Geological forces at work on the continental margins
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Geological forces at work on the continental margins.

May 19, 2010
Geological forces at work on the continental margins. Pictured, a seascape near Oregon.

More About this Image: Off the coast of Oregon, two of Earth's crustal plates come together. The North American Plate rides roughshod over the Juan de Fuca Plate, pushing it down into the earth's interior and in the process, scraping up sea floor sediments and leaving them in piles similar to the folds in a carpet.

The computer-generated picture of Oregon's seascape is one of several views of continental margins that Lincoln Pratson, a geologist at the University of Colorado and the National Oceanic and Atmospheric Administration (NOAA), and his colleague William Haxby, studied while they both were at the Lamont-Doherty Earth Observatory. Other sites include the Florida and Louisiana coasts.

Collection of data used in creating these pictures began in 1983 when president Ronald Reagan declared that the nation's boundaries extend for 230 miles off any U.S. shore. The U.S. Geological Survey performed the general mapping, while NOAA and scientists--supported by NSF--used multi-beam, echo-sounding systems to get high resolution images.

Using several data sets, Pratson and Haxby evaluated the continental margins at five survey sites. The images show the naked forces of geology. Tectonics, sedimentation and lithology (the structure and composition of rocks) have all been stripped of trees, grasses and other appendages of land, revealing their raw power and unexpected variety. For example, a site off the western coast of Florida contrasts sharply with its nearby state. Instead of Florida's uniform, gentle slopes, the continental margin has sharp edges and mile-high cliffs that drop to the abyss below.

Aside from the accompanying analysis providing new tools in the study of ocean floors, Pratson expects the images will assist companies considering gas or oil exploration and those laying transcontinental cables.

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