Seabed of new jet search zone mostly flat with 1 trench, mostly good news for wreckage hunt

The Associated Press

This undated graphic provided by Commonwealth of Australia (Geoscience Australia) Dr. Robin Beaman, James Cook University, shows the North-westerly view of the search area for the missing Malaysian Airlines Flight 370 at Broken Ridge, south-eastern Indian Ocean, which shows the Diamantina Escarpment dropping from about 800 meters to over 5000 meters in depth. Two miles under the sea where satellites and planes are looking for debris from the missing Malaysian jet, the ocean floor is cold, dark, covered in a squishy muck of dead plankton and - in a potential break for the search - mostly flat. The troubling exception is a steep, rocky drop ending in a deep trench. The sea floor in this swath of the Indian Ocean is dominated by a substantial underwater plateau known as Broken Ridge, where the geography would probably not hinder efforts to find the main body of the jet that disappeared with 239 people on board three weeks ago, according to seabed experts who have studied the area. (AP Photo/Commonwealth of Australia (Geoscience Australia) Dr Robin Beaman, James Cook University)

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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.

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Pritchard reported from Los Angeles. Associated Press writer Matthew Pennington in Washington contributed to this report.

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