Since 1990, high levels of carbon dioxide (CO2) in the soil have killed trees within about a 75-acre area adjacent to Horseshoe Lake on the south side of Mammoth Mountain.
Instrumentation Installed for Continuous Monitoring of Carbon Dioxide Emissions at Horseshoe Lake, Mammoth Mountain
This CO2 migrates upwards to the surface from depth beneath the mountain. In June 2013, a new measurement array was installed by the USGS adjacent to Horseshoe Lake to continuously monitor changes in CO2 emissions over space and time. At the heart of this instrumentation is a set of atmospheric sensors mounted on a tripod tower above the ground surface. These sensors make high-frequency measurements of atmospheric CO2concentrations and wind speeds and directions. Using the "eddy covariance" method, these measurements are then used to calculate rates of CO2 emission from land areas around the instrument tower (which change with atmospheric conditions such as wind speed and direction) on a half-hourly basis. Continuous monitoring of CO2 emissions should allow for better understanding of the relationships between changes in these emissions and variations in local weather conditions and activity (for example, seismicity) beneath Mammoth Mountain.