Lake Tai, or Tai Lake or Lake Taihu, is a large lake in the Yangtze Delta plain, on the border of the Jiangsu and Zhejiang provinces Eastern China. The waters of the lake belong to the former in its entirety with part of its southern shore forming the boundary between the two provinces. With an area of 2,250 km² and an average depth of 2 metres, it is the third largest freshwater lake in China, after Poyang and Dongting Lakes. The lake houses about 90 islands, ranging in size from a few square meters to several square miles.
Lake Tai is linked to the renowned Grand Canal and is the origin of a number of rivers, including Suzhou Creek. In recent years, Lake Tai has been plagued by pollution as a result of rapid economic growth in the surrounding region.
Scientific studies suggest that Lake Tai's circular structure is the result of a meteor impact based on the discovery of shatter cones, shock metamorphosed quartz, microtektites, and shock metamorphic unloading fractures. Recent science has dated the possible impact crater to be greater than 70 million years old and possibly from the Late Devonian Period. Fossils indicate that Lake Tai was dry land until the ingression of the East China Sea during the Holocene epoch. The growing deltas of the Yangtze and Qiantang rivers eventually sealed off Lake Tai from the sea, and the influx of fresh water from rivers and rains turned Lake Tai into a freshwater lake.