Deadly vapors.

Off the northeast coast of Scotland, 100 miles or so out from Aberdeen, is a mysterious portion of the North Sea known as the Witch Ground. Like the more infamous Bermuda Triangle, legends speak of ships disappearing into the area, never to be seen again. The sea floor below is pockmarked with strange craters. One of the largest, called the Witch's Hole, is located near the southern edge of the mysterious area. There, a survey from the 1970s indicated that something strange was located in the center of the hole.

This got the attention of Alan Judd, a marine geologist from the University of Sunderland. Judd believed the mysterious object to be a ship and embarked on an expedition to prove it. Sending a submersible down to investigate, Judd and his researchers watched on video screens in the mother ship above as the lights of the sub illuminated what turned out to be an 80-foot-long steam trawler sitting placidly upright, and apparently without damage of any kind, in the center of the Witch's Hole. No one knew how she came to be there, but Judd has a theory: methane gas.

According to Judd, the rugged pockmarks are evidence of recent releases of methane from the sea floor. "It is tempting to suggest that it is evidence of a catastrophic gas escape in the not too distant past," he told New Scientist in 2000. What's more, the gas releases, which would markedly reduce the density of seawater where they occur, could have led to the sinking of the trawler. "Any ship caught above would sink as if it were in a lift shaft," Judd said. And it wouldn't help the crew to wear life preservers or to take to life rafts. The reduced density of the water would mean they too would sink out of sight, to be lost without a trace.

While methane "burps" may account for some of the mysterious losses of ships in places like the Witch Ground and elsewhere, some researchers think methane long sequestered under the sea floor presents other even more serious dangers. In a theory popularized by University of California-Santa Barbara scientist James Kennett called the "clathrate gun hypothesis," rapid release of methane from gas-hydrates under the sea floor can cause rapid and catastrophic global warming.

Some say this is reason enough not to pursue commercial development of gas-hydrate reserves. "This is a technology that has the capacity to generate truly staggering environmental impacts, and most are not good," Richard Charter, an environmentalist with the group Environmental Defense, told the San Antonio Express-News. "We ought to do the science first so they don't have any big mistakes."

There is no evidence, however, that massive releases of methane from gas hydrates have ever altered the climate. According to the journal Nature, an examination of ice cores from Greenland turned up no evidence of previous catastrophic methane burps. "The data are convincing," Kai-Uwe Hinrichs, a geochemist at the University of Bremen in Germany, told Nature. "They won't exactly increase the attractiveness of the clathrate gun hypothesis."