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Horseshoe Lake CO2 Area

U.S.G.S scientists detected naturally occurring Carbon Dioxide (CO2) gas in the vicinity of Horeseshoe Lake and other areas on the Mountain in 1994.  Since then they have been monitoring the gas, measuring the concentration and rate of gas discharged from the ground.  The higher than normal concentrations of CO2 are responsible for killing approximately 120 acres of trees next to Horseshoe Lake and elsewhere on Mammoth Mountain. 

Scientists believe that the CO2 is being released from a gas reservior that has existed for a long period of time deep under Mammoth Mountain. It is believed that earthquake and magmatic activity beneath the area in 1989 opened channels for the gas to reach the surface. 

CO2 is heavier than air and can collect at high concentrations in depressions and enclosures, posing a potential danger to people, especially small children and pets.

General Information

Day use only: open 6:00 a.m. to 10:00 p.m.

 Wilderness permit for Red Cones Trail is required for overnight trips.

No fees are required for this site

Dogs must be leashed in all developed recreation sites.

building

Address: 2510 Hwy 203 Mammoth Lakes, CA 93546
Phone: (760) 924-5500
Hours: Daily, 8:00am- 5:00pm

Getting There

Latitude / Longitude

Latitude: 37.6129

Longitude: -119.0203

Elevation

9,100'

Directions

From the town of Mammoth Lakes, continue westward on hwy 203 as it turns into Lake Mary Road and heads into the Mammoth Lakes basin. Lake Mary road dead ends at Horseshoe Lake.

Facility and Amenity Information

Restrooms

Restrooms are available at this site.

Water

Potable water is available at this site.

Last updated April 10th, 2025