82 GEOLOGY OF TONOPAH MINING DISTRICT, NEVADA. 



CONTINUANCE OF VOLCANIC EPOCH. 



Viewed in this or in other lights, there is small reason for believing that the 

 period of volcanism in this province is past. It rather appears that we are still in 

 it. The occurrence of recent almost undefaced basaltic craters at various points, 

 such as at Silver Peak (PI. XV, A), at Lake Mono, and in central Oregon, show 

 that the last eruptions occurred only a few hundred years ago, while the evidence of 

 enormous Pleistocene and recent elevation and subsidence, especially in the western 

 part of the region, near the Sierra Nevada," suggests the migrations of the molten 

 tide beneath the present crust. 



a Spun, J. E., op. cit., p. 247, 248; also Bull. U. S. Geol. Survey No. 208, pp. 110, 129, 209, 210, etc. 



