20 Awesome Geological Places, Idaho & Montana

20 (or so ) Awesome Places in Idaho and Montana

Sometimes the places I explore don't fit into one particular field trip, so I put them into a post like this. Enjoy!

Eastern Idaho

The Snake River where it enters its namesake Snake River Plain in eastern Idaho. The river here is a hybrid braided and meandering -- meandering because of the low topography, and braided because of its seasonal heavy sediment load. The current is fast enough for terrific fishing and boating, but slow enough to be easy. Location: between Rigby and Ririe, Idaho.

Another view of the Snake River near Rigby and Ririe, Idaho. Did you know this is the largest cottonwood forest in the U.S.? It's absolutely gorgeous in Fall, and is home to a lot of eagles, hawks, and osprey.

The Snake River east of Kelly Canyon in eastern Idaho. This was the site of Yellowstone hot spot volcanism 8 to 10 million years ago. The smooth slopes to the left are volcanic rocks, and the cliff-forming bedrock to the right is Paleozoic limestones of the ancient continental shelf. The bedrock here has been uplifted along a normal fault at the base of the mountain front.

An early Spring view of lower Swan Valley and the Big Hole Mountains, eastern Idaho. The bedrock in the foreground is lava flows related to the Yellowstone hot spot's passage several million years ago. The Big Hole Mountains are part of the Cretaceous thrust belt, in which the ancient continental shelf was shoved and thrust-faulted landward by tectonic collisions from the west.

One of my very favorite places, Spring Mountain in the Lemhi Range of central Idaho. This is a glacial cirque, carved out by glaciers during the ice ages that ended about 12,000 years ago. A significant thrust fault cuts through this mountainside under the cliffs. The picture was taken in early June. Coordinates:  44.410097, -113.302747

This paleokarst cave in the southern Beaverhead Mountains in east-central Idaho was inhabited by native Americans 10,000 years ago. The bedrock is the Mississippian-age Surrett Canyon and lower Scott Peak formations, which are thick continental shelf limestones. Location:  44.137969, -112.873308   

This arch is about 100 meters north of the cave. See the kids for scale? The caves here formed down in the groundwater before the bedrock was uplifted by the normal fault at the base of the mountain front. It's called "paleokarst."

Southwestern Montana

This cabin and its neighbors were pushed into Hebgen Lake, Montana by a landslide and were swamped by waves during the 1959 M7.3 earthquake. The state of Montana has done a terrific job giving access to and informative signs about this earthquake area. Location is along U.S. highway 287 northwest of West Yellowstone, Montana. Coordinates: 44.852760, -111.323919  

Fault scarp at Cabin Creek campground from the M7.3 Hebgen Lake earthquake. Displacement here is 21 feet. Campers at this site that fateful August night said it felt like they were in an elevator when the cables were cut. What a ride! Coordinates: 44.872319, -111.341825  

A view of Quake Lake, Montana in late Spring, viewed from the Madison Slide (foreground). This lake was formed in the 1959 Hebgen Lake earthquake when a mountainside collapsed, damming the Madison River. The Army Corps of Engineers quickly sent a small army of heavy equipment to cut a channel so the river would not over-top the landslide and create a flood. The river is slowly eroding through the landslide, an inch or two per year. A very nice visitor center is open from Memorial Day to Labor Day. Location: 44.831526, -111.425222  

Another favorite place of mine - Birch Creek in the Pioneer Mountains of southwest Montana, not far from Dillon. The bedrock is granite that was decapitated off the Idaho batholith and shoved tens of miles eastward on a thrust fault. A pre-existing fabric in the granite is folded just like the sedimentary rocks nearby. The canyons here offer plenty of streams, small lakes, fabulous forest, camping, and hiking. Location:  45.403408, -112.833508  

At the far west end of the Birch Creek Road (past Dinner Station campground) you'll find this intriguing sign. You'll need a dirtbike, ATV, or good 4WD to get up this road! The challenge is worth it!  Location: 45.427775, -112.906474   

If you can get all the way up the rocky Birch Creek road in the Pioneer Mountains, you'll find beautiful Pear Lake at over 9000 feet elevation. It's in a basin carved out by glaciers, and enhanced by a 1930's vintage dam. Location: 45.424548, -112.991378   

Charcoal kilns were built to produce charcoal to refine ore taken from the nearby mountains. These are along the unimaginatively named Canyon Creek in the northeastern Pioneer Mountains, west of Melrose. Location: 45.679601, -112.869346   

A pleasant scene in a glacial U-shaped valley, Canyon Creek, looking up at an unnamed peak. Location: 45.676797, -112.883048   

The Pioneer Mounains scenic byway cuts north-south through the center of the Pioneer Mountains, and has a large number of campgrounds and fabulous fishing along Wise River. This view is looking south from near Wise. Location: 45.753949, -112.996628  

Yellowstone Region

The Centennial Mountains on the Idaho-Montana border as seen from Sawtelle Peak, Island Park, Idaho. The Centennials are one of only a few east-west trending mountain ranges in the U.S. (others include the Uinta Mountains, Utah, and Owl Creek Mountains, Wyoming.) One of the prettiest mountain fronts in the Yellowstone region, the Centennials are rarely visited. Bedrock is Cambrian (about 550 million years) on the east and gradually younger all the way to Cretaceous (about 70 million years) on the west. The normal fault on the north side of the range, responsible for its uplift and southward tilt, is thought to be one of the most significant seismic risks in the region. Take the Red Rock Road from Island Park to Monida, Montana for the full tour. Location of photo: 44.561612, -111.445699   

A northward view from Sawtelle Peak to Henry's Lake, Idaho. This lake is curious because it is surrounded on three sides by the Continental Divide! Location of Henry's Lake: 44.641500, -111.403009  

Aptly named Big Spring in Island Park, Idaho, is one of the most colorful, beautiful places in the Yellowstone region. The water emerges from fractured obsidian lava flows that spilled out of the Yellowstone caldera into the Island Park caldera about 160,000 years ago. Snow and rain trickle through fractures until they hit the old caldera floor's lake sediments, then flow horizontally to feed the Henry's Fork river here. The water is a constant 55 degrees F. Location: 44.500659, -111.254982  

I've seen this muskrat many times at Big Spring. Can't help but think of the Captain and Tennille (you might have to look that one up).

Big Spring and its neighbors to the south provide 90% of Henry's Fork water. It's clear and cool and absolutely lovely! I highly recommend a float trip from here (there's a launch just beyond the bend) down to Mack's Inn. It's easy enough to take kids on, and as pretty as any place in the Yellowstone region. You may even see a moose or two!

Related Posts:  Island Park