CAPE COD GEOLOGY 



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into two portions. This valley looks large for the size of the island, but when 

 the possibility that two streams entered it from the western area is added to 

 the fact that it has been submerged, and the probability that glaciation widened 

 it, to say nothing of the results of wave work, it may reasonably be considered 

 the site of an ancient river. It must also be remembered that the Vineyard inter- 

 val was extremely long compared with the time that has elapsed since the 

 Wisconsin ice sheet disappeared. 



The valleys of the second group are more numerous than those of the 

 first. Beginning on the southwest, we may say that the depression occupied 

 by Menemsha Pond was perhaps originally connected with a drainage system 

 that has since been submerged. In the higher ground on the northeast there 

 are two small brooks : Roaring Brook and Howland's Brook. These have com- 

 paratively short and steep courses to the sea, and were once used for mill power. 

 There are several other smaller brooks between them and Paul Point. At James 

 Pond another old valley, which was described above as a kettle valley, extends 

 well back into the moraine. It is not now occupied by a stream, but it was 

 dammed by glacial deposits that hold the water in several small ponds. 



Chappaquonsett Pond probably represents a valley that is now submerged 

 and glaciated in its lower part and obliterated by outwash gravel in its upper 

 part. 



OUTWASH FEATURES 

 THE OUTWASH PLAIN 



South of the two moraines lies a great triangular outwash plain formed by 

 gravel carried out from the melting ice of the Wisconsin glacier. Its northwest 

 side runs south-southwest, its northeast side runs southwest, and its south side 

 runs east and west and is virtually the south shore. That it is a true outwash 

 plain is shown by its relations to the terminal moraines, by the ice contact slopes 

 along its northern side, by its even, gentle slope, by the channels that traverse 

 it, and by the structure of the gravel that composes it. 



ICE CONTACTS 



Ice-contact slopes are well displayed along the northern edge of the 

 outwash plain at a few places but elsewhere the plain merges into a morainal 

 surface or breaks down into stratified moraine. At places where the ice contact is 

 found there is a well-marked fosse containing no morainal features. At such 

 places the relations between the plain and the moraine are those shown in Fig- 

 ure 8a. Where there is no ice contact slope the relations are those shown in 

 Figure 8b. 



