210 SOUTHERN CALIFORNIA GEOLOGY 



and corresponding uprisings of the surrounding and 

 outlying regions where the loads did not exist. These 

 movements were accompanied by foldings and fault- 

 ings of the kinds which we have described. 



Although situated southwest of the margins of the 

 former ice sheets that weighed down the crust of the 

 northern regions, one finds here in California the rec- 

 ords of certain other synchronous events which cause 

 us to believe, if the theory of isostasy is true, that the 

 presence of these inexpressibly heavy ice loads of 

 distant regions above the plastic sub-crust and the 

 removal of water load from above the oceans, must 

 have had wide effects upon the outlying areas, includ- 

 ing Southern California. 



It is here then, in Southern California that we 

 should find the events of the great Glacial Epochs rec- 

 orded in terms of profound crustal movements of the 

 kinds which we have already described, and which are 

 reflected in the present-day fault lines, highlands and 

 valleys. These effects are so overwhelmingly con- 

 spicuous in Southern California that we wonder that 

 they have not attracted the attention of geologists 

 rather than many other and less important subjects. 



The more we grasp and absorb the great principles 

 of isostasy, the more apparent does it become that vast 

 equilibristic efforts must have influenced the regions 

 bordering the ice-sheets of the glacial periods. This 

 effect being the result of the deposition and later melt- 

 ing of the tremendous ice loads over large, but re- 

 stricted portions of the yieldable earth's crust. Prob- 

 ably each of these four or more ice loads initiated 

 crustal movements of far-reaching extent, and it will 

 probably be ascertained in the future that the great 



