Laurasia

Laurasia was a paleogeographic landmass in the northern hemisphere that formed after the breakup of the supercontinent Pangaea during the Early to Middle Jurassic and persisted until its components began to fragment in the Late Cretaceous. It is typically described as consisting of the major continental blocks Laurentia, Baltica, and Siberia, which together occupied much of what is now North America, northern Europe, and Siberia. Some reconstructions also include smaller blocks along the Arctic and eastern Asia.

Geographically, Laurasia bordered Panthalassa to the north and the southern margins were separated from Gondwana by the expanding Tethys Ocean. The margin interactions with adjacent plates and microcontinents played a key role in shaping ocean basins and mountain belts along its perimeter, such as the Caledonian and Variscan orogenies that affected its southern and western margins far earlier in the Paleozoic, and later rifting that would drive its breakup.

Tectonically, the breakup of Pangaea initiated rifting and sea-floor spreading that eventually separated the northern landmasses from one another. Over tens of millions of years, Laurasia fragmented into the components we recognize today as North America, Europe, and much of Asia. The processes that dissolved Laurasia contributed to the opening of the North Atlantic and to the evolving architecture of the Northern Hemisphere’s continents.

Legacy, in broad terms, is that many of the landmasses and crustal formations of present-day North America, Europe, and parts of Asia trace their origins to the assembly and subsequent breakup of Laurasia. The concept remains a useful framework in paleogeography for describing the northern portion of the former Pangaea.