which flows the Shenandoah River, Virginia, is known as the Shenandoah peneplain. A generalized profile in a northwest and southeast direction through a portion of the Appalachians is shown in the following diagram, which will serve to make more definite the description just given. The highest summits in the diagram represent portions of the Schooley peneplain; if the depressions could be refilled the surface of the great plateau formed by the elevation of this plain would be restored. The bottoms of the broad depressions represent the Shenandoah peneplain, which is sharply trenched by the modern river channels.
[2]Also known as the "Kittatinny peneplain," but the name used above has priority.
Fig. 17.—Generalized east-and-west profile showing relation of peneplains.
The Appalachians thus furnish not only a typical example of a mountain system produced by the folding and upheaval of the rocks of the earth's crust, accompanied in many localities by breaks or faults and overthrusts, but also preserve the records of two well-characterized peneplains. The long and varied history of the range has been in part interpreted by geologists from the character of the rocks, the fossils they contain, and the structure that has been impressed upon them; but some of the most instructive chapters are recorded in the topography, and their study has led to a highly creditable advance in methods of geographical research.
The Appalachian Mountains when first seen by Europeans were clothed throughout with a varied and beautiful forest consisting largely of hardwood trees. Nowhere do they invade the region of perpetual snow, and glaciers are absent. These statements are true also for all of the mountains on the eastern side of the continent to the south of Hudson Strait.
The Appalachians abound in beautiful scenery, but, except about a few of the very highest domes and ridges, have
little of the stern ruggedness which is typical of truly great mountains. Their countless valleys are now mostly cleared of their primitive forests and under cultivation. To a large extent also even the steep hillsides are tilled. The larger trees which formerly grew on the mountains have nearly all been felled, and where the land is not suitable for cultivation their place is taken by a dense second growth. Under the mild, humid climate that prevails, more especially from the vicinity of the Susquehanna River southward, the rocks are deeply disintegrated and decayed, and even steep mountainsides are mantled with soil and rock débris. It is the excess of disintegration and decay over erosion which gives to the mountains their usually flowing outlines and pleasingly picturesque rather than rugged scenery. The valleys still retain much of the material washed from the uplands, and are deeply floored with rich soil. The characteristic colours of this decayed rock-waste are many shades of red and yellow, which harmonize in a most artistic manner with the prevailing green of the plant-covered uplands and abandoned fields. These red and yellow soils, particularly about the bases of the higher summits of the southern Appalachians, afford abundant crops of cotton, corn (maize), and tobacco.
The Mountains of New England, New York, New Brunswick, etc.—The picturesque Berkshire Hills, in the western portion of Massachusetts, have rounded and flowing outlines and a generally subdued relief. The more prominent of these greatly eroded remnants of what was once a mountain range rise but 2,000 to 3,500 feet above the sea. No satisfactory boundary between these hills of gneiss, schist, and allied metamorphic rocks, and the others of the same general character in the neighbouring portions of New York and New Jersey, has been determined. So far as the relief is concerned, and so far also as the complex geological history has been deciphered, there seems no good reason for separating the Berkshire Hills from the Appalachian Mountains. It is convenient, however, to consider the Appalachians as terminating at the Hudson. The Berkshire Hills when traced northward merge with a