BEA Interim Report n°2 stated that "There are depth variations of between 700 metres and 4,300 metres over short distances." The 1991 UNESCO report of the Russian multibeam explorations along the Mid-Atlantic Ridge (thanks to Machaca for the reference in post #766) includes a contour map of the area covered by the vessel Strakhov: there are some amazing tall peaks and steep deep valleys in this part of the Atlantic. The black areas are where contour lines are so close they bleed together in the UNESCO printout. The BEA areas of interest for continuing Phase Three search (Areas 1, 2, and 3, in yellow in the image below) unfortunately lie a bit eastward of the Strakhov data. Paull had suggested that it's mathematically possible (using the "CUBE" algorithm) to overlay two terrain data sets and look for differences and that the technique is commonly employed to discover changes in features and terrain over time. Makes sense -- that's how the tax assessor already knows about your swimming pool. But using lat/long coordinates from mm43's #764 post to scale the current AF447 search effort (posted yesterday at the BEA site) onto the Strakhov chart, it seems there is not much overlap.
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It was the black areas of the Russian contour map that brought reality home: "Debris field" becomes an oxymoron when there are few fields among the steep slopes. In a flyby, one moment you are peering at the top of a mountain peak, next you are looking a couple of thousand meters into the abyss. The recent BEA video included shots of crew at work and the Fledermaus 3D visualizer was showing peaks, but there was a tremendous amount of "undefined" hazy blue down into those valleys:
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Hats off to the BEA and the French government for pursuing this incredible search! Hats off and cheers to the French experts and the WHOI multibeam team for their dogged persistence at sea. I'd chip in to establish a new explorer's prize for these guys, even if they don't get lucky. Both the reason for this search and the search itself are playing out at the very edge of our technical capabilities and knowledge.