The American Cyclopædia (1879)/Appalachian Mountains

APPALACHIAN MOUNTAINS, the great range of mountains, called also the Alleghanies, which extends from that part of Canada lying between the New England states and the St. Lawrence river, through the whole length of Vermont, across the western part of Massachusetts and the middle Atlantic states, to the northern part of Alabama. The name Appalachian was given to the mountains hy the Spaniards under De Soto, who derived it from the neighboring Indians. The name Alleghany, given by the English settlers of the north, was received from the Indians, and supposed to mean endless. The White mountains of New Hampshire and the Adirondack mountains of New York are really outliers of this range, though separated from it by wide tracts of low elevation. In their Alpine forms and more metamorphic structure, they present also features somewhat different from those which are especially peculiar to the Appalachian range. The Catskills form a link of the main range. These groups will all be found described under their own names. Not including the lateral ranges, the greatest width of the Appalachian chain is about 100 m. This is in Pennsylvania and Maryland, about midway of its course. Its extreme length is about 1,300 m. At either end its termination is not well defined, the mountains sinking away and being lost in the hilly country that succeeds to them, and at the south its gneissoid and other ancient rocks gradually disappearing beneath the cretaceous formations of this region. In all their extent the Appalachian mountains are remarkable, not for their great elevation, nor for their striking peaks, nor for any feature that distinguishes one portion of them from the rest, but for a singular uniformity of outline, particularly of that which defines the summit of the ridges, as well as that which marks their direction. While varying little in height, the ridges pursue a remarkably straight course, sometimes hardly diverging from a straight line for a distance of 50 or 60 m., and one ridge succeeding beyond another, all continuing the same general course in parallel lines, like successive waves of the sea. As one curves round into a new direction, all curve with it. Thus the valleys between the ridges preserve a uniform width, and are as remarkable for their parallelism as are the hills which bound them. An able paper upon “The Physical Structure of the Appalachian Chain” was read before the American association of geologists and naturalists in 1842, by the Profs. Rogers, who were at the head of the geological surveys of Pennsylvania and Virginia, and who had extended their observations into the continuations of the chain N. and S. from these states. This paper is still the most complete treatise upon this subject. Prof. Guyot has also given much attention to the physical structure of these mountains, and made careful barometrical measurements of several of their highest summits, both near their northern and southern extremities.—The general course of the Alleghanies is that of the coast line opposite to them. The sea makes its nearest approach to them at the mouth of the Hudson river, which is only 50 m. from the passage of this river through the Highlands. Thence as far S. as Cape Hatteras, the width of the Atlantic slope gradually increases, till the space between the coast and the Blue Ridge is about 200 m.; and so it continues to the southern extremity of the mountains. This space is a hilly district, gradually becoming of higher elevation as it extends back from the coast. In New England its average height at the base of the mountains is about 500 ft. above the sea; in Pennsylvania, 300; in Virginia, 500; and further S. 1,200. From the mountains to the lowest falls of the streams over the edge of the granitic platform, this is for the most part a region of the lowest stratified, metamorphic, and granitic rocks. These lowest falls mark the head of navigation of the streams, and the descent to the lower and more level platform of the upper secondary and tertiary formations, which in the southern states stretch along the coast in a belt sometimes reaching 100 m. in width. The eastern ridges of the chain, rising from their elevated base, do not present the appearance of the height above the sea which they actually reach; and on their western slope; which stretches far away toward the Mississippi, their height is still more completely lost in the elevated and wide-spread plateau. Between Lake Champlain and Lake Ontario, this western table land is 1,500 ft. above the sea, and from it as a base rise the high summits of the Adirondack mountains. In Virginia and Tennessee, as observed by Prof. Guyot, the bottom of the valley W. of the Alleghanies is from 1,000 to 2,000 ft. above the sea, and beyond it for 100 m. W. extends a plateau of 1,500 to 2,000 ft. elevation, traversed by longitudinal ridges. All the cross sections from the eastern edge of the granite present first the slightly undulating profile of the Atlantic slope, which is succeeded by the sudden rise to the highest elevation, and this by the wave-like descent and ascent across the valleys and the ridges, and finally terminate in the gradual descent on the western table land. As first pointed out by Prof. Rogers, the same law is found to obtain in this chain and in the Jura mountains, of steepest general slopes toward the east; but of individual ridges the gentler slopes are toward the east, and the steepest inclinations toward the west. In the mid-region of the chain—in New Jersey, Pennsylvania, and Maryland—where the breadth is greatest, the height appears to be correspondingly diminished. The summits, valleys, and table land all reach here their least elevation. The highest summits are but little over 2,000 ft. above the sea. Still the barrier between the eastern and western waters is complete; and no clean cut through the range is anywhere found, excepting that of the Mohawk river in New York, the highest elevation of which is only 400 ft. above the sea. Toward the north and the south from this central portion, the plateau becomes more elevated, as well as the summits that rise up from it. In North Carolina, near the borders of Tennessee, and in the northern part of Buncombe county, the base of the Black mountains, which have been an especial subject of examination by Prof. Guyot, is found to extend from 100 to 150 m. in length, with an elevation of 2,000 ft. Above this many summits are found reaching more than 4,500 ft. higher, as the Black Dome, the height of which above the sea is 6,760 ft.; the Balsam Cone, 6,668; the Black Brother, 6,671; Cat-tail peak, 6,595; Hairy Bear, 6,597, &c. The great elevation of this group makes it the culminating point of the system. Mt. Washington in New Hampshire, though found by the measurement of Prof. Guyot to be but 6,288 ft. above the sea, which measurement differs only three feet from that made by the officers of the coast survey, appears much more elevated than the summits of the Black mountains, from its rising from a plateau of not half the height of the base of this group.—In the southern part of Pennsylvania other parallel ridges succeed to the Alleghany mountains: Negro mountain, Laurel hill, and Chestnut ridge, each a repetition of the other, at distances about 10 m. apart, and each occupying nearly as great a breadth as the valleys which separate them. The capping of their summits is the conglomerate rocks, which underlie the coal measures. These strata arch over the crests of the ridges, projecting in bold cliff's, and on each slope dipping beneath the coal measures, which in the valley hills attain their greatest thickness. Thus the same strata appear upon the summits, and in undulating lines pass beneath the valleys to reappear upon the crest of the next ridge, and so on till, dipping down the western slope of Chestnut ridge, the coal measures spread in nearly horizontal strata over the western portion of Pennsylvania, Maryland, and Virginia. Their lowermost layers reappear as they rise to the surface upon the other margin of the great coal basin, as far into Ohio as Zanesville, and thence along a line extending to the mouth of the Scioto. In the gentleness of the dips of the strata, this western slope presents a striking contrast to the highly disturbed stratification of the Atlantic slope. There the rock formations, nearer the disturbing causes which have elevated the mountains and metamorphosed the rocks of the most eastern ridges, are thrown into confused and intricate positions, and pressed into folds and wrinkles, the prevailing inclination of which is toward the southeast—as horizontal layers of heavy cloth, pressed laterally by irresistible force from one end of the pile, would be lifted into folds, whose general inclination, by the falling back of the arches, would be toward the direction where the force is applied. The direction of the line of force is that of the ridges themselves, or rather of the anticlinal and synclinal axes, the one being the crest of wave-like form into which the strata are thrown, and the other the trough. This, too, is the line of the great fissures, which, now filled with metallic ores, constitute the mineral veins of the chain. It is the line of the rents caused by the earthquakes of the present period; and it is regarded by the Profs. Rogers as the line along which the elevating force that lifted the mountains extended, moving onward at right angles to this line, with a wave-like motion, till the result was attained of placing the ridges in their present positions. Toward the southeast, whence the movement proceeded, the axes are crowded near together. Toward the northwest they are repeated at distances gradually increasing, till the undulations at last flatten out and die away in the horizontally stratified regions of the west. The straightness or regular curvature of these axes, and their parallelism in distinct groups, continued for distances sometimes amounting to over 100 m., without change in the stratification or topography, cannot fail to excite the astonishment of the geological observer. Among these axes are particularly noticed by the Profs. Rogers the straight axis of Montour's ridge in the Susquehanna region, which extends about 80 m.; the beautifully inflected axis of Jack's mountain, in the Potomac region, 90 m. long; and that of the Knobly mountain, nearly a continuation of the last named, itself 100 m. long. In S. W. Virginia, the straight axis of Clinch mountain is traced for more than 120 m.—The strata of the Appalachian system are all of marine or terrestrial origin. The fossils they contain are all of families belonging to the salt water, or plants of terrestrial growth. The latest or uppermost groups are those of the coal formation. Throughout the whole chain none of the stratified rocks belong to a later epoch. Their elevation, then, must have taken place previously to those periods, when the upper secondary rocks, that lap upon the extreme eastern border of the Appalachian formations, were deposited, and previously to those still later periods when the great deposits of tertiary marls, sandstones, and clays were produced, which cover the S. E. part of our country. These mountains are then of much older date than the Alps or the Andes, upon the high summits of both of which rest the rocks of these later formations, containing their characteristic marine fossils. Raised probably by many successive impulses exerted on the same lines (it may be after long intervals of rest), the rush of the retreating waters appears to have opened those gaps through the ridges, which constitute a peculiar and most interesting feature in the topography and scenery of these mountains, and which could not have been produced by the action of any existing streams. The same rush of waters, acting upon piles of strata of various degrees of hardness, and consequent capacities of resistance, impressed upon these the forms appropriate to these properties. This is seen in the sharp outline of single beds of sandstone, which project from the sides of the hill, around which they outcrop; and in the receding of the profile of the mountain against the beds of softer shales and slates. It is seen on a grander scale in the peculiar forms which each of the rock formations gives to the hills or mountains it composes, and which enables one to recognize it wherever met with by a glance at the topography.—The regular arrangement of the rock formations throughout all their foldings and undulations is rarely disturbed by any of those sudden breaks which are common in other countries, and which bring into contact, by the displacement of portions of the series, strata usually far separated from each other. These “faults,” however, are met with in several of the states, but particularly in S. W. Virginia, where they extend for about 100 m. in length, their course being the same as that of the anticlinal axes out of which they grow. They appear to have resulted from the lateral thrust toward the northwest of the folded piles of strata. They are observed, always beginning on the N. W. side of the anticlinal axes, in tracing these along their course, the strata on this side becoming steeper and steeper, till at last they are inverted, and dip toward the southeast. At this point the strata appear to have burst asunder along the line of greatest curvature, and the S. E. portion to have been lifted up, bringing its lower strata against the higher members on the other side of the line of fracture. The depth of this dislocation, or the extent of the displacement, increases toward the centre of the line of fault; and where the length of this line, as in the district under consideration, stretches along for 100 m. or more, it cannot appear disproportional that the vertical displacement should in its central portions amount to ¹⁄₂₀ of this distance; and that the lower groups of the Appalachian system, usually separated by intervening strata of four or five miles in thickness, should be brought in contact, so that the edges of one series abut against the edges of the other. Thus the lower limestones of the great valley of Virginia are seen in Montgomery county, and thence westward along the line of the Virginia and Tennessee railroad, in vertical position, with the strata of the far more elevated series containing coal beds dipping toward them, as if the more recent formations passed beneath these ancient groups. The thermal springs, which are of frequent occurrence along the Appalachian chain, and particularly so in Virginia, flow out almost universally on the lines of anticlinal axes, or of the faults. Their elevated temperature indicates the great depths from which they rise, and consequently that to which the folds and fractures of the stratification reach.—The geological formations of the Appalachian belt, comprising all the groups from the granite to the coal, are abundantly productive in the most important ores and minerals, which especially belong to these different formations. In the ancient granitic rocks which skirt the edge of the lower stratified formations, and sometimes spread out over broad areas, as in the mountainous region W. of Lake Champlain, in the highlands of New York and New Jersey, are found inexhaustible repositories of magnetic iron ores, which already are worked to great extent in connection with the valuable beds of hematite ores that are found conveniently near them, ranging from Canada to Alabama along the line of the great Appalachian valley. These beds occur in great depressions in the lower limestones and metamorphic slates of this range, and sometimes in veins in the same rocks, and are worked in every one of the states through which this passes, everywhere presenting the same peculiar features. They are frequently of extraordinary extent, and though worked in several instances for more than 100 years, the actual depth to which they reach, and their real nature, have never been fully explored. Together with the magnetic ores, they furnish the supplies for a very large proportion of all the iron manufactured in the United States; and the numerous bodies of them still untouched are a provision for still larger demands for generations to come. The value of these repositories can hardly be overestimated, particularly when considered in connection with the long extent of their range, not far back from the coast, and the enormous supplies of mineral coal that can be conveniently brought to effect their reduction. Far more valuable are they than the gold found in the granitic and metamorphic rocks of the eastern ranges, though this, judging from the production of certain localities in the southern states, would, if exposed by the great irregularities of the surface, like those of California, be found as rich and abundant as there. It is worked in alluvial deposits enriched from the auriferous veins; and these also contain ores of copper and lead, and occasionally of silver. These deposits and veins are met with in the valley of the Chaudière below Quebec, and are again seen in a few localities in Vermont; but their great development is on the eastern borders of the Appalachians S. of the Potomac. The copper ores met with in the rocks of the Appalachian system have never proved of great importance. They are found along the range of the talcose and micaceous slates of the Blue Ridge, as well as associated with the gold further toward the southeast. In Virginia these slates produce some workable beds of lead ore, and display occasionally attractive appearances of copper. In New Jersey the same range produces the remarkable red oxides of zinc associated with Franklinite, which are worked together, the one to produce the white zinc paint, and the other a superior quality of iron for the manufacture of steel. Further S. along the same belt are found, in the Lehigh valley and in Lancaster county, Pa., the valuable silicates and carbonates of zinc, called calamine, which are worked for the same purpose as the red oxides of New Jersey. Veins of lead ore are found in several of the formations; and in Wythe county in S. W. Virginia a mine in the great limestone formation has been worked with some interruptions for more than 100 years. These lead veins, however, of the lower members of the Appalachian system, have for the most part proved of little importance; indeed, throughout the range of the mountains none of the formations above the metamorphic rocks are rich in any other metallic ores than the hematites which are occasionally met with, the red fossiliferous iron ores of Formation No. V. of the Pennsylvanian survey, called in New York the Clinton group, and the argillaceous ores of the coal measures. No rock formation is more useful to man for the variety and value of its productions than the true coal formation. It furnishes the great supplies of anthracite and bituminous coal, beds of fire clay, and west of the Alleghany ridge abundant beds of limestone. Salt water is obtained by boring artesian wells to lower members of the series, and the brine flows up or is pumped up into the valleys, to be evaporated by the combustion of the coal found in the neighboring hills. In many localities, where the salt-bearing rocks approach the surface, the brine is more readily obtained in large quantities, and the coal is transported for its evaporation. The formations that furnish the salt also contain great beds of gypsum. Onondaga county in New York is famous for these productions, and in Washington county in S. W. Virginia solid beds of salt are struck in the midst of the most extensive plaster deposits.—From one extremity of their range to the other, the Alleghanies have furnished large supplies of the valuable white pine; and many of the less accessible districts of the belt still abound with it. Far toward the north, upon the better soils of the mountains, the hard-wood forests prevail—the fine sugar maple, of the curly and bird's-eye varieties, and the white birch. The ash and the beech also attain their highest state of perfection in the most fertile soil of these northern mountains. Upon the poorer lands, and along the ravines of the mountains, the “black growth” flourishes—the evergreens, as the different species of the pine family, the spruce, the hemlock, cedar, and balsam fir; and in the swamps, the hackmatack or larch. The varieties of the oak appear further S. upon the range, these and the chestnut taking the place of the maple, birch, and beech, and, to some extent, of the evergreens also. The large cherry tree, so valuable for its timber, is met with in Pennsylvania, scattered upon the mountains; in W. and S. W. Virginia it forms forests of itself. The white oak, the white poplar, the white and yellow pines, and the chestnut are the valuable forest trees of the mountains of Virginia. In some localities still further south, the dark growth of the conifer covers the summits, as found, for instance, by Prof. Guyot in the group in North Carolina named the Black mountains from the dark foliage of its balsam firs, spruce, and hemlock. Among the flowering shrubs, none are more beautiful than the varieties of kalmia, azalea, and rhododendron, which are found in the greatest profusion upon the slopes of the Alleghanies and along their watercourses, giving to the rough places of the mountains the rich colors of cultivated gardens.