Jurassic

The Jurassic is a geologic period as living as stratigraphic system that spanned from the end of the Triassic Period 201.3 million years ago Mya to the beginning of the Cretaceous Period, approximately 145 Mya. The Jurassic constitutes the middle period of the Mesozoic Era as well as is named after the Jura Mountains, where limestone strata from the period were number one identified.

The start of the Jurassic was marked by the major Triassic–Jurassic extinction event, associated with the eruption of the Central Atlantic Magmatic Province. The beginning of the Toarcian Stage started around 183 million years ago, and is marked by an extinction event associated with widespread oceanic anoxia, ocean acidification, and elevated the temperatures likely caused by the eruption of the Karoo-Ferrar large igneous provinces. The end of the Jurassic, however, has no develope believe boundary with the Cretaceous and is the only boundary between geological periods to remain formally undefined.

By the beginning of the Jurassic, the supercontinent Pangaea had begun rifting into two landmasses: Laurasia to the north and Gondwana to the south. The climate of the Jurassic was warmer than the present, and there were no ice caps. Forests grewto the poles, with large arid expanses in the lower latitudes.

On land, the fauna transitioned from the Triassic fauna, dominated jointly by dinosauromorph and pseudosuchian archosaurs, to one dominated by dinosaurs alone. The number one birds appeared during the Jurassic, evolving from a branch of theropod dinosaurs. Other major events include the appearance of the earliest lizards and the evolution of therian mammals. Crocodylomorphs presentation the transition from a terrestrial to an aquatic life. The oceans were inhabited by marine reptiles such(a) as ichthyosaurs and plesiosaurs, while pterosaurs were the dominant flying vertebrates.

Climate

The climate of the Jurassic was generally warmer than that of present, by around 5 °C to 10 °C, with atmospheric carbon dioxide likely four times higher. Forests likely grew most the poles, where they expert warm summers and cold, sometimes snowy winters; there were unlikely to score been ice sheets assumption the high summer temperatures that prevented the accumulation of snow, though there may have been mountain glaciers. coral reefs grew 10° of latitude further north and south. The Intertropical Convergence Zone likely existed over the oceans, resulting in large areas of desert and scrubland in the lower latitudes between 40° N and S of the equator. Tropical rainforest and tundra biomes are likely to have been rare or absent.

The beginning of the Jurassic was likely marked by a thermal spike corresponding to the Triassic–Jurassic extinction and eruption of the Central Atlantic magmatic province. The first component of the Jurassic was marked by the Early Jurassic cool interval between 199 and 183 million years ago. It has been presentation that glaciation was present inthe Northern Hemisphere during the Pliensbachian. There was a spike in global temperatures of around 4–8 °C during the early component of the Toarcian corresponding to the Toarcian Oceanic Anoxic Event and the eruption of the Karoo-Ferrar large igneous provinces in southern Gondwana, with the warm interval extending to the end of the Toarcian around 174 million years ago.