American Falls, Idaho: Devil's GateVolcanic tuff knobs remain from an extinct volcano in a place early emigrants called Devil's Gate Pass, and the Gate of Death. The park features a disc golf course.
Massacre Rocks State Park
- 3592 Park Ln, American Falls, ID
- SW of American Falls, I-86 Exit 28 west on Register Rd, turn right/north 1/2 mile to Massacre Rocks State Park.
- $5 vehicle day use fee.
Visitor Tips and News About Devil's Gate
Resistant knobs of volcanic tuff, most no more than a foot high, that are erosionally resistant remnants of small gas vents in the tuff flow. Gas (with silica-rich water vapor) flowed through the vents. As the water vapor cooled the silica came out of solution, cementing the material surrounding the vent.[Brad Wartman, 10/29/2011]