PART II THE SURFACE AND UNDERGROUND WATER BY WM. BULLOCK CLARK, EDWARD B. MATHEWS PREPARED IN CO-OPERATION WITH THE U. S. GEOLOGICAL SURVEY THE SURFACE AND UNDERGROUND WATER BY WM. BULLOCK CLARK, EDWARD B. MATHEWS, PHYSIOGRAPHY The State of Maryland forms a portion of the Atlantic slope which stretches from the crest of the Alleghanies to the sea, and is divided into three more or less sharply defined regions known as the Coastal Plain, the Piedmont Plateau, and the Appalachian Region. These three districts follow the Atlantic border of the United States in three belts of varying width from New England southward to the Gulf of Mexico. Maryland is, therefore, closely related in its physiographic features to the states which lie to the north and south of it, while its central location on the Atlantic border renders the Maryland section perhaps the most characteristic in this broad tract. In crossing the three districts from the ocean border, the country rises at first gradually and then more rapidly until it culminates in the highlands of the western portion of the state. The physical features of a country to no inconsiderable degree determine the pursuits of its inhabitants, and these indirectly affect their social, political, and financial welfare. The residents of mountainous districts have their peculiar occupations, while those of the lowlands find their employment in other ways. In regions bordering the sea or inland bodies of water still other means of livelihood are sought by the people. The character of the soil and its adaptability to particular crops also become important factors, while the underlying rocks, not only by their influence upon the conditions of life already described, but also by their inherent • wealth in mineral resources, still further influence the well-being of the community. It becomes necessary, therefore, to know something of the physical features of a country, or a state, if one would understand its past history or indicate the lines of its future prosperity. · THE COASTAL PLAIN The Coastal Plain is the name applied to the low and partially submerged surface of varying width extending from Cape Cod southward through Florida, bounded by the Piedmont Plateau on the west and the margin of the continental shelf on the east. The line of demarkation between the Coastal Plain and the Piedmont Plateau is sinuous and illdefined, the one passing over into the other oftentimes with insensible topographic gradations, although the origin of the two districts is quite different. A convenient, although somewhat arbitrary, boundary between the two regions is furnished in Maryland and Delaware by the Baltimore and Ohio Railroad in its extension to Washington. The eastern limit of the Coastal Plain is at the edge of the continental shelf. In the vicinity of Maryland this is located about 100 miles off shore at a depth of 100 fathoms beneath the surface of the Atlantic Ocean. It is in reality the submerged border of the North American continent, which extends seaward with a gently-sloping surface to the 100-fathom line. At this point there is a rapid descent to a depth of 3000 fathoms where the continental rise gives place to the oceanic abyss. THE DIVISIONS OF THE COASTAL PLAIN The Coastal Plain, therefore, falls naturally into two divisions, a submerged or submarine division and an emerged or subaerial division. The seashore is the boundary line which separates them. This line of demarkation, although apparently fixed, is in reality very changeable, for during the geologic ages which are past it has migrated back and forth across the Coastal Plain, at one time occupying a position well over on the Piedmont Plateau, and at another far out to sea. At the present time there is reason to believe that the sea is encroaching on the land by the slow subsidence of the latter, but a few generations of men is too short a period in which to measure this change. The subaerial division is itself separable in Maryland into the Eastern Shore and the Western Shore. These terms, although first introduced to designate the land masses on either side of Chesapeake Bay, are in reality expressive of a fundamental contrast in the topography of the Coastal Plain. This difference gives rise to an Eastern Shore and a Western FIG. 72.-MAP SHOWING THE PHYSIOGRAPHIC PROVINCES. Shore type of topography. Chesapeake Bay and Elk River separate the two. But fragments of the Eastern Shore type are found along the margin of the Western Shore at intervals as far south as Herring Bay, and again from Point Lookout northwestward along the margin of the Potomac River. On the other hand, an outlier of the Western Shore type of topography is found at Grays Hill in Cecil County at the northern margin of the Eastern Shore. The Eastern Shore type of topography consists of low, flat, and almost featureless plains, while the Western Shore is a rolling upland, attaining four times the elevation of the former and resembling the topography of the Piedmont Plateau much more than |