Methane hydrate musings

[William Beaty <billb@eskimo.com>]

WARNING: if you hate far out speculations, delete before reading, this
one's a doozy.


Did anyone catch the article in the last Sci News on Methane Hydrate
deposits on the ocean floor?  This was also mentioned in earlier articles
on Black-Smoker chemosynthetic life.

This article, along with something I read in the Corliss "Science
Frontiers" book of anomalies, made me see an interesting possible
connection. The lake Nyos disaster, where eruptions of C02 gas asphixiated
people in the Cameroons, perhaps has an analog in the Atlantic ocean.

In lake Nyos, volcanic C02 slowly filters up into the lake water from
below, until the lower portion of the water is supersaturated.  If
something disturbs this water and causes an upwelling, the water will
effervesce.  The reduced density of the bubble-filled water initiates a
vertical self-perpetuating plume of deep-lake water, somewhat like the
"draft" effect which makes fireplaces burn well, and which makes
firestorms possible.  The column of vertical flow pumps water up from
below, and the evolution of gas bubbles powers the pumping action.  This
effect continues until the high-CO2 water from below is exhausted. A deep
pool of CO2 spreads across the countryside. 

> From what I gather from the Corliss and the Sci News articles, a similar
thing might possibly happen in the Atlantic, but with methane, not C02. 
Methane slowly diffuses upwards from deep sources.  If the water
temperature is low, the methane causes the formation of water/methane ice,
Methane Hydrate, which has a melting temperature higher than 0C.  Great
volumes of this substance build up in the sea floor.  Methane hydrate
makes for an unstable situation, since it is at the bottom of a body of
water, and if it melts it can release 10 to 50 times its volume in gas. 

Suppose that after enough time has passed, just the slight bubbling from
the material is enough to start a vertical density current.  If this
current strips the mud off the Methane Hydrate deposit and fans it with
slightly warmer water, it will trigger melting and gas release, and start
a self-perpetuating plume of bubble-filled water.  An underwater hurricane
is created, with a shape somewhat like a firestorm: flow along the surface
directed radially inwards, with a large vertical density current at the
center.  The rapid flow and turbulence would keep exposing more "fuel" 
until the deposit of Methane Hydrate was depleted, and the end result
would be an enormous volume of bubble-filled water making its way upwards. 
When fluid of one density moves through another with different density,
the moving fluid usually takes the shape of a ring vortex.  So, the rising
plume of bubbles would take the shape of an underwater mushroom cloud. 

What phenomena might this create?  For one, it might be the cause of the
unexplained "barsial guns," the loud booming sounds sometimes heard on the
east coast, coming from out at sea.  These sounds were dismissed as being
sonic booms from the Concorde, but followups showed that the reports
didn't mesh with the timing of Concorde flights.  Also, reports of "water
guns" go quite a ways back in history.  The speed of sound is vastly
slowed in bubble-filled water, so the resonant volume and the turbulence
that occurs when the giagantic foam ring-vortex connects with the surface
could easily create deep booming sounds. 

Another possibility.  What happens if a ship has the bad luck to be at the
site where the methane bubble cloud meets the surface?  The methane plume
is basically a low-density foam.  A ship probably wouldn't float in it. 
During the eruption, the bouyant force of the ocean would be reduced, and
this as well as the turbulence might be enough to sink a ship. 

After the eruption, the volume of methane gas might extend high enough to
stall aircraft engines.  And any ship or plane crews encountering the
high-methane zone might be subject to anoxia.

So... if methane eruptions in the Atlantic correspond to CO2 eruptions in
the "killer lakes" in the Cameroons, then the Lake Nyos disaster
corresponds to mysterious disappearences of ships and planes off the
Atlantic coast.  Methane Hydrate fuels the Bermuda Triangle!

Seriously now, if such a phenomenon is taking place, Navy hydrophone
arrays must hear the smaller of these eruptions all the time.  My
experience with such things is limited to the book "Hunt for Red October,"
where the US submarine's AI software was frequently discarding signals as
"volcanic origin."  If the Navy is after enemy subs, then even something
as fantastic as ship-swallowing gas eruptions might commonly be ignored.

Perhaps evidence of methane eruptions might also have been captured by
satellite photographs.  Circular white blotches, hundreds of feet across,
sitting out in the ocean for no good reason.

Last tidbit: Corliss mentioned Methane Hydrate as an explanation for
large, shallow craters which showed up in side-scan sonar plots of the
ocean floor in the UK's North Sea.  These depressions were far too large
and too deeply submerged to be whale feeding marks.  The North Sea has
quite large petroleum deposits, I believe.  If methane eruptions exist,
they probably follow a fractal buildup/release pattern similar to that of
earthquakes.  If so, there should be "microtremors" and "megaquakes",
small craters and large craters, and every size in between, in
self-similar size distribution.  A side-scan image would look like the
Moon's surface.  Perhaps only the mega-plumes are of any danger to
shipping.  Small plumes would disperse before reaching the surface. 

To test all this speculation, all we need do is take a trip out to a
likely Methane Hydrate deposit and disrupt the bottom a bit.  Dumping a
few thousand pounds of rocks might trigger interesting effects.  Wait
around a few hours and see if your craft suddenly founders in a huge
eruption of bubbles. 

......................uuuu / oo \ uuuu........,.............................
William Beaty  voice:206-781-3320   bbs:206-789-0775    cserv:71241,3623
EE/Programmer/Science exhibit designer        http://www.eskimo.com/~billb/
Seattle, WA 98117  billb@eskimo.com           SCIENCE HOBBYIST web page