244 Adventures in Scenery 



pushed their heads backward up each side of the ridge, but 

 because those leading to the ocean have a greater fall their 

 heads have pushed back more rapidly than those of the north 

 slope. As a result the axis of the ridge or anticline is consider- 

 ably south of the dividing line between the north and south 

 streams. The ridges between the streams are all of nearly the 

 same height. 



The Range an Arched Ridge of 

 Former Sea Sediments 



What is now the Santa Monica Range of mountains was at 

 one time a flat plain. This plain had been for a long time sea 

 bottom, and on it were deposited sediments which became solidi- 

 fied as shale. Later, due to uplift of the region these sediments 

 became dry land. They are now the slates and schists which 

 are among the oldest rocks of the range. They are thought to 

 be of Triassic age, but no fossils have been found in them and 

 hence the age cannot be exactly determined. 



A Batholith of Molten Rock Forced 

 under a Roof of Sea Sediments 



At a later time, thought to be Jurassic (the next great geo- 

 logic period later than Triassic) , a vast up welling of molten 

 rock (technically called "magma") occurred. The great 

 molten mass was intruded under and into the shale formation 

 as a great batholith. The shale, several thousand feet in thick- 

 ness, which had been deposited on the old sea bottom and ele- 

 vated to become dry land, was uplifted, forming a roof or 

 covering over the intruded mass of molten rock. Heat and 

 pressure of the intruding magma transformed the shales by 

 metamorphism to slates and schists. The liquid molten rock 

 that was forced up under and into the shale formation slowly 

 cooled during the lapse of time following the intrusion, and the 

 minerals composing the magma crystallized and thus came to 

 be the hard Hollywood granite, which now forms the core of 

 the Santa Monica Range. 



