PHYSICAL AND CLIMATIC SETTING 27 



from other clays in being more or less strewn with 

 bowlders, probably carried in on floating masses of 

 ice. Probably the lakes were not deep. There were 

 islands of glacial till formed from the mass of rock 

 debris left directly by the ice as it melted. 



Long Island, which has a core of Cretaceous sedi- 

 ments, was also covered by the ice and has a rough 

 moraine along the northern shore and another diag- 

 onally through the central part from Brooklyn to 

 Montauk Point. On the south side the surface was 

 depressed below the sea during the retreat of the 

 glacial ice and during that period broad plains of 

 sand, sandy loam and clay were formed from the 

 glacial outwash of New England. 



The net result of the glacial incursion was to de- 

 face the preglacial surface features, rub off the sharp 

 eminences, unevenly fill up many of the valleys and 

 hollows with till and sediments and to carve out 

 others perhaps a little more deeply. On the plains 

 area south of Lake Ontario the till or rock flour 

 from the grinding action of the ice was left in 

 rounded bunches that in some places conform to the 

 general rock surface and in others make tadpole 

 shaped hills, called drumlins. These latter are 

 widely distributed through the middle of the State 

 but are especially abundant west of Syracuse and 

 north of Auburn and Geneva. Wherever the general 

 surface was moderately flat, irregular undulations 

 were produced in which lakes and ponds were formed, 

 many of which are now marked by swamp areas that 



