Lewis and Clark's Columbia River
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Lewis & Clark's Columbia River - "200 Years Later"
"Bonneville Landslide, Red Bluff Landslide, and the Cascade Landslide Complex, Columbia River Gorge, Washington"
Includes ... Bonneville Landslide ... Red Bluff Landslide ... Mosley Lakes Landslide ... Carpenters Landslide ... Cascade Landslide Complex ... "Table Mountain Landslide" ... Bridge of the Gods ... Table Mountain ... Red Bluffs ... Greenleaf Peak ...
Image, 2005, Columbia River looking downstream Bridge of the Gods, click to enlarge
Click image to enlarge
Columbia River looking downstream from Bridge of the Gods, with the toe of the Bonneville Landslide visible on the right. Image taken May 13, 2005.


Cascade Landslide Complex ...
The Bonneville Landslide is the youngest of the four landslide lobes within the "Cascade Landslide Complex", with the other three being the "Red Bluff Landslide" north of the Bonneville Landslide, the "Mosely Lakes Landslide" embedded within the Red Bluff Landslide, and the "Carpenters Landslide" located southwest of the Bonneville Landslide. The "Cascade Landslide Complex" was so named in 1961 from study by William S. Wise. Research today (J.R. Randall, 2012, Master's Thesis, Portland State University) questions whether the Mosley Lakes Landslide really is a landslide as it does not have typical landslide characteristics.

More Cascade Landslide Complex ...
According to Richard Hill in "A New Look at an Old Landslide" (Oregonian 1999, reprinted in "Washington Geology", 2001):

"The Bonneville Landslide, which tumbled from Table Mountain, has intrigued scientists for decades. It is the youngest and largest of four adjacent slides that make up the 14-square-mile Cascade Landslide Complex north of the Columbia near Cascade Loacks and Stevenson, Wash. The Area on the Columbia's north side is prone to landslides because of steep terrain made up of formations that tip toward the river. Columbia River basalt overlies the fragile, clay-filled Eagle Creek and Weigle Formations. The cliffs exposed when the mountain gave way easily can be seen north of Bonneville Dam. ...   The landslide unleashed blocks of rock as large as 800 feet long and 200 feet thick down the mountain, creating a temporary earthen dam more than 200 feet high -- three times the height of Bonneville Dam."

"The Cascade landslide complex is an impressive example of mass wasting created by multiple events. The source area includes portions of Table Mountain and the Red Bluffs in Washington. The landslide complex covers 12 to 14 square miles, with individual slide deposits of about 2 to 5 square miles.

The Bonneville landslide (a lobe of the complex) has an area of about 5.5 square miles. Debris from the source area reached as far as 3 miles to the southeast and buried the pre-slide Columbia River channel, which was about 1.5 miles north of its present location. The landslide substantially diverted the river channel toward the Oregon shoreline. The second powerhouse of Bonneville Dam abuts against the landslide. If you look north of the dam, you can see the cliffs that were exposed after the mountain gave way. ...

The river water impounded by the Bonneville landslide dam rose tens of meters, creating a lake that stretched almost 70 miles (up to the present-day John Day Dam). After a few months, the Columbia rose high enough to wash through the southern side of the landslide creating a flood of water that was 100 feet deep at Troutdale. Afterwards, things returned to normal, except that the river was displaced a mile to the south and the Cascade Rapids had formed.

Evidence for the landslide dam includes submerged tree stumps observed upstream. Evidence for catastrophic flooding from the breach has been observed downstream near the mouth of the Sandy River and at other locations. The Cascade Rapids, which developed from the breaching of the landslide dam, and the submerged forests were later inundated by the reservoir from the 1938 Bonneville Dam.

Although the slide complex has been extensively studied, the exact age of the slide remains a controversy. ...


Source:    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 State Division of Geology and Earth Resources Open-File Report 2004-7, March 2004.


Image, 2011, Table Mountain, Greenleaf Basin, Greenleaf Peak, Washington, click to enlarge
Click image to enlarge
Table Mountain, Greenleaf Basin, and Greenleaf Peak, Washington, as seen from Cascade Locks Marina, Cascade Locks, Oregon. The Bonneville Landslide is far left and originated from Table Mountain, and the Red Bluff Landslide is straight ahead and originated from the Greenleaf Basin/Greenleaf Peak area. Image taken May 20, 2011.


Bonneville Landslide, etc.

  • Bonneville Landslide ...
  • Bridge of the Gods Legend ...
  • Carpenters Landslide ...
  • Cascade Rapids ...
  • Dating the Bonneville Landslide ...
  • Greenleaf Basin Rock Avalanche (2008) ...
  • Ives, Pierce, and Hamilton Islands ...
  • Mosley Lakes Landslide ...
  • Red Bluff Landslide ...
  • Submerged Forest ...


Bonneville Landslide ...
The Bonneville Landslide slid from Table Mountain, giving rise to the Bridge of the Gods legend and creating the historic Cascade Rapids. The landslide lies approximately four miles north of the Columbia River, inland from the Washington community of Stevenson. Across the Columbia lies Cascade Locks. The landslide extends downstream to the Bonneville Dam and Hamilton Island.

"The Bonneville landslide blocked the entire Columbia River and created a lake that extended for tens of miles upstream. The bridge mentioned in the tribal stories was the pile of rocky landslide debris that allowed people to walk form one side of the river to the other during the time the river was blocked. The lake eventually overtopped the rocky blockage and rained. But the post-landslide Columbia River had been pushed more than a mile farther southeast than its pre-landslide channel and over to the Oregon shore. By the time Lewis and Clark arrived, the Columbia had cut down through rocks to create the "Great Shoot" or rapids mentioned by the explorers.

The big cliff of rock visible at Table Mountain, capped by a thick sequence of lava flows of the Miocene age Columbia River Basalt, is the headscarp or source area of the Bonneville landslide, whose debris trail extends to the southeast toward the Columbia River. The impressive cliffs east of Table Mountain that include Red Bluffs, above Skamania Lodge and the Columbia Gorge Interpretive Center, are the headscarp of what is likely an older, although still-active, slowly moving landslide complex. ..."


Source:    Pringle, P., 2009, "The Bonneville Slide", IN: Columbia Gorge Interpretive Center Museum, "Explorations", downloaded April 2014.


Image, 2013, Table Mountain, Washington, click to enlarge
Click image to enlarge
Table Mountain, Washington, as seen from Hamilton Island, Washington, with part of the Bonneville Landslide in the foreground. Image taken February 19, 2013.


Bridge of the Gods Legend ...
Various versions of the "Bridge of the Gods" legend exist, all with a common theme of volcanoes and a land bridge. The most common version given has it that the sons of Old Coyote, Wy’east (Mount Hood) and Pahto (Mount Adams), were powerful braves both in love with a maiden (Mount St. Helens). Because they crossed the “Bridge of the Gods” to fight over their love for her, Old Coyote collapsed the land bridge to keep his sons from fighting.

Image, 2010, South Support, Bridge of the Gods, click to enlarge
Click image to enlarge
South Support, Bridge of the Gods, Cascade Locks, Oregon. Image taken October 18, 2010.


Carpenters Landslide ...
"The Carpenters Landslide, adjacent to and west of the Bonneville Landslide covers an area of 2.75 km². Wise (1961) briefly describes the Carpenters Landslide to have moved during a two to three week period, and Palmer (1977) states that reports of rockfalls close to Carpenters Lake occurred in 1955 and 1974. Other than this, detailed information is lacking. It is likely to have occurred before the Bonneville Landslide."


Source:    James R. Randall, 2012, Characterization of the Red Bluff Landslide, Greater Cascade Landslide Complex, Columbia River Gorge, Washington, Master of Science in Geology Thesis, Portland State University.


Cascade Rapids ...
Throughout history the Cascade Rapids were a trecherous area of the Columbia River. In 1805 Lewis and Clark arrived in the area and camped two nights at the head of the rapids while they portaged around. They called the Rapids the "Great Shute". In 1896 the "Great Shute" was bypassed with completion of the Cascade Locks. In 1938 the Cascade Rapids disappeared under the rising waters of Bonneville Reservoir the waters behind the Bonneville Dam.


Dating the Bonneville Landslide ...
While currently accepted belief was that the Bonneville landslide occurred about 1100 A.D. (800 plus years ago) new radiocarbon dates from a core of a Douglas fir buried 150 feet under the massive slide indicate the fir was killed about 400 years ago and perhaps as recently as 250 years ago.

According to an Oregonian article by Richard Hill (2002):

"... Radiocarbon dates taken in 1958 from drowned trees indicated that the slide occurred between 1250 and 1280. A quarter-century later, a radiocarbon date of wood samples taken from within and below the landslide deposit put the date at about 1100. Four years ago, Pringle and Robert L. Schuster of the U.S. Geological Survey had radiocarbon dates taken of a buried Douglas fir that indicated the tree died between 1500 and 1760. That would place the slide close to the earthquake in 1700 that devastated the Northwest coast. Counting the tree rings, with each ring representing one year of the tree's life, they estimated that the tree died in about 1699. But the mystery of the slide's date has taken new twists recently. Last year, Nathaniel D. Reynolds, then a graduate student at Washington State University in Vancouver, used a technique called lichenometry to estimate the age of the Bonneville Landslide. The dating method uses the growth rate of specific lichen species as an indicator of the age of the surface the lichen is growing on. Lichens, slow-growing organisms formed from an association between a fungus and an alga, can be used for dating earthquakes and landslides because they quickly colonize fresh rockfalls that occur in the wake of a quake. Once established, they form at a constant rate if left undisturbed. Reynolds, now with the U.S. Forest Service, said his study indicates the landslide probably happened between 1670 and 1760. "These results demonstrate that the Bonneville Landslide may have occurred more recently than previously believed," Reynolds said in a recent article in Washington Geology. The dates "provocatively bracket" the powerful offshore Cascadia Subduction Zone earthquake of 1700, he said, but he cautioned that the study doesn't prove that the quake caused the landslide.

The research plot thickened with the recent surprising discovery of tree samples cut from the landslide site in 1934 by the late Donald B. Hamilton of Johns Hopkins University and the University of Minnesota before Bonneville Dam was completed. Pringle and Reynolds, along with colleagues Jim E. O'Connor, a hydrologist with the Geological Survey in Portland, and Alex C. Bourdeau, an archaeologist with the U.S. Fish and Wildlife Service in Sherwood, had wondered where the samples were. The Western Forestry Center, where some of the samples had been kept, burned to the ground in 1964. ... "So the four of us went over there and they drag these slabs out," Pringle said. "We couldn't believe it. They had four slabs -- two were from living old trees and two were from this submerged forest of the Columbia. We were just drooling." O'Connor and Bourdeau took samples for radiocarbon testing, and Pringle took samples for tree-ring dating. Pringle found that the sample from a submerged forest tree appears to have died the same year -- 1699 -- as the buried tree that he and Schuster had studied. "I was amazed when I found that these two trees from different sites had died the same year," Pringle said. "It was a victorious moment. And that 1699 date, almost the same as the 1700 earthquake date, just stopped me cold."

Despite the finding, however, the mystery of the landslide date remains unsolved. Although the tree-ring and lichen studies point to a slide date around 1700, the radiocarbon dates O'Connor obtained from the tree samples found at the World Forestry Center indicate that the trees died about 1500. "So now we have conflicting evidence," Pringle said. "We have our work cut out for us in trying to resolve these ambiguities from the different dating techniques."

Source: Richard Hill, 2002, Landslide Sleuths, from the Oregonian, Portland, Oregon, May 15, 2002, and presented on the U.S. Geological Survey Earthquake Hazards website, 2004.



Greenleaf Basin Rock Avalanche (2008) ...
"In January of 2008, a moderately large rock avalance landslide occurred on the southern portion of the Red Bluff scarp headwall (Greenleaf Basin Rock Avalanche)."


Source:    James R. Randall, 2012, Characterization of the Red Bluff Landslide, Greater Cascade Landslide Complex, Columbia River Gorge, Washington, Master of Science in Geology Thesis, Portland State University.

Image, 2004, Table Mountain from Bonneville Dam, North Bonneville, Washington click to enlarge
Click image to enlarge
Table Mountain and the Bonneville Landslide, Washington, as seen from Cascade Locks, Oregon. The western portion of Red Bluffs is visible on the right of Table Mountain. View from Thunder Island, Cascade Locks, Oregon. Image taken November 4, 2004.
Image, 2011, Table Mountain from Bonneville Dam, North Bonneville, Washington click to enlarge
Click image to enlarge
Table Mountain and the Bonneville Landslide, Washington, as seen from Cascade Locks, Oregon. The western portion of Red Bluffs is visible on the right of Table Mountain. View from Thunder Island, Cascade Locks, Oregon. Image taken May 20, 2011.

Note fresh January 2008 landslide scarp (Greenleaf Basin Rock Avalanche) on the left side of the western portion of Red Bluffs, right base of Table Mountain.


Ives, Pierce, and Hamilton Islands ...
Ives Island, Pierce Island, and Hamilton Island are all remnants of the Bonneville Landslide, while the uneroded portions produced the famous "Cascades of the Columbia." The cascades, or series of small waterfalls, produced by the slide provided the name for the Cascade Range.

Image, 2004, Pierce Island, click to enlarge
Click image to enlarge
Pierce Island, Washington. View from Beacon Rock boat dock. Image taken August 1, 2004.
Image, 2006, Ives Island from Hamilton Island, Washington, click to enlarge
Click image to enlarge
Ives Island from Hamilton Island, Washington. Image taken July 2, 2006.


Mosley Lakes Landslide ...
(to come)


Red Bluff Landslide ...
Abstract:

"Located in the Columbia River Gorge, the Red Bluff Landslide (18.8 km²) is one of four large landslides that make up the Cascade Landslide Complex. In its current form, the Red Bluff Landslide is a post-Missoula Flood feature made up of two components: an active upper lobe (8.6²) that is translational, creeping to the south at 25 cm/yr and spreading laterally to the east at 6 cm/yr over a semi-fixed portion (10.2 km²) of the Red Bluff Landslide area that has been "smoothed" by Missoula Floods. The upper active lobe is the landslide debris accumulated since Missoula Flood time (~15,000 yr.BP). Five separate collapse events have been identified and rock failures along the main scarp headwalls continue. Two rock avalanches on the Red Bluff Landslide were mapped. the Old Greenleaf Basin Rock Avalanche is estimated to have occurred 100 to 150 years ago, represents the fifth collapse event on the Red Bluff Landslide, and covers an area of 200,000 m². It has a volume of 4.2 million m³ its length is 748 m and has a width of 215 m. On January 3, 2008, the Greenleaf Basin Rock Avalanche occurred, flowing over the Old Greenleaf Basin Rock Avalanche, covering an area of 100,000 m² and deposited a volume of about 375,000 m³. Its length is 730 m with an average depth of 1.22 m. It contributed approximately 0.058% of the total volume and 0.01% of the surface area to the active upper lobe portion of the Red Bluff Landslide. The Greenleaf Basin Rock Avalanche was determined to be insignificant in the movement of the active part of the Red Bluff Landslide during the winter of 2007-2008. The original Cascade Landslide Complex map (Wise, 1961) included the Mosley Lakes Landslide which has now been removed because it lacked the characteristics of a landslide like scarp. The original complex (35.5 km²) has been renamed the "Greater Cascade Landslide Complex" (43.0 km²), with the addition of the adjacent Stevenson Slide and the elimination of the Mosley Lakes Landslide.


Source:    James R. Randall, 2012, Characterization of the Red Bluff Landslide, Greater Cascade Landslide Complex, Columbia River Gorge, Washington, Master of Science in Geology Thesis, Portland State University.


Image, 2003, Table Mountain and Greenleaf Peak, Washington, from Bonneville Dam, Oregon, click to enlarge
Click image to enlarge
Table Mountain and Greenleaf Peak, Washington, as seen from Bonneville Dam, Oregon. Image taken October 25, 2003.
Image, 2006, Greenleaf Peak, Washington, from Cascade Locks, Oregon, click to enlarge
Click image to enlarge
Columbia River, Red Bluffs, and Greenleaf Peak, Washington, as seen from Cascade Locks, Oregon. Image taken October 21, 2006.


Submerged Forest ...
The lake behind the temporary dam from the Bonneville Slide drowned a narrow forest of trees for 35 miles. About 1,800 of the stumps were visible in the river before they were again submerged in 1938 by the reservoir created by the Bonneville Dam.
[More]

Penny Postcard, ca.1920, Submerged Forest near Wind Mountain, Washington, click to enlarge
Click image to enlarge
Penny Postcard, Submerged Forest in the Wind Mountain, Washington, vicinity. Penny Postcard, ca.1920s, "Wind Mountain and Submerged Forest, Columbia River". #321, Chas. S. Lipschuetz Company, Portland, Oregon. In the private collection of Lyn Topinka.
Image, 2004, Wind Mountain and Collins Point, Washington, from Starvation Creek, Oregon, click to enlarge
Click image to enlarge
Wind Mountain and Collins Point, Washington, as seen from Starvation Creek State Park, Oregon. Image taken September 24, 2004.


From the Journals of Lewis and Clark ...

Clark, October 30, 1805 ...
A cool morning, a moderate rain all the last night, after eating a partial brackfast of venison we Set out [from their camp near Drano Lake and the Little White Salmon River]     passed Several places where the rocks projected into the river & have the appearance of haveing Seperated from the mountains and fallen promiscuisly into the river, Small nitches are formed in the banks below those projecting rocks which is comon in this part of the river, Saw 4 Cascades caused by Small Streams falling from the mountains on the Lard. Side,

[The possiblities in a two-mile area are - upstream to downstream - Starvation Creek and Falls, the seasonal Cabin Creek and Falls, Warren Creek and Falls, Wonder Creek and Lancaster Falls, Lindsey Creek and Falls, and Summit Creek and Falls.]

a remarkable circumstance in this part of the river is, the Stumps of pine trees [Submerged Forest]

[The Submerged Forest existed along the reach from above Dog Mountain/Viento Creek on the upstream edge and Wind Mountain/Shellrock Mountain on the downstream edge.]

are in maney places are at Some distance in the river, and gives every appearance of the rivers being damed up below from Some cause which I am not at this time acquainted with [Bonneville Landslide],     the Current of the river is also verry jentle not exceeding 1 1/2 mile pr. hour and about 3/4 of a mile in width. Some rain, we landed above the mouth of a Small river on the Stard. Side [Wind River] and Dined ...   :  here the river widens to about one mile large Sand bar in the middle, a Great [rock] both in and out of the water, large <round> Stones, or rocks are also permiscuisly Scattered about in the river, ...     The bottoms above the mouth of this little river [Wind River] <which we Call> is rich covered with grass & firn & is about 3/4 of a mile wide rich and rises gradually, below the river (which is 60 yards wide above its mouth) the Countery rises with Steep assent. we call this little river <fr Ash> New Timbered river from a Speces of Ash <that wood> which grows on its banks of a verry large and different from any we had before Seen, and a timber resembling the beech in bark <& groth> but different in its leaf which is Smaller and the tree smaller. passed maney large rocks in the river and a large creek on the Stard. Side in the mouth of which is an Island [Rock Creek near Stevenson, Washington], passed on the right of 3 Islands <on> near the Stard. Side, and landed on an Island close under the Stard. Side at the head of the great Shute [head of the Cascades Rapids], and a little below a village of 8 large houses on a Deep bend on the Stard. Side, and opposit 2 Small Islands imediately in the head of the Shute, which Islands are covered with Pine, maney large rocks also, in the head of the Shute. Ponds back of the houses, and Countrey low for a Short distance. The day proved Cloudy dark and disagreeable with Some rain all day which kept us wet. The Countary a high mountain on each Side thickly Covered with timber, Such as Spruc, Pine, Cedar, Oake Cotton &c. &c.     I took two men and walked down three miles to examine the Shute and river below proceeded along an old Indian path, passd. an old village at 1 mile [vicinity of Ice House Lake] ...     I found by examonation that we must make a portage of the greater perpotion of our Stores 2 1/2 miles, and the Canoes we Could haul over the rocks, I returned at Dark ...     a wet disagreeable evening, the only wood we could get to burn on this little Island on which we have encamped [near Ashes Lake, the island is now under the waters of the Bonneville Reservoir. Ashes Lake was near the head of the Cascade Rapids. Across from Ashes Lake is Cascade Locks, Oregon.] is the newly discovered Ash, which makes a tolerable fire. we made fifteen miles to daye





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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

Sources:    Hill, R., 1999, A New Look at an Old Landslide, from the Oregonian, Portland, Oregon, September 29, 1999, and reprinted in "Washington Geology, 2001, v.29, no.1, and also presented on the U.S. Geological Survey Landslides Hazards website, 2004;    Hill, R., 2002, Landslide Sleuths, from the Oregonian, Portland, Oregon, May 15, 2002, and presented on the U.S. Geological Survey Earthquake Hazards website, 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 State Division of Geology and Earth Resources Open-File Report 2004-7, March 2004;    Pringle, P., 2009, "The Bonneville Slide", IN: Columbia Gorge Interpretive Center Museum, "Explorations", downloaded April 2014;    Randall, J.R., 2012, Characterization of the Red Bluff Landslide, Greater Cascade Landslide Complex, Columbia River Gorge, Washington, Master of Science in Geology Thesis, Portland State University;    U.S. Forest Service website, 2004, Gifford Pinchot National Forest;   

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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November 2015