GLACIERS OF MOUNT RAINIER 



of the Cowlitz River, which, joining the Ohanapecosh, 

 forms the Cowlitz River proper, one of the largest 

 streams of the Cascade Range. For nearly a hundred 

 miles the Cowlitz River follows a southwesterly course, 

 finally emptying in the Columbia River a short dis- 

 tance below Portland, Oregon. 



The name Muddy Fork is a most apt one, for the 

 stream leaves the glacier heavily charged with debris 

 and mud, and while it gradually clears itself as it 

 proceeds over its gravelly bed, it is still turbid when 

 it reaches the Ohanapecosh. That stream is relatively 

 clear, for it heads in a glacier of small extent and little 

 eroding power, and consequently begins its career 

 with but a moderate load ; furthermore it receives on 

 its long circuitous course a number of tributaries from 

 the Cascade Range, all of them containing clear water. 



The name Muddy, however, might with equal ap- 

 propriateness be given to every one of the streams 

 flowing from the ice fields of Mount Rainier. So easily 

 disintegrated are the volcanic materials of which that 

 peak is composed, that the glaciers are enabled to erode 

 with great rapidity, even in their present shrunken 

 state. They consequently deliver to the streams vast 

 quantities of debris, much of it in the form of cobbles 

 and bowlders, but much of it also in the form of " rock 

 flour." 



A considerable proportion of a glacier's erosional 

 work is performed by abrasion or grinding, its bed 

 being scoured and grooved by the rock blocks and 

 smaller debris held by the passing ice. As a result 

 glacier streams ordinarily carry much finely com- 

 minuted rock, or rock flour, and this, because of its 

 fineness, remains long in suspension and imparts to 

 the water a distinctive color. In regions of light- 

 colored rocks the glacier streams have a characteristic 

 milky hue, which, as it fades out, passes over into a 

 delicate turquoise tint. But the lavas of Mount 

 Rainier produce for the most part dark-hued flour, and 



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