Editing Extinction event (section)

===Identifying causes of specific mass extinctions===
A good theory for a particular mass extinction should: 
* explain all of the losses, not just focus on a few groups (such as dinosaurs); 
* explain why particular groups of organisms died out and why others survived;
* provide mechanisms that are strong enough to cause a mass extinction but not a total extinction; 
* be based on events or processes that can be shown to have happened, not just inferred from the extinction.

It may be necessary to consider combinations of causes. For example, the marine aspect of the [[Cretaceous–Paleogene extinction event|end-Cretaceous]] extinction appears to have been caused by several processes that partially overlapped in time and may have had different levels of significance in different parts of the world.<ref>{{cite journal | vauthors = Marshall CR, Ward PD | title = Sudden and Gradual Molluscan Extinctions in the Latest Cretaceous of Western European Tethys | journal = Science | volume = 274 | issue = 5291 | pages = 1360–1363 | date = November 1996 | pmid = 8910273 | doi = 10.1126/science.274.5291.1360 | s2cid = 1837900 | bibcode = 1996Sci...274.1360M }}</ref>

Arens and West (2006) proposed a "press / pulse" model in which mass extinctions generally require two types of cause: long-term pressure on the eco-system ("press") and a sudden catastrophe ("pulse") towards the end of the period of pressure.<ref>{{cite conference | vauthors = Arens NC, West ID |year=2006 |title=Press/pulse: A general theory of mass extinction? |conference=[[Geological Society of America]]
 |url=http://gsa.confex.com/gsa/2006AM/finalprogram/abstract_111772.htm  
 |archive-url=https://web.archive.org/web/20170118164705/https://gsa.confex.com/gsa/2006AM/finalprogram/abstract_111772.htm
 |archive-date=2017-01-18
}}
</ref>
Their statistical analysis of marine extinction rates throughout the [[Phanerozoic]] suggested that neither long-term pressure alone nor a catastrophe alone was sufficient to cause a significant increase in the extinction rate.