Mississippi River May Have Flooded Cahokia and Destroyed Its Settlement

History may be rewritten as geographers found evidence that Cahokia may have been destroyed by Mississippi River floods and not just by drought as was earlier thought.

Researchers at University of Wisconsin-Madison found evidence in material forming the bed of two lakes, for eight major flooding events in the last 2,000 years. One flooding event in the year AD 1,200 proved to be last straw for the major prehistoric settlement north of Mexico. Until recently, drought was considered as the primary reason for the settlement's vanishing. Now mounds from the settlement are a historic attraction.

"We are not arguing against the role of drought in Cahokia's decline but this presents another piece of information," said researcher Samuel Munoz. His team collected samples from Horseshoe Lake that is said to be located at the center of ruined settlement. The Mississippi River which is located on the east of St. Louis runs in its vicinity.

According to Munoz and his team, floods were common in the region before AD 300 and AD 600 but the climate turned more arid later which caused people to move into the floor plain and populate the area. Researchers also learnt that the river would have rose by 10 meters above its elevation at St. Louis when if flooded nearby areas.

To validate their findings, researchers also studied sediments from the Grassy Lake about 120 miles downstream of Cahokia only to find sediments similar to the flooding patterns seen in the Horseshoe Lake.