One discovery is that Iceland itself is rifting at the rate of a few centimeters per year. The straddling of the ridge by Iceland and its many volcanoes makes for a natural scientific laboratory for the study of the geophysical processes that otherwise occurs mostly underwater. The northernmost portion of the ridge passes under and beyond Iceland, where it is actually at the floor of the Arctic Ocean rather than the Atlantic. Great volumes of water pour from the west side of the ridge thru Charlie-Gibbs to the east side, with weaker return flows occurring elsewhere along the mountain range. Situated straight west of Ireland and southeast of Greenland, the fracture zone cuts through the Mid-Atlantic Ridge and connects the two halves of the North Atlantic. To the north is a giant canyon hundreds of miles long and about 20 miles wide named the Charlie-Gibbs Fracture Zone. Near the Equator, the ridge bends sharply in an S-curve and is dissected into the North Atlantic Ridge and South Atlantic Ridge by the Romanche Trench, a narrow submarine ravine with a maximum depth of 7,758 m, one of the deepest points in the Atlantic Ocean. (Fast-spreading systems are more typical of the Pacific Ocean, where deep trenches are more common than in the Atlantic.) New seabed is continually being formed from the spreading ridge, which creates relatively shallow areas in the middle of the Atlantic above the extremely flat abyssal plains that begin at the margins of the continental shelves. The Mid-Atlantic Ridge is an example of what is called a slow-spreading mid-oceanic ridge system, which typically is broad with a deep, central rift valley. It actually sits on top of the "mid-Atlantic rise," a linear bulge running the length of the ocean with the ridge resting on the highest point of the bulge, which is thought to be caused by upward convective forces in the Earth's mantle. The ridge is now known to be an oceanic rift separating the North American Plate from the Eurasian Plate in the North Atlantic, and the South American Plate from the African Plate in the South Atlantic. The studies done of the areas below the surface of the seas greatly illuminated the scientific understanding of what was more clearly visible on dry land. Part of the Earth's mid-oceanic ridge system, which reaches throughout all the world's oceans, the Mid-Atlantic Ridge was discovered in the 1950s by American geologists whose work led in the next decade to the theories of seafloor spreading, continental drift, and plate tectonics. Evidence has been discovered that some of the largest whales that frequent the Atlantic migrate along the ridge. Its northern extent lies at approximately 87°N (about 330 km south of the North Pole) in the south it stretches to subantarctic Bouvet Island before turning east to become the Atlantic-Indian Ridge. If it were all above water, the ridge would be commonly regarded, at 16,000 km, as the world's longest near-continuous mountain span under one name. The Mid-Atlantic Ridge is a mountain range running mostly underwater and generally north-south through the middle of the Atlantic Ocean.
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