GEOLOGY OF THE WASHINGTON COAST
By Weldon W. Rau
Long before the Washington coast was viewed by Perez, Heceta, and Bodega y Cuadra, its beaches served as highways between Indian villages. Later the early settlers used them in much the same way. Today, however, the coast is a place where a variety of activities are pursued. Some visitors are content just to view the many scenes of natural beauty, perhaps take a short walk on the beach or, on occasion, observe the mighty force of winter storms being spent upon the sandy shores. Still others may be attracted by the colorful marine life of tide pools or the countless pieces of curiously shaped driftwood deposited high on the beach by winter storms.
Among these many visitors, some no doubt are also curious about the processes that formed the rock foundation for this unique and picturesque setting along Washington's part of our continent's western edge. What is the origin of rock strata that form cliffs and rocky beaches in many places along the coast? What were the forces that twisted and deformed many of these rock strata, and how were they generated? Where did the thick deposits of sand and gravel come from that are so common in many of the high cliffs, when were they deposited, and how did they get there? What do the fossils that are contained in some of the rocks reveal about the age of the rocks and about ancient environments? Although these and many other related geological questions are of particular interest to the geologist, very likely many others have also pondered at least some of these questions.
This publication, therefore, was prepared for the purpose of sharing some of the facts, theories, and concepts currently known to geologists or applied by them in their attempt to unravel the geologic history of the Washington coast and adjacent areas of the Olympic Peninsula. It is an outgrowth from comprehensive geologic studies now being conducted by the author for the purpose of collecting and interpreting basic data on the distribution and characteristics of the rock formations of the western part of the Olympic Peninsula.
The illustrations and accompanying captions alone tell a geologic story that many may find of interest. The text, in two parts, develops this story more fully.
Part I tells about the rock formations exposed along the coast and, in chronologic order, discusses the geologic events revealed by the formations. Included are comments on the general composition of the rock formations, their probable origin, and what they most likely have under gone since they were first formed. Part II describes less technically the geology of individual segments of the coast along a continuous traverse beginning at Point Grenville and extending northward to the Hoh River. Thus, the reader that is concerned only with a portion of this area can obtain general information about the rock formations and their geologic history locally without reading Part II in its entirety. However, some repetition is necessary as may be noted by those who do examine all of this part. For the reader desiring greater detail on certain related subjects, references are made to Part I, as well as additional, more technical publications.
All areas along the coast between Point Grenville and the Hoh River are accessible on foot with the exception of about half a mile along Pratt Cliff, where shear cliffs meet the ocean surf at all times. In many places tide conditions must be considered and several areas can only be reached during lowest tides. All of the coastal area south of the Olympic National Park boundary is part of the Quinault Indian Reservation and presently may be traversed only with the consent of the Quinault Tribal Council at Taholah.
The assistance and advice of, and discussions with, numerous colleagues have been invaluable to the writing of this report. Many published works have served either directly or indirectly as a source of background material, but, due to the nature of this report, not all have been cited specifically. Acknowledgments are here extended to these contributors.
Unpublished studies, including that of the late S. L. Glover, formerly of the Washington Division of Mines and Geology; a Master's thesis by E. M. Baldwin of the University of Oregon; University of Washington student theses by J. L. Moore and by A. J. Koch; a Stanford University Ph. D. thesis by R. J. Stewart; and a University of Southern California Master's thesis by A. D. Horn have all been particularly useful sources of basic data and original concepts. Discussions during the past several years with P. D. Snavely, Jr., N. S. MacLeod, H. C. Wagner, and W. M. Cady of the U.S. Geological Survey; R. J. Stewart of the University of Washington; and A. D. Horn of North Seattle Community College have been most stimulating and helpful. Special thanks is extended to R. W. Tabor of the U.S. Geological Survey for his constructive review of the manuscript. Paleontological contributions of W. O. Addicott and the constructive suggestions concerning late Cenozoic deposits of D. R. Crandell, both of the U.S. Geological Survey, are greatly appreciated.
Many people of the communities of Pacific Beach, Moclips, Taholah, Queets, and Kalaloch have, through their assistance, contributed much to this report. The writer is particularly grateful for the assistance and historical information made available by Mr. and Mrs. George Bertrand of Queets, Mrs. Connie Fox of Pacific Beach, Mr. and Mrs. F. L. Dickinson and Mrs. Rella Binion of Kalaloch, and Mrs. C. H. Barlow of the Hoh River valley. The cooperation of the Quinault Tribal Council in granting access to the Reservation beaches, and the general assistance of many staff members of the Olympic National Park Service is greatly appreciated. The Mobil Oil Corporation, through the generous offer of J. R. Sprague, has supplied several technical services for which the writer extends his gratitude. Thanks are due to all staff members of the Geology and Earth Resources Division for their aid in individual ways in the preparation of this report. The capable assistance of G. D. Cloud during the summer months throughout the course of this study is gratefully acknowledged.
Last Updated: 28-Mar-2006