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Phanerozoic/Permian period

The last period in the Paleozoic Era ranged from 290 million years ago to 240 million years ago. It saw the continued diversification of land vertebrates starting with the macro ancestral group ammniotes. The end of Permian Period and the beginning of the Mesozoic Era is marked by the largest mass extinction recorded in Earth's history. Tectonic activity joined all of the land masses together forming the super-continent named Pangea. The mass supercontinent was surrounded by the ocean Panthalassa. The Tethys Sea covered much of the southern and central section of what is now called Europe.

  • Worlds masses joined together on Pangea which was surrounded my the large single ocean the Panthalassa [1]

Climate

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Entering into the early Permian Period, the planet was experiencing an ice age. The north and south poles were covered in thick layers of ice. Gondwanaland was glaciated, and at the same point in time, tropical zones contained swampy forests. The continents move together and northward forming Pangea, which caused cooling on the land mass.[2] By the middle of the Permian Period, climate began to warm and become more humid but remained humid. Polar Tundra Regions began to dry up as Pangea's inner continent became more humid and dry. The late Permian saw sequences of warm and cool climate changes, which may be linked to the mass extinction that occurred at the end of the Permian Period and marked the beginning of the Mesozoic Era.[3]

The transition into the Middle Permian period saw a transition from an ice ago to a humid and dry climate, especially near the middle of Pangea’s equator. Lycopods and Sphenopsids greatly reduced in size, due to the lack of moisture on the midland. Mighty swamp forests were reduced to shrubberies. [4]

Life on Pangea

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Marine Life

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Life flourished within the warm shallow oceans. Here, and abundance of invertebrates lived including, sponges, rugose coral, stromatolites, algae, foraminifers, corals, bryozoa, brachiopods.

As predators increased in size and deadliness, prey began to develop methods of protection for survival. This led to diversification in marine life throughout the Permian Period.

Plant Life

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The northern section of of Pangea was dry and humid. Plants required very little water and could withstand intense fluctuations of dry and hot seasons. These plants included Conifers, Seed ferns, Ginkos, and other drought-resistant plants. As the climate became more dry, and abundance of gymnosperms fossils have been traced[5]. Seeds were able to maintain it's inner moisture to prevent dryness.

Land Animals

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  • Filled by eureptilia, especially archosaurs[6]
  • Dry climate favors reptillia
  • Pelycosaurs evolved, and had a sail on its back, which may have been used to stabilize body temperature
 
Dimetrodon, a dominant predator near the paleo-equator for about 20 million years
 
Archegosaurus, a genus of amphibian which lived during the Asselian to Wuchiapingian ages of the Permian, around 299-253 million years ago(4)
 
Palaeohatteria

Mass Extinction

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There are several theories as to what actually caused mass extinctions, diminishing or killing off most species. The end of the Permian period marked the greatest mass extinction ever recorded in Earth's history that left 90-95% of marine species and about 70% of land animals went extinct.[7]

Transgression

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A possible cause to the largest extinction in Earth's history is a global cooling and/or worldwide lowering of sea level.[8] These sea fluctuations Researchers have found evidence of Super volcano eruptions at shallow sea levels, where much of life existed during the Permian Period. The result may have been a formation of a cloud that spread the planet in ash and dust, effectively blocking out the sun, lowering the temperature globally, and produce acid rain.[9]

Impact

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An asteroid or comet collision with Earth could have killed off 90% of life at the end of the Permian Period. The collision would have been an direct cause of extinction. Rather, massive volcanism, global changes to sea-level and climate would have been the direct causes.[10]

It is considered that the K-T extinction that killed off about 60% of organisms on Earth, and most of the Dinosaurs, was the result of an impact event 65 million years ago. Since 70% of the Earth’s surface is covered in water, an impact would have more a 2 to 1 chance of striking the ocean, leaving no crater as evidence for us today. If an impact did occur in the ocean, the object would have been moved on the conveyer-belt-like divergent tectonic boundary on the ocean floor, and eventually ended up in a subduction zone or trench. There is evidence of shocked quartz at this time that has been found in Australia and Antarctica, as well as meteorite fragments in Antarctica [11]

Volcanism

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Some evidence suggests that an ancient super volcano in the Siberian Traps could have been responsible for the Permian-Triassic extinction event. By analyzing magnetically sensitive minerals in lava flow shows sign of the periodic reversal of Earth’s magnetic polarity. These stripes index the time of the eruption of the volcano in Siberia as well as similar magnetic pattern in the Deccan Traps that erupted near the time of the extinction of Dinosaurs. [12]. These super-volcanoes could cause "a volcanic eruption ten thousand times larger than man has ever seen”.[13] The end of the Permian period was marked by a basalt flow that created the Siberian Traps. It is considered to be one of the largest basalt flows in history, covering over 2 million square miles of Earth in lava [14]. These eruptions may have caused dust clouds that would have covered the sky, blocking out the sun which causes a few problems. First, the photosynthesis process shuts down, causing plants to stop producing oxygen as waste. The anoxic environment would devastate most life on earth, on the land and sea. Second, carbon dioxide levels would climb to unsafe levels poisoning the air organisms breathe. In addition, raised carbon dioxide levels would increase the global temperature, only before it lowers again after being blocked out from the sun’s exposure for a long period of time, resulting in a global cooling phase. Third, the eruptions may have cause acid rain from the excess dust in the atmosphere, killing off plant organisms very quickly [15].

References

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  1. ↑ http://www.palaeos.com/Paleozoic/Permian/Permian.htm
  2. ↑ author, date, title
  3. ↑ http://www.palaeos.com/Paleozoic/Permian/Permian.htm
  4. ↑ http://www.palaeos.com/Paleozoic/Permian/Permian.htm (May 20, 2010)
  5. ↑ http://www.ucmp.berkeley.edu/permian/permian.html (May 20, 2010)
  6. ↑ http://www.palaeos.com/Vertebrates/Units/270Archosauromorpha/270.500.html (May 20, 2010)
  7. ↑ Benton M. J., (2005), “When Life Nearly Died: The Greatest Mass Extinction of All Time. Thames & Hudson.
  8. ↑ Newell ND (1971). "An Outline History of Tropical Organic Reefs" (PDF). American Museum novitates 2465: 1–37. Retrieved 2007-11-03
  9. ↑ Park, http://park.org/Canada/Museum/extinction/permass.html (May 21, 2010)
  10. ↑ Stricherz, V., Feb 22, 2001: "Asteroid or comet triggered death of most species 250 million years ago": http://www.washington.edu/newsroom/news/2001archive/02-01archive/k022201.html (May 20, 2010)
  11. ↑ Basu AR, Petaev MI, Poreda RJ, Jacobsen SB, Becker L (2003). "Chondritic meteorite fragments associated with the Permian–Triassic boundary in Antarctica". Science 302 (5649): 1388–1392.
  12. ↑ Choi, C. Q., LiveScience Contributor, Ancient Super-volcano Created Giant Underwater Mountain Chain: <http://www.livescience.com/environment/Supervolcano-Underwater-Mountain-Chain-100409.html>, (May 9 2010))
  13. ↑ Professor Vincent Courtillon, University of Paris, BBC, 5 December, 2002, The Day the Earth Nearly Died: <http://www.bbc.co.uk/science/horizon/2002/dayearthdied.shtml>, (May 9, 2010)
  14. ↑ Andy Saunders and Marc Reichow (January 2009), "The Siberian Traps and the End-Permian mass extinction: a critical review",: <http://www.le.ac.uk/gl/ads/SiberianTraps/PDF%20Files/The%20Siberian%20Traps%20and%20the%20End-Permian%20mass.pdf> Chinese Science Bulletin (Springer) 54 (1): 20-37, (May 10, 2010)
  15. ↑ White RV (2002). "Earth’s biggest 'whodunnit': unravelling the clues in the case of the end-Permian mass extinction": <http://www.le.ac.uk/gl/ads/SiberianTraps/Documents/White2002-P-Tr-whodunit.pdf> Phil. Trans. Royal Society of London 360: 2963–2985. (May 10, 2010)

http://www.palaeos.com/Vertebrates/Units/270Archosauromorpha/270.500.html
http://www.palaeos.com/Paleozoic/Permian/Permian.htm
http://www.ucmp.berkeley.edu/permian/permian.html
http://en.wikipedia.org/wiki/Archegosaurus
http://park.org/Canada/Museum/extinction/permass.html
http://blogs.discovermagazine.com/80beats/2009/05/29/in-the-permian-period-erupting-super-volcanoes-may-have-killed-half-the-planet/
http://www.britannica.com/EBchecked/topic/452280/Permian-Period#

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