MARYLAND GEOLOGICAL SURVEY 



tion it maintains beyond the limits of the area nnder discussion, 

 though it does finally resume its southeastern course, cutting across 

 the Tertiary strata to Chesapeake Bay. 



TOPOGRAPHIC FEATURES. 



Prince George's County as a whole exhibits five general topo- 

 graphic features, which are usually very distinct. These vary 

 greatly in the amount of surface that they occupy, but the most 

 noticeable distinction is that they lie at different elevations. 



Tide Marshes. — The first of these topographic features to be 

 described consists of the tide marshes found in the valleys of most 

 of the larger estuaries, particularly of Patuxent and Anacostia rivers 

 and Piscataway Creek. These extend over a number of square miles 

 and lie at a level so low that the tides frequently submerge them in 

 part. The small streams that empty into many of the estuaries 

 meander through these marshes, which are rapidly encroaching on 

 them. These marshes are filled with a growth of sedges and other 

 marsh plants, which aid in filling up the depressions by serving as 

 obstructions to retain the mud carried in by streams and by furnish- 

 ing a perennial accumulation of vegetable debris. 



Lafayette Plain. — The Lafayette plain is the highest of the plains 

 developed Mdthin the Coastal Plain province. It has a considerable 

 extent in this county southeast of Anacostia, forming the divide 

 between the valley of Patuxent River on the east and the basin of 

 Potomac River on the west. Throughout this region the margin of 

 the Lafayette plain has been extensively removed by stream action, 

 but the central portions have been practically undisturbed. 



Sunderland Plain. — The Sunderland plain lies at a higher eleva- 

 tion than the Wicomico and extends from about 100 feet to about 200 

 feet above sea level. It is usually separated from the Wicomico 

 plain by an escarpment, and in most places another escarpment marks 

 its contact with the next plain above. The escarpment separating 

 the Wicomico from the Sunderland plain is one of the most striking 

 and constant topographic features in the Coastal Plain of IMaryland. 



