The Lava Plain of the North 



105 



Lava Beds Polished by Glaciers 



Glaciers have done much to shape the features of this dis- 

 trict. Rock tarns, U-shaped valleys, perched blocks, roches 

 moutonnees, abound. Steep-sided, dome-shaped or truncated 

 pyramidal peaks rise in profusion in the northeast corner of 

 Lassen Peak Park, chief among them Lassen Peak itself, Eagle 

 Peak, Bumpass and White mountains, and the Chaos Crags. In 

 general these domes represent the products of the latest volcanic 

 activity in the Lassen Peak region. 



Lava Rocks Become Soils 



I 



By and large the great lava plain of Northern California is 

 a vast desert of rock. Rugged, broken, angular fragments of 



Photo by Univ. of Calif, Courtesy U. S. Bureau of Soils 



FIG. 31. Rough surface of basaltic lava flow two miles north of Look- 

 out, Modoc County. 



rock, originally poured from earth's interior in a molten con- 

 dition, and flowing as a thick viscous liquid over great areas, or 

 thrown from craters in terrific explosions as so-called volcanic 

 ash or cinders, slowly cooled into crystalline hard rocks, or 

 deposited in wide areas of scoriaceous tufa and pumice, such a 

 land surface does not offer the most inviting field for the growth 



