NORTH ATLANTIC OCEAN BASIN
CROSS-SECTION OF THE NORTH ATLANTIC OCEAN BASIN FROM THE U.S. TO EUROPE
The diagram above is a drawing of the bottom profile of the North Atlantic Ocean Basin from the U.S. coast to Europe showing the major features of the ocean floor. The sea floor can be subdivided into three major features: (1) continental margin, (2) abyssal plain, and (3) Mid-Atlantic Ridge. The continental margin is itself comprised of the shelf, slope and rise. The margin is the portion adjacent to the continent and the transition to the deep ocean basin. The Atlantic Continental Margin is an example of a “passive” margin, with a well developed, wide, gently-sloping shelf. The deepest part of the ocean depicted above is the abyssal plain. This is a flat, almost featureless, part of the sea floor that has become mantled with a sediment cover so that the bottom irregularities have been almost covered. Only the largest features project slightly above the flat floor; these form the abyssal hills. The third major feature of the Atlantic Ocean Basin is the Mid-Atlantic Ridge. By any comparison with mountain ranges on land, the Mid-Atlantic Ridge would be the longest and highest mountain range on Earth. In fact, by other names the oceanic ridges form a continuous “seam” throughout all the ocean basins, much like the stitchings on a baseball. The ridge occupies about one third of the area of the entire Atlantic Ocean. At the crest of the ridge is the rift valley or axial rift zone. This is a relatively narrow (about 1 mile wide) cleft in the ridge where the tectonic plates are pulling apart and where new oceanic crust is formed from molten rock. Note the absence of any trenches in this part of the ocean. Very few trenches occur in the Atlantic, and these are associated with the island arcs in the Caribbean and Scotia Seas. No trenches are present in the “open” Atlantic Ocean.