Vol. 6] Rcid: The Geomorphogeny of the Sierra Nevada. 149 



Further, the fault-line or lines bounding Washoe Valley on the 

 east extend southerly through the Washoe Mountains into Eagle 

 Valley. East of these lines the old plateau surface is again at a 

 higher elevation, at least 6,000 feet. The north faces of both por- 

 tions of the south boundary of Washoe Valley are on the same 

 line of motion, and the fault limiting the Washoe Mountains on 

 the south is the same that extends westerly into the Sierra Ne- 

 vada. The low portion of the Washoe Mountains, standing be- 

 tween Washoe and Eagle valleys, and forming a connection be- 

 tween the Sierra Nevada and Virginia Range, appears to be a 

 faulted block that remained above the level of the adjoining ones 

 north and south. It is connected with the nearby hills of the 

 Sierra Nevada not only visibly, but also by its general struc- 

 tural and physiographic features. These are in the main evident 

 from the maps. Also, the closer relation of Lakeview Hill to the 

 Washoe Mountains than to the Sierra has been noted. But there 

 is one bond of continuity not yet discussed. The hills embraced 

 within the two-mile square southwest of Lakeview is physio- 

 graphically as well as structurally a prolongation of the Washoe 

 Mountains, and as such is quite distinct from the rest of the 

 Sierra hills adjacent. This square area southwest of Lakeview 

 is also a part of the badly faulted Carson topographic area and 

 contains the eastern section of the Tertiary River. All these 

 facts are reviewed at length to throw possible light upon the age 

 of the east-west faults south of Washoe Valley, and the forma- 

 tion of the Carson topographic area. 



From the facts already cited descriptive of the effects of the 

 second and lesser period of east-west faulting, it is obvious that 

 the southward facing hills bounding Washoe Valley on the south 

 are older than this last marked time of orogenic movements. Nor 

 is it probably of the same age as the first period of east-west 

 faulting. At this time the motion south of the main east-west 

 line through the south end of Washoe Lake was one of elevation 

 and eastward movement. This will be discussed more fully a 

 little later. This movement toward the east would produce com- 

 pression in that direction, assuming, as there is no reason for not 

 doing, that the Virginia Range was not moving simultaneously 

 and independently. But a triangular dropped block or graben 



