The upper layer of the Earth, which gives life to the inhabitants of the planet, is just a thin shell covering many kilometers of inner layers. Little more is known about the hidden structure of the planet than about outer space. The deepest Kola well, drilled into the earth's crust to study its layers, has a depth of 11 thousand meters, but this is only four hundredth of the distance to the center of the globe. Only seismic analysis can get an idea of the processes taking place inside and create a model of the Earth's structure.
Inner and outer layers of the Earth
The structure of the planet Earth is heterogeneous layers of inner and outer shells, which differ in composition and role, but are closely related to each other. The following concentric zones are located inside the globe:
- The core - with a radius of 3500 km.
- Mantle - approximately 2900 km.
- Earth's crust- an average of 50 km.
The outer layers of the earth make up a gaseous shell, which is called the atmosphere.
Center of the planet
The central geosphere of the Earth is its core. If we raise the question of which layer of the Earth is practically the least studied, then the answer will be - the core. It is not possible to obtain exact data on its composition, structure and temperature. All information that is published in scientific papers has been obtained by geophysical, geochemical methods and mathematical calculations and is presented to the general public with the proviso "presumably". As the results of the analysis of seismic waves show, the earth's core consists of two parts: internal and external. The inner core is the most unexplored part of the Earth, since seismic waves do not reach its limits. The outer core is a mass of hot iron and nickel, with a temperature of about 5 thousand degrees, which is constantly in motion and is a conductor of electricity. It is with these properties that the origin of the Earth's magnetic field is associated. The composition of the inner core, according to scientists, is more diverse and is supplemented by even lighter elements - sulfur, silicon, and possibly oxygen.
Mantle
The geosphere of the planet, which connects the central and upper layers of the Earth, is called the mantle. It is this layer that makes up about 70% of the mass of the globe. The lower part of the magma is the shell of the core, its outer boundary. Seismic analysis shows here a sharp jump in the density and velocity of compressional waves, which indicates a material change in the composition of the rock. The composition of the magma is a mixture of heavy metals, dominated by magnesium and iron. The upper part of the layer, or asthenosphere, is a mobile, plastic, soft mass with a high temperature. It is this substance that breaks through the earth's crust and splashes to the surface in the process of volcanic eruptions.
The thickness of the magma layer in the mantle is from 200 to 250 kilometers, the temperature is about 2000 ° C. The mantle is separated from the lower globe of the earth's crust by the Moho layer, or the Mohorovichic boundary, by a Serbian scientist who determined a sharp change in the speed of seismic waves in this part of the mantle.
hard shell
What is the name of the layer of the Earth that is the hardest? This is the lithosphere, a shell that connects the mantle and the earth's crust, it is located above the asthenosphere, and cleans the surface layer from its hot influence. The main part of the lithosphere is part of the mantle: out of the entire thickness from 79 to 250 km, the earth's crust accounts for 5-70 km, depending on the location. The lithosphere is heterogeneous, it is divided into lithospheric plates, which are in constant slow motion, sometimes diverging, sometimes approaching each other. Such fluctuations of the lithospheric plates are called tectonic movement, it is their fast tremors that cause earthquakes, splits in the earth's crust, and magma splashing onto the surface. The movement of lithospheric plates leads to the formation of troughs or hills, the frozen magma forms mountain ranges. Plates do not have permanent boundaries, they join and separate. Territories of the Earth's surface, above the faults tectonic plates- these are places of increased seismic activity, where earthquakes, volcanic eruptions occur more often than in others, minerals are formed. At this time, 13 lithospheric plates have been recorded, the largest of them: American, African, Antarctic, Pacific, Indo-Australian and Eurasian.
Earth's crust
Compared to other layers, the earth's crust is the thinnest and most fragile layer of all earth's surface. The layer in which organisms live, which is most saturated chemicals and trace elements, is only 5% of the total mass of the planet. The earth's crust on planet Earth has two varieties: continental or mainland and oceanic. The continental crust is harder, consists of three layers: basalt, granite and sedimentary. The ocean floor is made up of basalt (basic) and sedimentary layers.
- Basalt rocks- These are igneous fossils, the densest of the layers of the earth's surface.
- granite layer- absent under the oceans, on land it can approach a thickness of several tens of kilometers of granite, crystalline and other similar rocks.
- Sedimentary layer formed during the destruction of rocks. In some places it contains deposits of minerals of organic origin: coal, table salt, gas, oil, limestone, chalk, potassium salts and others.
Hydrosphere
Characterizing the layers of the Earth's surface, one cannot fail to mention the vital water shell of the planet, or the hydrosphere. The water balance on the planet is maintained by ocean waters (the main water mass), groundwater, glaciers, inland waters of rivers, lakes and other bodies of water. 97% of the entire hydrosphere falls on the salt water of the seas and oceans, and only 3% is fresh drinking water, of which the bulk is in glaciers. Scientists suggest that the amount of water on the surface will increase over time due to deep balls. Hydrospheric masses are in constant circulation, they pass from one state to another and closely interact with the lithosphere and atmosphere. The hydrosphere has a great influence on all earthly processes, the development and life of the biosphere. It was the water shell that became the environment for the origin of life on the planet.
The soil
The thinnest fertile layer of the Earth called soil, or soil, together with the water shell, is of the greatest importance for the existence of plants, animals and humans. This ball arose on the surface as a result of erosion of rocks, under the influence of organic decomposition processes. Processing the remnants of life, millions of microorganisms have created a layer of humus - the most favorable for crops of all kinds of land plants. One of the important indicators of high soil quality is fertility. The most fertile soils are those with an equal content of sand, clay and humus, or loam. Clay, rocky and sandy soils are among the least suitable for agriculture.
Troposphere
The air shell of the Earth rotates together with the planet and is inextricably linked with all processes occurring in the earth's layers. The lower part of the atmosphere through the pores penetrates deep into the body of the earth's crust, the upper part gradually connects with space.
The layers of the Earth's atmosphere are heterogeneous in composition, density and temperature.
At a distance of 10 - 18 km from the earth's crust extends the troposphere. This part of the atmosphere is heated by the earth's crust and water, so it gets colder with height. The decrease in temperature in the troposphere occurs by about half a degree every 100 meters, and at the highest points it reaches from -55 to -70 degrees. This part of the airspace occupies the largest share - up to 80%. It is here that the weather is formed, storms, clouds gather, precipitation and winds form.
high layers
- Stratosphere- the ozone layer of the planet, which absorbs the ultraviolet radiation of the sun, preventing it from destroying all life. The air in the stratosphere is rarefied. Ozone maintains a stable temperature in this part of the atmosphere from -50 to 55 ° C. In the stratosphere, an insignificant part of moisture, therefore, clouds and precipitation are not characteristic of it, in contrast to air currents that are significant in speed.
- Mesosphere, thermosphere, ionosphere- the air layers of the Earth above the stratosphere, in which a decrease in the density and temperature of the atmosphere is observed. The layer of the ionosphere is the place where the glow of charged gas particles occurs, which is called the aurora.
- Exosphere- a sphere of dispersion of gas particles, a blurred border with space.
I can’t say that the school was a place of incredible discoveries for me, but there were really memorable moments in the lessons. For example, once in a literature class I was leafing through a geography textbook (don't ask), and somewhere in the middle I found a chapter on the differences between oceanic and continental crust. This information really surprised me. That's what I remember.
Oceanic crust: properties, layers, thickness
It is distributed, obviously, under the oceans. Although under some seas lies not even oceanic, but continental crust. This applies to those seas that are located above the continental shelf. Some underwater plateaus - microcontinents in the ocean are also composed of continental, and not oceanic crust.
But most of our planet is still covered by the oceanic crust. The average thickness of its layer is 6-8 km. Although there are places with a thickness of both 5 km and 15 km.
It consists of three main layers:
- sedimentary;
- basalt;
- gabbro-serpentinite.
Continental crust: properties, layers, thickness
It is also called continental. It occupies smaller areas than the oceanic one, but it is many times greater than it in thickness. On flat areas, the thickness varies from 25 to 45 km, and in the mountains it can reach 70 km!
It has from two to three layers (from bottom to top):
- lower ("basalt", also known as granulite-basite);
- upper (granite);
- "cover" from sedimentary rocks (not always happens).
Those parts of the crust where "sheath" rocks are absent are called shields.
The layered structure is somewhat reminiscent of the oceanic, but it is clear that their basis is completely different. The granite layer, which makes up most of the continental crust, is absent in the oceanic one as such.
It should be noted that the names of the layers are rather conditional. This is due to the difficulties of studying the composition of the earth's crust. The possibilities of drilling are limited, therefore, the deep layers were initially studied and are being studied not so much on the basis of "live" samples, but on the speed of seismic waves passing through them. Passing speed like granite? Let's call it granite. It is difficult to judge how "granite" the composition is.
The earth's crust is of great importance for our life, for the exploration of our planet.
This concept is closely related to others that characterize the processes occurring inside and on the surface of the Earth.
What is the earth's crust and where is it located
The earth has an integral and continuous shell, which includes: the earth's crust, troposphere and stratosphere, which are the lower part of the atmosphere, hydrosphere, biosphere and anthroposphere.
They closely interact, penetrating each other and constantly exchanging energy and matter. It is customary to call the earth's crust the outer part of the lithosphere - the solid shell of the planet. Most of its outer side is covered by the hydrosphere. The rest, a smaller part, is affected by the atmosphere.
Under the Earth's crust is a denser and more refractory mantle. They are separated by a conditional border, named after the Croatian scientist Mohorovich. Its feature is a sharp increase in the speed of seismic vibrations.
Various scientific methods are used to gain insight into the earth's crust. However, obtaining specific information is possible only by means of drilling to a greater depth.
One of the objectives of such a study was to establish the nature of the boundary between the upper and lower continental crust. The possibilities of penetration into the upper mantle with the help of self-heating capsules made of refractory metals were discussed.
The structure of the earth's crust
Under the continents, its sedimentary, granite and basalt layers are distinguished, the thickness of which in the aggregate is up to 80 km. Rocks, called sedimentary rocks, were formed as a result of the deposition of substances on land and in water. They are predominantly in layers.
- clay
- shales
- sandstones
- carbonate rocks
- rocks of volcanic origin
- coal and other breeds.
The sedimentary layer helps to learn more about natural conditions on earth, which were on the planet in time immemorial. Such a layer may have a different thickness. In some places it may not exist at all, in others, mainly in large depressions, it may be 20-25 km.
The temperature of the earth's crust
An important energy source for the inhabitants of the Earth is the heat of its crust. The temperature increases as you go deeper into it. The 30-meter layer closest to the surface, called the heliometric layer, is associated with the heat of the sun and fluctuates depending on the season.
In the next, thinner layer, which increases in continental climates, the temperature is constant and corresponds to the indicators of a particular measurement site. In the geothermal layer of the crust, the temperature is related to the internal heat of the planet and increases as you go deeper into it. It is different in different places and depends on the composition of the elements, the depth and conditions of their location.
It is believed that the temperature rises on average by three degrees as it deepens for every 100 meters. Unlike the continental part, the temperature under the oceans is rising faster. After the lithosphere, there is a plastic high-temperature shell, the temperature of which is 1200 degrees. It is called the asthenosphere. It has places with molten magma.
Penetrating into the earth's crust, the asthenosphere can pour out molten magma, causing volcanic phenomena.
Characteristics of the Earth's crust
The Earth's crust has a mass of less than half a percent of the total mass of the planet. It is the outer shell of the stone layer in which the movement of matter occurs. This layer, which has a density half that of the Earth. Its thickness varies within 50-200 km.
The uniqueness of the earth's crust is that it can be of continental and oceanic types. The continental crust has three layers, the upper of which is formed by sedimentary rocks. The oceanic crust is relatively young and its thickness varies little. It is formed due to the substances of the mantle from oceanic ridges.
earth's crust characteristic photo
The thickness of the crust under the oceans is 5-10 km. Its feature is in constant horizontal and oscillatory movements. Most of the crust is basalt.
The outer part of the earth's crust is the hard shell of the planet. Its structure is distinguished by the presence of mobile areas and relatively stable platforms. Lithospheric plates move relative to each other. The movement of these plates can cause earthquakes and other cataclysms. The regularities of such movements are studied by tectonic science.
Functions of the earth's crust
The main functions of the earth's crust are:
- resource;
- geophysical;
- geochemical.
The first of them indicates the presence of the resource potential of the Earth. It is primarily a set of mineral reserves located in the lithosphere. In addition, the resource function includes a number of environmental factors that ensure the life of humans and other biological objects. One of them is the tendency to form a hard surface deficit.
you can't do that. save our earth photo
Thermal, noise and radiation effects realize the geophysical function. For example, there is a problem of natural radiation background, which is generally safe on the earth's surface. However, in countries such as Brazil and India, it can be hundreds of times higher than the allowable one. It is believed that its source is radon and its decay products, as well as some types of human activity.
Geochemical function associated with problems chemical pollution harmful to humans and other representatives of the animal world. Various substances with toxic, carcinogenic and mutagenic properties enter the lithosphere.
They are safe when they are in the bowels of the planet. Zinc, lead, mercury, cadmium and other heavy metals extracted from them can be very dangerous. In processed solid, liquid and gaseous form, they enter the environment.
What is the Earth's crust made of?
Compared to the mantle and core, the Earth's crust is fragile, tough, and thin. It consists of a relatively light substance, which includes about 90 natural elements. They are found in different places of the lithosphere and with varying degrees of concentration.
The main ones are: oxygen silicon aluminum, iron, potassium, calcium, sodium magnesium. 98 percent of the earth's crust is made up of them. Including about half is oxygen, more than a quarter - silicon. Due to their combinations, minerals such as diamond, gypsum, quartz, etc. are formed. Several minerals can form a rock.
- An ultra-deep well on the Kola Peninsula made it possible to get acquainted with mineral samples from a depth of 12 km, where rocks similar to granites and shale were found.
- The greatest thickness of the crust (about 70 km) was revealed under the mountain systems. Under the flat areas it is 30-40 km, and under the oceans - only 5-10 km.
- A significant part of the crust forms an ancient low-density upper layer, consisting mainly of granites and shales.
- The structure of the earth's crust resembles the crust of many planets, including those on the Moon and their satellites.
A distinctive feature of the earth's lithosphere, associated with the phenomenon of the global tectonics of our planet, is the presence of two types of crust: continental, which makes up continental masses, and oceanic. They differ in composition, structure, thickness and nature of the prevailing tectonic processes. An important role in the functioning of a single dynamic system, which is the Earth, belongs to the oceanic crust. To clarify this role, it is first necessary to turn to the consideration of its inherent features.
general characteristics
The oceanic type of crust forms the largest geological structure of the planet - the ocean bed. This crust has a small thickness - from 5 to 10 km (for comparison, the thickness of the continental-type crust is on average 35-45 km and can reach 70 km). It occupies about 70% of the total surface area of the Earth, but in terms of mass it is almost four times inferior to the continental crust. The average density of rocks is close to 2.9 g/cm 3 , that is, higher than that of the continents (2.6-2.7 g/cm 3 ).
Unlike isolated blocks of the continental crust, the oceanic one is a single planetary structure, which, however, is not monolithic. The Earth's lithosphere is divided into a number of mobile plates formed by sections of the crust and the underlying upper mantle. The oceanic type of crust is present on all lithospheric plates; there are plates (for example, the Pacific or Nazca) that do not have continental masses.
Plate tectonics and crustal age
In the oceanic plate, such large structural elements as stable platforms - thalassocratons - and active mid-ocean ridges and deep-sea trenches are distinguished. Ridges are areas of spreading, or moving apart of plates and the formation of new crust, and trenches are subduction zones, or subduction of one plate under the edge of another, where the crust is destroyed. Thus, its continuous renewal takes place, as a result of which the age of the most ancient crust of this type does not exceed 160-170 million years, that is, it was formed in the Jurassic period.
On the other hand, it should be borne in mind that the oceanic type appeared on Earth earlier than the continental type (probably at the turn of the Catarcheans - Archeans, about 4 billion years ago), and is characterized by a much more primitive structure and composition.
What and how is the earth's crust under the oceans
Currently, there are usually three main layers of oceanic crust:
- Sedimentary. It is formed mainly by carbonate rocks, partly by deep-water clays. Near the slopes of the continents, especially near the deltas of large rivers, there are also terrigenous sediments entering the ocean from land. In these areas, the thickness of precipitation can be several kilometers, but on average it is small - about 0.5 km. Precipitation is practically absent near mid-ocean ridges.
- Basaltic. These are pillow-type lavas erupted, as a rule, under water. In addition, this layer includes a complex complex of dikes located below - special intrusions - of dolerite (that is, also basalt) composition. Its average thickness is 2-2.5 km.
- Gabbro-serpentinite. It is composed of an intrusive analogue of basalt - gabbro, and in the lower part - serpentinites (metamorphosed ultrabasic rocks). The thickness of this layer, according to seismic data, reaches 5 km, and sometimes more. Its sole is separated from the upper mantle underlying the crust by a special interface - the Mohorovichic boundary.
The structure of the oceanic crust indicates that, in fact, this formation can, in a sense, be considered as a differentiated upper layer of the earth's mantle, consisting of its crystallized rocks, which is overlain from above by a thin layer of marine sediments.
"Conveyor" of the ocean floor
It is clear why there are few sedimentary rocks in this crust: they simply do not have time to accumulate in significant quantities. Growing from spreading zones in the areas of mid-ocean ridges due to the influx of hot mantle matter during the convection process, lithospheric plates, as it were, carry the oceanic crust further and further away from the place of formation. They are carried away by the horizontal section of the same slow but powerful convective current. In the subduction zone, the plate (and the crust in its composition) plunges back into the mantle as a cold part of this flow. At the same time, a significant part of the sediments is torn off, crushed, and ultimately goes to increase the crust of the continental type, that is, to reduce the area of the oceans.
The oceanic type of crust is characterized by such an interesting property as strip magnetic anomalies. These alternating areas of direct and reverse magnetization of basalt are parallel to the spreading zone and are located symmetrically on both sides of it. They arise during the crystallization of basaltic lava, when it acquires remanent magnetization in accordance with the direction of the geomagnetic field in a particular epoch. Since it repeatedly experienced inversions, the direction of magnetization periodically changed to the opposite. This phenomenon is used in paleomagnetic geochronological dating, and half a century ago it served as one of the strongest arguments in favor of the correctness of the theory of plate tectonics.
Oceanic type of crust in the cycle of matter and in the heat balance of the Earth
Participating in the processes of lithospheric plate tectonics, the oceanic crust is an important element of long-term geological cycles. Such, for example, is the slow mantle-oceanic water cycle. The mantle contains a lot of water, and a considerable amount of it enters the ocean during the formation of the basalt layer of the young crust. But during its existence, the crust, in turn, is enriched due to the formation of the sedimentary layer with ocean water, a significant proportion of which, partly in a bound form, goes into the mantle during subduction. Similar cycles operate for other substances, for example, for carbon.
Plate tectonics play a key role in the Earth's energy balance, allowing heat to move slowly away from hot interiors and away from the surface. Moreover, it is known that for the entire geological history the planet gave up to 90% of the heat through the thin crust under the oceans. If this mechanism did not work, the Earth would get rid of excess heat in a different way - perhaps, like Venus, where, as many scientists suggest, there was a global destruction of the crust when the superheated mantle substance broke through to the surface. Thus, the importance of the oceanic crust for the functioning of our planet in a mode suitable for the existence of life is also exceptionally great.
Earth's crust – outer solid shell of the Earth, the upper part of the lithosphere. The Earth's crust is separated from the Earth's mantle by the Mohorovichic surface.
It is customary to distinguish continental and oceanic crust, which differ in their composition, power, structure and age. continental crust located under the continents and their underwater margins (shelf). The earth's crust of the continental type with a thickness of 35-45 km is located under the plains up to 70 km in the area of young mountains. The most ancient sections of the continental crust have a geological age exceeding 3 billion years. It consists of such shells: weathering crust, sedimentary, metamorphic, granite, basalt.
oceanic crust much younger, its age does not exceed 150-170 million years. It has less power – 5-10 km. There is no boundary layer within the oceanic crust. In the structure of the earth's crust of the oceanic type, the following layers are distinguished: unconsolidated sedimentary rocks (up to 1 km), volcanic oceanic, which consists of compacted sediments (1-2 km), basalt (4-8 km).
The stone shell of the Earth is not a single whole. It is made up of individual blocks. – lithospheric plates. Total for the globe There are 7 large and several smaller plates. The large ones include the Eurasian, North American, South American, African, Indo-Australian (Indian), Antarctic and Pacific plates. Within all large plates, with the exception of the last, there are continents. The boundaries of lithospheric plates usually run along mid-ocean ridges and deep-sea trenches.
Lithospheric plates are constantly changing: two plates can be soldered into a single one as a result of a collision; As a result of rifting, the slab can split into several parts. Lithospheric plates can sink into the mantle of the earth, while reaching the earth's core. Therefore, the division of the earth's crust into plates is not unambiguous: with the accumulation of new knowledge, some plate boundaries are recognized as non-existent, and new plates are distinguished.
Within the lithospheric plates are areas with different types of the earth's crust. So, the eastern part of the Indo-Australian (Indian) plate is the mainland, and the western part is located at the base indian ocean. At the African Plate, the continental crust is surrounded on three sides by the oceanic crust. The mobility of the atmospheric plate is determined by the ratio of the continental and oceanic crust within it.
When lithospheric plates collide, folding of rock layers. Pleated belts – mobile, highly dissected parts of the earth's surface. There are two stages in their development. At the initial stage, the earth's crust experiences predominantly subsidence; sedimentary rocks accumulate and metamorphize. At the final stage, the lowering is replaced by an uplift, the rocks are crushed into folds. During the last billion years, there have been several epochs of intense mountain building on Earth: Baikal, Caledonian, Hercynian, Mesozoic and Cenozoic. In accordance with this, different areas of folding are distinguished.
Subsequently, the rocks that make up the folded area lose their mobility and begin to collapse. Sedimentary rocks accumulate on the surface. Stable areas of the earth's crust are formed –
platforms. They usually consist of a folded basement (remains of ancient mountains) overlain from above by layers of horizontally deposited sedimentary rocks that form a cover. In accordance with the age of the foundation, ancient and young platforms are distinguished. Rock areas where the foundation is submerged to a depth and covered by sedimentary rocks are called slabs. The places where the foundation comes to the surface are called shields. They are more characteristic of ancient platforms. At the base of all continents there are ancient platforms, the edges of which are folded areas of different ages. 
The spread of platform and fold areas can be seen on a tectonic geographical map, or on a map of the structure of the earth's crust.
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