§ 24. Plains
1. Remember, like a map denoting the plains.
2. What are the common forms of relief in your community?
Surface plains.On our planet dominated by flat terrain. It is well visible at physical map hemispheres.
Plains are flat. Their surface level, there are no notable rises and descents. There hilly plainsWhere alternating with a lower increase. But such disparities are high relative to 200 m. Thus, plain - A relatively level area Earth's surface with small fluctuations heights. Most of the plains of the world huge in size. This is reflected in their names: Great Plain of ChinaEurasia Great Plains in North America. At one Eastern European plain fit the territory of many countries - Ukraine, Belarus, Moldova, Lithuania, Latvia, Estonia and Russia (West).
Height plains.By height above sea level among distinguish low plains (lowlands), elevated (height) and high (Plateau).
Lowlands have absolute height to 200 m. For example, West-Siberian plain with flat surface in Eurasia. At the Earth's surface is the lowlands, which are even below the level Sea. For example, Pre-Caspian Sea lowland lies 28 m below sea level.
Highlands - It is plain from heights from 200 to 500 m. The hills include, for example Podolskin Ukraine.
Plateau - It is also plain, just high enough - over 500 meters above sea level. Examples are Serednosybirske plateau and plateau Dean in Asia.
Flat Ukraine establishes relief duty lowlands and highlands. With physical map easily identify where they are: yellowish color elevations Features among the green, which indicates the lowlands. Yes Dnieper heightlocated in western and Black Sea Lowland lies south. However, in nature it is difficult to notice the transition from one type to the Plains more. If you go, for example, from Odessa to the winery, the area will gradually increase and a traveler invisible to continue its path is not Lowland and Upland. Change in absolute height can be set only by using special equipment.
Formation plains.Plains can be formed as a result of lifting and removal of sea water bottom. This occurs during the vertical movement of the crust. These plain called primary. For example, Black Sea lowlandFarmland was once the bottom of the Black Sea.
Secondary plain formed differently. Some of them, created river sediments (sand, loam), which accumulated in a long time decrease in the crust. Their surface is flat or undulating. Yes Mesopotamian marshes formed by sediments of the rivers Euphrates and Tiger. The plains may occur in place of mountains, when under the influence of external processes destroyed their peaks and slopes and valleys filled with rubble. Then the mountain place gradually and leveled into a hilly plain. An example is Kazakh dribnosopkovyk- High plain, where the tower remains of some mountain ranges. In Ukraine is so plain Donets Ridge.
Plains usually coated thickness of sedimentary rocks: sand, clay, lesamy, gravel, limestone. Lie deep beneath magmatic and metamorphic rocks: granites and gneiss. In some places they come to the surface. Layers of sedimentary rocks lying horizontally or with a slight incline. Determine which way inclined plain and on the ground, and can map the direction of flow of rivers.
Change surface of the plains.Plain is affected by internal and external processes. Plains, as usually lie on the platform - the old stable areas aligned lithospheric plates. Therefore, internal processes, there appear to be mainly in the slow vertical movements.
External processes related to the work of water and wind. Where there is enough fluid water formed river valleys, ravines. Yara destroy the area's fertile lands. To combat people impose on them bushes and trees. In the desert, where dry, the surface of the plains changes due to weathering and the action of wind, creating a sand ridge, dunes and dunes. Today was a great external force and economic activity rights. During construction of the bridge, laying paths gully fall asleep, make embankments. During mining operations have careers and near mines growing mounds of waste - piles. Unfortunately, often converting natural person has a negative surface consequences. Nedbal economic activity can lead to dense network of ravines, the conversion of fertile land on the heath.
Questions and Tasks
1. What is called the plains? What surface can be plain?
2. As distinguished by high plains?
3. For the scale heights in the atlas defining what colors mark each type of plains in height. Give examples of each type of plains.
4. What is plain in Ukraine?
5. Ukraine Dnipro divides into right and left bank. With physical map of Ukraine determine which one is higher.
6. As plains formed?
7. Under the action of processes which may change the surface of the plains?
8. Consider where tilted Dnieper Upland, which in Ukraine. As you know learned?