The geology of Washington’s Coast and Puget Sound is complex and beautiful and is one of the attributes that make Washington a great place to live, work and play. While many derive their livelihoods directly from these resources, we all depend on the health of the Coast and Puget Sound ecosystems, either directly or indirectly, whether we are aware of it or not. The Division of Geology and Earth Resources has done a great deal of geological work in the Puget Sound and coastal areas that can help with planning and decision-making associated with the unique hazards these environments pose.
Hazards common to both Puget Sound and marine coastlines of Washington State include:
Information on these hazards is available to the public through our interactive, online geology maps that can be accessed by visiting http://www.dnr.wa.gov/geologyportal. There you will find a number of themes specifically tailored to providing our users with information on geology and hazards of significance to coastal regions, including earthquake hazards, landslide hazards and soil liquefaction information, as well as information on regions at risk for tsunami inundation and tsunami evacuation routes in coastal regions.
Our geologists are actively researching coastal landslide and bluff hazards (see data download at right) and are engaged in landslide hazard zonation projects along the Washington coast. Additionally, an expanding number of earthquake hazard maps, tsunami inundation maps and evacuation information are available for many areas on Washington’s outer coast, the Strait of Juan de Fuca, and Puget Sound.
The Puget Lowland is characterized by its glacial geology, being largely composed of glacial till deposited by numerous pulses of glacial ice and flood waters during the Pleistocene. J. Harlen Bretz published a history of Puget Sound glaciation in 1913 that is still referred to by modern geologists. Indeed, current mapping (mostly at the 24K scale) of the Puget Lowland's glacial geology is ongoing. Visit our Geology Maps Online pages to find maps (PDFs) of coastal regions.
High population growth in the Puget Lowland has been, but need not be detrimental to the overall health of the Sound. Conscientious planning and consideration can overcome much of the risk.
Extensive work has been done by past DNR geologists to characterize the geology of coastal regions. Particularly, the work of Weldon Rau has provided a comprehensive overview of the geology of Washington's outer coast. His reports can be downloaded as PDFs (from the Files section at the right of this page) or are available as online books (click below).