Geologic Points of Interest - Boise
Photo provided by Boise National Forest
Trinity fire lookout Boise National Forest
Type - Springs/Falls, Volcanic Activity, Earthquake Activity
Description - The Kirkham Hot Spring is easily accessible on foot from the nearby national forest Kirkham campground. Summer season is usually quite busy and nightly closure from 10:00 p.m. - 6:00 a.m. is strictly enforced. Steamy waterfalls and hot pools make this site very inviting to the weary traveler.
The Kirkham Hot Spring is part of the South Fork Payette Geothermal System (SFPGS). This series of thermal springs is located along faults that fracture the Atlanta lobe of the Idaho Batholith. Seismic activity helps to keep the hydrothermal systems in this region active. A magnitude 7.3 earthquake, the highest magnitude ever recorded in Idaho, occurred as recently as 1983. Noticeable changes in flow rates of the springs were recorded near the epicenter which was located just north of the SFPGS.
The Idaho batholith is comprised of Cretaceous period micaceous granites, leucogranites, and granodiorites. Tertiary plutons of granite and diorite are also present (Druschel et al., 2001).
Directions - On Highway 21 to Lowman, ID, turn left on the Banks-Lowman Road or take Highway 55 north to Banks, turn right on Banks-Lowman Road.