167 157 147 137 127 117 107 97 87 77 67 57 47 



K.nsan Drift 



Drift 

 Imoan Drift 



d later drift sheet 

 Existing glaciers and ice sheet 



MAP OF THE GLACIATED AREA OF NORTH AMERICA 

 From Upham's map as modified by Leverett, United States Geological Survey 



