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Panthalassa, also known as the Panthalassic or Panthalassan Ocean, (from Greek Ïá¾¶Î½ all and Î¸Î¬Î»Î±ÏÏÎ± sea), was the superocean that surrounded the supercontinent Pangaea. During the PaleozoicâMesozoic transition c. 250 Ma it occupied almost 70% of Earth's surface.
The underwater outskirts of the continents surrounding the basin of the Atlantic Ocean are characterized by gently inclined plains of continental embankments and steep continental slopes. The latter are cut by underwater canyons, which are situated, for the most part, along extensions of river valleys of the land mass.