EXTINCT GLACIERS OF COLORADO 



By Junius Henderson 



Although it seems quite probable that the ancient glaciers which 

 have so profoundly modified the alpine regions of Colorado were coex- 

 istent with the great continental ice-sheet of the Glacial Epoch, which 

 buried the Upper Mississippi Valley beneath a thick mantle of glacial 

 drift, yet it can hardly be said that there is any direct, positive proof 

 of it; and, even if the glaciers were synchronous, they seem certainly 

 not to have been territorially connected. A glance at the geological 

 map will show that Colorado is not within the hmits of the continental 

 ice-sheet as indicated by the lateral and terminal moraines, and there 

 is abundant evidence that the mountain glaciers radiating from the 

 alpine regions covered only a comparatively small portion of the state. 

 There is no evidence of general glaciation, the greater part of the state 

 being free from recognizable glacial phenomena. If it should be con- 

 sidered settled that the ancient mountain glaciers of Montana were 

 connected with the continental glacier in point of time and space, it 

 would merely add to the probability, but not actually demonstrate, 

 that the same was true of the southern Rockies, for the glaciated areas 

 of Colorado were isolated, not only from each other, but from the more 

 northern areas, by wide stretches of unglaciated country. 



Cross and Howe say: "It is commonly believed by specialists that 

 the recognizable glaciation of the Colorado mountain region belongs 

 to the latest main stage of the Glacial Epoch known as the 'Wisconsin 

 Stage.' Evidence of more ancient stages has been observed in the 

 Wasatch and Uinta Mountains of Utah, and elsewhere, and it is thought 

 that an interval of great erosion preceded the Wisconsin stage. "^ 



The conclusion as to the stage is largely a matter of inference, rather 

 than direct evidence, but it is so reasonable as to force itself emphatically 

 upon the attention. 



Owing to the fact that mountain glaciers in cirques and valleys 



' Silverton Folio, No. 120, p. 24, Geol. Atlas, U. S. Geol. Sur. 



39 



