National Geographic : 1894 May 23
Variations of Types. 73 sists of the even crested ridges similar to those of Pennsylvania which have been so well described by Davis.* As a rule the ridges of the southern Appalachian valley are remarkably even crested and are unquestionably the remnants of a plain. In many cases, however, more or less wide variations from the type are found. In some instances a continuous but irregular ridge seems to rise quite above the peneplain, while in others the wind gaps have a constant altitude and probably represent the old baselevel, while the intervening portions of the ridge rising 100 to 300 feet higher stand, now as then, as a series of knobs above the general level. On the other hand, some ridges composed of less resistant rocks or occupying more exposed positions have been so reduced by subsequent erosion that no points along their crests reach the altitude of the peneplain. In reconstruct ing the peneplain from the valley ridges, careful study is required to determine its true position, and in some regions considerable uncertainty attaches to the determination. On the whole, how ever, the results obtained from the ridges are surprisingly con cordant with those obtained in adjacent regions where the plain is better preserved. Smoky Mountain Type.-This type differs altogether from those previously described and consists almost wholly of baseleveled valleys. They prevail from the vicinity of Roanoke, Virginia, to Cartersville, Georgia, giving rise to some prairie-like country in the heart of the Smoky mountains. It was in these valleys that this peneplain was first recognized. In a paper read before this Society in 1889 Willis described the baseleveled valley of the French Broad river as follows : A broad amphitheater lies in the heart of the North Carolina moun tains which form its encircling walls; its length is forty miles from north to south and its width ten to twenty miles. At its southern gate the French Broad river enters; through the northern gate the same river flows out, augmented by the many streams of its extensive watershed. From these water-courses the even arena once arose with gentle slope to the surrounding heights. . . . But that level floor exists no longer. In it the rivers first sunk their channels, their tributaries followed, the gullies by which the waters gathered deepened, and the old plain was thus dissected. It is now only visible from those points of view from * The Rivers and Valleys of Pennsylvania, by W. M. Davis: Nat. Geog. Mag., vol. i, pp. 183-253. t Round about Asheville, by Bailey Willis: Nat. Geog. Mag., vol. i, pp. 291-300.
1894 Jun 22
1894 Apr 25