206 GUIDEBOOK OF THE WESTERIST UNITED STATES. 



range. The depth to which the modern river canyons have been 



accom 



considered 



velopment 



amount 



't- The old plateau surface has been 

 from being destroyed. The stream 

 in the ''youtlifuV stages of their 

 1 ^'maturity/' perhaps thousands of 

 5en them will have been worn down 

 streams themselves, instead of roar- 



ing through rocky canyons, will ghde in leisurely meanders through 

 broad green meadows. The canyons are thus evidence of the geologic 

 recency of the elevation of the Sierra Nevada. 



skirts 



gradually 



This part of 



the railroad follows closely'the bottom of the lava that caps the ridge, 



■ma 



tion. The main cap rock of the ridge is andesitic tuff-breccia. Under 

 this in places is some lighter-colored rhyolite tuflf. For a while there 



are few distant outlooks. 



most 



sm 



growth, the original forest having been destroyed long ago by lumber- 

 ing or by forest fires. At Forebay (milepost 162), 



which 



yon to the distant level sky line. W 



view 



charact 



com 



of fragmental volcanic materials ranging from fine tuff to coarse 

 blocks of lava. (See PL XLVIII, i?,) Just beyond Midas (elevation 

 4,142 feet, milepost 161) appears a seemindv almost sbppr dron into 



below the track. 



American 



:iin 



largely to the fact that they are capped ^vdth volcanic rocks, chiefly 

 andesite tuff-breccia, is again clearly apparent. Beyond Gorge sta- 



th 



known 



also as Lovers Leap. The canyon is narrow here because it cuts 



the slates above it. 



am 



thward thi'oug 



niue gap in the ricige into a smaJl upland valley. The rock in the 

 gap Itself IS white rhyohte tuff, but above and below the gap the 

 railroad crosses some serpentine fan altered m^cmp^inn .Vr.o^,.c r-^nt^ 



part 



this part of the Sierra slope. 



along 



