Editing Chicxulub crater

{{Short description|Prehistoric impact crater in Mexico}}
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{{Use American English|date=October 2022}}
{{Use mdy dates|date=July 2022}}
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{{Infobox terrestrial impact site
| name          = Chicxulub crater
| other_name    = Chicxulub impact structure
| photo         = Yucatan chix crater.jpg
| photo_caption = Imaging from [[NASA]]'s Shuttle Radar Topography Mission [[STS-99]] reveals part of the diameter ring of the crater in the form of a shallow circular trough. Numerous [[cenote]]s ([[sinkhole]]s) cluster around the trough marking the inner crater rim.<ref name="NASA PIA03379">{{Cite web |title=PIA03379: Shaded Relief with Height as Color, Yucatan Peninsula, Mexico |url=http://photojournal.jpl.nasa.gov/catalog/PIA03379 |url-status=live |archive-url=https://web.archive.org/web/20170313212222/http://photojournal.jpl.nasa.gov/catalog/PIA03379 |archive-date=March 13, 2017 |access-date=October 28, 2010 |website=[[Shuttle Radar Topography Mission]] |publisher=[[NASA]]}}</ref>
| map           = North America#Mexico
| map_caption   = Location of Chicxulub crater
| coordinates   = {{Coord|21|24|0|N|89|31|0|W|type:landmark_scale:5000000_region:MX-YUC|display=inline,title}}
| confidence    = Confirmed
| diameter      = {{convert|200|km|abbr=on}}
| depth         = {{convert|1|km|abbr=on}}
| age           = 66.043 ± 0.043 Ma<br />[[Cretaceous–Paleogene boundary]]<ref name="RenneDeino2013">{{Cite journal |last1=Renne |first1=P. R. |last2=Deino |first2=A.L. |last3=Hilgen |first3=F.J. |last4=Kuiper |first4=K.F. |last5=Mark |first5=D.F. |last6=Mitchell |first6=W.S. |last7=Morgan |first7=L.E. |last8=Mundil |first8=R. |last9=Smit |first9=J. |display-authors=3 |year=2013 |title=Time Scales of Critical Events Around the Cretaceous-Paleogene Boundary |url=https://eps.harvard.edu/files/eps/files/renne.kt_.science.2013.pdf |url-status=live |journal=Science |volume=339 |issue=6120 |pages=684–687 |bibcode=2013Sci...339..684R |doi=10.1126/science.1230492 |issn=0036-8075 |pmid=23393261 |archive-url=https://web.archive.org/web/20180403154929/https://eps.harvard.edu/files/eps/files/renne.kt_.science.2013.pdf |archive-date=April 3, 2018 |access-date=July 28, 2017 |s2cid=6112274}}</ref>
| exposed       = No
| drilled       = Yes
| imp_size      = {{convert|10|km|abbr=on}}
| bolide        = [[CM chondrite|CM]] or [[CR chondrite|CR]] type [[carbonaceous chondrite]]
| country       = Mexico
| state         = [[Yucatán]]
}}
The '''Chicxulub crater''' ({{IPAc-en|tʃ|iː|k|ʃ|uː|ˈ|l|uː|b}} {{respell|cheek|shoo|LOOB}}; {{IPA|es|tʃikʃuˈlub|lang|Chicxulub.ogg}}) is an [[impact crater]] buried underneath the [[Yucatán Peninsula]] in Mexico. Its center is offshore, but the crater is named after the onshore community of [[Chicxulub Pueblo]] (not the larger coastal town of [[Chicxulub Puerto]]).<ref name="Penfield"/> It was formed slightly over 66 [[million years ago]] when an [[asteroid]], about {{convert|10|km|mi|0|abbr=off|sp=us|spell=on}} in diameter, struck [[Earth]]. The crater is estimated to be {{convert|200|km|abbr=off|sp=us}} in diameter and {{convert|1|km|abbr=off|sp=us}} in depth. It is believed to be [[List of impact craters on Earth#10 Ma or more|the second largest impact structure on Earth]], and the only one whose [[peak ring]] is intact and directly accessible for scientific research.<ref name="SchulteOthers2010"/>

The crater was discovered by Antonio Camargo and Glen Penfield, geophysicists who had been looking for petroleum in the Yucatán Peninsula during the late 1970s. Penfield was initially unable to obtain evidence that the geological feature was a crater and gave up his search. Later, through contact with [[Alan R. Hildebrand]] in 1990, Penfield obtained samples that suggested it was an impact feature. Evidence for the crater's impact origin includes [[shocked quartz]], a [[gravity anomaly]], and [[tektite]]s in surrounding areas.<ref name="Penfield"/>

The date of the impact coincides with the [[Cretaceous–Paleogene boundary]] (commonly known as the K–Pg or K–T boundary). It is now widely accepted that the devastation and [[impact winter|climate disruption]] resulting from the impact was the primary cause of the [[Cretaceous–Paleogene extinction event]], a [[mass extinction]] of 75% of plant and animal species on Earth, including all [[Dinosaur|non-avian dinosaurs]].<ref name="SchulteOthers2010"/>

==Discovery==
In the late 1970s, geologist [[Walter Alvarez]] and his father, [[Nobel Prize]]–winning scientist [[Luis Walter Alvarez]], put forth their theory that the [[Cretaceous–Paleogene extinction event|Cretaceous–Paleogene extinction]] was caused by an impact event.<ref name="Bates_1992"/><ref name="newyorker_2019-03-29"/> The main evidence of such an impact was contained in a thin layer of clay present in the [[Cretaceous–Paleogene boundary]] (K–Pg boundary) in [[Gubbio|Gubbio, Italy]]. The Alvarezes and colleagues reported that it contained an [[iridium anomaly|abnormally high concentration of iridium]], a chemical element rare on Earth but common in asteroids.<ref name="Bates_1992"/><ref>{{Cite conference |last1=Alvarez, W. |author-link=Walter Alvarez |last2=Alvarez, L.W. |author-link2=Luis Walter Alvarez |last3=Asaro, F. |last4=Michel, H.V. |year=1979 |editor2-last=Birkelund, T. |title=Anomalous iridium levels at the Cretaceous/Tertiary boundary at Gubbio, Italy: Negative results of tests for a supernova origin |location=[[University of Copenhagen]], Copenhagen, Denmark| volume=2 |pages=69 |book-title=Cretaceous/Tertiary Boundary Events Symposium |editor=Christensen, W.K.}}; {{cite journal | first1=Luann | last1=Becker | url=http://www.miracosta.edu/home/kmeldahl/articles/blows.pdf | title=Repeated Blows | access-date=January 28, 2016 | journal=Scientific American | year=2002 | volume=286 | issue=3 | pages=76–83 | bibcode=2002SciAm.286c..76B | doi=10.1038/scientificamerican0302-76 | pmid=11857903 | archive-date=December 8, 2003 | archive-url=https://web.archive.org/web/20031208144031/http://www.miracosta.edu/home/kmeldahl/articles/blows.pdf | url-status=live }}</ref> [[Iridium]] levels in this layer were as much as 160 times above the background level.<ref name="Alvarez et al-1980" /> It was hypothesized that the iridium was spread into the atmosphere when the impactor was [[vaporized]] and settled across Earth's surface among other material thrown up by the impact, producing the layer of iridium-enriched clay.<ref>{{Cite web |first=Hillary|last=Mayell |date=May 15, 2005 |title=Asteroid Rained Glass Over Entire Earth, Scientists Say |url=http://news.nationalgeographic.com/news/2005/04/0415_050418_chicxulub.html |url-status=dead |archive-url=https://web.archive.org/web/20160918074556/http://news.nationalgeographic.com/news/2005/04/0415_050418_chicxulub.html |archive-date=September 18, 2016 |access-date=October 1, 2007 |website=[[National Geographic Society|National Geographic]] News}}</ref> At the time, there was no consensus on what caused the Cretaceous–Paleogene extinction and the boundary layer, with theories including a nearby [[supernova]], [[climate change]], or a [[geomagnetic reversal]].<ref name="Alvarez et al-1980">{{Cite journal |last1=Alvarez |first1=Luis |last2=Alvarez |first2=Walter |last3=Asaro |first3=Frank |last4=Michel |first4=Helen |date=June 6, 1980 |title=Extraterrestrial Cause for the Cretaceous-Tertiary Extinction |journal=[[Science (journal)|Science]] |volume=208 |issue=4408 |pages=1095–1108 |bibcode=1980Sci...208.1095A |doi=10.1126/science.208.4448.1095 |issn=0036-8075 |pmid=17783054 |s2cid=16017767}}</ref>{{rp|1095}} The Alvarezes' impact hypothesis was rejected by many paleontologists, who believed that the lack of fossils found close to the K–Pg boundary—the "three-meter problem"—suggested a more gradual die-off of fossil species.<ref name="newyorker_2019-03-29" /><ref name="Alvarez_2008"/>

The Alvarezes, joined by [[Frank Asaro]] and [[Helen Vaughn Michel|Helen Michel]] from [[University of California, Berkeley]], published their paper on the iridium anomaly in ''[[Science (journal)|Science]]'' in June 1980.<ref name="Alvarez et al-1980" /> Almost simultaneously [[Jan Smit (paleontologist)|Jan Smit]] and Jan Hertogen published their iridium findings from Caravaca, Spain, in ''[[Nature (journal)|Nature]]'' in May 1980.<ref name="Smit and Hertogen-1980" /> These papers were followed by other reports of similar iridium spikes at the K–Pg boundary across the globe, and sparked wide interest in the cause of the K–Pg extinction; over 2,000 papers were published in the 1980s on the topic.<ref name="Alvarez_2008"/>{{rp|82}}<ref name="Weinreb_2002"/> There were no known impact craters that were the right age and size, spurring a search for a suitable candidate.<ref name="newyorker_2019-03-29"/> Recognizing the scope of the work, Lee Hunt and Lee Silver organized a cross-discipline meeting in [[Snowbird, Utah]], in 1981. Unknown to them, evidence of the crater they were looking for was being presented the same week, and would be largely missed by the scientific community.<ref name="Alvarez_2008"/>{{rp|83–84}}<ref name="Weinreb_2002"/>

[[File:Chicxulub impact - artist impression.jpg|thumb|alt=A painting depicting the asteroid impacting Earth, creating the Chicxulub crater| Artist's impression of the asteroid slamming into tropical, shallow seas of the sulfur-rich [[Yucatán Peninsula]] in what is today [[Geography of Mexico|Southeast Mexico]].<ref name="nhm.ac.uk">{{Cite web |last=Osterloff |first=Emily |year=2018 |title=How an asteroid ended the age of the dinosaurs |url=https://www.nhm.ac.uk/discover/how-an-asteroid-caused-extinction-of-dinosaurs.html |url-status=live |archive-url=https://web.archive.org/web/20220426174952/https://www.nhm.ac.uk/discover/how-an-asteroid-caused-extinction-of-dinosaurs.html |archive-date=April 26, 2022 |access-date=May 18, 2022 |publisher=[[Natural History Museum, London|Natural History Museum]] |location=London, England}}</ref> The aftermath of the asteroid collision, which occurred approximately 66 million years ago, is believed to have caused the [[Extinction event|mass extinction]] of non-avian dinosaurs and many other species on Earth.<ref name="nhm.ac.uk" /> The impact spewed hundreds of billions of tons of sulfur into the atmosphere, producing a worldwide blackout and freezing temperatures which persisted for at least a decade.<ref name="nhm.ac.uk" />]]
In 1978, geophysicists Glen Penfield and Antonio Camargo were working for the Mexican state-owned oil company Petróleos Mexicanos ([[Pemex]]) as part of an airborne magnetic survey of the [[Gulf of Mexico]] north of the [[Yucatán Peninsula]].<ref name="Verschuur_1996"/>{{rp|20–21}} Penfield's job was to use geophysical data to scout possible locations for oil drilling.<ref name="Bates_1992"/> In the offshore magnetic data, Penfield noted anomalies whose depth he estimated and mapped. He then obtained onshore [[gravity anomaly|gravity data]] from the 1940s. When the gravity maps and [[Magnetic anomaly|magnetic anomalies]] were compared, Penfield described a shallow "bullseye", {{convert|180|km|abbr=on|sp=us}} in diameter, appearing on the otherwise non-magnetic and uniform surroundings—clear evidence to him of an impact feature.<ref name="Bates_1992"/><ref name="Penfield">{{Cite journal |last=Penfield |first=Glen |year=2019 |title=Unlikely Impact |url=https://explorer.aapg.org/story?articleid=55293 |url-status=live |journal=AAPG Explorer |volume=40 |issue=12 |pages=20–23 |archive-url=https://web.archive.org/web/20210116205711/https://explorer.aapg.org/story?articleid=55293 |archive-date=January 16, 2021 |access-date=December 12, 2019}}</ref> A decade earlier, the same map had suggested a crater to contractor Robert Baltosser, but Pemex corporate policy prevented him from publicizing his conclusion.<ref name="Verschuur_1996"/>{{rp|20}}

Penfield presented his findings to Pemex, who rejected the crater theory, instead deferring to findings that ascribed the feature to volcanic activity.<ref name="Penfield" /> Pemex disallowed release of specific data, but let Penfield and Camargo present the results at the 1981 [[Society of Exploration Geophysicists]] conference.<ref name="Weinreb_2002"/> That year's conference was under-attended and their report attracted little attention, with many experts on impact craters and the K–Pg boundary attending the Snowbird conference instead. Carlos Byars, a ''[[Houston Chronicle]]'' journalist who was familiar with Penfield and had seen the gravitational and magnetic data himself, wrote a front-page story<ref>{{Cite news |last=Byars |first=Carlos |date=1981-12-13 |title=Mexican site may be a link to dinosaurs' disappearance |url=https://infoweb.newsbank.com/apps/news/openurl?ctx_ver=z39.88-2004&rft_id=info%3Asid/infoweb.newsbank.com&svc_dat=AMNEWS&req_dat=0D1C2A34C3EF45E0&rft_val_format=info%3Aofi/fmt%3Akev%3Amtx%3Actx&rft_dat=document_id%3Aimage%252Fv2%253A14DB39C1C40322B4%2540EANX-NB-1642F1C7C1E6C3CA%25402444952-1642EDDD95D04DD1%25400-1642EDDD95D04DD1%2540 |access-date=2024-09-01 |work=[[Houston Chronicle]] |pages=1, 18 |type=Newspaper [digital microfilm] |edition=Final |via=[[NewsBank]] |volume=81 |issue=61}}</ref> on Penfield and Camargo's claim, but the news did not propagate widely.<ref name="Verschuur_1996"/>{{rp|23}}

Although Penfield had plenty of geophysical data sets, he had no rock cores or other physical evidence of an impact.<ref name="Bates_1992"/> He knew Pemex had drilled exploratory wells in the region. In 1951, one well bored into what was described as a thick layer of [[andesite]] about {{convert|1.3|km|ft|sp=us}} down. This layer could have resulted from the intense heat and pressure of an Earth impact, but at the time of the borings it was dismissed as a [[lava dome]]—a feature uncharacteristic of the region's geology.<ref name="Bates_1992"/> Penfield was encouraged by [[William C. Phinney]], curator of [[lunar rock]]s at the [[Johnson Space Center]], to find these samples to support his hypothesis.<ref name="Penfield" /> Penfield tried to secure site samples, but was told they had been lost or destroyed. When attempts to return to the drill sites to look for corroborating rocks proved fruitless, Penfield abandoned his search, published his findings and returned to his Pemex work.<ref name="Bates_1992"/> Seeing the 1980 ''Science'' paper, Penfield wrote to Walter Alvarez about the Yucatán structure, but received no response.<ref name="Weinreb_2002"/>

Alvarez and other scientists continued their search for the crater, although they were searching in oceans based on incorrect analysis of glassy [[spherule]]s from the K–Pg boundary that suggested the impactor had landed in open water.<ref name="Alvarez_2008"/> Unaware of Penfield's discovery, [[University of Arizona]] graduate student [[Alan R. Hildebrand]] and faculty adviser William V. Boynton looked for a crater near the [[Brazos River]] in [[Texas]].<ref name="Alvarez_2008"/> Their evidence included greenish-brown clay with surplus iridium, containing [[shocked quartz]] grains and small weathered glass beads that looked to be [[tektite]]s.<ref name="Hildebrand et al_1991-09"/> Thick, jumbled deposits of coarse rock fragments were also present, thought to have been scoured from one place and deposited elsewhere by an impact event. Such deposits occur in many locations but seemed concentrated in the [[Caribbean Basin]] at the K–Pg boundary. When Haitian professor Florentine Morás discovered what he thought to be evidence of an ancient volcano on [[Haiti]], Hildebrand suggested it could be a telltale feature of a nearby impact. Tests on samples retrieved from the K–Pg boundary revealed more tektite glass, formed only in the heat of asteroid impacts and high-yield [[nuclear weapon|nuclear detonations]].<ref name="Bates_1992"/>

In 1990, Carlos Byars told Hildebrand of Penfield's earlier discovery of a possible impact crater.<ref>{{Cite book |last=Frankel, Charles |title=The End of the Dinosaurs: Chicxulub Crater and Mass Extinctions |date=1999 |publisher=[[Cambridge University Press]] |location=Cambridge, England|isbn=978-0-521-47447-4 |page=[https://archive.org/details/endofdinosaursch00fran/page/236 236]}}</ref>{{rp|50}} Hildebrand contacted Penfield and the pair soon secured two drill samples from the Pemex wells, which had been stored in [[New Orleans]] for decades.<ref name="Penfield" /> Hildebrand's team tested the samples, which clearly showed [[shock metamorphism|shock-metamorphic]] materials.<ref name="Bates_1992"/> A team of California researchers surveying satellite images found a [[cenote]] ([[sinkhole]]) ring centered on the town of [[Chicxulub Pueblo]] that matched the one Penfield saw earlier; the cenotes were thought to be caused by [[subsidence]] of [[bolide]]-weakened [[lithostratigraphy]] around the impact crater wall.<ref>{{Cite journal |last1=Pope KO |last2=Baines, K.H. |last3=Ocampo, A.C. |last4=Ivanov, B.A. |year=1997 |title=Energy, volatile production, and climatic effects of the Chicxulub Cretaceous/Tertiary impact |journal=[[Journal of Geophysical Research]] |publisher=[[American Geophysical Union]] |location=Washington, D.C.| volume=102 |issue=E9 |pages=245–264 |bibcode=1997JGR...10221645P |doi=10.1029/97JE01743 |pmid=11541145 |doi-access=free}}</ref> More recent evidence suggests the crater is {{convert|300|km|abbr=on}} wide, and the {{convert|180|km|adj=on|abbr=on|sp=us}} ring observed is an inner wall of the larger crater.<ref>{{Cite journal |first1=Vernon L.|last1=Sharpton  |first2=Luis E.|last2=Marin |date=May 1997 |title=The Cretaceous–Tertiary impact crater and the cosmic projectile that produced it |journal=[[Annals of the New York Academy of Sciences]] | publisher=[[Wiley-Blackwell]]| location=New York City| volume=822 |issue=1 |pages=353–380 |bibcode=1997NYASA.822..353S |doi=10.1111/j.1749-6632.1997.tb48351.x |pmid=11543120 |s2cid=11962090}}</ref> Hildebrand, Penfield, Boynton, Camargo, and others published their paper identifying the crater in 1991.<ref name="Alvarez_2008"/><ref name="Hildebrand et al_1991-09"/> The crater was named for the nearby town of [[Chicxulub Pueblo]]. Penfield also recalled that part of the motivation for the name was "to give the academics and NASA naysayers a challenging time pronouncing it" after years of dismissing its existence.<ref name="Penfield" />

In March 2010, forty-one experts from many countries reviewed the available evidence: twenty years' worth of data spanning a variety of fields. They concluded that the impact at Chicxulub triggered the mass extinctions at the K–Pg boundary.<ref name="newyorker_2019-03-29"/><ref name="SchulteOthers2010">{{Cite journal |last1=Schulte |first1=P. |last2=Alegret |first2=L. |last3=Arenillas |first3=I. |last4=Arz |first4=J. A. |last5=Barton |first5=P.J. |last6=Bown |first6=P.R. |last7=Bralower |first7=T.J. |last8=Christeson |first8=G.L. |last9=Claeys |first9=P. |display-authors=3 |year=2010 |title=The Chicxulub Asteroid Impact and Mass Extinction at the Cretaceous-Paleogene Boundary |url=http://www3.nd.edu/~cneal/CRN_Papers/Schulte10_Sci_Chicxulub.pdf |journal=Science |volume=327 |issue=5970 |pages=1214–1218 |doi=10.1126/science.1177265 |issn=0036-8075 |archive-url=https://web.archive.org/web/20111209132114/http://www.nd.edu/~cneal/CRN_Papers/Schulte10_Sci_Chicxulub.pdf |archive-date=December 9, 2011 |access-date=December 9, 2016 |last10=Cockell |first10=C.S. |last11=Collins |first11=G.S. |last12=Deutsch |first12=A. |last13=Goldin |first13=T.J. |last14=Goto |first14=K. |last15=Grajales-Nishimura |first15=J. M. |last16=Grieve |first16=R.A.F. |last17=Gulick |first17=S.P.S. |last18=Johnson |first18=K.R. |last19=Kiessling |first19=W. |last20=Koeberl |first20=C. |last21=Kring |first21=D. A. |last22=MacLeod |first22=K.G. |last23=Matsui |first23=T. |last24=Melosh |first24=J. |last25=Montanari |first25=A. |last26=Morgan |first26=J.V.|author26-link= Joanna Morgan |last27=Neal |first27=C.R. |last28=Nichols |first28=D.J. |last29=Norris |first29=R. D. |last30=Pierazzo |first30=E. |last31=Ravizza |first31=G. |last32=Rebolledo-Vieyra |first32=M. |last33=Reimold |first33=W.U. |last34=Robin |first34=E. |last35=Salge |first35=T. |last36=Speijer |first36=R.P. |last37=Sweet |first37=A.R. |last38=Urrutia-Fucugauchi |first38=J. |last39=Vajda |first39=V. |last40=Whalen |first40=M.T. |last41=Willumsen |first41=P.S. |pmid=20203042|bibcode=2010Sci...327.1214S |s2cid=2659741 }}; {{Cite news |last=Rincon, Paul |date=March 4, 2010 |title=Dinosaur extinction link to crater confirmed |publisher=[[BBC]] |url=http://news.bbc.co.uk/2/hi/science/nature/8550504.stm |url-status=live |access-date=March 5, 2010 |archive-url=https://web.archive.org/web/20191031034913/http://news.bbc.co.uk/2/hi/science/nature/8550504.stm |archive-date=October 31, 2019}}</ref> Dissenters, notably [[Gerta Keller]] of [[Princeton University]], have proposed an alternate culprit: the eruption of the [[Deccan Traps]] in what is now the [[Indian subcontinent]]. This period of intense [[volcanism]] occurred before and after the Chicxulub impact;<ref name="newyorker_2019-03-29"/><ref name="Keller et al-2020">{{Cite journal |last1=Keller |first1=Gerta |last2=Mateo |first2=Paula |last3=Monkenbusch |first3=Johannes |last4=Thibault |first4=Nicolas |last5=Punekar |first5=Jahnavi |last6=Spangenberg |first6=Jorge E. |last7=Abramovich |first7=Sigal |last8=Ashckenazi-Polivoda |first8=Sarit |last9=Schoene |first9=Blair |last10=Eddy |first10=Michael P. |last11=Samperton |first11=Kyle M. |last12=Khadri |first12=Syed F.R. |last13=Adatte |first13=Thierry |display-authors=3 |date=November 2020 |title=Mercury linked to Deccan Traps volcanism, climate change and the end-Cretaceous mass extinction |journal=Global and Planetary Change |volume=194 |pages=103312 |bibcode=2020GPC...19403312K |doi=10.1016/j.gloplacha.2020.103312 |s2cid=225275560|doi-access=free }}</ref> dissenting studies argue that the worst of the volcanic activity occurred ''before'' the impact, and the role of the Deccan Traps was instead shaping the evolution of surviving species post-impact.<ref>{{Cite journal |last1=Hull |first1=Pincelli M. |last2=Bornemann |first2=André |last3=Penman |first3=Donald E. |last4=Henehan |first4=Michael J. |last5=Norris |first5=Richard D. |last6=Wilson |first6=Paul A. |last7=Blum |first7=Peter |last8=Alegret |first8=Laia |last9=Batenburg |first9=Sietske J. |last10=Bown |first10=Paul R. |last11=Bralower |first11=Timothy J. |display-authors=3 |date=January 17, 2020 |title=On impact and volcanism across the Cretaceous-Paleogene boundary |journal=Science |language=en |volume=367 |issue=6475 |pages=266–272 |bibcode=2020Sci...367..266H |doi=10.1126/science.aay5055 |issn=0036-8075 |pmid=31949074 |s2cid=210698721|doi-access=free |hdl=20.500.11820/483a2e77-318f-476a-8fec-33a45fbdc90b |hdl-access=free }}</ref> A 2013 study compared [[isotope]]s in [[impact glass]] from the Chicxulub impact with isotopes in ash from the K–Pg boundary, concluding that they were dated almost exactly the same, and within experimental error.<ref name="RenneDeino2013"/>

==Impact specifics==
[[File:Chicxulub Free-Air Gravity anomaly.png|thumb|[[Free-air gravity anomaly]] over the Chicxulub structure (coastline and state boundaries shown as black lines)]]

A 2013 study published in ''[[Science (journal)|Science]]'' estimated the age of the impact as 66,043,000 ± 11,000 years ago (± 43,000 years ago considering systematic error), based on multiple lines of evidence, including [[argon–argon dating]] of tektites from Haiti and [[bentonite]] horizons overlying the impact horizon in northeastern [[Montana]].<ref name="RenneDeino2013" /> This date was supported by a 2015 study based on argon–argon dating of [[tephra]] found in [[lignite]] beds in the [[Hell Creek Formation|Hell Creek]] and overlying [[Fort Union Formation|Fort Union]] formations in northeastern Montana.<ref>{{Cite journal |last1=Sprain |first1=C.J. |last2=Renne |first2=P.R. |last3=Wilson |first3=G.P. |last4=Clemens |first4=W.A. |date=March 1, 2015 |title=High-resolution chronostratigraphy of the terrestrial Cretaceous-Paleogene transition and recovery interval in the Hell Creek region, Montana |url=https://pubs.geoscienceworld.org/gsabulletin/article/127/3-4/393-409/126101 |journal=Geological Society of America Bulletin |language=en |volume=127 |issue=3–4 |pages=393–409 |bibcode=2015GSAB..127..393S |doi=10.1130/B31076.1 |issn=0016-7606 |s2cid=129291530}}</ref> A 2018 study based on argon–argon dating of spherules from [[Gorgona Island (Colombia)|Gorgonilla Island]], [[Colombia]], obtained a slightly different result of 66,051,000 ± 31,000 years ago.<ref>{{Cite journal |last1=Renne |first1=Paul R. |last2=Arenillas |first2=Ignacio |last3=Arz |first3=José A. |last4=Vajda |first4=Vivi |last5=Gilabert |first5=Vicente |last6=Bermúdez |first6=Hermann D. |display-authors=3 |date=June 1, 2018 |title=Multi-proxy record of the Chicxulub impact at the Cretaceous-Paleogene boundary from Gorgonilla Island, Colombia |url=https://pubs.geoscienceworld.org/gsa/geology/article/46/6/547/530690/Multiproxy-record-of-the-Chicxulub-impact-at-the |journal=Geology |language=en |volume=46 |issue=6 |pages=547–550 |bibcode=2018Geo....46..547R |doi=10.1130/G40224.1 |issn=0091-7613 |s2cid=135274460}}</ref> The impact has been interpreted to have occurred in the Northern Hemisphere's spring season based on annual [[isotope analysis|isotope curves]] in [[sturgeon]] and [[paddlefish]] bones found in an ejecta-bearing sedimentary unit at the [[Tanis (fossil site)|Tanis site]] in southwestern [[North Dakota]]. This sedimentary unit is thought to have formed within hours of impact.<ref>{{Cite journal |last1=During |first1=Melanie A.D. |last2=Smit |first2=Jan |last3=Voeten |first3=Dennis F.A.E. |last4=Berruyer |first4=Camille |last5=Tafforeau |first5=Paul |last6=Sanchez |first6=Sophie |last7=Stein |first7=Koen H. W. |last8=Verdegaal-Warmerdam |first8=Suzan J.A. |last9=van der Lubbe |first9=Jeroen H.J.L. |display-authors=3 |date=February 23, 2022 |title=The Mesozoic terminated in boreal spring |journal=Nature |volume=603 |issue=7899 |pages=91–94 |bibcode=2022Natur.603...91D |doi=10.1038/s41586-022-04446-1 |pmc=8891016 |pmid=35197634}}</ref> 

The site of the crater at the time of impact was a marine [[carbonate platform]].<ref name="Gulick_etal_2013">{{Cite journal |last1=Gulick |first1=S.P.S. |last2=Christeson |first2=G.L. |last3=Barton |first3=P.J. |last4=Grieve |first4=R.A.F. |last5=Morgan |first5=J.V.|author5-link= Joanna Morgan |last6=Urrutia-Fucugauchi |first6=J. |display-authors=3 |date=January 2013 |title=Geophysical characterization of the Chicxulub impact crater |journal=Reviews of Geophysics |language=en |volume=51 |issue=1 |pages=31–52 |bibcode=2013RvGeo..51...31G |doi=10.1002/rog.20007 |issn=8755-1209 |s2cid=55502139|doi-access=free }}</ref> The water depth at the impact site varied from {{Convert|100|m|ft|sp=us}} on the western edge of the crater to over {{Convert|1200|m|ft|sp=us}} on the northeastern edge, with an estimated depth at the centre of the impact of approximately {{Convert|650|m|ft|sp=us}}.<ref name="Gulick_etal_2008">{{Cite journal |last1=Gulick |first1=Sean P. S. |last2=Barton |first2=Penny J. |last3=Christeson |first3=Gail L. |last4=Morgan |first4=Joanna V.|author4-link= Joanna Morgan |last5=McDonald |first5=Matthew |last6=Mendoza-Cervantes |first6=Keren |last7=Pearson |first7=Zulmacristina F. |last8=Surendra |first8=Anusha |last9=Urrutia-Fucugauchi |first9=Jaime |last10=Vermeesch |first10=Peggy M. |last11=Warner |first11=Mike R. |display-authors=3 |date=February 2008 |title=Importance of pre-impact crustal structure for the asymmetry of the Chicxulub impact crater |url=http://www.nature.com/articles/ngeo103 |journal=Nature Geoscience |language=en |volume=1 |issue=2 |pages=131–135 |bibcode=2008NatGe...1..131G |doi=10.1038/ngeo103 |issn=1752-0894 |s2cid=128949260}}</ref> The seafloor rocks consisted of a sequence of [[Jurassic]]–[[Cretaceous]] marine sediments {{Convert|3|km|mi|sp=us}} thick. They were predominantly [[carbonate rock]], including [[Dolomite (rock)|dolomite]] (35–40% of total sequence) and [[limestone]] (25–30%), along with [[evaporite]]s ([[anhydrite]] 25–30%) and minor amounts of [[shale]] and [[sandstone]] (3–4%) underlain by approximately {{Convert|35|km|mi|sp=us}} of [[continental crust]], composed of [[Igneous rock|igneous]] [[Basement (geology)|crystalline basement]] including [[granite]].<ref>{{Cite journal |last1=Navarro |first1=Karina F. |last2=Urrutia-Fucugauchi |first2=Jaime |last3=Villagran-Muniz |first3=Mayo |last4=Sánchez-Aké |first4=Citlali |last5=Pi-Puig |first5=Teresa |last6=Pérez-Cruz |first6=Ligia |last7=Navarro-González |first7=Rafael |display-authors=3 |date=August 2020 |title=Emission spectra of a simulated Chicxulub impact-vapor plume at the Cretaceous–Paleogene boundary |url=https://linkinghub.elsevier.com/retrieve/pii/S0019103520301962 |journal=Icarus |language=en |volume=346 |pages=113813 |bibcode=2020Icar..34613813N |doi=10.1016/j.icarus.2020.113813 |s2cid=218965047 |access-date=February 19, 2022 |archive-date=May 22, 2023 |archive-url=https://web.archive.org/web/20230522063946/https://linkinghub.elsevier.com/retrieve/pii/S0019103520301962 |url-status=live }}</ref>

The impactor was around {{convert|10|km|mi||abbr=off|sp=us}} in diameter<ref name="Desch et al_2021">{{Cite journal |last1=Desch |first1=Steve |last2=Jackson |first2=Alan |last3=Noviello |first3=Jessica |last4=Anbar |first4=Ariel |date=June 1, 2021 |title=The Chicxulub impactor: comet or asteroid? |journal=Astronomy & Geophysics |language=en |volume=62 |issue=3 |pages=3.34–3.37 |arxiv=2105.08768 |doi=10.1093/astrogeo/atab069 |issn=1366-8781 |s2cid=234777761}}</ref>—large enough that, if set at sea level, it would have reached taller than [[Mount Everest]].<ref name="Alvarez_2008">{{Cite book |last=Alvarez |first=Walter |title=T. Rex and the Crater of Doom |publisher=Princeton University Press |year=2008 |isbn=978-0-691-13103-0}}</ref>{{rp|9}} The impactor's velocity was estimated at {{convert|20|km/s|sp=us}} inclined 45–60° to horizontal, impacting from the northeast.<ref name="collins">{{Cite journal |last1=Collins |first1=G. S. |last2=Patel |first2=N. |last3=Davison |first3=T. M. |last4=Rae |first4=A. S. P. |last5=Morgan |first5=J. V.|author5-link= Joanna Morgan |last6=Gulick |first6=S. P. S. |date=May 26, 2020 |title=A steeply-inclined trajectory for the Chicxulub impact |journal=Nature Communications |volume=11 |issue=1 |pages=1480 |bibcode=2020NatCo..11.1480C |doi=10.1038/s41467-020-15269-x |s2cid=218898524 |issn=2041-1723 |pmc=7251121 |pmid=32457325}}</ref> 

===Effects===
[[File:Chicxulub-animation.gif|thumb|An animation showing the Chicxulub impact and subsequent crater formation|alt=see caption]]
The [[kinetic energy]] of the impact was estimated at {{convert|72|TtTNT}}.<ref name="Richards">{{Cite journal |last1=Richards |first1=Mark A. |last2=Alvarez |first2=Walter |author-link2=Walter Alvarez |last3=Self |first3=Stephen |author-link3=Stephen Self |last4=Karlstrom |first4=Leif |last5=Renne |first5=Paul R. |author-link5=Paul Renne |last6=Manga |first6=Michael |author-link6=Michael Manga |last7=Sprain |first7=Courtney J. |last8=Smit |first8=Jan |author-link8=Jan Smit (paleontologist) |last9=Vanderkluysen |first9=Loÿc |last10=Gibson |first10=Sally A. |date=November 2015 |title=Triggering of the largest Deccan eruptions by the Chicxulub impact |url=https://seismo.berkeley.edu/~manga/richardsetal2015.pdf |url-status=live |journal=[[GSA Bulletin]] |volume=127 |issue=11–12 |pages=1507–1520 |bibcode=2015GSAB..127.1507R |doi=10.1130/B31167.1 |archive-url=https://web.archive.org/web/20240414192356/http://seismo.berkeley.edu/~manga/richardsetal2015.pdf |archive-date=2024-04-14 |access-date=August 10, 2024 |s2cid=3463018 |issn=0016-7606}}</ref> The impact generated winds in excess of {{convert|1000|km/h|sp=us}} near the blast's center,<ref>{{Cite web |title=Chicxulub Impact Event: Regional Effects |url=https://www.lpi.usra.edu/science/kring/Chicxulub/regional-effects/ |url-status=live |archive-url=https://web.archive.org/web/20190726023401/https://www.lpi.usra.edu/science/kring/Chicxulub/regional-effects/ |archive-date=July 26, 2019 |access-date=June 1, 2020 |website=Lunar and Planetary Institute}}</ref> and produced a transient cavity {{convert|100|km|sp=us}} wide and {{convert|30|km|sp=us}} deep that later collapsed. This formed a crater mainly under the sea and currently covered by ~{{convert|1000|m|sp=us}} of [[sediment]].<ref name="Gulick_etal_2013"/><ref name="Amos_2017-05-15">{{Cite web |last=Amos, Jonathan |date=May 15, 2017 |title=Dinosaur asteroid hit 'worst possible place' |url=https://www.bbc.com/news/science-environment-39922998 |url-status=live |archive-url=https://web.archive.org/web/20180318162335/http://www.bbc.com/news/science-environment-39922998 |archive-date=March 18, 2018 |access-date=August 19, 2017 |website=[[BBC News]] |department=Science and Environment}}</ref> The impact, expansion of water after filling the crater, and related [[seismic]] activity spawned [[megatsunami]]s over {{convert|100|m|sp=us}} tall, with one simulation suggesting the immediate waves from the impact may have reached up to {{convert|1.5|km|sp=us}} high.<ref name=":2" /><ref name="Bryant">{{Cite book |last=Bryant |first=Edward |url=https://books.google.com/books?id=tOkpBAAAQBAJ&pg=PA178 |title=Tsunami: The underrated hazard |date=June 2014 |publisher=Springer |isbn=978-3-319-06133-7 |page=178}}</ref> The waves scoured the [[seabed|sea floor]], leaving ripples underneath what is now [[Louisiana]] with average wavelengths of {{convert|600|m|sp=us}} and average wave heights of {{convert|16|m|sp=us}}, the largest ripples documented.<ref>{{Cite web |last=Koumoundouros |first=Tessa |date=July 14, 2021 |title=Fossilized Tsunami 'Megaripples' Reveal The Devastation From The Chicxulub Asteroid |url=https://www.sciencealert.com/tsunami-megaripples-from-the-dinosaur-killing-asteroid-impact-discovered-in-louisiana |access-date=January 1, 2022 |website=ScienceAlert |language=en-gb}}</ref><ref name="sciencedirect.com">{{Cite journal |last1=Kinsland |first1=Gary L. |last2=Egedahl |first2=Kaare |last3=Strong |first3=Martell Albert |last4=Ivy |first4=Robert |date=September 15, 2021 |title=Chicxulub impact tsunami megaripples in the subsurface of Louisiana: Imaged in petroleum industry seismic data |url=https://www.sciencedirect.com/science/article/pii/S0012821X21003186 |journal=Earth and Planetary Science Letters |language=en |volume=570 |pages=117063 |bibcode=2021E&PSL.57017063K |doi=10.1016/j.epsl.2021.117063 |issn=0012-821X |s2cid=237653482}}</ref> Material shifted by subsequent earthquakes and the waves reached to what are now [[Texas]] and Florida, and may have disturbed sediments as far as {{convert|6000|km|sp=us}} from the impact site.<ref name="Palmer_2016-02-25">{{Cite web |last=Palmer, Jane |date=February 25, 2016 |title=We Finally Know How Much the Dino-Killing Asteroid Reshaped Earth |url=http://www.smithsonianmag.com/science-nature/we-finally-know-how-much-dino-killing-asteroid-reshaped-earth-180958222/ |url-status=live |archive-url=https://web.archive.org/web/20160228025905/http://www.smithsonianmag.com/science-nature/we-finally-know-how-much-dino-killing-asteroid-reshaped-earth-180958222/ |archive-date=February 28, 2016 |access-date=February 26, 2016 |website=Smithsonian.com |publisher=[[Smithsonian Institution]]}}</ref><ref name=":2">{{Cite web |date=December 20, 2018 |title=Huge Global Tsunami Followed Dinosaur-Killing Asteroid Impact |url=https://eos.org/articles/huge-global-tsunami-followed-dinosaur-killing-asteroid-impact |url-status=live |archive-url=https://web.archive.org/web/20200711221446/https://eos.org/articles/huge-global-tsunami-followed-dinosaur-killing-asteroid-impact |archive-date=July 11, 2020 |access-date=July 11, 2020}}</ref><ref name="bundled_Kazuhisa et al">{{Cite journal|last1=Goto|first1=Kazuhisa|last2=Tada|first2=Ryuji|last3=Tajika|first3=Eiichi|last4=Bralower|first4=Timothy J.|last5=Hasegawa|first5=Takashi|last6=Matsui|first6=Takafumi|display-authors=3|year=2004|title=Evidence for ocean water invasion into the Chicxulub crater at the Cretaceous/Tertiary boundary|journal=Meteoritics & Planetary Science|language=en|volume=39|issue=8|pages=1233–1247|doi=10.1111/j.1945-5100.2004.tb00943.x|s2cid=55674339|bibcode=2004M&PS...39.1233G|issn=1945-5100|doi-access=free}}, {{Cite journal|url=https://agu.confex.com/agu/fm18/meetingapp.cgi/Paper/445502|title=The Chicxulub Impact Produced a Powerful Global Tsunami|first1=Molly M.|last1=Range|first2=SAND-Brian K.|last2=Arbic|first3=Brandon C.|last3=Johnson|first4=Theodore Carlton|last4=Moore|first5=Alistair|last5=Adcroft|first6=Joseph K.|last6=Ansong|first7=Jeroen|last7=Ritsema|first8=Christopher|last8=Scotese|display-authors=3|journal=AGU Fall Meeting Abstracts|date=December 14, 2018|volume=2018|publisher=AGU|bibcode=2018AGUFMPP53B..07R|via=agu.confex.com|access-date=July 11, 2020|archive-date=July 15, 2020|archive-url=https://web.archive.org/web/20200715022234/https://agu.confex.com/agu/fm18/meetingapp.cgi/Paper/445502|url-status=live}}, {{Cite web |last1=Matsui |first1=T. |last2=Imamura |first2=F. |last3=Tajika |first3=E. |last4=Nakano |first4=Y. |last5=Fujisawa |first5=Y. |year=2002 |title=Generation and propagation of a tsunami from the Cretaceous-Tertiary impact event |url=https://www.researchgate.net/publication/228783220 |url-status=live |archive-url=https://web.archive.org/web/20211020080538/https://www.researchgate.net/publication/228783220_Generation_and_propagation_of_a_tsunami_from_the_Cretaceous-Tertiary_impact_event |archive-date=October 20, 2021 |access-date=March 29, 2021 |website=Research Gate |publisher=Special Paper of the Geological Society of America 356 |pages=69–77}}</ref> The impact triggered a seismic event with an estimated [[Moment magnitude scale|moment magnitude]] of 9–11 {{M|w}}.<ref name="Richards"/>

A cloud of hot dust, ash and steam would have spread from the crater, with as much as 25 trillion metric tons of excavated material being ejected into the atmosphere by the blast. Some of this material escaped orbit, dispersing throughout the [[Solar System]],<ref name="newyorker_2019-03-29" /> while some of it fell back to Earth, vaporizing upon [[Atmospheric entry|re-entry]]. The rock heated Earth's surface and ignited wildfires, estimated to have enveloped nearly 70% of the planet's forests. The effect on living creatures even hundreds of kilometers away was immense, and much of present-day Mexico and the United States would have been devastated.<ref name="Bates_1992"/><ref name="Alvarez_2008" />{{rp|10–13}}<ref name="newyorker_2019-03-29" /> Fossil evidence for an instantaneous extinction of diverse animals was found in a soil layer only {{convert|10|cm|sp=us}} thick in [[New Jersey]], {{convert|2500|km|sp=us}} away from the impact site, indicating that death and burial under debris occurred suddenly and quickly over wide distances on nearby land.<ref name="Amos_2017-05-15" /> Field research from the [[Hell Creek Formation]] in North Dakota published in 2019 shows the simultaneous mass extinction of myriad species, combined with geological and atmospheric features that are consistent with the impact event.<ref name="newyorker_2019-03-29">{{Cite magazine |last=Preston |first=Douglas |author-link=Douglas Preston |date=March 29, 2019 |title=The Day The Dinosaurs Died |url=https://www.newyorker.com/magazine/2019/04/08/the-day-the-dinosaurs-died |url-status=live |magazine=[[The New Yorker]] |archive-url=https://web.archive.org/web/20190518000523/https://www.newyorker.com/magazine/2019/04/08/the-day-the-dinosaurs-died |archive-date=May 18, 2019 |access-date=May 13, 2019}}</ref>

Due to the relatively shallow water at the impact site, the rock that was vaporized included sulfur-rich [[gypsum]] from the lower part of the Cretaceous sequence, and this was injected into the atmosphere.<ref name="Amos_2017-05-15" /> This global dispersal of dust and [[sulfate]]s would have led to a sudden and catastrophic effect on the climate worldwide, instigating large temperature drops and devastating the [[food chain]]. Researchers stated that the impact not only generated an environmental calamity that extinguished life, but it also induced a vast subsurface [[Hydrothermal circulation|hydrothermal system]] that became an oasis for the recovery of life.<ref name="Kring_2017" /><ref>{{Cite journal |last1=Shaulis |first1=Barry J. |last2=Riller |first2=Ulrich |last3=Cockell |first3=Charles |last4=Coolen |first4=Marco J.L. |year=2017 |title=Probing the impact-generated hydrothermal system in the peak ring of the Chicxulub crater and its potential as a habitat |url=https://www.hou.usra.edu/meetings/lpsc2017/pdf/1212.pdf |journal=Lunar and Planetary Science |volume=XLVIII |issue=1964 |page=1212 |bibcode=2017LPI....48.1212K |archive-url=https://web.archive.org/web/20201026101301/https://www.hou.usra.edu/meetings/lpsc2017/pdf/1212.pdf |archive-date=October 26, 2020}}</ref> Using seismic images of the crater in 2008, scientists determined that the impactor landed in deeper water than previously assumed, which may have resulted in increased sulfate [[aerosol]]s in the atmosphere as a result of more water vapor being available to react with the vaporized [[anhydrite]]. This could have made the impact even deadlier by rapidly cooling the climate and generating [[acid rain]].<ref>{{Cite news |last=Airhart |first=Marc |date=January 1, 2008 |title=Seismic Images Show Dinosaur-Killing Meteor Made Bigger Splash |url=http://www.jsg.utexas.edu/news/2008/01/seismic-images-show-dinosaur-killing-meteor-made-bigger-splash/ |url-status=live |access-date=November 29, 2011 |archive-url=https://web.archive.org/web/20141220175132/http://www.jsg.utexas.edu/news/2008/01/seismic-images-show-dinosaur-killing-meteor-made-bigger-splash/ |archive-date=December 20, 2014}}</ref>

The emission of dust and particles could have covered the entire surface of Earth for several years, possibly up to a decade, creating a harsh environment for biological life. Production of [[carbon dioxide]] caused by the destruction of [[carbonate]] rocks would have led to a sudden [[greenhouse effect]].<ref name="Hildebrand et al_1991-09"/>{{rp|5}} For over a decade or longer, sunlight would have been blocked from reaching the surface of Earth by the dust particles in the atmosphere, cooling the surface dramatically. [[Photosynthesis]] by plants would also have been interrupted, affecting the entire food chain.<ref name="perlman_2007-09-06">{{Cite news |last=Perlman |first=David |author-link=David Perlman |date=September 6, 2007 |title=Scientists say they know where dinosaur-killing asteroid came from |url=http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2007/09/06/MNVFRUVCK.DTL |url-status=live |archive-url=https://web.archive.org/web/20120404030311/http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2007/09/06/MNVFRUVCK.DTL |archive-date=April 4, 2012 |access-date=October 3, 2007 |journal=[[San Francisco Chronicle]]}}</ref><ref>{{Cite journal |last1=Pope KO |last2=Ocampo AC |last3=Kinsland GL |last4=Smith R |year=1996 |title=Surface expression of the Chicxulub crater |journal=[[Geology (journal)|Geology]] |volume=24 |issue=6 |pages=527–530 |bibcode=1996Geo....24..527P |doi=10.1130/0091-7613(1996)024<0527:SEOTCC>2.3.CO;2 |pmid=11539331}}  See also [https://ntrs.nasa.gov/api/citations/19980211540/downloads/19980211540.pdf a similar 1998 report by the same group].</ref> A model of the event developed by Lomax et al (2001) suggests that [[Primary production#GPP and NPP|net primary productivity]] rates may have increased to higher than pre-impact levels over the long term because of the high carbon dioxide concentrations.<ref name="Lomax">{{Cite journal |last1=Lomax |first1=B. |last2=Beerling |first2=D. |author-link2=David Beerling |last3=Upchurch |first3=G. Jr. |last4=Otto-Bliesner |first4=B. |year=2001 |title=Rapid (10-yr) recovery of terrestrial productivity in a simulation study of the terminal Cretaceous impact event |journal=Earth and Planetary Science Letters |volume=192 |issue=2 |pages=137–144 |bibcode=2001E&PSL.192..137L |doi=10.1016/S0012-821X(01)00447-2 |s2cid=140196018}}</ref>

A long-term local effect of the impact was the creation of the Yucatán sedimentary basin which "ultimately produced favorable conditions for human settlement in a region where surface water is scarce".<ref>{{Cite conference |last=Winemiller |first=Terance L. |year=2007 |title=The Chicxulub meteor impact and ancient locational decisions on the Yucatán Peninsula, Mexico: The application of remote sensing, GIS, and GPS in settlement pattern Studies |url=http://www.asprs.org/a/publications/proceedings/tampa2007/0080.pdf |conference=ASPRS 2007 Annual Conference |publisher=[[American Society for Photogrammetry and Remote Sensing]] |archive-url=https://web.archive.org/web/20170810112923/http://asprs.org/a/publications/proceedings/tampa2007/0080.pdf |archive-date=August 10, 2017 |access-date=October 2, 2012 |place=Tampa, Florida |url-status=live}}</ref>

==Post-discovery investigations==
[[File:Chicxulub seismic & borehole map.png|thumb|Location of seismic surveys and boreholes|alt=see caption]]

===Geophysical data===
Two [[reflection seismology|seismic reflection]] datasets have been acquired over the offshore parts of the crater since its discovery. Older [[reflection seismology#2D versus 3D|2D seismic datasets]] have also been used that were originally acquired for hydrocarbon exploration. A set of three long-record 2D lines was acquired in October 1996, with a total length of {{convert|650|km|sp=us}}, by the [[BIRPS]] group. The longest of the lines, ''Chicx-A'', was shot parallel to the coast, while ''Chicx-B'' and ''Chicx-C'' were shot NW–SE and SSW–NNE respectively. In addition to the conventional seismic reflection imaging, data was recorded onshore to allow for [[Seismic wide-angle reflection and refraction|wide-angle refraction imaging]].<ref>{{Cite journal |last1=Morgan|first1= J.|author1-link= Joanna Morgan |last2=Warner|first2= M. |last3=Brittan|first3= J. |last4=Buffler|first4= R. |last5=Camargo|first5= A. |last6=Christeson|first6= G. |last7=Denton|first7= P. |last8=Hildebrand|first8= A. |last9=Hobbs|first9= R. |last10=Macintyre|first10= H.|last11= Mackenzie|first11= G.|last12= Maguire|first12= P.|last13= Marin|first13= L.|last14= Nakamura|first14= Y.|last15= Pilkington|first15= M.|last16=Sharpton|first16= V.|last17= Snyder|first17= D.|last18=Suarez|first18= G.|last19=Trejo|first19= A. |display-authors=3  |year=1997 |title=Size and morphology of the Chicxulub impact crater |url=https://www.researchgate.net/publication/232763118 |journal=Nature |volume=390 |issue=6659 |pages=472–476 |doi=10.1038/37291|bibcode=1997Natur.390..472M |s2cid=4398542 }}</ref><ref name="Snyder&Hobbs_1999">{{Cite book |title=Large Meteorite Impacts and Planetary Evolution II |last1=Snyder, D.B. |last2=Hobbs, R.W. |publisher=Geological Society of America |year=1999 |isbn=978-0-8137-2339-6 |editor-last=Dressler, B.O. |series=Special Publication |volume=339 |chapter=Deep seismic reflection profiles across the Chicxulub crater |editor-last2=Sharpton, V.L. |chapter-url=https://books.google.com/books?id=gV_H9cK94q8C&q=Chix&pg=PA263}}</ref>

In 2005, another set of profiles was acquired, bringing the total length of the 2D deep-penetration seismic data up to {{convert|2,470|km|sp=us}}. This survey also used [[ocean bottom seismometer]]s and land stations to allow [[seismic tomography|3D travel time inversion]] to improve the understanding of the velocity structure of the crater. The data was concentrated around the interpreted offshore peak ring to help identify possible drilling locations. At the same time, gravity data was acquired along {{convert|7638|km|sp=us}} of profiles. The acquisition was funded by the [[National Science Foundation]] (NSF), [[Natural Environment Research Council]] (NERC) with logistical assistance from the [[National Autonomous University of Mexico]] (UNAM) and the Centro de Investigación Científica de Yucatán (CICY – Yucatán Center for Scientific Investigation).<ref name="Gulick_etal_2013"/><ref name="Morgan_etal_2005">{{Cite journal |last1=Morgan |first1=J.|author1-link= Joanna Morgan |last2=Urrutia-Fucugauchi |first2=J. |last3=Gulick |first3=S. |last4=Christeson |first4=G. |last5=Barton |first5=P. |last6=Rebolledo-Vieyra |first6=M. |last7=Melosh |first7=J. |display-authors=3|year=2005 |title=Chicxulub Crater Seismic Survey prepares way for future drilling |journal=Eos |volume=86 |issue=36 |pages=325–328 |doi=10.1029/2005EO360001|bibcode=2005EOSTr..86..325M |doi-access=free }}</ref>

===Borehole drilling===
Intermittent [[core sample]]s from hydrocarbon exploration [[borehole]]s drilled by [[Pemex]] on the Yucatán peninsula have provided some useful data. UNAM drilled a series of eight fully-cored boreholes in 1995, three of which penetrated deep enough to reach the ejecta deposits outside the main crater rim (UNAM-5, 6, and 7). Between 2001 and 2002, a scientific borehole was drilled near the [[Yaxcopoil|Hacienda Yaxcopoil]], known as ''Yaxcopoil-1'' (or more commonly Yax-1), to a depth of {{convert|1511|m|sp=us}} below the surface, as part of the [[International Continental Scientific Drilling Program]]. The borehole was cored continuously, passing through {{convert|100|m|sp=us}} of impactites. Three fully-cored boreholes were also drilled by the [[Comisión Federal de Electricidad]] (Federal Electricity Commission) with UNAM. One of them, (BEV-4), was deep enough to reach the ejecta deposits.<ref>{{Cite web |last=Center for Lunar Science and Exploration |year=2019 |title=Classroom Illustrations: Chicxulub Crater |url=https://www.lpi.usra.edu/exploration/training/illustrations/chicxulub-crater/ |access-date=March 24, 2022}}; {{Cite journal |last1=Urrutia-Fucugauchi |first1=J. |last2=Chavez-Aguirre |first2=J.M. |last3=Pérez-Cruz |first3=L. |last4=De la Rosa |first4=J.L. |year=2008 |title=Impact ejecta and carbonate sequence in the eastern sector of the Chicxulub crater |journal=Comptes Rendus Geoscience |volume=340 |issue=12 |pages=801–810 |doi=10.1016/j.crte.2008.09.001|bibcode=2008CRGeo.340..801U |s2cid=129121808|url=https://comptes-rendus.academie-sciences.fr/geoscience/articles/10.1016/j.crte.2008.09.001/ }}</ref>

In 2016, a joint United Kingdom–United States team obtained the first offshore core samples from the peak ring in the central zone of the crater with the drilling of the borehole known as M0077A, part of Expedition 364 of the [[International Ocean Discovery Program]]. The borehole reached {{convert|1335|m|sp=us}} below the seafloor.<ref>{{Cite news |last=Amos |first=Jonathan |date=April 5, 2016 |title=Project to drill into 'dinosaur crater' gets under way |work=BBC News |url=https://www.bbc.com/news/science-environment-35950946 |url-status=live |access-date=April 5, 2016 |archive-url=https://web.archive.org/web/20160406072841/http://www.bbc.com/news/science-environment-35950946 |archive-date=April 6, 2016}}; {{cite news |last=Amos |first=Jonathan |url=https://www.bbc.com/news/science-environment-36377679 |title=Chicxulub 'dinosaur' crater drill project declared a success |work=BBC News |date=May 25, 2016 |access-date=May 25, 2016 |archive-date=May 28, 2016 |archive-url=https://web.archive.org/web/20160528081109/http://www.bbc.com/news/science-environment-36377679 |url-status=live }}</ref>

==Morphology==
[[File:Chicxulub schematic section.png|thumb|Schematic cross-section over the Chicxulub impact structure|alt=see caption]]
The form and structure ([[geomorphology]]) of the Chicxulub crater is known mainly from geophysical data. It has a well-defined concentric multi-ring structure. The outermost ring was identified using seismic reflection data. It is up to {{convert|130|km|sp=us}} from the crater center, and is a ring of [[normal fault]]s, throwing down towards the crater center, marking the outer limit of significant [[crust (geology)|crustal]] deformation. This makes it one of the three largest impact structures on Earth.<ref name="Morgan_etal_1997">{{Cite journal |last1=Morgan |first1=J.|author1-link= Joanna Morgan |last2=Warner |first2=M. |last3=the Chicxulub Working Group |last4=Brittan |first4=J. |last5=Buffler |first5=R. |last6=Camargo |first6=A. |last7=Christeson |first7=G. |last8=Denton |first8=P. |last9=Hildebrand |first9=A. |last10=Hobbs |first10=R. |last11=Macintyre |first11=H. |year=1997 |title=Size and morphology of the Chicxulub impact crater |s2cid=4398542|journal=Nature |volume=390 |pages=472–476 |doi=10.1038/37291 |last12=Mackenzie |first12=G. |last13=Maguire |first13=P. |last14=Marin |first14=L. |last15=Nakamura |first15=Y. |last16=Pilkington |first16=M. |last17=Sharpton |first17=V. |last18=Snyder |first18=D. |last19=Suarez |first19=G. |last20=Trejo |first20=A.|display-authors=3|issue=6659 |bibcode=1997Natur.390..472M }}</ref><ref name="Melosh_2001"/> Moving toward the center, the next ring is the main crater rim, also known as the "inner rim," which correlates with a ring of [[cenote]]s onshore and a major circular [[Bouguer anomaly|Bouguer gravity gradient anomaly]].<ref name="Gulick_etal_2008"/><ref name="Hildebrand_etal_1995">{{Cite journal |last1=Hildebrand |first1=A. |last2=Pilkington |first2=M. |last3=Conors |first3=M. |last4=Ortiz-Aleman |first4=C. |last5=Chavez |first5=R.E. |year=1995 |title=Size and structure of the Chicxulub crater revealed by horizontal gravity gradients and cenotes |journal=Nature |volume=376 |issue=6539 |pages=415–417 |doi=10.1038/376415a0|bibcode=1995Natur.376..415H |s2cid=4250257}}</ref> This ring has a radius that varies between {{convert|70|and|85|km|sp=us}}.<ref name="Gulick_etal_2013"/> The next inner ring structure is the peak ring. The area between the inner rim and peak ring is described as the "terrace zone", characterized by a series of [[fault block]]s defined by normal [[Fault (geology)|faults]] dipping towards the crater center, sometimes referred to as "slump blocks". The peak ring is about 80&nbsp;km in diameter and of variable height, {{convert|400|to|600|m|sp=us}} above the base of the crater in the west and northwest and {{convert|200|to|300|m|sp=us}} in the north, northeast, and east.<ref name="Gulick_etal_2013"/> The central part of the crater lies above a zone where the [[Earth's mantle|mantle]] was uplifted such that the [[Mohorovičić discontinuity]] is shallower by about {{convert|1|–|2|km|sp=us}} compared to regional values.<ref name="Gulick_etal_2013"/><ref name="Melosh_2001">{{Cite journal |last=Melosh |first=J. |year=2001 |title=Deep down at Chicxulub |journal=Nature |volume=414 |issue=6866 |pages=861–862 |doi=10.1038/414861a|pmid=11780048 |s2cid=33062203 }}</ref>

The ring structures are best developed to the south, west and northwest, becoming more indistinct towards the north and northeast of the structure. This is interpreted to be a result of variable water depth at the time of impact, with less well-defined rings resulting from the areas with water depths significantly deeper than {{convert|100|m|sp=us}}.<ref name="Gulick_etal_2008"/>

==Geology==

===Pre-impact geology===
[[File:Chicxulub Wharf Yucatan Mexico.jpg|thumb|alt=An image of a boardwalk over a body of water. A sign says "Chicxulub Puerto Mexico"| The center of the crater is near [[Chicxulub Puerto]].|right]]
[[File:Chicxulub Puerto.jpg|right|thumb|[[Stele|Stela]] in the main square of Chicxulub Puerto commemorating the impact]]
Before the impact, the geology of the [[Yucatán Platform|Yucatán area]], sometimes referred to as the "target rocks", consisted of a sequence of mainly Cretaceous limestones, overlying [[red bed]]s of uncertain age above an unconformity with the dominantly granitic [[basement (geology)|basement]]. The basement forms part of the [[Maya Block]] and information about its makeup and age in the Yucatán area has come only from drilling results around the Chicxulub crater and the analysis of basement material found as part of the ejecta at more distant K–Pg boundary sites. The Maya block is one of a group of crustal blocks found at the edge of the [[Gondwana]] continent. [[Zircon]] ages are consistent with the presence of an underlying [[Grenvillian orogeny|Grenville]] age crust, with large amounts of late [[Ediacaran]] [[Volcanic arc|arc]]-related [[igneous rock]]s, interpreted to have formed in the [[Pan-African orogeny]]. Late [[Paleozoic]] [[granitoid]]s (the distinctive "pink granite") were found in the peak ring borehole M0077A, with an estimated age of 326 ± 5 million years ago ([[Carboniferous]]). These have an [[adakite|adakitic]] composition and are interpreted to represent the effects of [[slab detachment]] during the [[Ouachita orogeny|Marathon-Ouachita orogeny]], part of the collision between [[Laurentia]] and Gondwana that created the [[Pangaea]] [[supercontinent]].<ref name="Zhao_etal_2020">{{Cite journal |last1=Zhao |first1=J. |last2=Xiao |first2=L. |last3=Gulick |first3=S.P.S. |last4=Morgan |first4=J.V.|author4-link= Joanna Morgan |last5=Kring |first5=D. |last6=Urrutia-Fucugauchi |first6=J. |last7=Schmeider |first7=M. |last8=de Graaf |first8=S.J. |last9=Wittmann |first9=A. |last10=Ross |first10=C.R. |last11=Claeys |first11=P. |last12=Pickersgill|first12=A.|last13=Kaskes|first13=P.|last14=Goderis|first14=S.|last15=Rasmussen|first15=C.|last16=Vajda|first16=V.|last17=Ferrière|first17=L.|last18=Fiegnon|first18=J.-G.|last19=Yamagucho|first19=K.|display-authors=3|year=2020 |title=Geochemistry, geochronology and petrogenesis of Maya Block granitoids and dykes from the Chicxulub Impact Crater, Gulf of México: Implications for the assembly of Pangea |journal=Gondwana Research |volume=82 |pages=128–150 |doi=10.1016/j.gr.2019.12.003|bibcode=2020GondR..82..128Z |s2cid= 214359672|url=https://biblio.vub.ac.be/vubirfiles/78237141/Zhao_etal_accepted.pdf }}</ref>

Red beds of variable thickness, up to {{convert|115|m|sp=us}}, overlay the granitic basement, particularly in the southern part of the area. These continental [[clastic rock]]s are thought to be of [[Triassic]]-to-Jurassic age, although they may extend into the [[Lower Cretaceous]]. The lower part of the Lower Cretaceous sequence consists of [[Dolomite (rock)|dolomite]] with interbedded anhydrite and gypsum, with the upper part being limestone, with dolomite and anhydrite in part. The thickness of the Lower Cretaceous varies from {{convert|750|m|sp=us}} up to {{convert|1675|m|sp=us}} in the boreholes. The [[Upper Cretaceous]] sequence is mainly platform limestone, with [[marl]] and interbedded anhydrite. It varies in thickness from {{convert|600|m|sp=us}} up to {{convert|1200|m|sp=us}}. There is evidence for a Cretaceous basin within the Yucatán area that has been named the Yucatán Trough, running approximately south–north, widening northwards, explaining the observed thickness variations.<ref name="Guzman_Hidalgo_etal_2021">{{Cite journal |last1=Guzmán-Hidalgo |first1=E. |last2=Grajales-Nishimura |first2=J.M. |last3=Eberli |first3=G.P. |last4=Aguayo-Camargo |first4=J.E. |last5=Urrutia-Fucugauchi |first5=J. |last6=Pérez-Cruze |first6=L. |display-authors=3|year=2021 |title=Seismic stratigraphic evidence of a pre-impact basin in the Yucatán Platform: morphology of the Chicxulub crater and K/Pg boundary deposits |journal=Marine Geology |volume=441 |page=106594 |doi=10.1016/j.margeo.2021.106594|bibcode=2021MGeol.44106594G |s2cid=238783773}}</ref>

===Impact rocks===
The most common observed [[impactite|impact rocks]] are [[suevite]]s, found in many of the boreholes drilled around the Chicxulub crater. Most of the suevites were resedimented soon after the impact by the resurgence of oceanic water into the crater. This gave rise to a layer of suevite extending from the inner part of the crater out as far as the outer rim.<ref name="Kaskes_etal_2022">{{Cite journal |last1=Kaskes |first1=P. |last2=de Graaf |first2=S.J. |last3=Feignon |first3=J.-G. |last4=Déhais |first4=T. |last5=Goderis |first5=S. |last6=Ferrière |first6=LO. |last7=Koeberl |first7=C. |last8=Smit |first8=J. |last9=Wittmann |first9=A. |last10=Gulick |first10=S.P.S. |last11=Debaille |first11=V. |last12=Mattielli|first12=N.|last13=Claeys|first13=P.|display-authors=3|year=2022 |title=Formation of the crater suevite sequence from the Chicxulub peak ring: A petrographic, geochemical, and sedimentological characterization |journal=GSA Bulletin |volume=134 |issue=3–4 |pages=895–927 |doi=10.1130/B36020.1|bibcode=2022GSAB..134..895K |s2cid=237762081|url=https://biblio.vub.ac.be/vubirfiles/72890608/b36020.pdf }}</ref>

Impact melt rocks are thought to fill the central part of the crater, with a maximum thickness of {{convert|3|km|sp=us}}. The samples of melt rock that have been studied have overall compositions similar to that of the basement rocks, with some indications of mixing with carbonate source, presumed to be derived from the Cretaceous carbonates. An analysis of melt rocks sampled by the M0077A borehole indicates two types of melt rock, an upper impact melt (UIM), which has a clear carbonate component as shown by its overall chemistry and the presence of rare limestone clasts and a lower impact melt-bearing unit (LIMB) that lacks any carbonate component. The difference between the two impact melts is interpreted to be a result of the upper part of the initial impact melt, represented by the LIMB in the borehole, becoming mixed with materials from the shallow part of the crust either falling back into the crater or being brought back by the resurgence forming the UIM.<ref name="de Graaf_etal_2022">{{Cite journal |last1=de Graaf |first1=S.J. |last2=Kaskes |first2=P. |last3=Déhais |first3=T. |last4=Goderis |first4=S. |last5=Debaille |first5=V. |last6=Ross |first6=C.H. |last7=Gulick |first7=S.P.S. |last8=Feignon |first8=J.-G. |last9=Ferrière |first9=L. |last10=Koeberi |first10=C. |last11=Smit |first11=J. |last12=Mattielli |first12=N. |last13=Claeys |first13=P. |display-authors=3 |year=2022 |title=New insights into the formation and emplacement of impact melt rocks within the Chicxulub impact structure, following the 2016 IODP-ICDP Expedition 364 |journal=GSA Bulletin |volume=134 |issue=1–2 |pages=293–315 |doi=10.1130/B35795.1 |bibcode=2022GSAB..134..293D |s2cid=236541913 |url=https://biblio.vub.ac.be/vubirfiles/79061460/deGraaff_ImpactMelt_GSA_B_Manuscript_v3_MasterFile_Clean.pdf |access-date=May 18, 2022 |archive-date=May 18, 2022 |archive-url=https://web.archive.org/web/20220518033352/https://biblio.vub.ac.be/vubirfiles/79061460/deGraaff_ImpactMelt_GSA_B_Manuscript_v3_MasterFile_Clean.pdf |url-status=live }}</ref>

The "pink granite", a granitoid rich in [[alkali feldspar]] found in the peak ring borehole shows many deformation features that record the extreme strains associated with the formation of the crater and the subsequent development of the peak ring.<ref name="Kring_2017" /><ref>{{cite news|last1=St. Fleur|first1=Nicholas|title=Drilling into the Chicxulub Crater, Ground Zero of the Dinosaur Extinction|url=https://www.nytimes.com/2016/11/18/science/chicxulub-crater-dinosaur-extinction.html|newspaper=The New York Times|date=November 17, 2016|access-date=March 1, 2017|archive-date=November 19, 2016|archive-url=https://web.archive.org/web/20161119200501/http://www.nytimes.com/2016/11/18/science/chicxulub-crater-dinosaur-extinction.html?_r=0|url-status=live}}</ref> The granitoid has an unusually low density and [[P-wave]] velocity compared to typical granitic basement rocks. Study of the core from M0077A shows the following deformation features in apparent order of development: pervasive fracturing along and through grain boundaries, a high density of [[shear fault]]s, bands of [[cataclasite]] and ultra-cataclasite and some [[shear zone|ductile shear structures]]. This deformation sequence is interpreted to result from initial crater formation involving [[acoustic fluidization]] followed by shear faulting with the development of cataclasites with [[fault zone]]s containing impact melts.<ref name="Riller_etal_2018">{{Cite journal |last1=Riller |first1=U. |last2=Poelchau |first2=M.H. |last3=Rae |first3=A.S.P. |last4=Schulte |first4=F.M. |last5=Collins |first5=G.S. |last6=Melish |first6=H.J. |last7=Grieve |first7=R.A.F. |last8=Morgan |first8=J.V.|author8-link= Joanna Morgan |last9=Gulick |first9=S.P. |last10=Lofi |first10=J. |last11=Diaw |first11=A. |last12=McCall|first12=N.|last13=Kring|first13=D.A.|last14=((IODP–ICDP Expedition 364 Science Party))|display-authors=3|year=2018 |title=Rock fluidization during peak-ring formation of large impact structures |journal=Nature |volume=562 |issue=7728 |pages=511–518 |doi=10.1038/s41586-018-0607-z|pmid=30356184 |bibcode=2018Natur.562..511R |s2cid=53026325|url=http://eprints.gla.ac.uk/173925/1/173925.pdf }}</ref>

The peak ring drilling below the sea floor also discovered evidence of a massive hydrothermal system, which modified approximately {{nowrap|1.4 × 10<sup>5</sup> km<sup>3</sup>}} of Earth's crust and lasted for hundreds of thousands of years. These hydrothermal systems may provide support for the impact origin of life hypothesis for the [[Hadean]] eon,<ref>{{cite journal<!--|authors=David A. Kring; Sonia M. Tikoo; Martin Schmieder1; Ulrich Riller; Mario Rebolledo-Vieyra; Sarah L. Simpson; Gordon R. Osinski; Jérôme Gattacceca; Axel Wittmann; Christina M. Verhagen; Charles S. Cockell; Marco J.L. Coolen; Fred J. Longstaffe; Sean P. S. Gulick; [[Joanna Morgan|Joanna V. Morgan]]; Timothy J. Bralower; Elise Chenot; Gail L. Christeson; Philippe Claeys; Ludovic Ferrière; Catalina Gebhardt; Kazuhisa Goto; Sophie L. Green; Heather Jones; Johanna Lofi; Christopher M. Lowery; Rubén Ocampo-Torres; Ligia Perez-Cruz; Annemarie E. Pickersgill; Michael H. Poelchau; Auriol S.P. Rae11; Cornelia Rasmussen; Honami Sato; Jan Smit; Naotaka Tomioka; Jaime Urrutia-Fucugauchi; Michael T. Whalen; Long Xiao and Kosei E. Yamaguchi-->|last1=Kring |first1=David |first2=Sonia M. |last2=Tikoo |first3=Martin |last3=Schmieder |display-authors=etal|title=Probing the hydrothermal system of the Chicxulub impact crater|journal=Science Advances |year=2020|volume=6|issue=22|doi=10.1126/sciadv.aaz3053|s2cid=219244669}}</ref> when the entire surface of Earth was affected by impactors much larger than the Chicxulub impactor.<ref>{{cite journal |first2= W.F. |last2=Bottke |first3=L.T. |last3=Elkins-Tanton |first4=M. |last4=Bierhaus|first5= K. |last5=Wuennemann|first6=A. |last6=Morbidelli |first7=D.A. |last7=Kring|last1=Marchi |first1=S. |display-authors=3|title=Widespread mixing and burial of Earth's Hadean crust by asteroid impacts|journal=Nature|year=2014|volume=511|issue=7511 |pages=578–582|doi=10.1038/nature13539|pmid=25079556 |bibcode=2014Natur.511..578M |s2cid=205239647}}</ref>

===Post-impact geology===
After the immediate effects of the impact had stopped, [[sedimentation]] in the Chicxulub area returned to the shallow water platform carbonate [[depositional environment]] that characterised it before the impact. The sequence, which dates back as far as the [[Paleocene]], consists of [[marl]] and limestone, reaching a thickness of about {{convert|1000|m|abbr=on}}.<ref name="Hildebrand et al_1991-09" />{{rp|3}} The K–Pg boundary inside the crater is significantly deeper than in the surrounding area.<ref name="Hildebrand et al_1991-09" />{{rp|4}}

On the Yucatán peninsula, the inner rim of the crater is marked by clusters of cenotes,<ref>{{cite magazine |url=https://www.youtube.com/watch?v=dNRTtLLuNM8 |type=video |title=Meteor impact site |series=Earth: The biography |magazine=National Geographic |date=July 11, 2008 |access-date=August 19, 2015 |archive-date=October 17, 2015 |archive-url=https://web.archive.org/web/20151017002003/https://www.youtube.com/watch?v=dNRTtLLuNM8 |url-status=live }}</ref> which are the surface expression of a zone of preferential groundwater flow, moving water from a recharge zone in the south to the coast through a [[karst]]ic [[aquifer]] system.<ref name="Hildebrand et al_1991-09" />{{rp|4}}<ref name="Pérez-Ceballos_etal_2021">{{Cite journal |last1=Pérez-Ceballos |first1=R. |last2=Canul-Macario |first2=C. |last3=Pacheco-Castro |first3=R. |last4=Pacheco-Ávila |first4=J. |last5=Euán-Ávila  |first5=J. |last6=Merino-Ibarra  |first6=M. |display-authors=3|year=2021 |title=Regional Hydrogeochemical Evolution of Groundwater in the Ring of Cenotes, Yucatán (Mexico): An Inverse Modelling Approach |journal=Water |volume=13 |issue=5 |page=614 |doi=10.3390/w13050614 |doi-access=free }}</ref> From the cenote locations, the karstic aquifer is clearly related to the underlying crater rim,<ref>{{cite web|author=Kring, David A.|work=lpl.arizona.edu|url=http://www.lpl.arizona.edu/SIC/impact_cratering/Chicxulub/Discovering_crater.html|title=Discovering the Crater|access-date=October 12, 2007|archive-url=https://web.archive.org/web/20071010021337/http://www.lpl.arizona.edu/SIC/impact_cratering/Chicxulub/Discovering_crater.html|archive-date=October 10, 2007}}</ref> possibly through higher levels of fracturing,
caused by [[Compaction (geology)#Differential compaction|differential compaction]].<ref name="Hildebrand_etal_1998">{{Cite book |last1=Hildebrand |first1=A.R.|last2=Pilkington|first2=M.|last3=Ortiz-Aleman|first3=C.|last4=Chavez|first4=R.E.|last5=Urrutia-Fucugauchi|first5=J.|last6=Connors|first6=M.|last7=Graniel-Castro|first7=E.|last8=Camara-Zi|first8=A.|last9=Halfpenny|first9=J.F.|last10=Niehaus|first10=D. |title=Meteorites: Flux with Time and Impact Effects |publisher=Geological Society |year=1998 |isbn=9781862390171 |display-authors=3|editor-last=Grady |editor-first=M.M. |series=Special Publications |volume=140 |publication-place=London |pages=160 |chapter=Mapping Chicxulub crater structure with gravity and seismic reflection data |doi=10.1144/GSL.SP.1998.140.01.12 |s2cid=130177601 |editor-last2=Hutchinson |editor-first2=R. |editor-last3=McCall |editor-first3=G.J.H. |editor-last4=Rothery |editor-first4=D.A.}}</ref>

==Astronomical origin and type of impactor==
There is broad consensus that the Chicxulub impactor was a [[C-type asteroid]] with a [[carbonaceous chondrite]]–like composition, rather than a [[comet]].<ref name="Desch et al_2021" /><ref name=":0" /> These types of asteroids originally formed in the outer Solar System, beyond the orbit of [[Jupiter]].<ref name=":0">{{Cite journal |last1=Fischer-Gödde |first1=Mario |last2=Tusch |first2=Jonas |last3=Goderis |first3=Steven |last4=Bragagni |first4=Alessandro |last5=Mohr-Westheide |first5=Tanja |last6=Messling |first6=Nils |last7=Elfers |first7=Bo-Magnus |last8=Schmitz |first8=Birger |last9=Reimold |first9=Wolf U. |last10=Maier |first10=Wolfgang D. |last11=Claeys |first11=Philippe |last12=Koeberl |first12=Christian |last13=Tissot |first13=François L.H. |last14=Bizzarro |first14=Martin |last15=Münker |first15=Carsten |date=2024-08-16 |title=Ruthenium isotopes show the Chicxulub impactor was a carbonaceous-type asteroid |url=https://www.science.org/doi/10.1126/science.adk4868 |journal=Science |language=en |volume=385 |issue=6710 |pages=752–756 |doi=10.1126/science.adk4868 |pmid=39146402 |issn=0036-8075 |access-date=August 15, 2024 |archive-date=August 15, 2024 |archive-url=https://web.archive.org/web/20240815223354/https://www.science.org/doi/10.1126/science.adk4868 |url-status=live }}</ref> In 1998, a meteorite, approximately {{convert|2.5|mm|sp=us|adj=|frac=16}} across, was described from a deep sea [[sediment core]] from the North Pacific, from a sediment sequence spanning the Cretaceous–Paleogene boundary (when the site was located in the central Pacific), with the meteorite being found at the base of the K-Pg boundary iridium anomaly within the sediment core. The meteorite was suggested to represent a fragment of the Chicxulub impactor. Analysis suggested that it best fitted the criteria of the [[CV chondrite|CV]], [[CO chondrite|CO]] and [[CR chondrite|CR]] groups of carbonaceous chondrites.<ref>{{Cite journal |last=Kyte |first=Frank T. |date=November 1998 |title=A meteorite from the Cretaceous/Tertiary boundary |url=http://www.nature.com/articles/24322 |url-status=live |journal=Nature |language=en |volume=396 |issue=6708 |pages=237–239 |bibcode=1998Natur.396..237K |doi=10.1038/24322 |issn=0028-0836 |s2cid=4381596 |archive-url=https://web.archive.org/web/20210520071110/https://www.nature.com/articles/24322 |archive-date=May 20, 2021 |access-date=June 7, 2021}}</ref> A 2021 paper suggested, based on geochemical evidence including the excess of [[Isotopes of chromium|chromium isotope]] <sup>54</sup>Cr and the ratios of [[Platinum group|platinum group metals]] found in marine impact layers, that the impactor matched the characteristics of [[CM chondrite|CM]] or CR carbonaceous chondrites.<ref name="Desch et al_2021" /> [[Ruthenium]] isotope ratios found in impact layers also support a carbonaceous chondrite composition for the impactor.<ref name=":0" />

A 2007 ''[[Nature (journal)|Nature]]'' report proposed a specific astronomical origin for the Chicxulub asteroid.<ref name="perlman_2007-09-06" /> The authors, [[William F. Bottke]], David Vokrouhlický, and [[David Nesvorný]], argued that a collision in the asteroid belt 160 million years ago between a {{cvt|170|km}} diameter parent body and another {{cvt|60|km}} diameter body resulted in the [[Baptistina family]] of asteroids, the largest surviving member of which is [[298 Baptistina]]. They proposed that the Chicxulub asteroid was also a member of this group.<ref>{{cite journal|url=http://www.boulder.swri.edu/~bottke/Reprints/Bottke_2007_Nature_449_48_Baptistina_KT.pdf|title=An asteroid breakup 160 Myr ago as the probable source of the K/T impactor|date=September 2007|journal=[[Nature (journal)|Nature]]|author=Bottke, W.F.|author2=Vokrouhlicky, D.|author3=Nesvorny, D.|access-date=October 3, 2007|volume=449|pages=23–25|doi=10.1038/nature06070|pmid=17805288|issue=7158|bibcode=2007Natur.449...48B|s2cid=4322622|archive-date=April 24, 2020|archive-url=https://web.archive.org/web/20200424184913/https://www.boulder.swri.edu/~bottke/Reprints/Bottke_2007_Nature_449_48_Baptistina_KT.pdf|url-status=live}}; {{Cite web |last=Ingham, Richard |date=September 5, 2007 |title=Traced: The asteroid breakup that wiped out the dinosaurs |url=http://afp.google.com/article/ALeqM5jz3TGi2zcsmdYQDxwbdCwq2kanMA |url-status=dead |archive-url=https://web.archive.org/web/20071114031858/http://afp.google.com/article/ALeqM5jz3TGi2zcsmdYQDxwbdCwq2kanMA |archive-date=November 14, 2007 |access-date=September 27, 2007 |agency=Agence France-Presse}}</ref> Subsequent evidence has disproven this theory. A 2009 spectrographic analysis revealed that 298 Baptistina has a different composition more typical of an [[S-type asteroid]] than the presumed carbonaceous chondrite composition of the Chicxulub impactor.<ref>{{Cite journal |last1=Reddy |first1=Vishnu |last2=Emery |first2=Joshua P. |last3=Gaffey |first3=Michael J. |last4=Bottke |first4=William F. |last5=Cramer |first5=Abigail |last6=Kelley |first6=Michael S. |display-authors=3 |date=December 2009 |title=Composition of 298 Baptistina: Implications for the K/T impactor link |journal=Meteoritics & Planetary Science |language=en |volume=44 |issue=12 |pages=1917–1927 |bibcode=2009M&PS...44.1917R |doi=10.1111/j.1945-5100.2009.tb02001.x |s2cid=39644763|doi-access=free }}</ref> In 2011, data from the [[Wide-field Infrared Survey Explorer]] revised the date of the collision which created the Baptistina family to about 80 million years ago, allowing only 15 million years for the process of [[Orbital resonance|resonance]] and collision, which takes many tens of millions of years.<ref>{{Cite journal |last1=Masiero |first1=Joseph R. |last2=Mainzer |first2=A.K. |last3=Grav |first3=T. |last4=Bauer |first4=J.M. |last5=Cutri |first5=R.M. |last6=Dailey |first6=J. |last7=Eisenhardt |first7=P.R.M. |last8=McMillan |first8=R.S. |last9=Spahr |first9=T.B. |last10=Skrutskie |first10=M.F. |last11=Tholen |first11=D. |display-authors=3 |date=November 10, 2011 |title=Main belt asteroids with WISE / NEOWISE. I. Preliminary albedos and diameters |url=https://iopscience.iop.org/article/10.1088/0004-637X/741/2/68 |journal=The Astrophysical Journal |volume=741 |issue=2 |pages=68 |arxiv=1109.4096 |bibcode=2011ApJ...741...68M |doi=10.1088/0004-637X/741/2/68 |issn=0004-637X |s2cid=118745497 |access-date=July 17, 2022 |archive-date=January 16, 2022 |archive-url=https://web.archive.org/web/20220116201153/https://iopscience.iop.org/article/10.1088/0004-637X/741/2/68 |url-status=live }}</ref> In 2010, another hypothesis implicated the newly discovered asteroid [[354P/LINEAR]], a member of the [[Flora family]], as a possible remnant cohort of the K–Pg impactor.<ref>{{Cite web |date=February 2, 2010 |title=Smashed asteroids may be related to dinosaur killer |url=https://www.reuters.com/article/us-space-asteroid-idUSTRE61154120100202 |url-status=live |archive-url=https://web.archive.org/web/20191004074906/https://www.reuters.com/article/us-space-asteroid-idUSTRE61154120100202 |archive-date=October 4, 2019 |access-date=July 5, 2021 |work=Reuters}}</ref> In 2021, a numerical simulation study argued that the impactor likely originated in the outer main part of the [[asteroid belt]].<ref>{{Cite journal |last1=Nesvorný |first1=David |last2=Bottke |first2=William F. |last3=Marchi |first3=Simone |date=November 1, 2021 |title=Dark primitive asteroids account for a large share of K/Pg-scale impacts on the Earth |journal=Icarus |language=en |volume=368 |pages=114621 |arxiv=2107.03458 |bibcode=2021Icar..36814621N |doi=10.1016/j.icarus.2021.114621 |issn=0019-1035 |s2cid=235765478}}</ref>

Some scholars have argued that the impactor was a [[comet]], not an asteroid. Two papers in 1984 proposed it to be a comet originating from the [[Oort cloud]], and it was proposed in 1992 that [[Disrupted planet|tidal disruption]] of comets could potentially increase impact rates.<ref name="Desch et al_2021" /> In 2021, [[Avi Loeb]] and a colleague suggested in ''[[Scientific Reports]]'' that the impactor was a fragment from a disrupted comet.<ref name="NYT-20210215">{{Cite news |last=Ferreira |first=Becky |date=February 15, 2021 |title=Where Did the Dinosaur-Killing Impactor Come From? – A new study blames a comet fragment for the death of the dinosaurs 66 million years ago. But most experts maintain that an asteroid caused this cataclysmic event. |work=[[The New York Times]] |url=https://www.nytimes.com/2021/02/15/science/dinosaur-extinction-kt-comet-asteroid.html |url-status=live |access-date=February 15, 2021 |archive-url=https://web.archive.org/web/20210215200655/https://www.nytimes.com/2021/02/15/science/dinosaur-extinction-kt-comet-asteroid.html |archive-date=February 15, 2021}}; {{Cite journal |last=Siraj |first=Amir |date=February 15, 2021 |title=Breakup of a long-period comet as the origin of the dinosaur extinction |journal=[[Scientific Reports]] |volume=11 |page=3803 |arxiv=2102.06785 |bibcode=2021NatSR..11.3803S |doi=10.1038/s41598-021-82320-2 |pmc=7884440 |pmid=33589634 |doi-access=free |number=3803}}</ref> A rebuttal in ''[[Astronomy & Geophysics]]'' countered that Loeb ''et al''. had ignored that the amount of iridium deposited around the globe, {{cvt|2.0e8|-|2.8e8|kg}}, was too large for a comet of the size implied by the crater, and that they had overestimated likely comet impact rates. They concluded that all available evidence strongly favors an asteroid impactor, effectively ruling out a comet.<ref name="Desch et al_2021" /> Ruthenium isotope ratios in impact layers also strongly support an asteroid rather than a comet nature for the impactor.<ref name=":0" />

== See also ==
* [[Timeline of Cretaceous–Paleogene extinction event research]]
* [[Tenejapa-Lacandón Formation]]
* [[Nadir crater]]
* [[List of impact structures on Earth]]
* [[List of possible impact structures on Earth]]
* [[Barberton Greenstone Belt]]
* [[Permian–Triassic extinction event]]

== References ==
{{Reflist|refs=

<ref name="Bates_1992">{{Cite AV media |url=http://imdb.com/title/tt0103400 |title=The Dinosaurs! Episode 4: "Death of the Dinosaur" |type=TV-series |publisher=PBS Video, [[WHYY-TV]] |year=1992 |people=Bates, Robin (series producer); Chesmar, Terri and Baniewicz, Rich (associate producers); [[Robert Bakker|Bakker, Robert T.]]; Hildebrand, Alan; [[H. Jay Melosh|Melosh, Gene]]; Moras, Florentine; Penfield, Glen (interviewees) |access-date=September 25, 2007 |archive-date=September 18, 2024 |archive-url=https://web.archive.org/web/20240918010428/https://www.imdb.com/title/tt0103400/ |url-status=live }}</ref>

<ref name="Hildebrand et al_1991-09">{{Cite journal |last1=Hildebrand |first1=Alan R. |last2=Penfield |first2=Glen T. |last3=Kring |first3=David A. |last4=Pilkington |first4=Mark |last5=Zanoguera |first5=Antonio Camargo |last6=Jacobsen |first6=Stein B. |last7=Boynton |first7=William V. |display-authors=3 |date=September 1991 |title=Chicxulub Crater; a possible Cretaceous/Tertiary boundary impact crater on the Yucatan Peninsula, Mexico |journal=[[Geology (journal)|Geology]] |volume=19 |issue=9 |pages=867–871 |bibcode=1991Geo....19..867H |doi=10.1130/0091-7613(1991)019<0867:CCAPCT>2.3.CO;2}}</ref>

<ref name="Kring_2017">{{Cite magazine |last1=Kring |first1=David A |last2=Claeys |first2=Philippe |last3=Gulick |first3=Sean P.S. |last4=Morgan |first4=Joanna V.|author4-link= Joanna Morgan |last5=Collins |first5=Gareth S. |date=October 10, 2017 |title=Chicxulub and the Exploration of Large Peak-Ring Impact Craters through Scientific Drilling |url=https://www.geosociety.org/gsatoday/science/G352A/GSATG352A.pdf |magazine=GSA Today |publisher=The Geological Society of America |issn=1052-5173 |access-date=February 1, 2022 |archiveurl=https://web.archive.org/web/20171010155225/https://www.geosociety.org/gsatoday/science/G352A/GSATG352A.pdf |archivedate=October 10, 2017}}</ref>

<ref name="Smit and Hertogen-1980">{{cite journal |last1=Smit |first1=Jan |last2=Hertogen |first2=Jan |title=An extraterrestrial event at the Cretaceous-tertiary boundary |journal=Nature |date=1980 |volume=285 |issue=5762 |pages=198–200 |doi=10.1038/285198a0 |bibcode=1980Natur.285..198S |s2cid=4339429 |url=https://www.nature.com/articles/285198a0 |access-date=March 5, 2024 |archive-date=May 4, 2023 |archive-url=https://web.archive.org/web/20230504002910/https://www.nature.com/articles/285198a0 |url-status=live }}</ref>

<ref name="Verschuur_1996">{{Cite book |last=Verschuur |first=Gerrit L. |title=Impact!: The Threat of Comets and Asteroids |date=1996 |publisher=Oxford University Press (U.S.) |isbn=978-0-19-511919-0 |author-link=Gerrit Verschuur}}</ref>

<ref name="Weinreb_2002">{{cite journal |last1=Weinreb |first1=David B. |title=Catastrophic Events in the History of Life: Toward a New Understanding of Mass Extinctions in the Fossil Record&nbsp;– Part I |journal=Journal of Young Investigators |date=March 2002 |volume=5 |issue=6 |url=https://www.jyi.org/2002-march/2017/10/23/catastrophic-events-in-the-history-of-life-toward-a-new-understanding-of-mass-extinctions-in-the-fossil-record-part-i |access-date=27 July 2024 |issn=1539-4026 |archive-date=September 18, 2024 |archive-url=https://web.archive.org/web/20240918010420/https://www.jyi.org/2002-march/2017/10/23/catastrophic-events-in-the-history-of-life-toward-a-new-understanding-of-mass-extinctions-in-the-fossil-record-part-i |url-status=live }}</ref>

}}
* {{Cite news |last=Kornel |first=Katherine |date=September 10, 2019 |title=A New Timeline of the Day the Dinosaurs Began to Die Out – By drilling into the Chicxulub crater, scientists assembled a record of what happened just after the asteroid impact |work=[[The New York Times]] |url=https://www.nytimes.com/2019/09/10/science/chicxulub-asteroid-impact-dinosaurs.html |url-status=live |access-date=September 25, 2019 |archive-url=https://web.archive.org/web/20190925002058/https://www.nytimes.com/2019/09/10/science/chicxulub-asteroid-impact-dinosaurs.html |archive-date=September 25, 2019}}

== External links ==
{{Commons category}}
* [http://www.chicxulubcrater.org Chicxulub Crater] {{Webarchive|url=https://web.archive.org/web/20180722035405/http://www.chicxulubcrater.org/ |date=July 22, 2018 }}
* [http://www.lpi.usra.edu/publications/slidesets/craters/slide_37.html Chicxulub: Variations in the magnitude of the gravity field at sea level image] (Lunar and Planetary Institute, USRA)
* [http://www.scientificamerican.com/article.cfm?id=doubts-on-dinosaurs "Doubts on Dinosaurs"] – ''[[Scientific American]]'' (paywalled)
* [https://gsa.confex.com/gsa/2017AM/webprogram/Session43180.html Papers and presentations resulting from the 2016 Chicxulub drilling project]

{{KT_boundary|K–Pg boundary}}
{{Impact cratering on Earth}}

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{{DEFAULTSORT:Chicxulub Crater}}
[[Category:Cretaceous–Paleogene boundary|+]]
[[Category:Cretaceous impact craters]]
[[Category:Extinction events]]
[[Category:Impact craters of Mexico]]
[[Category:Mérida, Yucatán]]
[[Category:Natural history of the Caribbean]]
[[Category:Natural history of the Yucatán Peninsula]]
[[Category:Oceans]]
[[Category:Dinosaurs]]