288 H. L. FAlRCHILD POST-GLACIAL SUBMERGENCE OF LONG ISLANt> 



water and where in consequence the surface soils are more clayey and 

 more subject to erosion. Most of the creases or hollows along the inner 

 margin of the submerged belt have the characters produced by offshore 

 currents from streams and from tidal scour. They will be discussed later. 

 In summation of this chapter it may be said that the characters of the 

 plain are such as should be expected under the condition of partial sub- 

 mergence. 



Ttte SuBMAKiNi-; Plain 



^J'iie portion of the great plain which lay under the sea constitutes the 

 belt along tide water from Brooklyn city to Yaphank, about five or six 

 miles in width, and all of the east end of the island east of the meridian 

 of Yaphank except small areas of the higher moraine hills on the River- 

 head and Sag harbor quadrangles; also it apparently included an irreg- 

 ular, narrow strip on the Setauket quadrangle east of Smithtown, lying 

 between the two moraines, which the outwash from the second moraine 

 did not entirely fill. 



. The surface characters of the western sand-plains have already been 

 described in the two preceding chapters. The plains at Riverhead and 

 eastward are quite different, but they will be described in a later section 

 under the term kettle plains. 



The features pertaining to at least the west end of the island have not 

 been convincing to all observers of the submarine origin. In the genetic 

 interpretation of many geologic phenomena there enters a large psycho- 

 logic factor, and the mental prepossession or working theory is often the 

 determining force. "We see that for which we are looking." Physio- 

 graphic features seem to be especially susceptible to varied interpretation. 

 To the writer the very smooth, even sand-plains, considered alone, are 

 clear evidence of standing water. Other students with a different phil- 

 osophy of the history find subaerial origin for the plains. It would seem 

 as if an intensive study of the plains ought, by itself, to prove the genesis. 

 But it may be repeated that the evidences of Post-Glacial submergence 

 emphasized in this paper are quite independent of the argument from 

 the characters of the sand-plains. 



Proofs of Submergence 



evidence from the hudson valley 



Unless some unusual faulting or other very localized movement is 

 postulated for the Hudson Valley, it must be apparent that considerable 

 diastrophic movement of that valley must involve neighboring territory 



