Silver Lake

The water that shaped this part of Washington came from a lake in Montana, and it arrived all at once.

During the last ice age a glacier dammed the Clark Fork in northern Idaho and backed up a lake across western Montana holding as much water as Lake Erie and Lake Ontario combined. Then the dam failed. The lake emptied across Idaho and into eastern Washington in a matter of days, stripping off the soil and cutting channels into the basalt underneath. The ice reformed, the lake refilled, and it happened again. Geologists count more than forty of these floods.

When J Harlen Bretz proposed this in 1923, his profession would not have it. Catastrophes were unfashionable and landscapes were supposed to form slowly. It took fifty years and the work of J T Pardee, who identified the Montana lake as the source, before Bretz was accepted. He received the discipline's highest honour in 1979, aged ninety six.

Silver Lake sits at the eastern edge of that country, just west of Spokane where the scablands begin.