TOPOGRAPHY OF THE PACIFIC COAST. 47 



surface of the Sierra Nevada has been deformed during this 

 uplift, and that the most noticeable deformation has been caused 

 by a subsidence of the portion adjoining the Great valley rela- 

 tively to the middle part of the range." 



Strono- evidence of the deformation is furnished by the dis- 

 tribution of the lone formation. As already shown, this forma- 

 tion was deposited about sea level. On Little Cow creek it now 

 occurs at an altitude of 3,400 feet, and on Bear creek about 4,000 

 feet above the sea, indicating conclusively that since the base- 

 level period the Lassen Peak region has been elevated at least 

 4,000 feet. There are indications that the elevation was still 

 o-reater to the southward about the northern end of the Sierra 

 Nevada, for between Mountain Meadows and Diamond Peak 

 opposite Susanville the auriferous gravels supposed to belong to 

 the estuarine lone formation rise from 5,000 to 7,000 feet. These 

 high gravels upon the northeastern block of the Sierra Nevada 

 have been displaced in a remarkable manner by the upheaval of 

 the range. The area occupied by them is about 10 X 16 miles 

 in extent. Although the gravels cover the larger part of this 

 area and are connected throughout, they do not appear over the 

 whole of it. There were a few small islands of older rocks 

 during at least the later portion of the gravel period, and at 

 some other places within the area the gravels have either been 

 washed away or covered up' by later volcanic flows. 



During the later part of the gravel period in that region, 

 after the effusion of the andesitic lavas, more or less well defined 

 beaches were formed around a series of volcanic islands upon 

 what is now the very crest of the range from Fredonia Pass 

 northeast of Mountain Meadows to Diamond Mountain. When 

 developed, these beaches must have been at the same level in a 

 body of standing water, but now they gradually rise to the south- 

 ward from about 5,000 feet near the northern end of Mountain 

 Meadows to 7,000 feet opposite Diamond Peak, and it is evident 

 not only that the northern end of the range has been elevated 

 but that the amount of elevation increased to the southward. 

 The general inclination of this body of gravels toward Lassen 



