Jurassic Period
In geologic time, the Jurassic Period—the middle of three geologic periods in the Mesozoic Era—spans the time from roughly 206–208 million years ago (mya) to approximately 146 mya.
The Jurassic Period contains three geologic epochs. The earliest epoch, the Lias Epoch, ranges from the start of the Jurassic Period to approximately 180 mya. The Lias Epoch is further subdivided into (from earliest to most recent) Hettangian, Sinemurian, Pliensbachian, and Toarcian stages. The middle epoch, the Dogger Epoch, ranges from 180 mya to 159 mya and is further subdivided into (from earliest to most recent) Aalenian, Bajocian, Bathonian, and Callovian stages. The latest epoch (most recent), the Maim Epoch, ranges from 159 mya to 144 mya and is further subdivided into (from earliest to most recent) Oxfordian, Kimmeridgian, and Tithonian stages.
During the Jurassic Period, the Pangaean supercontinent broke into continents recognizable as the modern continents. At the start of Jurassic Period, Pangaea spanned Earth's equatorial regions and separated the Panthalassic Ocean and the Tethys Ocean. Driven by plate tectonics during the Jurassic Period, the North American and European continents diverged, and the earliest form of the Atlantic Ocean flooded the spreading sea floor basin between the emerging continents. By mid-Jurassic Period, although still united along a broad region, what would become the South American and African Plates and continents became distinguishable in a form similar to the modern continents.
By the end of the Jurassic Period, North America and South America became separated by a confluence of the Pacific Ocean and Atlantic Ocean. Extensive flooding submerged much of what are now the eastern and middle portions of the United States.
By the end of the Jurassic Period, water separated South America from Africa, and the Australian and Antarctic continents were clearly articulated. The Antarctic continent began a slow southward migration toward the south polar region.
The Jurassic Period (in popular culture widely recognized as the "Age of the Dinosaurs") was named for the Jura Mountains on the Swiss-French border, an area where the classic formations were first identified and studied.
Large meteor impacts occurred at the start and end of the Jurassic Period (and later intensified during the subsequent Cretaceous Period). During the Jurassic Period itself, there is evidence of only one major impact—the Puchezh impact in Russia. The Manicouagan impact in crust now near Quebec, Canada, dates to the late Triassic Period just before the start of the Jurassic Period. A trio of impacts in areas now located in South Africa, the Barents Sea, and Australia occurred near the end of the Jurassic Period and start of the Cretaceous Period.
Although humans and dinosaurs never co-existed—in fact they are separated by approximately 63 million yeas of evolutionary time—the Jurassic Period's wealth of fossils have long stirred human imagination about life on Earth during that time. The abundant life of the Jurassic Period also left a legacy of organic remains that today provide an economically important source of fossil fuels. Many prominent oil-fields date to the Jurassic Period (e.g., the North Sea fields).
Archean; Cambrian Period; Cenozoic Era; Dating Methods; Devonian Period; Eocene Epoch; Evolution, Evidence Of; Fossil Record; Fossils and Fossilization; Geologic Time; Historical Geology; Holocene Epoch; Marine Transgression and Marine Recession; Miocene Epoch; Mississippian Period; Oligocene Epoch; Ordovician Period; Paleocene Epoch; Paleozoic Era; Pennsylvanian Period; Phanerozoic Eon; Pleistocene Epoch; Pliocene Epoch; Precambrian; Proterozoic Era; Quaternary Period; Silurian Period; Supercontinents; Tertiary Period
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