The shell of the earth consisting of slabs. The main spheres of planet Earth: lithosphere, hydrosphere, biosphere and atmosphere
In educational literature, the “stone shell of the Earth” refers to one of its shells - the lithosphere. It extends from the earth's surface to a depth of 100-250 km under the continents and up to 50-300 km under the oceans to the asthenosphere layer, a layer of “softened” plastic rocks. The lithosphere includes two components: the earth's crust and the upper solid layer of the mantle. Thus, the earth's crust is the solid upper shell of the Earth, and it relates to the lithosphere as a part and a whole.
The term “earth’s crust” was introduced into geographical science by the Austrian geologist E. Suess in 1881. (8) In addition to this term, this layer has another name - sial, composed of the first letters of the most common elements here - silicon (silicium, 26%) and aluminum (aluminum, 7.45%). The thickness of the earth's crust ranges from 5-20 km under the oceans to 30-40 km under the continents, in mountainous areas - up to 75 km. (10)
The structure of the earth's crust is heterogeneous. There are three layers in it: sedimentary, “granite” and “basalt”. Since the “granite” layer is approximately half composed of granites, and 40% of it is occupied by granite gneisses and orthogneisses, it is more correct to call it a granite gneiss layer. Also the “basalt” layer, since its composition is quite diverse, and metamorphic rocks of basic composition (granulites, eclogites) predominate in it, it is more correct to call it a granulite-mafic layer. The boundary between the granite-gneiss and granulite-mafic layers is the Conrad section. The lower boundary of the earth's crust stands out quite clearly, which is associated with an increase in the speed of longitudinal seismic waves in the underlying layer of the mantle. This boundary is called the Mohorovicic boundary in honor of the Yugoslav seismologist A. Mohorovicic, who first established it.
In different regions of the planet, the structure of the earth's crust is also different. In general, it can be divided into two types: continental and oceanic.
Continental type - its thickness ranges from 35 - 45 km on platforms to 55-75 km in mountainous areas. It is composed of three layers: sedimentary - from 0 km on shields to 15-20 km in marginal foothill troughs and platform depressions; granite gneiss layer - 20-30 km thick; granulite-mafic layer, the thickness of which reaches 15-35 km.
The oceanic crust is much thinner than the continental crust. Its structure also includes three layers: sedimentary with a maximum thickness of up to 1 km, composed of various sedimentary formations, most of which are in a loose state and saturated with water; basalt layer with interlayers of carbonate and siliceous rocks, 1-3 km thick; gabbro-basalt layer with the presence of ultrabasic rocks (pyroxenites, serpentinites), the thickness of which ranges from 3 to 5 km. Previously, it was believed that the oceanic crust was composed of only two layers, without granite, but after underwater drilling and seismic research, more accurate results were obtained.
In addition to the main ones, there are two transitional types: suboceanic and subcontinental.
The subcontinental type is similar in structure to the continental type and is distributed along the margins of continents and in areas of island arcs. The upper layer is sedimentary-volcanogenic with a thickness of 0.5-5 km; the second layer is composed of granite-metamorphic strata and has a thickness of up to 10 km; the third layer is basalt, the thickness of which ranges from 15 to 40 km.
Suboceanic type - similar in structure to the oceanic crust, located in the basins of marginal and inland seas (Sea of Okhotsk, Black Sea). This type differs from the oceanic crust by a much thicker layer of sedimentary rocks, reaching 10 km.
The question of the origin of the earth's crust remains unresolved to this day, as evidenced by the presence of various hypotheses for its formation. One of the most substantiated views is the principle of “zone” melting by A.P. Vinogradova. Its essence is as follows: the substance of the mantle is in a solid equilibrium state, but when external conditions (pressure, temperature) change, the mass of the substance transforms into a liquid mobile form and begins to mix in the radial direction towards the Earth's surface. As it progresses, differentiation of the substance occurs: low-melting compounds are brought to the surface, refractory compounds remain at depth. This process, which was repeated many times in the past and has not ceased its activity in the present, determined not only the formation of the earth’s crust, but also its chemical composition. As a result of the radial removal of elements, layers of the earth's crust were also formed: the basaltic layer was formed during the melting of mantle material, the formation of the granite layer is associated with the melting of metamorphic rocks and their enrichment with chemical elements due to the degassing process. This process was more active in geosynclinal belts, on continents, as evidenced by the greater thickness of the granite layer here. In the oceans, degassing was less efficient, as evidenced by the absence of a granite layer and the poverty of oceanic basalts in chemical elements. The sedimentary layer has a slightly different origin. The rocks of the granite layer that appeared on the surface were exposed to external conditions, the most important of which was and remains the geochemical effect of the vital activity of organisms, as evidenced by the high content of oxidized forms of sulfur, organic carbon, nitrogen, etc. in the sedimentary layer. This effect manifests itself both directly and indirectly through influencing the conditions that determine the transformation of rocks (acidity / alkalinity, the amount of oxygen and carbon dioxide, the presence of organic compounds, etc.) (9)
That. the earth's crust is the upper solid shell of the Earth; in its structure three layers are distinguished: sedimentary, granite-gneiss and granulite-mafic; According to the type of structure, continental and oceanic crust are distinguished, differing in thickness and composition of layers, as well as transitional - suboceanic and subcontinental, which have similarities with the main types, but at the same time have some isolation.
Earth is the 3rd planet from the Sun, located between Venus and Mars. It is the densest planet in the solar system, the largest of the four, and the only astronomical object known to host life. According to radiometric dating and other research methods, our planet formed about 4.54 billion years ago. The Earth gravitationally interacts with other objects in space, especially the Sun and Moon.
The Earth consists of four main spheres or shells, which depend on each other and are the biological and physical components of our planet. They are scientifically called biophysical elements, namely the hydrosphere ("hydro" for water), the biosphere ("bio" for living things), the lithosphere ("litho" for land or earth's surface), and the atmosphere ("atmo" for air). These main spheres of our planet are further divided into various sub-spheres.
Let's look at all four shells of the Earth in more detail to understand their functions and meaning.
Lithosphere - the hard shell of the Earth
According to scientists, there are more than 1386 million km³ of water on our planet.
The oceans contain more than 97% of the Earth's water. The rest is fresh water, two-thirds of which is frozen in the planet's polar regions and on snowy mountain peaks. It is interesting to note that although water covers most of the planet's surface, it makes up only 0.023% of the Earth's total mass.
The biosphere is the living shell of the Earth
The biosphere is sometimes considered one big one - a complex community of living and nonliving components functioning as a single whole. However, most often the biosphere is described as a collection of many ecological systems.
Atmosphere - the air envelope of the Earth
The atmosphere is the collection of gases surrounding our planet, held in place by the Earth's gravity. Most of our atmosphere is located near the earth's surface, where it is densest. The Earth's air is 79% nitrogen and just under 21% oxygen, as well as argon, carbon dioxide and other gases. Water vapor and dust are also part of the Earth's atmosphere. Other planets and the Moon have very different atmospheres, and some have no atmosphere at all. There is no atmosphere in space.
The atmosphere is so widespread that it is almost invisible, but its weight is equal to the layer of water more than 10 meters deep that covers our entire planet. The lower 30 kilometers of the atmosphere contain about 98% of its total mass.
Scientists say many of the gases in our atmosphere were released into the air by early volcanoes. At that time there was little or no free oxygen around the Earth. Free oxygen consists of oxygen molecules not bonded to another element, such as carbon (to form carbon dioxide) or hydrogen (to form water).
Free oxygen may have been added to the atmosphere by primitive organisms, probably bacteria, during . Later, more complex forms added more oxygen to the atmosphere. The oxygen in today's atmosphere likely took millions of years to accumulate.
The atmosphere acts like a giant filter, absorbing most of the ultraviolet radiation and allowing the sun's rays to penetrate. Ultraviolet radiation is harmful to living things and can cause burns. However, solar energy is essential for all life on Earth.
The Earth's atmosphere has. The following layers extend from the surface of the planet to the sky: troposphere, stratosphere, mesosphere, thermosphere and exosphere. Another layer, called the ionosphere, extends from the mesosphere to the exosphere. Outside the exosphere is space. The boundaries between atmospheric layers are not clearly defined and vary depending on latitude and time of year.
Interrelation of the Earth's shells
All four spheres can be present in one place. For example, a piece of soil will contain minerals from the lithosphere. In addition, there will be elements of the hydrosphere, which is moisture in the soil, the biosphere, which is insects and plants, and even the atmosphere, which is soil air.
All spheres are interconnected and depend on each other, like a single organism. Changes in one area will lead to changes in another. Therefore, everything we do on our planet affects other processes within its boundaries (even if we cannot see it with our own eyes).
For people dealing with problems, it is very important to understand the interconnection of all the layers of the Earth.
Introduction
1. Basic shells of the earth
3. Geothermal regime of the earth
Conclusion
List of sources used
Introduction
Geology is the science of the structure and history of the development of the Earth. The main objects of research are rocks that contain the geological record of the Earth, as well as modern physical processes and mechanisms operating both on its surface and in the depths, the study of which allows us to understand how our planet developed in the past.
The earth is constantly changing. Some changes occur suddenly and very violently (for example, volcanic eruptions, earthquakes or large floods), but more often - slowly (a layer of sediment no more than 30 cm thick is removed or accumulates over a century). Such changes are not noticeable throughout the life of one person, but some information has been accumulated about changes over a long period of time, and with the help of regular accurate measurements, even minor movements of the earth’s crust are recorded.
The history of the Earth began simultaneously with the development of the solar system approximately 4.6 billion years ago. However, the geological record is characterized by fragmentation and incompleteness, because many ancient rocks were destroyed or covered by younger sediments. Gaps must be filled by correlation with events that have occurred elsewhere and for which more data are available, as well as by analogy and hypotheses. The relative age of rocks is determined on the basis of the complexes of fossil remains they contain, and sediments in which such remains are absent are determined by the relative positions of both. In addition, the absolute age of almost all rocks can be determined by geochemical methods.
This work examines the main shells of the earth, its composition and physical structure.
1. Basic shells of the earth
The Earth has 6 shells: atmosphere, hydrosphere, biosphere, lithosphere, pyrosphere and centrosphere.
The atmosphere is the outer gaseous shell of the Earth. Its lower boundary runs along the lithosphere and hydrosphere, and its upper boundary is at an altitude of 1000 km. The atmosphere is divided into the troposphere (moving layer), stratosphere (layer above the troposphere) and ionosphere (upper layer).
The average height of the troposphere is 10 km. Its mass makes up 75% of the total mass of the atmosphere. The air in the troposphere moves in both horizontal and vertical directions.
The stratosphere rises 80 km above the troposphere. Its air, moving only in a horizontal direction, forms layers.
Even higher extends the ionosphere, which got its name due to the fact that its air is constantly ionized under the influence of ultraviolet and cosmic rays.
The hydrosphere occupies 71% of the Earth's surface. Its average salinity is 35 g/l. The temperature of the ocean surface is from 3 to 32 ° C, density is about 1. Sunlight penetrates to a depth of 200 m, and ultraviolet rays penetrate to a depth of 800 m.
The biosphere, or sphere of life, merges with the atmosphere, hydrosphere and lithosphere. Its upper boundary reaches the upper layers of the troposphere, the lower boundary runs along the bottom of the ocean basins. The biosphere is divided into the sphere of plants (over 500,000 species) and the sphere of animals (over 1,000,000 species).
The lithosphere - the rocky shell of the Earth - is from 40 to 100 km thick. It includes continents, islands and the bottom of the oceans. The average height of the continents above ocean level: Antarctica - 2200 m, Asia - 960 m, Africa - 750 m, North America - 720 m, South America - 590 m, Europe - 340 m, Australia - 340 m.
Under the lithosphere is the pyrosphere - the fiery shell of the Earth. Its temperature increases by about 1°C for every 33 m of depth. Due to high temperatures and high pressure, rocks at significant depths are likely to be in a molten state.
The centosphere, or the core of the Earth, is located at a depth of 1800 km. According to most scientists, it consists of iron and nickel. The pressure here reaches 300000000000 Pa (3000000 atmospheres), the temperature is several thousand degrees. The state of the core is still unknown.
The fiery sphere of the Earth continues to cool. The hard shell thickens, the fiery shell thickens. At one time, this led to the formation of solid stone blocks - continents. However, the influence of the fiery sphere on the life of planet Earth is still very great. The outlines of continents and oceans, the climate, and the composition of the atmosphere changed repeatedly.
Exogenous and endogenous processes continuously change the solid surface of our planet, which, in turn, actively affects the Earth's biosphere.
2. Composition and physical structure of the earth
Geophysical data and the results of studying deep inclusions indicate that our planet consists of several shells with different physical properties, the change of which reflects both the change in the chemical composition of the substance with depth and the change in its state of aggregation as a function of pressure.
The uppermost shell of the Earth - the earth's crust - under the continents has an average thickness of about 40 km (25-70 km), and under the oceans - only 5-10 km (without the layer of water, which averages 4.5 km). The lower edge of the earth's crust is taken to be the Mohorovicic surface - a seismic section on which the speed of propagation of longitudinal elastic waves with a depth of 6.5-7.5 to 8-9 km/s increases abruptly, which corresponds to an increase in the density of matter from 2.8-3 .0 to 3.3 g/cm3.
From the surface of Mohorovicic to a depth of 2900 km, the Earth's mantle extends; the upper least dense zone, 400 km thick, is distinguished as the upper mantle. The interval from 2900 to 5150 km is occupied by the outer core, and from this level to the center of the Earth, i.e. from 5150 to 6371 km, the inner core is located.
The Earth's core has interested scientists since its discovery in 1936. It was extremely difficult to image because of the relatively small number of seismic waves that reached it and returned to the surface. Additionally, the core's extreme temperatures and pressures have long been difficult to reproduce in the laboratory. New research may provide a more detailed picture of the center of our planet. The earth's core is divided into 2 separate regions: liquid (outer core) and solid (inner core), the transition between which lies at a depth of 5,156 km.
Iron is the only element that closely matches the seismic properties of the Earth's core and is abundant enough in the Universe to represent approximately 35% of the planet's mass in the core. According to modern data, the outer core is a rotating stream of molten iron and nickel that conducts electricity well. It is with this that the origin of the earth's magnetic field is associated, believing that, like a giant generator, electric currents flowing in the liquid core create a global magnetic field. The layer of the mantle that is in direct contact with the outer core is influenced by it, since temperatures in the core are higher than in the mantle. In some places, this layer generates huge heat and mass flows directed towards the Earth's surface - plumes.
The inner solid core is not connected to the mantle. It is believed that its solid state, despite the high temperature, is ensured by the gigantic pressure in the center of the Earth. It has been suggested that in addition to iron-nickel alloys, the core should also contain lighter elements, such as silicon and sulfur, and possibly silicon and oxygen. The question of the state of the Earth's core is still controversial. As you move away from the surface, the compression to which the substance is subjected increases. Calculations show that in the earth's core the pressure can reach 3 million atm. At the same time, many substances seem to be metallized - they pass into the metallic state. There was even a hypothesis that the Earth's core consists of metallic hydrogen.
The outer core is also metallic (essentially iron), but unlike the inner core, the metal is here in a liquid state and does not transmit transverse elastic waves. Convective currents in the metallic outer core cause the formation of the Earth's magnetic field.
The Earth's mantle consists of silicates: compounds of silicon and oxygen with Mg, Fe, Ca. The upper mantle is dominated by peridotites - rocks consisting mainly of two minerals: olivine (Fe,Mg) 2SiO4 and pyroxene (Ca, Na) (Fe,Mg,Al) (Si,Al) 2O6. These rocks contain relatively little (< 45 мас. %) кремнезема (SiO2) и обогащены магнием и железом. Поэтому их называют ультраосновными и ультрамафическими. Выше поверхности Мохоровичича в пределах континентальной земной коры преобладают силикатные магматические породы основного и кислого составов. Основные породы содержат 45-53 мас. % SiO2. Кроме оливина и пироксена в состав основных пород входит Ca-Na полевой шпат - плагиоклаз CaAl2Si2O8 - NaAlSi3O8. Кислые магматические породы предельно обогащены кремнеземом, содержание которого возрастает до 65-75 мас. %. Они состоят из кварца SiO2, плагиоклаза и K-Na полевого шпата (K,Na) AlSi3O8. Наиболее распространенной интрузивной породой основного состава является габбро, а вулканической породой - базальт. Среди кислых интрузивных пород чаще всего встречается гранит, a вулканическим аналогом гранита является риолит .
Thus, the upper mantle consists of ultrabasic and ultramafic rocks, and the earth’s crust is formed mainly by basic and acidic igneous rocks: gabbro, granites and their volcanic analogues, which, compared to the peridotites of the upper mantle, contain less magnesium and iron and at the same time are enriched in silica , aluminum and alkali metals.
Beneath the continents, mafic rocks are concentrated in the lower part of the crust, and felsic rocks are concentrated in the upper part. Beneath the oceans, the thin crust of the earth consists almost entirely of gabbro and basalt. It is firmly established that the basic rocks, which according to various estimates constitute from 75 to 25% of the mass of the continental crust and almost all of the oceanic crust, were smelted from the upper mantle during the process of magmatic activity. Felsic rocks are usually considered to be the product of repeated partial melting of mafic rocks within the continental crust. Peridotites from the uppermost part of the mantle are depleted in fusible components, transported during magmatic processes into the earth's crust. The upper mantle beneath the continents, where the thickest crust arose, is especially “depleted.”
The rocky shell of the Earth - the earth's crust - is firmly attached to the upper mantle and forms a single whole with it -. The study of the earth's crust and lithosphere allows scientists to explain the processes occurring on the Earth's surface and anticipate changes in the appearance of our planet in the future.
Structure of the earth's crust
The earth's crust, consisting of igneous, metamorphic and sedimentary rocks, on continents and under oceans has different thickness and structure.
It is customary to distinguish three layers in the continental crust. The upper layer is sedimentary, in which sedimentary rocks predominate. The two lower layers are conventionally called granite and basalt. The granite layer consists primarily of granite and metamorphic rocks. The basalt layer is made of denser rocks, comparable in density to basalts. Oceanic crust has two layers. In it, the upper layer - sedimentary - has a small thickness, the lower layer - basalt - consists of basalt rocks, and there is no granite layer.
The thickness of the continental crust under the plains is 30–50 kilometers, under the mountains - up to 75 kilometers. The oceanic crust is much thinner, its thickness is from 5 to 10 kilometers.
There is a crust on other terrestrial planets, on the Moon and on many satellites of the giant planets. But only the Earth has two types of crust: continental and oceanic. On other planets, in most cases it consists of basalts.
Lithosphere
The rocky shell of the Earth, including the crust and the upper part of the mantle, is called the lithosphere. Beneath it there is a heated plastic layer of the mantle. The lithosphere seems to float on this layer. The thickness of the lithosphere in different regions of the Earth varies from 20 to 200 kilometers or more. In general, it is thicker under continents than under oceans.
Scientists have found that the lithosphere is not monolithic, but consists of. They are separated from each other by deep faults. There are seven very large and several smaller lithospheric plates, which constantly but slowly move along the plastic layer of the mantle. The average speed of their movement is about 5 centimeters per year. Some plates are entirely oceanic, but most have different types of crust.
Lithospheric plates move relative to each other in different directions: they either move away, or, conversely, they come closer and collide. As part of the lithospheric plates, their upper “floor” - the earth’s crust - also moves. Due to the movement of lithospheric plates, the location of continents and oceans on the Earth's surface changes. The continents either collide with each other or move thousands of kilometers away from each other.
