Undersea Mounds May Host Gas Pockets Ready to Burst

When Edward A. Keller got his first look at some recent high resolution images of the ocean floor off Santa Barbara, Calif., he saw things that were surprising, exciting, and a little unsettling.

For openers, he saw what he believes to have been an ancient island, buried under the sea for thousands of years.

And he saw huge craters, one measuring at least 1,500 feet across, scattered along an earthquake fault zone like a series of open pits left behind by some aquatic miners.

He also saw mysterious mounds pushing up from the ocean floor, one more than 600 feet in diameter, and at first he didn't have a clue as to what they were. After many months of pondering the evidence, the UC Santa Barbara geologist is fairly convinced now that the mounds conceal pockets of gas that could rupture through the ocean floor with possibly disastrous consequences for anyone unfortunate enough to be directly over them.

A huge pocket of methane, suddenly bursting to the surface, would create a gaseous hole in the water so large that even an oil tanker could plunge into it and sink, Keller says.

"If enough bubbles come up, the water loses its buoyancy, and you can imagine a huge amount of methane coming up in a concentrated area," he adds. "If there was a boat there, it would lose its buoyancy and sink."

Is that very likely?

Probably not, Keller says.

"There's not a bunch of shipwrecks out there," he says.

Mysterious Deep Sea Slabs

But the fact that he can't rule it out has given rise to speculation that if the Earth burps at just the right time, ships — and even airplanes suddenly deprived of oxygen because of a flood of methane — might sink or fall out of the sky. There is even speculation that such events might explain the lost ships and aircraft in a region of the Atlantic known as the Bermuda Triangle, made famous by a pulp magazine article in 1968.

Adding to the speculation was the discovery of a sunken fishing boat near a sub sea crater off Great Britain in the North Sea. That crater looks very similar to the craters now known to lie off the coast of Santa Barbara.

Of course, many scholars scoff at the idea that there is anything unusual about the shipwrecks off the southeastern coast of North America in a region known variously as the Bermuda Triangle and the Devil's Triangle. But mysteries tend to die slowly.

As for Keller, he's got his own set of mysteries, mainly the strange structures he has found on the floor of the Santa Barbara Channel.

Keller has been studying earthquake hazards in that region for more than a decade, and he has recently been focusing on two offshore faults, called the Oak Ridge and Mid Channel faults, which are capable of producing a major quake. In fact, one of the faults may have caused a 1925 temblor that nearly destroyed the community of Santa Barbara.

"While I was studying these faults, the Monterey Bay Aquarium Research Institute gathered a lot of really high resolution topographic data for the bottom of the channel," he says. The institute was founded by the late David Packard of Hewlett-Packard fame, and it has some of the best marine research equipment in the world.

The exquisitely sharp images revealed a bottom that "looked strange," Keller says. The data revealed a 1.25-mile-long slab of rock jutting up from the bottom.

"There's abrupt cliffs, about 30 feet high, around it," Keller says. "It came to my mind that maybe we were looking at something like a sea cliff."

Submarine Captures Evidence

The most logical explanation for the cliffs is erosion caused by punishing waves like those that batter Southern California's coastal bluffs today. But that couldn't explain the cliffs in the present situation, because the flat top of the rock slab is 300 feet under the water.

But that might not always have been the case.

Some 15,000 to 20,000 years ago, when the Earth was going through an ice age, so much seawater was locked up in glaciers that sea level was about 400 feet below what it is today, according to many who have studied the record. That would have left about 100 feet of the rock slab sticking out of the sea, thus allowing erosion to gnaw away at its edges and create the cliffs that can be seen today, far below the water.

Recently, the Monterey Bay Aquarium Research Institute sent a remotely operated sub to take a closer look at the craters and mounds that have so intrigued Keller and his colleagues at the university. The sub captured video images of methane gas, seeping out of one of the craters.

There is a huge oil field in the area, and methane gas is always found in oil-bearing strata, so that finding was not particularly surprising. But the fact that it was coming out of a crater suggests that sometime, perhaps long ago, the crater was a mound like the others seen in the area today.

Then, possibly because of an earthquake, the mound ruptured and an explosion of natural gas blasted to the surface.

That's all just theory at this point, Keller says, but it could explain the craters and the mounds. It may be that such events happen only once every few thousand years, but no one knows for sure.

So Keller will spend the next few years studying his craters and mounds, and of course, his new island. He has even given it an unofficial name: "Isla Calafia."

As legend has it, Calafia was a beautiful warrior queen who ruled a utopian island empire, and is believed to be the source for the name California. Now she's just a sunken island.

Lets hope she doesn't burp anytime soon.

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