Welcome to Hells Canyon Geology

Hells Canyon is a ten-mile wide canyon located along the border of eastern Oregon and western Idaho in the United States. It is North America's deepest river gorge at 7,993 feet (2436 m). The canyon was carved by the waters of the Snake River, which plunges more than a mile below the canyon's west rim on the Oregon side and nearly 8,000 feet below the peaks of Idaho's Seven Devils Mountain range to the east.

The definition of Hells Canyon is controversial, and depends on the opinions of individual scientists, managing Federal agencies, business entrepreneurs, and towns’ chambers of commerce that advertise to attract visitors. The definition could include either the entire length of the Snake River Canyon between Huntington, Oregon and Lewiston, Idaho or be defined more rigorously as a small length of canyon from near the Hells Canyon Dam to Pittsburg Landing.

This website, similar to the definition recommended by Vallier (1998), defines Hells Canyon as that south-to-north length of the Snake River Canyon from near Oxbow, Oregon to the Snake River’s confluence with the Grande Ronde River in Washington. This definition fits the geologic features of the island arc’s magmatic axis and its associated rocks (Wallowa terrane). Older rocks in the Snake River Canyon south of the Oxbow to Huntington are mostly parts of the Baker and Olds Ferry terranes. And, north of the Grande Ronde River confluence, the canyon is cut predominantly into younger Miocene basalts.


This web site was created to familiarize you with the geology of Hells Canyon and the Blue Mountains, to provide geologic resources including seminal papers and books, and to keep you abreast of current geologic research in the region. The site provides links to related State and Federal web sites along with links to college and university departments of geological sciences. There are also links to many of the outfitters that are available to guide you during a visit to the canyon. Where possible, we provide the names of geologists who are willing to lead field trips and to give opinions on resources, environmental concerns, and potential geologic hazards like earthquakes and landslides.

We've made available many creative and original projects of the region. The geologic maps are a work in progress and are available for purchase as they are completed. We've also compiled a list of books that relate to Hells Canyon but are not geologically oriented. Finally, there is an introduction to Seven Devils Books, a collection of original fiction written and published by Tracy Vallier. These books are available for purchase.

What Is Geology?

Geology is the science and study of the physical matter and energy that constitute the Earth. The field of geology encompasses the study of the composition, structure, properties, and history of the planet's physical material, the processes by which it is formed, moved, and changed, the history of life on Earth, and human interactions with the Earth.

Hells Canyon Geology is much more personal. It is the story of one man's efforts to understand, document and share the unique geologic history of Hells Canyon and the Blue Mountains. Geologist Tracy L. Vallier has spent a vast portion of his professional career in or near Hells Canyon, his trusty four-pound sledgehammer shattering the silence of many a rocky outcrop, his backpack heavy with rock and mineral specimens carefully chosen along the way. From the early 1960's through today, a time span of nearly fifty years, his research and publications have led to a greater understanding of the rich geologic history of the region.