LIFE 663 



Some of the islands of Southern California seem to have risen, 

 ri-lativi-ly, some 1,500 feet since the Pliocene. Other parts of the 

 California coast, and some of the adjacent islands, have been sinking 

 during the same period. 1 Near San Francisco, the surface is thought 

 to have ranged from 1,800 feet below its present level to 400 feet 

 above. Along the northwestern coast of Oregon, a rise of at least 

 200 feet during the Pleistocene 2 has been estimated. 



Foreign 



The salient points in the glacial history of Europe have been 

 sketched, and some indication has been given of the extent of the 

 deployment of ice in other continents. It need only be added here 

 that outside the areas affected by the ice, there are, in all continents, 

 accumulations of sediment of the sorts just enumerated. In 

 Europe there are cave deposits of Quaternary, perhaps of glacial, 

 age, which are of interest because they contain human relics, prob- 

 ably the oldest known. The relics consist of rude stone implements, 

 bones of mammals with human markings on them, and bones of 

 human beings. 



LIFE 



Destructive effects of glaciation. We must believe that the suc- 

 cessive ice-sheets, several million square miles in extent, destroyed 

 much life, and caused great changes in that which survived; yet, so 

 far as the record shows, the difference between preglacial life and post- 

 glacial life is less than might have been expected. More than half 

 the known species of marine Pliocene invertebrates are still living, 

 though in the transition between several of the more ancient periods, 

 nearly all species disappeared. Of Pliocene plant species, too, many 

 are still living; but the land vertebrates of that period were very 

 generally replaced by new species, and the same appears to be true 

 of the insects. 



When the ice was most extensive, the sum total of life on the 

 earth must have been reduced greatly. Even the life of to-day is 

 probably less in amount than that of the middle Tertiary. Not only 

 this, but existing life is probably but poorly adjusted to its surround- 

 ings, for it is improbable that, in the millions of square miles where 

 life was destroyed by the ice, there has yet been worked out the 



1 Lawson, Bull. Dept. Geol., Univ. of Calif., Vol. I. Reviewed in Jour. Geol., 

 Vol. II, p. 235. 



1 Diller, i7th Ann. Kept., U. S. Geol. Surv., Pt. I. 



