“Mash, or thick ointment” (in Greek), it is a liquid molten hot rock of silicate nature. That's what magma is. It occurs in the earth's crust, in the upper mantle, at great depths. And when it cools, it forms characteristic rocks.
What is magma? Definition in dictionaries
In various sources, the word “magma” is interpreted as a mass of molten rock located under solid ground. They also point to its silicate composition and ability to form igneous rocks.
Origin
The fact is that the inside of the globe is hot. The heat melts the earth's rocks, which as a result are in a liquid state inside. What is magma? It is a liquid stone enclosed in a harder shell surrounding it. It is much lighter in weight than this shell. Therefore, it rises upward under the resulting pressure. Sometimes magma does not erupt outward, gradually cooling somewhere deep underground and hardening. This is how mountains are formed over thousands of years. Sometimes harder, cooler rocks cannot withstand the high pressure of magma from within. Cracks appear through which magma breaks out and pours out. It, still in a liquid state, spreads over the ground. 
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What happens next
What is magma that has reached the surface of the earth? It's called lava. After the magma has erupted, it immediately begins to cool, interacting with the external environment and the surrounding atmosphere. This happens quite quickly. Some substances included in its composition harden faster than others, forming crystals. These crystals seem to float in liquid rock. And the largest of them form mountains of lava. All these mountains are made up of numerous crystals embedded in basalt. They are called porphyry.
Chemical composition
What is magma from the point of view of the science of chemistry? This liquid rock contains many chemical elements. Among them are magnesium, sodium, iron, potassium. And also volatile components: chlorine, fluorine, hydrogen and others. And such a component as vaporous water. As volatile elements (their quantity) reach the surface, they are reduced, and a degassing process occurs. 
Classification
- Basalt (main). Contains silica (up to 50%), large quantities of magnesium, iron, aluminum, calcium. In a smaller volume - titanium and phosphorus, potassium and sodium.
- Granitic (acidic, rhyolite). Contains silica (up to 65%). It is more saturated with gases and has a lower density than basalt.
- Based on the nature of advancement and the method of solidification, several types of magmatism are distinguished. Intrusive type - magma solidifies and crystallizes deep in the depths without coming to the surface. Effusive type - magma erupts to the surface and solidifies there.
Hardening process
Molten magma consists of liquids, gases, and solid crystals that are in a certain equilibrium state. Under the influence of the environment, the volume of magma tends to evolve. Some mineral crystals melt, others re-emerge.
What does magma mean? This is a rather complex solution in which the precipitation of solid crystals obeys physical and chemical laws. But even in the same magma, the composition sometimes changes under the influence of temperature and pressure.
The flow speed of the erupting magma sometimes reaches 30 km/h, the temperature - up to 1250 degrees. In liquid form, magma remains at a temperature of approximately 600 degrees, and then begins to solidify.
At the same time, minerals crystallize and concentrate in certain areas of advancement, forming endogenous deposits of iron, non-ferrous and precious metals, and diamonds. These igneous formations occur in layered rock complexes.
What are magma and lava?
As already mentioned, lava is erupted magma, consisting of a viscous melt of rocks, mainly silicate. The main difference between the first and the second is that there are no gases in the lava, which evaporate when the “liquid stone” comes out. Lava tends to cool and solidify over time, stopping its progress. As a result, lava rocks are formed: mountains and even plateaus. Lava from different volcanoes varies in composition, temperature, and other characteristics. For example, carbonate lavas are brittle, soft, and easily dissolved in water. 
Volcanic eruptions
It only seems to us that the Earth is solid and motionless inside. In fact, deep inside there is a constant movement of molten substances - magma. It seeks access to the surface through all sorts of cracks and channels that appear in the Earth's crust. This is how volcanoes arise - magma that finds a way out erupts, sweeping away everything in its path. Of the most famous eruptions (recorded by science), the release of magma on the island of Krakatoa in 1883 can be noted. As a result, the island was completely destroyed. The eruption claimed more than 200 thousand human lives!
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Lava flowing out during volcanic eruptions often burns the clay with which it comes into contact. Fired clays are magnetized in the same way as vessels and bricks when fired.
Lavas differ from one another in their chemical composition, depending on the chemical composition of the magma. Lava is the same magma, but it has largely lost the gases dissolved in it during the eruption onto the surface of the earth.
Lava - 1) in mining - a clearing underground mine working with a long face in which minerals are extracted. It differs from magma in the absence of gases that escape during an eruption. Depending on the composition, when solidified, it forms various effusive rocks.
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Lava differs from magma in that it does not contain volatile components, which, when pressure drops, separate from the magma and escape into the atmosphere.
Lava differs from magma in the absence of gases that escape during an eruption.
Lava differs from magma in the absence of gases that escape during an eruption. Volcanoes (named after the god of fire, Vulcan) are geological formations that arise above channels and cracks in the earth's crust, through which magma erupts onto the earth's surface.
The lavas are characterized by intense fracturing. Cooling cracks give basaltic andesites a columnar appearance. Andesites and hyalodacites are characterized by platy separation.
Lava of the American Steel Corporation at a meeting of the Detroit Business Club: But it will require sacrifice; it will require patience; this will definitely require constant concern for productivity and investment.
Volcanic lava is magma that has risen from the depths along a volcanic crater or through cracks and frozen on the surface of the earth. Among the lava, well-formed crystals of many silicates are often found in the form of inclusions.
The volcanic lavas of basic and intermediate composition are massive, sometimes porous, strong and very strong. Tuffs and tuffites are strong. Siliceous rocks are also strong, massive, and have high strength. The sandstones are fine- and medium-grained, strong, and in places silicified. Sandstones and siltstones are characterized by thin and thick platy patterns.
Lav determined 0 005 - 0 04% W03 in ores against the background of 6 M HG1 from a 10 g sample. They do not interfere with the determination of Al, Ag, Au, B, Ba, Ca, Bi, Co, Cd, Gr, Fe, Hg, Mi, Mg, P, Pt, Rh, Sb, Sr, Ti, U, Zn, Zr; Ni, V, Sn, As, Pb, Cu, Mo interfere. In the presence of the latter, they are extracted from the ore (with the exception of tin) by treating the latter with nitric acid. The accuracy of the method is not inferior to the gravimetric method, based on the deposition of tungsten in the form of WOg-a; H20 and calcination to W03, and in terms of execution speed it is twice as fast.
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, at great depths, and upon cooling forms igneous rocks. Erupted magma is lava.
Types of magma
Basalt(mafic) magma appears to be more widespread. It contains about 50% silica, aluminum, calcium, iron and magnesium are present in significant quantities, and sodium, potassium, titanium and phosphorus are present in smaller quantities. Based on their 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(rhyolitic, 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
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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 of increased 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. The main distinctive features of 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. The chemical classification is based on the percentage of silica (SiO2) in the rock. According to this indicator, ultraacidic, acidic, medium, basic and ultrabasic rocks are distinguished. |
Volcanoes- separate elevations above channels and cracks in the earth's crust, through which eruption products are brought to the surface from deep magma chambers. Volcanoes usually have the shape of a cone with a summit crater (from several to hundreds of meters deep and up to 1.5 km in diameter). During eruptions, a volcanic structure sometimes collapses with the formation of a caldera - a large depression with a diameter of up to 16 km and a depth of up to 1000 m. As the magma rises, the external pressure weakens, associated gases and liquid products escape to the surface, and a volcanic eruption occurs. If ancient rocks, and not magma, are brought to the surface, and the gases are dominated by water vapor formed when groundwater is heated, then such an eruption is called phreatic. Active volcanoes include those that erupted in historical times or showed other signs of activity (emission of gases and steam, etc.). Some scientists consider active volcanoes that are reliably known to have erupted over the past 10 thousand years. For example, the Arenal volcano in Costa Rica should be considered active, since during archaeological excavations of a primitive man’s site in this area a volcanic volcano was discovered ash, although for the first time in human memory its eruption occurred in 1968, and before that no signs of activity appeared. Volcanoes are known not only on Earth. Images taken from spacecraft revealed huge ancient craters on Mars and many active volcanoes on. Io, the moon of Jupiter.
VOLCANIC PRODUCTS
Lava is magma that flows onto the earth's surface during eruptions and then hardens. Lava eruptions can come from the main summit crater, a side crater on the side of the volcano, or from fissures associated with a volcanic chamber. It flows down the slope as a lava flow. In some cases, lava outpourings occur in rift zones of enormous extent. For example, in Iceland in 1783, within the chain of Laki craters, stretching along a tectonic fault for a distance of about 20 km, an outpouring of -12.5 km3 of lava occurred, distributed over an area of -570 km2. Composition of lava: hard rocks formed when lava cools , contain mainly silicon dioxide, oxides of aluminum, iron, magnesium, calcium, sodium, potassium, titanium and water. Typically, lavas contain more than one percent of each of these components, and many other elements are present in smaller quantities.
There are many types of volcanic rocks, varying in chemical composition. Most often there are four types, the membership of which is determined by the content of silicon dioxide in the rock: basalt - 48-53%, andesite - 54-62%, dacite - 63-70%, rhyolite - 70-- 76%. Rocks that contain less silicon dioxide contain large amounts of magnesium and iron. When lava cools, a significant part of the melt forms volcanic glass, in the mass of which individual microscopic crystals are found. The exception is the so-called. phenocrystals are large crystals formed in magma in the depths of the Earth and brought to the surface by a flow of liquid lava. Most often, phenocrysts are represented by feldspars, olivine, pyroxene and quartz. Rocks containing phenocrysts are usually called porphyrites. The color of volcanic glass depends on the amount of iron present in it: the more iron, the darker it is. Thus, even without chemical analysis, one can guess that a light-colored rock is rhyolite or dacite, a dark-colored rock is basalt, and a gray rock is andesite. The type of rock is determined by the minerals visible in the rock. For example, olivine, a mineral containing iron and magnesium, is characteristic of basalts, quartz is characteristic of rhyolites.
As the magma rises to the surface, the released gases form tiny bubbles with a diameter often up to 1.5 mm, less often up to 2.5 cm. They are stored in the solidified rock. This is how they are formed bubbly lavas. Depending on the chemical composition of lavas, they vary in viscosity, or fluidity. With a high content of silicon dioxide (silica), lava is characterized by high viscosity. The viscosity of magma and lava largely determines the nature of the eruption and the type of volcanic products. Liquid basaltic lavas with low silica content form extensive lava flows more than 100 km long (for example, one lava flow in Iceland is known to stretch for 145 km). The thickness of lava flows is usually from 3 to 15 m. More liquid lavas form thinner flows. Flows 3-5 m thick are common in Hawaii. When the surface of a basalt flow begins to harden, its interior may remain liquid, continuing to flow and leaving behind an elongated cavity, or lava tunnel. For example, on about. Lanzarote (Canary Islands) a large lava tunnel can be traced for 5 km.
Surface lava flow It can be smooth and wavy (in Hawaii, such lava is called pahoehoe) or uneven (aalawa). Hot lava, which is highly fluid, can move at speeds of more than 35 km/h, but more often its speed does not exceed several meters per hour. In a slowly moving flow, pieces of the solidified upper crust can fall off and be covered by lava, “as a result, a zone enriched with fragments is formed in the bottom part. When lava hardens, columnar units (multifaceted vertical columns with a diameter of several centimeters to 3 m) or fracturing perpendicular to the cooling one are sometimes formed. surface. When lava flows into a crater or caldera, a lava lake is formed, which cools over time. For example, such a lake was formed in one of the craters of the Kilauea volcano on the island of Hawaii during the eruptions of 1967-1968, when lava entered this crater from. at a rate of 1.1 x 106 m3/h (part of the lava subsequently returned to the crater of the volcano). In the neighboring craters, within 6 months, the thickness of the solidified lava crust on the lava lakes reached 6.4 m.
Domes, maars and tuff rings. Very viscous lava (most often of dacite composition) during eruptions through the main crater or side fissures does not form flows, but a dome with a diameter of up to 1.5 km and a height of up to 600 m. For example, such a dome was formed in the crater of Mount St. Helens (USA) after an exceptionally strong eruption in May 1980. The pressure under the dome can build up, and weeks, months or years later it can be destroyed by the next eruption. In some parts of the dome, magma rises higher than in others, and as a result, volcanic obelisks protrude above its surface - blocks or spiers of solidified lava, often tens and hundreds of meters high. After the catastrophic eruption in 1902 of the Montagne Pelee volcano on the island. In Martinique, a lava spire formed in the crater, which grew by 9 m in a day and as a result reached a height of 250 m, and collapsed a year later. On the Usu volcano on the island. Hokkaido (Japan) in 1942, during the first three months after the eruption, the Showa-Shinzan lava dome grew by 200 m. The viscous lava that composed it made its way through the thickness of the previously formed sediments. Maar is a volcanic crater formed during an explosive eruption (most often with high humidity of the rocks) without the outpouring of lava. A ring shaft of debris ejected by the explosion is not formed, unlike tuff rings - also explosion craters, which are usually surrounded by rings of debris products.
