A year ago, a team that includes Kennedy and researchers at the U.S. Geological Survey and Lawrence Livermore National Laboratory surveyed soil gases in these areas. They found carbon dioxide concentrations ranging from about one percent in healthy forest to as high as 90 percent within tree-kill areas. Where concentrations were above 30 percent, most trees were dead. Kennedy's research indicates that the carbon dioxide soil gas in the tree-kill zones is mostly of volcanic origin. Aside from carbon dioxide, no other lethal gases were detected.
Researchers believe high concentrations of carbon dioxide kill plants by inhibiting root function.
Mammoth Mountain, which is about 30 miles south of Mono Lake, is part of the Long Valley caldera that was formed about 760,000 years ago during an eruption that was 500 times larger than Mount St. Helens. Smaller eruptions have occurred in the area as recently as 500 years ago. Researchers report that the total discharge of carbon dioxide from the 75 acres involved in the vegetation die-off is at least 1,200 tons per day. This is comparable to that seen during low-level eruptions of a number of volcanoes including Kilauea, Augustine, and Mount St. Helens. Scientists say there are no signs of an imminent eruption at Mammoth Mountain.