Geology from a Motor Car 395 



Yuba River is a high ridge known as Signal Peak. This ridge 

 is composed of metamorphic slates of Triassic age. On the peak 

 a fire look-out station is maintained. The brown talus from 

 these slates is in marked contrast with the white granite which 

 outcrops over much of the summit region. Below Soda Springs 

 the valley of the south fork of Yuba River has been scoured by 

 glacier ice, its broad and smoothly rounded bottom worn into 

 the bare granite. Morainic material is scattered along the sides 

 of the valley in the form of boulders, irregular shaped stone 

 fragments, and gravel. 



Crossing Sierra Siimmit, Above 

 7,000 Feet 



For about two miles, nearing the summit, an upland 

 glacially-formed meadow is in a valley in the lower part of 

 which is Lake Van Norden. And here is the summit of the 

 Sierra Nevada Range. In a distance of less than 200 miles from 

 the ocean, and in about 100 miles from the edge of the Great 

 Central Valley of California, an elevation of more than 7,000 

 feet has been reached. The achievement of building a railroad 

 through a rough mountainous country from sea level to such 

 an elevation was a marvel of engineering construction. To 

 traverse this vast slope now, through the same land that was 

 crossed by the pioneer '49-ers with such danger and difficulty, 

 over hard-surfaced well paved highways, is another of the mar- 

 vels of modern times. 



The highway crosses the summit of the great range at an 

 elevation of 7,135 feet. The railroad cuts under the crest of 

 the range through a long tunnel at a level 123 feet lower. Here 

 is Donner Lake and Donner Pass, memorable for the terrible 

 tragedy of 1846. The highway is north of Donner Lake. 

 Donner Lake State Monument, where is recorded the date and 

 the facts of the suffering and tragic fate of the emigrant party, 

 is south of the lake. 



