56 THE PHYSIOGHAPIIY OF ST. MARY'S COUNTY 



Topographic Description. 

 Maryland may be considered as divisible into three grand physio- 

 graphic provinces which are, beginning with the eastern, the Coastal 

 Phiin, the Piedmont Plateau, and the Appalachian Eegion. The Coastal 

 Plain extends from the outer margin of the continental shelf westward to 

 the edge of the Piedmont Plateau, or approximately to the position occu- 

 pied by the Baltimore & Ohio Eailroad as it crosses the State from 

 Delaware to Washington. The relief throughout the Coastal Plain re- 

 gion is low and its western margin slowly rises to an altitude of about 

 300 to 400 feet as it merges with the Piedmont Plateau. The Pied- 

 mont Plateau extends from the western margin of the Coastal Plain to 

 the eastern boundary of the Appalachian region. It is considerably 

 higher than the Coastal Plain, attaining in Carroll County an altitude 

 of over 800 feet, and has been deeply dissected by the river valleys which 

 cross it. Its western border merges with the Appalachian region at 

 Catoctin Mountain. The Appalachian region occupies the remainder of 

 the State. It consists of parallel ridges of rugged mountains over 3000 

 feet in height, separated by broad valleys and crossed by narrow water 

 gaps. Many of the counties of Maryland present a . variety of topo- 

 graphic features resulting from the fact that they lie in more than one 

 of these regions. St. Mary's County, however, lies entirely within the 

 Coastal Plain and it is due to this fact that its scenery, although pictur- 

 esque and in a measure diversified, does not present the variety which 

 is found in some of the other counties of Maryland. In a report on 

 Cecil County ^ recently iniblished, two types of the topographic character- 

 istics of the Coastal Plain were defined. They were described in the 

 following words : " In Cecil County the Coastal Plain contains two con- 

 trasted types of topography. One type is a flat, low, featureless plain, 

 and the other is a rolling upland attaining four times the elevation of 

 the former and resembling the topography of the Piedmont Plateau 

 more than that typical of the Coastal Plain. Elk Kiver is the dividing 

 line between these two types of topography. On the east side of it is 



' Cecil County. Maryland Geological Survey, 1902 



