( e Clark Fork River. Sometimes the ice d...)An ancient bathtub ring of mammoth fossils

The huge volumes of water swept overland from present-day Spokane to the Tri-Cities, creating a distinct geological region known as the Channeled Scablands. The only outlet for this tremendous outpouring was a southern ridge-opening called Wallula Gap. But Wallula Gap was too narrow to handle all the massive flow; the water would back up, creating temporary Lake Lewis, then slowly drain through to the Columbia River Gorge—all in a matter of days.

Preliminary results place most mammoth finds in the Lake Lewis area at elevations of 600 to 1,000 feet, which echoes the distribution of boulders that originated from far away—so-called erratics—and rafted in on icebergs. The evidence suggests that these elevations mirror the typical water depths when Lake Lewis and that larger floods and deeper waters, up to 1,200 feet, were exceptions rather than the rule.

Full skeletons found at lower elevations were likely buried soon after death-by-torrent, a hard to imagine wall of water a half-mile high spanning the doomed creature’s entire field of vision and approaching as fast as 60 miles an hour. Some fragments may have come from full skeletons churned up and redistributed by later floods, while others may actually have ice-rafted in with erratics.
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Source:DOE/Pacific Northwest National Laboratory