Alexandra Mae Jones writer
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Stalagmites in caves located southwest of the excavation site show a climatic cause for the collapse of the ancient chinese Liangzhu culture. (Haiwei Zhang)
TORONTO — More than 4,000 years ago, one of the most advanced societies in ancient China, referred to as “China’s Venice of the Stone Age” for its complex water management system, disappeared suddenly.
The reason for the abrupt collapse of Liangzhu City hasn’t been clear until now, but according to a new study published in the journal Science Advances, the city was wiped out not by war or famine but by an unusually heavy monsoon season, which flooded the region.
The ruins of Liangzhu City can be found in the Yangtze Delta, around 160 kilometres southwest of Shanghai, all that remains of an advanced society that existed around 5,300 years ago.
Liangzhu has only recently been recognized for its archeological significance, with the United Nations declaring it a World Heritage Site in 2019, but it is one of the earliest societies to display advanced water infrastructure.
The walled city was filled with canals, dams and water reservoirs that fed agricultural sites throughout the year. The archeological site was also rich in jade artifacts, with thousands of intricately carved pieces found during excavations.
It had been posited before that flooding could’ve led to the demise of the city, but it hadn’t been proven.
“A thin layer of clay was found on the preserved ruins, which points to a possible connection between the demise of the advanced civilization and floods of the Yangtze River or floods from the East China Sea,” Christoph Spötl, a geologist with the University of Innsbruck and one of the authors of the new research, said in a press release. “No evidence could be found for human causes such as warlike conflicts. However, no clear conclusions on the cause were possible from the mud layer itself."
In order to confirm that a climate event caused the end of this society, which existed for 1,000 years, researchers dug through archives containing data on caves in the area. Specifically, the data looked at stalactites and stalagmites that were formed by thousands of years of precipitation dripping down from the ceiling of the caves. These cave structures allow researchers to peer into the past and “allow the reconstruction of climatic conditions above the caves up to several 100,000 years into the past,” the release stated.
"These caves have been well explored for years,” Spötl said. “They are located in the same area affected by the Southeast Asian monsoon as the Yangtze delta and their stalagmites provide a precise insight into the time of the collapse of the Liangzhu culture, which, according to archeological findings, happened about 4,300 years ago.”
Between 4,345 and 4,324 years ago, the city and the surrounding area was bombarded with an unusually high level of rain. It was the specific isotope records of carbon found in the cave samples that allowed researchers to pinpoint at what time this precipitation increased. A lab at Xi’an Jiaotong University tested the samples and were confident within 30 years plus or minus that they had found the time when the rain pummelled Liangzhu.
"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,” Spötl said.
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