Editing Meteor Crater (section)

==Formation==
[[File:meteoroid_size_comparison.svg|thumb|upright=1.2|Comparison of approximate sizes of notable impactors with the [[Hoba meteorite]], a [[Boeing 747]] and a [[New Routemaster]] bus]]
The crater was created about 50,000 years ago during the [[Pleistocene]] [[epoch (geology)|epoch]], when the local climate on the [[Colorado Plateau]] was much cooler and damper.<ref>{{cite journal |last=Roddy |first=D. J. |author2=E. M. Shoemaker |date=1995 |title=Meteor Crater (Barringer Meteorite Crater), Arizona: summary of impact conditions |journal=Meteoritics |volume=30 |issue=5 |page=567|bibcode=1995Metic..30Q.567R }}</ref><ref>{{cite journal |doi=10.1016/0016-7037(91)90388-L |last=Nishiizumi |first=K. |author2=Kohl, C.P. |author3=Shoemaker, E.M. |author4=Arnold, J.R. |author5=Klein, J. |author6=Fink, D. |author7= Middleton, R.  |date=1991 |title=In situ 10Be-26Al exposure ages at Meteor Crater, Arizona |journal=Geochimica et Cosmochimica Acta |volume=55 |issue=9 |pages=2699–2703|bibcode = 1991GeCoA..55.2699N |url=https://zenodo.org/record/1253888 }}</ref> The area was an open grassland dotted with woodlands inhabited by [[mammoth]]s and [[ground sloth|giant ground sloths]].<ref>{{cite journal|last=Kring|first=David|title=Air blast produced by the Meteor Crater impact event and a reconstruction of the affected environment|journal=Meteoritics and Planetary Science|volume=32|issue=4|pages=517–30|doi=10.1111/j.1945-5100.1997.tb01297.x|year=1997|bibcode=1997M&PS...32..517K|doi-access=free}}</ref><ref>{{cite web|last=Kring|first=David|title=Barringer Meteor Crater and Its Environment|url=http://www.lpi.usra.edu/science/kring/epo_web/impact_cratering/enviropages/Barringer/barringerstartpage.html|publisher=Lunar and Planetary Institute|access-date=2014-02-12}}</ref>

The object that excavated the crater was a [[nickel]]-[[iron]] meteorite about {{convert|50|m|ft|abbr=on|order=flip}} across. The speed of the impact has been a subject of some debate. Modeling initially suggested that the meteorite struck at up to {{cvt|20|km/s|mph||order=flip|abbr=on}}, but more recent research suggests the impact was substantially slower, at {{cvt|12.8|km/s|mph||order=flip|abbr=on}}. About half of the impactor's bulk is believed to have been vaporized during its descent through the atmosphere.<ref name="r1">{{cite journal| author=Melosh HJ| author2=Collins GS| title=Planetary science: Meteor Crater formed by low-velocity impact | journal=[[Nature (journal)|Nature]] | volume=434 | issue=7030 | date=2005 | page=157 | pmid=15758988 | doi=10.1038/434157a |bibcode = 2005Natur.434..157M| s2cid=2126679| doi-access=free }}</ref> Impact energy has been estimated at 10 [[TNT equivalent|megatons TNT<sub>e</sub>]]. The meteorite was mostly vaporized upon impact, leaving few remains in the crater.<ref>Schaber, Gerald G. [http://pubs.usgs.gov/of/2005/1190/of2005-1190.pdf "The U.S. Geological Survey, Branch of Astrogeology – A Chronology of Activities from Conception through the End of Project Apollo (1960–1973)"], 2005, U.S. Geological Survey Open-File Report 2005-1190. (PDF)</ref>

Since the crater's formation, the rim is thought to have lost {{convert|15|–|20|m|ft|abbr=on|order=flip|round=5}} of height at the rim crest as a result of natural [[erosion]]. Similarly, the basin of the crater is thought to have roughly {{convert|30|m|ft|abbr=on|order=flip|round=5}} of additional postimpact sedimentation from lake sediments and [[alluvium]].<ref>{{cite journal|last1= Poelchau|first1= Michael|last2= Kenkmann|first2= Thomas|last3= Kring|first3= David|date= 2009|title= Rim uplift and crater shape in Meteor Crater: Effects of target heterogeneities and trajectory obliquity|journal= Journal of Geophysical Research|publisher=AGU |volume= 114|issue= E1|pages= E01006|doi= 10.1029/2008JE003235|bibcode= 2009JGRE..114.1006P|doi-access= free}}</ref> Very few remaining craters are visible on Earth, since many have been erased by erosive geological processes. The relatively young age of Meteor Crater, paired with the dry Arizona climate, has allowed this crater to remain comparatively unchanged since its formation. The lack of erosion that preserved the crater's shape greatly accelerated its groundbreaking recognition as an impact crater from a natural celestial body.<ref>{{cite web|url=http://www.scienceclarified.com/landforms/Faults-to-Mountains/Meteorite-Crater.html|title=Meteorite Crater – The shape of the land, Forces and changes, Spotlight on famous forms, For More Information|work=scienceclarified.com}}</ref>