The floods must have been so extreme that they destroyed the complex system of navigable canals, dams and water reservoirs in the Yangtze Delta
Referred to as “China’s Venice of the Stone Age“, the Liangzhu excavation site in eastern China is considered one of the most significant testimonies of early Chinese advanced civilization. More than 5000 years ago, the city already had an elaborate water management system. Until now, it has been controversial what led to its sudden collapse. Massive flooding triggered by anomalously heavy monsoon rains caused the collapse, as an international team with Innsbruck geologist and climate researcher Christoph Spötl has now shown.
Many of the remains of the Liangzhu-Kultur are elaborately crafted jade objects like congs (vessels) or bi-items (discs). These stone artifacts had a strong influence on the culture of other neolithic sites in China.
In the Yangtze Delta, about 160 km southwest of Shanghai, the archeological ruins of Liangzhu City are located. They are Unesco World Heritage.
There, a highly advanced culture blossomed about 5300 years ago, which is considered to be one of the earliest proofs of monumental water culture. The walled city had a complex system of navigable canals, dams and water reservoirs.
This system made it possible to cultivate very large agricultural areas throughout the year. In the history of human civilization, this is one of the first examples of highly developed communities based on a water infrastructure.
Metals were still unknown in this culture.
However, the advanced civilization came to an abrupt end after blossoming for more than 1000 years. “A thin layer of clay was found on the preserved ruins, which points to a possible connection between the demise of the Liangzhu culture and floods of the Yangtze River or floods from the East China Sea. No evidence could be found for human causes such as warlike conflicts,“ explains Austrian scientist Christoph Spötl, head of the Quaternary Research Group at the Department of Geology, Innsbruck University. “However, no clear conclusions on the cause were possible from the mud layer itself.“
The researchers focussed on caves and deposits there, such as dripstones, which allow the reconstruction of climatic conditions above the caves up to several 100,000 years into the past.
Geologists from Xi’an Jiaotong University in Xi’an, who spent a year at the University of Innsbruck, took samples of stalagmites from the two caves Shennong and Jiulong. They are located in the same area affected by the Southeast Asian monsoon as the Yangtze delta.
Data from the stalagmites show that between 4345 and 4324 years ago there was a period of extremely high precipitation. Evidence for this was provided by the isotope records of carbon, which were measured at the University of Innsbruck. The precise dating was done by uranium-thorium analyses at Xi’an Jiaotong University, whose measurement accuracy is ± 30 years.
“The massive monsoon rains probably led to such severe flooding of the Yangtze and its branches that even the sophisticated dams and canals could no longer withstand these masses of water, destroying Liangzhu City and forcing people to flee,“ Haiwei Zhang concludes.
The very humid climatic conditions continued intermittently for another 300 years, as the geologists could show from the cave data.
The history and the remnants of the Liangzhu culture are preserved in the Liangzhu Museum. It was built in 2018 by David Chipperfield architects clad with a travertine facade.
(21.12.2021, USA: 12.21.2021)