Geology from a Motor Car 407 



whence the Sacramento River enters upon its task of overcom- 

 ing the lava which flowed from Shasta down its original valley. 

 Here may be seen a section of more than 300 feet of lava and 

 tuffs (fragmentary lava dust) . 



Timberline Camp at Summit of 

 Mount Shasta 



From Sisson a good trail leads to Timberline Camp, 6 miles. 

 If a day can be spared, and // the tourist has good lungs, heart 

 and muscles, the climb to the summit of Mount Shasta, 6,000 

 feet higher, may be undertaken. (Note the /'/ in the above sen- 

 tence! ) . The summit is 14,3 80 feet, not quite as high as Mount 

 Whitney. The view from the summit is said to be unsur- 

 passed by that from any peak in the Cascade Range. A sul- 

 phurous fumerole (a vent from which hot gases are emitted) 

 is at the summit, and another on the northern slope. During 

 an eruption of the volcano lava poured down the south side 

 and flowed for 50 miles down the valley in which the Sacra- 

 mento River now struggles to keep its "right-of-way." 



Lava Fragments Pushed Down Mountain 

 Side by Glacier 



Along the west foot of the mountain, from Sisson to Weed, 

 fragments of lava which have been brought down the mountain 

 side by a glacier that has now disappeared, are piled in hum- 

 mocky hills, between and among which are ponds and swamps 

 such as occur commonly in moraines formed by glaciers. On 

 the right (east) near Summit (elevation 3,905 feet) is a lava 

 cone known as Sugar Loaf. It is made up of solid andesite lava. 

 When emitted it was in the form of a thick pasty lava which 

 bulged up over the volcanic vent without explosion, and cooled 

 forming the conical peak. It rises to a height of 6,250 feet. 



Near Sisson is a large spring which is spoken of as the source 

 of Sacramento River. Small streams in the foothills of the 



