201 
luropean ice sheet has been determined. This is about 8700 
years. The probable time that has elapsed since the last ice sheet 
stood on Long Island is thus found to be about 35,000 years. His- 
torically seen, this is very long ago, geologically seen, it was only 
part 
yesterday. 
The Quaternary Period 
These four or five glaciations with intervening interglacial 
epochs belong to the Quaternary Period which still prevails. To- 
gether the glaciations form the Quaternary Ice Age or the Pleisto- 
cene. The time of waning of the last ice sheets is the late-glacial 
age, and the time since the practical disappearance of the ice sheets 
is called the postglacial age. 
Will there be a new glaciation in the future? Since there seem 
to have been four or five glaciations separated by epochs as warm 
as or warmer than the present, it is not out of place to ask whether 
or not another glaciation is to be expected in the future. Positive 
answer cannot be given, but it is very possible that in some 50,000 
Fic. 21. Kettlehole in the Ronkonkoma moraine at Culloden Point, Long 
Island, September, 1920. The amount of water in the hole varies with the 
seas (Photo by Barrington Moore. From Brooklyn Botanic Garden 
icy) 
vee s, Vol. 
