More than 4,000 years ago, one of the most advanced societies of ancient China, called the “Chinese Venice of the Stone Age” for its sophisticated water management system, suddenly disappeared.
The reason for Liangzhu’s abrupt disappearance was unclear until now, but according to a new study published in Science Advances, the city was destroyed not by war or famine, but by an unusually strong monsoon season that flooded the region.
The ruins of Liangzhu are located in the Yangtze Delta, about 160 kilometers southwest of Shanghai. It is all that remains of an advanced society that existed about 5,300 years ago.
Liangzhu has only recently been recognized for its archaeological significance: it was declared a World Heritage Site by the United Nations in 2019 because it is one of the earliest societies to show an advanced water infrastructure.
The walled city was filled with canals, dams, and reservoirs that fed farmland throughout the year. The archaeological site is also rich in jade artifacts: thousands of artfully carved pieces were found during excavations.
It was previously speculated that the flood may have caused the city’s demise, but this has not been proven.
“A thin layer of clay was found on the surviving ruins, suggesting a possible connection between the death of an advanced civilization and flooding on the Yangtze River or flooding from the East China Sea,” Christoph Spöttl, a geologist at the University of Innsbruck and one of the authors of the new study, said in a press release.
“No evidence of human causes, such as military conflicts, could be found. However, no clear conclusions about the causes could be drawn from the mud layer itself.”
To confirm that a climatic event caused the end of this 1,000-year-old society, the researchers dug into archives containing data on caves in the area. Specifically, they studied stalactites and stalagmites that were formed by thousands of years of sediment flowing down from the caves’ ceilings. These cave structures give researchers a glimpse into the past and “allow them to reconstruct climatic conditions over the caves up to several 100,000 years ago,” the release said.
“These caves have been well studied for many years,” Spoettl said. “They are located in the same area that is influenced by the Southeast Asian monsoon as the Yangtze Delta, and their stalagmites give an accurate idea of the time of the decline of the Liangzhu culture, which according to the archaeological evidence occurred about 4,300 years ago.”
Between 4,345 and 4,324 years ago, the city and its surroundings were subjected to an unusually heavy rain bombardment. It was the specific carbon isotope records found in the cave samples that allowed researchers to determine exactly when the rainfall increased. The lab at Xi’an Jiaotong University tested the samples and determined with confidence within 30 years give or take when the rains hit Liangzhu.
“The massive monsoon rains probably caused the Yangtze and its branches to flood so much that even the complex dams and canals could no longer withstand these masses of water, destroying the city of Liangju and forcing people to flee,” Spöttl said.