Laurasia

Laurasia, a portmanteau for Laurentia and Eurasia, was the more northern of two large landmasses (the other being Gondwana) that formed part of the Pangaea supercontinent from around 335 to 175 million years ago (Mya). It separated from Gondwana 215 to 175 Mya (beginning in the late Triassic period) during the breakup of Pangaea, drifting farther north after the split and finally broke apart with the opening of the North Atlantic Ocean c. 56 Mya.

Laurentia, Avalonia, Baltica, and a series of smaller terranes, collided in the Caledonian orogeny 400 Ma ago to form Euramerica, then collided with Gondwana to form Pangaea. Kazakhstania and Siberia were then added to Pangaea 290–300 Ma to form Laurasia. Laurasia finally became an independent continental mass when Pangaea broke up into Gondwana and Laurasia.

Breakup
In the Triassic–Early Jurassic (c. 200 Mya), the opening of the Central Atlantic Ocean was preceded by the formation of a series of large rift basins, such as the Newark Basin, between eastern North America, from what is today the Gulf of Mexico to Nova Scotia, and in Africa and Europe, from Morocco to Greenland.

By c. 83 Mya spreading had begun in the North Atlantic between the Rockall Plateau, a continental fragment sitting on top of the Eurasian Plate, and North America. By 56 Mya Greenland had become an independent plate, separated from North America by the Labrador Sea-Baffin Bay Rift. By 33 Mya spreading had ceased in the Labrador Sea and relocated to the Mid-Atlantic Ridge. The opening of the North Atlantic Ocean had effectively broken Laurasia in two.