Massive undersea scars and mountains revealed by satellite mapping

Scientists have devised a map of the earth's sea floor using satellite data, revealing massive underwater scars and thousands of previously uncharted mountains in some of the deepest, most remote ocean areas.

The researchers said on Thursday they used gravity measurements of the sea floor from radar equipment aboard the European Space Agency's CryoSat-2 satellite and US space agency Nasa's Jason-1 satellite to capture underwater geological features in unprecedented detail.

"The pull of gravity reflects the topography and tectonics of the sea floor," said study leader David Sandwell, a geophysicist at the Scripps Institution of Oceanography at the University of California, San Diego.

University of Sydney geophysicist Dietmar Muller, another of the researchers, said about 90 per cent of the sea floor was uncharted by survey ships that used acoustic beams to map the depths.

"We know much more about the topography of Mars than we know about earth's sea floor," Muller said.

"The disappearance of Malaysia Airlines flight MH370 earlier this year has heightened global awareness of the poor knowledge of our ocean depths."

The map reveals major sea- floor and sub-sea-floor structures. They include a mid-ocean ridge beneath the Gulf of Mexico with a length about equal to the width of Texas, as well as another ridge under the South Atlantic west of Angola about 800km long. It was formed just after South America separated from Africa.