CAPE COD GEOLOGY 



267 



A chain of ice-block holes that are occupied by lakelets extends from the 

 plain south of the Falmouth moraine into the higher ground of the moraine. 

 Long Pond, in Falmouth, is a conspicuous example of this entanglement of 

 remnant ice blocks of the Nantucket substage with the ice front of the Falmouth 

 or second Wisconsin substage. The ice blocks in Spectacle and Lawrence ponds, 

 near Farmersville, appear to have been pushed into by the Falmouth ice, as does 

 also the block that gave rise to Great Pond, in Barnstable. The Mill Ponds in 

 Brewster occupy a similar position, and numerous smaller ponds lie along the 

 southern edge of the moraine, showing that the Falmouth frontal lobe deployed 

 into a region that was still occupied by scattered masses of the Nantucket 

 ice sheet. 



Upham l has pointed out that the abundant supply of gravel and sand about 

 the ice blocks which gave rise to glacial lakelets of this kind must have come 

 from drift that lay well up in the ice sheet. 



Masses of ice stood in the open ice-block holes south of the Falmouth 

 moraine during the second ice advance of the Wisconsin stage and lasted without 

 much change until the ice of that stage had disappeared; otherwise the outwash 

 of sand and gravel from the Falmouth ice would have obliterated the depres- 

 sions. The duration of the second or Falmouth substage was brief as compared 

 with the duration of the remnants of the Nantucket ice. 



On the south side of the Cape, in addition to the ice block holes of the 

 Nantucket substage, there are a few hills of drift that rise above the level of 

 the plain. Falmouth Heights is such a hill. It borders on Vineyard Sound, is 

 about 40 feet high, and is evidently older than the low sand plain that surrounds 

 it on the landward side. The bluff, which is now in part revetted by a sea wall, 

 shows coarse cobbly drift and much glacial sand. Small boulders occur in the 

 talus and on the beach. The deposit has all the internal characters of a torrential 

 kame. Its form suggests that it was overrun by the Wisconsin ice 'sheet when 

 that sheet advanced to Marthas Vineyard. It is early Wisconsin or older. 



Two small till-covered areas lie at the entrance to Lewis Bay, south of 

 Hyannis. The hill that rises above 60 feet at Hyannis Port appears to have 

 been strewn with small erratics, more of which are now gathered in stone fences. 

 The southwestern trend of the hill, parallel to that at Falmouth Heights, agrees 

 with the trend of the buried channels of the plain and indicates that ice moved 

 southwestward across this area during the Nantucket substage of glaciation. 

 Squaw Island, just back of Hyannis Point, is also a low mound of till. Boulders 



1 Upham, Warren, Walden, Cochituatc, and other lakes enclosed by modified drift, Proc. Boston 

 Soc. Nat. Hist., 25,' 1891, pp. 228-242. 



