The Geologic Map 93 



phosed (i.e., changed by heat and pressure), sandstones becom- 

 ing quartzites; muds, silt and clay transformed to slates; lime- 

 stones to marbles. The rock strata were crumpled, bent, 

 folded, and contorted, and intermixed with the intruded molten 

 lava. All slowly cooled and form what is now spoken of as the 

 basement complex on which later formations have been laid 

 down as the region sank beneath the sea. These rocks are rep- 

 resented on the State areal geology map as Plutonic rocks. 

 (Geologic Map of California, by Olaf P. Jenkins.) 



State Geologic Map Shows Plutonic 

 and Volcanic Rocks 



Plutonic rocks are shown widely distributed over the State. 

 The basement complex of granitic rocks, together with quartz- 

 ites, schists, slates, and marbles, extends far south forming the 

 foundation of the Coast Ranges. The rocks of the basement 

 complex meet and join with a similar batholith or underground 

 lake of molten granitic rocks in the San Emigdio Mountains and 

 form the basement complex of the Sierra Nevada. Much of 

 the basement complex of granitic rocks, quartzites, slates, 

 schists, and marbles has been covered by the sea and buried 

 beneath later sedimentary formations, only to be again uplifted 

 and the formations removed by erosion. Thus on the State 

 geologic map plutonic rocks are shown over vast areas of the 

 State. 



Another widely distributed surface rock is shown on the 

 geologic map under the designation V, meaning volcanic. Vol- 

 canic as distinguished from plutonic means that the rocks were 

 poured out from volcanic vents upon the surface, or thrown 

 out in violent explosions as volcanic ash. Northern California 

 is a vast lava field. Mount Shasta and Lassen Peak are out- 

 standing volcanoes. Many other volcanoes, not only in the 

 north but along the Sierra Range far into southern California, 

 have emitted vast millions of tons of lava which now covers 

 wide areas. The geologic age, or time of outpouring, of many 



