As the lush vegetation of summer surrounds the Mississippi Alluvial Plain, its tan coloration stands out against a field of green to the east and west.

The plain is sometimes referred to as the Delta region and is covered with rich soil carried by the Mississippi River and its tributaries. It’s tan coloration is due to the deposits of clay, silt, sand and gravel left behind by those flowing waterways.

An alluvial plain is technically different from a flood plain, which refers to an area often inundated when a river or stream overflows.

The relatively flat alluvial plain is created by millions of years of deposits and encompasses a far larger area representing the region where the flood plain has shifted during geological time.

The Mississippi Alluvial Plain is divided into sections known as the Mississippi embayment and the Mississippi Delta.

The embayment is generally the area on the west side of the Mississippi River from the southern tip of Illinois to northern Louisiana. The Mississippi Delta is generally to the east of the river.

The image of the region to the upper right was taken at midday on June 17, 2009, by NASA’s Aqua satellite. The relatively cloud-free conditions that prevailed at that moment in the lower Mississippi River Valley allows the plain to be clearly seen from southeastern Missouri to southern Louisiana.

The enlarged view highlights a portion across northeastern Arkansas. There, the Mississippi Embayment is broken by a strip of dark green stretching from north to south. This narrow region of wooded rolling hills is known as Crowley’s Ridge and rises about 250 to 550 feet above the alluvial plain.

It was formed when the ancestral Mississippi and Ohio rivers eroded away the land on each side and grew in height as deposits of wind-blown soils accumulated on the ridge that remained.

Full story and image: NASA