Permian Period (World of Earth Science)
In geologic time, the Permian Period, the last period of the Paleozoic Era, covers the time roughly 286 million years ago (mya) until 245 mya.
The Permian Period spans two epochs. The Early Permian Epoch is the most ancient, followed by the Late Permian Epoch.
The Early Permian Epoch is divided chronologically (from the most ancient to the most recent) into the Asselian, Sakmarian, and Artinskian stages. The Late Permian Epoch is divided chronologically (from the most ancient to the most recent) into the Kungurian, Kazanian, and Tatarian stages.
In terms of paleogeography (the study of the evolution of the continents from supercontinents and the establishment of geologic features), the Permian Period was dominated by the movements of the supercontinent Pangaea, that during the Permian Period was located along the equator. Plate tectonic activity along the western border of Pangaea formed an extensive subduction zone that survives today as a large number of volcanoes located around the Pacific rim (i.e., the Pacific "Ring of Fire").
Differentiated by fossil remains and continental movements, the Carboniferous Period (360 mya to 286 mya) preceded the Permian Period. In many modern geological texts, especially those in the United States, the time of Carboniferous Period is covered by two alternate geologic periods, the Mississippian Period (360 mya to 325 mya) and the Pennsylvanian Period (325 mya to 286 mya). The Permian Period is followed in geologic time by start of the Triassic Period of the Mesozoic Era. The largest mass extinction in Earth's history catastrophic extinction of marine lifemarks the close of both the Permian Period and the Paleozoic Era. Accordingly, many fossils dated to the Permian Period are not found in Mesozoic Era formations.
The fossil record indicates that more than 95% of all Permian species became extinct at the close of the Permian Period. Alternative hypotheses integrate differently the effects of loss of marine habitat due to the continued fusion of continents into Pangaea.
There were a number of major impacts from large meteorites during the Permian Period. Although no crater has been specifically identified with the impact possibly associated with the mass extinction of species, indirect evidence in the form of catastrophically fused quartz crystals (shocked quartz) in area of Antarctica indicates that the crater measured approximately 300 mi (450 km) in diameter. Other but smaller impact craters dating to the Permian Period have been identified in modern Florida, Quebec, and Brazil.
Because of the fusion and confluence of continental land masses in Pangaea, locations as diverse as Texas (Glass Mountains), Nova Scotia (Brule Trackways), and Germany share a similar fossil record dating to the Permian Period.
See also Archean; Cambrian Period; Cenozoic Era; Cretaceous Period; Dating methods; Devonian Period; Eocene Epoch; Evolution, evidence of; Fossils and fossilization; Historical geology; Holocene Epoch; Jurassic Period; Miocene Epoch; Oligocene Epoch; Ordovician Period; Paleocene Epoch; Phanerozoic Era; Pleistocene Epoch; Pliocene Epoch; Precambrian; Proterozoic Era; Quaternary Period; Silurian Period; Tertiary Period