America’s First Metropolis
It was America’s first metropolis.
Cahokia, the largest prehistoric settlement in the Americas north of Mexico, flourished in the 1200s, with a population of 20,000 people at its peak – but was mysterious abandoned by 1400.
Now researchers think they know why – a megaflood that raised the Mississippi River by 10m.
New evidence suggests that major flood events in the Mississippi River valley are tied to the cultural center’s emergence and ultimately, to its decline.
Sediment cores from these lakes, dating back nearly 2,000 years, provide evidence of at least eight major flood events in the central Mississippi River valley that could help explain the rise and fall of Cahokia, near present-day St. Louis.
‘We are not arguing against the role of drought in Cahokia’s decline but this presents another piece of information,’ says Samuel Munoz, a Ph.D. candidate in geography and the study’s leadauthor.
‘It also provides new information about the flood history of the Mississippi River, which may be useful to agencies and townships interested in reducing the exposure of current landowners and townships to flood risk,’ says Williams, a professor of geography and director of the Nelson Institute for Environmental Studies Center for Climatic Research.
Published in the Proceedings of the National Academy of Sciences, a research team led by UW-Madison geographers Samuel Munoz and Jack Williams provides this evidence, hidden beneath two lakes in the Mississippi floodplain.
While the region saw frequent flood events before A.D. 600 and after A.D. 1200, Cahokia rose to prominence during a relatively arid and flood-free period and flourished in the years before a major flood in 1200, the study reveals.
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