GLACIAL AND POST-GLACIAL HISTORY 



441 



which is a terrace of coarse gravel on the south side of Breakneck 

 Mountain (35, Fig. 9) with an estimated elevation of 80 feet. 



The weight of evidence in this part of the Hudson indicates 

 that the ice protruded as a tongue down the valley, and that it was 

 influential in shaping the edge of the plateaus toward the Hudson. An 

 alternative hypothesis is that the ice retired in a northeasterly direc- 



FlG. 15. — Looking eastward from the bluffs north of Albany across the trench of 

 the Hudson, cut into the clay plain. 



tion; that the plateaus on the west side of the valley were made first 

 and had their east edge shaped by the ice-front; and that later those 

 on the east side of the valley were constructed and had their east 

 edge shaped by the ice. This alternative hypothesis, however, does 

 not explain the eastward-dipping layers of the plateaus on the east 

 side of the valley, nor does it explain the apparent lower elevation of 

 some parts of the terraces on the east side next to the valley wall. It 

 would explain successive undulations from lower levels near the 

 Hudson to higher levels away from the Hudson, such as are found 

 at Cold Spring (33, Fig. 9). 



