PLEISTOCENE GEOLOGY OF THE SAWATCH RANGE 705 



terraces to the older drift seem to be analogous, and point strongly 

 to the glacio-fluvial origin of both sets of terraces. 



CHANGES IN DRAINAGE AFFECTED BY GLACIATION 



Two clear cases of changes in drainage due to glaciation were 

 worked out in this region. The Eagle River, one and a half miles 

 below Pando (Fig. 2, a) enters a narrow rock gorge, about three miles 



Fig. 2. — Sketch map of an area of about seventeen square miles near Pando. 



a represents the head of the postglacial rock gorge entered by Eagle River a mile below Pando; b 

 indicates the position of the probable preglacial course of the Eagle River. The dotted line represents 

 the position of the moraine of the glacier which came down Horaestake Creek. 



long. In this gorge, the stream, although of considerable size, has 

 cut itself only a shallow valley, which is clearly very young. Just 

 west of the point where the stream leaves its broad valley for the nar- 

 row gorge, there is a low, broad, col (Fig. 2,h), filled with drift, beyond 

 which Hes Homestake Creek, which has, from this point down, a much 

 larger valley than its size would require. 



