“The way we’re doing that is to use a satellite altimeter, a radar to map the topography of the ocean surface.Now that seems sort of strange that you'd map the topography of the ocean surface when you really wantted get at the sea floor. But, the ocean surface topography has these bumps and dips due to gravitational effects that mimic what’s on the sea floor.”
The scientists collected and studied information fromtwo satellites. Some of the data came from theEuropean Space Agency's Cryo-2 satellite. It wasplaced in Earth’s orbit to watch sea ice. The othersatellite is the American space agency’s Jason-1. It isstudying the surface of the oceans. Scientistscombined the satellite data with images gathered bysonar equipment on ships. Sonar works by sendingsound waves through the water. When the soundwaves hit an object, its presence is confirmed.
“That enables us to look at smaller-scale features andalso features that are buried by sediments in the oceanbasins.”
The new map shows the sea floor as it has never been seen before. It showsthousands of underwater mountains and places where continents pulled apart. It shows where earthquakes were active many years ago. They all are burieddeep underneath the ocean floor.
In one place, three mountain ridges join at the same area. Huge tectonicplates can be seen clearly there.
“It’s called the Indian Ocean Triple Junction. It’s one of my favorite spots in the ocean because it really displays the theoretical aspects of plate tectonicsperfectly. You have three plates -- the African plate, and the Indo-Australianplate and the Antarctic plate -- all connected at this one point in the center of the Indian Ocean.”
David Sandwell says the map is a powerful tool for fisheries, those interestedin protecting the environment and for oil exploration.
“(The) petroleum exploration industry is interested in how to reconnect thecontinents, bring them back together tectonically so you can map the basins(on) one continental margin -- say, Africa -- and use that to establish wherethe similar basin would be on the other continental margin in South America.”
If scientists know that information, they may be able to find oil fields.
The new data also will help scientists improve their estimates of oceandepths. This information can help ships travel safely and improve militaryoperations and scientific projects worldwide.
“This new gravity map really provides a reconnaissance tool for planningshipboard surveys. You don’t have to go out with your ship and start lookingfor something new -- we can target that with the gravity and then go out withthe ship and do the high resolution survey to really understand thesefeatures.”
Mr. Sandwell thinks scientists will make many more discoveries as theyexamine the new map and the information it provides.
The work is described in the journal Science.