Laurentia (continent)
Laurentia is a geologically old continental block that covers much of what is now North America, including Greenland.
The earth's oldest rock formations have been found in the land mass of Laurentia : the Acasta gneiss from the Western Canadian Shield dates from the Hadaic era of 4,030 mya and the Nuvvuagittuq greenstone belt from the Eastern Canadian Shield, possibly up to 4.3 billion years old .
Laurentia was about 1,910 mya from that part of the fragments Kenorlands that the Wopmay - orogeny in the slave Province of Northwest Territories caused, and was from about 1,100 mya part of the supercontinent Rodinia .
About 800 mya, Laurentia split off from Rodinia. With the rest of Proto- Laurasia , of which Laurentia was now part, it slowly moved north during the Ediacarium , and presumably reunited briefly with the rest of the earth to form Pannotia . Now it can also be called part of Laurasia.
During the Cambrian and Ordovician periods , i.e. 542 mya to 444 mya, the continental floe was near the equator, with Avalonia and Baltica in the Iapetus Ocean to the south .
Around 440 mya, in the early Silurian , the Iapetus Ocean began to expand east of Laurentia. Its plate subducted under the east coast, raised the continental crust and caused a period of volcanism . The Appalachians arose on Laurentia, while at the same time on the other side of the sea, on the already united Baltica / Avalonia, the Caledonian mountains grew. Sedimentary rocks of the Iapetus Ocean can be detected in both mountain ranges today. In the early Devonian , around 400 mya, the Iapetus Ocean then joined to form a bay of the Rheic Ocean and thus welded the three continental plates to form the new major continent Laurussia or Euramerica . The Appalachian and Caledonian Mountains were raised further.
Around 300 mya, Laurussia formed the last supercontinent, Pangea, with Sibiria and Gondwana .
Web links, sources
English:
German: