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Roger Weller, geology instructor

Bitterroot Mountains
Jacob Petersen
Spring 2006

                             The Bitterroot Mountains

“What Riches are ours in the world of nature, from the majesty of a distant fragile

 peak to the beauty of a tiny flower” - Esther Baldwin York




            Creating almost the entire border between Montana and Idaho, the Bitterroot mountains contain some of the most amazing and rugged peaks in the entire United States. The Bitterroot Mountains are named after the state flower of Montana, the small pink bitterroot flower. First explored by Lewis and Clark after the Louisiana Purchase, the Bitterroot Mountains are also a place of historical significance. Except for in the foothills, the region is almost completely unexploited by the natural resource industry and has remained much as it was when first found. The unique geology of the region has also helped to keep much of the Bitterroot Range empty of commercial exploitation based on difficult access to large quantities of usable resources. Federal protection envelopes nearly all of the Bitterroot Range, as well as vast areas of forest and mountain sub-ranges to the west. One of the most rugged regions in the country, the Bitterroot Mountains were once considered impenetrable except by the brave few. The southern half of the range forms part of the continental divide and contains the highest peaks in the region. Included in this area is Trapper Peak, the highest point in the Bitterroot Range at 10,157 feet. The Bitterroot Mountains are indeed one of the most spectacular places in America.

Bitterroot Flower.

Formation and Geology:


            The Bitterroot Mountains are located on the eastern edge of the Idaho Batholith. A batholith is a large exposed body of granite that is left exposed at the surface of the ground. In some cases the area of exposed granite may have been ground down and flattened, most likely due to glacial weathering. However, in the case of the Bitterroot Mountains a very large mountain range was formed. The Bitterroot Region has been affected by glacial weather, but instead of destroying the mountains it has only made them even more spectacular. Over 200 million years ago, large bodies of molten granite began to push against the ground above them. This caused the granite masses to rise higher away from their source and cool, but also caused a massive bulge in the surface crust of central Idaho. Later, a large portion of this giant bulge slid off the top of the granite masses beneath it and came to rest 50 miles to the east. After the Sapphire Block, as the bulge would come to be called, slid away, the surface crust of central Idaho rose up again and exposed many of the cooled bodies of granite to the surface. This led to the formation of the Bitterroot Range, which would have been much less impressive had the Sapphire Block never moved. The Sapphire Block also caused a large portion of western Montana to sink beneath its weight, although erosion later filled this depression in with materials that were mostly a result of glacial weathering in the mountains.  
Blue - Sapphire Block sink area.     Red - Main part of Bitterroot Range.

Most of the spectacular and rugged landscapes of the Bitterroot Mountains were formed by glacial weathering that took place during ice ages thousands of years ago. Examples of these can be seen in countless number throughout the range. Steep canyons and spine like ridges were formed as glaciers carved out the mountain peaks and deposited much of their remains in the Sapphire Block Sink Area, known today as the Bitterroot Valley in Montana. However, the climate of our planet is now much wetter and warmer then it was when the Bitterroot Valley was created and this has allowed streams and rivers to slowly carve their way through the valley floor. The Bitterroot Mountain range receives a very large amount of snow during the winter, in some places more than 500+ inches and certainly more on the highest peaks. This produces a large amount of water runoff in the summer, filling the streams and rivers that continue to carve their way through the region.  Although the constant weathering of flowing rivers has had an impact on the region, most of the jagged peaks and winding valleys in the Bitterroot Range were created by glaciers.


 Glacier carved ridge.   

Glacial U-Shaped valley.           

Glacially striated granite.

Glacier carved ridge.     


Wildlife and Recreation:


            The unique geological features of the Bitterroot Mountains allow for a very diverse collection of wildlife and offer people who visit the region a number of interesting things to do. Because such great changes in elevation occur throughout the entire Bitterroot area, there are essentially two different climates in the region. This makes it possible for animals that live in both warm, arid regions and cool, moist regions to live in close proximity to each other. Hunting these animals is one of the things that draw so many people to the Bitterroot Mountains in the first place. Deer, elk, moose, bears and wolves reside in the lower reaches of the forested areas, while mountain goats, bighorn sheep, and mountain lions live amongst the rocks and cliffs. There are over 1,600 miles of mapped and maintained trails, as well as hundreds of miles of unrecorded trails that lead into the wildest parts of the region. Along with hunting, mountain biking and backpacking through the high granite peaks of the Bitterroot Mountains are the chosen activities for many visitors. Actually climbing the high granite peaks is also something many people choose to do when in the Bitterroot Mountains. Fishing along the rivers that drain through the valleys of the Bitterroot Range is also a favorite recreational activity of visitors to the area. What truly brings people to the Bitterroot Mountains, however, is the untamed nature of the land itself. Nowhere else in the continental United States has such a large and rugged area been left so wild and untouched. When it come to the United States, the extreme mountain terrain and sheer size of the wilderness areas within the Bitterroot Mountain Range are second only to a few unexplored and nearly unreachable parts of Alaska.


 Hiking the trails.    


Fishing the streams.   

 Male elk.

With the creation of the Wilderness Act in 1964, the national government began placing selected areas of the United States aside for the purpose of natural preservation. A large portion of the Bitterroot Mountains, along with a large river in the region, was selected to be protected under this act. Thus the Selway-Bitterroot Wilderness Area, containing 1,340,460 acres in two states, was created. The wilderness area, the third largest in the country, is controlled by the only forest service system in the entire country to rest entirely within the boundaries of a wilderness area. The area also contains the largest roadless section of the United States. A person standing in the center of the Selway-Bitterroot Wilderness would be nearly 30 miles from the nearest passable road, albeit most likely a single lane mountain trail. If it wasn’t for a small, yet paved, road that separates the Selway-Bitterroot Wilderness from the Frank Church River of No Return Wilderness to the south the area would be the largest protected region in the United States. Although in recent times logging companies have attempted gain rights to the trees in nearby national forests, the deals that were brokered were much more beneficial to the protection of the land then to the logging companies. The Bitterroot Mountains are indeed a treasure to be protected for the future generations of our planet and represent the true wild nature that was once America. These mountains are truly a magnificent wonder to behold.


 Wilderness sign.

 Protected areas.


Works Cited: