The Tree-Kill at Horseshoe Lake: Invisible Danger
Near Mammoth Lakes, California
At the edge of Horseshoe Lake you will notice something eerie, a patch of forest where the trees stand bare and dead, no needles, no green, just gray trunks. They were not killed by fire or drought. They were killed by the volcano breathing.
After a swarm of earthquakes shook Mammoth Mountain in nineteen eighty nine, magma shifted underground and began releasing carbon dioxide gas, which seeped up through the soil. Carbon dioxide is heavier than air, invisible, and odorless. In the ground it smothers tree roots by crowding out oxygen, and it has killed roughly one hundred seventy acres of forest across several patches, the largest right here at Horseshoe Lake.
Scientists have measured soil gas here that is more than half carbon dioxide, concentrations high enough to be deadly. This is not only a hazard to trees. In nineteen ninety eight a cross-country skier was found dead in this tree-kill zone, killed by the gas.
Years later, in April of two thousand six, a far worse tragedy struck higher on the mountain. Three ski patrollers died when they fell into a gas-filled fumarole hidden beneath the snow near the summit, one of them a rescuer who went in to save the others. The Forest Service now posts warnings here.
Stay out of low hollows and snow pits where the invisible gas can pool.
