Flora Graham, deputy editor, newscientist.com
(Image: James Glaeser/Northwest Hydro/NOAA)
Looking like the weathered skeleton of some ancient dinosaur, the rusting remains of an American Civil War battleship have been imaged in their underwater grave by 3D sonar.
The USS Hatteras sank during battle with the CSS Alabama in 1863, coming to rest in 17 metres of water in the Gulf of Mexico, 30 kilometres off the coast of Galveston, Texas. One hundred and fifty years later, the bones of the iron-hulled paddle-wheel steamship have been mapped by the US National Oceanic and Atmospheric Administration (NOAA).
NOAA made the scans after local underwater photographer Jesse Cancelmo noticed that recent storms had shifted some of the sediment and sand that covered the wreck. The main image above shows the curved tooth-like outline of the stern on the right. The paddle-wheel shaft stretches from the top to the bottom of the picture, where the remains of the port paddle wheel lie crumpled like the bones of a skeletal hand. More than half of the ship still lies beneath the seabed.
This side-on view of the paddle-wheel shaft also shows the ship's broken stern in the distance (Image: James Glaeser/Northwest Hydro/NOAA)
"Most shipwreck survey maps are two-dimensional and based on observations made by sight, photographs or by feeling around in murky water while stretching a measuring tape," said James Delgado of NOAA's Office of National Marine Sanctuaries. "Thanks to the high-resolution sonar, we have a three-dimensional map that not only provides measurements and observations, but the ability for researchers and the public to virtually swim through the wreck's exposed remains and even look below the surface at structure buried in loose silt."
The Hatteras can't be disturbed due to its status as US navy property and a war grave - two of its engine-room crew killed in the battle with the Alabama are believed to lie buried inside the hull. This made the 3D sonar scan particularly well suited to mapping the wreck, because it's completely hands-off.
In 2002, NOAA raised the revolving gun turret from the USS Monitor, another naval icon of the Civil War.
Innovative scanning methods also recently revealed the ancient burial chambers under the earth mounds of Orkney, Scotland.
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