Undersea Mounds May Host Gas Pockets Ready to Burst

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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