Crowley's Ridge
Crowley's Ridge is an unusual geological formation that rises 250 to 550 feet above the flat plain of the Mississippi embayment in a 150-mile line from southeastern Missouri to the Mississippi River near Helena, Arkansas. It varies from half a mile to 12 miles wide and reaches an elevation of 550 feet. The ridge probably separated the Mississippi and Ohio Rivers thousands of years ago. Melting of glaciers in Canada sent water gushing on both sides of the ridge and carried most of the rock and sediment on either side of the ridge to the Gulf of Mexico.