104 Adventures in Scenery 



a grand scale. A few of the craters are more than a mile in 

 diameter. In the Lassen Peak region, and farther north in the 

 Cascade Range, the lava was generally of a viscous nature. 

 Being too stiff to flow far the lava accumulated about the craters 

 and formed large cones. One of the lava flows that continued 

 farthest from its source in the Cascade Range came from the 

 southern slope of Mount Shasta, and descended the canyon of 

 Sacramento River for 50 miles. The lavas in the eastern part 

 of this great field, extending through the Columbia, Deschutes, 

 and Snake valleys, were less viscous (more liquid) and flowed 

 more freely. They spread in thin sheets following the winding 

 valleys and surrounding isolated hills as islands in a lake. The 

 average thickness of the lava in this vast field has been estimated 

 to be thousands of feet. 



The California lava field extends from Susan River to Pit 

 River and the Oregon line, and eastward to the Modoc lava 

 beds, and beyond. It is densely wooded with conifers, and 

 mantled in places by a thick growth of Manzanita, while over 

 most of the region the volcanic rocks are obscured by a bouldery 

 cover of glacial debris. Small but well defined morainic ridges 

 occur, and where the bed-rock protrudes it is generally striated 

 and finely polished by glacial scour. Three well preserved 

 cones, Hat Mountain, Fairfield Peak, and Crater Butte, rise con- 

 spicuously above the general level, each about 500 feet high and 

 half a mile in diameter. Four outstanding volcanoes in the 

 plateau region east of Lassen Peak are Prospect, Raker and 

 Harkness peaks, and Red Mountain. Of these three the largest, 

 Prospect peak, has a diameter of four miles and rises 2,000 feet 

 above the surrounding country. Its slopes are almost perfectly 

 symmetrical. The other three are so slightly affected by ero- 

 sion that a cinder cone is still preserved on the summit of each. 

 The lavas to the east are among the oldest in the Lassen Peak 

 district and were deeply eroded by streams before glaciers cov- 

 ered the region with ice. 



