Canyons: Windows Into the Deep
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Like most ocean floor near coastlines, the ocean floor in the Gulf of Maine is relatively flat, with an average depth of 150 m (450 feet). This represents the continental shelf, the flat or slightly sloped portion of the ocean nearest the coast. In the Gulf of Maine, the continental shelf extends a few hundred miles outward from the coast. At the end of the continental shelf, the ocean floor drops off fairly rapidly in what is called the continental slope. |
| The continental slope is cut through along its edge at many places by deep rifts called submarine canyons. Differing theories exist as to how various canyons were formed. Some seem to have been formed as sediment from river basins was carried out to a shallower ancient sea and scoured out the rifts, while deep fans of sediment at the bottoms of others seem to point to their formation by rapid turbidity currents, violent undersea avalanches of sediment triggered in some instances by earthquakes. |  |
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The walls of these canyons are rocky and filled with crevices that are perfect homes for a wide variety of marine life, from deep-sea corals to fish, crabs and other animals. In addition, the nutrients that are washed down these canyons support this diverse collection of undersea creatures. Where there is an abundance of undersea life, there is generally a respectable diversity of marine life visible from the surface as well, and the birds and cetaceans attracted to the animals of these canyons were attracting there as well. |
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(Check out this
link to the American
Museum of Natural History's Milstein Hall of Ocean Life for some
good pictures and information about Undersea Canyon occupants. Be sure
to click on the pictures at the top of the page.)
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Our Destinations
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The continental slope off Georges Banks, some 100 miles from nearest landfall in Massachusetts, contains several notable submarine canyons. Those we were heading for were the series of canyons stretching from Lydonia Canyon to Hydrographer's Canyon, an area about 25 miles wide and 60 miles long just along the edge of the continental shelf. |
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Canyons visited by the 2003 CORE Whales and Seabirds Canyons Trip (Click on image for larger view) |
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The extent of the drop-off at the edge of the continental shelf is often difficult to appreciate from standard bathymetric maps. The image at right taken from a computer-generated "fly-by" of the Gulf of Maine shows the change in depth much more dramatically. This animation was created by scientists at Woods Hole Oceanographic Institute using bathymetric data taken of the Gulf of Maine. Click on the image to see the entire (very cool) animation. |
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