It Came From Beneath the Sea
(Wired) Methane bubbles from the sea floor could, in theory, sink ships and may explain the odd disappearances of some vessels, Australian researchers reported Tuesday. 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 sea floors.
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 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.”
