Mapping Massive Undersea Mountains

Chris Curl (left), captain of Melville, and geophysicist J.J. Becker.

Humanity often thinks it has explored to the known reaches of our world; seen everything there is to see, and now we’re just waiting for better space travel. However researchers aboard a Scripps Institution of Oceanography research vessel are mapping a series of mammoth and previously uncharted undersea mountains in the South Atlantic Ocean.

Located approximately 1,200 miles southwest of Cape Town, South Africa, the undersea mountains stretch to more than 14,700 feet from the seafloor.

These mountains had been known to exist thanks to satellite data, but had never been charted at sea.

To get just an idea of how tall and step these mountains are, geologist J.J. Becker, who received his Ph.D. from Scripps in 2008, and who is working alongside R/V Melville Captain Chris Curl, noted that “these particular seamounts are so steep that it was nerve-wracking to go from 3,000 meters (9,840 feet) of water to less than 500 meters (1,640 feet) in 15 or 20 minutes!”

Working alongside Becker and Curl, though from the safety and comfort of his office at the Scripps campus, David Sandwell, a Scripps professor of geophysics notes that “there are still 4,000-meter-tall undersea mountains that have never been charted by anyone. These are really huge seamounts that are somewhat known from satellite altimetry, so the ship data confirm their size and provide accurate measurements.”

The current exploration is the result of good planning and a little luck. Sandwell had provided a proposed trackline that the ship might travel which would allow them to explore uncharted undersea features. However almost immediately upon setting out, the Melville encountered bad weather and had to renavigate.

Using multibeam sonar, Scripps R/V Melville is charting giant undersea mountains.

“This is a great example of how serendipity and skill are involved in successful exploration and discovery,” said Bruce Appelgate, associate director for Ship Operations and Marine Technical Support at Scripps. “Dave Sandwell used the satellite data to create a great precruise plan, but the seas forced us to abandon that for a different path. Good oceanographers that they are, he and J.J. Becker were ready with contingency plans that have yielded spectacular results.”

“They are so big they actually deform the lithosphere they sit on, and they have a profound effect on the physical oceanography and biological ecosystems around them,” Appelgate. “Satellite altimetry has detected about 13,000 seamounts, but the total number of seamounts taller than one kilometer probably exceeds 100,000. So clearly these are important, and you need ships like Melville, and scientists like Sandwell and Becker, to go find them.”

Source: University of California, San Diego

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