Eastern Washington Travel Guide

The Columbia Plateau was created by a series of lava flows that were later deeply cut by glacial floods. Because its soil is mostly made up of alluvial deposits and windblown silt (known to geologists as loess), it's very fertile. But little annual rainfall means that its vast central section—more than 30,000 square mi from the foothills of the Cascades and the northeastern mountains east to Idaho and south to Oregon—has no forests. In fact, except for a few scattered pine trees in the north, oaks in the southwest, and willows and cottonwoods along creeks and rivers, it has no trees.