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Still Channeled Scablands: The World’s Most Peculiar Formation 2022

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Still Channeled Scablands: The World's Most Peculiar Formation 2022
Still Channeled Scablands: The World's Most Peculiar Formation 2022 1

Channeled Scablands: The World’s Most Peculiar Formation

DURING THE FINAL CENTURIES of the most recent ice age, esti­mated at 10,000-15,000 years ago, several floods stormed through the region of northern Idaho, and central and southeastern Washington State. Variously referred to as the Great Missoula Floods or the Spokane Floods; those incredible waters washed away soil between the areas of current-day Spokane, all the way south to the Snake River and west to the Columbia River. This was likely the world’s greatest series of floods.

The earliest and greatest of these floods took place in just a few days, during which more water was carried through the region than flows in all of the earth’s rivers today. This scoured away most of the soil in the area known as the Channeled Scablands. Much of this area is exposed bedrock basalt, but like little islands of deep soil, hummocks or outcrops were left. Most of the hummocks have steep north sides where the gentle slope was abruptly washed away, but they also have gentle south slopes which are still adequate for farming. But where did those floods originate?

Approximately 15,000-18,000 years ago, the ice-age glaciers pushed south from Canada. At the site of current-day Missoula, Montana, arms of the glaciers formed an ice dam to impound precipitation as well as the water that flowed from the Rockies, the Clark Fork River, and nearby drainages. Eventually a glacial lake was formed that reached an estimated 500 cubic miles.

Over the next 2,000 years, the earth warmed and the ice dam began to melt. As the dam melted, the lake grew higher and floated the ice dam. The result was an enormous flood that rushed across northern Idaho and into the Spokane Valley. It took paths westward, west by southwest, and the southwest tract, which created the Cheney-Palouse Scablands. That tract came through the current-day western 1/4th of Whitman County to the Palouse River, then to the Snake River, the Columbia, and on to the Pacific. The water was so high that it backed up river valleys so that they flowed upstream.

Erratic rocks, those out-of-place from far away, were left throughout the flooded areas. The erratic rocks were carried by unmelted pieces of the glacier. The bedrock was scoured clean in many areas. The Glacial Lake Missoula would then fill again, but at a lower level, and then flood again. It is estimated that as many as 40 of these floods took place at approximately 50-year intervals. Each time more soil was scoured away from those soil-depleted lands.

When viewed from an airplane, much this region looks like giant scabs on the land. The scabs appear to run in three wide channels. Consequently, this region is referred to as the Channeled Scablands.
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Channeled Scablands: The World’s Most Peculiar Formation|