Killer Lakes | National Geographic

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