Transcript for America\'s New Frontier, segment 05 of 11


On a typical GLORIA survey cruise the first detailed look at the ocean bottom comes when black and white photographs of the collected data are printed up and set out to dry. Again, the dark and light patterns on the GLORIA images define geological features and geological provinces occurring on the ocean bottom. This GLORIA image from the Gulf of Mexico was combined with local depth information, giving it a three-dimensional appearance. A meandering submarine channel clearly stands out because coarse sediment or sand in the channel bed reflect sound more strongly than the surrounding fine sediment which appears dark. Channels such as these exist worldwide and are thought to develop as swift sediment-laden bottom currents called turbidity flows moved down continental slopes into the deep ocean basins.

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Each day's set of photographs are eagerly awaited by the scientists in charge. The photos are cut and pasted together into a cumulative mosaic which takes shape over the month of a typical GLORIA cruise. Piece by piece, the mosaic grows to reveal a regional sound picture of the never before seen ocean bottom. The assembled shipboard mosaic answers many questions but raises many more, beginning the imagery's role as a base map for future exploration. It also ensures that there are no gaps in the collected data.

In advance of the cruise, the ship's course is carefully planned in a traversing pattern which ideally gives full coverage of the region. Like mowing a lawn, the ship moves back and forth with GLORIA in tow at about seven to eight knot speed.

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Following the GLORIA cruise, the digitally recorded data is cleaned up and processed on computers. Because the data is digital, it is easily stored and manipulated in the future. Rather than a razor blade and glue, the processors use a keyboard and toggle to assemble the sea floor images. What results is a continuous seamless map with only vestiges of the linear ship tracks which show so prominently on the shipboard mosaics. The completed GLORIA images are published and distributed as regional ocean floor atlases, both in book form and on CD-ROM computer-readable disks.