Taihu Lake, with its water area resembling a Buddha's hand, serves as the central hub of the water network in southern Jiangsu. It is rich in resources and has nurtured the lives of people in its basin, earning the title of 'embracing Wu and Yue' since ancient times. Many poets and scholars have been enchanted by its beauty, leaving behind numerous famous verses. The picturesque scenery and abundant products of Taihu Lake, along with the intricate river networks of the nearby Yangtze River Delta, have long made it a land of fish and rice in China. Surrounded by towering peaks, Taihu produces renowned teas like Biluochun and Taihu red oranges, which were once tributes to the imperial court. The lake is also home to a variety of aquatic products, including the translucent and tender Taihu silver fish, a delicacy at banquets.
However, despite its stunning landscapes and vast grandeur, the origins of Taihu Lake remain a topic of debate to this day.
As early as the early 20th century, Chinese geographer Ding Wenjiang and foreign scholar Heidenshuhm suggested that the lake was formed due to sedimentation from the Yangtze River. They theorized that 5,000 years ago, Jiangyin was a coastline, and the areas east of Jiangyin, south of Rugao, and north of Haining, including the Taihu region, were all part of the Yangtze River's sedimentary zone.
By the 1930s, the discovery of lacustrine and marine sediments in the lake area led to a more mature and systematic understanding of Taihu's formation. Notable geographers like Zhu Kezhen and Wang Huzhen proposed the lagoon formation theory, which was later enriched with new content. In 1941, German researcher Feishengmeng suggested that the coastline during the 1st to 3rd centuries AD extended from Taicang, Jiading, to the vicinity of Wangpan Mountain in Hangzhou Bay. Subsequent carbon-14 dating of shell fragments at the Maqiao cultural site confirmed that the area was the ancient coastline around 6,000 years ago.
Professor Chen Jiyu and his team at East China Normal University further developed and refined the lagoon theory based on previous studies. They argued that the presence of marine sediments in the Taihu Plain indicates that the massive sediment brought by the Yangtze River gradually accumulated downstream, causing the Yangtze River Delta to extend towards the sea, forming a sandbar. This sandbar eventually encircled the northeastern shore of the ancient Taihu, connecting with the sandbar on the northern bank of the Qiantang River, thus enclosing the ancient Taihu as a lagoon. Over time, continuous sedimentation led to the lagoon becoming isolated from the sea, resulting in the formation of various lakes, with Taihu being the largest among them.
In recent years, ongoing research into the geology, geomorphology, hydrology, archaeology, and literature of the Taihu region, particularly the discovery of Neolithic sites dating back 5,000 to 6,000 years, has prompted many researchers to question aspects of the lagoon theory. They argue that while sea water eroded and deposited sediment during its encroachment onto ancient land, this process was not uniform across the entire ancient land, leading to localized lagoonal deposits that do not represent the whole. Thus, while the lagoon theory may explain the topography and geological features of the Taihu Plain, it fails to account for the presence of Neolithic sites and ancient biological fossils beneath the peat layer in the plain's interior, which also contradicts the distribution of Holocene terrestrial layers. Many suggest that much of the Taihu Plain was originally land, allowing ancient inhabitants to settle and thrive.
It is speculated that around 6,000 to 10,000 years ago, the Taihu area was a flat plain where people lived and resided. Due to its low elevation, water eventually accumulated to form a lake, submerging their belongings before they could evacuate.
As for the formation of this depression, it is believed to be related to tectonic movements. The Taihu region may have always been an area of continuous crustal subsidence, where the low terrain prevented water from draining away, naturally leading to the formation of a lake.
The 'plain submergence theory' has not gained widespread attention, yet another hypothesis has recently emerged. A group of young geologists has proposed a bold explanation for the formation of Taihu Lake.
They hypothesize that in ancient times, an enormous meteorite struck the earth exactly at the location of Taihu Lake, suggesting that the vast lake was created by the impact of this meteorite! They estimate that the force of this meteorite could have been equivalent to the energy released by several billion tons of explosives or 10 million atomic bombs detonating over Hiroshima.
The proponents of the 'meteorite impact' hypothesis have presented several lines of evidence:
First, the external outline of Taihu Lake shows a significant indentation in the northeastern part, with a severely fragmented shoreline, while the southwestern part protrudes outward with a smooth, uniform rock face, resembling the shape of craters left by meteorite impacts on some continents.
Second, researchers have observed a remarkable regularity in the fractures of the rock layers surrounding Taihu. In the northeastern part of the lake, many layers are pulled apart, while the fractures in the southwestern layers are primarily formed by compression. Such abnormal geological features would only occur under the influence of a massive impact from the northeast.
Third, researchers discovered a complex composition of angular clasts around Taihu. Under a microscope, these rocks exhibit signs of metamorphism caused by impact. Additionally, they found cosmic dust and molten glass nearby, which are materials typically produced by meteorite impacts.
Based on this evidence, they deduce that the meteorite came from a northeastern direction. The southwestern part of Taihu, being directly in line with the meteorite's trajectory, experienced the greatest impact force, resulting in radial fractures, while the northeastern part, under tensile stress, formed fractures perpendicular to the direction of impact. The immense force of the meteorite shattered the rocks, creating a mixture of angular rocks and impact metamorphic features.
Currently, there is no unified understanding of the causes of Taihu Lake, but all these differing viewpoints contribute to further investigation and research. As exploration continues, it is believed that we will eventually uncover the mysteries surrounding the origins of Taihu Lake.
