Photograph by K. McGee on September 12, 1996

These dead and dying trees on the south side of Mammoth Mountain volcano (peak in distance) in eastern California were first noticed in 1990. Since then, about 170 acres of trees have died. When the area was examined in 1990, exceptionally high concentrations of carbon dioxide gas were found in the soil beneath the trees. What caused such high concentrations of carbon dioxide gas? The most likely sources of the carbon dioxide are (1) magma that intruded beneath Mammoth Mountain during an earthquake swarm in 1989; and (2) limestone-rich rocks surrounding the intrusion (CO2 is released from limestone (CaCO3) when heated).

More information about carbon dioxide gas in Long Valley area

• Invisible Carbon Dioxide Gas Killing Trees at Mammoth Mountain, a fact sheet
• More on carbon dioxide near Mammoth Mountain, including additional data