Volcanic Activity

Kirkham Hot Spring

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.

Description: The Kirkham Hot Springs is easily accessible on foot from the Boise National Forest Kirkham Campground. Summer season is usually quite busy and nightly closure from 10:00 p.m. to 6:00 a.m. is strictly enforced. Steamy waterfalls and hot pools make this site very inviting to the weary traveler.

The Kirkham Hot Springs 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. An earthquake with the magnitude of 7.3, 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 gradiorites. Tertiary plutons of granite and diorite are also present (Druschel et al., 2001).

Tushar Mountains

Directions: From Highway 89, south of Richfield, UT, just past Big Rock Candy Mountain, to the west begins the Tushar mountains. They continue south and end near Circleville, UT. Highway 89 offers the eastern view of this range.

Description: The Tushar Mountains consist of the Bullion Canyon Volcanics from 22-35 million years ago and the Mount Belknap Volcanics from roughly 21 million years ago. Catastrophic eruptions with large volumes of ash deposited as far north as Richfield formed the Joe Lott Tuff Member and led to the collapse of the Mount Belknap caldera 19 million years ago. 

Fluvial, eolian, and glacial activity has largely eroded these volcanics. Driving through Marysvale Canyon (see Big Rock Candy Mountain below) reveals a profile of the volcano's flank and several flows to the east. Sulphur laden deposits with their distinctive yellow color are also visible in this region and attest to the later stages of the volcanic activity (Godfrey.)

Big Rock Candy Mountain

Directions: Drive 20 minutes south of Richfield, UT on Highway 89.

Description: This landmark mountain and it's "lemonade spring" get their names from the brightly colored clays and rusty colored spring water. The clays were hydrothermally altered forming oxidized iron, limonite, and weakened in the process. Erosion readily took hold of the weakened materials to elaborate the colorful display. Across the canyon, is a small gray igneous intrusion that may have been the cause of the hydrothermal alteration. Melting its way through the layers, the intrusion may have heated and acidified the hot water.

Five miles north of Big Rock Candy Mountain, tertiary volcanic tuff and lava fragments form a mudflow deposit from a Mount Belknap eruption (see Tushar Mountains above). Tilted greenish and pinkish layers of volcanic ash are also visible just north of the I-70 Junction near Sevier (Chronic, 1990.)

Aurora-Bodie Volcanic Field

Directions: Highway 359 is south of the Aurora-Bodie volcanic field. The Old Bodie Road from Highway 359 south of Hawthorne NV enters the heart of the area.

Description: The Aurora-Bodie volcanic field occurs east-northeast of Mono Lake, between the Sierra Nevada and the Great Basin. Calc-alkaline andesite, dacite and trachyandesite lavas, breccias and ashflow tuffs, dated 15 to 8 million years ago, underlie a tighter concentration of younger alkaline-calcic cinder cones and flows. The older volcanics cover approximately 80 square kilometers with a volume of approximately 35 cubic kilometers.  Andesite domes and flows, 4.5 to 2 million years in age, occur at Cedar Hill and other areas in the field, and Pleistocene to late Holocene basaltic rocks forming well-preserved cinder cones and flows cover approximately 100 square kilometers. The probable late Pleistocene age Mud Springs volcano consists of a steep-fronted bulbous flow surrounding a depressed vent area, and a 7-kilometer-long ridged flow, together creating a remarkably distinctive landform. Although trees cover the flows, partially accounting for their dark color, the volcano is clearly one of the freshest in the Aurora-Bodie field.

Aurora Crater, approximately 12 kilometers west of Mud Springs volcano, is a 1.7-kilometer-wide breached crater of approximately 250,000 years, totally surrounded by lava flows, with an estimated total volume of 2 cubic kilometers.  Many of the volcanoes are cut by faults, and Pleistocene basalt has been warped as well. The topography of the entire area has been softened by ash probably erupted by the younger Mono Craters to the southwest. Gold and silver found in quartz veins in the Miocene (but not younger) volcanic rocks were mined until about 1950, and only the ghost towns of Bodie, California, and Aurora, Nevada, remain. (From: Wood and Kienle, 1990)

Alkali Valley and Mud Spring Canyon Spillway

Directions: Highway 359 is south of the Aurora-Bodie volcanic field. The Old Bodie Road from Highway 359 south of Hawthorne NV enters the heart of the area.

Description: Mono Basin, on the eastern flank of the central Sierra Nevada, is the highest of the large hydrographically closed basins in the Basin and Range province. Geomorphic features, shoreline deposits, and basalt-filled paleochannels have been used to reconstruct a Pleistocene record of shorelines and changing spillways of Lake Russell in Mono Basin. During this period, Lake Russell repeatedly attained altitudes between 2205 and 2280 m—levels far above the present surface of Mono Lake (1950 m) and above its last overflow level (2188 m). The spill point of Lake Russell shifted through time owing to late Tertiary and Quaternary faulting and volcanism.

During the early Pleistocene, the lake periodically discharged through the Mount Hicks spillway on the northeastern rim of Mono Basin and flowed northward into the Walker Lake drainage basin via the East Walker River. Paleochannels recording such discharge were incised prior to 1.6 million years ago and again after 1.3 million years (ages of basaltic flows that plugged the paleochannels). Faulting in the Adobe Hills on the southeastern margin of the basin eventually lowered the rim in this area to below the altitude of the Mount Hicks spillway. A pre-Pleistocene aquatic connection through Mono Basin between the hydrologically distinct Lahontan and Owens–Death Valley systems has been long postulated by biologists. Recent work confirms a probable link during the Pleistocene for species adapted to travel upstream in fast-flowing water.  

A low divide in northeastern Mono Basin lies at an altitude of 2237 m in the northwest corner of Alkali Valley, a northeastern appendage of Mono Basin. At the time of the highstand at 2155 m, 13,000 years ago, Lake Russell inundated the southern part of Alkali Valley but did not reach the higher northeastern part of the valley. Subdued lake terraces in the northern part of the valley below 2180 m probably were deposited during the 2188 m highstand of Lake Russell that did enter the valley. The late Tertiary and Quaternary sedimentary and volcanic stratigraphy of the area between Alkali Valley and Mud Springs Canyon records a history of older northward overflow from Lake Russell. This record can be deduced from the ages of deposits that were incised by paleodrainages carrying lake discharge and subsequently plugged by volcanic flows.  

Mud Spring Canyon is dry but for one small spring. The flat-floored, steep-walled canyon is 300–400 m wide and 40 m deep for much of its length but narrows quickly above a point 3 km up-canyon from the western end of flow. The modern drainage area above the spring is 75 km 2, disproportionately small compared to the size of the valley. Much larger discharge is necessary to explain the size of Mud Spring Canyon than could be generated from the modern basin, even during pluvial periods. (From: Reheis et al. 2002)

Seven Devil's Scenic Area

Directions: To Heaven's Gate Overlook and Trailhead: From Riggins, take State Highway 95 south one mile to the Seven Devils Road, Forest Road #517. This is a steep one-lane gravel road with turnouts and is rough for the last few miles. Although adequate for most passenger cars, it is not recommended for RVs or travel trailers. It is generally open from early July to mid-October. It is 17 miles to Windy Saddle Trailhead and generally takes one hour.

Road # 517 will fork near Windy Saddle Campground and trailhead. Take the fork to the right, past the Windy Saddle Campground and horse facilities. Continue for another 1.5 miles to Heaven's Gate Observation Site parking lot. The trail begins on the east side of the parking lot.

Description: Restroom facilities are only available at the parking lot, not at the lookout. Volunteers staff the lookout during the summer season since Heaven's Gate Overlook is one of the most popular overlooks of Hell's Canyon. The trail is short, but at a high elevation, so take your time and enjoy the amazing views.

Imagine millions year old squashed, island arc volcanoes folded and land locked and you will be picturing the Seven Devils Scenic Area. Named after seven peaks; He Devil, She Devil, Tower of Babal, The Ogre, The Goblin, Mt Belial, and Devils Throne, this scenic area has a complex and interesting geologic history.

100 million years ago, volcanic islands and their fringing reefs collided into Idaho creating tightly folded and steeply tilting layers of sedimentary and igneous rocks that make up the Seven Devils complex. Very pale gray to white limestone makes up the Martin Bridge limestone, which represents the remnants of those fringing reefs.

Basin and Range faulting helped to raise the Seven Devils Mountains high along with extensive erosion of the canyons on either side. Because the crust is floating on the mantle, when sediments are removed by erosion, a load is lifted and the crust rises. Beneath the crust, hot mantle material slowly flows in to replace where the weight of the removed load existed. The Snake and Salmon rivers are the culprits of intense erosion, the delving of deep canyons, and added uplift. 

Castle Rocks

Directions: The best access to the National Forest portion is through Castle Rocks State Park. This is a fairly new state park was designated in 2003. From I-84 in Idaho, take the Sublett Road exit toward Malta. Turn left onto Sublett Road. Sublett Road becomes Jane Lane. Travel to 4th Street, turn left on to Main Street. Turn right onto Center Street. Turn left on Elba-Almo Road, then west 1.4 miles on 2800 S. Big Cove Ranch Road.

Description: The Almo Pluton hosts the spectacular granitic rock formations in City of Rocks National Reserve, Castle Rocks State Park, and the southern end of the Albion Mountain Division of the Sawtooth National Forest. Much of the geologic story resulted from moving plates and colliding continents pushing intrusive magma to the surface where it solidified. Older rocks are around 2.5 billion years old--part of the Archean Green Creek Complex--some of the oldest in the country, but none is visible within the park boundaries. Sea deposited, fused and cemented sandstones, from around 700 million years ago, make up the Elba Quartzite, which can be seen in small outcrops around the area.

The Almo Pluton, a granitic intrusion that formed around 27 million years ago, pushed its way up through overlying rocks and sediments, makes up most of the granite of the Castle Rocks area. Effective weathering and erosion in joints of the granite created the fairy-tale resistant formations that remain today.

The brown varnish, also known as desert varnish, is iron oxide leached from the water that stains the surface of the rock and creates a erosion protective layer. In places where the desert varnish has broken or chipped away, small hollows quickly weather out.