:maryi.a>;d geological sukvey 1 1 



that extend inland to the eastern border of the Piedmont PLateau are 

 the most prominent characteristics of the Coastal Plain of Maryland. 

 On the eastern side of Chesapeake Bay these streams are occupied by 

 tide-water almost to their heads while the tributary streams are also 

 very little above tide, consequently stream erosion has accomplished 

 very little work and the country is in the main extremely flat. On 

 the western shore different conditions prevail as here the larger 

 streams are estuaries up as far as the 'Tall-line," but the heads of 

 the tributaries lie a few hundred feet above tide and hence they have 

 been able to do considerable erosion. For this reason the topography 

 of the western shore Coastal Plain is much more diversified than 

 that of the Eastern Shore, Prince George's County exhibiting a topog- 

 raphy of the western-shore type. 



The elevations in Prince George's County range from the level of 

 tide-water in the estuaries to slightly more than 420 feet above sea 

 level. The highest ]ioint is a small hill near the Montgomery County 

 line a short distance southwest of Laurel. At Tenley(town) in the 

 District of Columbia a hill rises to the height of 400 feet. Both of 

 these hills are found in the Piedmont Plateau province, although the 

 capping of the hills is Pleistocene sand and gravel. From the Pied- 

 mont Plateau border the stream divides slope gently to the southeast, 

 where they have an average elevation of about 140 feet. If the 

 stream valleys were filled up the result would be a gently sloping 

 country with an average of about 7 feet per mile, a grade so low as 

 to be practically unnoticeable, thus causing the region to appear as 

 a flat monotonous plain. It is in this very gently sloping country 

 that the Potomac and Patuxent rivers and their tributary streams 

 have cut their drainage cliannels and have by so doing developed a 

 somewhat diversified topography. 



The ease with which different strata or formations are worn away 

 by erosion is usually the most important factor in the determination 

 of the topographical configuration of any region. It is this which is 

 mainly responsible for the direction of the streams and for the rela- 

 tive elevations, especially in a region which has not been subjected 

 to erogenic movements and where, as a result, the strata are approxi- 

 mately horizontal. 



