Geologic Summary: The beautiful blue pools and impressive boiling fountains along Hot Creek have provided enjoyment to generations of visitors, but they have also been the cause of injury or death to some who have disregarded warnings and fences. The springs and geysers in the stream bed and along its banks change location, temperature, and flow rates frequently and unpredictably. Fences that previously protected the public now run through active hot pools. The fences and new pools emphasize how this geologically active area has been changing in our lifetime. The thermal aquifer that supplies the hot water to Hot Creek flows eastward from the West Moat. The hot springs and geysers of Hot Creek are visible signs of dynamic geologic processes in this volcanic region. Mammoth Creek, which flows through the town of Mammoth Lakes, changes its name to Hot Creek in Hot Creek Gorge where it intersects a series of faults that provide pathways to the surface for heated (geothermal) water flowing in an aquifer several hundred feet beneath the surface. Numerous older white (travertine) deposits surround extinct hot springs at higher levels along the gorge floor. Two images showing Hot Creek and Hot Creek with a geyser in it. The difference in temperature between the two images is over 100 degrees F in about 5 seconds. Thermal springs issue from the stream banks all along Hot Creek Gorge, but the largest and hottest springs are localized on two north-trending earthquake faults. The boiling pools in the gorge (93°C, 199°F at this elevation) commonly change in vigor and configuration in response to local earthquakes. They are also significantly affected by small and seasonal changes in the water level of Hot Creek. Travertine (white calcium carbonate deposits) lines the pools. Presumably magma beneath the Long Valley Caldera is the heat source for the hot springs, fumaroles, and areas of active hydrothermal alteration. The residual magma beneath the Resurgent Dome is unlikely to erupt in its current state after cooling for hundreds of thousands of years. Geology of the path to the creek: Water in Hot Creek Gorge has incised the Hot Creek lava flow (Doe Ridge on the map), which erupted about 333,000 years ago (sanidine Ar dated) on the shore of Pleistocene Long Valley Lake. The flow went northward into the lake and cooled quickly. The rock was later altered by lake water and hot-spring activity. Outcrops of the partly altered flow are exposed along the paved trail leading to the bottom of the gorge. For more information, please see the Fact Sheet, “Boiling Water at Hot Creek–The Dangerous and Dynamic Thermal Springs in California’s Long Valley Caldera.” References 2007, Boiling Water at Hot Creek–The Dangerous and Dynamic Thermal Springs in California’s Long Valley Caldera, U.S. Geological Survey Fact Sheet 2007-3045. Field Stop Location: Hot Creek Quadrangle: Whitmore Hot Spring, California 7.5 minute topographic quadrangle Coordinates: 37°39.620′ N, 118°49.661′ W Approximate Elevation: 7,093 ft (2,162 m) Directions to Hot Creek: Hot Creek Geologic Site is accessible by a 3.4 mile dirt road off of U.S. 395 near the Mammoth Lakes airport. The path down to the creek is steep and many adults find themselves needing to catch their breath on the way back up. Directions from Mammoth Lakes exit U.S. 395 and CA-203 Go this distance 1. Zero your odometer at the intersection of Highway 395 and Highway 203. Head south on US-395 towards Bishop. Go 5.4 miles 2. Turn left (north) onto Benton Crossing Road (the Mammoth Lakes Airport Exit at 37°37.785′ N, 118°51.854′ W). Go 1.2 miles 3. Slight left at Whitmore Tubs Road. Go 2.7 miles 4. Sharp left at Hot Creek Hatchery Road. Go 0.9 miles 5. Turn left to stay on Hot Creek Hatchery Road. Go 0.1 miles 6. Turn into Hot Creek Geologic Site parking lot (on the left), which overlooks Hot Creek Gorge. Park and walk to the overlook to view the hot pools below. Another overlook up the path to the right provides another equally impressive view of the linear hot spring activity. Follow the path down to the creek to see the activity from a variety of perspectives. The path down to the creek is steep and many adults find themselves needing to catch their breath on the way back up.