Extinction event

An extinction event (EE), also referred to as a mass extinction, is an event where the majority of species (mostly animals) on the planet become extinct. This is opposed to normal extinctions 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; historical extinction would be the asteroid impact that killed off the non- avian dinosaurs (the K-Pg extinction event); 65 million years ago. 50% of plants and animals (marine reptiles, ammonites, pterosaurs) died out. Many of them being animals that coexisted with dinosaurs, including mammals, birds, fish, and insects.
However, this pales in magnitude compared to the event, which ended the Permian period 252 million years ago. 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."The Great Dying", NASA, 2002
Similar explanations are suggested for the around 201 million years ago. Dinosaurs actually became dominant after this mass extinction, gaining a wider variety of niches after non dinosaurian reptile competitors died off.
The 360-375 million years ago 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 — as well as habitat loss, climate change, and poaching/overhunting. The biggest group of animals being affected are megafauna (large animals like 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 with dust.
*Massive volcanoes, causing either global warming or 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, etc.
*Changes in atmospheric oxygen, most obviously due to the widespread proliferation of : the 
*Astronomical effects: dark matter,"Does dark matter cause mass extinctions and geologic upheavals?", Astronomy Now, 2015 supernovae,"Supernova 'smoking gun' linked to mass extinctions", New Scientist, 9 January 2002 or gamma-ray bursts, any of which could reduce sunlight, fry the planet with radiation, and provoke mass panic and suicide.
==Implausible causes==
*Aliens"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 (aliensdidit)
*God killing stuff (goddidit)
==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
==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==
Category:Ancient history
Category:Conspiracy theories
Category:Paleontology
Category:Zoology