60 Adventures in Scenery 



but was not spread out upon the surface. It was upheaved by 

 great forces deep in the earth. The surface formations were 

 not broken through, but were uplifted by the great mass in- 

 truded from below. (This upheaved mass is known to geolo- 

 gists as a batholith, from two Greek words meaning a deep lake 

 of rock.) The surface formations which were uplifted have 

 been removed over wide areas by erosion, so that the cooled 

 molten rock now appears at the surface as granite rock. Much 

 of the rugged Sierra Nevada Range is this granodiorite rock. 

 The upheaved granitic rock, with the metamorphosed ancient 

 sedimentary rocks into which the granite was intruded, make 

 up the bed-rock or "basement complex" which underlies most 

 of the formations of California. 



The Geologic Record 



Turning to the record of geological formations: the great 

 geologic era following the primitive Archaean or Archaeozoic 

 was the Palaeozoic. The earliest period of the Palaeozoic era 

 was the Cambrian. The oldest of the sedimentary formations 

 in which definite remains of organic life, plants and animals, 

 have been found is the Cambrian. Cambrian rocks occur in 

 several areas of the State. So also rocks of Devonian and Car- 

 boniferous age are found. The definite geological history of 

 the State, however, begins mainly, or dates from, Triassic and 

 Jurassic, or Jura-Trias, time, which time marks the early stages 

 or beginning of the great Mesozoic era. 



At this time (beginning of the Mesozoic era) a profound 

 change in the conditions of the continent occurred. The Pa- 

 laeozoic era was very long. It was essentially a time of erosion 

 and sedimentation. The widespread formations of the Cam- 

 brian, Silurian, Devonian, and Carboniferous periods are but 

 slightly represented in California, which means that what is now 

 California was during this long time mostly above sea level, 

 and hence was being weathered and eroded. At the close of 

 the great Palaeozoic era a revolution which affected the conti- 



