How was Chongming Island in Shanghai formed?

It belongs to the accumulation of water, mainly because of the slow accumulation of sediment in the Yangtze River. Specifically, Chongming Island is a product of the development of the New Yangtze River Delta, and its original place is the shallow sea outside the Yangtze River estuary. When the Yangtze River rushes down to the east and flows into the estuary area, a large amount of sediment is gradually deposited here due to the decrease of specific gradient and the slowdown of flow velocity.

On the one hand, coastal plains are formed on the north and south banks of the Yangtze River estuary, and on the other hand, scattered estuarine sandbars are formed in the river. In this way, Chongming Island has gradually become a typical estuary sand island. It has experienced ups and downs for more than a thousand years from emerging from the water to finally forming a big island.

Chongming Island is formed because of its unique geographical location. Because it is located at the mouth of the Yangtze River, the Yangtze River flows eastward, and when it flows into the estuary, the velocity slows down, resulting in a large amount of sediment carried from the upstream depositing here, which gradually forms an estuary sand island over time. Chongming Island has experienced more than a thousand years of ups and downs from its emergence to the formation of a big island, which is linked with the evolution of the Yangtze River estuary.

Because the Yangtze River estuary extends to the southeast, and Koumensha Island tends to lean northward, the position and shape of Chongming Island in the past are also very different from the present.

according to research, in the Tang dynasty about 1 years ago, the Yangtze estuary was still in the present-day Yangzhou-Zhenjiang area. At that time, the Mensha Island in the Yangtze estuary was only two small sandbars in the river, called Dongsha and Xisha, with a very small area of only tens of square kilometers.

The ancestors of the island moved from Danyang, Jurong and other nearby places in Jiangsu to make a living by fishing. It was not until the first year of Shenlong in the Tang Dynasty, that is, AD 75, that Chongming Town was established in Xisha.

Since then, Chongming Island has been moving down the river, rising up and falling down. In the Song Dynasty, Yao Liusha and Sansha piled up in the northwest and northeast of Xisha were produced, while the original Dongsha and Xisha were gradually washed away by collapse.

Next, the fate of Sansha, like Dongsha and Xisha, was gradually uplifted, and the old ones went to the new ones.

Majiabang, Pingyangsha, Changsha and other sandbanks were formed under it, among which Changsha is the predecessor of the current Chongming Island. In the long river of history, many sand islands were pushed northward or disappeared in the process of being washed down. However, < P > Chongming Island is at its peak today. However, Chongming Island is also unstable, and even its < P > county has moved again and again. In 1583, the 11th year of Wanli in the Ming Dynasty, there had been

five major migrations in Chongming County. It was not until 1875-198, the Guangxu period of the Qing Dynasty, that the south bank of Changsha quickly silted up. It was only after the local people built Shitang dam that the silting up momentum was stopped and the county town was < P > maintained and stabilized.