58 THE PHYSIOGRAPHY OF ST. MARY's COUNTY 



its turn gently rises toward the interior until at a height of about 75 

 or 80 feet it is terminated by a second scarp some 20 to 30 feet in height, 

 which blends at its upper edge with tlie rolling surface of the Iiighest 

 and oldest terrace. The latter is the main divide of the county, although 

 not the oldest terrace. It has suffered greatly from erosion, especially 

 along its borders, where it no longer has a plain but a rolling topography. 

 This terrace in its turn rises gradually toward the northwest. At a 

 height of about 180 feet it is abruptly terminated by a third scarp, which 

 rises 20 feet to the surface of the oldest and highest terrace of the 

 series. This terrace, which is present in the vicinity of Charlotte Hall, 

 is but slightly represented in St. Mary's County. To the northwest in 

 Charles and Prince George's counties it has a much more extensive 

 development and remnants of it are found scattered along the eastern 

 slope of the Piedmont Plateau from Washington northeastward through 

 Maryland, Delaware, and Pennsylvania to the Delaware River. It also 

 is present in Virginia and southward. In the vicinity of Charlotte Hall 

 this terrace is represented by a series of small outliers which bear the 

 same relation to the main body of the terrace as the islands scattered 

 along the Eastern Shore bear to the mainland behind. 



Throughout the southern half of St. ilary's County, especially in the 

 vicinity of Eidge, the inner margins of the three lower terraces do not 

 have the same elevations as in the region just described. The lowest 

 rises from tide to a height of about 10 feet. It is here abruptly ter- 

 minated by a scarp about 10 feet high. The next terrace slopes from 

 the top of this scarp to a height of about 45 feet. At this point the 

 second scarp rises and joins the terrace above at a height of about 60 

 feet. Although there is this difference in elevation between the three 

 lower terraces in the southern half of the county and the same terraces 

 in the northern half, the transition from one to the other is not abrupt 

 but gradual and one may trace them as they gently rise from Point 

 Lookout northward to the margin of the county. It would appear then 

 that there has been a slight tilting of the surface in southern St. ilary's 

 County. 



To the four terraces just described a fifth may be added, although it 



