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. 
