Description of the Bristol Quadrangle

DESCRIPTION OF THE BRISTOL QUADRANGLE. GENERAL RELATIONS. with the Mississippi River as far up as Cairo, and Kanawha and Tennessee rivers, and to the Gulf trunk stream. A glance at the prominent surface thence extending northeastward across the States by the Alabama River. features, as shown on the map, would Divides. The Bristol quadrangle includes one-quarter of of Illinois and Indiana. In the north The positions of the streams in the Appalachian lead to the supposition that the highest a square degree of the earth's surface, extending ern part of the province the eastern vision "its" Valley are mainly dependent upon the geologic ridge, Clinch Mountain, divides the territory into - -, p -,.-.... , -, extent and from latitude 36° 30' on the south to 37° on the boundary ol this division is sharply f^gj^e structure. In a <->general wayi/ they«/ flow Arrangement. two drainage basins, but close examination shows north, and from longitude 82° on the east to 82° defined by the Allegheny front, and in in courses which, for long distances, ofstreams- that the comparatively low Moccasin Ridge forms 30' on the west. Its average width is 27.8 miles, the southern part by the eastern escarpment of the are parallel to the mountains on either side, fol the divide between Clinch River and the North its length 34.4 miles, and its area 956.6 square Cumberland Plateau. The rocks of this division lowing the outcrops of the softer rocks. These Fork, of Holston River, nearly as far east as miles. are almost entirely of sedimentary origin, and they longitudinal streams empty into a number of Lebanon; and that the equally unimportant Politically the quadrangle is divided into two remain very nearly horizontal. The topography, larger, transverse rivers which cross one or the Walker Mountain separates the North and South parts by an east-west line which passes through which is dependent on the character and attitude other of the barriers limiting the valley. In the forks of Holston River throughout the extent of the city of Bristol. That part which Location of of the rocks and the conditions under which ero northern part of the province these transverse this quadrangle. lies south of this line has an area of iuadransle- sion has operated in the past, is that of a series of rivers are the Delaware, Susquehanna, Potomac, Clinch River is the largest stream in this 180 square miles and is wholly within Sullivan plateaus, more or less dissected and decreasing in James, and Roanoke, each of which flows east territory. It enters the quadrangle near its County, Tennessee. The part lying north of the altitude westward from the Allegheny front and ward to the sea. In the central part of the prov northeastern corner, crosses it diago Clinch River. above-mentioned line has an area of 776 square the Cumberland escarpment. In Tennessee the ince the longitudinal streams form the New (or nally, and leaves it near the middle of miles and is included in the counties of Washing surface of the highest plateau is composed of hard Kanawha) River, which flows westward in a deep, the western side. Although this stream generally ton, Scott, Russell, Wise, and Dickenson, Virginia. rocks, which have withstood the attacks of erosion, narrow gorge through the Cumberland Plateau pursues a direct course, its channel is very tortuous The quadrangle receives its name from the city of and as a consequence the plateau is very perfectly into the Ohio River. From New River to north and it crosses and recrosses geologic formations Bristol, which is the most prominent town within preserved ; in the northern part of the division it ern Georgia the valley is drained by tributaries without any apparent regard for the character of its borders and which is located on the boundary has had no such protecting cap, and the streams of the Tennessee River, which also crosses the the rocks. It is probable that these short bends line between the two States. have cut deep and narrow valleys in its once level Cumberland Plateau in its course to the Ohio. are features inherited from a previous age, when" In its geographic and geologic relations this surface. The highest summits remain at approxi In Georgia and Alabama the streams flow directly the surface relief of the valley was slight and the quadrangle forms a part of the Appa- Relation of mately the same altitude as the former plateau, to the Gulf of Mexico. streams, meandering in a wide flood plain, were lachian province, which extends from but the even surface is gone and in its stead there measurably free from the influence of hard and TOPOGRAPHY. the Atlantic coastal plain on the east provmce' remains a broken, hilly region, difficult of access soft rocks; and that, in a period of active corra- to the Mississippi lowlands on the west, and from and poorly adapted to human habitation. The Bristol quadrangle extends entirely across sion which ensued later, this stream deepened its central Alabama to southern New York. Altitude of the Appalachian province. This the Appalachian Valley, having its southeastern crooked channel, its increased fall giving it suffi Subdivisions of the Appalachian province. province as a whole is broadly arched, its surface corner approximately upon the summit of Holston cient power to cut the hard as well as the soft This province may be subdivided into three well- rising from an altitude of about 500 feet along Mountain, which is the farthest outlier of the rocks which it found in its pathway. marked physiographic divisions, throughout each the eastern margin to the crest of the Appalachian Appalachian group, and its northwestern corner Copper Creek, a tributary of Clinch River, has of which certain forces have produced similar Mountains, and thence descending westward to several miles within the border of the coal field. selected for its course the outcrop of soft lime results in sedimentation, in geologic structure, about the same altitude on the Ohio and Missis From its location with reference to the great stone which lies between the flinty Copper Creek. and in topography. These divisions extend the sippi rivers. physiographic provinces, it follows that rocks of Copper and Moccasin ridges. entire length of the province, from northeast to The Appalachian Mountains rise gradually from the surface features of the quadrangle ofws°urtfa°cleps Near its mouth it has nearly kept pace with the southwest. less than 1000 feet in Alabama to more than 6600 ±all -.-. naturally, -i-i into , two groups, each-10 oi features. trunk stream in the excavation of its valley, but The central division is the Appalachian Valley. feet in western North Carolina. From Altitudes.,.., . of. which is typical of the province to which it along its upper course in this quadrangle it has It is the best denned and most uniform of the this culminating point they descend to belongs. The dividing line which separates these not had sufficient volume to cut its valley below three. It varies in width from 40 to Central_ . , di-., 3000 feet in southern Virginia, rise to Mountains- topographic groups is a fault, or break in the those, of the other minor streams. 125 miles, and is sharply outlined on XppaYacMan 4000 feet in central Virginia, and again descend rocks. On the southeastern side of this fault the Guest River, which drains a territory entirely the southeast by the Appalachian Valley< to 2000 feet on the Maryland-Pennsylvania line. strata have been greatly disturbed, thrown into within the coal field, is another branch of this Mountains and on the northwest by the Cumber The Appalachian Valley shows a gradual great folds, broken by the irresistible force which same system. In some far-off age this Quest River. land Plateau and the Allegheny Mountains. Its increase in altitude from 500 feet or less in Ala crowded them together, and frequently thrust for stream was doubtless located upon rela rocks are almost wholly sedimentary and in large bama to 900 feet in the vicinityJ of Altitudes..... of. great distances perhaps many miles out of tively soft shales and sandstones, but in the latest measure calcareous. The originally horizontal Chattanooga, 2000 feet at the Tennes- £cehfapnpa= their original positions and upon rocks which period of rapid corrasion it encountered a massive strata have been thrust into great folds which in see-Virginia line, and 2500 or 2700 Valley> normally belong above them; on the northwestern conglomerate which so retarded its development many places have been compressed to such an feet at its highest point, on the divide between side of the fault the rocks are somewhat disturbed, that it has not succeeded in deepening its channel, extent that the strata forming the folds have been New and Tennessee rivers. From this point it especially in the immediate vicinity of the break, except for a few miles above the trunk stream. In broken and crowded forward out of their normal descends to 2200 feet in the valley of New River, but in a general way they are nearly horizontal this lower part of its course it has cut a narrow, positions. That portion of the Appalachian Val 1500 to 1000 feet in James River Basin, and 1000 and in approximately the same attitude as that in rocky gorge with almost perpendicular walls, ley which lies within the States of Pennsylvania to 500 feet on Potomac and Susquehanna rivers. which they were deposited. which presents a striking contrast to the broad, and Virginia may be subdivided into two areas These figures represent the average elevation of Drainage. On an old land area, like the Appa flat valley that marks its upper course.

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