/ u dr. e. hull on the physical geology of 



§ 2. Physical Features. 



1. The Valley of East Tennessee. — ^The physical features of East 

 Tennessee are, when viewed on a large scale, extremely simple, 

 and are a faithful index to the geological structure. Along its 

 eastern margin, where Tennessee joins IS'orth Carolina, the State 

 follows the crest of the Unaka Range, which may be regarded as 

 one of the parallel ridges of the Alleghanies, and is nearly con- 

 tinuous with the Blue .Ridge of Virginia. This ridge is composed 

 chiefly of granite, gneiss, and crystalline schists, presumably of 

 Archaean age, and forming a prolongation of Professor J. D. Dana's 

 " Archaean Protaxis." It attains an elevation of 6760 feet in Black 

 Mountain in North Carolina *, and ranges in a general south- 

 westerly direction. Prom its base stretches the great plain known 

 as "the Yalley of East Tennessee," which extends south-west into- 

 Georgia and Alabama, and in an opposite direction is continued 

 into the Yalley of Virginia or Shenandoah. This rich and fertile 

 plain has an average breadth of about forty miles, and along its 

 course winds the Tennessee River, a noble stream of about 450 yards 

 in average width. The plain itself is closely furrowed by parallel 

 valleys and ridges, all trending in north-east and south-west direc- 

 tions, parallel to the strike of the beds. The ridges and furrows 

 are in fact the outcrops of the harder and softer strata. The whole 

 valley is underlain by Cambrian and Silurian formations, often 

 highly inclined or thrown into numerous flexures. This series is 

 surmounted by the Devonian beds, here very thin, and consisting 

 chiefly of black shale, which lie close to the base of the northern 

 margin formed by the Cumberland Table-land, which I now proceed 

 to describe. 



2. Cumberland Plateau; Waldenh Ridge. — The north-western 

 margin of the Valley of East Tennessee is formed by the escarp- 

 ment of the Cumberland Plateau, which rises abruptly above the 

 plain to a height of 1300 to 1600 feet, or 2000 to 2200 feet above 

 the ocean. The crest of the escarpment, formed of massive grit and 

 conglomerate of Carboniferous age, breaks off into mural precipices, 

 often perfectly vertical. As the Tennessee River hugs the base 

 of this escarpment for many miles, the full height of the cliff 

 is thus obtained at one sweep ; and as the slopes as well as the 

 summit of the ridge are covered with primaeval forest, except where 

 the naked cliff offers no footing for vegetation, the view of this 

 grand escarpment is as striking as it is beautiful. 



The escarpment above described forms the south-eastern margin 

 of the Cumberland Table-land, the surface of which is slightly 

 undulating, formed of Carboniferous beds, and which, below Chat- 

 tanooga, immediately on the west, is traversed by the Tennessee 

 River through a deep and winding gorge about twenty miles in 

 length, where the States of Georgia and Alabama on the south join 



* The granitoid rocks of North Carolina are remarkable for the number, 

 beauty, and size of the minerals they have yielded : specimens are exhibited in 

 t)\e museum of the Smithsonian Institution, Washington. 



