Permian–Triassic extinction event[edit]

The Permian–Triassic extinction event, labeled "End P" here, is the most significant extinction event in this plot for marine genera which produce large numbers of fossils.

The Permian ended with the most extensive extinction event recorded in paleontology: the Permian–Triassic extinction event. 90% to 95% of marine species became extinct, as well as 70% of all land organisms. It is also the only known mass extinction of insects.[8][27] Recovery from the Permian-Triassic extinction event was protracted; on land, ecosystems took 30 million years to recover.[9] Trilobites, which had thrived since Cambrian times, finally became extinct before the end of the Permian. Nautiluses, a species of cephalopods, surprisingly survived this occurrence.

There is evidence that magma, in the form of flood basalt, poured onto the surface in what is now called the Siberian Traps, for thousands of years, contributing to the environmental stress that led to mass extinction. The reduced coastal habitat and highly increased aridity probably also contributed. Based on the amount of lava estimated to have been produced during this period, the worst-case scenario is the release of enough carbon dioxide from the eruptions to raise world temperatures five degrees Celsius.[14]

Another hypothesis involves ocean venting of hydrogen sulfide gas. Portions of the deep ocean will periodically lose all of its dissolved oxygen allowing bacteria that live without oxygen to flourish and produce hydrogen sulfide gas. If enough hydrogen sulfide accumulates in an anoxic zone, the gas can rise into the atmosphere. Oxidizing gases in the atmosphere would destroy the toxic gas, but the hydrogen sulfide would soon consume all of the atmospheric gas available. Hydrogen sulfide levels might have increased dramatically over a few hundred years. Models of such an event indicate that the gas would destroy ozone in the upper atmosphere allowing ultraviolet radiation to kill off species that had survived the toxic gas.[28] there are species that can metabolize hydrogen sulfide.

Another hypothesis builds on the flood basalt eruption theory. An increase in temperature of five degrees Celsius would not be enough to explain the death of 95% of life. But such warming could slowly raise ocean temperatures until frozen methane reservoirs below the ocean floor near coastlines melted, expelling enough methane (among the most potent greenhouse gases) into the atmosphere to raise world temperatures an additional five degrees Celsius. The frozen methane hypothesis helps explain the increase in carbon-12 levels found midway in the Permian–Triassic boundary layer. It also helps explain why the first phase of the layer's extinctions was land-based, the second was marine-based (and starting right after the increase in C-12 levels), and the third land-based again.[29]

An even more speculative hypothesis is that intense radiation from a nearby supernova was responsible for the extinctions.[30]

It has been hypothesised that huge meteorite impact crater (Wilkes Land crater) with a diameter of around 500 kilometers in Antarctica represents an impact event that may be related to the extinction.[31] The crater is located at a depth of 1.6 kilometers beneath the ice of Wilkes Land in eastern Antarctica. The scientists speculate that this impact may have caused the Permian–Triassic extinction event, although its age is bracketed only between 100 million and 500 million years ago. They also speculate that it may have contributed in some way to the separation of Australia from the Antarctic landmass, which were both part of a supercontinent called Gondwana. Levels of iridium and quartz fracturing in the Permian-Triassic layer do not approach those of the Cretaceous–Paleogene boundary layer. Given that a far greater proportion of species and individual organisms became extinct during the former, doubt is cast on the significance of a meteorite impact in creating the latter. Further doubt has been cast on this theory based on fossils in Greenland that show the extinction to have been gradual, lasting about eighty thousand years, with three distinct phases.[32]

Many scientists argue that the Permian–Triassic extinction event was caused by a combination of some or all of the hypotheses above and other factors; the formation of Pangaea decreased the number of coastal habitats and may have contributed to the extinction of many clades.[citation needed]

See also[edit]


  1. Jump up ^ Image:Sauerstoffgehalt-1000mj.svg
  2. Jump up ^ File:OxygenLevel-1000ma.svg
  3. Jump up ^ Image:Phanerozoic Carbon Dioxide.png
  4. Jump up ^ Image:All palaeotemps.png
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  10. Jump up ^ Benton, M.J. et al., Murchison’s first sighting of the Permian, at Vyazniki in 1841, Proceedings of the Geologists' Association, accessed 2012-02-21
  11. Jump up ^ Murchison, Roderick Impey (1841) "First sketch of some of the principal results of a second geological survey of Russia," Philosophical Magazine and Journal of Science, series 3, 19 : 417-422. From p. 419: "The carboniferous system is surmounted, to the east of the Volga, by a vast series of marls, schists, limestones, sandstones and conglomerates, to which I propose to give the name of "Permian System," … ."
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  13. Jump up ^ "Kazanian" GeoWhen Database, International Commission on Stratigraphy (ICS)
  14. ^ Jump up to: a b c Palaeos: Life Through Deep Time > The Permian Period Accessed 1 April 2013.
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  17. Jump up ^ Zimmerman EC (1948) Insects of Hawaii, Vol. II. Univ. Hawaii Press
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  22. Jump up ^ Riek EF Kukalova-Peck J (1984) A new interpretation of dragonfly wing venation based on early Upper Carboniferous fossils from Argentina (Insecta: Odonatoida and basic character states in Pterygote wings.) Can. J. Zool. 62; 1150-1160
  23. ^ Jump up to: a b Huttenlocker, A. K., and E. Rega. 2012. The Paleobiology and Bone Microstructure of Pelycosaurian-grade Synapsids. Pp. 90–119 in A. Chinsamy (ed.) Forerunners of Mammals: Radiation, Histology, Biology. Indiana University Press.
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  25. Jump up ^ Huttenlocker A. K. (2009). "An investigation into the cladistic relationships and monophyly of therocephalian therapsids (Amniota: Synapsida)". Zoological Journal of the Linnean Society. 157: 865–891. doi:10.1111/j.1096-3642.2009.00538.x. 
  26. Jump up ^ Huttenlocker A. K.; Sidor C. A.; Smith R. M. H. (2011). "A new specimen of Promoschorhynchus (Therapsida: Therocephalia: Akidnognathidae) from the lowermost Triassic of South Africa and its implications for therocephalian survival across the Permo-Triassic boundary". Journal of Vertebrate Paleontology. 31: 405–421. doi:10.1080/02724634.2011.546720. 
  27. Jump up ^ Andrew Alden. "The Great Permian-Triassic Extinction". Education. 
  28. Jump up ^ Kump, L.R., A. Pavlov, and M.A. Arthur (2005). "Massive release of hydrogen sulfide to the surface ocean and atmosphere during intervals of oceanic anoxia". Geology. 33 (May): 397–400. Bibcode:2005Geo....33..397K. doi:10.1130/G21295.1. 
  29. Jump up ^ Benton, Michael J.; Twitchett, Richard J. (7 July 2003). "How to kill (almost) all life: the end-Permian extinction event". Trends in Ecology and Evolution. 18 (7): 358–365. doi:10.1016/S0169-5347(03)00093-4. 
  30. Jump up ^ Ellis, J (January 1995). "Could a nearby supernova explosion have caused a mass extinction?". Proceedings of National Academy of Sciences. 92: 235–8. doi:10.1073/pnas.92.1.235. PMC 42852Freely accessible. PMID 11607506. 
  31. Jump up ^ Gorder, Pam Frost (June 1, 2006). "Big Bang in Antarctica – Killer Crater Found Under Ice". Ohio State University Research News. Archived from the original on March 6, 2016. 
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Further reading[edit]

External links[edit]