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Drumheller Channels National Natural Landmark

ScablandsA violent geologic past has shaped the Columbia National Wildlife Refuge, creating in its wake features unique enough to interest the National Park Service—again and again and again. Well, at least twice.

The Drumheller Channels are the most spectacular example in the Columbia Plateau of basalt "butte-and-basin" channeled scablands. This is an erosional landscape characterized by hundreds of isolated, steep-sided hills surrounded by a braided network of (usually) dry stream channels. The landscape is the result of dramatic modification of the Columbia Plateau volcanic terrain by late Pleistocene catastrophic glacial outburst floods—the Missoula Floods. These floods occurred at a scale remaining unparalleled on earth, either in the geologic record or in historical account.

So striking and extreme is this landscape that in 1986, the National Park Service designated the Drumheller Channels National Natural Landmark. National Natural Landmarks recognize sites that contain outstanding biological and/or geological resources, regardless of landownership. They are selected for their outstanding condition, illustrative value, rarity, diversity and value to science and education. In fact, so important and unique are the Missoula Floods and the resulting landscapes that Congress has designated the Ice Age Floods National Geologic Trail.

How Were the Channeled Scablands Formed? 

BTW: "Scablands" is the term that applies to the torn up landscape in the Columbia Basin left by the Missoula Floods; early visitors thought the landscape barren—the term wasn't applied with affection. 

Anyway, going back to the last ice age, 13,000 to 15,000 years ago, the Okanogan lobe of the Cordilleran Glacier moved down the Okanogan River valley and blocked the ancient route of the Columbia River, backing up water to create Lake Spokane. Skipping a whole bunch of geology that you can read elsewhere, let's sidetrack to where the floodwaters came from. Most of the floods—there may have been dozens of them—were the result of a finger of ice coming down and blocking the Clarks Fork River. This pooled water up behind the ice dam to create Glacial Lake Missoula, the water rings of which can still be seen around the city of Missoula. Occasionally, this ice dam would give way, discharging the lake within the span of a week. The Missoula Floods discharged into Lake Spokane, through the Grand Coulee, greatly enlarging it, passed over Dry Falls and then ponded in and inundated the Quincy Basin, covering over 585 square miles and creating the Ephrata Fan (a deposit of boulders, cobbles, and pebbles where the flood waters discharged into the basin). The discharge volume was so great that water overflowed Lake Spokane in multiple places and also reached the Quincy Basin via the Telford-Crab Creek scablands and Lind Coulee. When floodwaters encountered the Frenchman Hills, their level was high enough that, although the bulk of the water passed through the Crab Creek drainage, some water spilled west over the low points of three divides along Evergreen and Babcock ridges to reach the Columbia river channel at Frenchman Coulee to the southwest, Potholes Coulee to the north central and Crater Coulee to the northwest. The bulk of the floodwaters took the easiest path, straight south through the Drumheller Channels stretch of Crab Creek.

The elevation drop of the floodwaters as they passed through the Drumheller Channels area was greater than 160 feet over a distance of 12 miles with gradiants locally ranging from about 10.5 to 63 feet per mile. This hydraulic head, combined with a flow depth of from 200 to 400 feet, provided the energy to achieve flood flow velocities as high as 65 mph, which eroded the topsoil and underlying basalt, gouging the complex network of channels, basins, potholes and buttes that are found there even today. Examples of scabland features, such as large excavated potholes, provide evidence of the tremendous powers of the floods.

There is a unique character to the Drumheller Channels; unlike most other Channeled Scabland zones, no single centralized channel or major cataracts were formed. In the Drumheller Channels the floodwaters passing through in a broad cascade of 8 to 12 miles in width. There are 150 distinct channels and over 180 rock basins in this region. Many of the low areas, including Upper Goose Lake, are filled by water seeping in through cracks in the basalt bedrock, which are connected with Potholes Reservoir to the north.

Other sources of information on the floods and the geology of the area include:

     Hanford Reach National Monument Geology Pages
     National Park Service Ice Age Floods Report
     National Park Service Drumheller Channels National Natural Landmark Site 

Page Photo Credits — Scablands - Chuck and Grace Bartlett
Last Updated: Mar 07, 2014
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