Thursday, March 3, 2011

Scripps mapping subsea mountains taller than Mt. Whitney

Seafloor in the South Atlantic Ocean.
The low resolution map is derived from satellite altimetry while the high resolution swath was collected by Melville
during their transit across the South Atlantic from Cape Town, South Africa to Punta Arenas, Chile.

From SignonSanDiego

Mount Whitney rises 14,494 feet high in California’s majestic Sierra Nevada, making it the highest summit in the lower 48 states.
It also means Whitney is shorter than some of the undersea mountains — or
seamounts — that are now being charted by the Melville, a research vessel out of the Scripps Institution of Oceanography.

SIO officials say scientists aboard the Melville are finding seamounts as tall as 14,700 feet on a mapping mission underway in the South Atlantic.
One of the seamounts has a diameter of 87 miles, roughly the distance between San Diego and Long Beach.

“Only about seven percent of the seafloor has been mapped by ship, so there are a lot of uncharted seamounts around the world,” said
David Sandwell, an SIO geophysicist who is helping guide scientists aboard the Melville from his office in La Jolla.

“It’s important to study them. We need to understand the geology of the ocean floor.”

Sandwell says some of the seamounts are inactive volcanoes that can affect the path of ocean currents which, in turn, can affect weather and climate.
The seamounts also are gathering spots for a diverse collection of marine species, including some types of commercially harvested fish.

Locating and charting the seamounts is tricky business.
Scientists use satellite radar to study the ocean’s surface.
Those images reveal the rough location of subsea volcanoes and seamounts.
But then scientists have to go to sea and use sophisticated sonar to map the upper reaches of the mountains -- which is what researchers on Melville have been doing as they’ve explored a region 1,200 miles southwest of Cape Town, South Africa.

Sandwell said that the captain of the Melville,
Chris Curl, has to approach the seamounts carefully because the peaks can rise close to the surface, posing a hazard to navigation.
In 2005, the nuclear-powered submarine
USS San Francisco struck an uncharted seamount while operating 500 feet deep off Guam (see article).
The collision killed one crew member and injured 23 others.

J.J. Becker, a geophysicst aboard Melville, said in a statement, “These particular seamounts are so steep that it was nerve-wracking to go from 9,840 feet of water to less than 1,640 feet in 15 or 20 minutes!”

Scientists said charting the seamonts won’t be completed any time soon.

“There are many areas the size of New Jersey for which we have no information,” Sandwell said.
“That’s worse than the coverage we have for Venus and the far side of our own moon.”

The public can follow the movement and work activity on
R/V Melville online.

Links :