National Geographic : 1898 Jul
GEOGRAPHIC DEVELOPMENT OF and its surface has been carved into hill and vale, broad divide and narrow valley, by the action of running water. During the ages past it was a high plateau or mountain range, which was first canyoned and afterward carried away by the Potomac and neighboring rivers of eastern United States. The Coastal province is a broad lowland made up of sedi mentary formations. It extends from the capital to the coast, and thence as shallow sea-bottom for over a hundred miles into the Atlantic, ending in a steep slope toward the ocean-depths; and it stretches northward to New York and southward to the limits of the continent. Thus the Coastal plain is about half land and half sea-bottom. Through the land portion broad estuaries pass, bearing the waters of Potomac and other rivers to the sea; and in the bottoms of the estuaries and in the sea-bot toms beyond, certain channels have been revealed by soundings. The history of the development of the region may be read from the land-forms of the two provinces, and from the sedimentary formations or deposits of the Coastal plain. DEFINITIONS The student of geographic development takes note of (1) pro cesses or agencies, and (2) products. The chief agency concerned in making this region is water, and the chief processes are (a) erosion, and (b) transportation by running water, together with (c) deposition of the transported material in slack water; or, in more general terms, degradation and subsequent aggradation. When a considerable area of earth-crust rises in such manner as to transform smooth sea-bottom to dry land, certain changes are wrought on the surface: When the rains fall, a part of the water lies long on the level surface and forms marshes, but here and there rivulets form and flow down the gentle slopes toward the sea; the rivulets cut rills and, as the waters gather strength with increased volume, dig gullies; eventually the rills unite in streamlets and brooks, and the gullies expand into ravines and valleys; and in time streams and rivers are formed, each flowing in a gorge or valley of its own making. In this way the surface of the uplifted sea-bottom is carved into valley-systems, and the forms of the valleys determine the forms of the hills and divides by which they are bounded. It is in this way that the lands of the earth are sculptured; and the sculpture of running water produces a characteristic topography.