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the Mid-Atlantic Ridge (Original)

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Carolyn Silver
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« Reply #75 on: July 28, 2008, 11:46:37 pm »


Figure 11. Former land areas in the present Pacific and Indian Oceans. Only those areas for which substantial evidence already exists are shown. Their exact outlines and full extent are as yet unknown. G1 -- Seychelles area; G2 -- Great Oyashio Paleoland; G3 -- Obruchev Rise; G4 -- Lemuria; S1 -- area of Ontong-Java Plateau, Magellan Sea Mounts, and Mid-Pacific Mountains; S2 -- Northeast Pacific; S3 -- Southeast Pacific including Chatham Rise and Campbell Plateau; S4 -- Southwest Pacific; S5 -- area including South Tasman Rise; S6 -- East Tasman Rise and Lord Howe Rise; S7 -- Northeast Indian Ocean; S8 -- Northwest Indian Ocean. (Reprinted with permission from Dickins [13]. Copyright by J.M. Dickins.)

    In the North Atlantic and Arctic Oceans, modified continental crust (mostly 10-20 km thick) underlies not only ridges and plateaus but most of the ocean floor; only in deep-water depressions is typical oceanic crust found. Since deep-sea drilling has shown that large areas of the North Atlantic were previously covered with shallow seas, it is possible that much of the North Atlantic was continental crust before its rapid subsidence. Lower Paleozoic continental rocks with trilobite fossils have been dredged from seamounts scattered over a large area northeast of the Azores, and the presence of continental cobbles suggests that the area concerned was a submerged continental zone. Bald Mountain, from which a variety of ancient continental material has been dredged, could certainly be a foundered continental fragment. In the equatorial Atlantic, continental and shallow-water rocks are ubiquitous.
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