Seafloor Still About 90 Percent Unknown, Experts Say

February 17, 2005

The U.S. nuclear submarine San Francisco crashed into an uncharted underwater mountain in the South Pacific last month, killing one submariner and injuring dozens of others.

The incident remains under investigation, but it spotlights a troubling nautical reality—we may know more about the geography of the moon than that of the ocean floor.

Geophysicist Walter Smith is with the National Oceanic and Atmospheric Administration's Laboratory for Satellite Altimetry in Silver Spring, Maryland.

He says that even a compilation of all historical data gathered by ships, no matter how primitive, would leave much of the ocean floor uncharted.

"If you make an estimate using all the historical data in a place like South Pacific, and compare it to the United States at the same scale, it looks a bit like the interstate highway system," he explained. "It's like sending surveyors out and saying that every few miles they can measure the height of the ground, but [they can] never leave the interstate highway system—then asking them to come back and make a map showing all the geographic features of the United States."

In such a scenario the Grand Canyon, among thousands of other features, would be unknown.

Estimates vary, but the amount of properly mapped seafloor in the public domain is likely around 2 or 3 percent.

Classified military information could boost that figure to as high as 10 percent, although even the percentage tends to be obscured in layers of secrecy.

The result is that current navigational charts are a mixed bag, often recycling data from primitive surveying techniques of past decades or even past centuries.

Surveys Are Accurate, but Oceans Are Vast

Survey ships equipped with sound-based systems can map the seafloor with striking accuracy.

"We can measure in the deep ocean with accuracies to 0.5 percent of the water depth with a really good system," said Jim Gardner, a research professor at the University of New Hampshire's Center for Coastal and Ocean Mapping/Joint Hydrographic Center. The Durham, New Hampshire-based center is operated in partnership with the U.S. National Ocean Service.

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