Lower Grand Coulee

Coulee City, Washington

Hwy 17 between Soap Lake & Coulee City

During the Ice Age, glaciers altered the course of the Columbia River, creating Grand Coulee. The coulee was carved even deeper as catastrophic flooding from Glacial Lake Missoula swept across present-day Washington several times before the glaciers finally receded. As they receded, the Columbia returned to its original channel, leaving Grand Coulee dry.

A 3.5-mile-long 400-foot-tall precipice is located near the midpoint of the coulee, and created a massive waterfall when water was flowing through the coulee. Ten times larger than Niagara, it is believed that Dry Falls was the greatest known waterfall in world history.

Dry Falls and Grand Coulee provide some of the evidence that has helped scientists piece together our understanding of the Missoula Floods that occured during the Ice Age and created several landscape features in Washington.

Lower Grand Coulee is the part of Grand Coulee below the falls. Today it features a number of small lakes, the result of groundwater seeping into depressions in the floor of the coulee.


blue lake

Highway 17 along Blue Lake (S05A0018)


basalt layers

Grand Coulee's Basalt Walls (S05A0019)
Much of eastern Washington and Oregon is covered with a thick layer of basalt. When basalt cools slowly, it cracks into vertical columns. When a river erodes some of the rock away, the resulting canyons carved into the basalt rock often have vertical walls.


sun lakes

Sun Lakes (S05A0020)
Although water no longer flows through Grand Coulee and over Dry Falls, groundwater has seeped into the area, creating Sun Lakes.


sun lakes

Sun Lakes from Dry Falls Interpretive Center (S05A0025)

Related Sights

You may also like these Grand Coulee landscapes:

Nearby Sights

While you're in the area, check out these sights:


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