QUATERNARY PERIOD ON THE WESTERN SIDE OF THE CONTINENT. 5(J5 



d. Many glaciers, whose tracks are still easily traced, at that time 

 ran down the steep mountain-slope into Lake Tahoe. The most con- 

 spicuous of these are three at the southern end, which, issuing from as 

 many canons, ran out on the level plain three or four miles, and into the 

 swollen waters of the lake to form icebergs. The beautiful lakelets and 

 the lake-like bay which form so conspicuous a feature of the scenery of 

 the southern end of the great lake, were partly scooped out by these 

 steeply descending glaciers, and partly dammed by the debris left when 

 they retired ; and the long, parallel ridges of earth and bowlders bor- 

 dering the lakelets and stretching down to the shores of the great lake, 

 are lateral moraines dropped on each side as the glaciers ran out into 

 the lake* (Fig. 934). 



During the Terrace epoch all these glaciers of the Sierra retreated, 

 leaving very distinct terminal moraines, where they rested awhile, be- 



Z. 1AHOE 



Fig. 934.— Diagram of Moraines at the Southern End of Lake Tahoe : a, Fallen-Leaf Lake ; b, Cas- 

 cade Lake ; c, Emerald Bay. 



hind which, drainage-waters accumulating, have formed beautiful little 

 lakes. Thus they have gone backward and upward, until they have 

 now mostly retired within the snow-fields which gave them birth. 



* American Journal of Science, vol. x, p. 126, 1875. 



