Recent Geology Field Trip in Eastern Jefferson County

Last year, geologists Michael Polenz and Trevor Contreras (DNR), mapped the bedrock and glacial geology of an area roughly from Chimacum to Quilcene along the west side of Hood Canal in eastern Jefferson County.

On Saturday August 2nd the Division of Geology and Earth Resources led a geology field trip in the area, along with geologists Carol Serdar of the Washington State Department of Ecology and Jeff Tepper of the University of Puget Sound. The trip was sponsored and organized by Michael Machette with the Jefferson Land Trust.

Michael and Trevor providing an overview of Center and Quilcene geology at an outcrop of Lyre Formation conglomerate. Photo courtesy of Michael Machette (Jefferson Land Trust).

Michael and Trevor providing an overview of Center and Quilcene geology at an outcrop of Lyre Formation conglomerate. Photo courtesy of Michael Machette (Jefferson Land Trust).

About 30 local geology enthusiasts visited 10 sites in the area showcasing Crescent Formation basalt and conglomerate, Lyre Formation pyroclastic flow deposits, conglomerate, and other marine sedimentary rocks of the region, as well as overlying sediment deposited within the last 100,000 years.

As geologists, it’s very rewarding to see members of the community interested and engaged in the geology around them.

Michael Polenz discussing Lyre Formation mudstone along State Route 104 near Center Rd. Photo courtesy of Ian Hubert (DNR).

Michael Polenz discussing Lyre Formation mudstone along State Route 104 near Center Rd. Photo courtesy of Ian Hubert (DNR).

The ongoing 7.5-minute quadrangle mapping is part of an effort to document the geology along the Hood Canal in detail. This area is important ecologically; slope instability, water quality, and dissolved oxygen levels affect shellfish and salmon habitat. Population is steadily rising there as well, making water resources increasingly more difficult to acquire.

Vashon Stade sediment of the most recent glacial advance dominates the surface in this area; evidence of thousands of feet of ice raking across the landscape is reflected in the modern environment. The area east of Discovery Bay is dominated by bedrock. Crescent Formation basalt flows and sedimentary interbeds and overlying Lyre Formation marine sedimentary rocks represent stacking of ocean floor above the subducting Juan de Fuca tectonic plate.

For more information on the area, check out recent 7.5-minute geologic maps for the Hoodsport, Lilliwaup, Holly, Eldon, Lofall, Seabeck–Poulbo, Brinnon, Belfair, Lake Wooten, and Skokomish Valley–Union quadrangles. We plan to publish the mapping for the Quilcene and Center quadrangles this fall.

Newly Published: Chehalis River Floodplain Geomorphic Mapping

We’re pleased to announce the release of a new publication!

Geomorphic mapping of the Chehalis River floodplain, Cosmopolis to Pe Ell, Grays Harbor, Thurston, and Lewis Counties, Washington

by S. L. Slaughter and I. J. Hubert

Relative elevation model of a portion of the study area approximately 5 miles east of Montesano showing the junction of the Chehalis River floodplain with the Satsop River.

Summary:  A relative elevation model of the Chehalis River floodplain was generated using 1- and 2-meter lidar and 12-inch-resolution aerial images in order to delineate subtle landforms on the floodplain for a 110-mile reach of the Chehalis River between Pe Ell and Cosmopolis, Washington. The relative elevation model represents elevation of features on the floodplain relative to the Chehalis River’s water surface by removing downstream changes in elevation associated with the channel gradient. Subtle landform features, such as primary, secondary, and abandoned channels, sloughs, swales, and natural and artificial levees were then identified within the floodplain. This information is useful to biologists, wetland scientists, land managers, property owners, and floodplain and watershed managers. The report contains 59 pages of maps at 1:28,000-scale and two pages of text.


Two New DGER Publications Released

We’re happy to announce the release of two new DGER publications!

Geothermal Favorability Model of Washington State

by D. E. Boschmann, J. L. Czajkowski, and J. D. Bowman 

Geothermal Resource Potential Map of Washington State

Geothermal Resource Potential Map of Washington State

Summary:  Geographic Information System (GIS) modeling of statewide heat, permeability, and infrastructure data, including volcanic centers, faults, earthquakes, temperature-gradient wells, thermal springs, young silicic intrusive rocks, and transmission lines produced layers showing relative geothermal favorability in Washington State. Regional modeling like this is one way to reduce costs in geothermal exploration by helping to more precisely locate areas worthy of additional research.

Landslide and liquefaction maps for the Ocean Shores and Westport peninsulas, Grays Harbor County, Washington: Effects on tsunami Inundation zones of a Cascadia subduction zone earthquake

by S. L. Slaughter, T. J. Walsh, Anton Ypma, and Recep Cakir

Ocean Shores and Westport liquefaction susceptibility from a Cascadia subduction zone 9+ earthquake

Ocean Shores and Westport liquefaction susceptibility from a Cascadia subduction zone 9+ earthquake

Summary:  Modeling of earthquake-induced soil liquefaction from ground shaking associated with a M9+ Cascadia subduction zone earthquake was performed as part of the National Tsunami Hazard Mitigation Program for the Ocean Shores and Westport peninsulas. Earthquake-induced ground failures, such as liquefaction or landslides, may adversely affect tsunami evacuation by blocking or damaging evacuation routes; the creation of these maps will aid emergency management officials in evaluating the suitability of existing evacuation routes and assembly areas.

Happy Reading!

Jari Roloff, Geology Editor at DGER, retires

Jari Roloff

Jari at the garden of Little & Lewis, Bainbridge Island, Washington

Last Monday was Jari Roloff’s last day with the Division of Geology and Earth Resources. After 23 years with the Division eliminating extraneous parentheticals, shortening run-on sentences, and generally saving us all from embarrassment, she is leaving us to finally relax.

We will miss her witty exasperation at our more-than-occasional use of incoherent grammar and her gentle, yet critical eye for detail. We are grateful for her uncanny ability to edit while leaving the authors their ‘voice’ intact. Her artistry, style, and experienced eye are evident on every publication we’ve produced for a very long time; thanks to her refinement of graphics to the level of a pixel, some of those publications won awards.

So please raise your coffee mugs to Jari Roloff, geology editor extraordinaire, gerund master, past and present perfectionist. May her subjects and verbs always agree. More importantly, may she think back fondly on us and her time here in Geology and may she visit us often. We only hope that she’s left enough clues and dropped sufficient hints so that we can continue to not embarrass ourselves in the future.

New TsuInfo Alert newsletter has been published

TsuInfo Alert is a bi-monthly newsletter that links scientists, emergency responders, and community planners to the latest tsunami research. This newsletter is published by the Washington Department of Natural Resources, Division of Geology and Earth Resources on behalf of the National Tsunami Hazard Mitigation Program, a state/federal partnership funded through the National Oceanic and Atmospheric Administration. It is made possible by a grant from the Federal Emergency Management Agency via the Washington Military Department, Division of Emergency Management.

February (v. 16, no. 1) [PDF; 2 MB]

Dating rocks on Valentine’s Day!

Valentines Foraminifera with scale bar

DGER geologists Trevor Contreras, Michael Polenz, Annette Patton and Harley Gordon are collaborating with the University of Washington’s Burke Museum to better date Tertiary rock formations along Hood Canal. Just as with macrofossil assemblages, microscopic fossils can be used to correlate an unidentified rock with known units. These tiny fossils pack quite a punch, despite their small size. The species of fossils in a given sample can indicate the specific age of the rock and allow researchers to deduce key information about environmental conditions at the time the microfossils and their accompanying sediments were deposited. Such knowledge provides valuable insight into our understanding of the age and stratigraphy of Tertiary sandstones and mudstones exposed in the current mapping area between Discovery Bay and Quilcene.


Foraminifera, like those pictured here, are members of a group of single-celled protozoans that primarily live in marine environments. The living organisms construct chambered shells in a variety of shapes and sizes, either by secreting a solid calcite shell or by cementing together grains that they pick up from the ocean floor. These organisms are particularly valuable microfossils because they are abundant, diverse, and morphologically distinct. Foraminifera also make useful biostratigraphic markers because most species are benthic (they live on the ocean floor). Unlike many planktonic organisms that float along ocean currents, such species remain geographically confined and form unique and local assemblages of fossils.