Fun with Science Club®


			The Ocean Floor Naval Meterological and Oceanography Command 03.23.01 Imagine flying cross-country. Below, the terrain is dotted with plains, mountains, and deep canyons. Now, picture the area seven miles below the surface of the sea. What does it look like? Surprisingly, very similar to the topography of the continental United States. The sea bottom is divided into three areas: the continental shelf, the continental slope, and the ocean floor. The continental shelf has numerous hills, ridges, terraces, and canyons. Its average width is 30 miles, but it can extend several miles from shore. The continental slope, between the shelf and the deep ocean, slopes an average of two to three degrees, except off volcanic islands where the slope is about 50 degrees. All oceans except the North Pacific are divided by mountain systems - several of which are higher than Mt. Everest. The largest mountain chain is the Mid-Atlantic Ridge. Much of the deep ocean floor, especially in the Pacific, is covered with basins, and somewhat resembles the surface of the moon. Another prominent feature of the deep ocean floor is the deep ocean trenches which are found in areas of volcanic activity. Narrow, often arc-shaped, these depressions are 50-60 miles wide, as much as 1,000 feet long, and up to 36,000 feet deep. The largest, the Tonga-Kermadec Trench in the Western Pacific, is spacious enough to contain six Grand Canyons. Movement in the trenches can displace the ocean surface leading to the formation of dreaded tsunami waves, often erroneously called tidal waves. Manned exploration of the trenches began on January 23, 1960, when two men in the bathyscaphe Trieste descended to the deepest known spot in the ocean, the Challenger Deep, located seven miles below the surface in the Marianas Trench. Today, exploration of the deep continues with more sophisticated deep submergence vehicles (DSVs). DSVs are invaluable aids in salvage and rescue missions as well as in scientific exploration and research.


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