What lithospheric plates underlie Eurasia. Geological structure of Eurasia. The process of formation of lithospheric plates
Unlike other continents, which are large fragments of the crushed proto-continents of Gondwana and Laurasia, Eurasia was formed as a result of the unification of ancient lithospheric blocks. Coming together under the influence of internal processes, at different geological times these blocks were connected by “seams” of folded belts, gradually “composing” the continent in its modern configuration and size (see pictures).
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The modern continent of Eurasia is located in the junction zone of five large lithospheric plates. Four of them are continental, one is oceanic. Most of Eurasia belongs to the continental Eurasian plate. The southern peninsulas of Asia belong to two different continental plates: the Arabian (Arabian Peninsula) and the Indo-Australian (Indian Peninsula). The northeastern margin of Eurasia is part of the fourth continental plate - the North American. And the eastern part of the continent with the adjacent islands is the zone of interaction between Eurasia and the oceanic Pacific plate. In the zones of junction of lithospheric plates, fold belts are formed. On the southern edge of the Eurasian plate - the Alpine-Himalayan belt: it contains the southern edge of Europe, the Crimea peninsula and Asia Minor, the Caucasus, the Armenian and Iranian plateaus, the Himalayas. On the eastern edge of the continent - the Pacific belt, which contains the Kamchatka Peninsula, Sakhalin Islands, the Kuril Islands, the Japanese Islands, and the Malay Archipelago.
IN composition of continent Eurasia, includes five ancient platforms; all of them are “shards” of the ancient continent Pangea. Three platforms - East European, Siberian and Chinese - after the split of Pangea made up the ancient northern continent of Laurasia. Two - Arabian and Indian - were part of the ancient southern continent of Gondwana. The platforms are “connected” to each other by folded belts formed at different geological times.
All ancient platforms of Eurasia They have a two-tier structure: the rocks of the sedimentary cover lie on a crystalline foundation. The foundations are composed of igneous and metamorphic rocks, the sedimentary cover is composed of marine and continental sedimentary rocks. Each platform contains plates and shields.
Each platform has its own characteristics. The Chinese platform is fragmented into several disparate blocks, the largest of which are Chinese-Korean And South China. The Siberian and Indian platforms are penetrated to the base by ancient powerful cracks and volcanic intrusions (intrusions). The foundation of the East European Platform is dissected by troughs and deep depressions. The Arabian platform is split and stretched into pieces by a modern fault - the rift (see pictures on the right). Sedimentary covers of platforms differ in thickness and the rocks composing them. The Eurasian platforms are characterized by different intensities of modern tectonic movements.
Fold belts in Eurasia formed at different geological times. During ancient folding, the Atlantic and Ural-Mongolian belts were formed. Subsequently, different areas of these belts developed differently: some experienced subsidence, others experienced uplift. Those that sank were flooded by the seas, and a thick layer of marine sediments gradually accumulated on the folded base. These areas acquired a two-tier structure. This - young platforms , the largest of which are Western European and Scythian (in Europe), West Siberian and Turanian (in Asia). The areas that experienced uplift were folded mountain systems (Tian Shan, Altai, Sayan Mountains). Throughout their existence, their folds (mountain ranges) were exposed to external forces. Therefore, at present they are heavily destroyed, and ancient crystalline rocks are exposed on the surface.
Alpine-Himalayan and Pacific pleated belts arose at a later geological time and have not yet been fully formed. They are young. The surface of the mountains that represent these belts has not yet had time to collapse. Therefore, it is composed of young sedimentary rocks of marine origin, hiding at considerable depth the crystalline cores of the folds. These belts are characterized by high seismicity - volcanism manifests itself here, and earthquake sources are concentrated. In such areas, volcanic rocks overlie sedimentary rocks or are embedded in their thickness.
Now let's move on to minerals.
Together with part of the upper mantle, it consists of several very large blocks called lithospheric plates. Their thickness varies - from 60 to 100 km. Most plates include both continental and oceanic crust. There are 13 main plates, of which 7 are the largest: American, African, Indo-, Amur.
The plates lie on a plastic layer of the upper mantle (asthenosphere) and slowly move relative to each other at a speed of 1-6 cm per year. This fact was established by comparing images taken from artificial Earth satellites. They suggest that the configuration in the future may be completely different from the present one, since it is known that the American lithospheric plate is moving towards the Pacific, and the Eurasian plate is moving closer to the African, Indo-Australian, and also the Pacific. The American and African lithospheric plates are slowly moving apart.
The forces that cause the divergence of lithospheric plates arise when the material of the mantle moves. Powerful upward flows of this substance push the plates apart, tearing apart the earth's crust, forming deep faults in it. Due to underwater outpourings of lavas, strata are formed along faults. By freezing, they seem to heal wounds - cracks. However, the stretching increases again, and ruptures occur again. So, gradually increasing, lithospheric plates diverge in different directions.
There are fault zones on land, but most of them are in the ocean ridges, where the earth's crust is thinner. The largest fault on land is located in the east. It stretches for 4000 km. The width of this fault is 80-120 km. Its outskirts are dotted with extinct and active ones.
Along other plate boundaries, plate collisions are observed. It happens in different ways. If plates, one of which has oceanic crust and the other continental, come closer together, then the lithospheric plate, covered by the sea, sinks under the continental one. In this case, arcs () or mountain ranges () appear. If two plates that have continental crust collide, the edges of these plates are crushed into folds of rock, and mountainous regions are formed. This is how they arose, for example, on the border of the Eurasian and Indo-Australian plates. The presence of mountainous areas in the internal parts of the lithospheric plate suggests that once there was a boundary of two plates that were firmly fused with each other and turned into a single, larger lithospheric plate. Thus, we can draw a general conclusion: the boundaries of lithospheric plates are mobile areas to which volcanoes, zones, mountain areas, mid-ocean ridges, deep-sea depressions and trenches are confined. It is at the border of lithospheric plates that they are formed, the origin of which is associated with magmatism.
What do we know about the lithosphere?
Tectonic plates are large, stable sections of the Earth's crust that are components of the lithosphere. If we turn to tectonics, the science that studies lithospheric platforms, we learn that large areas of the earth's crust are limited on all sides by specific zones: volcanic, tectonic and seismic activity. It is at the junctions of neighboring plates that phenomena occur that, as a rule, have catastrophic consequences. These include both volcanic eruptions and earthquakes that are strong on the scale of seismic activity. In the process of studying the planet, plate tectonics played a very important role. Its significance can be compared to the discovery of DNA or the heliocentric concept in astronomy.
If we recall geometry, we can imagine that one point can be the point of contact between the boundaries of three or more plates. Studies of the tectonic structure of the earth's crust show that the most dangerous and rapidly collapsing are the junctions of four or more platforms. This formation is the most unstable.
The lithosphere is divided into two types of plates, different in their characteristics: continental and oceanic. It is worth highlighting the Pacific platform, composed of oceanic crust. Most others consist of what is called a block, where a continental plate is welded into an oceanic one.
The arrangement of the platforms shows that about 90% of the surface of our planet consists of 13 large, stable sections of the earth's crust. The remaining 10% falls on small formations.
Scientists have compiled a map of the largest tectonic plates:
- Australian;
- Arabian subcontinent;
- Antarctic;
- African;
- Hindustan;
- Eurasian;
- Nazca Plate;
- Plate Coconut;
- Pacific;
- North and South American platforms;
- Scotia Plate;
- Philippine plate.
From theory we know that the solid shell of the earth (lithosphere) consists not only of plates that form the relief of the planet’s surface, but also of the deep part - the mantle. Continental platforms have a thickness from 35 km (in flat areas) to 70 km (in mountain ranges). Scientists have proven that the slab is thickest in the Himalaya zone. Here the thickness of the platform reaches 90 km. The thinnest lithosphere is found in the ocean zone. Its thickness does not exceed 10 km, and in some areas this figure is 5 km. Based on information about the depth at which the earthquake epicenter is located and the speed of propagation of seismic waves, the thickness of sections of the earth's crust is calculated.
The process of formation of lithospheric plates
The lithosphere consists predominantly of crystalline substances formed as a result of the cooling of magma as it reaches the surface. The description of the platform structure indicates their heterogeneity. The process of formation of the earth's crust took place over a long period, and continues to this day. Through microcracks in the rock, molten liquid magma came to the surface, creating new bizarre shapes. Its properties changed depending on the change in temperature, and new substances were formed. For this reason, minerals that are located at different depths differ in their characteristics.
The surface of the earth's crust depends on the influence of the hydrosphere and atmosphere. Weathering occurs constantly. Under the influence of this process, forms change, and minerals are crushed, changing their characteristics while maintaining the same chemical composition. As a result of weathering, the surface became looser, cracks and microdepressions appeared. In these places deposits appeared, which we know as soil.
Tectonic plate map
At first glance, the lithosphere appears to be stable. Its upper part is such, but the lower part, which is distinguished by viscosity and fluidity, is movable. The lithosphere is divided into a certain number of parts, the so-called tectonic plates. Scientists cannot say how many parts the earth's crust consists of, since in addition to large platforms, there are also smaller formations. The names of the largest slabs were given above. The process of formation of the earth's crust occurs constantly. We do not notice this, since these actions occur very slowly, but by comparing the results of observations for different periods, we can see how many centimeters per year the boundaries of the formations shift. For this reason, the tectonic map of the world is constantly updated.
Coconut tectonic plate
The Cocos platform is a typical representative of the oceanic parts of the earth's crust. It is located in the Pacific region. In the west, its border runs along the ridge of the East Pacific Rise, and in the east its border can be defined by a conventional line along the coast of North America from California to the Isthmus of Panama. This plate is being pushed under the neighboring Caribbean Plate. This zone is characterized by high seismic activity.
Mexico suffers the most from earthquakes in this region. Among all the countries of America, it is on its territory that the most extinct and active volcanoes are located. The country has experienced a large number of earthquakes with a magnitude greater than 8. The region is quite densely populated, so in addition to destruction, seismic activity also leads to a large number of victims. Unlike Cocos, located in another part of the planet, the Australian and West Siberian platforms are stable.
Movement of tectonic plates
For a long time, scientists have been trying to figure out why one region of the planet has mountainous terrain and another is flat, and why earthquakes and volcanic eruptions occur. Various hypotheses were based primarily on the knowledge that was available. Only after the 50s of the twentieth century was it possible to study the earth's crust in more detail. The mountains formed at the sites of plate fractures, the chemical composition of these plates were studied, and maps of regions with tectonic activity were created.
In the study of tectonics, the hypothesis of the movements of lithospheric plates has occupied a special place. Back at the beginning of the twentieth century, German geophysicist A. Wegener put forward a bold theory about why they move. He carefully examined the outline of the western coast of Africa and the eastern coast of South America. The starting point in his research was precisely the similarity of the outlines of these continents. He suggested that perhaps these continents were previously a single whole, and then a break occurred and parts of the Earth’s crust began to shift.
His research affected the processes of volcanism, stretching of the surface of the ocean floor, and the viscous-liquid structure of the globe. It was the works of A. Wegener that served as the basis for research conducted in the 60s of the last century. They became the foundation for the emergence of the theory of “lithospheric plate tectonics.”
This hypothesis described the model of the Earth as follows: tectonic platforms, having a rigid structure and having different masses, were located on the plastic substance of the asthenosphere. They were in a very unstable state and were constantly moving. For a simpler understanding, we can draw an analogy with icebergs that constantly drift in ocean waters. Likewise, tectonic structures, being on plastic matter, are constantly moving. During displacements, the plates constantly collided, overlapped one another, and joints and zones of moving apart plates appeared. This process occurred due to the difference in mass. In places of collisions, areas with increased tectonic activity were formed, mountains arose, earthquakes and volcanic eruptions occurred.
The rate of displacement was no more than 18 cm per year. Faults formed, into which magma entered from the deep layers of the lithosphere. For this reason, the rocks that make up the oceanic platforms are of different ages. But scientists have put forward an even more incredible theory. According to some representatives of the scientific world, magma came to the surface and gradually cooled, creating a new structure of the bottom, while the “excesses” of the earth’s crust, under the influence of plate drift, sank into the bowels of the earth and again turned into liquid magma. Be that as it may, continental movements continue to occur in our time, and for this reason new maps are being created to further study the process of drift of tectonic structures.
1. Mark the characteristics of the earth’s crust with a red pencil, the mantle with green, and the core with blue.
2. Label the internal shells of the Earth in Figure 9 and indicate at what depth the boundaries between them are located.
3. What does the earth's crust consist of? Complete diagram 4.
4. Select the most common minerals in the earth’s crust from the list and mark them with a “+” sign
5. In Diagram 5, use the arrows to establish a correspondence between the concepts and their definitions.
6. Complete the sentences.
From magma slowly cooling at depth, they form deep igneous rocks.
Lava that spills onto the earth's surface forms erupted (volcanic) igneous rocks.
7. From the list (rock salt, marble, sand, clay, granite, limestone, chalk, basalt, gypsum) select:
a) deep igneous rock:
granite;
b) erupted (volcanic) rock:
basalt.
8. How do sedimentary rocks differ by origin? Complete diagram 6.
9. From the list (gneiss, granite, marble, sand, basalt, gypsum, peat) select:
a) sedimentary clastic rock:
sand;
b) sedimentary rock of chemical origin:
gypsum;
c) sedimentary rock of organic origin:
peat.
10. Underline the name of the most common metamorphic rock in the earth’s crust.
Sand, gravel, basalt, chalk, marble, granite, gneiss, coal, rock salt, gypsum.
11. Fill out table 5, selecting rocks of the appropriate origin from the list: peat, gneiss, granite, sandstone, coal, gravel, basalt, crushed stone, chalk, salts, sand, marble, limestone, gypsum, pebbles, clay.
12. How are some rocks transformed into others? Complete diagram 7.
13. Mark the characteristics of the continental crust with a red pencil, and the oceanic crust with a blue pencil.
14. Figure 10 shows the types of the earth’s crust (numbers 1-2); layers of the earth's crust of both types (numbers 3-7); thickness of the earth's crust (in numbers 8-10).
Identify and write down what each number represents.
1. Oceanic crust.
2. Continental crust.
3. Sedimentary layer of the continental crust.
4. Granite layer of the continental earth's crust.
5. Basalt layer of the continental crust.
6. Basalt layer of the oceanic crust.
7. Sedimentary layer of the oceanic crust.
8. The thickness of the oceanic crust is 0.5-12 km.
9. The thickness of the continental crust is 35-40 km.
10. The thickness of the lithosphere is 50 km under the oceans and 200 km on the continents.
11. The thickness of the continental crust under the mountains is 75 km.
15. Finish the sentence.
Lithosphere is the solid shell of the Earth, consisting of the earth's crust and the upper part of the mantle.
16. Mark the characteristics of the lithosphere with a “+” sign.
17. Finish the sentence.
The lithosphere is not monolithic, but is divided by faults into separate blocks, which are called lithospheric plates.
18. Using Figure 44 of the textbook, determine which seven of the largest lithospheric plates of the Earth are depicted in Figure 11 by numbers 1-7. Circle the boundaries of their separation with a red pencil, and the collisions with a blue pencil.
1. South American.
2. African.
3. Eurasian.
4. North American.
5. Pacific.
6. Indo-Australian
7. Antarctic.
19. Finish the sentence.
The totality of all irregularities in the surface of the land and the bottom of the seas and oceans is called relief.
20. Fill out table 6.
21. Mark convex relief shapes with a red pencil, concave ones with a blue pencil.
22. How are landforms divided by size? Fill out table 7.
23. Consider Figure 12.
24. In diagram 8, use the arrows to establish a correspondence between the concepts and their definitions.
25. In diagram 9, use the arrows to establish a correspondence between absolute heights and layer-by-layer colors. Color the drawing with the appropriate colors.
26. Consider a fragment of the map in Figure 13.
a) Complete the sentences.
The lines shown on the map are called contours. These lines are used to depict the terrain.
b) Is the landform shown on the map convex or concave?
Convex.
c) Color the depicted relief shape using layer-by-layer coloring.
27. Fill out table 8 by selecting from the list (continents, land plains and ocean floors, ravines, hills, mountain ranges, hummocks, gullies, intermountain depressions, ocean depressions) landforms created by internal or external forces acting on the Earth.
28. Depending on the direction, what types of slow movements of the earth’s crust are divided? Complete diagram 10.
29. Figure 14, a shows the position of the Hindustan Peninsula 70 million years ago, Figure 14, b - at the present time. The island moved to the coast of Eurasia along with the lithospheric plate at an average speed of 9 cm per year. What is the length of the route covered by Hindustan?
The length of the route of the Hindustan Peninsula is
30. Look at Figure 15 (a and b) and complete the sentences.
a) The mountains in Figure 15, a arise in places where lithospheric plates collide, and the mountains in Figure 15, b - in places where they diverge.
b) The mountains in Figure 15, a are located on land and consist of rocks crushed into folds.
c) The mountains in Figure 15, b are located on the bottom of the oceans and consist of igneous rocks.
31. The plan (Fig. 16) shows the relief of the coastal territory. Color blue the part of the area that would be flooded by the sea if the earth's crust dropped 6 m.
Earthquakes are rapid vibrations of the earth's crust caused by tremors.
33. List the types of rock occurrence shown in Figure 17.
1. Wrinkling into folds
2. Reset
3. Gorst
4. Graben
34. In diagram 11, use the arrows to establish a correspondence between the concepts and their definitions.
35. Label the source and epicenter of the earthquake in Figure 18.
36. Why are areas of frequently recurring earthquakes located on the Earth in belts?
These belts are collision zones of lithospheric plates.
37. Label in Figure 19 the names of the parts of the volcano and volcanic emissions (substances).
38. Figure 20 shows two types of volcanic eruptions. Describe them.
a) a fissure-type volcano.
b) a crater-type volcano.
39. Why do mountain building, volcanism and earthquakes occur in the same areas?
These are the boundaries of the collision of lithospheric plates.
40. Using the textbook text and a physical map of the world, give examples of large volcanoes:
a) Mediterranean belt: Vesuvius, Etna, Elbrus, Kazbek, Ararat, Stromboli.
b) Pacific belt: Klyuchevskaya Sopka, Fuji, Popocatepetl, Orizaba, Llullaillaco, Cotopaxi, San Pedro.
41. Under the influence of what internal and external forces is the Earth’s topography formed? Fill out table 9.
42. Mark the characteristics of internal forces with a red pencil, external ones with a blue pencil.
43. What types of weathering do you know? Complete diagram 12.
44. Complete the sentences.
Weathering is the destruction and change of rocks on the land surface under the influence of natural environmental conditions.
45. How does weathering affect rocks? Fill out table 10.
46. Choose the correct answer.
A highly elongated depression in the relief formed by the long-term operation of a river is called:
c) valley;
47. What is the role of external forces in the formation of relief? Fill out table 11.
48. There are no glaciers on the East European Plain. But many hills between parallels 50 and 55° N. w. consist of glacial deposits (Valdai and Smolensk-Moscow uplands, Northern Uvaly). How were they formed?
During the anthropogenic period of the Cenozoic era, an ancient glacier passed through this territory, which brought a large amount of sediment.
49.Choose the correct answer.
Sandy crescent-shaped hills that form in deserts are called:
c) dunes.
50. Determine which elements of the structure of a mountainous country are depicted in Figure 21 by numbers 1-4.
1. Mountain range.
2. Top of the mountain.
3. Intermountain Valley.
4. Mountainside.
51.Longest mountains on land:
b) Andes;
The highest mountains on land:
b) Himalayas.
52.How do mountains differ in absolute height? Complete diagram 13.
53. Figure 22 shows plains with different absolute heights. What are their names?
a) lowland;
b) elevation;
c) plateau.
54. Choose the correct answer.
The largest lowlands by area are:
d) Amazonian and West Siberian.
55. Choose the correct statement.
b) Plains occupy 60% of the land area, and mountains - 40%.
56. Using a physical map of the world, determine which forms of relief of the ocean floor are indicated in Figure 23 by numbers 1-5. Write down the name of each of them.
1. North Atlantic Ridge;
2. South Atlantic Ridge;
3.East Pacific Rise;
4. West Indian Ridge;
5. Australian-Antarctic rise.
57. Choose the correct answer.
Underwater mountain ranges with oceanic crust, forming a single mountain system with a length of more than 60 thousand km, are called:
c) mid-ocean ridges.
58. Mark the characteristics of mid-ocean ridges with a “+” sign.
59.Choose the correct answer.
The bed of the oceans occupies about the area of their bottom:
b) 50%.
60. What landforms does the ocean floor consist of? Complete diagram 14.
61. Determine and write down what forms of relief of the bottom of the World Ocean are shown in Figure 24 by numbers 1-5.
1. Shelf (continental shallows).
2. Continental (continental slope).
3. Ocean bed.
4. Mid-ocean ridge.
5. Deep water trench.
62. Insert into the sentence instead of each number one of the words given in the list under the corresponding number so that the sentence turns out to be correct in meaning.
1. Short, long.
2. Narrow, wide.
3. Uplifts, ridges, depressions.
4. 60 m, 600 m, 6000 m.
5. Movements, collisions.
Deep-sea trenches are long and narrow oceanic depressions with a depth of more than 6000 m, located at the boundaries of the collision of lithospheric plates.
63. Choose the correct answer.
Earth's deepest trench:
c) Marian.
64. Why does 80% of the Earth's population live on the plains (up to an altitude of 500 m) and only 1% in the mountains at an altitude of more than 2000 m?
On the plains it is easier to build buildings and roads, and conduct agriculture.
65. What threatening natural phenomena associated with the earth’s crust occur in the mountains?
Earthquakes and volcanic eruptions, landslides, mudflows (mudflows).
66. What economic activity does a person engage in in the mountains? How does it change depending on the height of the mountains? Describe this activity in Figure 15.
67. What methods are used to extract minerals? Complete diagram 16.
68. What is the impact of human economic activity on the earth’s crust? Complete Table 12.
In my understanding, the lithospheric plate was something like a piece of a leaf floating on the water surface of a puddle. In fact, these substances are colossal in size, and their movement even of a few millimeters entails tsunamis, earthquakes, eruptions...
What is a lithospheric plate
Scientists call the lithospheric plate stable and solid area of the earth's surface, both oceanic and continental. In essence, these are huge pieces of magma that came to the surface of the Earth several billion years ago and solidified during its cooling. They are still “drifting” along that same magma. At the borders where they collide, natural disasters occur that claim a large number of lives, the ecosystem is destroyed, and the climate changes. The emergence of continents is associated with the movement of lithospheric plates even before the appearance of life on Earth.
The structure of the lithospheric plate
When considering the issue of the origin of lithospheric plates, it would not be amiss to focus on their structure. This is necessary in order to understand what features they differ from their component parts.
So, lithospheric plate consists from more stable formations - platforms. As a rule, the flat part of the plate is called a platform. At the foot of each platform is crystal shield.
Crystal Shield- this is the base of a platform, the characteristic feature of which is mineral deposits that are relatively shallow from the earth’s surface.
Lithospheric plates of Russia
Russia occupies its territory only two continental lithospheric plates:
Eurasian lithospheric plate includes the following stable crustal formations:
1. Scythian platformsA- the smallest territory of Russia is located on it. These are the Rostov and Volgograd regions, the Stavropol and Krasnodar territories.
2. East European Platform- european part of Russia.
3. West Siberian Platform- located between the Ural Mountains and Lake Baikal.
4. Siberian platform- located within the territory from Lake Baikal to the hills of Kamchatka.
5. Anabar, Aldan (Amur plate), and Baltic crystalline shields.
The volcanoes of Kamchatka are part of North American Plate. The Kamchatka mountain ranges are the site of the collision of two lithospheric plates, on which the territory of Russia is located - the North American and Eurasian lithospheric plates.
East of Sakhalin there is another plate - the Pacific. I think that it belongs to the territorial waters of Russia is doubtful.
