Geology Home Page physical geology historical geology planetary gems
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
Introduction:
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.




Glacial U-Shaped valley.
http://idahoptv.org/lc/crossing/images/bitterroots.jpg
Glacially
striated granite.
http://www.gravmag.com/bitterroot.htm

Glacier carved ridge.
http://www.peakbagger.com/photo/p134.jpg
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.


Fishing the
streams.
http://www.pepperbox.com/images/activities/fishing-2.jpg

Male
elk.
http://www.kohlsoutfitting.com/trips/hunting/images/elk9.jpg
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.


Works Cited:
http://en.wikipedia.org/wiki/Bitterroot_Range
http://imnh.isu.edu/digitalatlas/geo/bathlith/bathtxt/bathmn.htm
http://leemetcalf.fws.gov/about2.html
http://www.bitterroot.com/grizzly/BEARS31.HTM
http://www.bozemannet.com/getting_here/bitterroot_mountains.php
http://www.fs.fed.us/r1/bitterroot/
http://www.gravmag.com/bitterroot.htm
http://www.wilderness.net/index.cfm?fuse=NWPS&sec=wildView&wname=Selway-Bitterroot%20
Wilderness&error=404