Mammoth Mountain C02 Tree Kill Zone

Part of the Tamarack cross-country ski trail system near Horseshoe Lake has been closed because of high levels of carbon dioxide in the local atmosphere produced by constant outgassings from the mountain. A large number of trees have died. The danger to humans is greatest in the winter as the carbon dioxide collects underneath the snow surface. Places where the snowcap breaks such as at restrooms or in snow holes around trees are likely spots for the heavy gas to accumulate. The death of a cross-country skier in 1997 has been blamed on these emissions. The Horseshoe Lake tree kill area is around 170 acres in size and growing.

One of the most geologically active volcanoes in the United States, Mammoth Mountain releases some 1,300 tons of carbon dioxide a day. There is some controversy as to the significance of the emissions. Some geologists have argued that they are the result of a swarm of earthquakes in the late 1980s that indicated an uprising of magma underneath the mountain. Others maintain that the emissions come from a large reservoir of carbon dioxide that has been under the mountain for some time but has only recently been breached. Scientists do agree that the carbon dioxide emissions are unusual. Tree die-offs indicating the presence of large amounts of carbon dioxide have not taken place in the area for a few hundred years and 1,300 tons of carbon dioxide is a remarkably large amount. In comparison, Mount St.- Helens emits similar quantities during low-level eruptions. Solar-powered monitoring devices, such as this one, help government agencies better understand the evolving situation.