Wartburg folio, Tennessee

Abstract

G-eneral relations. The region represented by the Wartburg atlas sheet lies, entirely in Tennessee. It is included between parallels 36° and 36° 30' and meridians 84° 30' and 85°, and Extentof it contains 963 square miles, divided q«at«rangie. between Scott, Morgan, Cumberland, and Fentress counties. In its geographic and geologic relations this quadrangle forms a part of the Appalachian province, which extends from the Deflnition of Atlantic coastal plain on the east to tuVprovince. the Mississippi lowlands on the west, and from central Alabama to southern New York. All parts of the region thus defined have a common history, recorded in its rocks, its geologic structure, and its topographic features. Only a part of this history can be read from an area so small as a single quadrangle; hence it it necessary to consider the individual quadrangle in its relations to the entire province. Subdivisions of the Appalachian province. The Appalachian province may be subdivided into three well-marked physiographic divisions, throughout each of which certain forces have produced similar results in sedimentation, in geologic structure, and in topography. These divisions extend the entire length of the province, from northeast to southwest. The central division is the Appalachian Valley. It is the best defined and most uniform of the three. In the southern part it coin_. . , *The Appala= cides with the belt of folded rocks g^S which forms the Coosa Valley of c arac er' Georgia and Alabama and the Great Valley of East Tennessee and Virginia. Throughout the central and northern portions the eastern side only is marked by great valleys such as the Shenandoah Valley of Virginia, the Cumberland Valley of Maryland and Pennsylvania, and the Lebanon Valley of northeastern Pennsylvania the western side being a succession of ridges alternating with narrow valleys. This division varies in width from 40 to 125 miles. It is sharply outlined on the southeast, by the Appalachian Mountains and on the northwest by the Cumberland Plateau and the Allegheny Mountains. Its rocks are almost wholly sedimentary and in large measure calcareous. The strata, which must originally have been relief tonrack , , . ° . character. nearly horizontal, now intersect the surface at various angles and in narrow belts. The surface differs with the outcrop of different kinds of rock, so that sharp ridges and narrow valleys of great length follow the narrow belts of hard and soft rock. Owing to the large amount of calcareous rock brought up on the steep folds of this division, its surface is more readily worn down by streams and is lower and less broken than that of the divisions on either side. The eastern division of the province embraces the Appalachian Mountains, a system which is made up of many minor ranges and TheAppaIa_ which, under various local names, ex2K"; *££££" tends from southern New York to ranges* central Alabama. Some of its prominent parts are the South Mountain of Pennsylvania, the Blue Ridge and Catoctin Mountain of Maryland and Virginia, the Great Smoky Mountains of Tennessee and North Carolina, and the Cohutta Mountains of Georgia. Many of the rocks of this division are more or less crystalNature of the line, being either sediments which have rocksbeen changed to slates and schists by varying degrees of metamorphism, or igneous rocks, such as granite and diabase, which have solidified from a molten condition. The western division of the Appalachian province embraces the Cumberland Plateau and the Allegheny Mountains and the lowlands The Cumber= of Tennessee, Kentucky, and Ohio. Its lan̂ ^^ northwestern boundary is indefinite, but may be regarded as an arbitrary line coinciding with the Mississippi River as far up as Cairo, and then crossing the States of Illinois and Indiana. Its eastern boundary is sharply defined along the Appalachian Valley by the Allegheny front and the Cumberland escarpment. The rocks of this division are almost entirely of sedimentary origin and remain very nearly horizontal. The character of the surface, which is dependent on the character and attitude of the rocks, is that of a plateau more or less completely worn down. In the southern half of the province the Itg varied plateau is sometimes extensive and toP°graPhyperfectly flat, but it is oftener much divided by streams into large or small areas with flat tops. In West Virginia and portions of Pennsylvania" the plateau is sharply cut by streams, leaving in relief irregularly rounded knobs and ridges which bear but little resemblance to the original surface. The western portion of the plateau has been completely removed by erosion, and the surface is now comparatively low and level, or rolling. Altitude of the Appalachian province. The Appalachian province as a whole is broadly dome-shaped, its surface rising from an altitude of about 500 feet along the eastern margin to the crest of the Appalachian Mountains, and thence descending westward to about the same altitude on the Ohio and Mississippi rivers. Each division of the province shows one or more culminating points. Thus the Appalachian Mountains rise gradually from less ...... .' . O J Altitudes of than 1000 feet in Alabama to more chlanttnthan 6600 feet in western North Carolina. From this culminating point they decrease to between 4000 and 3000 feet in southern Virginia, rise to 4000 feet in central Virginia, and descend to 2000 or 1500 feet on the MarylandPennsylvania line. The Appalachian Valley shows a uniform increase in altitude from 500 feet or less in Alabama to 900 feet in the vicinity of Altitudes of Chattanooga. 2000 feet at the Tennesthe Appasia= chian Vallev seeVirginia line, and 2600 or 2700 feet at its culminating point, on the divide between the New and Tennessee rivers. From this point it descends to 2200 feet in the valley of New River, 1500 to 1000 feet in the James River basin, and 1000 to 500 feet in the Potomac basin, remaining about the same through Pennsylvania. These figures represent the average elevation of the valley surface, below which the stream channels are sunk from 50 to 250 feet, and above which the valley ridges rise from 500 to 2000 feet. The plateau, or western, division increases in altitude from 500 feet at the southern edge of the province to 1500 feet in northern Alabama, 2000 feet in central Tennessee, and 3500 feet in southeastern Kentucky. It is between 3000 and 4000 feet in West Virginia, and decreases to about 2000 feet in Pennsylvania. From its greatest altitude, along the eastern edge, the plateau slopes gradually westward, although it is generally separated from the interior lowlands by an abrupt escarpment. Drainage of the Appalachian province. The drainage of the province is in part eastward to the Atlantic, in part southward to the _. .. ' L Direction of Gulf, and in part westward to the Misoutflowsissippi. All of the western, or plateau, division of the province, except a small portion in Pennsylvania and another in Alabama, is drained by streams flowing westward to the Ohio. The northern portion of the eastern, or Appalachian Mountain, division is drained eastward to the Atlantic, while all of the area south of New River except the eastern slope is drained westward by tributaries of the Tennessee River or southward by tributaries of the Coosa. The position of the streams in the Appalachian Valley is dependent upon the geologic structure. In general they flow in courses which . o J Arrangement for long distances are parallel to the ofstreamssides of the Great Valley, following the lesser valleys along the outcrops of the softer rocks. These longitudinal streams empty into a number of larger, transverse rivers, which cross one or the other of the barriers limiting the valley. Jn the northern portion of the province they form the Delaware, Susquehanna, Potomac, James, and Roanoke rivers, each of which passes through the Appalachian Mountains in a narrow gap and flows eastward to the sea. In the central portion of the province, in Kentucky and Virginia, these longitudinal streams form the New (or Kanawha) River, which flows westward in a deep, narrow gorge through the Cumberland Plateau into the Ohio River. From New River southward to northern Georgia the Great Valley is drained by tributaries of the Tennessee River, which at Chattanooga leaves the broad valley and, entering a gorge through the plateau, runs westward to the Ohio. South of Chattanooga the streams flow directly to the Gulf of Mexico. Local geography of the Wai^tburg quadrangle. Within the limits of the Wartburg quadrangle only one geographic division, the Cumberland Plateau, appears. By far the greater part of this area consists of a well-developed plateau, but along its eastern and southern border irregular mountains rise to considerable heights above the plateau level. The drainage of the region is tributary to several river systems. The southern half of the area is drained through the . ' . ° Local river Obed and Emory rivers into the Tensystemsnessee River, the northern half through the South Fork of the Cumberland River into the Ohio, and the western edge by Obey River into the Cumberland River and the Ohio. The South Fork of the Cumberland River. and the Obey River head within the quadrangle. The streams of the mountains fall rapidly from their sources to a level of 1400 or 1500 feet, from which altitude they descend less rapidly to 800 or 900 feet at the borders of this quadrangle and near the edges of the plateau. The streams of the plateau head upon its surface at 1500 to 1800 feet above the sea, fall rapidly near their headwaters, and have many sluggish stretches in their lower courses. Their valleys are deep, and the slopes rise continuously from narrow bottoms to the divides. Through most of the plateau the large streams are sunk in deep, narrow channels, which are lined by high cliffs and are from 300 to 1000 feet below the level of the plateau. In this region the topography varies