The wonderful Owyhee geology was made possible by the Yellowstone hotspot that created a huge pool of magma just below the surface here about 15 to 16 million years ago and left a trail of now buried explosive volcanic calderas in its wake. The eruptions lasted for hundreds of thousands of years and covered the region with layers of rhyolite lava and tuff up to several thousand feet thick. Millions of years of erosion and weathering produced today’s scenic Owyhee canyonlands.

Today, the hotspot plume has rotated eastward under the North American plate and is now under Yellowstone National Park. Millions of years ago, hot springs, geysers, oozing lava flows, and caldera lakes like we see today at Yellowstone likely existed in this corner of southeast Oregon. So much time has passed that hotspot evidence has long since been eroded and buried by later geologic events.

Although the hot spot moved on, volcanic activity continued. Later eruptions created the Jordan Valley Volcanic Field and the rolling high lava plains that now cover the Owyhee landscape. More than once, lava flows dammed up the Owyhee River channel, altering its course. Almost everything we now see in the Owyhee Canyon is volcanic in origin and a consequence of the hot spot.