The Great Floods of Glacial Lake Missoula: Page Three

THE FIRST FRONT OF THE FLOOD

MAP #3

   Spilling into and out of Lake Columbia and across the Spokane area, a mass of water, debris, and ice 2,000 feet high at its source raced toward the ocean at speeds approaching 65 miles per hour.

   Gushing out across a southward-dipping plateau and inundating 16,000 sq. miles to a depth of hundreds of feet, floodwaters quickly stripped 200 feet of soil and cut deep canyons, or coulees, into the underlying bedrock which characterizes the area today known collectively as the Channeled Scablands.

   As floods raced southward, two major cascades were formed. The larger one was that of the ěUpper Couleeî where the river roared over an 800 ft. waterfall. The eroding power of the water plucked pieces of Basalt rock from the precipice causing the falls to retreat 20 miles and self-destruct when it cut through to the valley of the Columbia where the Grand Coulee Dam is today.

   The other was near Soap Lake. Known today as Dry Falls, it is the skeleton of one of the greatest waterfalls in geologic history. Almost three times the size of Niagara Falls, Dry Falls is 3.5 miles wide with a drop of over 400 ft.

Dry Falls

For more information regarding Dry Falls click here: