Bill Beaty's note on liquid CO2 at ocean depth reminded me of two
related phenomena. A case of mass deaths by asphyxiation occured
in 1986 at Lake Nyos, in Cameroon, West Africa. Tons of carbon
dioxide of volcanic origin held in solution under pressure at the
bottom of Lake Nyos convected upward to depths where they were no
longer held in solution, and flowed silently down a canyon and
through 3 villagesoccupied by 1700 people. They and 3000 cattle
died from lack of oxygen. This same sort of instability occurs
with methane at depth in the sea. The methane is dissolved in
water (or "aquated"), a combination that is stable at high
pressure, but if the pressure diminishes it can rise rapidly to
the surface as methane coming out of solution reduces the density
of the liquid. The result on the surface would be foamy water of
density insufficient to float a laden vessel. This aquated
methane is known to occur at several places on the ocean floor.
I don't know how deep Lake Nyos is, but it occurs to me now that
what Bill saw in Science News might well be the mechanism that
operated in Lake Nyos if it is about 1200 feet deep.
I know Bill's example was produced by man, but Nature can produce
many surprises of her own.