Mega-Flood Doomed Cahokia?

Here's an interesting report from NatGeo regarding the fall of the Mississippian Culture. I always figured the residents walked away...this new analysis posits why.

Did a Mega-Flood Doom Ancient American City of Cahokia?
One thousand years ago, on a floodplain of the Mississippi River near modern-day St. Louis, the massive Native American city known today as Cahokia sprang suddenly into existence. Three hundred years later it was virtually deserted.

The reasons for Cahokia's quick emergence and precipitous decline have been among the greatest mysteries in American prehistory, but new research suggests a possible cause of the city's demise: a catastrophic flood. NatGeo

reply to post by JohnnyCanuck


Is it just me or has National Geographic gone 100% closed to the public without an account made? I see stories there for about 5-8 seconds, then get a pop-up demanding a sign in or create a new account without any obvious way to get rid of it?

* a note to add here, this was apparently a random thing, as using a NatGeo source later this evening gave no problems.

reply to post by JohnnyCanuck


That's very interesting JC,

It must have been one heck of a flood to force them away. Or it might have been of factors with a social component, ie rebellion against the elite combined with a disastrous flood. One would think that they were no strangers to large floods.

reply to post by JohnnyCanuck

Nice find Johnny...

A team led by Samuel E. Munoz, a doctoral student at the University of Wisconsin, Madison, reported at the 2013 conference of the Geological Society of America that their study of sediment cores from a lake adjacent to the site of Cahokia reveals calamitous flooding of the area around 1200 C.E., just as the city was reaching its apex of population and power.

While analyzing cores from Horseshoe Lake, an oxbow lake that separated from the Mississippi River some 1,700 years ago, Munoz's team discovered a layer of silty clay 19 centimeters (7.5 inches) thick deposited by a massive ancient flood.

This would make sense. No food. No reason to stay. However, the question that comes to mind is, how long did these floods last? I would think flooding like this would be a shorter term event. Although if it was a yearly occurrence, that would certainly add to the theory. S&F.

reply to post by Wrabbit2000

I have seen that before Wrabbit, but I didn't get it this time.

punkinworks10
reply to post by JohnnyCanuck

 

That's very interesting JC,

It must have been one heck of a flood to force them away. Or it might have been of factors with a social component, ie rebellion against the elite combined with a disastrous flood. One would think that they were no strangers to large floods.

No flood would do it, quickly too. Think about the time and the type of shelter and what struggle life was already without dealing with flood. It is possible the Buffalo herds took massive hit during large flood event. If the event also happened during cold weather the results would be exponentially worse.

Everything for people, ancient native Americans, all across a wide area were dependant on the herds of Buffalo. Society rose and fell with food and water. The other side of this coin is drought. This too has a huge impact on society.

I can easily see where a great flood could have caused the demise of a great city and culture.

The Bot

dlbott

punkinworks10
reply to post by JohnnyCanuck

 

That's very interesting JC,

It must have been one heck of a flood to force them away. Or it might have been of factors with a social component, ie rebellion against the elite combined with a disastrous flood. One would think that they were no strangers to large floods.

No flood would do it, quickly too. Think about the time and the type of shelter and what struggle life was already without dealing with flood. It is possible the Buffalo herds took massive hit during large flood event. If the event also happened during cold weather the results would be exponentially worse.

Everything for people, ancient native Americans, all across a wide area were dependant on the herds of Buffalo. Society rose and fell with food and water. The other side of this coin is drought. This too has a huge impact on society.

I can easily see where a great flood could have caused the demise of a great city and culture.

The Bot

That's funny...since the Great Flood of the early 90's and the botched flooding caused by the Army Corp of Engineers along the Missouri...nobody seems to have fled in droves. They even built more IN THE FLOOD PLAIN outside of St. Louis. Earth City, MO never really existed until after the waters receded and businesses bought the land cheap.
Farming culture had to exist for such a large city. It was presumably bigger than London at the same time.

reply to post by JohnnyCanuck

My theory is thin layer of good topsoil was covered-up by "silty clay" on a massive area where the corn was grown making it almost impossible for agriculture to continue there.
The dust bowl was caused by planting repeated crops on too thin a topsoil typical of prairies states.

reply to post by dlbott


I have to strenuously disagree with you, these people were well familiar with flooding on a large scale, any one living on the flood plain would have been. Flooding is why these people built their settlements on mounds for this reason.
They were also not dependant on the buffalo, they were an agricultural society.
The question one had to ask is what mechanism caused folding on such a scale as to cause these people to abandon generations worth of development.

reply to post by JohnnyCanuck


Hey there johnnycanuck,
I just came across this nifty article, about a great fire at the beginning of the down fall of the city.

Excavations in the Midwest have turned up evidence of a massive ancient fire that likely marked “the beginning of the end” for what was once America’s largest city, archaeologists say.

The digs took place in southern Illinois, just meters away from the interstate highways that carve their way through and around modern-day St. Louis. But 900 years ago, this was the heart of Greater Cahokia, a civilization whose trade routes and religious influence stretched from the Great Lakes to the Deep South, and whose culture shaped the lifeways of the Plains and Southern Indians.

westerndigs.org...

Here, researchers with the Illinois State Archaeological Survey have discovered a widespread layer of charcoal and burned artifacts among the foundations of ancient structures — evidence of a great and sudden conflagration that consumed perhaps as many as 100 buildings.

While there’s only “circumstantial evidence” as to what caused the fire, the researchers say, what’s even more striking is that the event seems to mark an ominous turning point in Cahokian culture.

The structures destroyed by the fire were never rebuilt, the excavations showed. Meanwhile, other large, important buildings, like distinctive ceremonial “lodges” or houses for local elites, stopped appearing altogether throughout the region. And soon after the fire, a great palisade wall went up around the nearby city center — known to archaeologists as Downtown Cahokia — most likely for protection.

“My colleagues and I believe that we have pinpointed a major turning point in ancient Cahokia’s history,” writes Dr. Tim Pauketat, archaeologist at the University of Illinois, in a statement.

“We have found, we think, the beginning of the end of this American Indian city.”

I suppose it depends on the duration of the flood, the population in the city, and what kind of the support they had to see them through.

If they were an agricultural culture, they needed sufficient stores to see them through the winter. They also needed good harvests to build up those stores.

The larger the city population was, the harder it would be to achieve these things and the larger an area they would need to support their population.

If you had a big enough flood coming after a series of bad harvests, you could theoretically have a situation where the city was operating off of already depleted or low stores then you have a flood that wipes out existing stores and ruins the growing season for a wide area around the city forcing people to move or face certain starvation.