MARYLAND GEOLOGICAL SURVEY 69 



in other words, when the Lafayette terrace lies on the Piedmont Plateau 

 and the Sunderland terrace rests beneath it either on the Piedmont or 

 close to its eastern border, the descent from one surface to the other is 

 usually considerable and is accomplished by a topography of low, subdued, 

 rolling hills which pass down from the Lafayette terrace, occupying 

 successively lower and lower areas until they finally blend with the surface 

 of the Sunderland terrace beneath. This type of descent may be seen 

 along the eastern border of the Piedmont Plateau between Cecil county 

 and the District of Columbia (Fig. 3). The other type of descent is 

 found wherever the Lafayette and Sunderland terraces approach each 



lafayette for M at,on LAFAYETTE-SUNDERLAND SCARP 



PIEDMONT TYPE 



SUNDERLAND FORMATION 



Fig. 3. — Diagram showing Piedmont type of Lafayette-Sunderland scarp. 



other in the Coastal Plain. It may be described, as suggested above, as 

 being an abrupt descent resembling a wave-cut cliff which has since been 

 modified to a greater or less extent by subaerial erosion (Fig. 4). The 

 best localities for observing this type are to be found at Congress Heights 

 just south of the Anacostia river in the District of Columbia, near Bryan- 

 town and Aquasco in Charles county, and at Charlotte Hall in St. Mary's 

 county (Plate V). Two only of these localities need be described. At 

 Congress Heights the surface of the Lafayette terrace lies at an elevation 

 of about 260 feet and that of the Sunderland at about 200. The descent 

 between the two is accomplished by a cliff which is one of the most con- 

 spicuous features of the region and, in fact, of the entire Coastal Plain. 

 There, as one stands on the unbroken Sunderland surface facing east, he 



