Detailed knowledge of plateau geography

The altitude is generally above 1000 meters, 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 plateau is called "the stage of the earth", which was formed in the long-term and sustained large-scale crustal uplift movement. Some plateaus have broad and flat surfaces with little fluctuation; Some high-principle mountains fluctuate greatly and the terrain changes greatly. The highest plateau in the world is the Qinghai-Tibet Plateau in China, and the largest plateau is the Antarctic ice and snow plateau. The most essential feature of the plateau is its low terrain and high altitude. Plateau is widely distributed, plus closed basins, accounting for about 45% of the earth's land area.

There are four plateaus in China, which are concentrated in the first and second terraces. The Qinghai-Tibet Plateau is high-lying, with an average elevation of more than 4,000 meters, and there are many snow-capped mountains and glaciers. Inner Mongolia Plateau is a part of Mongolian Plateau, with an altitude of1000 m ~1400 m. The Loess Plateau is a world-famous plateau covered by loess in a large area. It inclines from northwest to southeast, with an altitude of 800-2,500m, criss-crossing gullies, scarce vegetation and serious soil erosion, which is rare in the world. Yunnan-Guizhou Plateau is rugged, with an altitude of 1000m ~ 2000m, numerous canyons and typical karst landforms.

According to the shape of the plateau surface, the plateau can be divided into several types: one is a plateau with a flat top, such as the Inner Mongolia Plateau in China; One is the ground.

Plateau with large ups and downs and wide top surface, such as Qinghai-Tibet Plateau in China; One is to divide plateaus, such as Yunnan-Guizhou Plateau in China, where flowing water cuts deeply, fluctuates greatly, and the top surface is still very wide. The Loess Plateau is one of the four plateaus in China, and most of the plateaus are covered with thick loess. Shaanxi Loess Plateau is the most typical area of loess physical geography in China, with complete strata and diverse landforms.

Inner Mongolian Plateau

Different types of plateau reflect the origin of plateau and its subsequent erosion history. The most common is the tectonic plateau. Most of Africa is such a raised continental block, and so is the Deccan Plateau in Arabian Peninsula and Indian subcontinent. The much smaller plateau has fault blocks and horsts, and it is a plateau that rises along the marginal fault system, or the part that is still high when the adjacent fault blocks settle. Horizons are usually easier to distinguish than large fault blocks. Inclined fault block is a variant, such a plateau has steep edges and gently inclined ground.

The plateau enclosed in the mountain system is called mountain plateau. In the United States, this type of landform is distributed between the Sierra Nevada and the Rocky Mountains, and is usually represented by the terms "basin" and "mountain range". However, the distribution of basins and mountains is worldwide. It includes most of Central Asia, Tibet, a part of Sichuan and Mongolia. Anatolia, Armenia and Iran are all composed of mountain plateaus, and some authors even extend to include the Mediterranean Sea, Aegean Sea and Black Sea in the category of mountain basins. Alpine plateau is also common in the Andes; Lake titicaca, the world's highest navigable body of water, is located on such a plateau with an altitude of 38 10 meters (12,500 feet). Intermountain plateaus, horsts and fault blocks are usually associated with young folded mountains.

Other types of plateaus are made of hard rocks. The volcano spewed out a large area of basalt lava flow, forming many plateaus. For example, the antrim Basalt Plateau in Northern Ireland, the Columbia-Shehe River Basin in the northwest of the United States, and the Deccan Plateau in the northwest of Ethiopia and India.

Plateau is characterized by high altitude, low air pressure and low oxygen content. Using this low-pressure hypoxia environment can improve the physical endurance quality of human body, so it becomes a "treasure land" for endurance training in sports. 1968 The 9th/kloc-0 Olympic Games was held in the plateau city of Mexico City. Athletes from the African Plateau include five middle-distance running and marathon champions, five runners-up and two runners-up. Since then, the plateau has become the endurance of long-distance running, marathon and race walking in sports circles all over the world.

Sichuan-Tibet Plateau

The training of this project is a "treasure land".

In addition, the plateau area receives more solar radiation, long sunshine time and abundant solar energy resources. The boiling point of water in plateau area is lower than 100℃. If you cook with an ordinary rice cooker, it will be unfamiliar.

Small height difference is the difference between plateau and mountain range, although it can also be produced. However, the plateau area is easily eroded by rivers and glaciers.

Albania

And cutting. After the ancient wrinkled mountain system was eroded, it rose to become a plateau, and then it began to suffer erosion again. For example, Adin in Belgium, Fjeld Plateau in Scandinavia and Allighan-Cumberland Plateau in Cheshire Mountains in Apara. Other places are cut more thoroughly, so there is almost no residue on the original plateau surface. This primitive surface is inferred from the consistent peak height, so whether there is such an erosion surface has caused controversy among geomorphologists. The Highlands of Scotland is such an area. It has always been assumed that there are primitive erosion surfaces, but whether there are several surfaces is often debated. In addition to questioning the selected erosion surface, the uplift area may have experienced severe warping, so we can't be sure that it is the result of a previous low-altitude plain uplift. [ 1]

In arid and arid areas, cutting often leads to the formation of flat strata, especially in the case of solid cover. This is a typical frontier landscape in the southwestern United States. The original ground has been eroded into terraces and battlements (smaller Pingdingshan). Because of the high terrain, the plateau often causes its unique local climate. In the topography of basins and mountains, the height and the rain shielding effect caused by surrounding mountains work together, resulting in arid and semi-arid environment.

The plateau formed in shorter years is generally flat, while the older ones look like mountains because of long-term weathering and erosion. The western end of the Appalachian Mountains in the eastern United States is actually a mountain-like plateau or platform.

Formation of Qinghai-Tibet Plateau

Qinghai-Tibet Plateau

The geological history of the Qinghai-Tibet Plateau with definite evidence can be traced back to the Ordovician period 400-500 million years ago. Since then, there have been different data of crustal rise and fall in different parts of the Qinghai-Tibet region, either submerged by seawater or on land. By 280 million years ago (early Permian in geological age), the Qinghai-Tibet Plateau was now a rough Wang Yang. This sea area spans the southern part of Eurasia and communicates with the waters of North Africa, South Europe, West Asia and Southeast Asia. It is called "Tethys Sea" or "Ancient Mediterranean". At that time, the Tethys Sea had a warm climate, which made it a prosperous area for marine animals and plants. Its north and south sides are divided primitive ancient land (also called Pangu land), and its south side is called Gondwana land, including South America, Africa, Australia, Antarctica and the South subcontinent. The northern continent is called Eurasia, also known as Lauea, including Europe, Asia and North America.

240 million years ago, due to plate movement, the separated Indian plate moved northward and squeezed at a relatively fast speed, and strong folds, faults and uplifts appeared in the north, which promoted the Kunlun Mountain and Hoh Xil area to grow into land. As the Indian plate continues to insert northward under the ancient ocean crust, it pushes the ocean crust to break continuously. About 265.438 billion years ago, the North Tethys Sea once again entered the tectonic active period, the North Qiangtang area and the Karakorum area. By 80 million years ago, the Indian plate continued to drift northward, causing strong tectonic movement again. The Gangdise Mountains and Nyainqentanglha Mountains have risen sharply, and parts of northern and southern Tibet have also left the sea and become land. The whole terrain is broad and gentle, with rivers and lakes, vast plains, humid climate and lush jungle. The landscape pattern of the plateau has basically taken shape. Geologically, this tectonic movement of plateau uplift is called Himalayan movement. The uplift process of the Qinghai-Tibet Plateau is not a uniform movement, not a one-time skyrocketing, but has gone through several different stages. Every uplift makes the plateau landform evolve. Ten thousand years ago, the plateau rose faster, with an average annual increase of 7 cm, becoming the "roof of the world" on the earth today.

The formation history of the Qinghai-Tibet Plateau can be roughly divided into nine development stages.

(1) Sinian: The Qinghai-Tibet Plateau is divided into two main parts: the ancient Gondwana continent and the Qilian Sea. The ancient Gondwana continent is in the west, namely Himalayas, Gangdise Mountain and Tanggula Mountain, and the Qilian Sea is in the east of the Qinghai-Tibet Plateau, namely Kunlun Mountain and Qilian Mountain.

(2) Cambrian to Ordovician: the ancient Gondwana continent sank, the Qilian Sea extended to it, and the original Tethys Ocean was greatly reduced;

(3) Ordovician to Silurian: the ancient Gondwana continent sank further, the Qilian Sea gradually disappeared, and the original Qilian Sea rose;

(4) Devonian to Permian: Gondwana, Middle Tethys and Eurasia appeared, and the central Qinghai-Tibet Plateau sank into the ocean again;

(5) Permian to Triassic: the central and eastern part of the former Qilian Sea rose to the mainland again, and the west sank to the deep sea, connecting with the shallow sea of Gondwana ancient land;

(6) Jurassic: the Middle Tethys Sea has been raised to land, and the ocean has expanded westward and northward, forming a new Tethys;

(7) Jurassic to Cretaceous: NeoTethys contracted, Lagugang Day rose first, and a small sea area was formed in the south;

(8) Cretaceous to Eogene: NeoTethys was completely closed and Eurasia was basically formed;

(9) Tertiary: Due to the fierce collision between Eurasian plates, large-scale volcanic and seismic activities were promoted, and the uplift of the Qinghai-Tibet Plateau was sharply intensified.

The Qinghai-Tibet Plateau is the highest plateau in the world, with an average elevation of over 4,000 meters. The Himalayan Mountains on its edge are as high as 8,848 meters, making it the highest mountain range in the world. However, the Qinghai-Tibet Plateau and the Himalayas were not that high at first. According to geologists, the Qinghai-Tibet Plateau and the Himalayas used to be a sea, and later the collision and uplift of continental plates became what they are today. In addition, the highest plateaus and mountains are still in the primary stage in geological history and will continue to increase.

Editing the Formation of this Loess Plateau After the Indian plate moved northward and collided with the Eurasian plate, the Indian continental crust was inserted under the Asian continental crust to prop up the latter. As a result, the shallow sea of the Himalayas disappeared, the Himalayas began to form and gradually lifted, and the Qinghai-Tibet Plateau was also squeezed and lifted by the Indian plate. After this process lasted more than 60 million years, by about 2.4 million years ago, the height of the Qinghai-Tibet Plateau had exceeded 2,000 meters.

The great change of surface morphology directly changed the pattern of atmospheric circulation. Before that, Chinese mainland was occupied by shallow seas to the east, Siberia to the north and Himalayas to the south, and the Mediterranean Sea to the west also extended to a far place in central Asia, so most of the flat Chinese mainland could get enough moist air from the ocean, and the climate was warm and humid. Northwest China and Central Asia are mostly subtropical areas, and there are no large areas of deserts and Gobi.

loess plateau

However, the east-west Himalayan mountains stopped the warm and humid air mass in the Indian Ocean from moving northward. With the passage of time, the northwest of China has become more and more arid, gradually forming a large area of desert and Gobi. This is the birthplace of dust on the Loess Plateau. The huge Qinghai-Tibet Plateau just stands in the westerly belt of the northern hemisphere, and its height has been increasing for 2.4 million years. The width of the Qinghai-Tibet Plateau accounts for about one third of the westerly belt, which divides the surface of the westerly belt into two branches. The south branch flows eastward along the south side of the Himalayas, and the north branch flows eastward from the northeast edge of the Qinghai-Tibet Plateau. This kind of high-altitude airflow exists at an altitude of 3500-7000 meters all the year round and becomes the main driving force for carrying dust. At the same time, due to the uplift of the Qinghai-Tibet Plateau, the East Asian monsoon has also been strengthened. The winter wind blowing from northwest to southeast, together with westerly jet, formed the Loess Plateau in the north of China.

In the desert and Gobi in the northwest of China and the inland of Central Asia, the rocks here disintegrate into pieces faster than other places because of the drastic change of temperature. Geologists divide it into gravel (more than 2 mm), sand (2-0.05 mm), silt (0.05-0.005 mm) and clay (less than 0.005 mm) according to its diameter. Clay and sediment particles can be carried to an altitude of more than 3,500m, enter the westerly belt, be transported to the southeast by westerly jet, and gradually fall until the middle and lower reaches of the Yellow River.

For two or three million years, the process of transporting sand from northwest to southeast in this part of Asia has never stopped. A lot of sand falls in the area where the Loess Plateau is located, and even many mountains in North China, such as Wutai Mountain and Taihang Mountain, have loess accumulation at the top. Of course, the scouring effect of several large rivers and countless valleys in northern China, including the Yellow River, is just the opposite of the accumulation of loess. Otherwise, the loess plateau will not be like this, and the thickness will not exceed 409.93 meters. The North China Plain east of Taihang Mountain is also a subsidence area of sand, but it is a subsidence area, and at the same time many rivers have developed, so the falling sand is either washed away by the rivers or buried by the sediment brought by the rivers.

There are hundreds of records about rain soil, rain loess, rain yellow sand and rain haze in China ancient books. The earliest record of "rainy soil" can be traced back to 1 150 BC: the sky is yellow and foggy, and sand falls from the sky like rain. What is recorded here is actually a sandstorm.

The location of rainy soil is mainly in the Loess Plateau and its vicinity. The ancients regarded this kind of thing as a strange catastrophe phenomenon and thought it was a sign of "harmony between man and nature" It is recorded in the Natural History compiled by Zhang Hua in the Jin Dynasty: "When Xia Jie was in the deep valley, the night palace was mixed with men and women, and he did not go out to listen to politics for ten days. It was a windy day and filled the empty valley overnight. "

During the period of 1966- 1999, there were 60 sandstorms lasting more than two days in China. Academician Liu Dongsheng of the Chinese Academy of Sciences thinks that the Loess Plateau should be regarded as a laboratory for sandstorms, which has accumulated records of sandstorms for millions of years. Sandstorms from the northwest desert and Gobi are scattered all over the sky, leaving a thin layer of loess on the Loess Plateau every year.

Development of the Loess Plateau The Loess Plateau and the Yellow River Basin were once the main settlements of the ancestors of the Chinese nation, the birthplace of ancient culture in China, and were once called the cradle of the Chinese nation. The cultures of the ancient Xia, Zhou and Qin dynasties all grew up here.

Today's Loess Plateau includes most or part of Shaanxi, Gansu, Ningxia, Shanxi, Henan, Qinghai and Inner Mongolia. There are more than 200 counties, with a total area of about 599,000 square kilometers, cultivated land area of 65.438+0.8 billion mu and a population of nearly 70 million. In this vast land, there are about 430,000 square kilometers of land with serious soil erosion.

Heavy, annual soil erosion per square kilometer, from thousands of tons to 1 10,000 tons. According to the survey, it is estimated that 0.5 cm of fertile soil is eroded from the ground every year. There are about 200 million mu of cultivated land in this area. Due to long-term soil erosion, the natural environment and production conditions have been seriously damaged, and agricultural production is backward. In some areas, the grain yield per mu is only 30-50 kg. 1In July, 977, a flood caused by a rainstorm of more than 150 mm poured down from the nearby highlands without hindrance, and once flooded more than half of Yan 'an City. It is estimated that the average annual erosion modulus of the Loess Plateau (the amount of sediment lost per unit area every year) is generally 5000 ~ 15000 tons/square kilometer, and even as high as 15000 ~ 30000 tons/square kilometer in some places in northwestern Shaanxi and northwestern Shanxi. The sediment flowing into the Yellow River every year reaches more than 654.38+0.6 billion tons. Due to soil erosion in the Loess Plateau, it not only seriously endangers agricultural production in northwest China, but also seriously threatens the safety of the Yellow River, causing the riverbed in the lower reaches of the Yellow River to continuously deposit and become a rare "suspended river" in the world. At present, the riverbed in the lower reaches of the Yellow River is 3-8 meters above the ground, and in some places it is as high as 12 meters, which is already higher than the Kaifeng city wall, seriously threatening the lives and property of people in the lower reaches.

The topography of the Loess Plateau can be divided into three parts.

(1) Central Gansu Plateau, west of Liupan Mountain, with an altitude of about 2000 meters. There are several narrow valley plains on the plateau, such as the Yellow River Valley near Lanzhou and the Taohe River Valley near Lintao, which are the richest places on the plateau. When we stroll on the Loess Plateau, you will also see rows of neat caves, which are the residences of some farmers on the Loess Plateau under the oil fields of wheat and millet.

(2) The northern Shaanxi Plateau is about 800 ~ 1000 meters above sea level, with low terrain, surrounded by high mountains and structurally a basin, so many geographers and geologists call it the northern Shaanxi Basin. There is Luliang Mountain in Shanxi across the Yellow River to the east of the northern Shaanxi Plateau. To the west is Liupanshan Mountain in Gansu, all of which are high mountains over 2000 meters. The elevation of the mountain between Tongchuan and Yijun in the south is only 1200 ~ 1500m. The northern part is connected with the Mu Us Desert, and there is no obvious boundary. However, Baiyu Mountain to the north of Jingbian is 2000 meters above sea level, which can be regarded as the northern boundary of the plateau. On the gentle ground of the northern Shaanxi Plateau, high Rocky Mountains sometimes stand at an altitude of about 1 100 ~ 1400 meters. Most strata in the northern Shaanxi Plateau are horizontal, and the erosion of rivers is particularly strong.

(3) Shanxi Plateau lies between Taihang Mountain and Luliang Mountain. There are many faults and local basins in Shanxi, and the terrain is more complicated than that in northern Shaanxi and Gansu Plateau. The eastern foot of Taihang Mountain is steep and slopes gently to the west, which actually constitutes a part of Shanxi Plateau. The eastern edge of Shanxi Plateau is more than 2000 meters above sea level, which gradually decreases to the west, so the ground elevation of the plateau is mostly between 1500 ~ 2000 meters. There are many local basins on this plateau at an altitude of about 1000m, such as Pingding, Qinxian and Changzhi. The shape of Luliang Mountain is similar to that of Taihang Mountain, with the highest peak above 2500 meters above sea level. The whole Shandong slope is steep and the west slope is gentle, and it is gradually connected with the northern Shaanxi Plateau. There is a long and narrow lowland between Luliang Mountain and Taihang Mountain in central Shanxi, with an altitude of 400 ~ 800 meters, extending from Taiyuan to the bank of the Yellow River in southwest Shanxi. Among them, the flat land near Taiyuan has the widest range, about 150 km long and about 50 km wide, which constitutes the largest local basin in Shanxi Plateau. The lowland is roughly parallel to Taihang Mountain and Luliang Mountain, and the Fenhe River flows into the Yellow River along this lowland, so this lowland is called Fenhe Lowland. Because there are obvious faults on both sides of the lowland, Fenhe lowland is indeed a typical graben in terms of geological structure.

Regional Classification of the Loess Plateau After the founding of New China, the state has done a lot of work on the management and development of the Loess Plateau, but there are some problems in production policies and management measures, which make the change of the Loess Plateau appear slow. On the basis of summing up the past experience and lessons, the relevant state departments initially put forward the policies that should be adopted in the future construction of the loess plateau in northwest China. For the hilly and gully areas that occupy a considerable area of the Loess Plateau and have the most serious soil erosion, priority should be given to the development of forestry and animal husbandry, and agriculture, forestry and animal husbandry should be comprehensively developed according to local conditions and comprehensively managed; According to different natural and socio-economic conditions, the Loess Plateau is divided into four different types of regions:

(1) Agricultural area, including Weibei, Longdong, Jinzhong and south of Yan 'an. It belongs to semi-humid and mild cold climate, with annual precipitation of 500 ~ 600 mm, annual average temperature above 10℃, many platforms and great production potential. These areas should mainly develop agriculture to make food self-sufficient, and some counties should build commodity grain, cotton and oil bases. It is necessary to actively build farmland shelterbelts and slope protection forests, appropriately plant pasture in the source areas and hilly gentle slopes, and develop animal husbandry.

(2) Forest and pastoral areas, including Longnan, Ningnan, Northwest Shanxi and hilly and gully areas north of Yan 'an. It belongs to forest grassland and its transition zone to grassland, with semi-dry and cold climate, annual precipitation of 400 ~ 500mm and serious soil erosion. The eastern part is very important to the sandstorm area and has been threatened by wind erosion; The cultivated land area is very large, and the vegetation has been seriously damaged; Agriculture is affected by topography and climate, and its output is low and unstable. This area should focus on planting trees and grass, develop forestry and animal husbandry, properly build basic farmland on the "Sichuan" platform and gentle slope, and strive for perennial food self-sufficiency.

(3) Pastoral areas, including central Gansu, southern Ningxia, northwestern Shanxi, northern Yulin and some places in northern Inner Mongolia. Belonging to grassland belt and desert grassland belt, the climate is semi-dry and cold, the annual precipitation is mostly below 400 mm, the winter is long and cold, the spring and summer are dry and windy, the sandy soil area is large, the wind erosion and water erosion are serious, the crop growth period is short, and there are many unfavorable conditions for developing agriculture. This area should mainly develop animal husbandry, vigorously build windbreaks and grazing forests, appropriately develop agriculture, and strive for basic self-sufficiency in food.

(4) Forest areas, including some counties near Ziwuling, Huanglong Mountain, Laoshan Mountain, Qiaoshan Mountain, Liupanshan Mountain and Longshan Mountain and some areas of Luliang Mountain. There is a lot of precipitation and high terrain here. Most of them are rocky mountains, and the soil layer is thin. Now there are some secondary forests left. This area should give priority to forests, strictly protect existing forest areas and actively develop water source forests to ensure the development of agriculture and animal husbandry in this area.

In short, the main crop in the plateau is highland barley, a kind of barley; Yak is a unique livestock in the Qinghai-Tibet Plateau, and ranks as the three main livestock in the alpine pastoral area of the Qinghai-Tibet Plateau along with Tibetan goats and sheep. According to the natural conditions, socio-economic conditions and the needs of agricultural modernization in different types of areas, the development zoning and implementation planning of agriculture, forestry and animal husbandry production should be formulated respectively in the Loess Plateau, focusing on soil and water conservation, combining soil improvement with water control, combining slope control with gully control, combining engineering measures with biological measures, actively building basic farmland, vigorously planting trees and grass, and focusing on contiguous management in small and medium-sized watersheds to speed up comprehensive management and rational development in the Loess Plateau. He and Gao Song co-authored the book Characters in Rock Paintings and History in Characters. He graduated from college and published poems and essays one after another. In 2003, he studied phonology, philology and hermeneutics of rock paintings with his father, Professor Gao Song, and participated in writing "Characters in Rock Paintings, History in Characters". A scholar from Ningxia and his daughter studied the plateau for four years and came to the conclusion that Helan Mountain is an ancient non-Zhoushan Mountain, that is, a sacred mountain worshipped by ancient China people.

The main plateaus in China and the world are: Loess Plateau, Inner Mongolia Plateau, Qinghai-Tibet Plateau and Yunnan-Guizhou Plateau.

The main plateaus in the world are: Antarctic Plateau, Brazil Plateau, Iran Plateau, Qinghai-Tibet Plateau, South Africa Plateau, Labrador Plateau, East Africa Plateau, Ethiopia Plateau, Mongolia Plateau, Arabia Plateau, Deccan Plateau, Central Siberia Plateau, Guyana Plateau and Patagonia Plateau.