CAPE COD GEOLOGY 



61 



like that broader and deeper opening between Gay Head and Block Island. A 

 curve drawn from the boulder shoal southwest of No Mans Land to Montauk, 

 where the frontal moraine reappears, indicates that the axis may have been 

 prolonged as much as five or ten miles south of the south coast of Block Island 

 in the area between that island and No Mans Land. 



A striking feature of the morainal topography of the outer islands is their 

 freedom from alteration by wave action above the present sea level. Except for 

 long-continued atmospheric weathering, which is particularly noticeable in some 

 of the granitic boulders, the surface has been but little altered, even by fresh- water 

 streams. A strong contrast with this retention of the forms impressed upon the 

 surface by the glacier and the streams that flowed over the outwash plain is seen 

 in the present destructive work of the sea in cutting away and trimming the edges 

 of the land. 



Falmouth Moraine 



The second Wisconsin terminal or frontal moraine is best developed in the 

 town of Falmouth. It skirts the shores of Buzzard's Bay and the south side of 

 the Cape Cod Canal, where it forms a huge outwash fan of sand and minor beds 

 of gravel, sprinkled with thousands of granitic boulders. Southwest and east of 

 the apex of the frontal fan, which coincides in position with the interlobate angle 

 of the ice sheet, the mounds of the frontal moraine rise above the level of the 

 stratified drift and form rather typical morainal topography, as at Woods Hole 

 and on the Elizabeth Islands; but farther east, along the frontal of the Cape Cod 

 Bay lobe, the beds of outwashed sand continue to form a large part of the frontal 

 deposits. They were more or less overrun by the ice and are pitted with large 

 holes, which were occupied by blocks of ice left over from the Nantucket substage. 



The deposits of stratified material in this moraine dwindle eastward, toward 

 Orleans, whence the ice front appears to have turned southeastward to form a 

 lobe whose axis, like that in the earlier Nantucket substage, lay along the South 

 Channel. A weak interlobate axis is thus traceable from Tom Never's Head, on 

 Nantucket, through the Orleans-Nauset section of Cape Cod, north of which the 

 forearm of the cape lies in the interlobate axis between the South Channel or 

 offshore lobe and the Cape Cod Bay lobe. 



In the interlobate tract in the northern part of Falmouth the features of the 

 Nantucket substage at Vineyard Haven are repeated and continued northward 

 over the Plymouth quadrangle by the great mass of gravel and sand in the 

 Plymouth woods, in which Manomet Hill is prominent. 



A remarkable fact in the history of the three lobes in this part of the glaciated 



