Lewis and Clark's Columbia River
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Lewis & Clark's Columbia River - "200 Years Later"
"Columbia River Basalt Group (CRBG)"
Includes ... Columbia River Basalt Group ... CRBG ... Anticlines ... Synclines ... Yakima Fold Belt ... Horse Heaven Hills Anticline ... Twin Sisters ... Wallula Gap ... Celilo ... Fulton Ridge ... Columbia Hills ... Horsethief Butte ... Mitchell Point ... Cape Horn ... Crown Point ... Multnomah Falls ... Angels Rest ...
Image, 2003, Wallula Gap basalts, click to enlarge
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Wallula Gap basalt flows, right bank, as seen from upstream. Image taken September 29, 2003.

Columbia River Basalt ...
The Columbia River Basalt is massive fissure lava flows which covered quite a bit of Idaho, Washington State, and Oregon. Formally called the Columbia River Basalt Group (CRBG), the flows are divided into five formations - the Saddle Mountains, Wanapum, Grande Ronde, Imnaha, and Picture Gorge Basalts. The majority of the CRBG flows are Early Miocene and are between 17 and 5.5 million years old. They were erupted from north-south fissures near the present-day Washington-Idaho border. The CRBG consists of approximately 300 thick sequences of flood basalt flows, each flow from 10 to over 100 feet in thickness, with an estimated eruptive volume of at least 700 cubic miles, making them the largest documented individual lava flows on Earth. The flows reached maximum thickness of 16,000 feet in the Pasco Basin, and in the Columbia River Gorge, 21 flows poured through forming layers of rock up to 2,000 feet thick.

Anticlines and Synclines ...
Concurrent with the CRBG eruptions was the folding and faulting of the basalt in the western part of the Columbia Basin, creating a system of anticlines (ridges) and synclines (valleys). This "ridge and valley" topography can easily be seen while driving along the Columbia River.

Western Columbia River Gorge ...
"Flood basalts of the Miocene Columbia River Basalt Gorup (CRBG) are among the most volumninous and far-traveled lava flows on earth. About 10% of the basalt flows that erupted on the Columbia Plateau between 17 and 12 Ma were voluminous enough to pass through the Cascade arc via a wide ancestral Columbia River valley, and some of them eventually reached the Pacific Ocean. Some of the larger flows invaded the marine strata, forming mega-invasive flows on the continental shelf and slope. ...

The basic geologic framework of the Columbia River Gorge has been known for over a century. In the western gorge, the package of Columbia River Basalt Group (CRBG) flood-basalt flows unconformably overlies volcanogenic rocks of ancestral Cascade volcanic arc. Vigorous and widespread volcanism characterized the arc from its inception 40 Ma until ca. 18 Ma, when activity greatly declines. The arc must have been relatively quiescent during emplacement of the most voluminous CRBG flows, because interflow volcanic sediments are sparse. The larger flows passed through a 50-km-wide ancestral Columbia River valley on their way to the ocean. Owing to late Cenozoic uplift of the Cascade Range and resultant incision by the Columbia River, CRBG flows are now spectacularly exposed in the cliffs and waterfalls of the Columbia River Gorge. The modern gorge roughly follows the northern margin of the broad Miocene valley. Grande Ronde flows clearly abut the northern paleovalley wall formed by early Miocene volcaniclastic rocks of the 19 Ma Eagle Creek Formation. ...

The slight southward dip of the Columbia River Basalt Group (CRBG) section and the underlying Eagle Creek Formation gives the western gorge an asymmetric physiographic cross section. In Washington, failure of weakly lithified Eagle Creek strata that dip toward the river under the load of superincumbent basalt has produced huge landslide complexes composed largely of CRBG debris. In Oregon, where strata dip away from the river, undercutting of the Eagle Creek Formation instead creates towering cliffs. As a result, the CRBG section south of the river consists of continuous cliffs, whereas to the north the CRBG forms scattered peaks (Greenleaf Peak, Table Mountain, Hamilton Mountain, and Archer Mountain) separated by low-lying terrain underlain by the Eagle Creek Formation or landslide debris. Each of these peaks is actually the southern end of a N-S ridge of CRBG, marking sites where basalt flows backfilled south-flowing tributaries of ancestral Columbia River."

Source:    Wells, R.E., Niem, A.R., Evarts, R.C., and Hagstrum, J.T., 2010, "The Columbia River Basalt Group -- From the gorge to the sea", IN: Geologic Society of America Field Guild 15, 2009.

Columbia River Basalts

Image, 2005, Horse Heaven Hills from Sacajawea State Park, click to enlarge
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Mouth of the Snake River looking towards the Columbia River, at the Horse Heaven Hills. Fishing docks are at Sacajawea State Park. Image taken September 25, 2005.

Image, 2004, Twin Sisters, Wallula Gap, click to enlarge
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Twin Sisters, Wallula Gap, Washington. Image taken September 26, 2004.

Image, 2004, Columbia Hills, click to enlarge
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Columbia Hills, Washington. View between Celilo and the Deschutes River. Image taken September 26, 2004.

Image, 2005, Basalt Flow upstream of Celilo Park, click to enlarge
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Fulton Ridge basalt flow between the Deschutes River and Celilo Park, Oregon. Image taken May 24, 2005.

Image, 2005, Basalt Flow, near Celilo, Oregon, click to enlarge
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Basalt Flow and Union Pacific train, between The Dalles and Celilo, Oregon. Image taken June 4, 2005.

Image, 2011, Horsethief Butte and Horsethief Lake, click to enlarge
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Horsethief Butte and Horsethief Lake. View from Columbia Hills State Park (Horsethief Lake State Park). Image taken September 28, 2011.

Image, 2010, Basalts near Chamberlain Lake Rest Area, click to enlarge
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Columbia River Basalts near Chamberlain Lake Rest Area, Washington. View from Tom McCall Nature Preserve, Oregon. Image taken March 6, 2010.

Image, 2005, Cape Horn, Washington, click to enlarge
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Cape Horn, Washington. Cape Horn as seen from Dalton Point, Oregon. Phoca Rock is near the base of the cliff. Cape Horn is a formation of Grande Ronde basalt flows which erupted in the Lower Miocene. The Cape Horn basalts are capped by Troutdale gravels, which in turn are overlain by the lavas of the small Mount Zion olivine basalt shield volcano of the Boring Lava Field. Image taken October 22, 2005.

Image, 2005, Crown Point from Portland Woman's Forum Scenic View, click to enlarge
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Crown Point and Vista House, Oregon. Crown Point is a remnant of a massive Priest Rapids intracanyon lava flow. The Priest Rapids is a member of the Wanapum Basalt of the Columbia River Basalt Group (CRBG), and erupted in the middle Miocene. View from Portland's Woman Forum Scenic View (formerly Chanticleer Point). Image taken October 22, 2005.

Imag5, 2005, Multnomah Falls, Oregon, Benson Bridge, click to enlarge
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Multnomah Falls, Oregon, with Benson Bridge. Multnomah Falls, located near Portland, Oregon, drops 620 feet over Grande Ronde Basalt of the Columbia River Basalt Group. The Missoula Floods enhanced the cliff face, eroding away loose and softer materials. At Multnomah Falls the visitor can view six flows in the cliff face, with pillow flows being visible in the upper sequence near the lip of the Upper Falls. Image taken March 6, 2005.

Image, 2004, Angels Rest and Devils Rest, Oregon, from Tunnel Point, click to enlarge
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Angels Rest (ridge left) and Devils Rest (cone on top), as seen from Tunnel Point, Oregon. Angels Rest is Columbia River basalt and lies uphill from Dalton Point, Oregon. Devils Rest is a Boring Lava cone. Image taken October 10, 2004.

From the Journals of Lewis and Clark ...

Clark, October 18, 1805 ...
This morning Cool and fare wind from the S. E. ...     Took our leave of the Chiefs and all those about us [from their camp, the location of today's Sacajawea State Park] and proceeded on down the great Columbia river     passed a large Island at 8 miles about 3 miles in length, a Island on the Stard. Side the upper point of which is opposit the center of the last mentioned Island and reaches 3 miles below the 1st. Island and opposit to this near the middle of the river nine Lodges are Situated on the upper point at a rapid which is between the lower point of the 1st Island and upper point of this; great numbers of Indians appeared to be on this Island, and emence quantites of fish Scaffold     we landed a few minits to view a rapid which Commenced at the lower point, passd this rapid which was verry bad between 2 Small Islands two Still Smaller near the Lard. Side, at this rapid on the Stard. Side is 2 Lodges of Indians Drying fish, at 2 miles lower and 14 below the point passed an Island Close under the Stard. Side on which was 2 Lodges of Indians drying fish on Scaffolds as above

[Today this reach has been inundated by the waters of Lake Wallula, the reservoir behind the McNary Dam. The Burbank Slough - part of the McNary National Wildlife Refuge - dominates the eastern bank of the Columbia and two islands which remain offshore of Wallula are Crescent Island and Badger Island.]    

at 16 miles from the point [junction of the Snake River with the Columbia, location of today's Sacajawea State Park] the river passes into the range of high Countrey at which place the rocks project into the river from the high clifts [Wallula Gap] which is on <both> the Lard. Side about 2/3 of the way across those of the Stard Side about the Same distance, the Countrey rises here about 200 feet above The water and is bordered wth black rugid rocks [Columbia River Basalt],     at the Commencement of this high Countrey [Wallula Gap] on Lard Side a Small riverlet falls in [Walla Walla River] which appears to passed under the high County in its whole cose     Saw a mountain bearing S. W. conocal form Covered with Snow [Mount Hood, Oregon].    passed 4 Islands, at the upper point of the <first> 3rd is a rapid, on this Island is two Lodges of Indians, drying fish, on the fourth Island Close under the Stard. Side is nine large Lodges of Indians Drying fish on Scaffolds as above [Yellepit area]; at this place we were called to land, as it was near night and no appearance of wood [Lewis and Clark are in the Port Kelley area, where today the islands offshore are under the waters of Lake Wallula.],     we proceeded on about 2 miles lower to Some willows, at which place we observed a drift log     formed a Camp on the Lard Side [Spring Gulch] under a high hill nearly opposit to five Lodges of Indians; Soon after we landed, our old Chiefs informed us that the large camp above "was the Camp of the 1st Chief of all the tribes in this quarter [Chief Yellepit], and that he had called to us to land and Stay all night with him, that he had plenty of wood for us &" This would have been agreeable to us if it had have been understood perticelarly as we were compelled to Use drid willows for fuel for the purpose of cooking, we requested the old Chiefs to walk up on the Side we had landed and call to the Chief to come down and Stay with us all night which they did;     ... we made 21 miles to day.

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*River Miles [RM] are approximate, in statute miles, and were determined from USGS topo maps, obtained from NOAA nautical charts, or obtained from the U.S. Army Corps of Engineers website, 2003, 2004.

  • Norman, D.K, Busacca, A.J., and Teissere, R., 2004, Geology of the Yakima Valley Wine Country -- A Geologic Field Trip Guide from Stevenson to Zillah, Washington, Washington Division of Geology and Earth Resources Field Trip Guide 1, June 2004;
  • Norman, D.K., and Roloff, J.M., 2004, A Self-Guided Tour of the Geology of the Columbia River Gorge -- Portland Airport to Skamania Lodge, Stevenson, Washington: Washington Division of Geology and Earth Resources, Open-File Report 2004-7, March 2004;
  • Swanson, D.A., and Wright, T.L., 1981, Guide to Geologic Field Trip Between Lewiston, Idaho, and Kimberly, Oregon, Emphasizing the Columbia River Basalt Group: IN: Johnston, D.A., and Donnelly-Nolan, J., (eds.), 1981, Guides to Some Volcanic Terranes in Washington, Idaho, Oregon, and Northern California: U.S. Geological Survey Circular 838, 189p;
  • Wells, R.E., Niem, A.R., Evarts, R.C., and Hagstrum, J.T., 2010, "The Columbia River Basalt Group -- From the gorge to the sea", IN: Geologic Society of America Field Guild 15, 2009;

All Lewis and Clark quotations from Gary Moulton editions of the Lewis and Clark Journals, University of Nebraska Press, all attempts have been made to type the quotations exactly as in the Moulton editions, however typing errors introduced by this web author cannot be ruled out; location interpretation from variety of sources, including this website author.
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June 2012