Meteorites are characterized by the presence of both oxidized and metallic iron. The first is included in the iron-magnesium silicates that form the basis of the rocky substance of meteorites, and the second is represented by nickel iron, found in the form of inclusions. Oxidized and metallic iron coexists in very different proportions: along with iron meteorites, consisting of almost pure metal, there are meteorites containing up to 10-20% ferrosilicates; Stone-iron meteorites contain metal and ferrosilicate in approximately equal quantities. Along with stony meteorites that contain no or almost no metal (achondrites and some types of chondrites), there are chondrites in which only metallic inclusions make up 30% of their mass. The following pattern is observed in chondrites (Pryor’s law): the fewer metal inclusions they contain, the richer these inclusions are in nickel and the richer the iron-magnesium silicates are in iron. The established patterns may be due to the different thermal history of metal grains before the agglomeration of chondritic matter into a meteorite body. Apparently, small metal particles were transformed into large ones before the formation of single chondrite bodies.
There is no doubt that meteorites falling to Earth are fragments of larger bodies. Most researchers believe that meteorites come from the asteroid belt located between the orbits of Mars and Jupiter, which is confirmed by calculations of the orbits of the Pshibram meteorite body and the Sikhote-Alin meteorite. The number of asteroids is very large: about 55,000 of them have a diameter of more than 1 km, the largest - Ceres - 770 km across. The total mass of the asteroid ring is estimated to be about 1/10 the mass of the Moon or 1/100 the mass of the Earth. Asteroids, moving in intersecting orbits, are fragmented; Moreover, their fragmentation and scattering of fragments, which later became meteorites, were often preceded by collisions that were not accompanied by scattering, but traces of which were preserved in the structure of the substance. The latter indicates a shock pressure of more than 10 10 Pa, which led, in particular, to the formation of diamonds in some meteorites. Calculations show that during the existence of the Earth (4.5 billion years), approximately 30% of asteroids turned into small fragments and dust - approximately 10 10 tons per year. Of this amount, several thousand tons fall to Earth annually in the form of meteorites and cosmic dust.
The chemical composition of meteorites consists of the same elements as terrestrial rocks, although their ratios are often unusual from an “earthly” point of view. However, in meteorites, as on Earth, the most common are the first nine elements, which, combining with each other in various proportions, form the main minerals of meteorites. At the same time, oxygen is present in meteorites in the form of chemical compounds with other elements, forming mainly anhydrous silicates, and water is contained in noticeable quantities only in carbonaceous chondrites. In general, meteorite matter is characterized by three main phases: silicate (74.7%), troilite (5.7%) and iron-nickel (19.6%). These values come from analyzes of ordinary chondrites, which are the most common meteorites and the least differentiated compared to other types of meteorites. Therefore, many researchers, following G. Urey, believe that chondrites are most consistent with the average composition of meteorite matter. Table 1 gives an idea of how different groups of stony meteorites differ in composition. 9, reflecting variations only in groups of chondrites. The achondrite groups of iron and stony-iron meteorites also differ in a similar way.
It should be borne in mind that meteorites are extremely inhomogeneous in phase composition; within each of their main phases there are a large number of different minerals, and the distribution of trace elements is very uneven even within grains of the same mineral. So, if ordinary chondrites lack many elements, sometimes 10-1000 times, compared with their cosmic abundance and content in the Earth as a whole, then in enstatite and carbonaceous chondrites of type I the same elements (Hg, Tl, Pb, Bi, etc.) turned out to be just as much as required (Table 10). In table 10 includes those elements whose prevalence varies from group to group by more than two times. Deficient elements in carbonaceous chondrites of types II and III are, as a rule, less common than in type I. In ordinary chondrites, the fractionation pattern is more complex compared to carbonaceous ones: manganese and alkali metals, with the exception of cesium, do not show a noticeable deficiency; the abundance of elements such as Cu, Au, Ga, Ge, Sn, Sb, F, Sn, Se is four times less than in type I carbonaceous chondrites, and 13 elements are Cs, Le, Ag, CI, Br, Y , Zn, Cd, Hg, Pb, Bi, Tl and Tn - 10-500 times less. In many cases, type I enstatite chondrites are similar to carbonaceous ones, but on average the abundance of volatiles in them is approximately 2/3 of their abundance in type I carbonaceous ones, with the exception of mercury and atmophilic elements, which is explained by their extremely high volatility. Type II enstatite chondrites behave similarly to ordinary chondrites. In Fig. Figure 9 shows the periodic table of D.I. Mendeleev, on which those elements that are lacking in ordinary chondrites in comparison with their cosmic abundance or their concentration varies greatly from sample to sample are indicated by shading. All elements of transition groups turn out to be “normal”, with the exception of manganese: all “abnormal” elements have only one common property - they are all volatile to one degree or another.
Let's talk about how a meteor differs from a meteorite in order to understand the mystery and uniqueness of the starry sky. People trust the stars with their most cherished desires, but we will talk about other celestial bodies.
Meteor Features
The concept of “meteor” is associated with phenomena occurring in the earth’s atmosphere, during which foreign bodies invade it at a significant speed. The particles are so small that they are quickly destroyed by friction.
Do meteors get hit? The description of these celestial bodies offered by astronomers is limited to indicating a short-term luminous strip of light in the starry sky. Scientists call them "shooting stars."
Characteristics of meteorites
A meteorite is the remains of a meteoroid that falls on the surface of our planet. Depending on the composition, there is a division of these celestial bodies into three types: stone, iron, iron-stone.
Differences between celestial bodies
How is a meteor different from a meteorite? This question remained a mystery for astronomers for a long time, a reason for conducting observations and research.
Meteors lose their mass after entering the earth's atmosphere. Before the combustion process, the mass of this celestial object does not exceed ten grams. This value is so insignificant in comparison with the size of the Earth that there will be no consequences from the fall of a meteor.
Meteorites that fall on our planet have significant weight. The Chelyabinsk meteorite, which fell to the surface on February 15, 2013, according to experts, weighed about ten tons.
The diameter of this celestial body was 17 meters, the speed of movement exceeded 18 km/s. The Chelyabinsk meteorite began to explode at an altitude of about twenty kilometers, and the total duration of its flight did not exceed forty seconds. The power of the explosion was thirty times greater than the bomb explosion in Hiroshima, resulting in the formation of numerous pieces and fragments that fell onto the Chelyabinsk soil. So, discussing how a meteor differs from a meteorite, first of all, let’s note their mass.
The largest meteorite was an object discovered at the beginning of the twentieth century in Namibia. Its weight was sixty tons.
Drop Frequency
How is a meteor different from a meteorite? Let's continue the conversation about the differences between these celestial bodies. Hundreds of millions of meteors are observed in the earth's atmosphere in just one day. In case of clear weather, you can observe about 5-10 “shooting stars”, which are actually meteors, in an hour.
Meteorites also quite often fall on our planet, but most of them burn up during the journey. Several hundred of these celestial bodies hit the surface of the earth every day. Due to the fact that most of them land in the desert, seas, and oceans, they are not discovered by researchers. Scientists manage to study only a small number of these celestial bodies per year (up to five). When answering the question of what meteors and meteorites have in common, we can note their composition.
Fall hazard
Small particles that make up a meteoroid can cause serious harm. They render the surface of spacecraft unusable and can disable the operation of their energy systems.
It is difficult to assess the real danger that meteorites pose. After their fall, a huge number of “scars” and “wounds” remain on the surface of the planet. If such a celestial body is large, after it hits the Earth, its axis may shift, which will negatively affect the climate.
In order to fully appreciate the scale of the problem, we can give an example of the fall of the Tunguska meteorite. It fell into the taiga, causing serious damage to an area of several thousand square kilometers. If this territory were inhabited by people, one could talk about a real catastrophe.
A meteor is a light phenomenon that is often observed in the starry sky. Translated from Greek, this word means “heavenly.” A meteorite is a solid body of cosmic origin. Translated into Russian, this term sounds like “stone from the sky.”
Scientific research
In order to understand how comets differ from meteorites and meteorites, let’s analyze the results of scientific research. Astronomers were able to find out that after a meteor hits the earth's atmosphere, it flares up. During the combustion process, a luminous trail remains, consisting of meteor particles that fade away at approximately an altitude of seventy kilometers from the comet, leaving a “tail” in the starry sky. Its basis is the core, which includes dust and ice. In addition, the comet may contain the following substances: carbon dioxide, ammonia, organic impurities. The dust tail that it leaves as it moves consists of particles of gaseous substances.
Once in the upper layers of the Earth's atmosphere, fragments of destroyed cosmic bodies or dust particles heat up from friction and flare up. The smallest of them immediately burn out, and the larger ones, continuing to fall, leave behind a glowing trail of ionized gas. They go out, reaching a distance of approximately seventy kilometers from the surface of the earth.
The duration of the flare is determined by the mass of this celestial body. If large meteors burn up, you can admire the bright flashes for several minutes. It is this process that astronomers call star rain. In the event of a meteor shower, about a hundred burning meteors can be seen in one hour. If the celestial body is large in size, in the process of moving through the dense earth's atmosphere, it does not burn up and falls on the surface of the planet. No more than ten percent of the initial weight of the meteorite reaches the Earth.
Iron meteorites contain significant amounts of nickel and iron. The basis of rocky celestial bodies are silicates: olivine and pyroxene. Ironstone bodies have almost equal amounts of silicates and nickel iron.
Conclusion
People at all times of their existence have tried to study celestial bodies. They made calendars based on the stars, determined weather conditions, tried to predict destinies, and were afraid of the starry sky.
After the advent of various types of telescopes, astronomers managed to unravel many secrets and mysteries of the starry sky. Comets, meteors, and meteorites were studied in detail, and the main distinctive and similar features between these celestial bodies were determined. For example, the largest meteorite that hit the surface of the earth was the iron Goba. Scientists discovered it in Young America; its weight was about sixty tons. Halley's comet is considered the most famous in the solar system. It is precisely this that is associated with the discovery of the law of universal gravitation.
They can be large and small, inconspicuous and terrifying, iron and silicate, the most diverse. The scientific name for a shooting star is meteorite. This definition applies to bodies larger than 10 microns. Smaller space guests are called micrometeorites.
What are meteorites?
Almost 93% of meteorites are stony. Among them there are chondrites consisting of silicate spheres (ordinary, carbonaceous and enstatine), and achondrites that have undergone melting and the accompanying differentiation in composition into silicates and metals. The remaining bodies are divided into iron-stone (pallasites and mesosiderites) and pure iron.
It is important to note that a meteorite is not a meteor. These concepts mean different things. A meteorite is the body itself, and a meteor is the fiery trail formed in the atmosphere during its fall. It is he who is mistaken for a “shooting star” on which romantically minded individuals make wishes.
Meteorites can vary in size. Some of them are as small as a grain of sand, others reach tens of tons. Representatives of the scientific world claim that during the year 21 tons of extraterrestrial bodies hit our planet, while representatives of the stream can weigh from a few grams to 1000 kilograms.
The largest meteorites in Earth's history
Sutter Mill fell to Earth on April 22, 2012. Its path ran over Nevada and California, and its speed exceeded 29 kilometers per second. Over these states, parts of different sizes broke off from the meteorite, but the main part reached Washington and exploded right above it. The force of the explosion turned out to be equal to 4000 tons. Scientists know the age of the celestial wanderer - more than 4500 million years.
In Peru, not far from and near the Bolivian border, in 2007 there was a fall of a cosmic body, the fragments of which were not found. What happened is evidenced only by a pit 6 meters deep and 30 meters in diameter, filled with muddy water. At the time of the incident, according to local residents, water boiled like a fountain. There is a version that there were toxic substances in it, since after its fall, eyewitnesses began to have severe migraines.
In June 1998, on the 20th, a space guest weighing 820 kg landed on a cotton field near the Turkmen city of Kunya-Urgench. The diameter of the funnel was about 5 meters. The International Meteor Society calculated the age of the body - more than 4 billion years - and recognized it as the largest of all that fell in the CIS, and the third largest in the world.
On a May night in 1990, from the 17th to the 18th, a 315-kilogram meteorite fell twenty kilometers from Sterlitamak. This event occurred on a state farm field, in the soil of which a 10-meter crater formed. At the same time, the cosmic body itself was immersed 12 m deep into the earth.
The Namibian meteorite is considered the largest found. This iron miracle bears the name Goba and has a volume of 9 cubic meters and a weight of 66 tons. Its fall occurred 80,000 years ago, but this ingot was discovered only in 1920. Now it is a local landmark.
, meteoroid, asteroid, their fragments, or other meteoroids.
A celestial body flying through the Earth's atmosphere and leaving a bright luminous trail in it, regardless of whether it flies through the upper layers of the atmosphere and goes back into outer space, burns up in the atmosphere, or falls to Earth, can be called either a meteor or a bolide . Meteors are considered bodies no brighter than 4th magnitude, and fireballs - brighter than 4th magnitude, or bodies whose angular dimensions are distinguishable.
A solid body of cosmic origin that fell to the surface of the Earth is called a meteorite.
A crater (astrobleme) may form at the site where a large meteorite falls. One of the most famous craters in the world is Arizona. It is assumed that the largest meteorite crater on Earth is Wilkes Earth Crater (diameter about 500 km).
Other names for meteorites: aerolites, siderolites, uranolites, meteorolites, baituloi, sky, air, atmospheric or meteor stones, etc.
Phenomena similar to the fall of a meteorite on other planets and celestial bodies are usually called simply collisions between celestial bodies.
The process of meteorites falling to Earth
The meteor body enters the Earth's atmosphere at a speed of about 11-25 km/sec. At this speed, it begins to warm up and glow. Due to ablation (burning and blowing away by the oncoming flow of particles of the meteoroid body), the mass of the body that reaches the ground may be less, and in some cases significantly less than its mass at the entrance to the atmosphere. For example, a body that enters the Earth's atmosphere at a speed of 25 km/s or more burns up almost completely. At such a speed of entry into the atmosphere, out of tens and hundreds of tons of initial mass, only a few kilograms or even grams of matter reach the ground. Traces of the combustion of a meteoroid in the atmosphere can be found along almost the entire trajectory of its fall.
If the meteor body does not burn up in the atmosphere, then as it slows down it loses the horizontal component of its speed. This results in a change in the trajectory of the fall from often almost horizontal at the beginning to almost vertical at the end. As it slows down, the glow of the meteorite decreases and it cools down (they often indicate that the meteorite was warm and not hot when it fell).
In addition, the meteor body may break into fragments, resulting in a Meteor Shower.
Classification of meteorites
Classification by composition
- stone
- chondrites
- carbonaceous chondrites
- ordinary chondrites
- enstatite chondrites
- chondrites
- iron-stone
- palasites
- mesosiderites
- iron
The most common meteorites are stony meteorites (92.8% of falls). They consist mainly of silicates: olivines (Fe, Mg)2SiO4 (from fayalite Fe2SiO4 to forsterite Mg2SiO4) and pyroxenes (Fe, Mg)SiO3 (from ferrosilite FeSiO3 to enstatite MgSiO3).
The vast majority of stony meteorites (92.3% of stony meteorites, 85.7% of total falls) are chondrites. They are called chondrites because they contain chondrules - spherical or elliptical formations of predominantly silicate composition. Most chondrules are no more than 1 mm in diameter, but some can reach several millimeters. Chondrules are found in a detrital or finely crystalline matrix, and often the matrix differs from chondrules not so much in composition as in crystalline structure. The composition of chondrites almost completely replicates the chemical composition of the Sun, with the exception of light gases such as hydrogen and helium. Therefore, it is believed that chondrites formed directly from the protoplanetary cloud that surrounded and surrounded the Sun, through the condensation of matter and the accretion of dust with intermediate heating.
Achondrites make up 7.3% of stony meteorites. These are fragments of protoplanetary (and planetary?) bodies that have undergone melting and differentiation by composition (into metals and silicates).
Iron meteorites are composed of an iron-nickel alloy. They account for 5.7% of falls.
Iron silicate meteorites have a composition intermediate between stony and iron meteorites. They are relatively rare (1.5% incidence).
Achondrites, iron and iron-silicate meteorites are classified as differentiated meteorites. They presumably consist of matter that has undergone differentiation as part of asteroids or other planetary bodies. It was previously believed that all differentiated meteorites were formed by the rupture of one or more large bodies, such as the planet Phaeton. However, an analysis of the composition of different meteorites showed that they were more likely formed from the debris of many large asteroids.
Classification by detection method
- falls (when a meteorite is found after observing its fall in the atmosphere);
- finds (when the meteorite origin of the material is determined only by analysis);
Traces of extraterrestrial organics in meteorites
Coal complex
Carbonaceous (carbonaceous) meteorites have one important feature - the presence of a thin glassy crust, apparently formed under the influence of high temperatures. This crust is a good heat insulator, thanks to which minerals that cannot withstand strong heat, such as gypsum, are preserved inside carbonaceous meteorites. Thus, it became possible, when studying the chemical nature of such meteorites, to detect in their composition substances that, under modern earthly conditions, are organic compounds of a biogenic nature ( Source: Rutten M. Origin of life (naturally). - M., Publishing House "Mir", 1973) :
- Saturated hydrocarbons
- Isoprenoids
- n-Alkanes
- Cycloalkanes
- Aromatic hydrocarbons
- Naphthalene
- Alkybenzenes
- Acenaphthenes
- Pyrene
- Carboxylic acids
- Fatty acid
- Benzenecarboxylic acids
- Hydroxybenzoic acids
- Nitrogen compounds
- Pyrimidines
- Purines
- Guanylurea
- Triazines
- Porphyrins
The presence of such substances does not allow us to unambiguously declare the existence of life outside the Earth, since theoretically, if certain conditions were met, they could be synthesized abiogenically.
On the other hand, if the substances found in meteorites are not products of life, then they may be products of pre-life - similar to that which once existed on Earth.
"Organized Elements"
When studying stony meteorites, so-called “organized elements” are discovered - microscopic (5-50 microns) “single-cell” formations, often having clearly defined double walls, pores, spines, etc. ( Source: Same)
It is not an indisputable fact that these fossils are the remains of some form of extraterrestrial life. But, on the other hand, these formations have such a high degree of organization that is usually associated with life ( Source: Same).
In addition, such forms have not been found on Earth.
A feature of “organized elements” is also their large number: per 1g. The substances of the carbonaceous meteorite account for approximately 1800 “organized elements”.
Large modern meteorites in Russia
- Tunguska phenomenon (at the moment, the exact meteorite origin of the Tunguska phenomenon is unclear. For details, see the article Tunguska meteorite). Fell on June 30 this year in the Podkamennaya Tunguska river basin in Siberia. The total energy is estimated at 15−40 megatons of TNT equivalent.
- Tsarevsky meteorite (meteor shower). Fell on December 6 near the village of Tsarev, Volgograd region. This is a rock meteorite. The total mass of the collected fragments is 1.6 tons over an area of about 15 square meters. km. The weight of the largest fallen fragment was 284 kg.
- Sikhote-Alin meteorite (total mass of fragments is 30 tons, energy is estimated at 20 kilotons). It was an iron meteorite. Fell in the Ussuri taiga on February 12.
- Vitimsky car. Fell in the area of the villages of Mama and Vitimsky, Mamsko-Chuysky district, Irkutsk region, on the night of September 24-25. The event had a great public resonance, although the total energy of the meteorite explosion is apparently relatively small (200 tons of TNT equivalent, with an initial energy of 2.3 kilotons), the maximum initial mass (before combustion in the atmosphere) is 160 tons, and the final mass of the fragments is about several hundred kilograms.
The discovery of a meteorite is a rather rare occurrence. The Meteoritics Laboratory reports: “In total, only 125 meteorites have been found on the territory of the Russian Federation over 250 years.”
The only documented case of a meteorite hitting a person occurred on November 30 in Alabama. The meteorite, weighing about 4 kg, crashed through the roof of the house and ricocheted Anna Elizabeth Hodges on the arm and thigh. The woman received bruises.
Other interesting facts about meteorites:
Individual meteorites
- Channing
- Chainpur
- Beeler
- Arcadia
- Arapahoe
Notes
Links
Meteorite crash sites Google Maps KMZ(KMZ tag file for Google Earth)
- Museum of Extraterrestrial Matter RAS (meteorite collection)
- Peruvian chondrite (commentary by astronomer Nikolai Chugay)
see also
- Meteor craters or astroblemes.
- Portal:Meteorites
- Moldavite
Wikimedia Foundation. 2010.
Meteorites are cosmic bodies falling to Earth from 2nd space. speed, therefore experiencing heating, melting, explosion. The surface of the planets has the characteristic appearance of collisions
Types of meteorites: 1) Stone - Ch. MgFe silicate components, metal impurities. 2) Iron - Fe+ Ni alloy. 3) Iron-stone – intermediate. Meteorite minerals(main components): 1) Silicates (olivine, pyroxene). 2) Plagioclase is rare. 3) Layered silicates (with water - serpentine, chlorite) - extremely rare. 4) Metallic iron (tennesite and kamacite) differ in Ni content. 5) sulfideFeS- troilite (less common): (on average, meteorites are a carbonaceous substance). Apatite, magnetite diamond, lonsdaleite are important for understanding the genesis of MgS (MgS-FeS) CaS (olthamite) indicate oxygen deficiency during formation. Carbides – FeC, MgC. TiN nitrides. The problem of chemistry is complex - the proportions are violated: Stone - kg (destroyed in the atmosphere), iron - tens of thousands of tons. meteorites-finds meteorites-falls. -Statistics of finds – iron ones predominate. -Fall statistics - stone
7. Chondrites. Formation of the planets of the solar system
Stone. The main type of M. is stone, of which 90% are chondrites. Chondrules – density 3, formation not in planetary gravitational fields. The balls indicate formation in a liquid state, the crystallization structure is quenched. Composition: Olivine (skeletal crystals), pyroxene (quenching). Chondrules are the result of rapid cooling of silicate substances in unknown processes (multiple evaporation and condensation). The matter has not passed the planetary stage of development. Types of chondrites: Enstatite chondrite MgSiO3 + Fe itself. (met. phase) – restored situation. Carbonaceous chondrites - there is no native Fe, there is magnetite. C carbon – up to 2-3%, C H2O – first % (Sp, chl).
Meteorites-finds, meteorites-falls. -Primary substance? – enriched with volatile components. Achondrites (devoid of chondritic structure). -As a result of fur deformations (collisions), diamonds appear. -Brecciated (chondrule fragments). -Basaltoid (pyroxene plagioclase olivine) of a different origin (the quantity is small).
Iron meteorites: Tennesseeite + kamacite. The structure is lamellar, lattice - kamacite beams. Windmanstätten structure hardening temperature is 600 °C. Important - such structures could not be repeated in laboratory conditions (Fe condensation), the same structure of iron in the interstices in chondrites
Troilite nodules. - a rare admixture of silicates. -Iron-stone meteorites: -Pallasites are a uniform mixture without differentiation into light and heavy phases. -Their role is extremely small. -The history of meteorites is captured in the isotopic composition. -It turned out that the substance is ancient - 4.55 * 10 * 9 years. -This is the age of the Earth, the Moon and meteorite matter. - the “cosmic age” of meteorites, 100-200 million years, was determined from short-lived isotopes formed on the surface of meteorites under the influence of cosmic irradiation. -That is, meteorites are young formations that arose as a result of the fragmentation of cosmos. tel
The prevalence of elements in meteorites: The basic position developed by Goldschmitt on chondrites. Identity of the abundance of elements in chondrites and in the Solar system. Abundance of elements in meteorites: It is reasonably believed that chondrites are undifferentiated primary matter. But there are also differences from the Solar System: 1. H and inert gases are very rare in meteorites. 2. Depleted in Pb, Ge, Cd, Bi, Hg, but not as much as in inert gases. That is, chondrites are only a solid fraction of the primary substance (without volatile matter). The composition of the terrestrial planets is associated with this fraction. The main process of planet formation is the condensation of a gas-dust cloud.
8. Regularities of the structure of terrestrial planets
Planets differ in size, density, mass, distance from the Sun and other parameters. They are divided into two groups: internal (Mercury, Venus, Earth, Mars) and external (Jupiter, Saturn, Uranus, Neptune). They are separated by a ring of asteroids between Mars and Jupiter. As they move away from the Sun, the planets, up to the Earth, increase in size and become more dense (3.3–3.5 g/cm3), and the outer planets decrease, starting from Jupiter, and become less dense (0.71–2.00 g /cm3). In the inner planets, the silicate and metallic phases are distinguished, the latter is expressed in Mercury (62%). The closer a planet is to the Sun, the more metallic iron it contains. The outer planets are composed of gas components (H, He, CH4, NH3, etc.). Planets have one or more satellites, with the exception of Mercury and Venus.
9. Surface shells of planets
Planetary shells. P.'s vertical structure is layered; several are distinguished. spherical shells, differing in chemical composition, phase state, density, etc. physical-chemical. characteristics. All P. of the terrestrial group have hard shells, in which almost all of their mass is concentrated. Three of them - Venus, Earth and Mars - have gaseous atmospheres; Mercury is practically devoid of an atmosphere. Only the Earth has a liquid shell (discontinuous) of water - the hydrosphere, as well as a biosphere - a shell whose composition, structure and energy are essentially determined by the past and present. activities of living organisms. An analogue of the hydrosphere on Mars is. cryosphere - ice H 2 O in the polar caps and in the ground (permafrost). One of the mysteries of the solar system is the shortage of water on Venus. There is no liquid water there due to the high temperature, and the amount of water vapor in the atmosphere is equivalent to a layer of liquid ≈ 1 cm thick. The hard shells of the planet are in a hydrostatic state. equilibrium, since the yield strength of rocks corresponds to the weight of a rock column ≈10 km high (for the Earth). Therefore, the shape of the hard shells of P., which have a significantly greater thickness, is almost spherical. Due to the difference in gravity. force varies max. the height of the mountains on the planet (for example, on Earth it is about 10 km, and on Mars, where the gravitational field is weaker than the earth’s, about 25 km). The shape of small satellites of planets and asteroids can differ markedly from spherical.
10. Origin of the earth's shells
The geographic envelope is formed by two fundamentally different types of matter: atomic-molecular “non-living” matter and atomic-organismic “living” matter. The first can only participate in physicochemical processes, as a result of which new substances can appear, but from the same chemical elements. The second has the ability to reproduce its own kind, but of different composition and appearance. The interactions of the former require external energy expenditure, while the latter have their own energy and can release it during various interactions. Both types of matter arose simultaneously and have been functioning since the beginning of the formation of the earth’s spheres. Between the parts of the geographic shell there is a constant exchange of matter and energy, manifested in the form of atmospheric and oceanic circulation, movement of surface and underground waters, glaciers, movement of organisms and living matter, etc. Thanks to the movement of matter and energy, all parts of the geographical shell are interconnected and form an integral system
11. Structure and composition of the earth’s shells
The lithosphere, atmosphere and hydrosphere form almost continuous shells. The biosphere as a collection of living organisms in a certain habitat does not occupy an independent space, but develops the above-mentioned spheres completely (hydrosphere) or partially (atmosphere and lithosphere).
The geographic envelope is characterized by the identification of zonal-provincial units, which are called landscapes or geosystems. These complexes arise from a certain interaction and integration of geocomponents. The simplest geosystems are formed through the interaction of matter at an inert level of organization.
Chemical elements in the geographical shell are in a free state (in the air), in the form of ions (in water) and complex compounds (living organisms, minerals, etc.).
12. Structure and composition of the mantle
Mantle- the part of the Earth (geosphere) located directly below the crust and above the core. The mantle contains most of the Earth's matter. There is a mantle on other planets as well. The Earth's mantle ranges from 30 to 2900 km from the Earth's surface.
The boundary between the crust and the mantle is the Mohorovicic boundary, or Moho for short. There is a sharp increase in seismic velocities - from 7 to 8-8.2 km/s. This boundary is located at a depth of 7 (under the oceans) to 70 kilometers (under fold belts). The Earth's mantle is divided into an upper mantle and a lower mantle. The boundary between these geospheres is the Golitsyn layer, located at a depth of about 670 km.
The difference in the composition of the earth's crust and mantle is a consequence of their origin: the initially homogeneous Earth, as a result of partial melting, was divided into a low-melting and light part - the crust and a dense and refractory mantle.
The mantle is composed mainly of ultrabasic rocks: perovskites, peridotites, (lherzolites, harzburgites, wehrlites, pyroxenites), dunites and, to a lesser extent, basic rocks - eclogites.
Also, among the mantle rocks, rare varieties of rocks that are not found in the earth’s crust have been identified. These are various phlogopite peridotites, grospidites, and carbonatites.
Structure of the mantle
The processes occurring in the mantle have a direct impact on the earth's crust and surface of the earth, causing the movement of continents, volcanism, earthquakes, mountain building and the formation of ore deposits. There is growing evidence that the mantle itself is actively influenced by the Earth's metallic core.
13. Structure and composition of the earth's crust
The structure of the globe. The main object of geological, including mineralogical, research is Earth's crust*, which means the uppermost shell of the globe accessible to direct observation. This includes: the lower part of the atmosphere, the hydrosphere and the upper part of the lithosphere, i.e. the solid part of the Earth.
The hypothesis of V. M. Goldshmidt about the structure of the globe currently enjoys the greatest recognition. The latter, according to his ideas, consists of three main concentrically located zones (geospheres):
outer - lithosphere;
intermediate - chalcosphere, rich in oxides and sulfur compounds of metals, mainly iron,
the central one is the siderosphere, represented by an iron-nickel core.
The lithosphere, in turn, is divided into two parts:
upper shell - to a depth of 120 km, composed mainly of ordinary silicate rocks,
the lower one is the eclogite shell (120-1200 km), represented by silicate rocks enriched in magnesium.
Composition of the earth's crust.
The most common elements are: O, Si, Al, Fe, Ca, Na, K, Mg, H, Ti, C and Cl. The remaining 80 elements account for only 0.71% (by weight)