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scabland: a region characterized by elevated tracts of rocky land with little or no soil cover and traversed or isolated by postglacial dry stream channels.
-Webster-

"CHANNELED SCABLAND"

The Channeled Scabland in eastern Washington - Drumheller Channels.

“Drumheller is the most spectacular tract of butte-and-basin scabland on the plateau. It is an almost unbelievable labyrinth of anastomosing channels, rock basins, and small abandoned cataracts”.

J Harlen Bretz

THE COLUMBIA BASIN’S “CHANNELED SCABLAND”

The scabland was created where the Ice Age floods accelerated across the tilted surface of the Palouse slope, causing massive erosion. Much of the eroded sediment was carried all the way to the Pacific Ocean.

Move your mouse over image to remove Glacial Lakes and Ice Sheet.

NASA base image shows eastern Washington's Channeled Scabland from space. Major scabland tracts are identified: Moses Coulee (1), Grand Coulee (2), Telford-Crab Creek (3) and Cheney-Palouse (4). Another ice sheet (Laurentide) east of the Rocky Mountains - extended south to about same latitude as the Cordilleran sheet. Illustration does not show alpine glaciers that were feeding down into ice sheet from the mountain ranges.

Lower Grand Coulee channels.
No path to this Grand Coulee scabland viewpoint. Be careful if you go - Loose rock! Fall exposure! ...Great View!
Link with a few more images of this area: Trip Report.

The unflattering term “scabland” sometimes is applied to rough or barren regions with little or no economic potential – especially for agriculture. The esteemed analyst of the Columbia Basin scabland –geologist J Harlen Bretz—used the term “channeled scablands “ because he saw clear evidence that this strange landscape had been created by monster Ice Age Floods which had gouged channels through it. This distinguishes the Columbia Basin from tracts of scabland [or badlands] elsewhere, in which the topography normally results from the effects of massive long-term erosion.


BBC Describes Glacial Lake Missoula and the Channeled Scablands

Player set to start at Scabland section of program on click.


Out-of-place boulders (glacial erratics) are scattered throughout the scabland.

Lake Missoula Floods ice rafted erratics.
erratic: a misplaced, oversized boulder that is of a different rock type than the underlying bedrock of the region. In the Mid-Columbia Basin, erratics were rafted in on icebergs and came to rest in slackwater areas during Ice Age flooding.

Deer graze near huge glacial erratic above. At top-right: Argillite boulder stranded in lower Grand Coulee. Bottom-right: Erratic boulder sits on pothole floor near Quincy, WA.

Lake Missoula Floods ice rafted erratics.
Lake Missoula Floods ice rafted erratics.


Columbia Basin Wildflowers, phlox, lupine and balsamroot.
Springtime in the scabland: Phlox, Lupine and Balsamroot shown.


Drumheller Channels rattlesnake.
Scabland resident- These guys are out there but seem to work hard to stay out of the way. Watch your step when hiking in rattesnake habitat.

Aerial image shows Potholees Coulee scabland.

Potholes Coulee

Caption soon ... Photo by Jim Wark at AirPhotoNA.com.

"I could conceive of no geological process of erosion to make this topography except huge, violent rivers of glacial meltwater...It was a debacle which swept the Columbia Plateau."

J Harlen Bretz

Bruce Bjornstad On the Trail of the Ice Age Floods.

Frenchman Coulee and Echo Basin cataracts.
Frenchman Coulee and Echo Basin cataracts.

View Nick Zentner's Frenchman Coulee video.

Deep Lake Ice Age Floods pothole.
Some potholes near Deep Lake are 40-50 ft. deep.

NOTE: Interesting scabland features are also found in the Columbia Gorge and Southern Idaho (Snake River Canyon).

Scabland: Where is it?

That part of Washington which contains the channeled scabland is defined roughly as follows: The northern boundary is the plateau region which begins south of Lake Roosevelt and the Spokane River from Grand Coulee to a few miles west of Spokane. The western limit follows Grand Coulee to the town of Soap Lake, then to the Columbia River near Quincy, and south along the Columbia to the Saddle Mountains. The eastern boundary approximates an imaginary line from Spokane south to where State Road 127 crosses the Snake River. The southern limit is the Saddle Mountains from Mattawa to Othello, and then an imaginary line running southeast from Othello to the Snake River.

This is a vast expanse of real estate. But while it contains the channeled scabland, only part of it actually rates as scabland. Bretz estimated that there are 2,000 square miles of scabland within the region. However, in their book Cataclysms on the Columbia, authors John Elliot Allen and Marjorie Burns include 1,500 square miles in only that part of the overall scabland region south and east of Interstate 90 and U.S. 395 from Spokane to Ritzville and Pasco. Allen and Burns do not offer an estimate for the square mileage of scabland elsewhere in the Columbia Basin, but their calculation would suggest a larger overall total than Bretz’s.

Many areas within the above boundaries clearly are not scabland. The rounded Palouse-type hills which retained topsoil in spite of the floods are intensively used today for grain production. A belt of these hills north of Interstate 90 between the town of Sprague and the city of Moses Lake provides one example. The eastern fringe of the scabland region is a mixture of Palouse hills and scabland. Certain coulee valleys qualify geologically as scabland, but enough soil from nearby hills has eroded into them that they, too, are farmed. A motorist driving Interstate 90 between Moses Lake and George, Wash., will observe little or nothing out of the ordinary while passing among field of sweet corn, potatoes, peas, alfalfa, or mint. Tracts of scabland such as those southwest of Sprague Lake or in the Drumheller Channels [south of Potholes Reservoir], however, are only fit for cattle grazing and isolated hay fields.

Cattle graze in the channeled scablands - Drumheller Channels.

DRUMHELLER CHANNELS

Designated as a National Natural Landmark, the Drumheller Channels south of Potholes Reservoir total more than 60 square miles of channel’s buttes, and basins.

J Harlen Bretz identified 150 distinct channelways and 180 rock basins in this area. The channels are 400 feet lower than the surrounding buttes. [Drumheller’s lakes and marshes are the destination of vast numbers of migrating sandhill cranes which visit the region each spring.]

Othello Sandhill Crane Festival
Sandhill Cranes in Drumheller Channels - Othello Crane Festival.

Umatilla Rock in lower Grand Coulee.
Umatilla Rock - Grand Coulee

Trip Reports: Umatilla Rock I, Umatilla Rock II

"The bedrock of eastern Washington is the key to understanding how the floods were able to carry away so much rock. If the bedrock of the Channeled Scabland was mostly granite or metamorphic rock, I don't think coulees and scabland would've formed. But the basalt bedrock, riddled with cooling fractures, was pre-cut and ready to be hauled off!"

Nick Zentner (CWU)


SCABLAND CHARACTERISTICS

The channeled scabland was created where the Ice Age floods accelerated across the tilted surface of the Palouse slope, causing massive erosion. Much of the eroded sediment was carried all the way to the Pacific Ocean.

Scarped Palouse Hills, Cheney Palouse scabland tract.

LOESS REMOVED BY FLOODS

Early morning along Hammer Grade Road (Cheney-Palouse Scabland Tract). This area was once covered with rolling loess hills up to 250 feet thick. In major channels, the Ice Age Floods removed huge amounts of loess (windblown silt), exposing the basalt bedrock. Flood scarped face of loess hills shown in distance beyond scabland.

View images of streamlined loess islands (Palouse Hills) at: Hammer Grade Trip Report, Palouse River (East) Trip Report.
Longitudinal Grooves, Grand Coulee.

LONGITUDINAL GROOVES

Once the loess blanket was removed to expose underlying basalt, the floodwaters began the process of carving scabland features. Note photographer's shadow: Camera is mounted on the end of a 16' pole (see camera shadow) to view grooves. Basalt between grooves often looks like old broken asphalt roads.

"...the water would begin by eroding longitudinal grooves, probably associated with longitudinal vortex structure in the macroturbulent flow field." -Vic Baker

Crossing Longitudinal Grooves, Grand Coulee.

KOLKS CREATE POTHOLES

Another feature of the Channel Scabland are numerous lakes, ponds, and dry depressions. As the floodwater gouged troughs in the basalt, swirling eddies known as “kolks” plucked chunks of basalt from the channel beds. Later floods widened them. South of Sprague Lake is an extensive region which shows kolk effects. Kolk-carved lakes and depressions (potholes) also are common near Sun Lakes State Park (image left) and the Drumheller Channels.

Crossing Longitudinal Grooves, Grand Coulee.
The Ice Age Floods lifted and hauled away basalt to create huge rock basins.

Basalt Arch, Telford-Crab Creek Tract.
Pothole scabland development.
Potholes coalesce
The floodwater's hydraulic plucking effect rapidly removed the fractured bedrock. Potholes were drilled by kolks (often described as "whirlpool-like" or "underwater tornado-like" currents). Photo at left shows all that remains of wall between two potholes (a rare basalt arch). Image above illustrates result when several potholes merge (or "coalesce") as butte-and-basin channels develop (wide view of this area near page top).
Scabland features, Channeled Scabland, Potholes and Scour Marks.

The scabland also contain what geologists call butte-and-basin topography. The massive floods scoured lengthy grooves in the underlying basalt, and then gouged out potholes and rock basins. Subsequent flooding created vertical walls of basalt which became temporary cataracts and then dry waterfalls. These dry falls receded as each successive flood ripped basalt columns from their forward edges.


Potholes Coulee plungepool view in the Channeled Scablands.
Potholes Coulee plungepool (Dusty Lake)
Scabland gravel bar.

Interesting depositional features are found throughout the scabland: Erratics, flood bars (above) and rhythmites. Look for these featues in slackwater areas.


Floodwaters Exploit Large Scale Fractures in the Basalt


View Larger Map
Shortcut in the Palouse

Use Google Map tools to explore Palouse River Canyon (Left). Huge pre-flood cracks in the basalt created an opportunity for the Ice Age Floods to carve the spectacular Palouse River Canyon.

The modern-day Palouse river leaves Washtucna Coulee (see SR-26) and flows south to the Snake River (bottom of embedded map) via this shortcut.


Grand Coulee monocline.
Coulee Monocline

Image above shows tilted basalt layers in the Grand Coulee (SR-17 shown). Floodwaters found the broken edge of the Coulee Monocline and were able rip apart and remove huge volumes of rock.

Maps and information related to: Coulee Monocline

Wikipedia: Monocline



CLICK ABOVE TO RIDE WITH TOM TABBERT

When the Ice Age floods diverted the Palouse River from its former course through Washtucna Coulee, the new waterway carved a deep 11-mile scabland canyon north of the Palouse River’s junction with the Snake River. Coulees, abandoned spillways, buttes, and recessional cataracts dominate the landscape. Palouse Falls has retreated about five miles up the canyon due to the series of Lake Missoula floods. The falls are an impressive sight and may be viewed from an overlook at Palouse Falls State Park, north of the State Road 261 bridge crossing the Snake River at Lyons Ferry.

EASTERN WASHINGTON COULEEES

The most visible landmarks are the region’s coulees. These features are steep-walled canyons which either lack any active streams or contain streams so puny that they couldn’t have been responsible for the scale of erosion needed to gouge the coulees. The channels in the coulee floors represent an interconnected pattern of braiding. An exception is Grand Coulee, whose lower segment between Coulee City and Soap Lake is filled by a chain of lakes, and whose upper reaches are the dammed impoundment of Banks Lake.


Moses Coulee scabland.
Moses Coulee floor scabland.

Among the other more impressive landforms of this type are:
  • Moses Coulee, which stretches for more than 40 miles from Mansfield to the Columbia River near Rock Island.


  • The complex of canyons through which Coal Creek and upper Crab Creek flow between Harrington, Odessa, and Wilson Creek [traversed by State Road 28].


  • Washtucna Coulee between Connell and Washtucna [State Road 260].


  • Frenchman Coulee on the Columbia’s east bank north of the Interstate 90 bridge at Vantage, as well as Potholes Coulee, about five miles upriver from Frenchman Coulee.


  • Lower Crab Creek Coulee between the Frenchman Hills and Saddle Mountains [from Othello to the Columbia River just north of Sentinel Gap].


Dry Falls Cataract System - Ice Age Floods from Glacial Lake Missoula.
Huge cataracts at Dry Falls State Park (near Coulee City, WA).


Coulee Corridor - Truck on floor of the Lower Grand Coulee.
Lower Grand Coulee Floor - SR 17.

All photos by Tom Foster unless otherwise noted.

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