|Geology of the Mesozoic Era
Paleogeography played an important role in the changes that occurred in Earth’s climate and biota during the Mesozoic Era.
At the beginning of the Mesozoic Era, all of the earth’s continents were welded together to form the supercontinent Pangaea. This hot and dry continent was inhabited by reptiles that had survived the Permian–Triassic extinction event. Near the end of the Triassic Period, Pangaea began to break apart. This resulted in the development of large fault-bound valleys, containing volcanoes (CAMP volcanics, i.e., Central Atlantic Magmatic Province), along what was to become the eastern edge of the North American continent.
The breakup of Pangaea continued during the Jurassic Period. A long, narrow seaway, similar to today’s Red Sea, formed along the eastern edge of North America, stretching into what is now the Gulf of Mexico.
During the Cretaceous Period the narrow seaway grew, rapidly forming the Atlantic Ocean. The rapid formation of the Atlantic Ocean’s crust is believed to have been responsible for the unusually high sea level during the Cretaceous. Near the end of the Cretaceous, the Indian subcontinent broke away from Africa, and the resulting Deccan volcanics are believed to have contributed to the Cretaceous–Paleogene (K-Pg) extinction.