THE PLEISTOCENE OR GLACIAL PERIOD 913 



Atlantic coast south of the drift there have perhaps been complex 

 movements, but of no great range, in the course of the period. On 

 the whole, elevation (relative) appears to have exceeded depression, 

 but the latest movement (present) appears to have been one of sink- 

 ing, as the drowned ends of the valleys show. 



It is not improbable that movements of equal magnitude have 

 affected the interior regions of the continent, but except about 

 the lakes, there is no datum plane like the sea-level to which these 

 changes may be readily referred. In a few places, notable local 

 deformation is known. In western New York 1 and Ohio, the 

 solution of underlying gypsum and salt is suspected of being the 

 occasion of some of the slight deformations which have been 

 observed. 



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

 relatively, some 1,500 feet since the Pliocene. Other parts of the 

 California coast, and some of the adjacent islands, have been sub- 

 siding during the same period. 2 Near San Francisco, the surface 

 is thought tc have ranged from 1,800 feet below its present level, 

 to 400 feet above. 3 Along the northwestern coast of Oregon, a 

 rise of at least 200 feet during the Pleistocene 4 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 especial interest because they contain human 

 relics, probably the oldest known. The relics consist of rude stone 

 implements, bones of mammals with human markings on them-, 

 and bones of human beings. 



1 Gilbert, Proc. Am. Ass. Adv. of Sci., Vol. XL, p. 249. 



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

 Geol., Vol. II, p. 235. 



3 Ashley, Jour. Geol., Vol. Ill, p. 449. 



4 Diller, 17th Ann. Kept., U. S. Geol. Surv., Pt. I. 



