In extreme northwest Georgia lie two elongated flat-top mountains: Lookout Mountain and Sand Mountain. These mountains mark a transition zone between the Ridge and Valley province to the southeast, and the Cumberland Plateau to the northwest. As transitional terrain, these mountains may in some way be considered part of either zone. The smaller Lookout Mountain extends northeast from Alabama through Georgia into Tennessee; its northern tip overlooks Chattanooga. The much larger Sand Mountain, northwest of and parallel to Lookout Mountain, extends farther south into Alabama and farther north into Tennessee. Dissected by the Tennessee River, Sand Mountain's landform extends north to mid-Tennessee bearing the name Walden Ridge.
Both mountains comprise Paleozoic sedimentary rock like that of the Ridge and Valley and Cumberland Plateau. Both mountains have nearly flat tops; in cross-section, their strata show gentle synclinal (trough-like) structure. Valleys flanking these mountains show anticlinal (arch- or ridge-like) structure. Evidently, today's valley strata were folded upward in the collision that assembled Pangea. Cracks in these upward folds allowed water to penetrate; 300 million years of erosion reduced former fractured ridges to valleys, leaving Sand and Lookout Mountains relatively intact.
Gorges and coves in these mountains show some of northwest Georgia's finest scenery. Toward Lookout Mountain's northern end, Cloudland Canyon (Sitton Gulch) looks north toward the Tennessee River, cutting through sandstone, limestone, and shale in scarps and slopes. Farther south on Lookout Mountain lies Alabama's spectacular Little River Canyon. Also on the north end of Lookout Mountain, in abandoned coal mine dumps you may find Pennsylvanian plant fossils in shale.