The Diamantina trench, named after an Australian navy vessel, is one of the deeper sections of the parts of the oceans that surround Antarctica, according to Mike Coffin, the executive director of the Institute for Marine and Antarctic Studies at Australia's University of Tasmania.
The trench's rocky crags and crannies would make it difficult for ships using instruments like side-scanning sonar or multi-beam echo sounders to distinguish any debris from the crevices.
Searchers will especially be hoping to locate the jet's two "black boxes," which recorded sounds in the cockpit and data on the plane's performance and flight path that could help reconstruct why it diverted sharply west from its overnight flight from Kuala Lumpur, Malaysia, to Beijing on March 8. The black boxes were designed to emit locator pings for at least 30 days, and are projected to lose battery power — and thus their pings — by mid-April.
The pinger can be heard as far as 2 1/2 miles away, but the distance can vary widely, depending on the state of the sea and the wreckage location, said Joseph Kolly, director of research and engineering for the U.S. National Transportation Safety Board. Black boxes can get buried or muffled by other wreckage, and thermoclines, which are layers of water with great variations in temperature, can refract the signal, he said.
The sediment on Broken Ridge is unlikely to inhibit the ping — but on the escarpment or in the trench, rocks could scatter the sound, making it harder to detect, according to Mike Haberman, a research scientist specializing in acoustics at the University of Texas, Austin.
To pinpoint the ping they hear from the surface, searchers likely will run a submersible equipped with sonar several hundred feet above the ocean floor. The unmanned underwater vehicle will putter along at a slow jog, able to "see" objects on the floor that may seem out of place. But its vision is limited — in a day it could cover an area only about the size of Manhattan, Sager said.
The observations stored in the vehicle's memory can be accessed only by bringing it to the surface.
Under the best conditions, to survey the entire new search area could take between three months and up to nearly two years, depending on the quality of data needed to identify the debris, according to calculations by David T. Sandwell, a professor of geophysics who specializes in seafloor mapping at the Scripps Institution of Oceanography in San Diego.
Because it is such a painstaking — and expensive — process, most mapping has been focused on things that people consider useful, like underwater shipping hazards and potential oil deposits. With nothing much to interest people in the this part of the Indian Ocean, the maps tend to follow features like the volcanically active mid-ocean ridges, leaving big blank spaces in between.
There are 80-kilometer (50-mile) -wide strips of the search area where no shipboard measurements have been taken and scientists use less detailed satellite measurements and educated guesswork to depict what the floor actually looks like.
Precisely what the seafloor looks like in detail in the area of the new search is another in a long line of Flight 370 mysteries.
Pritchard reported from Los Angeles. Associated Press writer Matthew Pennington in Washington contributed to this report.
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