Set of irregularities earth's surface form it relief. Landforms vary in size, origin, and development history. The relief of the earth, or more correctly, the earth's surface, is the result of a complex interaction of internal and external forces. Internal forces, the energy of which is provided by internal energy the Earth itself, create large irregularities. External forces smooth out these irregularities, creating smaller irregularities.
Most large forms relief of the earth- ridges of continents and depressions of oceans. Their distribution is determined by the structure of the earth's crust - the presence or absence of a granite layer. There are currently six continents on Earth. Land on the Earth's surface is distributed unevenly. We can distinguish two conventional hemispheres on the planet - oceanic and continental. In the center of the first is the Pacific Ocean, in the center of the second is Africa. The prevailing heights within the land are about 800 m, the average depths of the ocean are about 3500 m. The surface of the land and the ocean bottom is complicated by lower-order irregularities.
The main landforms are mountains and plains. About 60% of the land surface is occupied plains. These are vast areas of the earth's surface with small fluctuations in heights (about 200 m), relatively low elevated above sea level. By absolute altitude the plains are divided on lowlands (height from 0 to 200 m), hills (200-500 m) and plateaus (above 500 m). By the nature of the surface- flat, hilly and stepped. Lowland areas are the most populated and developed by people. Most cities and transport routes and the main tracts of cultivated land are concentrated on them.
They call them mountains distinct elevations on the earth's surface with heights of more than 200 m, with well-defined slopes and bases. Mountainous regions occupy about 40% of the land surface. Most of the mountains on Earth stretch in mutually perpendicular directions, close to sublatitudinal or submeridional. By height, mountains are divided into low (with altitudes up to 1000 m), medium-altitude (1000-2000 m) and high (over 2000 m). According to the structure of mountains there are folded, folded - blocky and blocky. According to geomorphological age, they distinguish young, rejuvenated and reborn mountains. Mountains of tectonic origin predominate on land, while mountains of volcanic origin predominate in the oceans.
Within the land, the distribution of mountainous and lowland areas is determined by the structure of the earth's crust. On the platforms, due to the horizontal occurrence of rocks, there are plains. In folded areas, rocks occur in the form of folds, and in the relief they correspond to mountains.
The structure of the earth's crust determines not only the relief, but also the placement of mineral resources. Minerals of sedimentary origin (oil, gas, coal, salts) are concentrated in the sedimentary rocks of the platform cover. Minerals of igneous origin - in folded areas and crystalline platform basements. The greatest variety of minerals is characteristic of ancient platforms.
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Relief is the shape that the earth's surface has. The earth's topography is prone to dynamic changes. Small relief forms can change quite quickly, while changes in larger ones occur over the course of centuries.
Concept of the Earth's relief
The Earth's topography can change under the influence of various factors, in particular volcanic eruptions and earthquakes. Such factors are called endogenous. The destructive effect on the relief of wind, water, as well as flora and fauna is called exogenous impact.
In addition to these factors, the earth's topography is significantly influenced by human activity and its active economic intervention in the subsoil. However, the anthropogenic factor cannot influence dramatic changes in the structure of the relief.
Basic landforms of the Earth
The relief of the earth's surface is expressed in four forms: plains, highlands, shelves and mountains. Plains- the most stable areas of the earth's surface. On flat surfaces, the possibilities of changing the relief under the influence of various factors are minimal.
Plains include lowlands (up to 200 m above sea level), hills (200-500m), plateaus (more than 500m).
Mountains are areas of land that rise to a height of more than 600m above sea level. Mountains consist of peaks and steep slopes. Mountains can form highlands and ridges, which form a slight difference in elevation levels.
Highlands They are a system of mountain ranges, individual mountains and small valleys. The most famous highlands: Tien Shan, Pamir, Cordillera.
Shelf- This is a form of relief that is inherent exclusively to the bottom of the world's oceans. The shelf is a collection of vast areas of the seabed, often located along the coast.
Age of relief forms
On external characteristics The earth's topography is influenced by many factors. One of them is the age of the Earth's topography. Despite the fact that relief forms belong to the category of inanimate nature, from the moment of their emergence they undergo several evolutionary factors that can be identified with human life.
The age of relief forms is most clearly visible in the example of mountain peaks. Young mountains are usually high and are constantly in the process of dynamic growth. After the growth stage stops, the process of aging of the mountains begins.
Over the years, mountain systems begin to slowly lose their height - the slopes become gentle, they are covered with forest thickets. Mountain rivers lose their speed and turn into calm reservoirs. Several centuries after the growth of mountains ceases, mountain rivers may disappear altogether, leaving behind only wide valleys.
Relative elevation differences gradually begin to decrease. At this moment, the process of disappearing mountains begins. Territories that were previously mountain peaks, can turn into plateaus.
The geographical concept of relief includes the shape (outline) of the outer surface of the lithosphere. These include irregularities of land, and the bottom of oceans and seas. The relief of the Earth's surface consists of positive (convex) and negative (concave) shapes.
Convex relief forms include various elevations (mountains, hills), and concave relief forms include various lowlands and depressions. The relief of the Earth's surface directly depends on the processes occurring in the thickness of the earth's crust. These processes are called tectonic. For example, positive landforms (hills, mountain ranges) arise mainly in places where lithospheric plates collide, which slowly move under the influence of complex processes occurring inside the planet. Earthquakes and volcanic eruptions often occur in such areas. For those points on the earth's surface under which there is an ancient powerful lithospheric plate called a platform, such processes are very rare. Landforms Here mostly concave, and the mountains and hills encountered are low.
Relief formation the earth's surface has been happening since ancient times. This process is quite lengthy, since movement of the earth's crust occur slowly - only a few centimeters per year. Billions of years have passed from the formation of the Earth to the present day. Now we can only guess what our planet looked like then. According to experts, there was once only one huge continent on Earth, which then broke up into several smaller ones. Many times during this time, some areas of modern land were under water, and what is now the bottom of the oceans and seas was dry land.
But not only tectonic processes influence the relief of the Earth. Such external processes like weathering, the passage of glaciers and others, also significantly changed the appearance of the planet's surface. Man also influences relief structure, changing it during its activities. Although human influence cannot yet compare with the natural processes that have occurred during many years, many small landforms (for example, ravines) are the result of his actions.
HIGHEST PEAKS OF THE SIX PARTS OF THE WORLD:
- Asia - Chomolungma (8848 m) South America- Aconcagua (6962 m)
- North America - McKinley (6194 m)
- Africa - Kilimanjaro (5895 m) Europe - Elbrus (5642 m)
- Antarctica - Vinson Massif (4892 m)
LARGEST LOWLANDS
- The Amazon is the most extensive in the world: more than 5 million km 2
- The Gobi Plain is the largest in Central Asia, named after the desert of the same name
- Great Plains - foothill plateau in North America
- The Mesopotamian lowland is one of the most famous, as the great civilization of Mesopotamia was born here
- The East European (Russian) Plain is one of the richest in mineral resources, largest deposit- Kursk magnetic anomaly
The totality of the unevenness of the earth's surface forms it relief. Landforms vary in size, origin, and development history. The relief of the earth, or more correctly, the earth's surface, is the result of a complex interaction of internal and external forces. Internal forces, the energy of which is provided by the internal energy of the Earth itself, create large irregularities. External forces smooth out these irregularities, creating smaller irregularities.
The largest landforms of the Earth- ridges of continents and depressions of oceans. Their distribution is determined by the structure of the earth's crust - the presence or absence of a granite layer. There are currently six continents on Earth. Land on the Earth's surface is distributed unevenly. We can distinguish two conventional hemispheres on the planet - oceanic and continental. In the center of the first is the Pacific Ocean, in the center of the second is Africa. The prevailing heights within the land are about 800 m, the average depths of the ocean are about 3500 m. The surface of the land and the ocean bottom is complicated by lower-order irregularities.
The main landforms are mountains and plains. About 60% of the land surface is occupied plains. These are vast areas of the earth's surface with small fluctuations in heights (about 200 m), relatively low elevated above sea level. According to absolute height, the plains are divided on lowlands (height from 0 to 200 m), hills (200-500 m) and plateaus (above 500 m). By the nature of the surface- flat, hilly and stepped. Lowland areas are the most populated and developed by people. Most cities and transport routes and the main tracts of cultivated land are concentrated on them.
They call them mountains distinct elevations on the earth's surface with heights of more than 200 m, with well-defined slopes and bases. Mountainous regions occupy about 40% of the land surface. Most of the mountains on Earth stretch in mutually perpendicular directions, close to sublatitudinal or submeridional. By height, mountains are divided into low (with altitudes up to 1000 m), medium-altitude (1000-2000 m) and high (over 2000 m). According to the structure of mountains there are folded, folded - blocky and blocky. According to geomorphological age, they distinguish young, rejuvenated and reborn mountains. Mountains of tectonic origin predominate on land, while mountains of volcanic origin predominate in the oceans.
Within the land, the distribution of mountainous and lowland areas is determined by the structure of the earth's crust. On the platforms, due to the horizontal occurrence of rocks, there are plains. In folded areas, rocks occur in the form of folds, and in the relief they correspond to mountains.
The structure of the earth's crust determines not only the relief, but also the placement of mineral resources. Minerals of sedimentary origin (oil, gas, coal, salts) are concentrated in the sedimentary rocks of the platform cover. Minerals of igneous origin - in folded areas and crystalline platform basements. The greatest variety of minerals is characteristic of ancient platforms.
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The natural features of continents and oceans are largely determined by their topography. Continental topography is an important factor in climate formation, as well as human settlement and economic activity. The topography of the bottom of the oceans determines their depth, and therefore the volume of water, the presence of islands and much more.
Rice. 3. Lithospheric plates ()
The boundaries of lithospheric plates do not coincide with the boundaries of continents, although sometimes they are close to them. The idea of mountain formation is also associated with the movement of plates. Where two plates with continental crust collide, mountain systems planetary scale. This explains the emergence of the Himalayas - the highest part of the Alpine-Himalayan mountain belt.
The correctness of the hypothesis of splits, divergence and connection of continents is also confirmed by the geological structure of the land of different continents. The age of the rocks on both sides of the Atlantic suggests that these continents were once one whole. Thanks to plate tectonics, it has become possible to reconstruct ancient pages of the Earth's history and the positions of continents in the past.
Ancient continent Pangea ( )
In the history of the development of the Earth, scientists distinguish 4 major stages. Each of them ended with the formation of a supercontinent washed by the waters of one ocean.
The first such continent - MONOGEA - included the entire continental crust and arose about 2.5 billion years ago. The second - METAGEA - about 1.8 billion years ago. The third - MESOGEA - about 1 billion years ago. The last one was about 200 million years ago. Scientists called it Pangea (“universal Earth”) (see Fig. 4). Millions of years later, this ancient continent in the ancient Ocean split first into two parts - Laurasia (northern continent) and Gondwana (southern continent), and then into several more parts. This is how modern continents were formed.
Rice. 4. Pangea
The set of irregularities on the earth's surface, varying in size, origin and age, is called relief ().
The main reason for diversity relief of the earth- interaction of internal (endogenous) and external (exogenous) forces of the Earth.
Domestic forces are manifested in the processes of movement of the lithosphere, the introduction of mantle matter into Earth's crust and pouring it out onto the surface.
There are slow vertical movements and horizontal movements, the most significant of which are the movements of lithospheric plates. As a result of their movement, the largest landforms of the Earth are formed - continental ridges and ocean basins, mountain belts, and huge plains.
External forces act on the surface of the Earth. External forces are weathering, the work of flowing waters, wind, groundwater, glaciers, sea surf and human activities.
These forces destroy rocks and carry destruction products from one area of the earth's surface to others, where they are deposited and accumulated.
The role of weathering (mechanical and chemical) is especially important in the destruction and leveling of relief on land.
Internal and external forces act simultaneously. At the same time internal forces They mainly create large relief forms, while external ones mainly destroy them.
The creative power of external processes is manifested in the formation of small-sized relief forms. On the plains there are hills, river valleys, ravines, in the mountains there are screes, gorges, rocks of bizarre shapes.
Relief changes on Earth occur continuously. The outlines of the mountains are changing, the hills are leveling out, and even, albeit very slowly, the outlines of the continents are changing.
Homework
Read §. Execute practical work: "Earth's lithosphere".
Experimental work: “Modeling the position of continents in ancient times, at present, in the future”
In his book “The Origin of Continents and Oceans,” German geophysicist A. Wegener wrote: “In 1910, the idea of moving continents first occurred to me (...), when, while studying a map of the world, I was struck by the similarities in the outlines of the coasts on both sides of the Atlantic Ocean.” .
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Purpose of the study: |
To verify the correctness of the assumptions of the German geophysicist A. Wegener about the origin of continents and oceans, that is, to confirm the hypothesis of continental drift. |
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What is needed for this? |
scissors, glue (glue stick or PVA glue), blank sheet of paper (A4 format), old geographical map of the world (you can use contour map peace) |
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Progress of the experiment: |
It is necessary to cut out the contours of the continents using an old geographical map peace. On clean slate paper (A4 format), connect (but do not glue yet) the contours of the continents so that you get: ancient continents: Laurasia and Gondwana (model A); then connect the resulting ancient continents in such a way that you get the ancient single continent of Pangea (model B). Follow the “course” of continental drift: · in ancient times: the split of Pangea into Laurasia and Gondwana (that is, from model B you get model A); · currently (model B), · in the future (model D). Answer the questions. |
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Experiment result (conclusion): |
Give answers to the questions: The ancient giant continent is called... The ancient huge ocean is called... As a result of the Laurasia fault,... As a result of the Gondwana Fault,... The name Pangea comes from... The name Tethys is associated with... The hypothesis of continental drift was outlined by A. Wegener in 1915 in the book... |
References
MainI
1. Geography. Land and people. 7th grade: Textbook for general education. uch. / A.P. Kuznetsov, L.E. Savelyeva, V.P. Dronov, series “Spheres”. - M.: Education, 2011.
2. Geography. Land and people. 7th grade: atlas. Series "Spheres".
Additional
1. N.A. Maksimov. Behind the pages of a geography textbook. - M.: Enlightenment.
Literature for preparing for the State Exam and the Unified State Exam
1. Tests. Geography. 6-10 grades: Educational and methodological manual/ A.A. Letyagin. - M.: LLC "Agency "KRPA "Olympus": Astrel, AST, 2001. - 284 p.
2. Tutorial in geography. Tests and practical assignments in geography / I. A. Rodionova. - M.: Moscow Lyceum, 1996. - 48 p.
3. Geography. Answers to questions. Oral examination, theory and practice / V. P. Bondarev. - M.: Publishing house "Exam", 2003. - 160 p.
4. Thematic tests to prepare for the final certification and the Unified State Exam. Geography. - M.: Balass, ed. House of RAO, 2005. - 160 p.
1. Russian Geographical Society ().
3. Textbook on geography ().