Eastern Washington, the Columbia River Gorge, and Oregon's Willamette Valley were all shaped by a series of catastrophic floods that occurred 13,000 to 17,000 years ago. Where did all this water come from? It came from Glacial Lake Missoula, a humongous lake that formed when glacial ice blocked the flow of the Clark Fork River near present-day Sandpoint, Idaho. Geologists claim that Glacial Lake Missoula was up to 2,000 feet deep and was the size of Lake Erie and Lake Ontario put together. When the ice dam broke, the tremendous flow of water rushed westward, eventually emptying into the Pacific Ocean. The ice dam would then reform and the lake refill; over time, the flood event repeated itself many times.
As you travel around the region, you'll observe geological evidence of the existence of Glacial Lake Missoula in the landscape. This photo gallery shows the features that you can look for and lets you know where they are located so that you can check them out for yourself.