PRINCE WILLIAM SOUND 173 



Two facts indicate that these mountains are geologically 

 young. The first is paleontologic. Russell found, in 

 one of the lower spurs of Mount St. Elias, a fossil marine 

 fauna composed wholly of forms which still inhabit the 

 coastal waters of Alaska. 1 These show that the last great 

 elevation of the mountain range is recent, as measured in 

 terms of biologic evolution. The other evidence of youth 

 is found in the great height of the mountains. As pointed 

 out by Powell, the degradation of mountains is so rapid 

 that only young mountains can be lofty. The St. Elias 

 Range is not only lofty but steep, and its rate of waste 

 must be rapid. The fact that it is lofty despite rapid 

 waste indicates that its waste is compensated by growth. 



In view of the differences in general geologic history, 

 there need be no surprise if the Pleistocene history of the 

 district of high mountains should differ from the Pleisto- 

 cene history of the districts of Alexander Archipelago 

 and Prince William Sound. In view of the loftiness of 

 the mountains, it is rather probable than otherwise that 

 uplift has occurred since the epoch of chief Pleistocene 

 glaciation. It is therefore inferred with some confidence 

 that the discordance between the sea-level indicated by 

 the rampart moraines and the present sea-level has been 

 brought about chiefly by local uplift of the land. 



If this view is correct, the disturbed marine clays ob- 

 served near La Perouse Glacier (fig. 22) may be con- 

 nected with a fault zone of Pleistocene or post-Pleistocene 

 date. 



PRINCE WILLIAM SOUND 



Prince William Sound is a very irregular bay, opening 

 southward (pi. xm). All about it are mountains, the 

 higher being massed at the north, and others encroaching 

 on its area as promontories and islands. The largest islands, 



1 National Geographic Mag., vol. 3, pp. 171-172, 1891. 



