Description of the Nantahala Quadrangle

DESCRIPTION OF THE NANTAHALA QUADRANGLE. By Arthur Keith. GEOGRAPHY. have been changed to slates, schists, or similar except the eastern slope is drained westward by beyond the junction of these two rivers the valley rocks by varying degrees of metamorphism, or tributaries of the Tennessee or southward by tribu is hemmed in by steep mountains and becomes a GENERAL RELATIONS. igneous rocks, such as granite and diabase, which taries of the Coosa. narrow and rocky gorge. The descent of 4000 feet Location. The Nantahala quadrangle lies mainly have solidified from a molten condition. The position of the streams in the Appalachian from Hangover to the mouth of Cheoah River is in North Carolina, but in its northwest corner The ,western division of the Appalachian prov Valley is dependent on the geologic structure. In accomplished in a trifle over 4 miles. includes also a few square miles of Tennessee. It ince embraces the Cumberland Plateau and Alle general they flow in courses which for long dis Hiwassee River below Hayesville is bordered by is bounded by parallels 35° and 35° 30' and merid gheny Mountains and the lowlands of Tennessee, tances are parallel to the sides of the Great Valley, plateaus of the same character as those on the Little ians 83° 30' and 84°, and contains 985 square miles, Kentucky, and Ohio. Its northwestern boundary following the lesser valleys along the outcrops of Tennessee. A short distance above that point the in Graham, Swain, Macon, Clay, and Cherokee is indefinite, but may be regarded as an arbitrary the softer rocks. These longitudinal streams empty river is nearly at the level of the plateau. Valley counties, North Carolina, and Monroe and Blount line coinciding with the eastern boundary of the into a number of larger, transverse rivers, which River, although a smaller stream, has cut its chan counties, Tennessee. Mississippi embayment as far up as Cairo, and cross one or the other of the barriers limiting the nel wider than the Hiwassee, because much of its In its geographic and geologic relations this then crossing the States of Illinois and Indiana. valley. In the northern portion of the province course is on the marble beds (see fig. 3 on colum quadrangle forms part of the Appalachian prov Its eastern boundary is sharply defined along the they form Delaware, Susquehanna, Potomac, James, nar section sheet). The ready solubility of these ince, which extends from the Atlantic Coastal Plain Appalachian Valley by the Allegheny Front and and Roanoke rivers, each of which passes through beds has resulted in broad and open valleys along on the east to the Mississippi lowlands on the west, the Cumberland escarpment. The rocks of this the Appalachian Mountains in a narrow gap and the river, from 200 to 300 feet below the plateau and from central Alabama to southern New York. division are almost entirely of sedimentary origin flows eastward to the sea. In the central portion level. Both these rivers have broad terraces cov All parts of the region thus denned have a common and remain very nearly horizontal. The character of the province, in Kentucky and Virginia, these ered with- waterworn pebbles from 25 to 50 feet history, recorded in its rocks, its geologic structure, of the surface, which is dependent on the character longitudinal streams form New (or Kanawha) above the stream level. Each river in this quad and its topographic features. Only a part of this and attitude of the rocks, is that of a plateau more River, which flows westward in a deep, narrow rangle has worn its basin down to its particular history can be read from an area so small as that or less completely worn down. In the southern gorge through the Cumberland Plateau into Ohio local base-level, and the plateaus thus produced represented on a single atlas sheet; hence it is neces half of the province the Plateau is sometimes River. From New River southward to northern have different heights, varying according to the sary to consider the individual area in its relations extensive and perfectly flat, but it is oftener much Georgia the Great Valley is drained by tributaries difficulty of erosion. All of the stream valleys to the entire province. divided by streams into Large or small areas with of Tennessee River, which at Chattanooga leaves except the Nantahala were reduced to substantially Subdivisions of the Appalachian province. The flat tops. In West Virginia and portions of Penn the broad valley and, entering a gorge through the same level 2000 to 2100 feet. The plateaus Appalachian province is composed of three well- sylvania the Plateau is sharply cut by streams, leav the Plateau, runs westward to the Ohio. South which now appear on the Nantahala were pro marked physiographic divisions, throughout each of ing in relief irregularly rounded knobs and ridges of Chattanooga the streams flow directly to the duced at a considerably earlier date than those of which certain forces have tended to produce similar which bear but little resemblance to the original Gulf of Mexico. the other streams and are about 1000 feet higher. results in sedimentation, in geologic structure, and surface. The western portion of the Plateau has Above the levels of the different plateaus the val DETAILED GEOGRAPHY OF THE QUADRANGLE. in topography. These divisions extend the entire been completely removed by erosion, and the sur leys are wild and rocky V-shaped ravines, with length of the province, from northeast to southwest. face is now comparatively low and level, or rolling. Geographic divisions. The Nantahala quadran slopes steadily increasing nearly to the divides. The central division is the Appalachian Valley. Altitude of the Appalachian province. The gle is included entirely in the Mountain division Topography. The variations in the topography It is the best defined and most uniform of the Appalachian province as a whole is broadly dome of the Appalachian province. The quadrangle of this region depend very largely upon the influ three. In the southern part it coincides with the shaped, its surface rising from an altitude of about includes the Great Smoky Mountains on the north, ence of erosion on the different formations. Such belt of folded rocks which forms the Coosa Valley 500 feet along the eastern margin to the crest of the Blue Ridge on the southeast, and various cross rock-forming minerals as carbonates of lime and of Georgia and Alabama and the Great Valley of the Appalachian Mountains and thence descending ranges in the center. In this region there is less magnesia, and to a less extent feldspar, are East Tennessee and Virginia. Throughout the cen westward to about the same altitude on Ohio and correspondence than usual between the forms of the removed by solution in water. Rocks contain tral and northern portions the eastern side only is Mississippi rivers. surface and the underlying strata. This-is true ing these minerals in large proportions are, there marked by great valleys such as the Shenandoah Each division of the province shows one or of the details of the formations as well as of the fore, subject to decay by solution, which breaks up Valley of Virginia, the Cumberland Valley of more culminating points. Thus the Appalachian broad geologic divisions. The surface of the region the rock and leaves the insoluble matter less firmly Maryland and Pennsylvania, and the Lebanon Mountains rise gradually from less than 1000 feet is that of a number of mountain ranges running in united. Frost, rain, and streams break up and Valley of eastern Pennsylvania the western side in Alabama to more than 6700 feet in western various directions, separated by narrow stream val carry off this remainder, and the surface is thus being a succession of ridges alternating witK narrow North Carolina. From this culminating point leys and small plateaus. The area which lies in worn down. According to the nature and amount valleys. This division varies -in width from 40 to they decrease to 4000 or 3000 feet in southern Tennessee is very small and differs in no respect of the insoluble matter the rocks form high or low 125 miles. It is sharply outlined on the southeast Virginia, rise to 4000 feet in central Virginia, and from the North Carolina portion. ground. Calcareous rocks, leaving the least resi by the Appalachian Mountains and on the north descend to 2000 or 1500 feet on the Maryland- Drainage. The region is drained by six rivers. due, make the low ground. Such are the Nottely west by the Cumberland Plateau and the Alle Pennsylvania line; One of these, the Tallulah, flows south from the marble and the Andrews schist; these leave a fine gheny Mountains. Its rocks are almost wholly The Appalachian Valley shows a uniform Blue Ridge at Standing Indian and finds its way clay after solution. The least soluble rocks are sedimentary, "and are in large measure calcareous. increase in altitude from 500 feet or less in into the Atlantic. Of the others, the Nantahala the quartzites and the more siliceous portions of The strata, which must originally have been nearly Alabama to 900 feet in the. vicinity of Chatta and Cheoah join the Little Tennessee within this the Great Smoky conglomerate. Since most of horizontal, now intersect the surface at various nooga, 2000 feet at the Tennessee-Virginia line, quadrangle; Valley and Hiwassee rivers unite just their mass is left untouched by solution they are angles and in narrow belts. The surface features and 2600 or 2700 feet at its culminating point, west of the quadrangle and also join Tennessee among the last to be reduced in height.

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