Editing Catastrophism (section)

==Current application==
Neocatastrophism is the explanation of sudden extinctions in the palaeontological record by high magnitude, low frequency events (such as asteroid impacts, super-volcanic eruptions, supernova gamma ray bursts, etc.), as opposed to the more prevalent [[Geomorphology|geomorphological]] thought which emphasises low magnitude, high frequency events.<ref>{{cite book |last1=Goudie |first1=A. |title=Encyclopedia of Geomorphology |page=709 }}</ref>

===Luis Alvarez impact event hypothesis===
{{Main|Cretaceous–Paleogene extinction event}}
In 1980, [[Walter Alvarez|Walter]] and [[Luis Walter Alvarez|Luis Alvarez]] published a paper suggesting that a {{convert|10|km|mi}} [[asteroid]] [[Impact event|struck Earth]] 66 million years ago at the end of the [[Cretaceous]] period. The impact wiped out about 70% of all species, including the non-avian [[dinosaur]]s, leaving behind the [[Cretaceous–Paleogene boundary]] (K–T boundary). In 1990, a {{convert|180|km|mi}} candidate crater marking the impact was identified at [[Chicxulub crater|Chicxulub]] in the [[Yucatán Peninsula]] of [[Mexico]]. These events sparked a wide acceptance of a scientifically based catastrophism with regard to certain events in the distant past. 

Since then, the debate about the [[extinction]] of the dinosaurs and other [[mass extinction]] events has centered on whether the extinction mechanism was the asteroid impact, widespread volcanism (which occurred about the same time), or some other mechanism or combination. Most of the mechanisms suggested are catastrophic in nature.

The observation of the [[Comet Shoemaker-Levy 9|Shoemaker-Levy 9]] cometary collision with Jupiter illustrated that catastrophic events occur as natural events.

===Moon-formation===
{{Main|Giant impact theory}}
Modern theories also suggest that Earth's anomalously large [[moon]] was formed catastrophically. In a paper published in ''Icarus'' in 1975, [[William K. Hartmann]] and [[Donald R. Davis (astronomer)|Donald R. Davis]] proposed that a catastrophic near-miss by a large [[planetesimal]] early in Earth's formation approximately 4.5 billion years ago blew out rocky debris, remelted Earth and formed the [[Moon]], thus explaining the Moon's lesser density and [[Internal structure of the Moon|lack of an iron core]].<ref>{{cite journal |last2=Gott III |first1=J. R. |year=2005 |title=Where Did The Moon Come From? |journal= [[The Astronomical Journal]] |volume= 129 | issue=3 | pages= 1724–1745 |arxiv=astro-ph/0405372 |bibcode=2005AJ....129.1724B |doi=10.1086/427539 |last1=Belbruno |first2=J. Richard|s2cid=12983980 }}</ref> The impact theory does have some faults; some computer simulations show the formation of a ring or multiple moons post impact, and elements are not quite the same between the Earth and Moon.<ref>{{cite web |date=September 2009 |title=Moonwalk  |url=http://www.geolsoc.org.uk/webdav/site/GSL/shared/pdfs/Geoscientist/Download%20PDF%20copy%20of%20Geoscientist%2019.9%20September%202009.pdf |publisher=[[Geological Society of London]] |access-date=2010-03-01}}</ref><ref>{{cite journal |last1=Binder |first1=A.B. |year=1974 |title=On the origin of the Moon by rotational fission |journal=[[The Moon]] |volume=11 |issue=2 |pages=53–76 |bibcode=1974Moon...11...53B |doi=10.1007/BF01877794|s2cid=122622374 }}</ref><ref>{{cite journal |last1= Stevenson |first1=D. J. |year=1987 |title=Origin of the Moon-The Collision Hypothesis |journal=Annual Review of Earth and Planetary Sciences |volume= 15|pages= 271–315|bibcode=1987AREPS..15..271S |doi=10.1146/annurev.ea.15.050187.001415 }}</ref>