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Mississippi Geologic Map

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Before the state of Mississippi there was the Mississippi River, but before the river was a great geologic structure, the Mississippi Embayment. (more below)
Mississippi's rocks

Created by Andrew Alden from the U.S. Geological Survey's Geologic Map of the United States, 1974, by Philip King and Helen Beikman (fair use policy)

Click the map for a larger version
Geologically, the state of Mississippi is dominated by the Mississippi Embayment along its western side—not the Mississippi River. This is a deep trough or thin spot in the North American continent where a new ocean tried to form once upon a time, cracking the crustal plate and leaving it weakened ever since. Such a structure is also called an aulacogen ("aw-LACK-o-gen"). The Mississippi River has run down the embayment ever since.

As the seas have risen and fallen over geologic time, the river and the sea have combined to fill the trough with sediment, and the trough has sagged under the weight. Thus the rocks that line the Mississipi Embayment are bent downward in its midsection and exposed along its edges, older the farther east you go.

In only two places are there deposits not related to the embayment: along the Gulf coast, where short-lived sandbars and lagoons are regularly swept away and sculpted by hurricanes, and in the extreme northeast where a tiny edge is exposed of the continental platform deposits that dominate the Midwest.

The most distinctive landforms in Mississippi arise along the stripes of rocks. Gently dipping strata that are harder than the rest are left by erosion as low, level ridges, broken off steeply on one face and ramping gently into the ground on the other. These are called cuestas.

More about Mississippi Geology

More Mississippi resources on About.com:
Mississippi Maps
Mississippi Geography, State Symbols & Facts
Mississippi National Parks
Mississippi State Parks
Mississippi Campgrounds
Mississippi Scenic Roads
Mississippi Fishing
Mississippi Saltwater Fishing

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