Extinction event

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An '''extinction event''' (EE), also referred to as a '''mass extinction''', is an event where the majority of [[species]] (mostly [[animal]]s) on the [[planet]] become extinct. This is opposed to normal [[extinction]]s of just single species, which happen all the time in the wild, at a background extinction rate. Things that cause extinction-level events include supervolcanoes and mass [[climate change]], which are events suspected to have happened in the past on several occasions. The most spectacular and popular, of course, are [[asteroid]] impacts, which were popularized in the late 1990s by the movies ''Deep Impact'' and ''Armageddon''.

==Previous extinction events==
The most famous, undoubtedly because it is among the most ''spectacular'', extinction would be the asteroid impact that killed off the non-[[avian]] [[dinosaurs]] (the [[K-Pg extinction event]]); 65 million years ago (MYA). 50% of [[plants]] and [[animals]] (marine [[reptile]]s, ammonites, [[pterosaur]]s) died out. Many of them being animals that coexisted with dinosaurs, including [[mammals]], [[birds]], [[fish]], and [[insect]]s.

However, this pales in magnitude compared to the {{wpl|P-T extinction}} event, which ended the Permian period 252 MYA. Also known as the Permian mass extinction or the "Great Dying", it resulted in the worldwide loss of 57% of all families, 83% of all genera, 96% of all marine species, and an estimated 70% of all land species. Its cause is unclear but may have involved gradual climate change made suddenly much worse by meteor impact or volcanoes.<ref>[http://science.nasa.gov/science-news/science-at-nasa/2002/28jan_extinction/ "The Great Dying"], NASA, 2002</ref>

Similar explanations are suggested for the {{wpl|Triassic–Jurassic extinction event}} around 201 MYA. Dinosaurs actually became dominant after this mass extinction, gaining a wider variety of niches after  reptile competitors died off.

The {{wpl|Late Devonian extinction}} 360-375 MYA only affected aquatic life; again its causes are unclear but oxygen levels in water seem to have dropped dramatically. Terrestrial life was mostly safe and unaffected, ranging from insects to myriapods to amphibians.

Finally, the extinction which is understood most clearly is happening now, the [[Holocene extinction]]. The cause: people killing animals and other living things&nbsp;— as well as habitat loss, climate change, and poaching/overhunting. The biggest group of animals being affected are megafauna (large animals such as mammals, birds, reptiles, amphibians, and fish), and endemic species.

==Plausible causes==
It's generally hard to figure out the causes of a mass extinction, as they can vary depending on the period or era. Explanations vary but the following mechanisms have been advanced for past extinction events:
*Impacts from meteorites, [[comets]], asteroids: typically causing tsunamis and blotting out the [[Sun]]'s rays with dust.
*Massive volcanoes, causing either [[global warming]] or [[Ice age|global cooling]].
*Gradual climate change, which may have been caused by small continents mushing up into big continents (from [[Plate tectonics]]) and changing winds and ocean currents, or more complex mechanisms such as a runaway [[greenhouse effect]], {{wpl|Methane clathrate|methane clathrate offgassing|,}} etc.
*Changes in atmospheric [[oxygen]], most obviously due to the widespread proliferation of {{wpl|photosynthesis||:}} the {{wpl|Great Oxygenation Event}}
*Astronomical effects: [[dark matter]],<ref>[http://astronomynow.com/2015/02/19/does-dark-matter-cause-mass-extinctions-and-geologic-upheavals/ "Does dark matter cause mass extinctions and geologic upheavals?"], Astronomy Now, 2015</ref> supernovae,<ref>[https://www.newscientist.com/article/dn1764-supernova-smoking-gun-linked-to-mass-extinctions/ "Supernova 'smoking gun' linked to mass extinctions"], New Scientist, 9 January 2002</ref> or gamma-ray bursts, any of which could reduce sunlight and fry the planet with [[radiation]].

==Implausible causes==
*[[Aliens]]<ref name=griffiths>[http://www.dailymail.co.uk/sciencetech/article-2386923/The-10-strangest-dinosaur-extinction-theories-suggested-experts.html "From cataracts and caterpillars to a planet overrun with males: The 10 strangest dinosaur extinction theories ever suggested by experts"], Sarah Griffiths, Daily Mail, 8 August 2013</ref> ([[aliensdidit]])
*[[Global flood|God killing stuff]] ([[goddidit]])

==Gallery==
<gallery>
File:Late_Ordovician_Extinction.webp|Late Ordivician extinction
File:Late_Devonian_Extinction.jpg|Late Devonian extinction
File:Permian-Triassic_Extinction.jpg|Permian-Triassic extinction
File:Triassic-Jurassic_Extinction.jpg|Triassic-Jurassic extinction
File:Cretaceous-Paleogene_Extinction.jpg|Cretaceous-Paleogene extinction
</gallery>

==See also==
*[[Comet Elenin]] - for what happens when conspiracy theorists decide that Hollywood fiction is a deeply masked message about reality.
*[[History of the Earth]]
*[[List of predictions of the end of the world]]
*[[K-Pg extinction event]] - the last one to occur… until now, that is.
*[[Holocene extinction]] - the one that's happening now, the extinction to end all extinctions.

==References==
{{reflist}}

[[Category:Ancient history]]
[[Category:Conspiracy theories]]
[[Category:Paleontology]]
[[Category:Zoology]]

Categories: Ancient history, Conspiracy theories, Paleontology, Zoology