Researchers today published the most detailed map of the ocean floor ever produced. Data collected by satellites and remote sensing instruments were used to created a model at least twice as accurate as previous maps, revealing thousands of previously uncharted seafloor features in the process. And best of all, you can explore the maps for yourself!
Above: A marine gravity map of the North Atlantic Ocean Red dots show locations of earthquakes with magnitude > 5.5 and they highlight the present-day location of the seafloor spreading ridges and transform faults. This gravity information shows the details of the plate tectonic history of the rifting of these continents including the subtle signatures of fracture zones that are currently buried by sediment. | Image & Caption Credit: David Sandwell, Scripps Institution of Oceanography
Much of what we know about the ocean floor's topology we know from data collected by multibeam sonar systems. It is estimated that these sonar systems – which have to be lugged back and forth across the ocean's surface by ships in order to acquire soundings of the seafloor deep beneath them – have left a staggering 90% of the deep-sea bottom uncharted.
Now, researchers led by geophysicist David Sandwell, of Scripps Institution of Oceanography in San Diego, California, have used data collected from satellite-based radar altimeters to fill in huge swaths of missing seafloor. What's incredible is that these satellites map the ocean deep not by scanning the seafloor, but by repeatedly scanning the waters' surface. Correcting for waves and tides creates a picture of sea-surface topography that reflects features of the seafloor far below. "A seamount, for example, exerts a gravitational pull, and warps the sea surface outward," said Sandwell, in an interview with Science News, "so we can map the bottom of the ocean indirectly, using sea-surface topography."
So what has the new scan turned up? Here's Science News' Carolyn Gramling:
Among the new features they're now able to detect, Sandwell says, are thousands of previously unknown seamounts between 1000 and 2000 meters tall dotting the ocean floor. They also discovered an 800-kilometer-long now-extinct (i.e., no longer actively spreading) ridge in the South Atlantic Ocean that formed after Africa and North America rifted apart. The team also reports the exact location of a now-extinct seafloor spreading ridge, a zone where two tectonic plates began pulling apart 180 million years ago to form the deep basin that became the Gulf of Mexico. "That was a surprise to me—you'd think everyone would know everything about the Gulf because it's so well-studied," he says. "Of course, people knew it opened from seafloor spreading, but they didn't know exactly where the ridge and transform faults were." Those features were so deeply buried by sediment that the gravity signals were extremely faint.
Also cool: Sandwell's team, in addition to publishing its findings in the latest issue of Science, has put its charts online in the form of several interactive maps (overlapys can also be downloaded for navigation in Google Earth). Here's the team's vertical gravity gradient map: