58 THE MOUNTAINEER 



Notes on the Bed Rock Geology of the 

 Olympic Peninsula 



By CHARLES E. WEAVER 



PROBABLY one of the least known and as yet nnexplored areas in the 

 continental portion of the Thiited States lies in the northwestern part 

 of the state of Washington and is known as the Olympic peninsula. 

 The interest in the geology of this region which was aroused during the 

 writer's outing with The Mountaineers has resulted in a few scattered notes, 

 part of which are derived from first hand information in the field, and part 

 from the published investigations of Dr. Ralph Arnold of the United States 

 Geological Survey, wiio has made a somewhat extended study of the geology 

 along the coast. The results here given are only general and entirely from 

 a popular standpoint and it is only after a detailed scientific study of the 

 whole area has been made that any account even approaching accuracy can 

 be attempted. The region is wild, heavily timbered and in many places 

 difficult of access and as no suitable maps are available, geological work must 

 be carried on under serious difficulties. However, the attractiveness of the 

 field, the grandeur of the scenery and the interesting and varied geological 

 problems to be worked out make the Olympic mountains of especial interest 

 not only to those interested in elucidating the geology of the west coast of 

 North America, but also to those who delight in the enjoyment of a vacation 

 spent in a primeval district which is as yet so little know^n. 



The Olympic peninsula is a rugged land area very nearly surrounded 

 by water. On the east it is bounded by Puget Sound and Hood's Canal, 

 on the north by the Straits of Juan de Fuca, on the west by the Pacific 

 ocean and on the south by Grays Harbor and the Chehalis valley. The 

 counties embraced within this area are Chehalis, Mason, Clallam, Jefferson 

 and Kitsap. The area occupied by this peninsula approaches something 

 like eight thousand square miles. The extent from east to west is about 

 eighty miles and from north to south about one hundred miles. 



The topographic features of the Olympic peninsula consist of a central 

 mass composed of high, rugged and serrated mountain ridges which grad- 

 ually diminish in altitude until they become a very low plateau along the 

 coast with an elevation of less than three hundred feet above sea level. 

 The high central portion of this peninsula, of which Mount Olympus is the 

 culminating point, has a general east to west trend and is perhaps twenty 

 miles long by ten to fifteen in wddth. The maximum elevation on the highest 

 I^eak of Mount Olympus is 8,250 feet and the average elevation in the district 

 around the mountain is between five thousand and eight thousand feet. 

 West of this central area the elevation of the mountain ridges decreases 

 and in the vicinity of the Hoh and Soleduck rivers it ranges from four to 

 live thousand feet, and from then on continues to decrease to nearly sea 

 level at the coast. To the northeast and southeast the elevation gradually 

 decreases and finally we have only low foothills along the Straits of Juan 

 de Fuca and Hood's Canal. 



The main central mass is drained by a large number of rivers which 

 head in the vicinity of Mount Olympus and from there radiate outward in 



