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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.
During the Jurassic period the continent Pangaea split into two major continents: Laurasia and Gondwana. This division opened up what would eventually become the Gulf of Mexico and the Atlantic Ocean. Underwater volcanic activity caused ocean floor to spread and thereby bringing about the rise of water levels.