Fantastic Dry Falls - Part I

Niagara Falls has to take second place to the massive Dry Falls in the State of Washington. With a rim 5.6 kilometres wide and a drop of 116 metres Dry Falls would have been one of the most impressive spectacles in North America.

Dry Falls is just that now, dry. But when the great glacier was on the continent it was very active… at times.

The glacier from Canada spread across the Clark River in Montana and blocked it. Behind the dam the waters rose to a depth of perhaps 610 metres feet to form Glacial Lake Missoula, a lake that held over 2100 cubic kilometres of water.

Eventually the pressure of the water caused the ice dam to break so that a 610 metre high wall of water exploded down the valley.

Much of the river valley shows the effects of the rampaging water which tore the soil cover from the cliffs leaving the bare rock exposed.

Geologic evidence shows that a flow of water greater than the Amazon’s went through here for a short time. In Washington State, a 160 kilometres wide wave swept everything from its path. Only the high hills escaped the water. That region is known as the Washington Scablands. This event may have repeated itself up to 40 times.

Much of the area was covered by an ancient accumulation of wind blown dust (loess) that had built up into thick layers, in places 30 metres or more deep. Wherever the water went with any force, it ripped out most of this covering material from the black basalt rock below.

In places the water even dislodged slabs of rock. All this is revealed on the steep cliffs of the scoured canyons where there are yellowish layers above the black. The flood is known as the Spokane Flood.

The Columbia River which flowed south because of another ice dam farther north carved the gorge known as the Grand Coulee. Then the Spokane Flood surged through it making it even larger. The Coulees probably resulted from water which poured over a lip of tough rock. The waterfalls would have been impressive.



The plunge pool below the falls eroded into the softer rock. Eventually the hard rock above it would collapse and the falls would retreat upstream. In time long deep valleys were formed. Similar action is taking place on the Niagara Falls Gorge in Ontario.

Eventually the falls will disappear.

The Upper Grand Coulee now contains the water of Banks Lake. The Lower Grand Coulee is south of US-2 below Dry Falls.