Borah Fault

Hikes: D.
Total Distance, D: 2 miles.
Difficulty: Levels I, III+.
Season: May 1-October 1.
USGS Map: Borah Peak.
Forest Service Map: Challis N.F.
Dirt Road Miles: 3 gravel.
PLSS Location: Section 19, T8N R24E.

Introduction: These are actually three shorter hikes near the area of maximum faulting from the 1983 Borah Quake. They are easy hikes. (The author intends to add the Upper Cedar Creek hike which tappeared in the printed book when he revisits that site.)

The Birch Springs Hike: First, hike to the right from the parking area (T1), up the Birch Springs Road to the Birch Springs sign. Cut right, cross the small creek, and contour and climb around a gentle hill. Soon you are confronted with a catastrophic view. White and gray rock in a cementlike white mud flowed from a prominent scarp on your left, knocking over many aspen trees. Walk just above the fault scarp. The flow came after the quake, as you can see where the flow went right over the fault scarp. You'll pass two main areas where the debris flowed over the fault scarp--thus proving that the fault came before the flow.
  Pass the first debris flow, which is drier, shorter, and more poorly defined, and proceed to the second, southernmost flow (D2). The small creek here, and the shade provided by junipers, birches, aspens, and mountain mahogany make for a nice picnic spot. Descend this lobe, and watch as it narrows down to one distinct flow.
  Now climb back to the southern end of the fault scarp, and walk north along the edge. In a few places, cracks show where the scarp's unsupported weight is pulling away from the slope above. Note how the upper part of the flow consists of blocks of ground that rotated backwards as they broke away from the scarp. Return to your car, and watch out for earthquakes!

The Maximum Fault Hike: To see the zone of maximum faulting from the quake, hike north from the parking area (D2), taking a way along the base of the fault. Just as soon as you start, observe the small basin filled with big sagebrush, to the right of the way. This is a graben--a downthrown depression between two upthrown areas. (The upland areas are called horsts.) Along much of your route, you'll follow a horst, with a graben between you and the main fault scarp.
  Just climb along the way, with your goal the first drainage that comes in from the right. As you walk, note the way the fault changes from one big scarp at the parking area, to multiple scarps further along. Take pictures of identifiable places--the photos will be valuable for comparison purposes in a few years. It's amazing how fast the scarp is revegetating!
  When you reach the drainage (D1), you can look down to Rock Creek and to the Doublespring Pass Road. All along the base of the mountains, there are more horst and graben areas. After studying photos taken before the 1983 quake, geologists found that this quake's faults are in almost the exact same places as the previous quake's faults.
  As soon as you turn back, you can see your car. This keeps the maze of ways from fooling you!

Access: First, take a look at the holes near Chilly. Drive to Trail Creek Road, 16 miles north of Mackay. Turn left, and drive 2 1/4 miles to a four way intersection with old US-93A. Turn right on the old highway, drive 3/4 mile, and turn left. Take this road a mile and turn right on a road that follows the base of the Chilly Buttes. In 1/10 mile, you start seeing pits in the field (private property) to your right. Here, geysers shot up to 50 feet high during the quake. After another quarter mile, watch the hillside to your left. Deep gashes mark gullies where springs erupted from the hill, and flowed strongly for several minutes.
  Now turn around, take the road back to the old highway, and turn left (north). Drive 2 miles to present US 93, and turn left. After 1 mile, turn right on Birch Springs Road (access to Mt. Borah). Drive almost 3 miles, to a level area at the foot of the fault scarp, and park (T1). Hike the Birch Springs and maximum throw hikes, and return to your car.
  Drive back to the highway, and turn right. Go a short 2 miles to the Doublespring Pass (May-Patterson) Road. Turn right and drive 2 1/2 miles to the famous spot where the scarp made stairsteps on the road (T2). Challis N.F. maps shows an "Earthquake Visitor Information Center" here, so maybe something exciting will happen.