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.

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.

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.

Nice day for a hike in Drumheller Channels north of Othello, WA. The Ice Age Floods ripped this place apart! Geologists estimate the floods swept through the area at 65 mph 200 – 400 ft deep! The U.S. National Park Service has designated the Drumheller Channels a National Natural Landmark. J Harlen Bretz was the first geologist to promote the idea of huge Ice Age Floods sweeping through the Columbia Basin. In 1923 he wrote: “Drumheller is the most spectacular tract of butte-and basin scabland on the plateau. It is an almost unbelievable labyrinth of anastamosing channels, rock basins, and small abandoned cataracts”. #iceagefloods #drumhellerchannels #columbiariverbasaltgroup #scabland #pnwwonderland #livewashington #WanderWashington #nationalnaturallandmark A photo posted by Tom Foster (@hugefloods) on Nov 8, 2015 at 7:55pm PST

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.

Springtime in the scabland: Phlox, Lupine and Balsamroot shown. 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. 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

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

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.

	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 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
	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.
The Ice Age Floods lifted and hauled away basalt to create huge rock basins.
	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).
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 (Dusty Lake)

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
br />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.	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

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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, 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].