THE GEOLOGICAL HISTORY OF NEW YORK STATE Og 
In conclusion we may say that while many comparatively small, 
local features were produced by ice erosion, the major topographic 
features of the State were practically unaffected by ice erosion 
due to the passage of the great ice sheet. 
Ice deposits. The vast amount of debris transported by the great 
ice sheet wasycarried either on its surface, or frozen within it, or 
pushed along under it. It was very heterogeneous material ranging 
from the finest clay through sand and gravel, to boulders of many 
tons weight. The deposition of these materials, as we now see 
them, took place during both the advance and retreat of the ice, but 
chiefly during its retreat. Most of the deposits made during the 
ice advance were obliterated by ice erosion, while those formed 
during the ice retreat have been left intact except for the small 
amount of postglacial erosion. .The general term applied to all 
deposits of glacial origin is “ drift,’ this term having been given 
at the time when they were regarded as flood deposits. Drift 
deposits cover practically all of New York State except where bare 
rock is actually exposed, and its thickness is very variable, ranging 
_ from nothing to several hundred feet. 
The ice sheet could advance only when the rate of motion was 
greater than the rate of melting of the ice front and vice versa in 
the case of retreat. Thus it is true, though seemingly paradoxical, 
to assert that the ice was constantly flowing southward even while 
the ice front was retreating northward. Whenever, during the 
great general retreat, the ice front remained stationary because the 
forward motion of the ice was just counterbalanced by the melting, 
all the ice reaching the margin of the glacier dropped its load to 
build up a terminal moraine. Such a moraine is a more or less 
distinct range of low hills and depressions consisting of very 
heterogeneous and generally unstratified debris, though at times 
waters emerging from the ice caused stratification. The depres- 
sions are usually called kettle holes. The so-called great terminal 
moraine marks the southernmost limit of the ice sheet, and is 
wonderfully well shown by the ridge of low irregular hills extend- 
ing the whole length of Long Island (see plate 12). It is also 
clearly traceable across northern New Jersey and Pennsylvania and 
passes through southern Cattaraugus county in New York. 
Terminal moraines farther northward are generally not so long 
nor sharply defined, the one of perhaps most prominence having 
been traced from Herkimer through Oriskany Falls, Cortland, 
Watkins, Bath, Portageville, Dayton, and Jamestown. Moraines, 
either terminal or lateral, are often locally very prominently 
developed. 
