Together with part of the upper mantle, it consists of several very large blocks, which are called lithospheric plates. Their thickness is different - 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 the 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 photographs taken with artificial satellites Earth. They suggest that the configuration in the future may be completely different from the current one, since it is known that the American lithospheric plate is moving towards the Pacific, and the Eurasian one is approaching the African, Indo-Australian, and also the Pacific. The American and African lithospheric plates are slowly moving apart.
The forces that cause the separation of lithospheric plates arise when the mantle substance moves. Powerful ascending flows of this substance push apart the plates, break the earth's crust, forming deep faults in it. Due to underwater outpourings of lavas, strata are formed along the faults. Freezing, they seem to heal wounds - cracks. However, the stretch increases again, and breaks occur again. So, gradually increasing lithospheric plates diverge in different directions.
There are fault zones on land, but most of them are in ocean ridges on where the earth's crust is thinner. The largest fault on land is located in the east. It stretched for 4000 km. The width of this fault is 80-120 km. Its outskirts are dotted with extinct and active ones.
Collision is observed along other plate boundaries. It happens in different ways. If the plates, one of which has an oceanic crust and the other a continental one, approach each other, then the lithospheric plate, covered by the sea, sinks under the continental one. In this case, arcs () or mountain ranges () arise. If two plates with a continental crust collide, then the edges of these plates are crushed into folds of rocks, and mountainous regions are formed. So they arose, for example, on the border of the Eurasian and Indo-Australian plates. The presence of mountainous areas in the inner parts of the lithospheric plate suggests that once there was a boundary between two plates, which were firmly soldered to each other and turned into a single, larger lithospheric plate. Thus, it is possible to make general conclusion: boundaries of lithospheric plates - mobile areas, to which volcanoes, zones, mountainous areas, mid-ocean ridges, deep-water depressions and trenches are confined. It is at the boundary of lithospheric plates that are formed, the origin of which is associated with magmatism.
1. Mark the characteristics of the earth's crust with a red pencil, the mantle in green, and the core in blue.
2. Sign the inner shells of the Earth in figure 9 and indicate at what depth the boundaries between them are.
3. What does the earth's crust consist of? Complete chart 4.
4. Select from the list the most common minerals in the earth's crust 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, deep igneous rocks.
From poured out on earth's surface lavas are formed 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 in origin? Complete chart 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 in table 5 by selecting from the list of rocks of the appropriate origin: peat, gneiss, granite, sandstone, coal, gravel, basalt, crushed stone, chalk, salt, sand, marble, limestone, gypsum, pebbles, clay.
12. How are some rocks transformed into others? Complete chart 7.
13. Mark the characteristics of the continental crust with a red pencil, oceanic - in blue.
14. In Figure 10, the types of the earth's crust are indicated (numbers 1-2); layers of the earth's crust of both types (numbers 3-7); the thickness of the earth's crust (in numbers 8-10).
Determine and write down what is indicated by each number.
1. Oceanic crust.
2. Continental crust.
3. Sedimentary layer of the continental crust.
4. Granite layer of the continental 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 earth's crust, which is 0.5-12 km.
9. The thickness of the continental crust, which is 35-40 km.
10. The thickness of the lithosphere, which is 50 km under the oceans, and 200 km on the continents.
11. The thickness of the continental crust under the mountains, which is 75 km.
15. Complete the sentence.
The lithosphere is a 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. Complete the sentence.
The lithosphere is not monolithic, but is broken 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 shown in figure 11 by numbers 1-7. Draw a red pencil around the borders of their separation, and blue - the collision.
1. South American.
2. African.
3. Eurasian.
4. North American.
5. Pacific.
6. Indo-Australian
7. Antarctic.
19. Complete the sentence.
The totality of all the irregularities of the land surface and the bottom of the seas and oceans is called relief.
20. Complete table 6.
21. Mark the convex landforms with a red pencil, the concave ones with blue.
22. How are landforms divided by size? Complete table 7.
23. Consider Figure 12.
24. In Scheme 8, use the arrows to establish a correspondence between the concepts and their definitions.
25. In diagram 9, use the arrows to set the correspondence between the absolute heights and the colors of the layered coloring. 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 contour lines. These lines represent the terrain.
b) Is a convex or concave landform shown on the map?
Convex.
c) Color the depicted landform using layered coloring.
27. Fill in table 8 by selecting from the list (continents, land and ocean floor plains, ravines, hills, mountain ranges, bumps, beams, intermountain depressions, ocean depressions) landforms created by internal or external forces acting on Earth.
28. What types, depending on the direction, are the slow movements of the earth's crust? 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 shores of Eurasia along with the lithospheric plate at an average speed of 9 cm per year. What is the length of the path passed 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) Mountains in figure 15, a appear in places where lithospheric plates collide, and 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 crumpled into folds.
c) The mountains in figure 15, b are located at the bottom of the oceans and consist of igneous rocks.
31. The plan (Fig. 16) shows the relief of the coastal territory. Fill in blue the part of the terrain that will be flooded by the sea if the earth's crust sinks 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. Crease
2. Reset
3. Gorst
4. Graben
34. In Scheme 11, use the arrows to establish a correspondence between concepts and their definitions.
35. Sign in figure 18 the source and epicenter of the earthquake.
36. Why are areas of frequently recurring earthquakes located on the Earth in belts?
These belts are zones of collision of lithospheric plates.
37. Sign 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 mountain building, volcanism and earthquakes occur in the same areas?
These are the boundaries of the collision of lithospheric plates.
40. Using the text of the textbook and the physical map of the world, give examples of large volcanoes:
a) Mediterranean belt: Vesuvius, Etna, Elbrus, Kazbek, Ararat, Stromboli.
b) Pacific Belt: Klyuchevskaya Sopka, Fujiyama, Popocatepetl, Orizaba, Lullaillaco, Cotopaxi, San Pedro.
41. Under the influence of what internal and external forces the earth's relief is formed? Complete table 9.
42. Mark the characteristics of internal forces with a red pencil, external ones with blue.
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 conditions natural environment.
45. How does weathering affect rocks? Complete table 10.
46. Choose the correct answer.
A strongly elongated lowering of the relief, formed by the long work of the river, is called:
c) valley;
47. What is the role of external forces in the formation of relief? Complete table 11.
48. There are no glaciers on the East European Plain. But many hills between the parallels 50 and 55 ° N. sh. consist of glacial deposits (Valdai and Smolensk-Moscow Uplands, Northern Uvaly). How did they form?
In the anthropogenic period of the Cenozoic era, an ancient glacier passed through this territory, which brought a large amount of deposits.
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 shown in Figure 21 by numbers 1-4.
1. Mountain range.
2. Top of the mountain.
3. Intermountain valley.
4. The slope of the mountain.
51. The longest mountains of land:
b) Andes;
The highest mountains of land:
b) the 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 in terms of 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 landforms 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 Range;
5. Australo-Antarctic uplift.
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 with a "+" the characteristics of the mid-ocean ridges.
59. Choose the correct answer.
The bed of the oceans occupies from the area of \u200b\u200btheir bottom about:
b) 50%.
60. What landforms does the bed of the oceans consist of? Complete diagram 14.
61. Determine and write down which landforms of the bottom of the World Ocean are shown in Figure 24 by numbers 1-5.
1. Shelf (continental shallow).
2. Continental (continental slope).
3. The bed of the ocean.
4. Mid-ocean ridge.
5. Deep sea 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 is correct in meaning.
1. Short, long.
2. Narrow, wide.
3. Uplifts, ridges, depressions.
4. 60m, 600m, 6000m.
5. Extensions, 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 do 80% of the world's population live on the plains (up to a height of 500 m) and only 1% live in the mountains at an altitude of more than 2000 m?
On the plains it is easier to build buildings and roads, to farm.
65. What terrible natural phenomena associated with the earth's crust occur in the mountains?
Earthquakes and volcanic eruptions, landslides, landslides, mudflows (mudflows).
66. What kind of economic activity does a person do in the mountains? How does it change depending on the height of the mountains? Describe this activity in Figure 15.
67. What are the ways to extract minerals? Complete diagram 16.
68. What is the impact of human economic activity on the earth's crust? Complete table 12.
What is the "earth's crust" and what is its structure? What is the difference between rocks by origin?
The Earth's crust is the thin upper shell of the Earth, which has a thickness of 40-50 km on the continents, and 5-10 km under the oceans. On the continents, the crust is three-layered: sedimentary rocks cover granitic rocks, and granitic rocks lie on basalt rocks. Under the oceans, the crust is of an "oceanic", two-layer type; sedimentary rocks lie simply on basalts, there is no granite layer.
Rocks are the material that makes up the earth's crust. Rocks are divided into the following groups:
1. Igneous rocks. They are formed during the solidification of magma in the thickness of the earth's crust or on the surface.
2. Sedimentary rocks. They are formed on the surface, formed from the products of destruction or changes in other rocks, biological organisms.
3. Metamorphic rocks. They are formed in the thickness of the earth's crust from other rocks under the influence of certain factors: temperature, pressure.
How do mountains vary in height? What are plains? Name their types.
Altitude is divided into low, middle and high mountains.
Low mountains (up to 800 m) - with rounded or flat tops and gentle slopes. There are many rivers in these mountains. Examples: Northern Urals, Khibiny, spurs of the Tien Shan.
Middle mountains (800-3000 m). They are characterized by a change in landscape depending on the height. These are the Polar Urals, the Appalachians, the mountains of the Far East.
High mountains (over 3000 m). Basically, these are young mountains with steep slopes and sharp peaks. natural areas change from forests to icy deserts. Examples: Pamir, Caucasus, Andes, Himalayas, Alps, Rocky Mountains.
Plains are fairly large areas of land with slight slopes and slight fluctuations in elevation.
According to the height, the plains are divided into lowlands (below 200 m), uplands (200-500 m) and plateaus (above 500 m).
questions and tasks
1. Compare physical-geographical and tectonic maps.
A comparison of the physical-geographical and tectonic maps shows that stable platform areas correspond to flat areas, while mobile areas at the junction of platforms correspond to mountain areas.
2. According to fig. 17 and physical map in the atlas, name the mountains located in the areas of the Hercynian and Caledonian folding.
Areas of Caledonian folding (460-400 Ma) - formed the Western Sayan, Gorny Altai. Areas of Hercynian folding (300 - 230 million years) - Ural, Rudny Altai.
3. According to fig. 17 identify the lithospheric plates that underlie the territory of Eurasia.
The basis of the territory of Eurasia is the Eurasian, Arabian lithospheric plates, Hindustan.
4. The collision of what plates led to the emergence of the Caucasus, the mountains of Kamchatka, Sakhalin, the Kuril Islands?
The Caucasus Mountains were formed as a result of the collision of the Eurasian plate and the African-Arabian. The mountains of Kamchatka, Sakhalin, the Kuril Islands are the result of the collision of the Eurasian plate with the Pacific.
Unlike other continents, which are large fragments of the fragmented foremothers of Gondwana and Laurasia, Eurasia was formed as a result of the union of ancient lithospheric blocks. Approaching under the influence of internal processes, at different geological times, these blocks were connected by "seams" of folded belts, gradually "composing" the mainland in its modern configuration and size (see figures).
|
And you know that... |
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 (Indostan Peninsula). The northeastern margin of Eurasia is part of the fourth continental plate - the North American. And the eastern part of the mainland with adjacent islands is the zone of interaction between Eurasia and the oceanic Pacific plate. Folded belts are being formed in the junction zones of lithospheric plates. On the southern edge of the Eurasian plate - the Alpine-Himalayan belt: it contains the southern outskirts of Europe, the Crimean Peninsula and Asia Minor, the Caucasus, the Armenian and Iranian highlands, the Himalayas. On the eastern edge of the mainland - the Pacific belt, in which the Kamchatka Peninsula, the Sakhalin Islands, the Kuril Islands, the Japanese, and the Malay Archipelago are located.
AT composition of the Eurasian continent, includes five ancient platforms; all of them are "fragments" of the ancient foremother 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 that formed at different geological times.
All ancient platforms of Eurasia have a two-tiered structure: the rocks of the sedimentary cover lie on the crystalline basement. The foundations are composed of igneous and metamorphic rocks, the sedimentary cover is composed of marine and continental sedimentary rocks. Each platform has plates and shields.
Each of the platforms has its own characteristics. The Chinese platform is fragmented into several disparate blocks, the largest of which are Chinese-Korean and South Chinese. 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 - a rift (see pictures on the right). The sedimentary covers of the platforms differ in thickness and in the rocks that make them up. The platforms of Eurasia are characterized by different intensity 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 have acquired a two-tiered structure. It - young platforms , the largest of which are West European and Scythian (in Europe), West Siberian and Turan (in Asia). The areas that experienced uplifts were folded mountain systems (Tien Shan, Altai, Sayan). During the entire time of their existence, their folds (mountain ranges) were exposed to external forces. Therefore, at present they are severely destroyed, and ancient crystalline rocks are exposed on the surface.
Alpine-Himalayan and Pacific folded belts arose at a later geological time and has not yet been fully formed. They are young. The surface of the mountains, which represent these belts, has not yet had time to collapse. Therefore, it is composed of young sedimentary rocks of marine origin, hiding at a considerable depth the crystalline cores of the folds. These belts are characterized by high seismicity - volcanism is manifested here, earthquakes are concentrated. In such areas, volcanic rocks overlap sedimentary rocks or are embedded in their thickness.
Now let's move on to minerals.
What do we know about the lithosphere?
Tectonic plates are large stable areas of the Earth's crust that are constituent parts 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 activities. It is at the junctions of neighboring plates that phenomena occur, which, as a rule, have catastrophic consequences. These include both volcanic eruptions and strong earthquakes on the scale of seismic activity. In the process of studying the planet, platform 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 the geometry, then we can imagine that one point can be the point of contact of the boundaries of three or more plates. The study of the tectonic structure of the earth's crust shows 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 of the others consist of the so-called block, when the continental plate is soldered into the oceanic one.
The location of the platforms shows that about 90% of the surface of our planet consists of 13 large, stable areas of the earth's crust. The remaining 10% fall on small formations.
Scientists have compiled a map of the largest tectonic plates:
- Australian;
- Arabian subcontinent;
- Antarctic;
- African;
- Hindustan;
- Eurasian;
- Nazca plate;
- Cooker 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 the plates that form the relief of the surface of the planet, but also of the deep part - the mantle. Continental platforms have a thickness of 35 km (in the flat areas) to 70 km (in the zone of mountain ranges). Scientists have proven that the plate in the Himalayas has the greatest thickness. 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 epicenter of the earthquake is located and what is the speed of propagation of seismic waves, calculations are made of the thickness of the sections of the earth's crust.
The process of formation of lithospheric plates
The lithosphere consists mainly of crystalline substances formed as a result of cooling of magma upon reaching the surface. The description of the structure of the platforms speaks of 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 forms. Its properties changed depending on the change in temperature, and new substances were formed. For this reason, minerals that are at different depths differ in their characteristics.
The surface of the earth's crust depends on the influence of the hydrosphere and atmosphere. There is constant weathering. Under the influence of this process, the forms change, and the minerals are crushed, changing their characteristics with 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.
Map of tectonic plates
At first glance it seems that the lithosphere is stable. Its upper part is such, but the lower part, which is distinguished by viscosity and fluidity, is mobile. 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 plates were given above. The process of formation of the earth's crust is ongoing. 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 a year the boundaries of formations are shifting. For this reason, the tectonic map of the world is constantly updated.
Tectonic Plate Cocos
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 boundary runs along the ridge of the East Pacific Rise, and in the east, its boundary can be determined by a conditional line along the coast. North America from California to the Isthmus of Panama. This plate is subducting 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 suffered a large number of earthquakes with a magnitude greater than 8 points. The region is quite densely populated, so in addition to destruction, seismic activity 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, while another is flat, and why earthquakes and volcanic eruptions occur. Various hypotheses were built mainly 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. Mountains formed at the sites of plate faults were studied, chemical composition these plates, and also created maps of regions with tectonic activity.
In the study of tectonics, a special place was occupied by the hypothesis of the displacement of lithospheric plates. Back in the early twentieth century, the German geophysicist A. Wegener put forward a bold theory about why they move. He carefully studied the outline of the west coast of Africa and the east coast 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 the shift of parts of the Earth's crust began.
His research touched upon the processes of volcanism, the stretching of the surface of the ocean floor, and the viscous-liquid structure of the globe. It was the works of A. Wegener that formed the basis of the 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 with a rigid structure and different masses were placed 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 are constantly drifting in ocean waters. Similarly, tectonic structures, being on a plastic substance, are constantly moving. During displacements, the plates constantly collided, came one on top of the other, joints and zones of separation of the plates arose. This process was due to the difference in mass. Areas of increased tectonic activity were formed at the collision sites, mountains arose, earthquakes and volcanic eruptions occurred.
The displacement rate 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 scientific world, magma came to the surface and gradually cooled, creating a new bottom structure, while the "excess" of the earth's crust, under the influence of plate drift, sank into the earth's interior and again turned into liquid magma. Be that as it may, the movements of the continents occur in our time, and for this reason new maps are being created to further study the process of drifting tectonic structures.
- In contact with 0
- Google Plus 0
- OK 0
- Facebook 0
