Mammoth Area's Beauty Masks Its Natural Dangers
The deaths of three ski patrol members at Mammoth Mountain on Thursday highlight the many hazards facing those who live, work and play atop one of the nation's largest active volcanic systems.
Earthquake swarms, toxic gases that are deadly when concentrated, the unlikely event of a cataclysmic eruption -- such risks are permanent features of life in the exquisitely scenic area.
Geologists, public safely officials and resort managers do their best to protect residents and visitors from the dangers, but deaths do occasionally occur.
Eight years ago, a healthy 58-year-old man from Torrance, who was cross-country skiing in the nearby Horseshoe Lake area, was found dead. His death was believed to have resulted from breathing carbon dioxide gas, according to the Mono County coroner.
The fumes that emanate from volcanoes include the potentially lethal gases carbon dioxide and hydrogen sulfide, which gives the fumes their characteristic rotten-egg smell. Both are denser than air, so they tend to sink and pool in hollows where volcanic heat has melted the snow.
At the volcanic vent, or fumarole, where Thursday's accident occurred, the emissions measured there in 2002 were 98% carbon dioxide and 0.005% hydrogen sulfide, said Dave Hill, a U.S. Geological Survey scientist who is in charge of the observatory in the Long Valley Caldera, the volcanic basin that includes the Mammoth area.
Though we exhale carbon dioxide and take in a small amount (0.03%) with each breath of fresh air, carbon dioxide levels of just 10% to 20% can be lethal. Hydrogen sulfide can be lethal in far lower amounts.
"At high concentrations, CO2 displaces oxygen from your lungs. At 70% or 80%, it just takes a couple of breaths," Hill said. "People can expire very quickly."
The areas that emit gases can shift as magma rearranges itself within the belly of a volcano, but they are relatively stable.
"Generally, the places with high gas output are known, but from time to time, new areas can develop," said Jake Lowenstern, a geologist in charge of the volcanic observatory at Yellowstone National Park, the country's largest active volcanic system.
Partly because of Yellowstone's flat topography near thermal areas and because of the area's prevalent winds, there has been only one recorded death due to volcanic gases at the park, and that was in the 1930s.
