Idaho Geology and Geographical Regions

One of the most geologically interesting and diverse states in the country, it’s no wonder that so many people visit the state specifically for adventure and outdoor education. Whether you’re a long-time resident or you’re just starting to think about taking your next big adventure trip in the Gem State, check out this introduction to the state’s geology and natural history.


Find the perfect river trip along the Snake or Salmon River, visit the iconic Sun Valley ski resort or take a more remote ski adventure in the Panhandle, see the breathtaking view of Hell’s Canyon (the deepest river gorge in North America), go on a hiking and backpacking trek across the Columbia Plateau, or explore the beautiful forests that cover most of central Idaho.


You can learn about the economic benefits of these abundant natural resources as well as the increasing strain these resources are facing due to climate change. Learn about the history of the state’s lumber industry in the 19th and 20th centuries, and see the devastation of forest fires in recent years. See the infamous salmon run along the Salmon River, or register for a half-marathon in the locally famous Riggins Salmon Run.


Bear Lake and Idaho’s Basin Region

The Great Basin covers much of western United States and extends into the very southeast corner of Idaho. The Northern Basin and Range covers much of the state’s southern border. This area is higher, cooler, and drier than the Snake River Basin, though modern irrigation has allowed good portions of this land to be cultivated. The crown jewel of this part of the state is Bear Lake, which hosts a seemingly endless array of recreation and lake-based activities.

More than just the famous Bear Lake, however, our recommendation is to check out the splattering of natural hot springs that dot the lower third of the state. Along with Bear Lake Hot Springs, consider checking out Maple Grove, Durfee, Magic, and others.


The Snake River Plain and Columbia Plateau

The Snake River cuts a huge a bowl-shaped swatch across the middle of the state. It connects the Rocky Mountains in the east with the Cascade Mountains to the west and runs through the Columbia Plateau—with its breathtaking lava formations and Hell’s Canyon—in the process.

In a sign of its economic and cultural importance, several major highways (I-15, I-86, and I-84) run right alongside the river and several major towns (Idaho Falls, Pocatello, Twin Falls, Mountain Home, and Boise) were founded along the banks of the river. Heard about whitewater rafting and other river trips in Idaho? There’s an excellent chance it followed along the Snake River. The Salmon River, just a little further to the north, is also popular among fishermen and ecologists. The western part of the Snake River Plain is also a great spot to study ancient lava formations.


The National Forests of Central Idaho

Much of central Idaho is covered in alpine forest with varying characteristics and ecosystems. Perched along the Columbia Plateau, Payette National Forest is known for incredible mountain lakes and the surrounding beauty of the plateau. On the east side of the state, the Salmon Forest is coveted by those looking for a more remote and rugged adventure. Sawtooth National Forest is great for wildlife and education programs. It’s also popular for its proximity to Boise and those who are looking to add a little outdoor adventure to their city life or metropolitan vacation.

Idaho State University has produced this simple but effective guide to the state’s forests, forestry service, and lumber industry. From these types of sources, you can learn about the forests’ essential function in protecting the state’s drinking water, agriculture, and irrigation system. But it’s another thing altogether to explore these various forest terrains while hiking, camping, backpacking, snowshoeing, or skiing. Read about the forests first, then see them in person.


The Central Rockies of Northeast Idaho

All along Idaho’s eastern border, you’ll find the Central Rocky Mountains and the Bitterroot Mountain Ranges in particular. This geological mountain range is largely responsible for defining the state’s eastern border. While popular myth has it that the border was supposed to be defined by the Continental Divide and the surveyors got lost—or were paid to get lost—the truth is that Congress had originally decided that much of Montana’s western border was to be determined by the Bitterroot Mountains. Of course, how Congress made that determination is also a topic of discussion among many locals, especially since the Idaho Territory originally included most of Montana, Wyoming, and Idaho as its borders.

My grandpa loved to provoke the groans of friends and family when he said that the matter is a “bitterroot” to swallow. Even still, whether it’s the “quiet side of the Tetons” or the panhandle’s Coeur d’Alene Mountains, you literally get to see another side of the Rockies when you come to Idaho. On the west side of Idaho’s northern panhandle, you’ll also find the Selkirk Mountains, which are part of the Columbia Mountains and which host world-class winter sports adventures.