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Far out in the Indian Ocean, hundreds of miles off Australia, the search for the wreckage of the Malaysia Airlines flight is fighting mercurial weather and strong currents. The longer the search drags on, the more problematic it is getting:
The area, the location
* The main search area covered 470,000 square nautical miles in the southern Indian Ocean till Friday. It is one of the most isolated regions in the world, far from any land, airline routes.
* The predominant winds and ocean currents there would move the debris in an easterly direction from the presumed crash site. The speed would depend on the strength of winds and the speed of surface and subsurface currents. On Friday, the search area saw another shift, 1,100 km to the north-east, closer to land.
* The southern corridor of the Indian Ocean ranges in depth from 3,770 feet to 23,000 feet.
* There are volcanic ridges rising up from the ocean floor. The Southeast Indian Ocean Ridge cuts through the search area, meaning the sea bed is rugged and constantly being reshaped by magma flows. Experts hope the wreckage is lying on a flat area, as a search operation becomes complicated if objects are lodged in a ravine or mountainous area. Geological features can hinder sonar (Sound Navigation and Ranging) and obscure debris.
Search planes are having to fly with and against a wind system called the Roaring Forties, which circle the earth at 30-40 mph, moving west to east. The search area is characterised by high waves and swift undercurrents.
Ocean currents move west to east in loops and eddies in southern hemisphere, and can carry material 50-60 miles. This is the location of Indian Ocean Gyre, an area of circular ocean current.
* The plane’s black box sends out a ping — activated by immersion in water — that can be picked up. The emergency locator transmitter sends out a distress signal on impact. The voice recorder and data recorder each have their own pinger. But there’s a problem — the battery of the pinger on MH370 will only last 30 days.
* The search will try to locate the wreckage before moving in to pinpoint the black box by picking up the ping. If the pinger has expired then, other techniques — such as magnetic detection — will be necessary. But the box is small