THE LIFE FEATURES OF THE COASTAL PLAIN 

 AND THE PIEDMONT 



SPENCER TROTTER 



Delivered April 9, 1917 



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THE REGION of Old Appalachia is probably one of the most ancient 

 land surfaces on the globe. Unlike many other areas, it appears never 

 to have been wholly submerged, but to have existed at first as a series 

 of detached island masses to the south and east of the great primordial Archean 

 of Labrador. As such it became the nucleus of later successive stages of land- 

 building that ultimately developed into the eastern portion of the North Amer- 

 ican continent. The weathering of its rock surface suppHed the material for 

 future land growth, and we now behold it worn down to its roots — a basal com- 

 plex of crystalline schist, granite, and gneiss. It is this old land surface that 

 today we call New England and, south of the Hudson Valley, the Piedmont 

 Plateau. The hundred-fathom line marks the edge of the continental plat- 

 form, and Appalachia may at one time or another have extended to this boun- 

 dary as an uphfted land surface, but for long periods of time it was submerged 

 and overlaid with sediments. Not until the later Tertiary deposits of sand 

 and gravel had accumulated to a considerable thickness was there an up- 

 warping movement that added a more or less permanent land area along the 

 southeastern border of the continent — the present Atlantic Coastal Plain. 



The physical features of these two adjoining land surfaces, the one of 

 ancient archean rocks, the other of the more recent Tertiary sands, are strongly 

 contrasted. At the present time the Coastal Plain of New England is, for the 

 most part, under the sea, granitic rocks forming the rugged coast line of the 

 land. From Cape Cod southward there is an increasingly wider and wider 

 area of coastal plain country until it merges with the Gulf lowland of like age 

 and formation. South of the Hudson the line of demarcation between the 

 Coastal Plain and the Piedmont becomes very apparent. The former presents 

 a generally fiat expanse of lowland, gravel, sand, and clay deposits, through 

 which the smaller streams have everywhere cut trenches on their way to join 

 the alluvial reaches of rivers that flow slowly seaward into tidal estuaries. 



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