products; it is no longer found in ancient volcanics.

From damn fingers to fiamme

If the amount of silica occupies more than 63% of the composition, the melt becomes completely viscous and clumsy. Most often, such lava, called acidic, is not able to flow at all and solidifies in the supply channel or is squeezed out of the vent in the form of obelisks, “devil’s fingers,” towers and columns. If the acidic magma still manages to reach the surface and pour out, its flows move extremely slowly, several centimeters, sometimes meters per hour.

Unusual rocks are associated with acidic melts. For example, ignimbrites. When the acidic melt in the near-surface chamber is saturated with gases, it becomes extremely mobile and is quickly ejected from the vent, and then, together with tuffs and ash, flows back into the depression formed after the ejection - the caldera. Over time, this mixture hardens and crystallizes, and large lenses of dark glass clearly stand out against the gray background of the rock in the form of irregular shreds, sparks or flames, which is why they are called “fiamme”. These are traces of the stratification of the acidic melt when it was still underground.

Sometimes acidic lava becomes so saturated with gases that it literally boils and becomes pumice. Pumice is a very light material, with a density lower than that of water, so it happens that after underwater eruptions, sailors observe entire fields of floating pumice in the ocean.

Many questions related to lavas remain unanswered. For example, why lavas of different compositions can flow from the same volcano, as, for example, in Kamchatka. But if in this case there are at least convincing assumptions, then the appearance of carbonate lava remains a complete mystery. It, half consisting of sodium and potassium carbonates, is currently erupted by the only volcano on Earth - Oldoinyo Lengai in Northern Tanzania. The melt temperature is 510°C. This is the coldest and most liquid lava in the world, it flows along the ground like water. The color of hot lava is black or dark brown, but after just a few hours of exposure to air, the carbonate melt becomes lighter, and after a few months it becomes almost white. Frozen carbonate lavas are soft and brittle and easily dissolve in water, which is probably why geologists do not find traces of similar eruptions in ancient times.

Lava plays a key role in one of the most pressing problems of geology - what heats up the Earth's interior. Why do pockets of molten material appear in the mantle, which rise upward, melt through the earth's crust and give rise to volcanoes? Lava is only a small part of a powerful planetary process, the springs of which are hidden deep underground.

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 dark shade. 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.