THE GLACIERS OF MT. RAINIER 



661 



Crater Lake. The lakelets observed in 

 the neighboring valley heads all of 

 which are abandoned cirques are of 

 similar origin. 



It is a significant fact that the empty 

 cirques about the Mother Mountains lie 

 at elevations ranging between 4,500 and 

 6,00 feet; that is, on an average 5,000 

 feet lower than the cirques on Mount 

 Rainier which now produce glaciers. 

 Evidently the snow line in glacial times 

 lay at a much lower level than it does 

 today, and the ice mantle of Mount 

 Rainier expanded not merely by the 

 forward lengthening of its ice tongues 

 but by the birth of numerous new 

 glaciers about the mountain's foot. The 

 large size of the empty cirques and can- 

 yons, moreover, leads one to infer that 

 many of these new glaciers far exceeded in 

 volume the ice streams descending the 

 volcano's sides. The latter, it is true, 

 increased considerably in thickness dur- 

 ing glacial times, but not in proportion 

 to the growth of the low-level glaciers. 

 Nor is this surprising in view of the 

 heavy snowfalls occuring on the moun- 

 tain's lower slopes. There is good 

 reason to believe, moreover, that the 

 cool glacial climate resulted in a general 

 lowering of the zone of heaviest snowfall. 

 It probably was depressed to levels be- 

 tween 4,000 and 6,000 feet. Not only 

 the cirque glaciers about the Mother 

 Mountains, but all the neighboring ice 

 streams of the glacial epoch originated 

 within this zone, as is indicated by the 

 altitudes of the cirques throughout the 

 adjoining portions of the Cascade Range. 

 By their confluence these ice bodies pro- 

 duced a great system of glaciers that 

 filled all the valleys of this mountain belt 

 and even protruded beyond its western 

 front. 



To these extensive valley glaciers the 

 ice flows of Mount Rainier stood in the 

 relation of mere tributaries. They 

 descended from regions of rather scant 

 snowfall, for the peak in those days of 

 frigid climate rose some 10,000 feet 

 above the zone of heaviest snowfall, into 

 atmospheric strata of relative dryness. 

 It may well be, indeed, that it carried 

 then but little more snow upon its 

 summit than it does today. 



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