Reshaping Of The Continents And Oceans

The Earth underwent dramatic geologic changes during the 180 million-year span of the Mesozoic Era. During most of the Trias-sic Period, the continents that are known today were still joined together as the supercontinent Pangaea. Pangaea was an expansive landmass that filled most of the Earth's Western Hemisphere. Because of Pangaea's size, distinct interior climate zones and new habitats for plants and animals developed. The formation of Pangaea also marked a low ebb in ocean depths; this was one of the factors that contributed to the changes in ocean habitats that led to the end-Permian extinction of many marine invertebrate species.

By the Early Jurassic, Pangaea began to split apart, first dividing into two landmasses. The northern landmass, which geologists call Laurasia, included areas that later became North America, Europe, and Asia. The southern landmass, known as Gondwana, included the regions now known as South America, Africa, India, Australia, and Antarctica. Further division into the present configuration of the world's continents was well under way by the end of the Mesozoic Era.

If the formation of Pangaea could be called the signature geologic event of the Paleozoic, then the gradual breakup of the supercontinent could be called the most influential geologic occurrence of the Mesozoic. Massive shifts in tectonic plates were not without their consequences for many of the world's habitats. While Pangaea was intact, it was surrounded by the Panthalassic Ocean, the southeastern portion of which was called the Tethys Ocean. The Atlantic Ocean began to appear in the middle of Pangaea as tectonic plates separated and continental landmasses radiated outward from the equator to the north and south. The collision of tectonic plates began the formation of North America. Continental areas today associated with North and South America, Europe, central Asia, and northern Africa were the site of extensive inland seas. By the Cretaceous Period, North America had a shallow inland sea stretching down its middle from what is now Alaska to the Gulf of Mexico.

225 million years ago

6 Infobase Publishing

225 million years ago

6 Infobase Publishing

Pangaea during the Triassic Period

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