PHYSICAL AND CLIMATIC SETTING 9 



with the upbuilding of the California of today than 

 surface agencies. It has been estimated that more 

 than half the land surface is of sedimentary sub- 

 stances. These include sandstones, shales and clays 

 of inorganic origin. The ancient waters of the 

 State, however, not only received and held fast these 

 scourings from the uplifts by stream, wind and gla- 

 ciers but supported a submarine growth of coral and 

 other lime-collecting organisms which gave limestones 

 literally thousands of feet in depth in some places. 

 The other chief component of the California sur- 

 face is of igneous origin. Less than one-half is 

 counted as being chiefly granitic (of which the Sierra 

 Nevada Mountains are a great irregular block of 

 granite), and lava flows productive of other rocks 

 and of volcanic ash. This line of creation is still 

 active in the recent out-pours of Mt. Lassen in north- 

 ern California, although the adjacent higher cone of 

 Mt. Shasta has not been active. 



In the possession of animal and plant life in geo- 

 logic time, the vestiges do not indicate that Cali- 

 fornia was particularly rich as compared with other 

 parts of the earth's surface, although in special in- 

 terest of some of the forms, and in the unique man- 

 ner in which the remains have been preserved, the 

 paleontology of California is very notable from a 

 scientific point of view. 



Owing to the multiplicity of geologic agencies and 

 the diversity of materials they produced and trans- 

 ported, not only within narrow geographical limits 

 but by superposition, because of alternating eleva- 



