Lewis and Clark's Columbia River
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Lewis & Clark's Columbia River - "200 Years Later"
"Missoula Floods"
Includes ... Missoula Floods ... Lake Missoula ... Lake Lewis ... Lake Condon ... Lake Allison ... Columbia River Basalt Group (CRBG) ... Wallula Gap ...
Image, 2005, Wallula Gap from Juniper Canyon, Oregon, click to enlarge
Click image to enlarge
Wallula Gap, as seen from Juniper Canyon, Oregon. The waters of the Missoula Floods poured through the Wallula Gap thousands of years ago. Image taken September 25, 2005.


Glacial Lake Missoula and the Missoula Floods ...
Between 80,000 years ago and 10,000 years ago ice sheets called the "Wisconsin Glaciation" covered much of North America, including Northern Washington, Idaho, and Montana. Towards the end of this glaciation a large ice dam blocked the Clark Fork River in the Idaho Panhandle, creating "Glacial Lake Missoula". This lake was a massive lake 2,000 feet deep filling the valleys of western Montana. It stretched eastward more than 200 miles and, at its maximum height and extent, contained more than 500 cubic miles of water - more water than Lake Erie and Lake Ontario combined. Periodically, the ice dam would fail, resulting in a large catastrophic flood of ice- and dirt-filled water which rushed across northern Idaho and eastern and central Washington, down the Columbia River, through the Columbia River Gorge, and finally poured into the Pacific Ocean at the mouth of the Columbia River. Flood waters filled the Willamette River Valley, reaching Eugene, Oregon, more than 100 miles away. When Lake Missoula burst through the ice dam and exploded downstream, it did so at a rate 10 times the combined flow of all the rivers of the world.

"At the end of the last Ice Age, a finger of the Cordilleran ice sheet crept southward into the Idaho panhandle, forming a large ice dam that blocked the mouth of the Clark Fork River, creating a massive lake 2000 feet deep and containing more than 500 cubic miles of water. Glacial Lake Missoula stretched eastward for some 200 miles and contained more water than Lake Erie and Lake Ontario combined. When the highest of these ice dams failed, lake water burst through, shooting out at a rate 10 times the combined flow of all the rivers of the world.

This towering mass of water and ice literally shook the ground as it thundered toward the Pacific Ocean, stripping away hundreds of feet of soil and cutting deep canyons—”coulees”—into the underlying bedrock. With flood speeds approaching 65 miles per hour, the lake would have drained in as little as 48 hours.

Over time the Cordilleran ice sheet continued moving south and blocked the Clark Fork River again and again, recreating Glacial Lake Missoula. Over approximately 2,500 years, the lake, ice dam and flooding sequence was repeated dozens of times, leaving a lasting mark on the landscape.

... They carved out more than 50 cubic miles of earth, piled mountains of gravel 30 stories high, created giant ripple marks the height of three-story buildings, and scattered 200-ton boulders from the Rockies to the Willamette Valley. Grand Coulee, Dry Falls, Palouse Falls—all were created by these flood waters, as were the Missoula and Spokane ground-water resources, numerous wetlands and the fertile Willamette Valley and Quincy Basin."


Source:    U.S. National Park Service website, 2001, "Ice Age Floods", 2005, 2018.

Along the floodwaters’ path, more than 50 cubic miles of earth and rock were removed, transported, and much was deposited as new landforms. The floods built gravel bars as tall as 400 feet and moved boulders weighing many tons and deposited them high on the valley walls. Most of the eroded material was carried out onto the floor of the Pacific Ocean, where extensive deposits of flood sediment have been identified hundreds of miles from the current mouth of the Columbia River. According to Geologist Richard Waitt of the U.S. Geological Survey (1985), the various limits on the ice sheet and the floods suggests that Glacial Lake Missoula existed for 2,000 to 2,500 years between 15,300 and 12,700 years ago, creating more than 40 and maybe up towards 60 separate flood events.

"Quaternary deposits in the gorge are those of the cataclysmic Missoula (or Spokane) floods. The Cordilleran ice sheet from Canada advanced several times during the Pleistocene and covered parts of Washington, Idaho, and Montana. The ice formed dams on the Clark Fork River on the Idaho-Montana border and created glacial Lake Missoula. The lake covered 3,000 square miles of western Montana and held 600 cubic miles of water (Carson and Pogue, 1996).

The ice dams failed repeatedly releasing gigantic glacial floods that swept across northern Idaho, through the Spokane Valley, southwestward across eastern Washington, and down the Columbia River Gorge enroute to the Pacific Ocean (Carson and Pogue, 1996). The Missoula floods are the largest known floods on Earth in the last two million years; the flow of water was ten times the combined flow of all the rivers of the world. In eastern Washington, the floods created the Channeled Scablands, an area studied by J. Harlen Bretz in the 1920s. Bretz was the first person to describe these gigantic glacial floods.

The flood crest at Wallula Gap on the Columbia River at the Washington-Oregon border was about 1,200 feet as evidenced by glacial erratics that were left stranded on the hillside. The water poured down the Columbia Gorge and widened the valley by cleaning off all the soil and talus up to 1,000 feet elevation as far as The Dalles, Oregon. By the time it reached Crown Point, the surface of the last flood had dropped to about 600 feet elevation (Allen, 1979).

There may have been more than 40 major glacial floods (Waitt, 1980) recorded by bedded slack water deposits (rhythmites). The average interval between Missoula floods was about 30 years (Waitt and others, 1994). The last flood occurred 13,000 years ago."


Source:    David K. Norman and Jaretta M. Roloff, 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.


Flood Heights ...
Missoula Flood heights (measured and estimated elevations) as listed in Allen and Burns (1986):


Lake Lewis, Lake Condon, and Lake Allison ...
"Lake Lewis":   The constriction of Missoula Flood waters at the Wallula Gap created a backwater lake called "Lake Lewis". Lake Lewis covered more than 3,000 square miles of the Pasco and Quincy Basins, the Walla Walla River Basin, and the Lower Snake River.

"... up to 250 cubic miles of water and 50 cubic miles of ice and debris were trying to rush through this gap [Wallula Gap] all at the same time. The gap formed a hydrologic dam, a constriction that ponded water in back of it until it all could rush through. This became the first Missoula Flood lake formed in the lower Columbia River system. We call it Lake Lewis after Meriwether Lewis of the Corps of Discovery who came through the area in 1805 on the Lewis and Clark expedition." [Allen, et.al., 2009]

"Up to 264 cubic miles of water were ponded during each of the later, cleaner floods for perhaps a couple of weeks. These temporary lakes covered over 3,000 square miles of the Pasco and Quincy Basins, flooded the Yakima and Walla Walla River Valleys, and went 100 miles up the Snake River. Overall, Lake Lewis stretched about 120 miles from east to west and 60 miles from north to south. It probably was up to 800 feet deep at the Tri-Cities." [Allen, et.al., 2009]

"Lake Condon"   The constriction at The Dalles created "Lake Condon", which covered approximately 1,500 square miles from The Dalles to Umatilla.

"The Columbia River Gorge, starting at The Dalles, became the next hydrologic dam for the Missoula Flood waters, slowing down the flows and forming a second large lake that extended from Wallula Gap to The Dalles. It had a surface area of over 1,500 square miles and covered the present day Umatilla and The Dalles Basins. It rose to an elevation of over 1,000 feet and most likely reached to 1,100 feet (the height of the erosion lines in Wallula Gap). This lake was named to honor Thomas Condon, one of the great pioneers in geology in Oregon. During each flood, soft sediments and the upper basalt flows in the basin on either side of the river were eroded away and reworked in the initial flows." [Allen, et.al., 2009]

"Lake Allison":   The constriction at Kalama created a backwater lake, known as "Lake Allison". This lake filled the Willamette River Valley as far as Eugene, Oregon, over 100 miles away, with a measured height of 400 feet at Oregon City and an estimated height of 380 feet at Eugene. The area covered was approximately 3,000 square miles. The flood waters dumped thick layers of Palouse Silt, making the Willamette Valley one of the most fertile agricultural lands in the country.

"Each flood filled the Willamette Valley as far south as Eugene to nearly 400 feet in elevation, leaving deposits in the valley that consist of layered rhythmites known as Willamette Silt. The floods entered the Willamette Valley through the Oregon City Gap. More than 300 known groups of erratic boulders were dropped by melting icebergs around the margin of ephemeral Lake Allison. The floods also poured west through the Lake Oswego Gap into the Tualatin Valley, filling it to at least 350 feet elevation." [Allen, et.al., 2009]

"The Willamette Silt first described by Allison (1953) is a widespread deposit of bedded sand and silt which overlies several of the younger land surfaces above the flood plains of the present stream in the Valley. It varies in thickness from 150 feet at Newberg to 70 feet in Salem to 20 feet at Irish Bend (south of Corvallis) to a few feet at Eugene. It contains up to 50 rhythmites, like those found in the Walla Walla and Yakima Valleys of Washington. Oregonians can thank Washington for their rich soil in the Willamette Valley, for the Willamette Silts were originally Palouse Silts before the Missoula Floods transported them there." [Allen, et.al., 2009]

Image, 2005, Wallula Junction from Highway 730, click to enlarge
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Wallula Junction from Highway 730, Wallula Gap. Looking at the Port of Walla Walla between basalts of the Wallula Gap. The Wallula Gap constriction backed up the waters of the Missoula Floods creating "Lake Lewis". Image taken September 25, 2005.
Image, 2005, Columbia River upstream from Rowena Crest, click to enlarge
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Columbia River, looking upstream from Rowena Crest, Oregon. Rowena Crest is located within the "Rowena Gap" constriction of the Missoula Floods, backing waters up into "Lake Condon". Image taken September 18, 2005.
Image, 2018, Willamette River at Oregon City, Oregon, from Interstate 205, click to enlarge
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Willamette River at Oregon City, as seen from Interstate 205. Heading south on Interstate 205, looking at the "Oregon City Gap", a constriction along the Missoula Floods path entering the Willamette Valley. Image taken June 2, 2018.


Along the Flood Path



Columbia River Mile (RM) 329 ... Pasco Basin
Missoula Flood heights in Pasco were estimated at 1,250 feet (Allen and Burns, 1986).

Buttes located west of Richland are between 400 to 500 feet elevation.


Image, 2006, Columbia River from Kennewick, Washington, click to enlarge
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Sunset, Columbia River looking upstream, as seen from Kennewick, Washington. Image taken September 30, 2006.

Looking northeast towards Richland. Buttes in the background are between 400 to 500 feet in elevation.


RM 313 ... Wallula Gap
Many features along the Columbia River were impacted or created by the Missoula Floods. The Wallula Gap near the eastern end of the Columbia River restricted flood waters creating a temporary "Lake Lewis". Lake Lewis stretched back into the Yakima River Valley and covered the today's cities of Richland, Pasco, and Kennewick.

Missoula Flood heights at the Wallula Gap were measured at 1,250 feet (Allen and Burns, 1986).


Image, 2005, Wallula Gap as seen from Wallula, Washington, click to enlarge
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Wallula Gap as seen from upstream, from Wallula, Washington. The mouth of the Walla Walla River is visible on the left. Image taken September 25, 2005.
Image, 2003, Wallula Gap from downstream, click to enlarge
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Wallula Gap from downstream, from near Sand Station Recreation Area, Washington The flood crest at the Wallula Gap was about 1,200 feet as evidenced by glacial erratics left stranded on the hillsides. View from downstream from a pullover on Highway 730, just east of Sand Station Recreation Area, Oregon. Image taken September 29, 2003.


RM 313 ... Twin Sisters (Two Sisters), Oregon
Twin Sisters (also seen as "Two Sisters") is the remnant of a Columbia River basalt flow scoured by the Missoula Floods.

The U.S. National Elevation Dataset (2018) lists the Twin Sister's elevation at 449 feet.

The Missoula Flood waters were over 1,200 feet at this point.


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


RM 298 ... Hat Rock and Boat Rock, Oregon
Downstream from the Wallula Gap is Hat Rock, a 70-foot-high basalt feature created by the eroding waters of the Missoula Floods. Hat Rock and nearby Boat Rock are located off U.S. Highway 730, nine miles upstream of Umatilla, Oregon, at Columbia River Mile (RM) 298.

Lewis and Clark passed Hat Rock on October 19, 1805, and gave it it's name.

"... SW. 14 miles to a rock in a Lard. resembling a hat just below a rapid at the lower Point of an Island in the Midl: of the river ..." [Clark, October 19, 1805, first draft]

The U.S. National Elevation Dataset (2018) lists Hat Rock's elevation at 469 feet and Boat Rock's elevation at 509 feet. The Missoula Flood waters were over 1,200 feet at this point.


Image, 2004, Hat Rock, Oregon, click to enlarge
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Hat Rock, Oregon. Hat Rock is a remnant of a Columbia River Basalt flow, eroded during the Missoula Floods. Image taken September 24, 2004.

"... a rock in a Lard. resembling a hat just below a rapid at the lower Point of an Island in the Midl: of the river ..." [Clark, October 19, 1805, first draft]
Image, 2004, Boat Rock, Oregon, click to enlarge
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Boat Rock, Oregon. Image taken September 24, 2004.


RM 292 ... Umatilla
Missoula Flood heights at Umatilla, Oregon, were estimated at 1,210 feet (Allen and Burns, 1986).


RM 243 ... Arlington
Missoula Flood heights at Arlington, Oregon, estimated at 1,180 feet (Allen and Burns, 1986). Arlington lies at the mouth of Alkali Canyon.


RM 243, RM 239.5, RM 234, and RM 227.5 ... Alkali Canyon, Jones Canyon, Blalock Canyon, and Philippi Canyon
Flood waters of Lake Condon of the Missoula Floods spilled over the southern bank of the Columbia River and headed south through Alkali Canyon (RM 243), Jones Canyon (RM 239.5), Blalock Canyon (RM 234), and Philippi Canyon (RM 227.5). The waters rushing through Alkali Canyon flowed to Rock Creek to the John Day River and then northwest along the John Day River drainage back to the Columbia River (RM 217). The waters flowing up Jones, Blalock, and Philippi Canyons created a scabland before entering the John Day River drainage.

SPILLWAYS INTO THE JOHN DAY CANYON

"Hodge (1931) recognized more than 50 years ago that floodwaters had overtopped the low divides between the Columbia River and the headwaters of Rock Creek, as well as the divide directly into the John Day Canyon. The floodwater poured up Alkali Canyon, south of Arlington (Oregon 19), and scoured a channel westward (now occupied by the Union Pacific RR branch line) into Rock Creek 6 miles above its junction with the John Day River. Farther west, the Floods poured up Jones Canyon, Blalock Canyon, and Phillip Canyon just east of Quinton, where it formed several square miles of scabland and left a high-perched expansion bar on the east wall of the John Day Canyon 10 miles from its mouth. A sixth small spillway lies at 1020 feet elevation, 2 miles northwest of Phillipi Canyon."


Source:    John Eliot Allen and Marjorie Burns, with Sam C. Sargent, 1986, Cataclysms on the Columbia: Timber Press, Portland, Oregon



RM 218 ... John Day River
Missoula Flood heights at the mouth of the John Day River, located at Columbia River Mile (RM) 218, were measured at 1,140 feet (Allen and Burns, 1986).

"The Nook", rising over 1,000 feet above the waters of Lake Umatilla, is the high point on the right bank of the John Day River. The U.S. National Elevation Dataset (2018) lists it's elevation at 1,270 feet. During maximum Missoula Flood height, only the top 130 feet of The Nook's top was above water.

The height of the Lake Umatilla pool (the reservoir behind the John Day Dam) is 268 feet (full pool, U.S. Army Corps of Engineers, 2018).


Image, 2004, Mouth of the John Day River from Washington State Highway 14, click to enlarge
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Lake Umatilla, the reservoir behind the John Day Dam, looking towards the mouth of the John Day River. "The Nook" is the high point on the John Day's right bank (left in image). View from Washington State Highway 14. Image taken April 24, 2004.


RM 216 ... John Day Dam Gap
As Lake Condon backed up behind behind a constriction near The Dalles (Allen, et.al., 2009), flood waters were also making it through a smaller constriction just downstream of the John Day Dam. This constriction has been called the "John Day Dam Gap" (Allen and Burns, 1986).

Missoula Flood heights at the John Day Dam Gap, were measured at 1,130 feet (Allen and Burns, 1986). Two miles upstream lies the mouth of the John Day River where Missoula Flood heights were measured at 1,140 feet (Allen and Burns, 1986).

According to Allen, et.al. (2009):

"The Columbia River, four miles below the mouth of the John Day, passes through a narrows, now the site of the John Day Dam. ... The floodwaters flowing through these narrows and draining Lake Condon moved at a rate of up to 40 miles per hour." [Allen, et.al., 2009]

Image, 2012, John Day Dam from Washington State Highway 14, click to enlarge
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John Day Dam as seen from Washington State Highway 14. Image taken June 6, 2012.

John Day Dam, Lake Umatilla, and the John Day River (drainage furthest left). This area is just upstream of a constriction which slowed Missoula Flood waters of Lake Condon.


RM 210 and RM 205 ... Stonehenge and Maryhill Museum
Washington State's Stonehenge Memorial and Maryhill Museum sit on a bench cut into the north wall of the Columbia Hills by the Missoula Floods. In places this bench is nearly one mile wide.

According to Allen, et.al. (2009):

"A high bench up to a mile wide was cut into the north wall of the [Columbia River] canyon on which Maryhill Museum and the Stonehenge Monument now rest. Several large ice-rafted erratics have been found here above 800-feet elevation, one of them at 860 feet." [Allen, et.al., 2009]

According to Norman, et.al. (2004):

"Maryhill Museum sits on a bench of nearly flat-lying lava flows of the 14.5-million-year-old Priest Rapids Member of the Wanapum Basalt." [Norman, et.al, 2004]

The U.S. National Elevation Dataset (2018) lists Stonehenge's elevation at 561 feet and Maryhill Museum's elevation at 774 feet.


Image, 2004, Stonehenge Memorial sitting on the banks of the Columbia River, click to enlarge
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Stonehenge Memorial, Maryhill, Washington, perched on the banks of the Columbia River. Image taken April 24, 2004.
Image, 2005, Maryhill Museum, Washington, as seen from Interstate 84, Oregon, click to enlarge
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Maryhill Museum and the Columbia Hills, Washington, as seen from Interstate 84, Oregon. Maryhill Museum sits on a large bench carved by the Missoula Floods. Image taken September 24, 2005.


RM 204 ... Deschutes River
Missoula Flood heights at the mouth of the Deschutes River, Oregon, were measured at 1,070 feet (Allen and Burns, 1986).


RM 203 ... Miller Island
Missoula Flood gravels lie at the downstream (south/southwestern) end of Miller Island. (O'Connor, et.al., 2009)

Image, 2004, Miller Island, downstream tip, click to enlarge
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Miller Island, Washington, from downstream on Washington State Highway 14. Image taken April 24, 2004.
Image, 2004, Miller Island from road to the Deschutes, click to enlarge
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Miller Island, Washington. View is the downstream side of Miller Island as seen from road leading to the mouth of the Deschutes River, Oregon. Image taken March 20, 2004.


RM 200 ... Fairbanks Water Gap
The Fairbanks Water Gap was created when flood waters from the Missoula Floods "jumped banks" and flowed through the gap into Fifteenmile Creek, eight miles east of The Dalles, Oregon.

Image, 2011, Avery Park, Washington, and Fairbanks Water Gap, Oregon, click to enlarge
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Avery Park, Washington, with Fairbanks Water Gap, Oregon. Waters from the Missoula Floods flowed through the Fairbanks Water Gap into Fifteenmile Creek, east of The Dalles, Oregon. Image taken September 28, 2011.


RM 194 ... Horsethief Butte
The great floods of the last ice age carved the basalts of Horsethief Butte and the surrounding Columbia River channel, creating the features we see today. The basalts themselves were created thousands of years earlier when a series of lava flows emerged from cracks in the earth's crust and blanketed the entire eastern Washington and northern Oregon region. Horsethief Butte is made up of a series of lava flows, visible in the cliffs.

Missoula Flood heights at the Ortley Gap (Columbia Hills) were measured at 1,000 feet (Allen and Burns, 1986).

The U.S. National Elevation Dataset (2018) lists Horsethief Butte's elevation at 492 feet.


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.


RM 189 ... The Dalles
Missoula Flood heights at The Dalles, Oregon, were estimated at 1,000 feet (Allen and Burns, 1986).

The Missoula Floods kolk pond behind the Columbia Gorge Discovery Center was formed by "strong Floods whirlpools plucking out the bedrock" (IAFI Field Trip Guide).


Image, 2018, Kolk pond at Columbia Gorge Discovery Center, click to enlarge
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Kolk lake, Columbia Gorge Discovery Center, The Dalles, Oregon. The lake is a remnant of the Missoula Floods. Image taken June 6, 2018.


RM 186 ... Turbulence-cut Bench Lines
Turbulent Missoula Flood waters rushing into the Rowena Gap created bench lines visible on the Washington banks of the Columbia River, and can be seen from the Columbia Gorge Discovery Center, located downstream from The Dalles, Oregon.

According to the Ice Age Floods Institute (2018):

"... from this viewpoint [Columbia Gorge Discovery Center] a few thin horizontal benches can be seen on the gently dipping hillsides across the river. These benches are also thought to have been cut by turbulent flood waters rushing into Rowena Gap." [Ice Age Floods Institute, 2018]

Image, 2013, Missoula Flood Bench Lines, click to enlarge
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Turbulence-cut Bench Lines (horizontal thin lines left, middle of bank). Washington side of the Columbia River at Columbia River Mile 186 and seen from road past the Columbia Gorge Discovery Center, The Dalles, Oregon. Image taken May 8, 2013.


RM 185 to RM 181 ... Rowena Gap
The Columbia River passes through the Ortley Anticline at Rowena Gap, a major constriction in the path of the Missoula Floods. Flood waters backed up for miles upstream and an eddy bar developed downstream.

According to Allen, et.al, (2009):

"Between The Dalles and Hood River, soil and talus were swept from the valley walls, leaving the series of clean steps we now see on the barren lava flows of Columbia River Basalt. ... The almost vertical 600-foot-high cliffs here were overtopped by at least 200 feet of water which cleaned off much of the overlying The Dalles Formation." [Allen, et.al., 2009]

Image, 2004, Rowena Gap, Washington side, from Mayer State Park, Oregon, click to enlarge
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Rowena Gap basalts, Washington side, view from Mayer State Park, Oregon. The Rowena Gap is where the Columbia River carved a channel through the Ortley Anticline. Image taken November 11, 2004.

View of oversteepened cliffs in the basalt flows north of the Columbia River, eight miles west of The Dalles, and just west of the Ortley fold and water-gap. The flood crest line lies at the top of the highest cliff. Above this elevation the soil has not been stripped off by the floods. A modern highway and railroad now skirt the river. [Allen and Burns, 1986]


RM 181 ... Kolk Pond, Mayer State Park
A "kolk lake" or "kolk pond" is a lake/pond filling a depression scoured away by the churning flood waters. A good example can be seen at Mayer State Park, easily accessible from Interstate 84.

Image, 2005, Rowena Gap, Washington side, from Rowena Crest, Oregon, click to enlarge
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Mayer State Park, the Columbia River, and Washington's Rowena Gap basalts, as seen from Rowena Crest, Oregon. Image taken September 18, 2005.

The "kolk pond" in the foreground is a remnant of the Missoula Floods.


RM 180 ... Klickitat River and Lyle
Stratigraphy in exposures of eddy deposits northwest and across the Klickitat River from Lyle show that many of the several floods passing by achieved stages of 600 feet. The community of Lyle is built on a huge Missoula Floods gravel bar.

Image, 2008, Lyle, Washington, from Rowena Crest, Oregon, click to enlarge
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Lyle, Washington, from Rowena Crest, Oregon. Image taken August 23, 2008.


RM 180 ... Rowena Crest
Rowena Crest sits at an elevation of 720 feet and was stripped of its pre-Missoula-flood surface. Estimates give a 960 +/- 40 feet water elevation.

According to Allen and Burns (1986):

"Between The Dalles and Hood River, soil and talus were swept from the valley walls, leaving the series of clean steps we now see on the barren lava flows of Columbia River Basalt. At many places the accumulations of talus, which one would expect to see after 15,000 years at the base of the cliffs, have yet to form substantial slopes. Just west of Mayer State Park (US 30), the river makes an abrupt turn to the north. This change in the course of the floods caused the cliffs to be undermined so extensively that a great landslide developed, down which the Scenic Highway swings in a series of turns (Rowena Loops)." [Allen and Burns, 1986]

Image, 2006, Rowena Crest and Interstate 84, click to enlarge
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Rowena Crest and Interstate 84, Oregon. View from moving car on Interstate 84 heading west. Image taken October 2, 2006.
Image, 2005, Rowena Loops, click to enlarge
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Rowena Loops, Historic Columbia River Highway, Oregon. View from Rowena Crest, looking at the upper loop on the landslide block. Image taken September 18, 2005.


RM 180 ... Mima Mounds
"Mima mounds" can be seen on some of the basalt benches left by the Missoula Floods and covered with flood deposits.

According to Allen, et.al. (2009):

"The almost vertical 600-foot-high cliffs here were overtopped by at least 200 feet of water, which cleaned off much of the overlying The Dalles Formation and left several scabland channels, one of them by the highway containing a small kolk lake. Deposits of sands and gravels from the Missoula Flood waters were spread across the top of this plateau where today one can visit the Rowena Overlook and Tom McCall State Park. In the last 15,000 years, these sand and gravel deposits have been shaped into mima mounds. These deposits are about 30 feet across and five feet high and rest on the barren basalt bedrock." [Allen, et.al., 2009]

Image, 2007, View upstream from Rowena Crest, Oregon, click to enlarge
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View downstream from Rowena Crest, Oregon. Image taken May 13, 2007.
Image, 2010, Columbia River from Tom McCall Nature Preserve, Oregon, click to enlarge
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Columbia River as seen from Tom McCall Nature Preserve, Oregon. Image taken March 6, 2010


RM 180 ... Tom McCall Nature Preserve
The Tom McCall Nature Preserve and nearby Rowena Crest are located on a high basalt mesa known as the "Rowena Plateau". During the end of the last ice age over 200 feet of raging flood waters (today known as the Missoula Floods) ripped across this plateau stripping it clean. Over the next ten thousand years this surface was covered by 3 to 4 feet of loess (wind blown ash, most likely from nearby Mount St. Helens volcano) which eventually eroded into the mounds. These mounds, wildflower-covered in the spring, dot the surface of the basalt flow. They are commonly referred to as "biscuit mounds" or "biscuit scabland".

The Missoula Floods also left behind small rounded depressions in the basalts which eventually filled with water and are now called "kolk lakes". The trails at Tom McCall pass by two such lakes.


Image, 2009, Tom McCall Nature Preserve, Oregon, click to enlarge
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Rowena Plateau, Tom McCall Nature Preserve, Oregon, with the Columbia River. Gold Stars dot the hillside. Image taken April 4, 2009.
Image, 2007, Tom McCall Nature Preserve, Oregon, click to enlarge
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Loess mounds, Rowena Plateau, Tom McCall Nature Preserve, Oregon. Image taken May 13, 2007.
Image, 2007, Tom McCall Nature Preserve, Oregon, click to enlarge
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Kolk Lake, Rowena Plateau, Tom McCall Nature Preserve, Oregon. Image taken May 13, 2007.


RM 175 ... Mosier
At Mosier, Oregon, Missoula flood waters spilled over the divide from the Columbia River to Mosier Creek. West of town are nice examples of a glacial erratic and a Missoula Flood eddy bar.

According to Waitt, et.al., (2009):

"West of The Dalles and Rowena Gap we pass the town Mosier in a sysclinal valley. Like the bars at Petersburg and Fairbanks, Missoula flood flow spilling over a divide from Columbia River to Mosier Creek deposited a large delta of southwest-dipping foresets of cobble-pebble gravel and sand." [Waitt, et.al., 2009]

Image, 2018, Glacial erratic in gravel pit, Mosier, Oregon, click to enlarge
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Glacial erratic, Mosier, Oregon. Image taken June 6, 2018.
Image, 2018, Glacial erratic in gravel pit, Mosier, Oregon, click to enlarge
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Glacial erratic, Mosier, Oregon. Image taken June 6, 2018.

The Mosier erratic most likely was rafted in from Canada, is 6x8x12 feet in size, and weighs between 30 to 40 tons.


RM 171 ... Bingen Gap
The Bingen Gap is a constriction in the Columbia River where the Columbia crosses the Bingen Anticline.


RM 170 ... White Salmon
According to O'Connor and Burns (2009):

"From Hood River east, marks of the Missoula floods become evident; the town of White Salmon (Washington side) sits atop a large gravel bar, with scrubbed hillslopes flanking the upstream constriction." [O'Connor and Burns, 2009]

According to Waitt, et.al., (2009):

"The north-side town of White Salmon is built upon a large pendant bar in the lee of Bingen Gap. One of the larger bars in [the] Columbia Gorge." [Waitt, et.al., 2009]

[More]


Image, 2011, White Salmon from Hood River, click to enlarge
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White Salmon, Washington, on the ridge, as seen from Hood River, Oregon. View from moving car. Image taken August 22, 2011.


RM 169 ... Hood River
The Hood River Valley, Oregon was inundated by backwater from the Missoula Floods, with flood deposits reaching above 800 feet, and some ice-rafted erratics thought to be Missoula Flood erratics being found between 840 and 880 feet. As the waters receded massive deposits of sand, gravel, and debris were left behind forming a rich valley soil which today supports Hood River's famous fruit orchards.

Missoula Flood heights at Hood River, Oregon, were estimated at 925 feet (Allen and Burns, 1986).

Missoula flood deposits form a late Pleistocene capping of sand and silt as thick as 30 meters [100 feet] in some parts of the Hood River Valley (Scott, et.al., 1997).

According to D.K. Norman, et.al. (2004):

"The Hood River Valley was inundated by backwater from the Missoula floods. Newcomb (1969) reported "fine-grained lacustrine deposits" as high as 800 feet, probably slackwater deposits of Missoula floods. The highest ice-rafted erratics in the Hood River Valley are betwen 840 and 880 feet. If this was the maximum stage achieved by the largest flood, the water surface dropped substantially through Bingen Gap (O'Connor and Waitt, 1994)." [Norman, et.al., 2004]

According to Waitt, et.al., (2009):

"Backwater from the Missoula floods inundated Hood River valley, where Newcomb (1969) reported "fine-grained lacustrine deposits" as high as 245 meters (800 feet). High ice-rafted erratics in the Hood River valley lie between 255 and 270 meters (840-880 feet) altitude. If this was the maximum stage achieved by the largest flood, the water surface dropped substantially through Bingen Gap." [Waitt, et.al., 2009]

"The best examples of polished, fluted, and scoured basalt surfaces known at high level in [the] Columbia Gorge are riverward of the Columbia River Gorge Hotel, a 1921 structure on the National Historic Register." [Waitt, et.al., 2009]

Image, 2016, Hood River Valley, Oregon, click to enlarge
Click image to enlarge
Mount Hood and the Hood River Valley, Oregon. View looking south/southwest from Panorama Point. Image taken April 6, 2016.

Missoula Flood deposits lined the banks of the Hood River, leaving behind vast areas of rich soil. These deposits now support the famous Hood River orchards.
Image, 2015, Ruthton Park basalt, Hood River, Oregon, click to enlarge
Click image to enlarge
Ruthton Park basalt cliff, Hood River, Oregon. Image taken April 9, 2015.

"The best examples of polished, fluted, and scoured basalt surfaces known at high level in [the] Columbia Gorge are riverward of the Columbia River Gorge Hotel, a 1921 structure on the National Historic Register." [Waitt, et.al., 2009]


RM 166 ... Ruthton Point
According to the 2012 U.S. Geological Survey's "Digital Geologic Map of the Hood River Valley" (OFR O-12-03), Missoula Flood deposits are located on the southeast side of Ruthton Point, providing rich soil for farming.

Image, 2006, Columbia River and Ruthton Point as seen from Ruthton Park, click to enlarge
Click image to enlarge
The Columbia River and Ruthton Point, Oregon, as seen from Ruthton Park. Mitchell Point is on the left. Image taken September 29, 2006.


RM 160 ... Dog Mountain Gap
Missoula Flood heights at the Dog Mountain Gap (Dog Mountain, Washington), were measured at 875 feet (Allen and Burns, 1986).


RM 142 ... Beacon Rock
Beacon Rock is a large 840-foot-high basalt plug. The Missoula Floods eroded away the softer outer material.

Image, 2010, Beacon Rock, Washington, click to enlarge
Click image to enlarge
Beacon Rock and Hamilton Mountain, Washington. Beacon Rock is a large 840-foot-high basalt plug. The Missoula Floods eroded away the softer outer material View from Beacon Rock boat dock. Image taken November 2, 2010.


RM 136 ... Multnomah Falls
The 620-foot-high cliff at Multnomah Falls was enhanced when flood waters of the Missoula Floods eroded away softer material, highlighting the spectacular cliff face.

Imag5, 2005, Multnomah Falls, Oregon, Benson Bridge, click to enlarge
Click image to enlarge
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.


RM 129 ... Crown Point
The 700-foot-high Crown Point was inundated during peak floods.

Missoula Flood heights at the Crown Point Gap, were measured at 700 feet (Allen and Burns, 1986).


Image, 2006, Crown Point from Chanticleer Point, Oregon, click to enlarge
Click image to enlarge
Crown Point, Oregon, as seen from Chanticleer Point, 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. The 700-foot-high feature was covered by waters of the Missoula Floods. Image taken September 23, 2006.


RM 120 ... Troutdale
Troutdale, Oregon, is the easternmost entrance to the Willamette Valley.

Missoula Flood heights at Troutdale, were estimated at 540 feet (Allen and Burns, 1986).



RM 120 to RM 102 ... Willamette River Valley
"As the floods emerged from the Gorge at Crown Point Gap which is only two miles wide, they crested above the Vista House at over 700-feet elevation, then plunged down within about three miles to 550-feet elevation, with a width of about five miles. ...

Spreading out in the broad Portland-Vancouver Basin, the crests dropped abruptly to about 400-feet elevation, which still left only the tops of Rocky Butte and Mount Tabor above each flood. Only the tops of Portland's highest buildings today would have protruded from the floodwaters if they had been present.

Again restricted in their flow to the sea by the narrows north of Portland at Kalama, the floods continued south to fill the Tualatin Valley through the Oswego Gap and the Willamette Valley through the Oregon City Gap as far south as Eugene, ponding in the valley to form Lake Allison."


Source:    John Eliot Allen, Marjorie Burns, and Scott Burns, 2009, "Cataclysms on the Columbia: The Great Missoula Floods", Ooligan Press.

[More]



Willamette River Valley, Rocky Butte ...

Rocky Butte stood in the path of the Missoula Floods. The rushing flood waters heading down the Willamette Valley eroded the land on the upstream side of the Butte, similar to how a stream erodes the sediment on the upstream side of a rock in its path. Today on the east side of Rocky Butte, Interstate 205 and Interstate 84 follow the broad channels carved by the floods.

According to Scott (1997):

"... Rocky Butte, an early Pleistocene basaltic andesite volcano of the Boring Lava. ... During peak flows of the latest Pleistocene Missoula floods, high velocities and turbulence induced by the submerged butte eroded huge scour pits on its upstream side; downstream, gravel bars many kilometers long were deposited. I-84 curves around the south and east sides of the butte in scour pits." [Scott, 1997, Geologic History of Mount Hood Volcano, Oregon, USGS Open-file Report 97-263]

Image, 2006, Rocky Butte, Oregon, and Interstate 205, from the south, click to enlarge
Click image to enlarge
Rocky Butte, Oregon, and Interstate 205. View from the south. Image taken February 19, 2006.
Image, 2004, Rocky Butte, Oregon, from the south, click to enlarge
Click image to enlarge
Rocky Butte, Oregon, as seen from Interstate 205. View from Interstate 205 heading north. Image taken July 4, 2004.


Willamette River Valley, Oregon City Water Gap ...

As Missoula Flood waters rushed down the Columbia River Valley they reached the Kalama Gap constriction at Columbia River Mile 71. The area behind the construction filled with water creating "Lake Allison". Waters of Lake Allison flowed south entering the Willamette Valley through the Oregon City and Lake Oswego Water Gaps, and eventually reached as far south as Eugene, Oregon, over 100 miles south of the Columbia River.


Image, 2018, Willamette River at Oregon City, Oregon, from Interstate 205, click to enlarge
Click image to enlarge
Willamette River at Oregon City, as seen from Interstate 205. Heading south on Interstate 205, looking at the "Oregon City Gap", a constriction along the Missoula Floods path entering the Willamette Valley. Image taken June 2, 2018.


Willamette River Valley, Missoula Flood Deposits ...

"Each flood filled the Willamette Valley as far south as Eugene to nearly 400 feet in elevation, leaving deposits in the valley that consist of layered rhythmites known as Willamette Silt. ...

The Willamette Silt first described by Allison (1953) is a widespread deposit of bedded sand and silt which overlies several of the younger land surfaces above the flood plains of the present streams in the Valley. It varies in thickness from 150 feet at Newberg to 70 feet in Salem to 20 feet at Irish Bend (south of Corvallis) to a few feet at Eugene. ...

Oregonians can thank Washington for their rich soil in the Willamette Valley, for the Willamette Silts were originally Palouse Silts before the Missoula Floods transported them there."


Source:    John Eliot Allen, Marjorie Burns, and Scott Burns, 2009, "Cataclysms on the Columbia: The Great Missoula Floods", Ooligan Press.


Image, 2018, Willamette Valley, click to enlarge
Click image to enlarge
Iris fields, Willamette Valley Missoula Flood deposits, as seen from Interstate-5 heading south. View from south of Newberg and north of Salem. Image taken June 2, 2018.


Willamette River Valley, Granitic Erratic, Multnomah County ...

As of June 2003, the U.S. Geological Survey's Missoula Flood Glacial Erratic database contained "records of 400 glacial erratics and their locations; however, approximately 28 of these locations are thought to be duplicates". [Minervini, et.al., 2003, USGS OFR-03-408]


Image, 2014, Granitic Erratic, Lewis and Clark College, Portland, Oregon, click to enlarge
Click image to enlarge
Granitic Erratic, Lewis & Clark College, Multnomah County, Portland, Oregon. Image taken August 24, 2014.
Image, 2014, Granitic Erratic, Lewis and Clark College, Portland, Oregon, click to enlarge
Click image to enlarge
Granitic Erratic, Lewis & Clark College, Multnomah County, Portland, Oregon. Image taken August 24, 2014.
Image, 2014, Granitic Erratic, Lewis and Clark College, Portland, Oregon, click to enlarge
Click image to enlarge
Granitic Erratic, Lewis & Clark College, Multnomah County, Portland, Oregon. Image taken August 24, 2014.

A GRANITIC ERRATIC
CARRIED BY AN ICE-BERG
AT THE END OF THE LAST
ICE AGE FROM THE UPPER
COLUMBIA RIVER BASIN
TO NEAR THIS POINT.


Willamette River Valley, Glacial Erratic, Yamhill County ...

The "Sheridan Erratic", often called the "Bellevue Erratic", is located on the west side of the Willamette Valley, just off of Oregon Highway 18, and halfway between the Oregon communities of Sheridan and McMinnville. According to Dr. Jim O'Connor in an interview with the Yamhill Valley News-Register" (2005):   "the 90-ton rock, which sits atop a rise about a half mile from the site entrance, probably came in on an iceberg around 15,000 years ago, transported by one of the Missoula floods, the biggest known fresh water floods in history. The erratic rock is at an elevation of 300 feet and the floods probably topped that by 100 feet." The News-Register goes on to say:   "More than 400 ice-rafted rocks have been identified along the flood plain ... they are different in composition from the local bedrock, thus are called "erratic" and the one near Sheridan is the largest known glacial erratic in the Willamette Valley." Geologically the rock is an argillite boulder from Canada and is believed to be 600 million years old. It was originally part of the sea-floor. It once weighed 160 tons and measured nearly 21 x 18 x 5 feet. Today the boulder sits in many pieces with the largest being nearly 18 x 13 x 5 feet, and weighs in at 90 tons. Vandalism and souvenier hunters have taken the rest.


Image, 2013, Glacial Erratic, McMinnville, Oregon, click to enlarge
Click image to enlarge
Glacial Erratic, McMinnville, Oregon. Image taken January 11, 2013.


RM 120 to RM 80 ... Vancouver Basin
"From Crown Point Gap, the water poured northwestward across the present sites of Washougal and Camas with a depth of nearly 500 feet. It swept up the Washougal and Little Washougal valleys and across the divide past Woodburn Hill north of Washougal into the valley of Lacamas Creek, where it was joined by similar torrent that had surged up Lacamas Creek, scouring out the kolk depression now occupied by Lackamas Lake. Only the upper 100 feet of Woodburn Hill and the upper 200 feet of the higher Prune Hill, west of Camas, stood above the waters. The entire Vancouver plains surface was inundated as far north as Woodland, 35 miles to the northwest, covering over 275 square miles of the basin in Washington."


Source:    John Eliot Allen, Marjorie Burns, and Scott Burns, 2009, "Cataclysms on the Columbia: The Great Missoula Floods", Ooligan Press.


RM 120 ... Lacamas Lake and Round Lake
Lacamas Lake and Round Lake, located just north of Camas, Washington, are two kolk lakes which lie within a Missoula Flood trough created as the massive floods left the Columbia Gorge and surged west, reaching the Kalama Gap constriction, and backing flood waters over the Vancouver Basin and the Willamette Valley.

According to Evarts and O'Connor (2008):

"In latest Pleistocene time, huge Columbia River floods from glacial Lake Missoula inundated the Portland Basin, eroding channels such as the Lacamas Lake trough but also leaving immense bars of sand and gravel and a blanket of sand, silt, and clay in slack water areas." [Evarts and O'Connor, 2008]

According to Allen, et.al. (2009):

"From Crown Point Gap, the water poured northwestward across the present sites of Washougal and Camas with a depth of nearly 500 feet. It swept up the Washougal and Little Washougal valleys and across the divide past Woodburn Hill north of Washougal into the valley of Lacamas Creek, where it was joined by similar torrent that had surged up Lacamas Creek, scouring out the kolk depression now occupied by Lackamas Lake. Only the upper 100 feet of Woodburn Hill and the upper 200 feet of the higher Prune Hill, west of Camas, stood above the waters. The entire Vancouver plains surface was inundated as far north as Woodland, 35 miles to the northwest, covering over 275 square miles of the basin in Washington." [Allen, et.al., 2009]

Image, 2018, Lacamas Lake, Washington, click to enlarge
Click image to enlarge
Lacamas Lake, Camas, Washington. View looking northwest. Image taken June 11, 2018.
Image, 2009, Round Lake, Washington, click to enlarge
Click image to enlarge
Fishing, Round Lake, Washington. View looking northwest. Image taken April 29, 2009.


RM 118 ... Prune Hill
Prune Hill, a Boring Lava cone, has a high point of 751 feet. Only the upper 200 feet of Prune Hill stood above the Missoula Flood waters. (Allen, et.al., 2009)

Image, 2004, Prune Hill, Washington, from Chinook Landing, Oregon, click to enlarge
Click image to enlarge
Prune Hill, Washington, from Chinook Landing, Oregon. Lady Island is the low trees in the middleground. Image taken October 11, 2004.


RM 117 to RM 111 ... Mill Plain Bar
According to Allen, et.al. (2009):

"As the floodwaters hit Prune Hill (a Boring Lava volcano to the west of Camas), a large pendant bar formed in back of it and extends over five miles to the west. Prune Hill acted like a boulder in the streambed, slowing down the flow, especially downstream, and allowing the load of the water to deposit sediment. (Humans have been mining sediment from Mill Plain Pendant Bar for over 100 years)." [Allen, et.al., 2009]

According to Evarts (2006):

"Mill Plain [east Vancouver, Washington] is the surface of a huge bar deposited by the floods in the lee of Prune Hill at Camas ... These deposits, as thick as 40 meters [130 feet] or more, were apparently deposited by multiple floods (Waitt, 1996). Similar gravel accumulated as a fan west of Proebstel, where floodwaters discharged northwestward through the trough now occupied by Lacamas Lake (Trimble, 1963; Waitt, 1994). Before the floods, Lacamas Creek probably flowed westward to Burnt Bridge Creek but was diverted sharply southeastward to Lacamas Lake by the fan near Proebstel. Well logs indicate that the gravel grades northward to predominantly sand near Hockinson." [Evarts, 2006]

The Vancouver and Orchards Geologic Map Quadrangle (O'Connor, et.al., 2016), the Camas Quadrangle Geologic Map (Evarts and O'Connor, 2008) and the Washougal Quadrangle Geologic Map (Evarts, et.al., 2013) describe the composition and depth of the Missoula flood gravel deposits.

Vancouver and Orchards Quadrangles:
"Gravel facies -- Unconsolidated, gray, stratified, bouldery to cobbly gravel and sand, deposited in thick sheets over older basin-fill deposits on upland areas flanking the Columbia River; organized into prominent, large bar-and-channel complexes on Mill Plain and Fourth Plains. On uplands of Mill Plain and Fourth Plains in the eastern area [map extends to NE 164th], several quarries show more than 59 feet of crudely stratified and poorly sorted coarse gravel and sand, commonly deposited in tall (locally >16 feet), steeply dipping (as much as 35 degrees) foresets; former exposures to west showed similar features. In eat part of map area, many rounded boulders exceed 3 feet diameter. Many active and historic quarry exposures in upland areas reveal fining westward, and away, from the Columbia River. On Mill Plain, north-dipping foresets indicate transport by northward flow out of the Columbia valley. Sweeping unconformities visible in large, fresh exposures likely separate deposits of individual floods. Texturally and compositionally variable; most clasts derived from Columbia River Basalt Group but includes blocks of Troutdale Formation and Pliocene to Quaternary volcanic rocks, all probably entrained in the western Columbia River Gorge. On uplands, deposits overlie older basin-fill deposis, but cataclysmic-flood gravel bars step down into the Columbia River valley and locally thicken to the south and west, perhaps to as much as 200 feet thick along I-5 through Vancouver. West of Vancouver, a possibly inset bench may have been deposited by later, smaller floods. Beneath Holocene Columbia River floodplain deposits, cataclysmic-flood gravel coats and partly fills the late-glacial valley, a valley bottom incised at least 230 feet below sea level." [O'Connor, et.al., 2016, Scientific Investigations Map 3357]

Camas Quadrangle:
"Gravel facies -- Unconsolidated, gray, stratified, bouldery to cobbly gravel and sand deposited in thick sheets over older basin-fill deposits on upland areas flanking the Columbia River; organzied into prominent large bar and channel complexes on Mill Plain in the northwest part of map area [beginning at 164th] and much of east Portland, Fairview, and Troutdale south of the river. ... Locally, as along southern edge of the historic Columbia River floodplain and in the Lacamas Lake trough, Missoula-flood deposits form thin (<2 meters) and discontinuous mantle on older basin-fill and bedrock units. Numerous active and historic quarry exposures in upland areas reveal more than 15 meters [50 feet] of crudely stratified and poorly sorted coarse gravel and sand, commonly deposited in tall (locally >5 meters [16 feet]), steeply dipping (up to 35 degrees) foresets. Deposits generally fine westward and away from the Columbia River; in some places, contain immense boulders, some exceeding 4 meters [13 feet] in long diameter, particularly near Troutdale and along southwest side of Prune Hill. Texturally and compositionally variable; most clasts derived from Columbia River Basalt Group but includes blocks of Troutdale Formation and Pliocene-Quaternary Cascadian basalt, all probably entrained in the western Columbia River Gorge; locally, such as southwest of Prune Hill, consists of large, angular-tosubangular blocks eroded from nearby valley walls. Sweeping unconformities visible in large fresh exposures likely reflect multiple flood events. Unit includes local sand accumulations below 200 feet elevation ...." [Evarts and O'Connor, 2008, Scientific Investigations Map 3017]

Washougal Quadrangle:
"Gravel facies -- Unconsolidated, gray, stratified, bouldery to cobbly gravel and sand organized into prominent large bar along lower reach of Washougal River. Base not exposed, but bars reach heights of 20 meters [65 feet] above enveloping Columbai River floodplain. Well logs west of map area indicated total thickness locally as great as 68 meters [223 feet]. Texturally and compositionally variable; most clasts derived from Columbia River Basalt Group but also includes blocks of Troutdale formation and Pliocene-Quaternary Cascadian basalt, all probably entrained in western Columbia River Gorge. Likely deposited during multiple flood events between 20 and 15 thousand years ago. Finer sand facies probably deposited by late floods confined to Columbia River valley. ..." [Evarts and others, 2013, Scientific Investigations Map 3257]

Image, 2018, Vancouver, Washington, click to enlarge
Click image to enlarge
Sand and gravel operations, Missoula Flood deposits, Vancouver, Washington. Sand and Gravel pit across from the "Cadman, Heidelberg Cement Group, English Plant" location on SE 1st St. and NE 192nd Ave. Image taken June 11, 2018.
Image, 2018, Vancouver, Washington, click to enlarge
Click image to enlarge
Sand and gravel operations, Missoula Flood deposits, Vancouver, Washington. Sand and Gravel pit across from the "Cadman, Heidelberg Cement Group, English Plant" location on SE 1st St. and NE 192nd Ave. Image taken June 11, 2018.
Image, 2018, Vancouver, Washington, click to enlarge
Click image to enlarge
Sand and gravel operations, Missoula Flood deposits, Vancouver, Washington. English Pit operations, sign today says "Cadman, Heidelberg Cement Group, English Plant", located on SE 1st St. and NE 192nd Ave. Image taken June 11, 2018.


RM 86 ... St. Helens
Missoula Flood heights at St. Helens, Oregon, were estimated at 400 feet (Allen and Burns, 1986).


RM 71 ... Kalama Gap
The constriction between Carrolls Bluff on the Washington side of the Columbia and the bluff on the Oregon side just north of Prescott Beach backed up flood waters from the Missoula Floods into the Willamette Valley. This constriction is known as "Kalama Gap".

Missoula Flood heights at the Kalama Gap, were measured at 400 feet (Allen and Burns, 1986).


Image, 2013, Kalama, Washington, click to enlarge
Click image to enlarge
Carroll's Bluff, Washington, as seen from Interstate 5. View looking north. Image taken February 2, 2013.
Image, 2016, Prescott Point, Oregon, click to enlarge
Click image to enlarge
Prescott Point (Prescott Bluff) as seen from Prescott Beach County Park, Oregon. Image taken September 9, 2016.


RM 67 ... Longview and Kelso
Missoula Flood heights at Longview and Kelso, Washington, were estimated at 375 feet (Allen and Burns, 1986).


RM 50 ... Clatskanie
Missoula Flood heights at Clatskanie, Oregon, were measured at 275 feet (Allen and Burns, 1986).

According to Allen, et.al. (2009):

"[Between Portland and Astoria] there were two major constrictions in the Columbia River Valley, at Kalama and at Clatskanie. ... Floodwaters remained near the 400-foot contour level through Kalama, but then began to fall. After the Kalama narrows, the water was reduced to 275 feet deep at Clatskanie and near sea level at Astoria. Woodland and St. Helens were both beneath 400 feet of water. Interpolating between Kalama and Clatskanie suggests that both Kelso and Longview were at least 300 feet below the surface of the floods." [Allen, et.al., 2009]


RM 40 ... Nicolai Ridge and Clatsop Crest
Nicolai Ridge and Clatsop Crest is a long basalt ridge on the Oregon side of the Columbia River which was undercut by Missoula flood erosion, resulting in a steep north face towering over Westport and Wauna, Oregon, and Puget Island, Washington. Bradley State Wayside, downstream of Wauna, sits upon this ridge and provides great views. Bradley State Wayside is at Columbia River Mile (RM) 40.

According to Allen, et.al. (2009):

"Nicolai Ridge opposite Cathlamet, Washington is an outstanding example of a basalt ridge undercut by flood erosion resulting from an abrupt north bend of the course of the river. Abnormal steepening continues for another five miles on the south side of the river to Aldrich Point." [Allen, et.al., 2009]

Image, 2012, Brownsmead, Oregon, click to enlarge
Click image to enlarge
Nicolai Ridge near Wauna, Oregon. View from moving car. Image taken September 22, 2012.
Image, 2005, Cargo ship passing Puget Island, click to enlarge
Click image to enlarge
Cargo ship passing Puget Island, Washington. View from Bradley State Wayside, Clatsop Crest, Oregon. Image taken February 19, 2005.


RM 0 ... Astoria and the Pacific Ocean
"Two important physical effects would greatly affect the floodwaters as they moved from Portland to the Pacific Ocean. First, there were two major constrictions in the Columbia River Valley, at Kalama and at Clatskanie. Second, the Pacific Ocean was 300 feet lower in elevation during the Ice Age, since ice sheets stored enough water from the oceans to drop it that much. The Columbia River entered the ocean 40 miles to the west of present-day Astoria, near the edge of the Continental Shelf.

At that time there was a canyon from the Longview area out to the ocean. Today it is filled in with modern Columbia River sediment. In his 1994 study, Ned Gates determined that the canyon has been filled in with 75 cubic kilometers (18 cubic miles) of sediment since the Missoula Floods (as sea level rose to its current position in the mid-Holocene about 5,000 years ago). This canyon was only 40 feet deep where Longview stands today but was 360 feet below present sea level at both river mile 54 (Oak Point, Washington) and Astoria at the time of the catastrophic floods.

Floodwaters remained near the 400-foot contour level through Kalama, but then began to fall. After the Kalama narrows, the water was reduced to 275 feet deep at Clatskanie and near sea level at Astoria. Woodland and St. Helens were both beneath 400 feet of water. Interpolating between Kalama and Clatskanie suggests that both Kelso and Longview were at least 300 feet below the surface of the floods."


Source:    John Eliot Allen, Marjorie Burns, and Scott Burns, 2009, "Cataclysms on the Columbia: The Great Missoula Floods", Ooligan Press.

[More Astoria]
[More Pacific Ocean]


Image, 2005, North Jetty from Lewis and Clark Interpretive Center, click to enlarge
Click image to enlarge
North Jetty, Cape Disappointment State Park. View from the Lewis and Clark Interpretive Center. Image taken April 19, 2005.


From the Journals of Lewis and Clark ...

Clark, ...
 




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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:
  • Allen, J.E., and Burns, M., 1986, Cataclysms on the Columbia, Timber Press, Portland;
  • Allen, J.E., Burns, M., and Burns, S., 2009, Cataclysms on the Columbia: The Great Missoula Floods, Ooligan Press;
  • Bishop, E.M., 2004, Hiking Oregon's Geology, The Mountaineers Press;
  • Evarts, R.C., 2006, "Geologic Map of the Lacamas Creek Quadrangle, Clark County, Washington", U.S. Geological Survey Scientific Investigations Map 2924;
  • Evarts, R.C., and O'Connor, J.E., 2008, "Geologic Map of the Camas Quadrangle, Clark County, Washington, and Multnomah County, Oregon", U.S. Geological Survey Scientific Investigations Map 3017;
  • Evarts, R.C., O'Connor, J.E., and Tolan, T.L., 2013, "Geologic Map of the Washougal Quadrangle, Clark County, Washington, and Multnomah County, Oregon", U.S. Geological Survey Scientific Investigations Map 3257;
  • Ice Age Floods Institute website, 2018;
  • Minervini, J.M., O'Connor, J.E., and Wells, R.E., 2003, "Maps showing inundations depths, ice-rafted erratics, and sedimentary facies of late Pleistocene Missoula Floods in the Willamette Valley, Oregon", U.S. Geological Survey Open-file Report 03-408;
  • 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., Busacca, A.J., and Teisseire, 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;
  • O'Connor, J.E., and Burns, S.F., 2009, "Cataclysms and Controversy -- Aspects of the Geomorphology of the Columbia River Gorge, IN: The Geological Society of American Field Guide 15;
  • O'Connor, J.E., Cannon, C.M., Mangano, J.F., and Evarts, R.C., 2016, Geologic Map of the Vancouver and Orchards Quadrangles and Parts of the Portland and Mount Tabor Quadrangles, Clark County, Washington, and Multnomah County, Oregon, U.S. Geological Survey Scientific Investigations Map 3357;
  • O'Connor, J.E., Dorsey, R.J., and Madin, I.P., 2009, "Volcanoes to Vineyards: Geologic Field Trips Through the Dynamic Landscape, Geological Society of America;
  • Scott, W.E., Gardner, C.A., Sherrod, D.R., Tilling, R.I., Lanphere, M.A., and Conry, R.M., 1997, Geologic History of Mount Hood Volcano, Oregon - A Field-Trip Guidebook, USGS Open-File Report 97-263;
  • U.S. Army Corps of Engineers website, 2018;
  • U.S. National Park Service website, 2001, "Ice Age Floods - Background", 2005, 2018;
  • Waitt, R.B., 1985, Case for periodic, colossal jökulhlaups from Pleistocene glacial Lake Missoula: GSA Bulletin v.96, p.1271-1286;
  • Waitt, R.B., Denlinger, R.P., and O'Connor, J.E., 2009, "Many monstrous Missoula floods down Channeled Scabland and Columbia Valley", IN: "Volcanoes to Vineyards", Geological Society of America, 2009;
  • "Yamhill County News-Register", online edition, June 18, 2005, "New Erratic Rock Marker Unveiled", by Yvette Saarinen;


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 2018