plain
The area with relatively low altitude on plain land is called plain. Refers to the vast and flat land. Its main characteristics are low and flat terrain, gentle fluctuation, relative height less than 55 meters and slope below 5. It is different from the lower plateau and the less undulating hills. The plain is the flattest area on the land, generally below 200 meters above sea level. Plain landform is broad and flat with little fluctuation, which is different from hills with little fluctuation and plateau with little height.
The cause of the plain: rivers will carry a certain amount of sediment in the process of flowing. When the river enters the sea, due to the slow flow rate, the sediment will be deposited and accumulated over time, forming a plain.
Hills and hills are generally more than 250 meters and less than 550 meters, and the relative height is generally not more than 2 10 meters. They are wavy with gentle slopes and consist of continuous low hills.
Causes: weathering of small mountains, sliding and sinking of unstable slopes, accumulation caused by wind, accumulation caused by glaciers, accumulation caused by vegetation, erosion caused by rivers, volcanoes and earthquakes, prehistoric meteorites, man-made, such as accumulation caused by open-pit mining, accumulation caused by ancient settlements, etc. In addition, hilly areas, such as golf courses, are deliberately caused by landscape technology, with absolute height less than 500 meters and relative height less than 20 meters.
Mountainous areas belong to the geological category, and the surface morphology is defined as more than 500 meters above sea level and relative height difference of more than 200 meters according to the characteristics of altitude and fluctuation.
Origin of mountain: According to the origin of mountain, it can be divided into fold mountain, fault mountain, fold-fault mountain, volcano and erosion mountain. The folded mountain is formed by the strata in the earth's crust being squeezed by horizontal force and bent upward into an arch. The fault mountain is formed by the vertical force on the rock stratum, which breaks the rock stratum and then is lifted. Himalayan Mountain is a typical folded mountain, Lushan Mountain in Jiangxi Province is a fault mountain, and Tianshan Mountain belongs to a folded fault mountain.
upland
The plateau is generally above 1000 meters above sea level, with a vast territory and open terrain, surrounded by obvious steep slopes. A relatively complete large uplift area is called plateau. The main difference between the plateau and the plain is the high altitude, and the difference between the plateau and the mountain area is a complete large-scale uplift.
The origin of the plateau: the plateau is known as the "stage of the earth" and was formed in the long-term and sustained large-scale crustal uplift movement. It has a great height difference from the plain, and has a great flat land and small ups and downs from the mountainous area. Some plateaus have broad and flat surfaces with little fluctuation; Some high-principle mountains fluctuate greatly and the terrain changes greatly.
basin
As the name implies, a basin is like a great basin on the ground, so people call it a basin with high surroundings (mountains or plateaus) and low middle (plains or hills). The largest basin on earth is in the middle of East Africa, called Congo Basin or Zaire Basin, with an area of about 1/3 of Canada. This is an important agricultural area in Africa, and there are rich mineral resources on the edge of the basin.
Genesis of the basin: The basin is mainly formed by crustal movement. Under the action of crustal movement, underground strata are squeezed or stretched.
Stretching, bending or fracture will cause some parts of the rock to rise and some parts to fall. If the descending part is surrounded by the ascending part, the prototype of the basin is formed.