Farallon Plate In the Early Jurassic the Pacific Plate opened originating from a triple junction between the Panthalassic Farallon, Phoenix, and Izanagi plates. Pangaea Panthalassa (Wikipedia) Panthalassa, also known as the Panthalassic Ocean or Panthalassan Ocean (from Greek πᾶν “all” and θάλασσα “sea”), was the superocean that surrounded the supercontinent Pangaea, the latest in a series of supercontinents in the history of Earth. During the Paleozoic–Mesozoic transition c. 250 Ma it occupied almost 70% of Earth’s surface. Its ocean floor has completely disappeared because of the continuous subduction along the continental margins on its circumference. Panthalassa is also referred to as the Paleo-Pacific (“old Pacific”) or Proto-Pacific because the Pacific Ocean is a direct continuation of Panthalassa. Panthalassa was a hemisphere-sized ocean, much larger than the modern Pacific. The Juan de Fuca Plate system has its origins with Panthalassa’s oceanic basin and crust. The Pacific Ocean was born 750 million years ago at the breakup of Rodinia, although it is generally called the Panthalassa until the breakup of Pangea, about 200 million years ago.