October 11, 2017
THERE ARE SIGNS OF IT all over Oregon and Washington: the dramatic cliffs of the Columbia River Gorge, the layered rock along the Palouse River, the ash deposits around the Zumwalt Prairie. A series of volcanic eruptions, starting 17.5 million years ago, formed the Columbia River Basalt Group, a complex of rock formations that was created over a few million years as lava erupted from fissures in the ground and seeped over the landscape. Among them, for example, is the Wapshilla Ridge formation, the product of about half a million years of eruptions that were, at most, thousands of years apart. The eruptions deposited about 10,000 cubic miles of rock and, according to new research, probably released enough sulfur gas to cool the whole planet down.
Image: The Zumwalt Prairie, June 2015