i 5 8 



WORK OF SNOW AND ICE 



left there, for it is to be remembered that the ice is moving, though 

 its end is stationary. If a glacier moves forward 500 feet pel: year, 

 while its end is melted at the same rate, all the debris in the 500 

 feet of ice melted, is deposited, and all except that washed away 

 is deposited at and beneath the end of the glacier (Figs. 160-161). 

 If ice advances 500 feet per year and is melted back 600 feet in the 



Fig. 162. Illecillewaet Glacier; Glacier, British Columbia, 

 at the right of the ice records its diminution. 



A lateral moraine 



same time, all the debris carried by the 600 feet melted has been 

 deposited, and largely in the narrow zone (100 feet) from which the 

 ice has receded. If the end of a glacier advances 500 feet per year 

 while it is being melted but 400 feet, all the drift in the 400 feet 

 melted is deposited, chiefly at or beneath the immediate margin of 

 the ice. To the marginal and sub-marginal accumulations made 

 in this way, the material carried on the ice is added whenever 

 the ice is melted from beneath it. Deposition beneath the lateral 



