00:00:11volcanic gases escape from the magma
00:00:14they percolate through the Earth’s crust
00:00:17and into the atmosphere
00:00:33professional geologist Charles Watson
00:00:36investigates the risks at Horseshoe Lake
00:00:39close to mammoths main resort there’s
00:00:45this quiet silent killer that’s lurking
00:00:48about in the trees along the lakes edge
00:00:50in the early 1990s trees began to die in
00:00:55the area north of the lake the cause
00:00:59high concentrations of carbon dioxide
00:01:04scientists have discovered that around a
00:01:06hundred tons of the gas escapes around
00:01:08Horseshoe Lake each day raising the
00:01:13level of carbon dioxide in the soil up
00:01:16to 95 times normal levels a simple test
00:01:22of the lakeside shows what this means in
00:01:24practice carbon dioxide is heavier than
00:01:28air so what we’ve done is we’ve dug a
00:01:30hole and the carbon dioxide is gonna
00:01:32fill that up and displace the oxygen out
00:01:34and extinguish this butane lighter fire
00:01:38needs oxygen to burn starve to this the
00:01:43flame dies you won’t even realize
00:01:50high concentrations of carbon dioxide
00:01:52can kill a butane flame in seconds and
00:01:55it can have a deadly effect on humans
00:02:00the usual concentration of carbon
00:02:03dioxide in air is only point zero three
00:02:06five percent at a concentration level of
00:02:11around one percent it causes dizziness
00:02:13headaches and hallucinations above 17
00:02:18percent unconsciousness and death
00:02:21happens in a matter of seconds
00:02:26[Music]
00:02:30at Mammoth Lakes wind usually disperses
00:02:33the carbon dioxide safely but in 2006
00:02:39investigators confirmed that a lethally
00:02:41high concentration of the gas killed
00:02:43three ski patrollers who fell into a
00:02:46snow cave on Mammoth Mountain and there
00:02:49was no volcanic eruption
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