Geologic Features of Yakima Canyon: Technical Writing

A term research project for Geology 101 in Spring 2011.



Features of Yakima Canyon

                                                                                                                               
                                                                                                     
                                                                                      ^{Yakima River Canyon in Winter (Bureau of Land Management)}

The Yakima Canyon follows the meander of the Yakima River along US scenic highway 821, beginning after Umtanum Ridge, then meeting Wenas, Squaw and Umtanum Creeks, crosses north from Yakima County to Kittitas County, until it cuts through the Manastash Ridge Anticline (Kelsey 2011) 43 kilometers later. The canyon displays dramatic examples of erosion, basalt columns, and a variety of faults; since the time that the river began to carve out the canyon, 5700 acres of material have been removed (Public Lands). The numerous seismic shifts that helped to shape the canyon can be traced to the network of faults throughout the Umtanum and Manastash Ridges area are thought to be over 1.6 million years old (Kelsey 2011). The basalt flows that make up the majority of stratified material in the canyon exhibit many pillar formations that are covered in lichen ranging from pale greens to ambers and deep ochres. The striking beauty and solitude of the region make it a favorite spot for fishing, hiking, camping and biking.

                                  
              Overturned Umtanum anticline (Campbell 1975): A Geologic Road Log over Chinook, White Pass, and Ellensburg to Yakima Highways

The Basalt flows of the Yakima area and the Columbia Plateau are part of the greater Columbia Basalt Flows. The Columbia basalt flows are the result of a progression of several individual lava flows over a long period, from about 17.5 to 6 MYA (CRBG: NDG), and extend to parts of Idaho and Oregon. One theory of their origin is that they were caused by massive hotspot eruptions, much like Yellowstone and Long Valley; another is that an impact from a massive meteorite caused a catastrophic seismic chain-reaction leading to the flows.

Geologists have identified and mapped most of the layers in the canyon’s rock, many of which extend throughout the greater Columbia Plateau region. Much of the research information available for this paper was based on the studies of G.O. Smith, who wrote on the Ellensburg and Yakima region’s geology for the United States Geologic Survey, and several sources for this paper relied on his research. Smith made a distinction between the Yakima Basalt and the Columbia Basalt, seeing it as a distinct type; however, in publications after 1979, no mention is made of Yakima Basalt. I do find record that these flows have been re-categorized and reorganized several times, including new nomenclature since the publication of the majority of my research source material (USGS; Reidel et al 2002). To avoid confusion, I will refer to the geologic groups in the Yakima Canyon by the former names throughout the paper.   

             
                                                         Diagram of a roadside syncline, showing typical strata of the canyon (Campbell 1975)

Commonly occurring formations of the canyon are: Yakima Basalt (Roza and Ellensburg Formations) I believe now re-categorized as the Wanapum Formation of the Columbia Basalt, Vantage Sandstone, Squaw Creek Diatomite, Frenchman Springs and the Museum Flow; Smith also names the Wenas as a distinct formation, for the Yakima tributary Wenas Creek, which enters into the canyon near the southern Umtanum. The Yakima Basalt was originally recognized at an exposure in the Yakima Canyon. The Yakima Basalt is one of several  flows that make up the greater Columbia Plateau basalt, and is estimated to be between 900 and 1400 meters thick (Bingham et al 1966: G4.)

The Columbia basalt flows are the result of a progression of several individual lava flows over a long period. The Yakima Basalt covers an area from the crest of the Cascade Mountains to the Idaho’s Sawtooth Mountains, north of the Blue Mountains and south of the Pend Oreille, resulting from flows during the Miocene and early Pliocene ages (Smith 1901: 68; Waters 1961: 608).

                                    
                             Roza Flow basalt columns atop Squaw Creek diatomite, with Frenchman Springs at the base (Campbell 1975)

The Roza Member’s first type was recognized at the location along the southern canyon, between Umtanum Ridge and Wenas Creek. It is believed to be about 14 million years old (Columbia River Flood Basalts), and chiefly composed of two lava flows. The older of these flows is of a uniform thickness in the canyon, about 30 meters, and is believed to be part of a larger flow that covers an area of about 52,000 square kilometers, from Coulee City, Washington to Pendleton, Oregon. Typically the lower flow basalt is dark grey to blue, oxidizing to a deep brown, is porphyritic, and contains plagioclase, pyroxene, and olivine. This basalt typically forms in uniform columns two to three meters in diameter, and shows platy cleavage along regularly occurring segments in the column (Bingham 1966: G-8, G-9). This accounts for the dramatic, colorful roadside lichen displays visible when driving through the canyon.

According to Smith the Ellensburg formation is a mix of an original sediment layer up to 350 meters thick, not marine in origin, but made from eroded and volcanic sources in the Cascades (Mackin 1961; VanLandingham 1964: 729). These are primarily hornblende, andesite and pyroclastic ash. When these met with the basalt flow, according to Smith, they were intercalated and contemporaneously folded (Mackin 1961: 4-5). The Wenas Formation was made from a mix of these sediments and the basalt as well, formed as it extruded and cooled; this description seems to that of the Ellensburg Formation, except that the Wenas is not described as folded. The US Army Map Service classifies the basalt flows and sedimentary deposits in the Wenas part of the Ellensburg Formation of the Canyon as Pre- and Post-Vantage Sandstone Yakima Basalt (Campbell 1975: 4-5).                                 
                                   
                                                            Yakima Canyon wall showing uplift and slip-dip faults (Campbell 1975)

The Squaw Creek Diatomite is a relatively thinner layer in the Yakima Canyon strata, and indicates that prior to the Ellensburg and Roza formations’ extrusion, the region was covered in water. There are instances of pillow basalt in the canyon, but they are rare compared to the typical Roza pillar formations. The Frenchman Springs layer is composed of a series of basalt flows of similar composition.

The Yakima River Canyon is designated a protected area by the Washington Department of Natural Resources and the Bureau of Land Management. The river remains a fishery, with catch-and-release for trout in season, but is closed to all steelhead fishing. Campgrounds are seasonally open near the Wenas-Yakima confluence, and public boat access is available at Roza and near Manastash Ridge at Thrall outside of Ellensburg (BLM 2011).

ANNOTATED BIBLIOGRAPHY
FEATURES of YAKIMA CANYON 


Bingham, James W. and Maurice J. Grolier (1966) Contributions to Stratigraphy:  The Yakima Basalt and Ellensburg Formation of South-Central Washington, Geological Survey Bulletin 1224-G, Washington Department of Conservation Division of Water Resources
This source was published by the State of Washington as a geological and water resource bulletin, and intended for professional use. I believe it was relevant and reliable at the time of publication. Available in the Hazelwood Library.

Bureau of Land Management (BLM) (2011) Cover photo. Yakima River Canyon: public lands information center, Bureau of Land Management, retrieved 5/28/2011 <http://publiclands.org/explore/site.php?id=4568>
This was an electronic source published by the federal government, and I found it relevant for public use information, as well as a reliable photographic source.

Campbell, Newell P. (1975) Geologic Road Log Over Chinook, White Pass, and Ellensburg to Yakima Highways, State of Washington Department of Natural Resources, Division of Geology and Earth Resources 
This book was published by the State of Washington for professional use.  It was very relevant for maps, photographs and graphs showing the stratigraphy of Yakima Canyon. Available in the Hazelwood Library.

Columbia River basalt group (CRBG) (No Date Given) Theories on the cause of the Columbia Basalt Flows, retrieved 5/28/2011 < http://hugefloods.com/Basalt.html>
This electronic source appeared to be a hobby site created by a professional or paraprofessional geologist or historian. It had many photographs, and interpretations of geologic information, but little citation for original material. I was selective in what I chose to include from this source.


Kelsey, Harvey M., Tyler Ladinsky (2011) NEHRP Final Technical Report, USGS Award Number: G09AC00464: Investigations of tectonic deformation in the Yakima River canyon, Department of Geology, Humboldt State University
This source was written as a scholarly publication for professional use, and published by a university press.  It is a report on geological formations, water wells and evidence of seismic activity. I found it to be useful for maps and information; downloaded as a pdf file.

Hackin, J. Hoover (1961) A Stratigraphic Section in the Yakima Basalt and the Ellensburg Formation in South-Central Washington, State of Washington Department of Conservation, Division of Mines and Geology, State Printing Plant
This was a publication from the state of Washington, a reliable source. It was written as a descriptive paper on the superposition of rock layers in the area from Ellensburg to the Columbia River at Vantage, and was useful for general information on specific formations’ ages and mineral composition. Available in Hazelwood Library.

Reidel, S.P., V.G. Johnson, and F.A. Spane (2002) USGS Columbia River Basalt Stratigraphy in the Pacific Northwest, regarding nomenclature, retrieved 5/29/2011< http://or.water.usgs.gov/projs_dir/crbg/stratigraphy.html>
This publication was an original citation for the USGS page concerning the reassignment of nomenclature. It was very useful in comparing data on the Yakima Canyon; I used a link entitled “diagram of formations, members and units” on the USGS page listed above for comparing older and newer data, accepted in 1979, in an attempt to isolate, identify and name the strata of the canyon.