CAPE COD GEOLOGY 



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2. Deposition or erosion of a then more extensive tract and, after its surface 

 had been shaped by deposition or erosion, its dissection by streams flowing to 

 a base level that is now submerged. The heads of most of the stream valleys 

 then lay on a divide east of the present coast line. 



3. The Wisconsin ice sheet then advanced over this tract, filling depressions 

 with ice in the interlobate axis between the offshore South Channel lobe and the 

 Cape Cod Bay lobe. In the interlobate axis of two such lobes the motion of 

 the ice and its erosive power is at a minimum. 



As the glacier melted, masses of the ice were left here and there in low places, 

 and the spaces about them, between the ice and the hillsides, were filled with 

 gravel and sand and some of the older valleys were more or less blocked, so 

 that many of the depressions in this glacial field, where pre-Wisconsin glacial 

 deposits and valleys are partly masked by Wisconsin ice effects, are very complex. 



The "hollows" in this region are named and described in Blunt's American 

 Coast Pilot. 1 The first and northernmost of the "hollows," known as Dyer's 

 hollow, opens on the east coast of the Cape at a point 1| miles from the light- 

 house, at the clay pounds. No. 2, Harding's hollow, which is 1| miles south 

 of Dyer's hollow, is blocked by sand just north of Pamet River. No. 3 is at the 

 head of Pamet River, and No. 4, known as Brushy hollow, which is three-fourths 

 of a mile south of the head of Pamet hollow, is a narrow vale that runs into Pamet 

 hollow. No. 5, 3 miles south of Brush valley, known as Newcomb's hollow, 

 lies east of the head of Herring River, in Wellfleet, and is a quarter of a mile 

 wide. No. 6, which is half a mile south of Newcomb's hollow, is known as Pearce's 

 hollow. No. 7, Cohoon's hollow, is half a mile south of Pearce's hollow. No. 8, 

 Snow's hollow, is 2 miles south of Cahoon's hollow. No. 9 is Fresh Brook hollow, 

 the name Fresh Brook appearing on current maps. No. 10, Plumb valley, is 

 21 miles south of Fresh Brook, at a point just north of the Nauset Beacons on 

 the present map. These hollows afford opportunities for castaways on the 

 beach at the back of the Cape to reach places of refuge and the houses of the 

 inhabitants, so that they need not attempt to climb the steep sand and gravel 

 bluffs, which for long distances are unscalable. 



PLYMOUTH INTERLOBATE MORAINE 



As the retreating ice sheet in Cape Cod Bay melted and permitted the 

 drainage from the lobe lying east of Cape Cod to discharge westward into the 

 basin just vacated by the ice, so the lobe lying west of the Plymouth interlobate 



1 Blunt, Edmund M., The American Coast Pilot, 11th ed., pp. 71-74, 1827; New York, also 13th ed., 

 pp. 179-183, 1837. 



