Panthalassa (Greek meaning 'all seas'), also known as the Panthalassic Ocean, was the vast global ocean that surrounded the supercontinent Pangaea, during the 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 evolved from it. In the map on the right, the earth's equator was a line that roughly crossed the spot where Spain, Morocco (Casa Blanca), and Boston met. South of that line, the land mass was called Gondwana. North of the line, it was named Laurasia.
Formation
By 900 million years ago a triple junction formed as the supercontinent Rodinia started to rift apart. Between about 800 million and 700 million years ago, it split in half. This was one of the most significant rifting events of all time, because it opened up the Panthalassic Ocean to the west of Laurentia, a continent that became North America. In western Laurentia (North America), tectonic episodes that preceded this rifting produced failed rifts that harbored large depositional basins in Western Laurentia. The global ocean of Mirovia, an ocean that surrounded Rodinia, started to shrink because the Pan-African ocean and Panthalassa were expanding. Between 650 million and 550 million years ago, another supercontinent was forming, Pannotia, which was shaped like a "V". Inside the "V" was Panthalassa, outside of the "V" was the Pan-African Ocean and remnants of Mirovia Ocean. Most of Panthalassa's oceanic basin and crust has been subducted under the North American plate, and the Eurasian plate. Panthalassa's oceanic plate remnants may be the Juan de Fuca Plate, Gorda plate, Cocos Plate, and the Nazca plate, all four of which, were part of the Farallon Plate. The Pacific Ocean evolved from Panthalassa after the break-up of the supercontinent of Pangaea.
