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CAPE COD GEOLOGY 



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POST-GLACIAL OR RECENT CHANGES 



Cape Cod more than any other part of southeastern New England shows 

 the changes due to the ravages of the sea since the glacial epoch. As the changes 

 in the inland part of the area are insignificant compared with those that occurred 

 along the shore, they will be considered later. 



Changes in the Shore Line 



The east coast of Cape Cod is somewhat protected from the attack of the 

 sea by the great shoal known as Georges Bank, which lies southeast and east 

 of the Cape at distances of 80 to 140 nautical miles. This shoal breaks the force 

 of seas running from the east and southeast, but the Cape is exposed to the full 

 force of northeast storms, which have a fetch of more than 250 nautical miles 

 measured from the southern prong of Nova Scotia, and of a much greater fetch 

 measured from the Bay of Fundy. Since glacial time considerable land has been 

 lost on the east coast and the outline of the coast has been reduced to its present 

 form, in which irregularities have been cut away to form a graceful curve. This 

 cutting has been accompanied by the building up of great hooks and spits of 

 wave-washed sand encumbered by dunes formed by the wind that sweeps the 

 beaches. The submarine contours off the east coast of the Cape conform to the 

 curvature of the shore line down to the depth of 24 fathoms. Those that lie at 

 greater depths, south of Nauset Light, do not show like conformity. The curva- 

 ture of the coast line increases westward as the exposure of the shore to the 

 northeast storms increases, until at Highland Light the coast trends about 50° 

 west of north. It turns within two miles to 70° W. on the bar that extends the 

 Cape toward its northernmost reach, where it recurves to the southwest toward 

 Race Point. The contour of the sea bottom below a depth of about 30 fathoms 

 suggests that the original trend of the Cape did not differ much from its present 

 trend from High Head as far south as Chatham. 



As the submerged ridge between the north end of the Cape and Stellwagen 

 Bank lies at a depth of about 24 fathoms, the land probably did not extend out 

 beyond that depth, although the shore line may have been shifted inward by 

 the erosion of the bottom or outward by deposition. At and off the headland 

 of the Cape an old shore line lies 5 miles from the present shore. The nature of 

 this headland of interlobate morainal material indicates that along the old 

 eastern shore line there was an embankment or ice-contact slope along which 

 the surface of the Wellfleet and Eastham plains dropped to a lower level, such 



