134 



MARGARET BRADLEY FULLER 



Tahosa Valley. The Estes Valley was the melting basin of this 

 whole system of glaciers, though the drift deposits left in the 

 glaciated area have been cleared out by long and active erosion of 

 the stream and ice tributaries, leaving a U-shaped valley as chief 

 evidence of its occupancy. Simultaneously ice gathered in the 

 valleys adjacent to Storm Peak and filled in the North Fork, 

 Cedar Park, and the Thompson Valley between Drake and Mont 

 Rose. 



Fig. 7. — Diagram to represent the suggested drainage systems which preceded 

 early Pleistocene glaciation of this area. 



When the Muggins Gulch outlet was filled with ice to the 9,000- 

 foot level, drainage traveled from Estes to Drake over the low 

 col and through the small tributaries. This outlet became more 

 important as an escape for all the waters from the upper Thompson 

 after the ice had melted from the lower altitudes of the Thompson 

 Valley east of Drake. On account of its lower elevation the ice 

 freed the area east of Drake while it may have lingered for some 

 time in the Estes Valley to the west. As a result, the drainage once 

 established along its present lines east of Estes rapidly cut down its 

 course below the 8,000-foot level, thus determining the upper canyon 



