The total relief of Mississippi, from the coastline to the highest elevation at Woodall Mountain, near Iuka in Tishomingo County, is 806 feet. Mississippi’s eleven physiographic regions can be described as alternating bands of ridges and prairies. As a generalization, the hills are underlain by sand or gravel deposits, and the prairies or plains are underlain by clay formations. The physiographic regions map of Mississippi resembles the state geologic map because the terrain formed on the underlying geologic formations. For related reasons, similar patterns can be seen in state maps of soil types and forest types.
The Paleozoic Bottoms are confined to eastern Tishomingo County and are stream valleys underlain by Paleozoic rocks—the oldest exposed in Mississippi. The Tombigbee Hills lie west of the Paleozoic Bottoms and are bounded to the west by a line running through Alcorn, Prentiss, Lee, Monroe, and Lowndes Counties. These hills are underlain by unconsolidated sands and gravels deposited during the Cretaceous period. The Black Prairie or Black Belt is a crescent-shaped strip of level or gently sloping terrain underlain by chalk and marl of the Cretaceous Selma Group. It has rich soils; the northern part of the region is more wooded and has more relief, while the southern part, extending into Alabama, exhibits more continuous plains. To the west of the Black Prairie is a narrow range of hills, the Pontotoc Ridge, that extends as far south as Chickasaw County. This rugged terrain is underlain by Cretaceous sands and sandstones and includes the high points of Lebanon Mountain at 790 feet in elevation and Geeville Mountain at 710 feet.
The Flatwoods is a narrow region (just two to eight miles wide) of low, wooded terrain. It is underlain by the Paleocene Porters Creek Clay and forms an arc from the Tennessee line in Tippah County to the Alabama line in Kemper County. The North Central Hills region is a broad area of uplands underlain by sand and clay formations from the Paleocene and Eocene ages that are noted for containing deposits of lignite, a low-grade form of coal. Stream erosion has created areas of rugged terrain. To the south, the North Central Hills grade into the gently undulating plains of the Jackson Prairie. This region extends from northern Hinds and southern Madison Counties southeast into Clarke County. The Jackson Prairie is underlain by marine clay of the Eocene Yazoo Formation, infamous in central Mississippi for its shrink-swell properties that can damage roads and buildings. South of the Jackson Prairie, the southern third of the state is in the Piney Woods, also known as the Pine Hills region. The Piney Woods is an eroded highland noted for its pine trees and is underlain in the valleys by sands and clays of Miocene age and in the uplands by gravels and sands of the Pliocene Citronelle Formation. Citronelle gravels are mined extensively, particularly in Copiah County.
The Loess Hills or Bluff Hills in western Mississippi extends from the Tennessee line in DeSoto County to Louisiana in Wilkinson County. It is about fifteen to twenty-five miles wide and is underlain by loess, an eolian silt deposited during the Ice Age, and preloess gravel deposits. The loess is thickest—one hundred feet or more—in the Vicksburg-Natchez region. The eastern boundary of the Loess Hills is indistinct, but the western boundary is formed by the very distinctive Bluff Line that separates the hills to the east and the Delta to the west. The Mississippi Alluvial Plain, better known as the Mississippi Delta, lies to the west of the Loess Hills. Also called the Yazoo River Basin, this agriculturally rich area slopes gently from 210 feet above sea level at the Tennessee line to 94 feet at Vicksburg. The Coastal Meadows form a low, flat strip of land between the Piney Woods and the coastline. The region contains sandy ridges that were once barrier islands or beach ridges.
Other landforms include the Mississippi River, which forms much of the state’s western border; alluvial plains of rivers, with their oxbow lakes, meander scars, and terraces; drowned river valleys such as Back Bay of Biloxi; and the chain of barrier islands that define the Mississippi Sound.
- Mississippi Department of Environmental Quality website, http://www.deq.state.ms.us
- Mississippi Office of Geology, Physiographic Regions of Mississippi (2009)