MILLIONS OF YEARS IN THE MAKING

Snake River Adventures, LLC

The geology of Hells Canyon tells an incredible story.

Many of the oldest rocks exposed throughout the region originated hundreds of millions of years ago when portions of what is now the Pacific Northwest were associated with ancient volcanic island systems in the Pacific Ocean. Through the movement of the Earth’s tectonic plates, these terrains eventually became attached to the North American continent.

Later volcanic activity covered large portions of the region with enormous lava flows. Uplift helped form surrounding mountain ranges, including Idaho’s Seven Devils and Oregon’s Wallowa Mountains, while erosion and the Snake River continued shaping the landscape.

Over millions of years, the Snake River cut deeper into the rising terrain, helping create the enormous canyon we see today.

Hells Canyon now exposes an unusually complex collection of rock formations. Visitors traveling the river can see evidence of ancient volcanic activity, basalt flows, limestone originating in ancient marine environments, alluvial deposits and other formations representing vastly different periods in the Earth’s history.

The canyon isn’t simply beautiful — traveling through it is like traveling through millions of years of geological history.