Southern Illinois - Geography

Geography

Illinois has been partially covered at times by continental ice sheets. Specifically, Southern Illinois was only partially covered by continental ice sheet during the Illinoian Stage and not at all during the Wisconsin Stage. Thus, the geography of Southern Illinois is considerably more hilly and rocky than central or northern Illinois. Areas of Southern Illinois are more similar to the Ozarks than to central or northern Illinois.

Additionally, the rich farm land of northern and central Illinois is generally not found in Southern Illinois. Significant exceptions are the American Bottom along the Mississippi River and the alluvial soils of the Gulf Coastal Plain, a large region that has its northernmost extent in the two river valleys of Southern Illinois.

The region's other major river, the Ohio River, winds generally southwest, past Shawneetown, Cave-in-Rock, Elizabethtown, and Golconda. Its waters join the Mississippi at Cairo. In ancient times, the Ohio is thought to have flowed a more northerly course through Pope and Pulaski counties. It carved a broad valley there, fit for a major river. But today the underfit Bay Creek and Cache River occupy those valleys.

The hills of Little Egypt can be divided into two areas. The western area, more closely related to the Ozarks of Missouri, is chiefly in southern Jackson, Union, northern Alexander and Johnson counties. The eastern area, more closely related to the Wabash Valley Seismic Zone, is mostly in northern Pope, southern Saline, Gallatin, eastern Johnson and southern Williamson counties. The Shawnee National Forest covers a large territory, including seven wilderness areas: Garden of the Gods, Bay Creek, Clear Springs, Bald Knob, Burden Falls, Lusk Creek, and Panthers Den.

Of southern Illinois' rivers, only the Mississippi and the Ohio are navigable for modern commerce. The Big Muddy River, Marys River, Saline River and Cache River run their courses in deep southern Illinois. The Kaskaskia River and Wabash River are nearby.