CHAPTER XII. 



THE PACIFIC SLOPE : WASHINGTON, OREGON, AND CALIFORNIA 



WASHINGTON. 



2.12.01. Geology. Little is available in the way of systematic 

 descriptions of the geology of Washington, and an attractive field 

 remains to be developed. The rocks of the Rocky Mountains 

 extend across the panhandle of Idaho and show in northeastern 

 Washington, affording considerable amounts of ores. They are 

 prevailingly granite and gneiss, which have escaped being covered 

 by the enormous volcanic outbreaks of Tertiary and later time. 

 West of the granites a great plateau country of somewhat diversi- 

 fied surface is met. It seems to have been an ancient lake basin, 

 but is now covered by igneous rocks and deposits of volcanic tuff. 

 Still farther west the Cascade chain forms the central divide of 

 the State. The rocks are granites, flanked by Paleozoic, Mesozoic, 

 and metamorphic strata, much like the Sierras of California. 

 They were upheaved in large part before the Cretaceous, and since 

 then other movements have occurred. There are vast develop- 

 ments of igneous rocks, forming, as at Mount 3=$Qgi& (Rainier), 

 some of the highest American peaks. West of the Cascade range 

 is a great valley formerly marking a drainage system, but now 

 covered partly by glacial drift and partly by the waters of Puget 

 Sound. The glacial deposits are enormous, and render the prob- 

 lem of working out the geology very difficult. Some glaciers re- 

 main on the heights even to the present day. West of the Puget 

 Sound Basin is the northerly extension of the Coast range, locally 

 called the Olympics, and largely Cretaceous and Tertiary strata'. 1 



1 G. F. Becker, Tenth Census, Vol. XIII., p. 27. G. A. Bethune, First 

 Ann. Rep. State Geologist, 1891. A. Bowman, " Mining Developments on 

 the Northwest Pacific Coast and their Wider Bearing," M. E., XV. 707. 

 J. MacFarlane, Geol. Railway Guide, second edition, p. 262 ; notes by 

 Pumpelly, Willis, and others. Rec. J. S. Newberry, " Geology and Bot- 



