37 



The Pleistocene, or as many geologists term it the Quater- 

 nary, while relatively short in comparison with the previous 

 geologic epochs, presents many dramatic elements profoundly 

 affecting the character and distribution of the present life 

 upon our planet, including the entire span of human existence. 

 Our existing knowledge concerning this phase of terrestrial 

 history has recently been summarized and amply documented 

 in an extensive monograph by Charlesworth (1957). 



The Pleistocene has been characterized by a continuance of 

 the volcanic activity that prevailed during the Pliocene, of 

 which our North Pacific area is a good example. If carbon-14 

 datings have been correctly interpreted the explosive erup- 

 tion of Mt. Mazama occurred about 6,500 years ago. The 

 great eruption of Mt. Katmai in Alaska is a part of recent 

 history. 



Great changes also occurred during the Pleistocene in the 

 distribution of both sea and land, involving according to the 

 views of Charlesworth more than seventy percent of the sur- 

 face of the planet. The presence of raised beaches, arranged 

 frequenrly in step-like fashion on the coasts of all of the con- 

 tinents, indicates changes of level, but as to whether of sea 

 or land has been a matter of dispute. Charlesworth would 

 ascribe these successive steps, which range in magnitude from 

 a few feet to one thousand feet or more, primarily to crustal 

 changes of the type now in progress in various parts of the 

 world. In Finland, where one generation wades the next 

 generation plows. Hudson Bay is evidently destined to be- 

 come a broad plain traversed by a river. Holland on the other 

 hand will have to build higher dikes to hold back the sea. 



On our Pacific Coast we have abundant evidence of changes 

 of level; in California a dozen or more such steps have been 

 noted. Similar formations, some of them at considerable alti- 

 tude, have been discovered in British Columbia and Wash- 

 ington. One such area is exposed on the retreating eastern 

 shore of Willapa Bay in southwestern Washington. This is 

 illustrated on plate XIV. Not shown in the figures is a group 



