Washington’s Ice Age Floods

Mammoth toothThese fragments of mammoth tusk are part of an incredible story. During the last Ice Age, glaciers of the Northern polar icecap dammed up the headwaters of the Columbia River and then broke, releasing some of the largest floods the world has ever seen. Much of the eastern half of Washington State went under, time and time again, as the ice dam broke and then reformed, and then broke again.

Highway workers building an interchange on Interstate-5 just north of Vancouver, Washington in the town of Ridgefield, dug up the tusk fragments and passed them along to paleontologists at Seattle’s Burke Museum. When the scientists went to investigate, they learned that the tusk had been buried within the deep layers of mud and sediment laid down by those Ice-Age floods. So it seems likely the mammoth died in one of those floods and was washed to its final resting place, where the construction workers found it.

Flood ComethIt’s impressive that the flood could carry off and then bury one of the largest elephants to ever walk the earth. This is the Columbian Mammoth, a stupendous creature that makes modern elephants look small. It stood as much as 13 feet high at the shoulder. But the flood that carried it was no lightweight, either. As the picture at right shows, the torrent that was released when the ice dam broke roared down the valleys and canyons of Eastern Washington, reaching speeds of 80 miles per hour and depths of hundreds of feet. That’s a flash flood the likes of which no human has seen in recorded history. So carrying off mammoths was not at all beyond its scope. In fact, the floods scoured the soil and trees away too, taking the canyons down to bedrock, and then sweeping away some of that as well.

Missoula FloodsThe map shows just how stupendous the floods were. On the right, Lake Missoula was backed up behind the ice dam, which was in the Idaho Panhandle near Spokane, Washington. Lake Missoula inundated much of western Montana, and held a volume of water comparable to several of the Great Lakes. When the dam gave way, the water overtopped the river channels and spilled across the landscape of Eastern Washington, pooled into several gigantic temporary lakes, and then spilled down the Columbia River Gorge, where it overwhelmed the area of present-day Portland and Vancouver, and even filled the entire Willamette River valley. Ridgefield, where the mammoth came to rest, was deep underwater at the height of the surge.

The mammoths, and the floods, are gone now with the passing of time and the retreat of the glaciers. But the bones and tusks remain, and are occasionally discovered, bringing back to us the awesome history of this part of our planet. And, oh, by the way, scientists think that maybe–just maybe–the first Native Americans had arrived on the scene to be witnesses. Or victims, perhaps?

It all gets me to thinking. Can’t I come up with a story that weaves these colossal events into a plot filled with mystery and intrigue? Stay tuned.

About Tom Hopp

Thomas P Hopp is a scientist and author living in Seattle. He writes Peyton McKean mystery stories and the Dinosaur Wars science fiction series.
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