Panthalassa (
Greek "all" and "ocean"), also known as the
Panthalassic Ocean, was the vast global ancestral Pacific
ocean that surrounded the
supercontinent Pangaea, during the late
Paleozoic and the early
Mesozoic eras. It included the
Pacific Ocean to the west and north and the
Tethys Ocean to the southeast. It became the Pacific Ocean, following the closing of the Tethys basin and the breakup of Pangaea, which created the
Atlantic,
Arctic, and
Indian Ocean basins. The Panthalassic is often called the
Paleo-Pacific ("old Pacific") because the Pacific Ocean developed from it in the
Mesozoic to the present.
