What was the climax of the first great migration in ancient China?

Debate on the Yellow River water control and migration has existed since ancient times. The research on the history of Yellow River water conservancy shows that the fifth year of King Ding Zhou (602 BC) was the first major diversion of the Yellow River with accurate historical records, which created the famous Gong Yuhe. Then, after years of dike construction and management, the Yellow River became increasingly stable until the Eastern Han Dynasty. During the Northern Song Dynasty, the Yellow River flood occurred again on a large scale, and the river course changed dramatically, with more floods, overflows and immigrants than before. At this time, the most intense dispute between the East and the West occurred in history. Both Sima Guang and Wang Anshi were involved in the dispute over the general plan of river management, which eventually ended in adapting to the new tectonic activity of "flowing high in the east and flowing smoothly in the north", which actually led to a correct understanding of the laws of nature.

Since modern times, the research on the lower reaches of the Yellow River has entered a scientific track. The discussion on the basic causes of migration and diversion in the lower Yellow River can be summarized as sediment deposition and basement tectonic activity. Not long ago, Mr. Ren Meihua quoted Liang, an American Chinese, as saying that the evolution of the northbound channel in the lower reaches of the Yellow River was related to prehistoric earthquake disasters, and a strong earthquake in ancient times prompted the Yellow River to divert its course northwards. This statement links major disasters with the evolution of paleogeographic environment, provides a new way of thinking, and can be said to be a new explanation of the reasons for migration and diversion in the lower Yellow River. However, after in-depth study of the problems related to earthquake structures and prehistoric disasters in the North China Plain, it is found that the problems may not be so simple.

The evolution of regional rivers is controlled by basement active structures and has a clear understanding in geology. After studying the ancient rivers on the surface of North China Plain, Chen Wu and others pointed out that "Zhanghe River, Hutuo River and Tanghe River even include the ancient Yellow River Road. After flowing out from the alluvial fan to form a plain, it does not directly flow eastward into the sea, but flows northeast for a certain distance before it flows eastward into the sea. This is obviously affected by the active structure of the basement. At the same time, the study of geological tectonic movement in North China Plain reveals that the general movement of the plain tends to tilt northward and eastward, that is to say, the direction of northward flow should be towards the central Bohai Sea, the settlement center of Quaternary in North China. Repeated strong earthquakes along the tectonic belt (especially the seismic tectonic belt in the middle of North China Plain) may affect the evolution trend of the Yellow River, but it is impossible for strong earthquakes to form a northbound valley large enough to accommodate the Yellow River, which has been confirmed by earthquake research.

When studying the evolution law of the north channel in the lower reaches of the Yellow River, the first problem found is that the north channel of the Yellow River has never reached the west of the plain and entered the Baiyangdian basin in history. Many routes of Beiliu only reach the edge of this area, then turn northeast, cross the corridor of Cangzhou, Texas, and enter the vicinity of Haihe River. This is a question that has always been confusing. The research results of earthquake geology have confirmed that the piedmont of Taihang Mountain and the central and western plains do not have the geological and structural conditions for the occurrence of catastrophic earthquakes, and the northward movement of the Yellow River has never reached this area including Baiyangdian Basin. So, what happened in this area?

Recently, it was discovered that there was a huge meteorite shower impact in the middle of Hebei Plain and Baiyangdian Valley in prehistoric times. Through in-depth study, it is found that this major disaster is one of the main factors that caused the basic pattern of the north flow of the Yellow River in history.

In recent years, when studying the historical landform of Baiyangdian basin, it is found that there is a special geomorphologic panwa group in this area. This peculiar and widely distributed landform in Baiyangdian River Basin is the remains of meteorite shower impact crater on Quaternary loose sediments in the middle and late Holocene. Combined with relevant data, it is speculated that the special landform of Baiyangdian River Basin was formed by surface water and artificial transformation after a huge meteorite shower impact in the middle and late Holocene. The preliminary study proves that the area where this astronomical geological disaster occurred may extend from the northern part of Shanxi to the central part of Hebei, and even to the vicinity of Bohai Bay. The time of occurrence is estimated to be 4000-5000 years ago. A large part of meteorite shower splashed down in the central and western Hebei Plain, forming a large number of impact craters on loose sediments in the plain, which were distributed in groups on the surface of the plain. After the erosion and transformation of surface water, a special Baiyangdian basin has been formed in the central and western parts of Hebei Plain. The lip of the impact pit is intertwined with the annular deposits formed by the surrounding projectiles, and the uplift forms a multi-stage natural annular dam, which not only blocks the huge impact of the northward flow of the Yellow River, but also limits the outflow of surface water in the impact area. On the other hand, the impact destroyed the surface rivers (probably including the Yellow River) and blocked the channels of the Yellow River and other rivers into the sea, thus causing prehistoric floods. In this way, a series of problems that were difficult to explain in the past, such as "the unique existence of Baiyangdian small watershed" and "the northward flow of the Yellow River ended in the south of Baiyangdian watershed in history", have been successfully explained. It is confirmed that the shell dike developed on the west coast of Bohai Bay is the geological evidence for the diversion and southward migration of the Yellow River. Only when the Yellow River does not flow into the Bohai Sea can a shell dike be formed. The oldest fourth shell dike in Bohai Bay was formed 4700-4000 years ago, that is to say, during this period, the Yellow River diverted to the south and then began to flow back to the north. As the shell dike with a certain scale and an older age has not been found in Bohai Bay, it can be further inferred that before the Middle Holocene (geological age of 1 10,000 years ago), although there was a small-scale diversion, the Yellow River mainly flowed northward and entered the Bohai Sea. This is the relatively fixed flow direction of the ancient Yellow River, and the time when the Yellow River moved south for the first time can be presumed to be about 4,700 years ago. We can briefly summarize the evolution history of the migration and diversion of the Yellow River as follows: after the river was formed on the North China Plain, the direction of the Yellow River was influenced by the basement active structure, and basically maintained the northeast-northeast direction and merged into the Bohai Sea. Although sediments are easy to flood, before the middle and late Holocene, the northward river activity on the plain was stable as a whole; Sometime between 4,000 and 5,000 years ago, a huge meteorite shower collision occurred in North China, and a huge collision occurred in the central and western parts of the plain, which destroyed the passage of the northward flow of the Yellow River, caused the blockage of the passage, and possibly cut off the estuary. Since then, Hebei Plain has been flooded, and the lower reaches of the Yellow River have entered a period of extreme instability. Ancient ancestors began an important period of fighting floods. The Yellow River no longer enters the central and western parts of the plain, extends downstream to the central part of Hebei, then turns east, then passes through the narrow corridor of Cangzhou-Dezhou to the north, and finally enters the Bohai Sea.