Frenchman Coulee and Echo Basin, Overflowing the Bathtub

Time to play catch up It's a been a while.

Lets rewind the clocks back to 15,000 years ago. Our stage curtain opens with the northern hemisphere gripped in the frigid clutches of an ice age. Canada is completely smothered, the Puget Sound region is filled to the brim, and several tongues of ice extend down through north-central Washington, northern Idaho, and Montana. One of these lobes has blocked up one of western Montana's largest rivers, the Clark Fork. The pooling lake behind this icy blockade, named Glacial Lake Missoula by modern day geologists, has risen over 900 feet in some valleys. The location of downtown Missoula, Montana is now resting at the bottom of a body of water dwarfing any lake in the western US today.

Map showing the location of Glacial Lake Missoula and the path of the ice age floods. 

But then, something happened, a catastrophic event that rearranged the face of eastern Washington forever. The ice dam holding back Glacial Lake Missoula breached. A massive wall of water, filled with icebergs, boulders, trees, tore through the narrow river valleys of the Idaho panhandle and plowed into another huge glacial lake resting over what is now Spokane and extending northwest. But even this huge glacial lake was not enough to halt the flow of this sudden rush of water, the second lake also breached and the floodwaters made their way to the Columbia River the fastest way they could, through the Columbia River Basalts.

The Columbia River Basalts, were formed 18-15 Million Years ago when the Yellowstone Hot Spot began it's chain of cataclysmic explosive eruptions in southwestern Idaho. The basalt flows covered 40% of Washington State in a flat plateau up to 3 miles thick. But as sizable as this blanket of rock was, it hardly slowed the raging water down.

Artist's rendition of what the floods may have looked like as they flowed through the Grand Coulee. 

The incredible force of the gargantuan torrent ripped into the basalt rock with vengeance, scouring huge, square-shaped canyons, or "Coulees", into the bedrock as it flowed towards the Columbia. However, at a certain point during its journey, it paused. One branch of the flood encountered the basin of an ancient lake, a geologic bathtub perched high above the eastern shore of the Columbia. The water was temporarily halted as it filled the lake basin, but the volume was too much. Eventually the flood spilled over the western rim of the bathtub.  Huge waterfalls, unlike anything the world has ever seen today, crashed over cliffs hundreds of feet into the waiting maw of the Columbia's canyon. As the volume of water going over the falls increased, the waterfalls migrated backwards, eating their way through weak layers of columnar basalt flows, picking away individual columns like straws; Frenchman Coulee was being born. At the same time slightly further to the south, Echo Basin, a huge amphitheater carved into the same lava flow as Frenchman Coulee, was also forming. Eventually, the headwalls of these spectacular basins, now used as a playground for hikers and rock climbers, and prime rattlesnake habitat, were worn back to the point where they remain today.

Looking out over Echo Basin on the edge of the Columbia River canyon (Background). Note the prominent Basalt Columns on the right side of the image. Photo by Micah K.