Alabama Landscapes
The Piedmont
Physiographic Districts
Relationship of Physiographic Districts to Geology
Although described as a plateau, the relatively flat nature of the upland is only obvious in its southern region. The northern part contains many of the highest peaks in the state, including the highest--Mt. Cheaha (2,407 feet)--and numerous northeasterly-trending steep-sided ridges.
A shorter version of this discussion occurs in the Encyclopedia of Alabama ( http://eoa.auburn.edu/face/Article.jsp?id=h-1309)
This distinction between a relatively rugged and a flat landscape serves to divide the Piedmont Upland into two physiographic districts: the Northern Piedmont Upland--developed on rocks of the Talladega and Ashland-Wedowee belts--and the Southern Piedmont Upland (developed on rocks of the Dadeville, Opelika, Pine Mountain and Uchee belts: Figure P1 and Figure PG1). The boundary between the districts is the Brevard Fault zone, which roughly follows the course of the Tallapoosa River in the vicinity of Lake Martin (Tallapoosa County). In Randolph County the boundary swings more northeasterly and follows the valley of High Pine Creek, passing just north of Roanoke.
A topographic profile from Lincoln (Talladega County) to Phenix City (Russell County) shows the topographic differences between the two districts and their underlying geology (Figure PD1).
Figure PD1. Topographic Profile from Lincoln to Phenix City showing the differences in elevation and ruggedness of the Northern Piedmont and Southern Piedmont Upland. Red lines: faults. Geologic Belts are TB: Talladega Belt, AWB: Ashland-Wedowee Belt, DB: Dadeville Belt, OB: Opelika Belt, PMB: Pine Mountain belt, UB: Uchee Belt. The vertical scale is exaggerated about 80 times horizontal scale. (see Figure P1 for location of profile.)