The floor of the ocean comes into better focus

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Undersea mountains near the Hawaiian Islands, from the Marine Geoscience Data System. Images of the mountains and nearby seafloor are derived from sonar readings taken along the paths sailed by research ships.

The bottom of the ocean just keeps getting better. Or at least more interesting to look at.

In an ongoing project, mappers at Lamont-Doherty Earth Observatory have been gathering data from hundreds of research cruises and turning it all into accessible maps of the ocean floor with resolutions down to 25 meters.

You can see some of the results here, at a mapping site that allows scientists—and you—to zero in on a particular location, zoom in and download topographical maps of the ocean floor. The Lamont data has also contributed to the latest version of Google ocean map, which now offers its own more closely resolved view of the ocean floor globally. (You can take a quick tour of the updated Google map here.)

“I love looking at everything,” said Vicki Ferrini, a scientist at Lamont who oversees the team that synthesizes the data and creates the maps. Ferrini may have absorbed more data about the ocean floor than anyone; a self-professed map and data geek, she says she has her own map of the oceans in her head.

“I really like these sinuous channels in the deep sea, they’re very cool to me. … There [are] clearly concentrated areas of energy that are able to scour these river-like features through the seafloor. And the [mid-ocean] ridges are all pretty cool.”

The new data from Lamont covers about 8 percent of the ocean floor, a fraction of the oceans, but a sizable piece overall of the earth’s surface. The data mostly comes as a byproduct of scientific expeditions that send research vessels criss-crossing the seas, explained Suzanne Carbotte, a professor of marine geology and geophysics at Lamont. The cruises may not be focused on ocean topography at all; but as the ships sail, they keep their measuring instruments humming and collect sonar data.

The sonar sends a pulse of sound down through the water column, and uses the speed of the sound’s return to calculate depth. Data from U.S. expeditions is archived by the National Oceanic and Atmospheric Administration. Lamont processes that data, gathers more from scientists around the world, and turns it into maps.

The Google ocean map, covering the entire ocean floor, relies mostly on data collected by satellite that is curated by the Scripps Institution of Oceanography, in partnership with NOAA, the U.S. Navy and the National Geospatial Intelligence Agency, with contributions from the Japan Agency for Marine-Earth Science and Technology and Australia Geosciences-AGSO. It also incorporates the more precise data from Lamont. (A video produced by Scripps at this site offers an interesting global tour of mid-ocean ridges.)

The satellite data details small changes in sea surface height which, through gravity, reflect the underlying topography of the sea floor. The latest version of the Scripps-NOAA ocean map offers a resolution of roughly 500 meters—an improvement over the earlier, 1 kilometer resolution. That means one data point for every 500-meter-square grid of the seafloor. Even that rough picture is valuable, Carbotte said. “The coarse data does a beautiful job revealing the detailed boundaries of earth’s tectonic plates and other large-scale seafloor structures, and the map covers the entire ocean,” she said.

Those measurements allowed researchers to discover a new “microplate” in the Indian Ocean—a remnant from the crustal shifts that sent the Indian subcontinent crashing into Eurasia, creating (and still forming) the Himalaya mountains. Researchers studying that plate have come up with a more precise date for when that collision began, 47.3 million years ago.

But the finer resolution mapping processed by Lamont opens up other avenues for scientists. “It allows you to study the active modern processes that shape the seafloor,” Carbotte said, like earthquakes and undersea landslides that can flush sediments across long distances.

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