Geology of the Pacific Ocean . The Pacific Ocean developed from the Panthalassa, a vast global ocean, following the breakup of the supercontinent Pangaea in the Mesozoic Era, gradually forming Gondwana and Laurasia, which in turn divided. There is no firm date for when the changeover occurred, as the replacement of the sea bed is a continuous process, though reconstruction maps often change the name from Panthalassic to Pacific around the time the Atlantic Ocean began to open. The Panthalassic Ocean first opened around 750 million years ago at the breakup of Rodinia, but the oldest Pacific Ocean floor is only around 180 Ma old.
Supercontinent Neoarchean age broke off at ~2480 and and portions of them later collided to form Nuna (Northern Europe North America) (). Nuna continued to develop during the Mesoproterozoic, primarily by lateral accretion of juvenile arcs, and in Nuna collided with other land masses, forming Rodinia. Between ~825 and Rodinia broke apart. However, before completely breaking up, some fragments of Rodinia had already come together to form Gondwana (also known as Gondwanaland) by . Pangaea formed by through the collision of Gondwana, Laurasia (Laurentia and Baltica), and Siberia. The second model (Kenorland-Arctica) is based on both palaeomagnetic and geological evidence and