The Mississippi River Delta is an unstable place, geologically speaking. Built by sediments deposited by the Mississippi River over thousands of years, the delta is at the mercy of the river's path. In the past, the river regularly changed course, moving the supply of sediments from one place to another. As some areas gained land, areas cut off from the river gradually compacted, sunk and eroded, eventually forming the bayous, lakes, and bays that today make up the largest coastal wetlands in the continental United States.
Over thousands of years, sediments carried by the Mississippi River collected and formed the delta--25,000 square kilometers (9,650 square miles) of land, about half of which is wetlands, on the Louisiana coast.
The Mississippi River Delta is a refuge for hundreds of animal species, including 40 percent of the migratory waterfowl in the United States, and supports many commercial fisheries and a booming recreation industry. It also supplies about 15 percent of the country's domestic oil and hosts one of the world's largest and busiest port systems.