Catastrophic Volcanic Eruption Occurred in Pacific Northwest 16.5 Million Years Ago, Geologists Say
Oct 11, 2017 by News Staff / Source
Starting 16.5 million years ago, vents in southeast Washington and northeast Oregon put out a series of flows that reached nearly to Canada and all the way to the Pacific Ocean.
The flows created the Wapshilla Ridge Member of the Grande Ronde Basalt, a kilometer-thick block familiar to travelers in the Columbia Gorge and most of Eastern Washington.
http://www.sci-news.com/geology/wapshilla-volcanic-eruption-05308.html