The ground trembling came first, Eastern Washington and Oregon shuddering under the approach of an Ice Age flood of 500 cubic miles of water, weighing more than 2 trillion tons.
The sound next, an ominous rumble growing to an overpowering roar. A cloud of mist on the horizon. Beneath it, a towering, unstoppable wave.
The water was a brown slurry, soupy with silt, rocks, trees, icebergs and any animals unlucky enough to get in its path: mammoths, giant sloths, beavers the size of bears. Basalt columns were peeled off like string cheese. Some gravel from Montana would be carried all the way to the Pacific Ocean. Other would be left in bars as high as a 40-story building.
If any humans were in the Northwest then, roughly 15,000 years ago, the inundation would have seemed like the end of the world.
The wave itself was a prow of white water, pushing a shockwave of air. Rivers typically flow from near zero to 7 miles an hour, but this flood started at freeway speeds. In volume, the deluge thundering across the Pacific Northwest was 10 times the combined flow today of all the rivers on Earth.
The flood started in the Idaho panhandle as a wall of water 2,000 feet high, bursting through the remnants of a glacial dam at 65 miles an hour. It spread into temporary lakes as it plowed west and south, and bunched into a rising boil at every canyon and constriction. In the Columbia River Gorge, it rose again as deep as 2,000 feet, its kinetic energy so great that it gouged out a pothole below sea level in the John Day River canyon.
At the Gorge's western end, the flood depth was still 800 to 1,000 feet, and water shot past Oregon's Crown Point like a fire hose at speeds as high as 70 to 80 miles an hour. One of its gravel bars would become east Portland, the water there 400 feet deep. The flood backed up the Willamette Valley as far south as Eugene, the swirling current grounding ice chunks that, when melted, deposited odd boulders across future farmland.
And thus was the Columbia River Gorge created...
Those massive dams were, on occasion, made of ice. Other dams that formed were made from basalt, lava that had flowed from numerous small and large volcanoes that dot the West. Geologists estimate these catastrophic floods happened up to 100 times.
The geology of this area has been influenced by many factors, including the last Ice Age, but under that ice there was always the rock. When Glacial Lake Missoula's ice dam gave way, the great carving began and when it was all done, we were left with a scenic area like no other.
But, Mother Nature was not done...