Scientists seek answers for the abandonment of the Great City of Cahokia
The ancient Native American city of Cahokia, located is Collinsville, Illinois, is known to have been one of the most sophisticated pre-Columbian settlements north of Mexico. At its peak, it was home to some 20,000 people and sprawled over nearly 1,600 hectares. But life in the impressive city came to an abrupt end when it was abandoned some 700 – 800 years ago. According to a report in Live Science, new research published in the journal Geology suggests the mysterious exodus is linked to a massive Mississippi River flood.
Cahokia was once composed of a collection of agricultural communities that reached across the American Midwest and Southeast starting around 800 AD and flourishing between the 11th and 12th century. It is a striking example of a complex chiefdom society, with many satellite mound centres and numerous outlying hamlets and villages. It was also a place where Native Americans made pilgrimages for special spiritual rituals linked to the origin of the cosmos. At its peak, Cahokia boasted some 120 mounds, the largest of which is a ten-story earthen colossus known as Monk’s Mound. The giant mound is the largest prehistoric earthwork in the Americas, covering over 5 hectares and standing 30 metres high. An estimated 22 million cubic feet of earth was used to build the mound between the years of 900 and 1,200 AD, but it was not long after this time that Cahokia was mysteriously abandoned. Why did they go to such massive effort to construct their remarkable city and then leave?
A reconstruction of Cahokia with Monk’s Mound in the distance. Image source.
Scientists have long debated the cause for Cahokia’s abandonment, with some suggesting climate change, and others arguing that it was the result of political battles. But Samuel Munoz, geographer at the University of Wisconsin-Madison, has a new theory.
Munoz has spent a number of years researching how Cahokia’s residents shaped the local landscape, such as how farming affected the region. During this research he discovered the buried remains of a massive flood dated that likely destroyed the crops and houses of more than 15,000 people. Evidence for the flood is a silty layer nearly 20 centimetres thick, dated to 1200 AD, plus or minus 80 years. Although Cahokia wasn’t completely abandoned until 1350 AD, Munoz believes that the catastrophic flood could have shaken the confidence of the city, eventually leading them to make the decision to move on.
"I think the relationships between flooding and the decision to abandon the settlement are pretty complicated, but it's surprising and exciting to discover this flood happened right in the middle of a key turning point in Cahokia's history," Munoz said.
No one knows where the Cahokia people went, but according to Munoz, Mississippian cultural traditions continued in the Southeast for several centuries.
Featured image: An illustration of North America's first city, Cahokia. Image source.