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Shoreline lakes--Lagoons
This type of lakes, generally called lagoons, is created at inner bays when the sands deposited cut the bay from the sea at the mouth. For instance, Dongqian Lake in Ningbo and West Lake in Hangzhou.
The forming process of a type of tectonic lakes-the rift lake is:
- the line of demarcation between the ocean and land is called coastline, which undertakes the influence and erosion of waves and is in a constant change.
- the coastline turns into crooked from being straight. The bay forms and on both sides of its mouth is made up of the narrow and long sand.
- the narrow and long sand spits are nearing each other, and the bay loses the connection with the sea gradually, and finally forms a lagoon.
 About thousands of years ago, West Lake was still a shallow bay linked with Qiantang River in Hangzhou. Afterwards, because the silt carried by the tide and river was constantly deposited near the bay mouth, which eventually separated the bay from the sea, and the seawater within the secluded bay gradually desalinated and formed today's West Lake.
West Lake is called Jinniu Lake or Mingsheng Lake in the ancient time, also named Qiantang Lake or Xizi Lake, because the lake is located in the famous western suburb of Hangzhou.
West Lake is developed from the lagoon, and has entered the marsh stage for many times, forming the present scene after many times of dredging by the past working people. Su Dyke, Bai Dyke and Zhaogong Dyke divide the lake into Wai Lake, Beili Lake, Xili Lake, Yue Lake and Xiaonan Lake. Su Shi, a great writer in the Northern Song Dynasty, compared the lake to Xishi, the ancient beauty in Yue Kingdom, and it becomes famous both at home and abroad.
Some scholars believe that Taihu Lake and the surrounding lake groups are also lagoons in the ancient time. Probably 6000 years ago, the high sea surface once reached the foot of mountains to the west of the present Taihu Plain. Afterwards, because of the silt deposit of the Yangtze River, currents, waves and resultant wind direction, the sand spits on the south bank of the Yangtze River and the north bank of the Hangzhou Gulf joined together in a pincer shape. Therefore, the ancient Taihu Lake was enclosed (lagoon). The area of ancient Taihu Lake is far larger than that of present time. Nowadays Taohu-Gehu lake group, Dian-Mao lake group as well as the reclaimed Furong lake group and Linghu Lake group all belong to ancient range of Taihu Lake.
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