THE TERMINAL MORAINE OF THE PUGET SOUND 



GLACIER 



J. HARLEN BRETZ 



I. GENERAL CHARACTER OF THE COUNTRY SOUTH OF PUGET SOUND 



The region of Puget Sound, inclosed between the Olympic 

 and Cascade ranges, is a heavily drift-covered lowland. The drift 

 is deeply incised by broad valleys of meridional trend, some occu- 

 pied by arms of the Sound, some by lakes, and others by streams. 

 The summits of the plateaus and hills of drift accord in a general 

 level so that, seen from overlooking mountain peaks, the region 

 appears to be a vast plain, interrupted only by a few rock hills, 

 remnants of the preglacial topography rising above the drift. 



Immediately south of the Sound the drift assumes a different 

 facies. The trough valleys disappear and the plain becomes 

 continuous and is widely covered with gravel outwash. It is 

 still a part of the great Puget Sound drift plain. It is diversified 

 with morainic eminences occasionally, of a character different 

 from that of the drift hills lying between the valleys of Puget 

 Sound farther north. The most southerly extended of these hills 

 is a belt which constitutes a part of the terminal moraine of the 

 Puget Sound glacier. 



Beyond the southern portion of the Puget Sound depression 

 is an abrupt transition in the topography. Rock hills of pre- 

 glacial sculpture, lying beyond the limit of glaciation, begin here 

 and continue- southward past the Columbia. In western Washing- 

 ton no other such area of low rock surface occurs as must here 

 exist beneath the heavy drift mantle of Puget Sound. 



On the southeast, the area is overlooked by the magnificent 

 Tertiary volcano Rainier. On the south is a region of rock hills 

 bearing no group name. They are drained by the upper Des 

 Chutes and the Skookum Chuck rivers and have a maximum 

 altitude of about 2,000 feet. Farther west lie the Black Hills, 

 whose highest altitude is probably not greater than 2,000 feet. 



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