The Valley and Ridge
The Tennessee Section of the Valley and Ridge Province (hereafter called the Valley and Ridge) occupies about 9% of the state. It occurs as a roughly northeast trending rectangular-shaped area in central and east-central Alabama. Its northwestern boundary passes to the west of Birmingham and Gadsden and its southeastern boundary occurs near Sylacauga (Talladega County) and Talladega (Talladega County). The southwestern boundary occurs near Centerville (Bibb County).
Figure HR1. Location Map of the Valley and Ridge Section in Alabama. Black line: southeast boundary of the Valley and Ridge based on recent work. (Base map from Cartographic Research Lab, University of Alabama)
The Valley and Ridge is bordered by the Cumberland Plateau to the northwest, the East Gulf Coastal Plain to the south and the Piedmont Upland to the southeast (Figure HR1). The the southeastern boundary with the Piedmont was originally mapped in northwestern Coosa County and northeastern Chilton County. More recent work has shown that Piedmont rocks occur much further to the north and west than originally thought. The map shows two boundaries in this area: the more northerly boundary that passes near Columbiana (Shelby County) is based on the newer work (solid black line in Figure HR1), whereas the southern boundary is that based on the original work. The Valley and Ridge continues northeast into Georgia and Tennessee, where it is includes the valley of the Tennessee River.
The landscape, which has developed on tightly-folded and thrust-faulted Paleozoic sedimentary rocks, consists of numerous ridges separated by deep steep-sided valleys. A unique feature of the Valley and Ridge is the “zigzag” nature of the ridges. (Figure HR2 and Cahaba and Coosa Ridges, Cahaba Valley).
Figure HR2. Image of the Valley and Ridge showing zigzag ridges in bottom right. Birmingham is top left. (NASA)
In 2000, the Valley and Ridge contained about 1.2 million people. Population density was the highest in the state (~216 persons/square mile). Twenty eight percent of the population was Black or African American.
Three major highways run through the Valley and Ridge (Figure HR1), with Birmingham as the hub. Interstate 65, passes north-south through Birmingham connecting Huntsville to Montgomery. I-59 connects Birmingham to Gadsden and I-20 connects Tuscaloosa to Birmingham to Atlanta. Birmingham is also the hub of an extensive rail system, used primarily for freight.
Average annual temperatures range from 60oF in Gadsden (Etowah County) to 62oF in Birmingham (Jefferson County) and rainfall averages about 55 inches.An abbrevited version of this article occurs in the Encyclopedia of Alabama (http://eoa.auburn.edu/face/Article.jsp?id=h-1308)