The formation of the Loess Plateau in our country has gone through approximately

In the north of our country, there is a loess plateau with an area of about 600,000 square kilometers, which is famous for its huge area, rugged terrain and deep loess.

How did the Loess Plateau form?

For more than 100 years, many scientists have devoted themselves to the study of this problem and put forward dozens of hypotheses: some believe that the "hometown" of loess is not local, and that the loess is carried to the Loess Plateau by wind (called the loess wind theory); Some believe that the flowing water carries the loess to the Loess Plateau (called the Loess Hydrogenic Theory); Some people believe that the "hometown" of loess is in the local area, and it is weathering that "crushes" the original rocks and gravel, and then the remnants evolve into loess in situ (called the theory of weathering residue), and so on.

In the past two or three decades, more scientists have agreed with the theory of loess aeoliation. Because after research, scientists have found that the farther away from the deserts in Mongolia, Central Asia and northwest China, the finer the particles of loess; From northwest to southeast, the distribution pattern of Gobi, desert, sand loess, loess and clay loess is present, and the mineral composition of each zone is completely consistent with the mineral composition of sand and gravel in desert areas, but it is very different from the local rock composition. The loess is inselectively covered on the mountains of the Loess Plateau, and its thickness gradually thins from northwest to southeast. Fossils of terrestrial animals and plants of the arid steppe type have also been found in the loess.

According to the explanation of the theory of loess wind, the Loess Plateau is formed in this way: in the desert areas of Mongolia, Central Asia and northwest China, the climate is dry, the temperature difference is very large, due to the effect of thermal expansion and cold contraction, the rocks, gravel, etc. are "processed and crushed" into fine sand and dust. A strong northwesterly wind will whirl millions of tons of fine sand and dust into the sky and move south with the wind.

As a result, the coarse-grained ones settled down first to form a desert, while the fine-grained ones were drifted to the northern foot of the Qinling Mountains. After two or three million years of transportation and accumulation, the Loess Plateau was finally formed.

Science is constantly evolving, and in recent years scientists have discovered many phenomena that cannot be explained by the loess aeolian theory. For example, the content of coarse silt in loess decreases from northwest to southeast, while the content of clay increases from northwest to southeast. This shingle-like distribution transition is more like a masterpiece of the flood and so on.

In this regard, Chinese scientist Li Mingguang put forward a new theory -- the theory of catastrophe water formation on the Loess Plateau. He used a large amount of evidence to confirm that the Loess Plateau was formed by flooding, loess sedimentation and neotectonic uplift brought about by Himalayan movements. His views have attracted attention.

The formation of the Loess Plateau in China has taken about one million years.

The formation process of the Huangsun Fantu Plateau is briefly described as follows:

1. The ground wind rolls up the particulate matter from the Gobi Desert area, and some of the imitation particles are directly transported by the ground wind, and the other part is blown up to the sky and transported by the westerly rapids.

2. In the area of the present-day Huangshi Plateau, dust began to fall due to the weakening of the wind and the barrier of the mountains, and finally accumulated to form the Loess Plateau.

3. The rainfall brought by the southeast monsoon has eroded the loess, resulting in the scene of dry ravines and ravines in some areas of the Loess Plateau today.

The shape of the plateau on the Loess Plateau is related to the original topography under the loess. If the dust falls on the flat high ground, the dust will accumulate on the flat top surface, and the soil layer will gradually thicken, and eventually form a loess plateau, if the original ground is not a flat high ground, but a gentle hill, the dust will accumulate on the top surface to a certain extent.

The dust on the slope will roll freely into the edge valley, and it will not be able to form a flat Huangyi Plateau, and eventually only the Yellow Ten Beams and Ridges can be formed. When the yellow ten falls on some rocky mountains, the loess will fill the depression with a small thickness, and the tips of the mountains will protrude from the loess in the form of small islands.

Introduction to the Loess Plateau

The Loess Plateau is located in the north-central part of China and is one of the four major plateaus in China. In a broad sense, the Loess Plateau is the loess area, with a loess area of 10,000 square kilometers, including 10,000 square kilometers of primary loess and 10,000 square kilometers of secondary loess, which is mainly composed of Shanxi Plateau, Shaanxi-Gansu-Jin Plateau, Longzhong Plateau, Ordos Plateau and Hetao Plain.

In a narrow sense, the Loess Plateau roughly stretches from the Great Wall in the north, to the Qinling Mountains in the south, to the Wusheling Mountains in the west, and to the Taihang Mountains in the east, including most of Shanxi, central and northern Shaanxi, central and eastern Gansu, southern Ningxia and eastern Qinghai, with an area of about 300,000 square kilometers.