Borah Peak, Idaho West
Borah Peak, Idaho - West Side
- Breath-taking scenery
- 20 mile-long fresh fault scarp
- Hiking trail to peak
- Great ATV and hiking trails
- Great back-country camping
- No crowds, ever
Travel to Borah Peak
Interactive Google Map of Borah Peak area
Lodging Near Borah Peak
Borah is pretty remote from towns, so it's a good place to camp with tents, truck campers, or trailers. But here are the nearest towns:
Sun Valley / Ketchum (west) -- The famous resort area has a lot of accommodations, and in the summer they're reduced in price. It's a graded gravel road to get to Borah from there, okay for cars when dry.
Challis (north) -- Challis has a couple of motels along the highway. If you're camping, I highly recommend Challis Hot Springs along the Salmon River, where I've stayed many times on field trips. The grassy, shady camp sites and swimming pools are a bargain, and spending time strolling along the rapid Salmon River is a soul-filling treat. Here's their website.
McKay (south) -- A couple of small motels. Farther south, Arco has a couple of motels and a KOA.
The mountain front at Borah is conspicuously steep Just look at the alluvial fans, whose apeces (apexes) are a thousand feet higher than the valley! That means the mountain is uplifting faster than erosion & deposition can deepen the canyons and lower their mouths. This view is from the Chilly road.
Borah Peak is made of limestones that formed on the ancient continental shelf. On the right (west) side are steeply tilted layers of the more colorful Jefferson Formation, which includes black dolostone and yellow calcareous siltstone. The hiking trail goes up that western ridge. The tilting occurred during continental collisions between about 150 and 50 million years ago. Uplift of the mountain range only started about 15 million years ago. This view also shows the fault scarp from the 1983 earthquake.
Borah Peak Trail
Driving up to the trailhead from the highway, you'll have good views of the 1983 fault scarp (the light-colored ribbon along the lower mountain front). More on that later.
Much of the water in Birch Creek comes from springs near the fault.
The Borah Peak trailhead gets a steady flow of visitors all summer long. That means it's busy for Idaho, not busy like California trails!
This is a whale of a hike, not to be taken lightly. Many who start out do not make it to the top.
1983 Fault Scarp
Borah Peak was the site of a M6.9 (old scale M7.1) earthquake on October 28, 1983 at 8 in the morning. It was the biggest quake in the U.S. in 25 years. Its maximum shaking intensity (Mercalli scale) was IX, which is violent and has only been reached a few times in the U.S. It was felt from Calgary, Alberta on the north to Salt Lake City on the south, and from western Wyoming to eastern Oregon. The fault scarp is 21 miles (34 km) long, with a maximum displacement of about 9 feet (2.7 m). The mountain range rose nearly a meter, while the valley dropped nearly 2 meters (measured away from the scarp). You can find authoritative information about the quake at the USGS.
Because of its remote location, only 2 people were killed in the earthquake, but tragically those two were children walking to school in Challis. Tara Leadon, 7 years old, and Travis Frank, 6, were killed when a 75 year old stone facade on a store collapsed on them.
Faults usually form branches, especially tilted (dipping) faults like the Lost River Fault here. They're analogous to fractures in glass, which branch off, merge, and are sometimes parallel without merging. Just how the geometry forms is a function of bedrock strength, depth of gravel, structures or fabrics in the bedrock, and direction of fault slip.
The scarp is fascinating to geologists! Its varied geometry tells us a lot about the geometry of the fault at depth. A simple but powerful principle says that the geometry we see at the surface in map view is the same geometry at depth when turned on its side in cross-section view. Let's apply that principle to the following pictures of the scarp.
Visitor Site on Doublesprings Pass Road
A sign on highway 93 will point you toward this site. The Doublesprings Pass Road is a smooth, graded gravel road. It was displaced in the earthquake, but of course it has been smoothed out since. The site is a dirt parking lot with an outhouse, a fence around the scarp, and informative signs.
An interesting trip using this road is to take it northeast to the Pahsimmeroi Valley road, then north to Ellis on the Salmon River. Look for the metamorphic rocks along the road at Ellis! From there, you can go west to Challis or east to Salmon, and it's wonderful scenery all the way.
Borah Peak area, east side