Geological Papers. 155 



GEOLOGY. 

 Introductory Remarks. 



The high mountains form a circular area forty miles in diameter 

 and 6000 to 8000 feet in height in the east central part of the pen- 

 insula. They are alpine in their central area, and are character- 

 ized by glacial sculpture, precipitous slopes, and high, barren 

 ridges, with intervening prairie lands. From this central area, as 

 has been stated, the streams radiate out toward the coast-line in 

 ail directions, the radial pattern being very perfect toward the coast 

 region but less perfect in the mountain district. Along with the 

 radial drainage-courses there also radiates outward from the central 

 mass a system of ridges, the divides between the streams. Some 

 of these ridges are due to erosive agencies. Many of them, how- 

 ever, are the ref-ult of uplift. Those along the Strait of Fuca are 

 the upturned edges of fault blocks, the streams following the fault 

 lines. Those radiating out toward the Pacific are anticlinal folds, 

 the streams here occupying the synclines. These anticlinal folds 

 jut out to sea as bold headlands, and still farther out as islands 

 and reefs, and shallow- water areas known as "the banks." But to 

 consider the region as a whole, the surface slopes gently seaward 

 from an elevation of 5000 feet. The streams, therefore, seem to 

 be consequent to some imaginary surface of double curvature. As 

 will be noted later, neither volcanic debris nor Tertiary rocks have 

 been found in the central mountain mass; nothing but upturned 

 slates and sandstone and other rocks of pre-Tertiary age are found, 

 and these pitched to a vertical position and the Tertiary of the 

 lower country deposited upon their upturned, eroded edges. It 

 would seem, therefore, that the radial drainage was initiated on 

 the domed surface of a peiie-piain. 



Concerning the drriinage of this region and its origin. Doctor 



Arnold says:^" 



"The drainage of the region is radial, the radial pattern being 

 very perfect about the borders of the high mountains, while within 

 the mountains it is less perfect. The streams of the peiiiuf-ula are 

 arranged much like the spokes of a wheel, ot which the region of 

 the high mountains is the hub. This pattern could have one of 

 three possible origins: First, the drainage was initiated on a vol- 

 canic accumulatitjn about a center; second, the drainage was ini- 

 tiated on the domed surface of Tertiary strata, which has since been 

 removed by erosion ; third, the drainage was initiated on the domed 

 surface of a pene-plain. By all of these hypotheses the streams are 

 consequent to some imaginary surface of double curvature. The 

 first is disproved by the absence of extensive volcanic material. 



16. Bull. Geol. Soc. Am., vol. 17, pp. 454-455. 



