27.09.2019

How is continental crust different from oceanic crust? What is the earth's crust

The earth consists of several shells: atmosphere, hydrosphere, biosphere, lithosphere.

Biosphere- a special shell of the earth, the area of vital activity of living organisms. It includes the lower part of the atmosphere, the entire hydrosphere and the upper part of the lithosphere. The lithosphere is the hardest shell of the earth:

Structure:

Earth's crust

mantle (Si, Ca, Mg, O, Fe)

outer core

inner core

center of the earth - temperature 5-6 thousand o C

The core composition is Ni\Fe; core density - 12.5 kg / cm 3;

Kimberlites- (from the name of the city of Kimberley in South Africa), an igneous ultrabasic brecciated rock of an effusive appearance that fills the explosion pipes. It consists mainly of olivine, pyroxenes, pyrope-almandine garnet, picroilmenite, phlogopite, less often zircon, apatite, and other minerals included in a fine-grained groundmass, usually altered by post-volcanic processes to a serpentine-carbonate composition with perovskite, chlorite, etc. d.

eclogite- metamorphic rock consisting of pyroxene with a high content of jadeite minal (omphacite) and grossular-pyrope-almandine garnet, quartz and rutile. In terms of chemical composition, eclogites are identical to the igneous rocks of the basic composition - gabbro and basalts.

The structure of the earth's crust

Layer thickness =5-70 km; highlands - 70 km, seabed - 5-20 km, on average 40-45 km. Layers: sedimentary, granite-gneiss (not in the oceanic crust), granite-bosite (basalt)

The earth's crust is a complex of rocks lying above the Mohorovichic boundary. Rocks are natural aggregates of minerals. The latter are composed of various chemical elements. The chemical composition and internal structure of minerals depend on the conditions of their formation and determine their properties. In turn, the structure and mineral composition of rocks indicate the origin of the latter and make it possible to determine the rocks in the field.

There are two types of the earth's crust - continental and oceanic, which differ sharply in composition and structure. The first, lighter, forms elevated areas - continents with their underwater margins, the second occupies the bottom of the oceanic depressions (2500-3000m). The continental crust consists of three layers - sedimentary, granite-gneiss and granulite-mafic, with a thickness of 30-40 km on the plains to 70-75 km under the young mountains. The oceanic crust up to 6-7 km thick has a three-layer structure. Under a thin layer of loose sediments lies the second oceanic layer, consisting of basalts, the third layer is composed of gabbro with subordinate ultrabasic rocks. The continental crust is enriched in silica and light elements - Al, sodium, potassium, C, in comparison with the oceanic one.

Continental (mainland) crust characterized by high power - an average of 40 km, sometimes reaching 75 km. It consists of three "layers". On top lies a sedimentary layer formed by sedimentary rocks of different composition, age, genesis and degree of dislocation. Its thickness varies from zero (on shields) to 25 km (in deep depressions, for example, the Caspian one). Below lies the "granite" (granite-metamorphic) layer, consisting mainly of acidic rocks, similar in composition to granite. The greatest thickness of the granite layer is observed under young high mountains where it reaches 30 km or more. Within the flat areas of the continents, the thickness of the granite layer decreases to 15-20 km. Under the granite layer lies the third, “basalt”, layer, which also received its name conditionally: seismic waves pass through it at the same speeds with which, under experimental conditions, they pass through basalts and rocks close to them. The third layer, 10-30 km thick, is composed of highly metamorphosed rocks of predominantly mafic composition. Therefore, it is also called granulite-mafic.

Oceanic crust sharply different from the continental. Over most of the area of the ocean floor, its thickness varies from 5 to 10 km. Its structure is also peculiar: under a sedimentary layer with a thickness of several hundred meters (in deep-sea basins) to 15 km (near the continents), there is a second layer composed of pillow lavas with thin layers of sedimentary rocks. The lower part of the second layer is composed of a peculiar complex of parallel dikes of basaltic composition. The third layer of the oceanic crust, 4-7 km thick, is represented by crystalline igneous rocks of predominantly basic composition (gabbro). Thus, the most important specific feature of the oceanic crust is its low thickness and the absence of a granite layer.

1) The structure of the oceanic and continental crust are the same.

2) Continental crust is lighter than oceanic.

3) The youngest layer of the earth's crust is sedimentary.

4) The oceanic crust has a greater thickness than the continental one.

10. What is the largest climate zone in Australia?

1) Tropical 2) Equatorial 3) Temperate 4) Arctic

11. Distribute the southern continents as their area increases:

1) Antarctica 2) Africa 3) South America 4) Australia.

Write your answer in one word

12. What is the most remarkable current of the World Ocean, which is a powerful and deep (2500-3000 m) stream in the ocean. Moving at a speed of 25-30 cm / s, it crosses three oceans and closes the southern subtropical gyres.

Answer:_______________________________

Give a short answer.

13. 2/3 of the Earth's surface is occupied by the ocean. But every year more and more people face the problem of lack of water. Why?

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Where are the boundaries between the plates of the lithosphere? a) along ravines; b) on plains and rivers; c) along mid-ocean ridges and deep-sea trenches; d) along

coastline of the continents. What are the ancient stable areas of lithospheric plates called? a) folded areas; b) platforms; c) plains; d) the bed of the ocean. What is the name of the long-term weather regime that repeats in a given area from year to year? a) climate; b) the weather; c) isotherm; d) the greenhouse effect. The closer to the equator, the: a) the greater the angle of incidence of the sun's rays and the less the earth's surface heats up; b) the smaller the angle of incidence of the sun's rays and the higher the air temperature in the troposphere; the greater the angle of incidence of the sun's rays and the earth's surface heats up more, which means , the air temperature in the surface layer of the atmosphere is higher d) the angle of incidence of the sun's rays is less and the earth's surface heats up less. What winds prevail in tropical latitudes? a) trade winds; b) Western; c) northern; d) monsoons. Where are areas of low pressure on Earth? a) near the equator and in temperate latitudes; b) in temperate and tropical latitudes c) near the poles; d) only over the continents. At what latitudes is the upward movement of air observed? a) in the tropical; b) in the equatorial; c) in the Antarctic; d) in the arctic. In which climatic zone do 2 air masses dominate during the year: temperate and tropical? a) in temperate; b) in the tropics; c) in the subtropical; d) in the subequatorial. For which climate. belts are characteristic of dominance westerly winds, pronounced seasons? a) for the tropical; b) for the equatorial; c) for moderate; d) for the Arctic. What does the salinity of ocean waters depend on? a) on the amount of precipitation; b) from evaporation; c) from the inflow of river waters; d) from all of the above reasons. The temperature of surface ocean waters: a) is the same everywhere; b) varies and depends on latitude; c) changes only with depth; d) changes with depth and with latitude. What is the reason for the alternation of natural zones on land? a) the amount of moisture; b) the amount of heat; c) vegetation; d) the ratio of heat and moisture. Part B. What are the three layers that make up the continental crust? What is the importance of the atmosphere for living organisms? (at least 3 factors) Indicate how all components geographical envelope connected into a single whole? Define the concept of race, and indicate the main human races. Part C. What force moves the plates of the lithosphere? Why do air masses move north and then south during the year? What is altitudinal zonality? And its main pattern.

1. How many years ago did the planet Earth form?

1. 6 -7 billion; 2. 4.5 - 5 billion; 3. 1 - 1.5 billion 4. 700 -800 million
Which line shows the correct sequence of geological eras?
1. Archean - Paleozoic - Proterozoic - Mesozoic - Cenozoic;
2. Proterozoic - Paleozoic - Mesozoic - Archean - Cenozoic;
3. Archean - Proterozoic - Paleozoic - Mesozoic - Cenozoic;
4. Archean - Proterozoic - Paleozoic - Cenozoic - Mesozoic;
The thickness of the continental crust is:
1. less than 5 km; 2. from 5 to 10 km; 3. from 35 to 80 km; 4. from 80 to 150 km.
Where is the Earth's crust the thickest?
1. on the West Siberian Plain; 3. at the bottom of the ocean
2. in the Himalayas; 4. in the Amazonian lowland.
Part of Eurasia is located on the lithospheric plate:
1. African; 3. Indo-Australian;
2. Antarctic; 4.Pacific.
Earth's seismic belts are formed:
1. at the boundaries of the collision of lithospheric plates;
2. at the boundaries of the expansion and rupture of lithospheric plates;
3. in areas where lithospheric plates slide parallel to each other;
4. all options are correct.
Which of the following mountains are among the most ancient?
1. Scandinavian; 2. Ural; 3. Himalayas; 4. Andes.
In which line do mountain structures stand in right order by time of occurrence (oldest to youngest)?
1. Himalayas - Ural Mountains - Cordillera; 3. Ural Mountains - Cordillera - Himalayas;
2. Ural Mountains - Himalayas - Cordilleras; 4. Cordillera - Ural Mountains - Himalayas.
What landforms are formed in the areas of folding?
1. mountains; 2. plains; 3. platforms; 4. lowlands.
Relatively stable and leveled areas of the earth's crust that lie at the base of modern continents are:
1. continental shallows; 2. platforms; 3. seismic belts; 4. islands.
Which statement about lithospheric plates is true?
1. lithospheric plates move slowly over the soft plastic material of the mantle;
2. continental lithospheric plates are lighter than oceanic ones;
3. The movement of lithospheric plates occurs at a speed of 111 km per year;
4. The boundaries of the lithospheric plates exactly correspond to the boundaries of the continents.
If it is established on the map of the structure of the earth's crust that the territory is located in the area of the new (Cainozoic folding), then we can conclude that:
1. it has a high probability of earthquakes;
2. it is on a large plain;
3. there is a platform at the base of the territory.
How does oceanic crust differ from continental crust?
1. the absence of a sedimentary layer; 2. lack of a granite layer; 3. the absence of a granite layer.
Arrange the rock layers of the continental crust from bottom to top:
1. granite layer; 2. basalt layer; 3. sedimentary layer.
Read the text.
On May 21, 1960, an earthquake occurred in the city of Concepcion, located on the territory of the state of Chile, followed by a series of tremors. Buildings collapsed, under the rubble of which thousands of people died. On May 24, at six o'clock in the morning, tsunami waves approached the Kuril Islands and Kamchatka.
Why do earthquakes often occur in this area? Give at least two sentences.

The oceanic crust is primitive in its composition and, in essence, represents the upper differentiated layer of the mantle, overlain from above by a thin layer of pelagic sediments. In the oceanic crust, three layers are usually distinguished, the first of them (upper) is sedimentary.

At the base of the sedimentary layer, thin and irregular metal-bearing sediments with a predominance of iron oxides occur. The lower part of the sedimentary layer is usually composed of carbonate sediments deposited at depths of less than 4-4.5 km. At great depths, carbonate sediments, as a rule, are not deposited, since the microscopic shells of unicellular organisms (foraminifera and cocolithopharid) composing them are easily dissolved in sea water at pressures above 400-450 atm. For this reason, in oceanic depressions at depths greater than 4-4.5 km, the upper part of the sedimentary layer is composed mainly of non-carbonate sediments - red deep-sea clays and siliceous silts. Near island arcs and volcanic islands in the section of the sedimentary sequence, lenses and interlayers of volcanogenic deposits are often found, and near deltas major rivers- and terrigenous sediments. In the open oceans, the thickness of the sedimentary layer increases from the crests of the mid-ocean ridges, where there is almost no precipitation, to their peripheral parts. The average thickness of precipitation is small and, according to A.P. Lisitsyn, is close to 0.5 km, but near the continental margins of the Atlantic type and in areas of large river deltas, it increases to 10-12 km. This is due to the fact that almost all terrigenous material transported from land is deposited in the coastal areas of the oceans and on the continental slopes due to the processes of avalanche sedimentation.

The second, or basaltic, layer of the oceanic crust in the upper part is composed of tholeiitic basaltic lavas (Fig. 5). Pouring out in underwater conditions, these lavas take on bizarre forms of corrugated pipes and pillows, which is why they are called pillow lavas. Below are dolerite dikes of the same tholeiite composition, which are former supply channels through which basaltic magma in rift zones erupted onto the surface of the ocean floor. The basaltic layer of the oceanic crust is exposed in many places on the ocean floor adjacent to the crests of the mid-ocean ridges and the transform faults feathering them. This layer has been studied in detail both by traditional methods of studying the ocean floor (dredging, sampling with soil pipes, photographing), and with the help of underwater manned vehicles, which allow geologists to observe the geological structure of the studied objects and conduct targeted rock sampling. In addition, over the past 20 years, the surface of the basalt layer and its upper layers have been exposed by numerous deep-sea drilling holes, one of which even went through a layer of pillow lavas and entered the dolerites of the dike complex. The total thickness of the basalt, or second, layer of oceanic crust, according to seismic data, reaches 1.5, sometimes 2 km.

Figure 5 The structure of the rift zone and oceanic crust:
1 - ocean level; 2 - precipitation; 3, pillow basaltic lavas (layer 2a); 4, dike complex, dolerites (layer 2b); 5 - gabbro; 6 - layered complex; 7, serpentinites; 8, lherzolites of lithospheric plates; 9 - asthenosphere; 10 - 500 °C isotherm (beginning of serpentinization).

Frequent finds of gabbro-tholeiite inclusions within large transform faults indicate that these dense and coarse-grained rocks are also included in the oceanic crust. The structure of ophiolite covers in the folded belts of the Earth, as is known, are fragments of the ancient oceanic crust thrust in these belts over the former edges of the continents. Therefore, it can be concluded that the dike complex in the modern oceanic crust (as well as in the ophiolite sheets) is underlain from below by a layer of gabbro, which forms the upper part of the third layer of the oceanic crust (layer 3a). At some distance from the crests of the mid-ocean ridges, judging by the seismic data, the lower part of this crustal layer can also be traced. Numerous finds in large transform faults of serpentinites, corresponding in composition to hydrated peridotites and ophiolite complexes similar in structure to serpentinites, suggest that the lower part of the oceanic crust is also composed of serpentinites. According to seismic data, the thickness of the gabbro-serpentinite (third) layer of the oceanic crust reaches 4.5-5 km. Under the crests of the mid-ocean ridges, the thickness of the oceanic crust is usually reduced to 3-4 and even to 2-2.5 km directly under the rift valleys.

The total thickness of the oceanic crust without a sedimentary layer thus reaches 6.5-7 km. From below, the oceanic crust is underlain by crystalline rocks of the upper mantle, which form the subcrustal sections of the lithospheric plates. Beneath the crests of the mid-ocean ridges, the oceanic crust overlies directly above the chambers of basalt melts released from the hot mantle material (from the asthenosphere).

The area of the oceanic crust is approximately equal to 3.0610 × 18 cm 2 (306 million km 2), the average density of the oceanic crust (without precipitation) is close to 2.9 g / cm 3, therefore, the mass of the consolidated oceanic crust can be estimated by the value (5.8 -6.2)x10 24 g. The volume and mass of the sedimentary layer in the deep-water basins of the world ocean, according to A.P. Lisitsyn, are respectively 133 million km 3 and about 0.1 × 10 24 g. The volume of sediments concentrated on the shelves and continental slopes, somewhat larger - about 190 million km 3, which in terms of mass (taking into account the compaction of sediments) is approximately (0.4-0.45) 10 24 g.

The ocean floor, which is the surface of the oceanic crust, has a characteristic relief. In abyssal basins, the ocean floor lies at depths of about 66.5 km, while on the crests of mid-ocean ridges, sometimes dissected by steep gorges, rift valleys, the ocean depths decrease to 2-2.5 km. In some places, the ocean floor comes out on the daytime surface of the Earth, for example, on about. Iceland and in the province of Afar (Northern Ethiopia). In front of the island arcs surrounding the western periphery Pacific Ocean, northeast indian ocean, in front of the arc of the Lesser Antilles and South Sandwich Islands in the Atlantic, as well as in front of the active margin of the continent in Central and South America, the oceanic crust sags and its surface plunges to depths of up to 9-10 km, going further under these structures and forming in front of them narrow and long deep sea trenches.

The oceanic crust is formed in the rift zones of the mid-ocean ridges due to the separation of basalt melts from the hot mantle (from the asthenospheric layer of the Earth) and their outpouring onto the surface of the ocean floor. Every year, in these zones, it rises from the asthenosphere, pours out onto the ocean floor and crystallizes at least 5.5-6 km 3 of basalt melts, which form the entire second layer of the oceanic crust (taking into account the gabbro layer, the volume of basalt melts introduced into the crust increases to 12 km3) . These grandiose tectonomagmatic processes, constantly developing under the crests of the mid-ocean ridges, are unparalleled on land and are accompanied by increased seismicity (Fig. 6).

Figure 6 Earth seismicity; placement of earthquakes
Barazangi and Dorman, 1968

In rift zones located on the crests of mid-ocean ridges, the ocean floor is stretched and pushed apart. Therefore, all such zones are marked by frequent, but shallow-focus earthquakes with the dominance of discontinuous displacement mechanisms.

In contrast, under island arcs and active continental margins, i.e. in zones of plate underthrust, stronger earthquakes usually occur with the dominance of compression and shear mechanisms. According to seismic data, the subsidence of the oceanic crust and lithosphere is traced in the upper mantle and mesosphere to depths of about 600–700 km (Fig. 7). According to tomography data, the subsidence of oceanic lithospheric plates has been traced to depths of about 1400-1500 km and, possibly, deeper - down to the surface of the earth's core.

Figure 7 The structure of the plate underthrust zone in the area of the Kuril Islands:
1 - asthenosphere; 2 - lithosphere; 3, oceanic crust; 4-5 - sedimentary-volcanogenic sequence; 6 - oceanic sediments; isolines show seismic activity in A 10 units (Fedotov et al., 1969); β is the angle of incidence of the Wadati-Benief zone; α is the angle of incidence of the plastic deformation zone.

The ocean floor is characterized by characteristic and rather contrasting banded magnetic anomalies, which usually lie parallel to the crests of mid-ocean ridges (Fig. 8). The origin of these anomalies is associated with the ability of ocean floor basalts to be magnetized by the Earth's magnetic field during cooling, thereby remembering the direction of this field at the time of their outpouring onto the surface of the ocean floor. Given now that the geomagnetic field changed its polarity many times over time, the English scientists F. Vine and D. Matthews back in 1963 for the first time managed to date individual anomalies and show that on different slopes of the mid-ocean ridges these anomalies turn out to be approximately symmetrical in in relation to their crests. As a result, they were able to reconstruct the main patterns of plate movements in certain areas of the oceanic crust in the North Atlantic and show that the ocean floor is moving apart approximately symmetrically away from the crests of the mid-ocean ridges at rates of the order of several centimeters per year. Subsequently, similar studies were carried out in all areas of the World Ocean, and everywhere this pattern was confirmed. Moreover, a detailed comparison of the magnetic anomalies of the ocean floor with the geochronology of the remagnetization of continental rocks, the age of which was known from other data, made it possible to extend the dating of the anomalies to the entire Cenozoic, and then to the Late Mesozoic. As a result, a new and reliable paleomagnetic method for determining the age of the ocean floor was created.

Figure 8 Anomaly Map magnetic field in the Reykjanes Ridge in the North Atlantic
(Heirtzler et al., 1966). Positive anomalies are marked in black; AA is the zero anomaly of the rift zone.

The use of this method led to the confirmation of the previously expressed ideas about the comparative youth of the ocean floor: the paleomagnetic age of all oceans without exception turned out to be only Cenozoic and Late Mesozoic (Fig. 9). Subsequently, this conclusion was brilliantly confirmed by deep-sea drilling at many points on the ocean floor.

It turned out that the age of the depressions of the young oceans (Atlantic, Indian and Arctic) coincide with the age of their bottom, while the age of the ancient Pacific Ocean significantly exceeds the age of its bottom. Indeed, the Pacific Ocean basin has existed at least since the Late Proterozoic (maybe earlier), and the age of the most ancient sections of the ocean floor does not exceed 160 Ma, while most of it was formed only in the Cenozoic, i.e. younger than 67 Ma.

Figure 9 Map of the age of the ocean floor in millions of years
after Larson, Pitman et al., 1985

The "conveyor" mechanism of ocean floor renewal with the constant subsidence of older sections of the oceanic crust and sediments accumulated on it into the mantle under island arcs explains why during the life of the Earth, oceanic depressions did not have time to be covered with sediments. Indeed, at the current rate of backfilling of oceanic depressions with terrigenous sediments carried from the land of 2.210 × 16 g/year, the entire volume of these depressions, approximately equal to 1.3710 × 24 cm 3, would be completely filled up in approximately 1.2 billion years. Now it can be stated with great confidence that the continents and ocean basins have existed together for about 3.8 billion years and no significant backfilling of their depressions has occurred during this time. Moreover, after drilling in all oceans, we now know for certain that there are no sediments older than 160-190 million years on the ocean floor. But this can be observed only in one case - in the case of the existence of an effective mechanism for removing sediment from the oceans. This mechanism, as is now known, is the process of drawing sediments under island arcs and active continental margins in plate underthrust zones, where these sediments are remelted and reattached in the form of granitoid intrusions to the continental crust formed in these zones. This process of remelting of terrigenous sediments and reattachment of their material to the continental crust is called sediment recycling.

The concept of the earth's crust.

Earth's crust

3) upper layer- sedimentary. Its average thickness is about 3 km. In some areas, the thickness of precipitation reaches 10 km (for example, in the Caspian lowland). In some regions of the Earth, the sedimentary layer is absent altogether and a granite layer comes to the surface.

Such areas are called shields (eg Ukrainian Shield, Baltic Shield).

weathering crusts.

Conrad surface

On continental shoals or shelves, the crust is about 25 km thick and is generally similar to the continental crust. However, a layer of basalt may fall out in it. IN East Asia in the region of island arcs (the Kuril Islands, the Aleutian Islands, the Japanese Islands, and others), the earth's crust is of a transitional type. Finally, the earth's crust of the mid-ocean ridges is very complex and still little studied.

There is no Moho boundary here, and the material of the mantle rises along faults into the crust and even to its surface.

The concept of isostasy

isothermal layer

geothermal gradient geothermal stage

Read also:

The shell of the Earth includes the earth's crust and the upper part of the mantle.

The surface of the earth's crust has large irregularities, the main of which are the protrusions of the continents and their depressions - huge oceanic depressions. The existence and mutual arrangement of continents and oceanic depressions is associated with differences in the structure of the earth's crust.

continental crust. It consists of several layers. The top is a layer of sedimentary rocks. The thickness of this layer is up to 10-15 km. Beneath it lies a granite layer. The rocks that compose it are similar in their physical properties to granite. The thickness of this layer is from 5 to 15 km. Under the granite layer is a basalt layer, consisting of basalt and rocks, the physical properties of which resemble basalt. The thickness of this layer is from 10 km to 35 km. Thus, the total thickness of the continental crust reaches 30-70 km.

oceanic crust. It differs from the continental crust in that it does not have a granite layer or it is very thin, so the thickness of the oceanic crust is only 6-15 km.

To determine the chemical composition of the earth's crust, only its upper parts are available - up to a depth of no more than 15-20 km. 97.2% of the total composition of the earth's crust falls on: oxygen - 49.13%, aluminum - 7.45%, calcium - 3.25%, silicon - 26%, iron - 4.2%, potassium - 2.35 %, magnesium - 2.35%, sodium - 2.24%.

Other elements of the periodic table account for tenths to hundredths of a percent.

Most scientists believe that oceanic-type crust first appeared on our planet.

Under the influence of the processes that took place inside the Earth, folds, that is, mountainous areas, formed in the earth's crust. The thickness of the bark increased. This is how the protrusions of the continents were formed, that is, the continental crust began to form.

In recent years, in connection with studies of the earth's crust of oceanic and continental types, a theory of the structure of the earth's crust has been developed, which is based on the idea of lithospheric plates. The theory in its development was based on the hypothesis of continental drift, created at the beginning of the 20th century by the German scientist A. Wegener.

Types of the earth's crust wikipedia
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Hypotheses explaining the origin and development of the earth's crust

The concept of the earth's crust.

Earth's crust is a complex of surface layers of the solid body of the Earth. In the scientific geographical literature there is no single idea of the origin and development of the earth's crust.

There are several concepts (hypotheses) that reveal the mechanisms of formation and development of the earth's crust, the most justified of which are the following:

1. The theory of fixism (from lat. fixus - motionless, unchanging) claims that the continents have always remained in the places they currently occupy. This theory denies any movement of continents and large parts of the lithosphere.

2. The theory of mobilism (from Latin mobilis - mobile) proves that the blocks of the lithosphere are in constant motion. This concept has been especially established in recent years in connection with the receipt of new scientific data in the study of the bottom of the World Ocean.

3. The concept of the growth of continents at the expense of the ocean floor assumes that the original continents were formed in the form of relatively small massifs, which now make up the ancient continental platforms. Subsequently, these massifs grew due to the formation of mountains on the ocean floor adjacent to the edges of the original land cores. The study of the ocean floor, especially in the zone of mid-ocean ridges, gave reason to doubt the correctness of the concept of the growth of continents due to the ocean floor.

4. The theory of geosynclines states that the increase in the size of land occurs through the formation of mountains in geosynclines. The geosynclinal process, as one of the main ones in the development of the earth's crust of the continents, is the basis for many modern scientific explanations of the process of origin and development of the earth's crust.

5. The rotational theory bases its explanation on the proposition that since the figure of the Earth does not coincide with the surface of a mathematical spheroid and is rebuilt due to uneven rotation, zonal bands and meridional sectors on a rotating planet are inevitably tectonically unequal. They react with varying degrees of activity to tectonic stresses caused by intraterrestrial processes.

There are two main types of earth's crust: oceanic and continental. There is also a transitional type of the earth's crust.

Oceanic crust. The thickness of the oceanic crust in the modern geological epoch ranges from 5 to 10 km. It consists of the following three layers:

1) the upper thin layer of marine sediments (thickness is not more than 1 km);

2) middle basalt layer (thickness from 1.0 to 2.5 km);

3) the lower gabbro layer (about 5 km thick).

Continental (continental) crust. The continental crust has a more complex structure and greater thickness than the oceanic crust. Its average thickness is 35-45 km, and in mountainous countries it increases to 70 km. It also consists of three layers, but differs significantly from the ocean:

1) the lower layer composed of basalts (about 20 km thick);

2) the middle layer occupies the main thickness of the continental crust and is conditionally called granite. It is composed mainly of granites and gneisses. This layer does not extend under the oceans;

3) the upper layer is sedimentary. Its average thickness is about 3 km.

In some areas, the thickness of precipitation reaches 10 km (for example, in the Caspian lowland). In some regions of the Earth, the sedimentary layer is absent altogether and a granite layer comes to the surface. Such areas are called shields (eg Ukrainian Shield, Baltic Shield).

On the continents, as a result of weathering of rocks, a geological formation is formed, called weathering crusts.

The granite layer is separated from the basalt Conrad surface , at which the speed of seismic waves increases from 6.4 to 7.6 km/sec.

The boundary between the earth's crust and mantle (both on the continents and on the oceans) runs along Mohorovichic surface (Moho line). The speed of seismic waves on it jumps up to 8 km/h.

In addition to the two main types - oceanic and continental - there are also areas of a mixed (transitional) type.

On continental shoals or shelves, the crust is about 25 km thick and is generally similar to the continental crust. However, a layer of basalt may fall out in it. In East Asia, in the area of island arcs (the Kuril Islands, the Aleutian Islands, the Japanese Islands, and others), the earth's crust is of a transitional type. Finally, the earth's crust of the mid-ocean ridges is very complex and still little studied. There is no Moho boundary here, and the material of the mantle rises along faults into the crust and even to its surface.

The concept of "earth's crust" should be distinguished from the concept of "lithosphere". The concept of "lithosphere" is broader than "the earth's crust". Into the lithosphere modern science includes not only the earth's crust, but also the uppermost mantle to the asthenosphere, that is, to a depth of about 100 km.

The concept of isostasy . The study of the distribution of gravity has shown that all parts of the earth's crust - continents, mountainous countries, plains - are balanced on the upper mantle. This balanced position is called isostasy (from Latin isoc - even, stasis - position). Isostatic equilibrium is achieved due to the fact that the thickness of the earth's crust is inversely proportional to its density. Heavy oceanic crust is thinner than lighter continental crust.

Isostasy is, in essence, not even an equilibrium, but a striving for equilibrium, continuously disturbed and restored again. So, for example, the Baltic Shield after the melting of continental ice of the Pleistocene glaciation rises by about 1 meter per century. The area of Finland is constantly increasing due to the seabed. The territory of the Netherlands, on the contrary, is decreasing. The zero balance line is currently running somewhat south of 60 0 N.L. Modern St. Petersburg is about 1.5 m higher than St. Petersburg during the time of Peter the Great. As data from modern scientific research, even the heaviness of large cities is sufficient for the isostatic fluctuation of the territory under them. Consequently, the earth's crust in the areas of large cities is very mobile. In general, the relief of the earth's crust is a mirror reflection of the Moho surface, the soles of the earth's crust: elevated areas correspond to depressions in the mantle, lower areas correspond to more high level its upper limit. So, under the Pamirs, the depth of the Moho surface is 65 km, and in the Caspian lowland - about 30 km.

Thermal properties of the earth's crust . Daily fluctuations in soil temperature extend to a depth of 1.0 - 1.5 m, and annual fluctuations in temperate latitudes in countries with a continental climate to a depth of 20-30 m. At the depth where the influence of annual temperature fluctuations due to heating ceases earth's surface The sun is a layer of constant temperature of the soil. It is called isothermal layer . Below the isothermal layer deep into the Earth, the temperature rises, and this is already caused by the internal heat of the earth's interior. Internal heat does not participate in the formation of climates, but it serves as the energy basis for all tectonic processes.

The number of degrees by which the temperature increases for every 100 m of depth is called geothermal gradient . The distance in meters, when lowered by which the temperature rises by 1 0 C, is called geothermal stage . The value of the geothermal step depends on the relief, the thermal conductivity of rocks, the proximity of volcanic foci, the circulation of groundwater, etc. On average, the geothermal step is 33 m. In volcanic areas, the geothermal step can be only about 5 m, and in geologically calm areas (for example, on platforms) it can reach 100 m.

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The shell of the Earth includes the earth's crust and the upper part of the mantle. The surface of the earth's crust has large irregularities, the main of which are the protrusions of the continents and their depressions - huge oceanic depressions. The existence and mutual arrangement of continents and oceanic depressions is associated with differences in the structure of the earth's crust.

oceanic crust. It differs from the continental crust in that it does not have a granite layer or it is very thin, so the thickness of the oceanic crust is only 6-15 km.

Other elements of the periodic table account for tenths to hundredths of a percent.

Most scientists believe that oceanic-type crust first appeared on our planet. Under the influence of the processes that took place inside the Earth, folds, that is, mountainous areas, formed in the earth's crust. The thickness of the bark increased. This is how the protrusions of the continents were formed, that is, the continental crust began to form.

Types of the earth's crust wikipedia
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Ocean gorges are primitive in composition and are in fact an upper differentiated coat layer dominated by a thin layer of pelagic sediments. In the oceanic crust, three layers are usually distinguished, of which the first (upper) sediment.

At the bottom of the sedimentary layer, they are often thin and unstable metal deposits dominated by iron oxides.

The lower part of the sediment usually consists of carbonate deposits at depths of less than 4-4.5 km. With deeper recirculation of carbonate, it usually does not precipitate due to their microscopic composition of the shells of single-chain organisms (foraminifera and cocolithopharid) at pressures above 400-450 ATM, immediately dissolved in sea water. For this reason, in marine basins at depths of more than 4-4.5 km to the upper part of the sedimentary layer, only non-calcified sediments mainly consist of dark red clays and silicate heat.

Near the island arc and volcanic islands, lentils and an intertwining of volcanic dykes and a terrigenous dump near the delta of large rivers are often found in part of the sedimentary layers. In open oceans, the thickness of the sediment layer increases from the reefs of the central ocean, where there is almost no sediment in their peripheral areas.

The average thickness of sediments is low and, according to A.P. Lisitsyn, it is close to 0.5 km, near the continental margins of the Atlantic type and in areas of a large rectal delta, increasing to 10-12 km. This is due to the fact that almost all terrigenous materials that land due to floating sedimentation processes are practically embedded in the coastal regions of the oceans and continental slopes.

Another, or basaltic, layer of oceanic crust in the upper part consists of basaltic lavas of Tollei composition (Fig.

5). Under water, the lava will be an unusual form of corrugated pipes and pillows, so these pillows are lava. Below are doleitic crests, tholeiites of the same composition, the former are supply channels for which basaltic magma in tectonic regions is filled on the surface of the seabed.

The basalt layer of the oceanic crust is exposed in many areas of the ocean floor, bordering the mid-ocean reefs and turning defects with a knife. This layer has been extensively reviewed as conventional ocean floor survey methods in (mining, sampling drilling) or with an underwater manned vehicle to enable geologists to take into account the geological structure of objects and perform targeted rock sampling.

In addition, over the past twenty years, the surface of the basalt layer and its upper layers was opened by a number of deep-water boreholes, one of which also passed through the layer of soft lions and entered the lobular complexes of the dike complex. The total thickness of the basalt or other layer of oceanic crust is 1.5, sometimes 2 km, according to seismic data.

Figure 5 The structure of the rift belt of the oceanic crust:
1 - ocean level; 2 - precipitation; 3, soft basaltic lava (layer 2a); 4, complex complex, dolerite (layer 2b); 5 - gabbro; 6, layered complex; 7, serpentinites; 8, lyrosoliths of lithospheric plates; 9 - asthenosphere; 10 - 500°C isotherm (start of serpentinization).

Frequent finds within the framework of the main errors of the transformation of the participation of the gabbrotholian show that these dense and coarse rocks are included in the composition of the oceanic crust.

The structure of ophiolite leaves in strips of land, as we know, fragments the ancient oceanic crust that was shed in these areas at the edge of former continents. Therefore, it can be concluded that the bulk complex in the modern oceanic crust (as well as in the upper ophiolite) is lower than the main layer of gabro properties that makes up the upper part of the oceanic crust of the third layer (layers 3a). At a certain distance from the ridge in the middle of the marine reefs, according to seismic data, there were traces and the lower part of the crust.

Many finds in large convertible serpentinite defects responsible for the composition of hydrated peridotite and serpentinites, similar to the structure of ophiolite complexes, indicate that the lower part of the oceanic crust is composed of serpentinite.

According to seismic data, the thickness of the gabbro-serpentinite (third) layer of the oceanic crust reaches 4.5-5 km. Under the ridge reefs in the middle of the ocean, the thickness of the oceanic crust usually decreases to 3-4 and even to 2-2.5 km just below the river valley.

The total thickness of the oceanic crust without a sedimentary layer, reaching 6.5-7 km. From below, the oceanic crust is covered with crystalline rocks of the upper layer, which form subcrustal regions of lithospheric plates. Beneath the mid-ocean ridge, oceanic crust lies directly above the centers of basaltic hostages separated from hot-coat material (from the asthenosphere).

The area of the oceanic crust is approximately 3.0610 x 18 cm2 (306,000,000 km2), the average density of the oceanic crust (rain) is close to 2.9 g/cm3, hence the cleared mass of the oceanic crust can be estimated (5.8-6 ,2) , where h1024

The volume and mass of the sedimentary layer of the deep-water basins of the World Ocean, according to A.P. Lisitsyn, are 133 million km3 and about 0.1 × 1024 g.

Precipitation is concentrated on the continental shelf and the slope is slightly higher at about 190 million km3, about (0.4-0.45) 1024 depending on weight (including precipitation)

The ocean floor, which is the surface of the oceanic crust, has a characteristic relief.

In the abyssal depression, the ocean floor is at a depth of about 66.5 km, while the coats of arms of the middle oceanic ridge, sometimes carving steep grapes, the fever of the deep ocean depths decreased by 2-2.5 km.

In some places, the ocean floor extends, for example, to the surface of the Earth. Iceland and the province of Afar (Northern Ethiopia). From island arcs around the western edge of the Pacific Ocean, northeast of the Indian Ocean, in front of the arc of the Lesser Antilles and the South Sandwich Islands in the Atlantic, and to the beginning of the active continental margin in Central and South America, the oceanic crust flexes and its surface sinks to a depth of 9 -10 km to go further into these structures and form in front of them and two longer narrow ditches.

The oceanic crust is formed in the tectonic regions of the central oceanic reefs due to the separation that occurs under the basalt melt from the hot layer (Earth's asthenospheric layers) and seepage on the surface of the seabed.

Annually in these areas rises from the astenosfera, poured onto the seabed, and crystallizes at least 5.5-6 km3 of basalt melts, forming the entire second layer of the oceanic crust (including the volume of the gabbro layer implanted in the crust of basalt melts increases to 12 km3) .

These magnificent tectonomagmatic processes, which are constantly developing under the ridge of the mid-ocean ridge, are uncontrollable on land and are accompanied by increased seismicity (Fig. 6).

Figure 6 Earth seismicity; earthquake location
Barazangi and Dorman, 1968

In rift regions located on the reefs of the middle ocean ridge, the ocean floor expands and spreads.

Therefore, all such zones are marked by frequent, but slightly accentuated earthquakes, with the predominant effect of interrupting the mechanisms of movement. On the contrary, under the bends of the islands and the active edges of the continents, i.e.

In areas of panel subduction, as a rule, stronger earthquakes are generated by the predominance of compression and shear mechanisms. According to the earthquake data, the oceanic crust and lithosphere subsidence occurs in the upper layer and mesosphere to a depth of about 600–700 km (Fig. 7). According to the same tomography, the subsidence of oceanic lithospheric plates was traced to a depth of about 1400-1500 km and, if possible, deeper to the surface of the earth's core.

Figure 7 The structure of the underwater section of the plate on the Kuril Islands:
1 - asthenosphere; 2 - lithosphere; 3, oceanic crusts; 4-5 - sedimentary-volcanogenic layers; 6 - oceanic sediments; isolines show seismic activity in A10 units (Fedotov et al., 1969); β is an aspect of the incidence of Wadati-Benif; α is the field of view of the plastic deformation region.

For the ocean floor, there are characteristic and rather contrasting magnetic anomalies of the band, which are usually located parallel to the ridge in the middle of the ocean ridge (Fig.

8). The origin of these anomalies is associated with the possibility of magnetization of ocean floor basalts by cooling by the Earth's magnetic field, thereby resembling the direction of this field during their unloading onto the surface of the ocean floor.

Taking into account that the geomagnetic field repeatedly changed its polarity over a long period of time, the English scientist F. Vine and D. Mathews in 1963 for the first time succeeded in so far separate irregularities, and suggests that various inclinations in the middle of the ocean reefs about these anomalies symmetrical with their coats of arms. As a result, they were able to reconstruct the basic laws of plate motion in parts of the oceanic crust in the North Atlantic and to show that the ocean floor extends roughly symmetrically along the sides of the mid-ocean ridge velocity ridges on the order of a few centimeters per year.

In the future, similar studies were carried out in all areas of the World Ocean, and this picture was confirmed everywhere. In addition, a detailed comparison of magnetic anomalies on the ocean floor with a reversal of the geo-chronology of the magnetization of continental rocks, whose age was known from other sources, will contribute to the spread of Osipovka disturbances throughout the Cenozoic, Mesozoic, and then late.

Therefore, a new and reliable paleomagnetic method for determining the age of the ocean floor has appeared.

Figure 8 Map of magnetic field anomalies in the Reykjanes Ridge in the North Atlantic
(Heirtzler et al., 1966).

Positive anomalies are marked in black; AA is the zero anomaly of the rift zone.

The use of this method led to the confirmation of previously expressed ideas regarding the youth on the seabed: the paleomagnetic receives everything, without exception, that only the oceans and the late kenozoic (Fig.

9). Later, this conclusion was fully confirmed by deep-sea drilling at many points on the ocean floor. In this case, the young age of the cavity of the oceans (Atlantic, Indian and Arctic) coincides with the bottom of their age, the era of the ancient Pacific Ocean, far beyond its bottom. Indeed, the Pacific Basin is at least late Proterozoic (perhaps even earlier) and the age of the oldest areas of the ocean floor is less than 160 million years, while most were created only in the Kenozoic, i.e.

younger than 67 million years.

Figure 9 Map of the ocean floor in millions of years
Larson, Pitman et al. 1985

The mechanism of modernization of the “bicycle” of the ocean floor with the constant submergence of sections of the old ocean crust and accumulated sediments on it in a coat under the island arches explains why during the life of the Earth’s oceanic dams it did not have time to fill the abyss.

In fact, at the current stage of filling the sea basins, destroyed from land sediments of 2210 x 16 g of sediment, the total volume of these wells is approximately 1.3710 x 24 cm 3, it will be completely bombarded by approximately 1.2 ha. Now we can say with certainty that continents and ocean basins coexisted about 3.8 billion years ago, and there was no significant recovery of their depressions at that time. In addition, after drilling operations in all oceans, we now know for sure that there has been no sediment on the ocean floor for more than 160-190 million years.

However, this can be observed only in one case - in the case of an effective mechanism for the removal of sediments in the ocean. This mechanism is now known as a rain extension process based on island bows and active continental margins in subduction areas where these deposits melt and re-adjoin as granitoid intrusion into the emerging continental crust in these zones.

This process of overflowing terrigenous sediments and reattaching their material to the continental crust is called sediment recycling.

Oceanic and continental crust

There are two main types of earth's crust: oceanic and continental. There is also a transitional type of the earth's crust.

Oceanic crust. The thickness of the oceanic crust in the modern geological epoch ranges from 5 to 10 km. It consists of the following three layers:

1) the upper thin layer of marine sediments (thickness is not more than 1 km);

2) middle basalt layer (thickness from 1.0 to 2.5 km);

3) the lower gabbro layer (about 5 km thick).

Continental (continental) crust. The continental crust has a more complex structure and greater thickness than the oceanic crust.

Its average thickness is 35-45 km, and in mountainous countries it increases to 70 km. It also consists of three layers, but differs significantly from the ocean:

1) the lower layer composed of basalts (about 20 km thick);

3) the upper layer is sedimentary.

Its average thickness is about 3 km. In some areas, the thickness of precipitation reaches 10 km (for example, in the Caspian lowland). In some regions of the Earth, the sedimentary layer is absent altogether and a granite layer comes to the surface.

Such areas are called shields (eg Ukrainian Shield, Baltic Shield).

On the continents, as a result of weathering of rocks, a geological formation is formed, called weathering crusts.

The granite layer is separated from the basalt Conrad surface , at which the speed of seismic waves increases from 6.4 to 7.6 km/sec.

The boundary between the earth's crust and mantle (both on the continents and on the oceans) runs along Mohorovichic surface (Moho line). The speed of seismic waves on it jumps up to 8 km/h.

In addition to the two main types - oceanic and continental - there are also areas of a mixed (transitional) type.

On continental shoals or shelves, the crust is about 25 km thick and is generally similar to the continental crust.

However, a layer of basalt may fall out in it. In East Asia, in the area of island arcs (the Kuril Islands, the Aleutian Islands, the Japanese Islands, and others), the earth's crust is of a transitional type. Finally, the earth's crust of the mid-ocean ridges is very complex and still little studied.

There is no Moho boundary here, and the material of the mantle rises along faults into the crust and even to its surface.

The concept of "earth's crust" should be distinguished from the concept of "lithosphere". The concept of "lithosphere" is broader than "the earth's crust".

In the lithosphere, modern science includes not only the earth's crust, but also the uppermost mantle to the asthenosphere, that is, to a depth of about 100 km.

The concept of isostasy .

The study of the distribution of gravity has shown that all parts of the earth's crust - continents, mountainous countries, plains - are balanced on the upper mantle. This balanced position is called isostasy (from Latin isoc - even, stasis - position). Isostatic equilibrium is achieved due to the fact that the thickness of the earth's crust is inversely proportional to its density.

Heavy oceanic crust is thinner than lighter continental crust.

The area of Finland is constantly increasing due to the seabed. The territory of the Netherlands, on the contrary, is decreasing. The zero balance line is currently running slightly south of 600 N. Modern St. Petersburg is about 1.5 m higher than St. Petersburg during the time of Peter the Great. As the data of modern scientific research show, even the heaviness of large cities is sufficient for the isostatic fluctuation of the territory under them.

Consequently, the earth's crust in the areas of large cities is very mobile. In general, the relief of the earth's crust is a mirror image of the Moho surface, the sole of the earth's crust: the elevated areas correspond to depressions in the mantle, and the lower ones correspond to a higher level of its upper boundary. So, under the Pamirs, the depth of the Moho surface is 65 km, and in the Caspian lowland - about 30 km.

Thermal properties of the earth's crust .

Daily fluctuations in soil temperature extend to a depth of 1.0–1.5 m, and annual fluctuations in temperate latitudes in countries with a continental climate to a depth of 20–30 m. a layer of constant soil temperature.

It is called isothermal layer . Below the isothermal layer deep into the Earth, the temperature rises, and this is already caused by the internal heat of the earth's interior. Internal heat does not participate in the formation of climates, but it serves as the energy basis for all tectonic processes.

The number of degrees by which the temperature increases for every 100 m of depth is called geothermal gradient . The distance in meters at which the temperature rises by 10°C is called geothermal stage .

The value of the geothermal step depends on the relief, the thermal conductivity of rocks, the proximity of volcanic foci, the circulation of groundwater, etc. On average, the geothermal step is 33 m.

In volcanic areas, the geothermal step may be as low as about 5 m, while in geologically quiet areas (such as on platforms) it may be as high as 100 m.

TOPIC 5. continents and oceans

Continents and parts of the world

Two qualitatively different types of the earth's crust - continental and oceanic - correspond to two main levels of planetary relief - the surface of the continents and the bed of the oceans.

Structural-tectonic principle of allocation of continents.

The fundamental qualitative difference between the continental and oceanic crust, as well as some significant differences in the structure of the upper mantle under the continents and oceans, make it necessary to distinguish continents not according to their visible surroundings by oceans, but according to the structural-tectonic principle.

The structural-tectonic principle states that, firstly, the mainland includes a continental shelf (shelf) and a continental slope; secondly, at the heart of each continent there is a core or an ancient platform; thirdly, each continental block is isostatically balanced in the upper mantle.

From the point of view of the structural-tectonic principle, the mainland is an isostatically balanced array of the continental crust, which has a structural core in the form of an ancient platform, to which younger folded structures adjoin.

In total, there are six continents on Earth: Eurasia, Africa, North America, South America, Antarctica and Australia.

Each continent contains one platform, and there are six of them at the heart of Eurasia: East European, Siberian, Chinese, Tarim (Western China, the Takla-Makan desert), Arabian and Hindustan. The Arabian and Hindustan platforms are parts of ancient Gondwana that joined Eurasia. Thus, Eurasia is a heterogeneous anomalous continent.

The boundaries between the continents are quite obvious.

The border between North America and South America runs along the Panama Canal. The border between Eurasia and Africa is drawn along the Suez Canal. The Bering Strait separates Eurasia from North America.

Two rows of continents . IN modern geography the following two rows of continents are distinguished:

Equatorial series of continents (Africa, Australia and South America).

2. Northern row of continents (Eurasia and North America).

Outside these rows remains Antarctica - the southernmost and coldest continent.

The current location of the continents reflects the long history of the development of the continental lithosphere.

The southern continents (Africa, South America, Australia and Antarctica) are parts ("fragments") of the Gondwana megacontinent that was united in the Paleozoic.

The northern continents at that time were united into another megacontinent - Laurasia. Between Laurasia and Gondwana in the Paleozoic and Mesozoic was a system of vast marine basins, called the Tethys Ocean. The Tethys Ocean stretched from North Africa, through southern Europe, the Caucasus, Asia Minor, the Himalayas to Indochina and Indonesia.

In the Neogene (about 20 million years ago), an Alpine folded belt arose on the site of this geosyncline.

According to their large sizes supercontinent Gondwana. According to the law of isostasy, it had a thick (up to 50 km) earth's crust, which was deeply immersed in the mantle. Beneath them, in the asthenosphere, convection currents were especially intense, the softened substance of the mantle moved actively.

This led first to the formation of a swelling in the middle of the continent, and then to its splitting into separate blocks, which, under the influence of the same convection currents, began to move horizontally. As proved mathematically (L. Euler), the movement of the contour on the surface of the sphere is always accompanied by its rotation. Consequently, parts of Gondwana not only moved, but also unfolded in geographic space.

The first split of Gondwana occurred at the border of the Triassic and Jurassic (about 190-195 million years ago).

years ago); Afro-America seceded. Then, on the border of the Jurassic and Cretaceous (about 135-140 million years ago), South America separated from Africa. On the border of the Mesozoic and Cenozoic (about 65-70 million years ago).

years ago) the Hindustan block collided with Asia and Antarctica moved away from Australia. In the present geological era, the lithosphere, according to neomobilists, is divided into six slab-blocks, which continue to move.

The collapse of Gondwana successfully explains the shape of the continents, their geological similarity, as well as the history of vegetation and wildlife. southern continents.

The history of the split of Laurasia has not been studied as carefully as Gondwana.

The concept of the parts of the world .

In addition to the geologically determined division of land into continents, there is also a division of the earth's surface into separate parts of the world that has developed in the process of the cultural and historical development of mankind. In total there are six parts of the world: Europe, Asia, Africa, America, Australia with Oceania, Antarctica. On one mainland of Eurasia there are two parts of the world (Europe and Asia), and two continents of the Western Hemisphere (North America and South America) form one part of the world - America.

The border between Europe and Asia is very conditional and is drawn along the watershed line of the Ural Range, the Ural River, the northern part of the Caspian Sea and the Kuma-Manych depression.

Along the Urals and the Caucasus, there are lines of deep faults that separate Europe from Asia.

Area of continents and oceans. The land area is calculated within the current coastline. The surface area of the globe is approximately 510.2 million km 2. About 361.06 million km 2 is occupied by the World Ocean, which is approximately 70.8% of the total surface of the Earth. Approximately 149.02 million hectares fall on land.

km 2, which is about 29.2% of the surface of our planet.

Area of modern continents characterized by the following values:

Eurasia - 53.45 km2, including Asia - 43.45 million km2, Europe - 10.0 million km2;

Africa - 30, 30 million km 2;

North America - 24.25 million km2;

South America - 18.28 million km2;

Antarctica - 13.97 million km2;

Australia - 7.70 million

Australia with Oceania - 8.89 km2.

Modern oceans have an area:

Pacific Ocean - 179.68 million km 2;

Atlantic Ocean - 93.36 million km 2;

Indian Ocean - 74.92 million km 2;

Arctic Ocean - 13.10 million km2.

Between the northern and southern continents, in accordance with their different origin and development, there is a significant difference in the area and nature of the surface.

The main geographical differences between the northern and southern continents are as follows:

1. Incomparable in size with other continents of Eurasia, which concentrates more than 30% of the planet's land.

2. The northern continents have a significant shelf area. The shelf is especially significant in the Arctic Ocean and the Atlantic Ocean, as well as in the Yellow, Chinese and Bering Seas of the Pacific Ocean. The southern continents, with the exception of the underwater continuation of Australia in the Arafura Sea, are almost devoid of a shelf.

3. Most of the southern continents fall on ancient platforms.

In North America and Eurasia, ancient platforms occupy a smaller part of the total area, and most of it falls on the territories formed by the Paleozoic and Mesozoic mountain building. In Africa, 96% of its territory falls on platform sites and only 4% on mountains of Paleozoic and Mesozoic age. In Asia, only 27% are ancient platforms and 77% are mountains of various ages.

4. The coastline of the southern continents, formed mostly by split cracks, is relatively straight; peninsulas and mainland islands few.

The northern continents are characterized by an exceptionally winding coastline, an abundance of islands, peninsulas, often reaching far into the ocean.

Of the total area, islands and peninsulas account for about 39% in Europe, 25% in North America, 24% in Asia, 2.1% in Africa, South America- 1.1% and Australia (excluding Oceania) - 1.1%.

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The structure of the continental crust in different areas.

Continental crust or continental crust - the earth's crust of the continents, which consists of sedimentary, granite and basalt layers.

The average thickness is 35-45 km, the maximum thickness is up to 75 km (under mountain ranges). It is opposed to the oceanic crust, which is different in structure and composition. The continental crust has a three-layer structure. The upper layer is represented by a discontinuous cover of sedimentary rocks, which is widely developed, but rarely has a large thickness. Most of the crust is composed of the upper crust, a layer composed mainly of granites and gneisses of low density and ancient history.

Studies show that most of these rocks were formed very long ago, about 3 billion years ago. Below is the lower crust, consisting of metamorphic rocks - granulites and the like.

5. Types of ocean structures. The land surface of the continents makes up only one third of the Earth's surface. The surface area occupied by the World Ocean is 361.1 ml sq. km. The underwater margins of the continents (shelf plateaus and continental slope) account for about 1/5 of its surface area, the so-called.

“transitional” zones (deep trenches, island arcs, marginal seas) – about 1/10 of the area. The rest of the surface (about 250 ml sq. km.) Is occupied by oceanic deep-water plains, depressions and interoceanic uplifts separating them. The ocean floor differs sharply in the nature of seismicity. It is possible to distinguish areas with high seismic activity and aseismic areas.

The first are extended zones occupied by systems of mid-ocean ridges, stretching across all oceans. These areas are sometimes called oceanic mobile belts. Mobile belts are characterized by intense volcanism (tholeiitic basalts), increased heat flow, sharply dissected relief with systems of longitudinal and transverse ridges, trenches, ledges, and shallow mantle surface.

Seismically inactive areas are expressed in the relief by large oceanic basins, plains, plateaus, as well as underwater ridges limited by fault-type ledges and intra-oceanic swell-like uplifts topped by cones of active and extinct volcanoes. Within the regions of the second type, there are underwater plateaus and uplifts with continental-type crust (microcontinents).

Unlike mobile oceanic belts, these regions, by analogy with the structures of continents, are sometimes called thalassocratons.

6. The structure of the oceanic crust in structures of various types. Oceanic depressions, as the largest negative structures on the surface of the earth's crust, have a number of structural features that allow them to be opposed to positive structures (continents) and compared with each other.

The main thing that unites and distinguishes all oceanic depressions is the low position of the surface of the earth's crust within them and the absence of a geophysical granite-metamorphic layer characteristic of continents.

Mobile belts stretch through all oceanic depressions - mountain systems of mid-ocean ridges with a high heat flow, an elevated position of the mantle layer, which is not typical for continents. The system of mid-ocean ridges, the longest on the surface of the Earth, penetrates and thus connects all oceanic depressions, occupying a central or marginal position in them. It is also characteristic that the tectonic structures of the ocean floor are often closely related to the structures of the continents.

First of all, these connections are expressed in the presence of common faults, in the transitions of rift valleys of mid-ocean ridges into continental rifts (Gulfs of California and Aden), in the presence of large submerged blocks of continental crust in the oceans, as well as depressions with graniteless crust on continents, in transitions trap fields of the continents to the shelf and ocean floor. The internal structure of oceanic depressions is also different. According to the position of the zone of modern spreading, one can contrast the depression Atlantic Ocean with the median position of the Mid-Atlantic Ridge to all other oceans, in which the so-called.

the median ridge is displaced to one of the edges. The internal structure of the Indian Ocean depression is complex. In the western part it resembles the structure of the Atlantic Ocean, in the eastern part it is closer to the western region of the Pacific Ocean. Comparing the structure of the western region of the Pacific Ocean with the eastern part of the Indian Ocean, one draws attention to their certain similarities: the depth of the bottom, the age of the crust (the Cocos and Western Australian Basins of the Indian Ocean, the Western Basin of the Pacific Ocean).

In both oceans, these parts are separated from the continent and the basins of the marginal seas by systems of deep-water trenches and island arcs. The connection of active ocean margins with young folded structures of the continents is observed in Central America, where the Atlantic Ocean is separated from the Caribbean Sea by a deep-sea trench and island arc.

The close relationship between the deep-water trenches separating the ocean basins from the continental massifs with the structures of the continental crust can be traced in the example of the northern extension of the Sunda deep-sea trench, which passes into the Pre-Darakan marginal trough.

Structures of the margins of continents (oceans) and types of crust.

8. Types of boundaries of continental blocks and oceanic depressions. Continental massifs and oceanic depressions can have two types of boundaries - passive (Atlantic) and active (Pacific). The first type is distributed along the framing of most of the Atlantic, Indian, and Arctic oceans. This type is characterized by the fact that through a continental slope of one or another steepness with a system of stepped normal faults, ledges and a relatively gentle continental foot, continental massifs merge with the area of abyssal plains of the ocean floor.

In the zone of the continental foot, systems of deep troughs are known, but they are smoothed out by thick layers of unconsolidated sediments. The second type of margins is expressed along the framing of the Pacific Ocean, along the northeastern margin of the Indian Ocean and on the margin of the Atlantic Ocean adjacent to Central America. In these areas, between the continental massifs and the abyssal plains of the ocean floor, there is a zone of varying width with deep-sea trenches, island arcs, and basins of marginal seas.

Lithospheric plates and types of their boundaries. Studying the lithosphere, which includes the earth's crust and upper mantle, geophysicists came to the conclusion that it contains its own heterogeneities. First of all, these inhomogeneities of the lithosphere are expressed by the presence of strip zones crossing it for the entire thickness with a high heat flow, high seismicity, and active modern volcanism. The areas located between such strip zones are called lithospheric plates, and the zones themselves are considered as the boundaries of lithospheric plates.

At the same time, one type of boundaries is characterized by tensile stresses (borders of divergence of plates), another type is characterized by compressive stresses (borders of convergence of plates), and the third type is characterized by tensions and compressions that occur during shears.

The first type of boundaries are divergent (constructive) boundaries, which on the surface correspond to rift zones.

The second type of boundaries is subduction (when oceanic blocks are pushed under continental ones), obductive (when oceanic blocks are thrust onto continental ones), and collisional (when continental blocks are shifted). On the surface, they are expressed by deep-water trenches, foredeeps, and zones of large thrusts, often with ophiolites (sutures).

The third type of boundaries (shear) is called transform boundaries. It is also often accompanied by discontinuous chains of rift depressions. There are several large and small lithospheric plates. Large plates include the Eurasian, African, Indo-Australian, South American, North American, Pacific, and Antarctic.

Small plates include the Caribbean, Scotia, Philippine, Cocos, Nazca, Arabian, etc.

10. Rifting, spreading, subduction, obduction, collision. Rifting is the process of the emergence and development in the earth's crust of continents and oceans of band-like zones of horizontal stretching on a global scale.

In its upper brittle part, it manifests itself in the formation of rifts expressed in the form of large linear grabens, sliding cavities and related structural forms, and their filling with sediments and (or) products of volcanic eruptions, usually accompanying rifting.

In the lower, more heated part of the crust, brittle deformations during rifting are replaced by plastic tension, leading to its thinning (formation of a “neck”), and, with especially intense and prolonged stretching, to a complete break in the continuity of the pre-existing crust (continental or oceanic) and the formation of "gaps" of the new crust of the oceanic type.

The last process, called spreading, proceeded powerfully in the late Mesozoic and Cenozoic within the modern oceans, and on a smaller (?) scale periodically manifested itself in some zones of older mobile belts.

Subduction - subduction of lithospheric plates of the oceanic crust and mantle rocks under the edges of other plates (according to the concepts of plate tectonics).

Accompanied by the emergence of zones of deep-focus earthquakes and the formation of active volcanic island arcs.

Obduction - thrusting of tectonic plates, composed of fragments of the oceanic lithosphere, onto the continental margin.

As a result, an ophiolite complex is formed. Obduction occurs when any factors disrupt the normal absorption of the oceanic crust into the mantle. One of the mechanisms of obduction is the lifting of the oceanic crust to the continental margin when it enters the subduction zone of the mid-ocean ridge. Obduction is a relatively rare phenomenon and occurred in earth history only periodically.

Some researchers believe that in our time this process is taking place on the southwestern coast of South America.

A continental collision is a collision of continental plates, which always leads to the collapse of the crust and the formation of mountain ranges. An example of a collision is the Alpine-Himalayan mountain belt, formed as a result of the closure of the Tethys Ocean and a collision with the Eurasian plate of Hindustan and Africa. As a result, the thickness of the crust increases significantly, under the Himalayas it is 70 km.

This is an unstable structure, its sides are intensively destroyed by surface and tectonic erosion. In the crust with a sharply increased thickness, granites are smelted from metamorphosed sedimentary and igneous rocks.

The structure and types of the earth's crust

All types of rocks that lie above the Moho boundary take part in the structure of the earth's crust. The ratio of various types of rocks in the earth's crust varies depending on the relief and structure of the earth. In the relief of the Earth, continents and oceans are distinguished - structures of the first (planetary) order, which differ significantly from each other in their geological structure and the nature of development.

Within the continent, structures of the second order are distinguished - plains and mountain structures; in the oceans - the underwater margins of the continents, beds, deep-sea trenches and mid-ocean ridges. The topography of the Earth's surface is dominated by two levels: continental plains and plateaus (altitudes less than 1000 m, occupy more than 70% of the land surface) and flat, relatively leveled spaces of the World Ocean bed, located at depths of 4-6 km below the water level.

Initially, two main types of the earth's crust were distinguished - continental and oceanic, then two more were singled out - subcontinental and suboceanic, characteristic of the continent-ocean transition zones and marginal and inland seas.

C o n t i n t i n t a l crust consists of three layers.

First- upper, represented by sedimentary rocks with a thickness of 0 to 5 (10) km within the platforms, up to 15-20 km in tectonic troughs of mountain structures. Second- granite-gneiss or granite-metamorphic 50% composed of granites, 40% - gneisses and other metamorphosed rocks. Thickness on the plains is 15-20 km, in mountain structures up to 20-25 km. Third- granulite-basite (basite is the main rock, granulite is a metamorphic rock of a gneissic texture of a high (granulite) degree of metamorphism).

Thickness is 10-20 km within platforms and up to 25-35 km in mountain structures. The thickness of the continental crust within the platforms is 35-40 km, in young mountain structures 55-70 km, maximum under the Himalayas and Andes 70-75 km. The boundary between the granite-metamorphic and granulite-mafic layers is called the Konrad section. Deep seismic sounding data showed that the Konrad surface is fixed only in some places.

Research by N. I. Pavlenkova and other specialists, drilling data from the Kolskaya ultra-deep well showed that the continental crust has a more complex structure than that presented above, and an ambiguous interpretation of the data obtained by different authors.

Ocean crust. According to modern data, the oceanic crust has a three-layer structure. Its thickness is from 5 to 12 km, on average 6-7 km.

It differs from the continental crust in the absence of a granite-gneiss layer. First(upper) layer of loose marine sediments with a thickness of a few hundred meters to 1 km. Second, located below, is composed of basalts with interlayers of carbonate and siliceous rocks.

Power from 1 to 3 km. Third, lower, has not yet been opened by drilling. According to dredging data, it is composed of basic igneous rocks of the gabbro type and partially ultrabasic rocks (pyroxenites). Power from 3.5 to 5 km.

S uboceanic crust type confined to the deep basins of the marginal and inland seas (the southern basin of the Caspian, Black, Mediterranean, Okhotsk, Japan, etc.).

In structure, it is close to the oceanic, but differs in a greater thickness of the sedimentary layer - 4-10 km, in some places up to 15-20 km. A similar structure of the crust is characteristic of some deep depressions on land - the central part of the Caspian lowland.

S ub c o n t i n e n t a l characteristic of island arcs (Aleutian, Kuril, etc.) and passive margins of the Atlantic type, where the granite-gneiss layer is wedged out within the continental slope.

In structure, it is close to the mainland, but differs in a smaller thickness - 20-30 km.

Composition and state of matter of the mantle and core of the Earth

Indirect, more or less reliable data on the composition are available for the layer IN(Gutenberg layer).

These are: 1) the outcrop of igneous intrusive ultramafic rocks (peridotites), 2) the composition of rocks that fill diamond pipes, in which, along with peridotites containing garnets, there are eclogites, highly metamorphosed rocks similar in composition to gabbro, but with a density of 3 35-4.2 g/cm3, the latter could be formed only at high pressure. According to the data of the study of intrusive bodies and the experimental study, it is assumed that the layer IN consists mainly of ultramafic rocks of the peridotite type with garnets.

A.E. Ringwood in 1962 called such a breed pyrolite.

The state of matter in the layer IN

In layer IN seismic method established a layer of less dense, as if softened rocks, called asthenosphere(gr.

"asthenos" - weak) or a waveguide. In it, the speed of seismic waves, especially transverse ones, decreases. The state of matter in the asthenosphere is less viscous, more plastic in relation to the higher and lower layers. The solid suprasthenospheric layer of the upper mantle, together with the earth's crust, is called lithosphere(Greek “lithos” - stone).

Horizontal movements of lithospheric plates are associated with this layer. The depth of the asthenosphere under the continents and oceans is different. Research in recent decades has shown a more complex picture of the distribution of the asthenosphere under continents and oceans than before.

Under the rifts of the mid-ocean ridges, the asthenospheric layer in places is located at a depth of 2-3 km from the surface. Within the shields (Baltic, Ukrainian, etc.), the asthenosphere was not detected by the seismic method to a depth of 200-250 km. Some researchers believe that the asthenospheric layer is discontinuous, in the form of asthenolenses. Nevertheless, there are indirect data on the presence of an asthenosphere under the shields of the platforms.

It is known that the Baltic and Canadian shields were subjected to powerful Quaternary glaciations. Under the weight of the ice, the shields sagged (like Antarctica and Greenland now). After the melting of the glaciers and the removal of the load, a rapid rise of the shields occurred in a relatively short period of time - the alignment of the disturbed balance.

Here the phenomenon of isostasy manifests itself (Greek “isos” - equal, “statis” - state) - the state of equilibrium of the masses of the earth's crust and mantle.

According to VE Khain, the asthenosphere under the shields lies deeper than 200-250 km and its viscosity increases, so it is more difficult to detect it by existing methods.

Data on the vertical inhomogeneity of the asthenosphere have been obtained. The depth of the location of the base of the asthenosphere is estimated ambiguously. Some researchers believe that it descends to depths of 300-400 km, others that it captures part of layer C. Taking into account the endogenous activity of the lithosphere and upper mantle, the concept tectonosphere. The tectonosphere includes the earth's crust and upper mantle to depths of 700 km (where the deepest earthquake sources have been recorded).

Composition and state of matter in layers C and D

With depth, temperature and pressure increase, the substance passes into denser modifications.

At depths greater than 400(500) km, olivine and other minerals acquire the structure spinels, the density of which increases by 11% in relation to olivine. At a depth of 700-1000 km, even greater compaction occurs and the spinel structure acquires a denser modification - perovskite. There is a successive change of mineral phases:

pyrolitic to a depth of 400 (420) km,

spinel to a depth of 670-700 km,

perovskite to a depth of 2900 km.

There is another opinion regarding the composition and state of the layers WITH And D.

It is assumed that iron-magnesian silicates decompose into oxides with the closest packing.

Earth's core

The issue is complex and debatable. A sharp drop in P-waves from 13.6 km / s at the base of the D layer to 8-8.1 km / s in the outer core, and S-waves are completely extinguished. The outer core is liquid, it does not have shear strength, unlike a solid. The inner core appears to be solid. According to modern data, the core density is 10% lower than that of the iron-nickel alloy.

Many researchers believe that the core of the Earth consists of iron with an admixture of nickel and sulfur, and possibly silicon or oxygen.

Physical characteristics of the Earth

Density

The density of the Earth is on average 5.52 g/cm3.

The average density of rocks is 2.8 g/cm3 (2.65 according to Palmer). Below the Moho boundary, the density is 3.3-3.4 g/cm3, at a depth of 2900 km - 5.6-5.7 g/cm3, at the upper boundary of the core 9.7-10.0 g/cm3, in the center of the Earth - 12.5-13 g/cm3.

The density of the continental lithosphere is 3-3.1 g/cm3. The density of the asthenosphere is 3.22 g/cm3. The density of the oceanic lithosphere is 3.3 g/cm3.

Thermal regime of the Earth

There are two sources of heat of the Earth: 1.

received from the Sun, 2. carried out from the bowels to the surface of the Earth. Warming by the Sun extends to a depth of no more than 28-30 m, and in some places the first meters.

At some depth from the surface constant belt temperature at which the temperature is equal to the average annual temperature of the area. (Moscow -20 m - +4.20, Paris - 28 m - +11.830). Below the belt of constant temperature, there is a gradual increase in temperature with depth, associated with the deep heat flow. The increase in temperature with depth in degrees Celsius per unit length is called geothermal gradient, and the depth interval in meters at which the temperature rises by 10 is called geothermal step. The geothermal gradient and step are different in different places on the globe.

According to B. Gutenberg, the limits of fluctuations differ by more than 25 times. This indicates different endogenous activity of the earth's crust, different thermal conductivity of rocks. The largest geothermal gradient was noted in the state of Oregon (USA), equal to 1500 per 1 km, the smallest - 60 per 1 km in South Africa.

The average value of the geothermal gradient has long been assumed to be 300 per 1 km, and the corresponding geothermal step is 33 m.

According to V.N. Zharkov, near the Earth's surface, the geothermal gradient is estimated at 200 per 1 km.

If both values are taken into account, then at a depth of 100 km the temperature is 30,000 or 20,000 C. This does not correspond to the actual data. Lava erupting from magma chambers from these depths has a maximum temperature of 1200-12500 C. Taking into account this peculiar thermometer, a number of authors believe that at a depth of 100 km the temperature does not exceed 1300-15000. At higher temperatures, the mantle rocks would be completely melted and S-waves would not pass through them.

Therefore, the average geothermal gradient can be traced to a depth of 20-30 km, and deeper it should decrease. But the change in temperature with depth is uneven. For example: Kola well. A geothermal gradient of 100 per 1 km was calculated. Such a gradient was up to a depth of 3 km, at a depth of 7 km - 1200 C, at 10 km - 1800 C, at 12 km - 2200 C. More or less reliable temperature data were obtained for the base of the layer IN — 1600 + 500 C.

Question about temperature change below the layer IN not resolved.

It is assumed that the temperature in the core of the Earth is in the range of 4000-50000 C.

Earth's gravitational field

Gravity, or gravity, is always perpendicular to the surface of the geoid.

The distribution of gravity on the continents and in the areas of the oceans is not the same at any latitude. Gravimetric measurements of the absolute value of gravity make it possible to identify gravimetric anomalies - areas of increase or decrease in gravity.

An increase in gravity indicates a denser substance, a decrease indicates the occurrence of less dense masses. The magnitude of the acceleration due to gravity is different. On the surface, on average, 982 cm/s2 (at the equator 978 cm/s2, at the pole 983 cm/s2), first increases with depth, then rapidly falls. Near the boundary with the outer core, 1037 cm/s2, decreases in the core, reaches 452 cm/s2 in the F layer, 126 cm/s2 at a depth of 6000 km, and reaches zero in the center.

Magnetism

The earth is a giant magnet with a force field around it.

The geomagnetic field is dipole, the Earth's magnetic poles do not coincide with the geographic ones. The angle between the magnetic axis and the rotation axis is about 11.50.

Distinguish between magnetic declination and magnetic inclination. Magnetic declination is determined by the angle of deviation of the magnetic needle of the compass from the geographic meridian. Declension can be western and eastern. The eastern declination is added to the measured value, the western declination is subtracted. Lines connecting points on the map with the same declination are called zogonami (Greek.

"isos" - equal and "gonia" - angle). Magnetic inclination is defined as the angle between the magnetic needle and the horizontal plane. A magnetic needle suspended on a horizontal axis is attracted by the magnetic poles of the Earth, therefore it is not set parallel to the horizon, forming a larger or smaller angle with it. In the northern hemisphere, the northern end of the arrow goes down, and vice versa in the southern hemisphere. The maximum angle of inclination of the magnetic needle (900) will be at the magnetic pole, it reaches zero in the area close to the geographic equator.

Lines connecting points on the map with the same inclination are called and o kl and m and (Greek “klino” - I incline). The line of zero value of the inclination of the magnetic needle is called the magnetic equator.

The magnetic equator does not coincide with the geographic equator.

The magnetic field is characterized by an intensity that increases from the magnetic equator (31.8 A/m) to the magnetic poles (55.7 A/m). The origin of the constant magnetic field of the Earth is associated with the action of a complex system of electric currents that arise during the rotation of the Earth and accompany turbulent convection (movement) in the liquid outer core.

The Earth's magnetic field affects the orientation of ferromagnetic minerals (magnetite, hematite, and others) in rocks, which, in the process of solidification of magma or accumulation in sedimentary rocks, take the orientation of the Earth's magnetic field existing at that time. Studies of the remanent magnetization of rocks have shown that the Earth's magnetic field has repeatedly changed in geological history: North Pole became southern, and southern - northern, i.e.

there were also inversions (reversal). The scale of magnetic inversions is used to dismember and compare rock masses and determine the age of the ocean floor.

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Earth's crust- the outer solid shell of the Earth (geosphere), part of the lithosphere, from 5 km wide (under the ocean) to 75 km (under the continents). Below the crust is the mantle, which differs in composition and physical qualities - it is more compacted, contains mostly refractory elements. Divides the crust and mantle of the Mohorovichic feature, or the Moho layer, where a sharp acceleration of seismic waves occurs.

There are continental (continental) and oceanic crust, as well as its transitional types: subcontinental and suboceanic crust.

Continental (mainland) crust consists of several layers. The top is a layer of sedimentary rocks. The thickness of this layer is up to 10-15 km. Beneath it lies a granite layer. The rocks that compose it are similar in their physical properties to granite. The thickness of this layer is from 5 to 15 km. Beneath the granite layer is a basalt layer composed of basalt and rocks whose physical characteristics resemble basalt. The thickness of this layer is from 10 km to 35 km. Consequently, the total thickness of the continental crust reaches 30-70 km.

oceanic crust differs from the continental crust in that it does not have a granite layer, or it is very thin, because the thickness of the oceanic crust is only 6-15 km.

To determine the chemical composition of the earth's crust, only its upper parts are available - to a depth of less than 15-20 km. 97.2% of the total composition of the earth's crust falls on: oxygen - 49.13%, aluminum - 7.45%, calcium - 3.25%, silicon - 26%, iron - 4.2%, potassium - 2.35 %, magnesium - 2.35%, sodium - 2.24%.

Other elements of the periodic table account for from 10 to hundredths of a percent.

Sources:

ecosystema.ru - Earth's crust in the Geographic Dictionary on the website of the ecological center "Ecosystem"

en.wikipedia.org - Wikipedia: Earth's crust

glossary.ru - Earth's crust on the Glossary website

geography.kz - Types of the earth's crust

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How is continental crust different from oceanic crust? What is the earth's crust

Oceanic and continental crust

The structure of the continental crust in different areas.

The structure and types of the earth's crust

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