MARYLAND GEOLOCilCAL SURVEY 137 



stances it is coutiiiued along the Patuxcnt itself by the foreland areas 

 already described. In fact the foreland is merely a similar terrace 

 formed along the Patuxent. 



From an agricultural standpoint the facts of physical geography are 

 of greatest interest in connection with the results produced on the 

 land surface. As a brief summary of the effects upon Calvert County 

 it may be stated, that the continual action of storm waves along the 

 bay shore will steadily though slowly cut away the land area at 

 exposed ])oints and deposit this material as sand bars and mud-fiats 

 where sheltered positions or cross currents cause a slack water area. 

 The equally continuous erosion performed by the head-waters of all 

 streams will wear away the upland surface and transport the derived 

 materials to tide water estuaries where they will be deposited, forming 

 mud-flats and marshes and causing a general shallowing of all adjoining 

 water courses, except where tide and stream currents are strong enough 

 to keep the channels open. 



Thus upland areas, subject to rapid rain wash, must be carefully 

 tended, while the wearing away of the Bay shore and the silting up 

 of bays along the Patuxent are inevitable and affect both agriculture and 

 agricultural transportation. 



THE GEOLOGY. 



Calvert County lies entirely within the Coastal Plain division of 

 Maryland, and the geologic formations which enter into its structure are 

 composed of unconsolidated clays, sands, ami gravels, together with 

 remains of organic life like the diatomaceous earths and the marl bods. 

 These materials, though unconsolidated, form rocks in the geologic 

 sense, since they conRtituto an intooral ]iart of the earth's crust. They 

 are still passing through the earlier stages of rot-k formation, and neither 

 pressure nor cementation has progressed far enough to bind the inco- 

 herent masses into firm, solid rocks. 



All geologic formations of sedimentary origin are divided and sub- 

 divided into various groupings according to their age, as determined by 



the character of the fossil organisms entombed in them, and according 

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