Data gathered by satellites capable of the most detailed measurements of the Earth's gravity has produced maps giving us the clearest view to date of the shape of the world's seafloors, scientists report.

Towering volcanoes and mountains, some nearly a mile high, lie hidden beneath the waves of the world's oceans, as do deep, giant chasms where ancient supercontinents ripped apart, the new detailed maps reveal.

The maps, published in the journal Science, feature resolution twice that of anything available before, says marine geophysicist and lead study author David Sandwell of the Scripps Institution of Oceanography in La Jolla, California

"I think these data are pretty important in terms of the details that are going to come out," he said.

The maps were created using gravity models of the world's oceans based on radar altimetry data from the Cryosat-2 and Jason-1 satellites.

The satellites use radar signals to determine height of the sea surface, which in very subtle variations in its highs and lows reflects the topography of the underlying seafloor as well as Earth's gravitational field.

The resolution of the new maps has allowed scientists to increase the count of known undersea volcanoes from about 5,000 seen in previous mapping efforts to around 20,000, the researchers say.

The highly-detailed maps also provide a new look at the seafloor features created by the movements of Earth's tectonic plates.

Spreading ridges and fracture zones are seen where plates are created and then recycled into deep trenches, just as scientists have long believed.

"Even now, I'm just amazed by how simple seafloor spreading patterns are," Sandwell said. "They're just like in the textbooks. It's just perfect plate tectonics."

Much of the new topology coming to light was invisible to previous technologies used to scan the seafloor, the researchers said.

This is particularly true around the coastlines of the globe's continents, where the topology is buried under thick layers of sand and mud pouring off of the continents.

Previous technologies, such as echosounders towed through the water beneath a ship, could only see the surface of such sedimentary layers, missing the true nature of the seabed beneath.

The gravity-measuring satellites have provided a way to look through the mud and sand to reveal the true contours of the sea bottom underneath, researchers said.

The new maps will advance our knowledge of the world under our feet -- or in this case under our oceans, scientists say.

"You may generally think that the great age of exploration is truly over; we've been to all the remotest corners of continents, and perhaps one might think also of the ocean basins," says Dietmar Muller of the University of Sydney. "But sadly this is not true -- we know much more about the topography of Mars than we know about the seafloor."