- WASHINGTON (Reuters) -- Methane
bubbles from the sea floor could, in theory, sink ships and may explain
the odd disappearances of some vessels, Australian researchers reported
- The huge bubbles can erupt from undersea deposits of
solid methane, known as gas hydrates. An odorless gas found in swamps and
mines, methane becomes solid under the enormous pressures found on deep
- The ice-like methane deposits can break off and become
gaseous as they rise, creating bubbles at the surface.
- David May and Joseph Monaghan of Monash University in
Australia said they had demonstrated how a giant bubble from one of these
deposits could swamp a ship.
- "Sonar surveys of the ocean floor in the North Sea
(between Britain and continental Europe) have revealed large quantities
of methane hydrates and eruption sites," May and Monaghan wrote in
their report, published in the American Journal of Physics.
- "A recent survey revealed the presence of a sunken
vessel within the center of one particularly large eruption site, now known
as the Witches Hole."
- "One proposed sinking mechanism attributes the vessel's
loss of buoyancy to bubbles of methane gas released from an erupting underwater
hydrate," they wrote." The known abundance of gas hydrates in
the North Sea, coupled with the vessel's final resting position and its
location in the Witches Hole, all support a gas bubble theory."
- No one has ever seen such an eruption and no one knows
how large the bubbles coming off a methane deposit would be.
- May and Monaghan created a model of a single large bubble
coming up under a ship. They trapped water between vertical glass plates,
launched gas bubbles from the bottom and used a video camera to record
what happened to an acrylic "hull" floating on the surface.
- "Whether or not the ship will sink depends on its
position relative to the bubble. If it is far enough from the bubble, it
is safe," they wrote.
- "If it is exactly above the bubble, it also is safe,
because at a stagnation point of the flow the boat is not carried into
the trough. The danger position is between the bubble's stagnation point
and the edge of the mound where the trough formed," they concluded.
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