CLACIAL DKI'OSITS 



159 



Tin- moraines ;ii>out the lower end of a glaciated mountain valley. 

 Bloody Canyon, Cal. (U. S. Gcol. Surv.) 



margins of a glacier is much the same as beneath its terminus 

 (Fig. 163). 



Types of Moraines 



The terminal moraine. The thick accumulation of drift made 

 at the cud of a glacier or at the edge of an ice sheet, especially where 

 its end or edge is stationary or nearly so for a long time, is the 

 t.crtniinil moraine. Terminal moraines of ice caps are of more im- 

 portance, relatively, than those of valley glaciers, for streams are 

 more effective in destroying the moraines of the latter. The topog- 

 raphy of terminal moraines is rather distinctive, as illustrated by 

 l-'ig. 1 68. 



The ground moraine. When a glacier disappears, all its debris 

 is deposited. All drift deposited beneath the body of the ice, and 

 all deposited from its base during dissolution, constitutes the ground 

 moraine. The thickness of the ground moraine is notably unequal. 

 In general, it is thicker toward the terminus of the glacier and 

 thinner toward its source, but considerable portions of a glacier's 

 bed may be left without debris when the ice melts. As a rule, the 

 ground moraine is thinner than the terminal moraine, and less irreg- 

 ularly disposed. The ground moraines of valley glaciers are rela- 

 tively unimportant as compared with those of ice-caps, since condi- 

 tions for erosion under the body of a valley glacier are, on the 

 average, better than under an ice-sheet, while those for deposition 



