Old page wikitext, before the edit (old_wikitext) | '[[Image:Yucatan chix crater.jpg|thumb|300px|Imaging from [[NASA]]'s Shuttle Radar Topography Mission [[STS-99]] reveals part of the 180 kilometer (112 mi) diameter ring of the crater; clustered around the crater's trough are numerous [[sinkhole]]s, suggesting a prehistoric [[oceanic basin]] in the depression left by the impact.<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|work=[[Shuttle Radar Topography Mission]]|publisher=[[NASA]]|accessdate=28 October 2010}}</ref>]]
The '''Chicxulub crater''' ({{IPAc-en|icon|ˈ|tʃ|iː|k|ʃ|ə|l|uː|b}} {{respell|CHEEK|shə-loob}}; {{IPA-myn|tʃʼikʃuluɓ|[[Yucatec Maya language|Maya]]:}}) is an ancient [[impact crater]] buried underneath the [[Yucatán Peninsula]] in [[Mexico]].<ref>{{Cite Earth Impact DB | name = Chicxulub | accessdate = 2008-12-30 }}</ref> Its center is located near the town of [[Chicxulub, Yucatán|Chicxulub]], after which the crater is named.<ref name=penfield /> The crater is more than 180 km (110 mi) in diameter, making the feature one of the [[List of impact craters on Earth#Confirmed impact craters listed by size|largest confirmed impact structures on Earth]]; the impacting [[bolide]] that formed the crater was at least 10 km (6 mi) in diameter.
The crater was discovered by Glen Penfield, a [[geophysics|geophysicist]] who had been working in the Yucatán while looking for [[petroleum|oil]] during the late 1970s. Penfield was initially unable to obtain evidence that the unique geological feature was in fact a crater, and gave up his search. Through contact with Alan Hildebrand, Penfield was able to obtain samples that suggested it was an impact feature. Evidence for the impact origin of the crater includes [[shocked quartz]], a [[gravity anomaly]], and [[tektite]]s in surrounding areas.
The age of the rocks shows that this impact structure dates from the end of the [[Cretaceous]] [[Period (geology)|Period]], roughly 65 [[million years ago]]. The impact associated with the crater is [[Cretaceous–Tertiary extinction event|implicated in causing the extinction]] of the [[dinosaur]]s as suggested by the [[K–T boundary]], the geological boundary between the Cretaceous and [[Tertiary]] periods, although some critics argue that the impact was not the sole reason<ref name=bakker>Bakker interview. "Does the [impact theory] explain the extinction of the dinosaurs? There ''are'' problems..."</ref> and others debate whether there was a single impact or whether the Chicxulub impactor was one of several that may have struck the Earth at around the same time. Recent evidence suggests that the impactor may have been a piece of a much larger asteroid that broke up in a collision in distant space more than 160 million years ago.<ref name=Bottke/>
In March 2010, following extensive analysis of the available evidence covering 20 years' worth of data spanning the fields of [[palaeontology]], [[geochemistry]], [[climate modelling]], [[geophysics]] and [[sedimentology]], 41 international experts from 33 institutions reviewed available evidence and concluded that the impact at Chicxulub triggered the [[mass extinction]]s at the K–T boundary including those of dinosaurs.<ref name="science">Schulte, et al.</ref><ref>Rincon.</ref>
==Discovery==
[[Image:Chicxulub-gravity-anomaly-m.png|thumb|Artist's rendering of the gravity anomaly map of the Chicxulub Crater area. Red and yellow are gravity highs; green and blue are gravity lows. White areas indicate multiple sinkholes, "cenotes". The shaded area is the Yucatan Peninsula.<ref>{{cite web
| url = http://rst.gsfc.nasa.gov/Sect18/Sect18_4.html
| title = Crater Morphology; Some Characteristic Impact Structures
| publisher = NASA | first = Nicholas M. | last = Short, Sr.
| accessdate = March 2010
}}</ref>]]
In 1978, geophysicists Antonio Camargo and Glen Penfield were working for the Mexican state-owned oil company [[Pemex|Petróleos Mexicanos]], or Pemex, as part of an airborne magnetic survey of the [[Gulf of Mexico]] north of the Yucatán peninsula.<ref name=verschuur>Verschuur, 20-21.</ref> Penfield's job was to use geophysical data to scout possible locations for oil drilling.<ref name=bates>Bates.</ref> Within the data, Penfield found a huge underwater arc with 'extraordinary symmetry' in a ring 70 km (40 mi) across.<ref name=penfield>Penfield.</ref> He then obtained a [[Gravity anomaly|gravity map]] of the Yucatán made in the 1960s. A decade earlier, the same map suggested an impact feature to contractor Robert Baltosser, but he was forbidden to publicize his conclusion by Pemex corporate policy of the time.<ref>Verschuur, 20.</ref> Penfield found another arc on the peninsula itself, the ends of which pointed northward. Comparing the two maps, he found the separate arcs formed a circle, 180 km (111 mi) wide, centered near the Yucatán village [[Chicxulub, Yucatán|Chicxulub]]; he felt certain the shape had been created by a cataclysmic event in geologic history.
Pemex disallowed release of specific data but let Penfield and company official Antonio Camargo present their results at the 1981 [[Society of Exploration Geophysicists]] conference.<ref>Weinreb.</ref> That year's conference was underattended and their report attracted scant attention. Ironically, many experts in [[impact crater]]s and the [[K–T boundary]] were attending a separate conference on Earth impacts. Although Penfield had plenty of geophysical data sets, he had no rock cores or other physical evidence of an impact.<ref name=bates/>
He knew Pemex had drilled exploratory wells in the region in 1951, one bored into what was described as a thick layer of [[andesite]] about 1.3 km (4,200 ft) 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. Penfield tried to secure site samples but was told such samples had been lost or destroyed.<ref name=bates/> When attempts at returning to the drill sites and looking for rocks proved fruitless, Penfield abandoned his search, published his findings and returned to his Pemex work.
[[Image:Chicxulub shockedquartz.png|thumb|left|Penfield with the sample of [[shocked quartz]] found at Well #2, Chicxulub]]
At the same time, scientist [[Luis Walter Alvarez]] put forth his hypothesis that a large extraterrestrial body had struck Earth and, unaware of Penfield's discovery, in 1981 [[University of Arizona]] graduate student Alan R Hildebrand and faculty adviser William V Boynton published a draft Earth-impact theory and sought a candidate crater.<ref>Mason.</ref> 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>Hildebrand, Penfield, et al.</ref> Thick, jumbled deposits of coarse rock fragments were also present, thought to have been scoured from one place and deposited elsewhere by a kilometres-high [[tsunami]] likely resulting from an Earth impact.<ref name=alanhild2/> Such deposits occur in many locations but seem concentrated in the [[Caribbean Basin|Caribbean]] basin at the K–T boundary.<ref name=alanhild2>Hildebrand interview: 'Similar deposits of rubble occur all across the southern coast of North America [...] indicate that something extraordinary happened here.'</ref> So 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.<ref name=moras>Morás.</ref> Tests on samples retrieved from the K–T boundary revealed more tektite glass, formed only in the heat of asteroid impacts and high-yield [[atom bomb|nuclear detonations]].<ref name=moras />
In 1990, ''[[Houston Chronicle]]'' reporter Carlos Byars told Hildebrand of Penfield's earlier discovery of a possible impact crater.<ref name=Frankel>Frankel, 50.</ref> Hildebrand contacted Penfield in April 1990 and the pair soon secured two drill samples from the Pemex wells, stored in [[New Orleans]].<ref name=alanhild>Hildebrand interview.</ref> Hildebrand's team tested the samples, which clearly showed [[Shock metamorphism|shock-metamorphic]] materials.
A team of California researchers including [[Kevin O. Pope|Kevin Pope]], Adriana Ocampo, and Charles Duller, surveying regional satellite images in 1996, found a [[sinkhole]] ([[cenote]]) ring centered on Chicxulub that matched the one Penfield saw earlier; the sinkholes were thought to be caused by [[subsidence]] of the impact crater wall.<ref>Pope, Baines, et al.</ref> More recent evidence suggests the actual crater is 300 km (190 mi) wide, and the 180 km ring an inner wall of it.<ref>Sharpton & Marin.</ref>
==Impact specifics==
[[Image:Chicxulub-animation.gif|thumb|right|An animation showing the impact, and subsequent crater formation (University of Arizona, Space Imagery Center)]]
The impactor had an estimated diameter of {{convert|10|km|mi|abbr=on}} and delivered an estimated {{convert|96|TtonTNT|J|lk=on}}.<ref>Covey ''et al.''</ref> By contrast, the most powerful man-made explosive device ever detonated, the [[Tsar Bomba]], had a yield of only {{convert|50|MtonTNT|J|lk=on}},<ref>Adamsky and Smirnov, 19.</ref> making the Chicxulub impact 2 million times more powerful. Even the most energetic known volcanic eruption, which released approximately {{convert|240|GtonTNT|J|lk=on}} and created the [[La Garita Caldera]],<ref>Mason, ''et al.''</ref> was substantially less powerful than the Chicxulub impact.
===Effects===
The impact would have caused some of the largest [[megatsunami]]s in Earth's history, reaching thousands of meters high. A cloud of super-heated dust, ash and steam would have spread from the crater, as the impactor burrowed underground in less than a second.<ref>Melosh, interview.</ref> Excavated material along with pieces of the impactor, ejected out of the atmosphere by the blast, would have been heated to incandescence upon re-entry, broiling the Earth's surface and possibly igniting global wildfires; meanwhile, colossal [[shock wave]]s would have effected global [[earthquakes]] and [[volcanic eruption]]s.<ref name=Molosh>Melosh. "On the ground, you would feel an effect similar to an oven on broil, lasting for about an hour [...] causing global forest fires."</ref> The emission of dust and particles could have covered the entire surface of the Earth for several years, possibly a decade, creating a harsh environment for living things. The shock production of [[carbon dioxide]] caused by the destruction of [[carbonate]] rocks would have led to a sudden [[greenhouse effect]].<ref name=ppg5>Hildebrand, Penfield, ''et al.''; 5.</ref> Over a longer period, sunlight would have been blocked from reaching the surface of the 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>Perlman.</ref><ref name=popeandocampo>Pope, Ocampo, ''et al.''</ref> A model of the event developed by Lomax et al. (2001) suggests that [[Primary productivity#GPP and NPP|net primary productivity]] (NPP) 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|last=Lomax|first=B.|coauthors=Beerling D., Upchurch Jr G. & Otto-Bliesner 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|url=http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V61-4441439-3&_user=10&_coverDate=10%2F15%2F2001&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1327486115&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=1f071c79677e3cb01503970a31509a1d|accessdate=8 May 2010|doi=10.1016/S0012-821X(01)00447-2|bibcode=2001E&PSL.192..137L}}</ref>
In February 2008, a team of researchers led by Sean Gulick at the University of Texas at Austin’s Jackson School of Geosciences used seismic images of the crater to determine that the impactor landed in deeper water than was previously assumed. They argued that this would have resulted in increased sulfate aerosols in the atmosphere. According to the press release, that "could have made the impact deadlier in two ways: by altering climate (sulfate aerosols in the upper atmosphere can have a cooling effect) and by generating acid rain (water vapor can help to flush the lower atmosphere of sulfate aerosols, causing acid rain)."<ref>{{Cite news |url=http://www.jsg.utexas.edu/news/2008/01/seismic-images-show-dinosaur-killing-meteor-made-bigger-splash/ |title=Seismic Images Show Dinosaur-Killing Meteor Made Bigger Splash |date=January 1, 2008 |author=Marc Airhart}}</ref>
===Geology and morphology===
In their 1991 paper, Hildebrand, Penfield, and company described the geology and composition of the impact feature.<ref>Hildebrand, Penfield, ''et al.''; 1.</ref> The rocks above the impact feature are layers of marl and [[limestone]] reaching to almost {{convert|1000|m|ft|abbr=on}} in depth. These rocks date back as far as the [[Paleocene]].<ref name=ppg3>Hildebrand, Penfield, ''et al.''; 3.</ref> Below these layers lie more than {{convert|500|m|ft|abbr=on}} of [[andesite]] glass and [[breccia]]. These andesitic [[igneous rock]]s were found only within the supposed impact feature; similarly, quantities of [[feldspar]] and [[augite]], normally only found in impact-melt rocks, are present,<ref>Grieve.</ref> as is [[shocked quartz]].<ref name=ppg3/> The K–T boundary inside the feature is depressed between {{convert|600|to|1100|m|ft|abbr=on}} compared to the normal depth of about {{convert|500|m|ft|abbr=on}} depth {{convert|5|km|mi}} away from the impact feature.<ref name=ppg4>Hildebrand, Penfield, ''et al.''; 4.</ref> Along the edge of the crater are clusters of [[cenote]]s or sinkholes, which suggest that there was a water basin inside the feature during the [[Tertiary period]], after the impact.<ref name=ppg4/> Such a basin's groundwater dissolved the [[limestone]] and created the caves and cenotes beneath the surface.<ref>Kring, "Discovering the Crater".</ref> The paper also noted that the crater seemed to be a good candidate source for the [[tektite]]s reported at [[Haiti]].<ref>Sigurdsson.</ref>
===Astronomical origin of asteroid===
On September 5, 2007, a report published in ''[[Nature (journal)|Nature]]'' proposed an origin for the asteroid that created Chicxulub Crater.<ref name=perlman/> The authors, [[William F. Bottke]], David Vokrouhlický, and David Nesvorný, argued that a collision in the asteroid belt 160 million years ago resulted in the creation of 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. The connection between Chicxulub and Baptistina is supported by the large amount of carbonaceous material present in microscopic fragments of the impactor, suggesting the impactor was a member of a rare class of asteroids called [[carbonaceous chondrite]]s, like Baptistina.<ref name=Bottke/> According to Bottke, the Chicxulub impactor was a fragment of a much larger parent body about {{convert|170|km|mi|abbr=on}} across, with the other impacting body being around 60 km (40 mi) in diameter.<ref name=Bottke>Bottke, Vokrouhlicky, Nesvorny.</ref><ref>Ingham.</ref> In 2011, new 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. This makes an asteroid from this family highly improbable to be the asteroid that created the Chicxulub Crater, as typically the process of resonance and collision of an asteroid takes many tens of millions of years.<ref name="Universe Today">{{cite news | first=Tammy | last=Plotner | title=Did Asteroid Baptistina Kill the Dinosaurs? Think other WISE... | url=http://www.universetoday.com/89050/did-asteroid-baptistina-kill-the-dinosaurs-think-other-wise/#more-89050 | work=Universe Today | date=2011| accessdate=2011-9-19}}</ref>
In 2010, another hypothesis was offered which implicated the newly-discovered asteroid [[P/2010 A2]], a member of the [[Flora family]] of asteroids, as a possible remnant cohort of the K/T impactor.<ref>[http://news.yahoo.com/s/nm/20100202/sc_nm/us_space_asteroid Smashed asteroids may be related to dinosaur killer, Yahoo! News, Feb. 2, 2010]</ref>
===Chicxulub and mass extinction===
{{main|Cretaceous–Tertiary extinction event}}
[[Image:Iridium clay layer.png|thumb|right|The piece of clay, held by Walter Alvarez, which sparked research into the impact theory. The greenish-brown band in the center is extremely rich in [[iridium]].]]
The Chicxulub Crater lends support to the theory postulated by the late [[physicist]] [[Luis Alvarez]] and his son, [[geologist]] [[Walter Alvarez]], that the extinction of numerous animal and plant groups, including [[dinosaur]]s, may have resulted from a [[bolide]] impact (the [[Cretaceous-Tertiary extinction event]]). Luis and Walter Alvarez, at the time both faculty members at the [[UC Berkeley|University of California, Berkeley]], postulated that this enormous extinction event, which was roughly contemporaneous with the postulated date of formation for the Chicxulub crater, could have been caused by just such a large impact.<ref>Alvarez, W. interview.</ref> This theory is now widely accepted by the [[scientific community]]. Some critics, including [[paleontology|paleontologist]] [[Robert Bakker]], argue that such an impact would have killed [[frog]]s as well as dinosaurs, yet the frogs survived the extinction event.<ref>Kring, "Environment Consequences".</ref> [[Gerta Keller]] of [[Princeton University]] argues that recent core samples from Chicxulub prove the impact occurred about 300,000 years ''before'' the mass extinction, and thus could not have been the causal factor.<ref>Keller, ''et al.''</ref>
The main evidence of such an impact, besides the crater itself, is contained in a thin layer of clay present in the [[K–T boundary]] across the world. In the late 1970s, the Alvarezes and colleagues reported<ref name=alvarez>Alvarez.</ref> that it contained an abnormally high concentration of [[iridium]]. Iridium levels in this layer reached 6 parts per billion by weight or more compared to 0.4<ref>Web Elements.</ref> for the Earth's crust as a whole; in comparison, meteorites can contain around 470 parts per billion<ref>Quivx.</ref> of this element. It was hypothesized that the iridium was spread into the atmosphere when the impactor was vaporized and settled across the Earth's surface amongst other material thrown up by the impact, producing the layer of iridium-enriched clay.<ref>Mayell.</ref>
==Multiple impact theory==
In recent years, several other craters of around the same age as Chicxulub have been discovered, all between latitudes 20°N and 70°N. Examples include the [[Silverpit crater]] in the [[North Sea]]<ref>Stewart, Allen.</ref> and the [[Boltysh crater]] in [[Ukraine]].<ref>Kelley, Gurov.</ref> Both are much smaller than Chicxulub, but likely to have been caused by objects many tens of metres across striking the Earth.<ref>Stewart.</ref> This has led to the hypothesis that the Chicxulub impact may have been only one of several impacts that happened nearly at the same time.<ref name=multiple/> Another possible crater thought to have been formed at the same time is the [[Shiva crater]],<ref name=Economist1009>{{cite web|url=http://www.economist.com/sciencetechnology/displaystory.cfm?story_id=14698363|title=Mass extinctions: I am become Death, destroyer of worlds|date=2009-10-22|publisher=[[The Economist]]|accessdate=2009-10-24}}</ref> though the structure's status as a crater is contested.<ref>Mullen, "Shiva".</ref>
The collision of [[Comet Shoemaker-Levy 9]] with Jupiter in 1994 demonstrated that gravitational interactions can fragment a comet, giving rise to many impacts over a period of a few days if the comet should collide with a planet. Comets undergo gravitational interactions with the [[gas giant]]s, and similar disruptions and collisions are very likely to have occurred in the past.<ref name=Economist1009/><ref name=Weisstein>Weisstein.</ref> This scenario may have occurred on Earth 65 million years ago,<ref name=multiple>Mullen, "Multiple Impacts".</ref> though Shiva and the Chicxulub craters might have been formed 300,000 years apart.<ref name=Economist1009/>
In late 2006, Ken MacLeod, a [[geology]] professor from the [[University of Missouri]], completed an analysis of [[sediment]] below the ocean's surface, bolstering the single-impact theory. MacLeod conducted his analysis approximately 4,500 km (2,800 mi) from the Chicxulub Crater to control for possible changes in soil composition at the impact site, while still close enough to be affected by the impact. The analysis revealed there was only one layer of impact debris in the sediment, which indicated there was only one impact.<ref>Than.</ref> Multiple-impact proponents such as [[Gerta Keller]] regard the results as "rather hyper-inflated" and do not agree with the conclusion of MacLeod's analysis.<ref>Dunham.</ref>
==See also==
*[[Deccan Traps]]
*[[Permian–Triassic extinction event]]
*[[Vredefort Crater]]
*[[Wilkes Land crater]]
==Notes==
{{Reflist|colwidth=30em}}
==References==
{{Refbegin|2}}
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*:Hildebrand, Alan. Interview: ''The Dinosaurs: Death of the Dinosaur''. 1992, [[WHYY-TV|WHYY]].
*:[[H. Jay Melosh|Melosh, Gene]]. Interview: ''The Dinosaurs: Death of the Dinosaur''. 1992, (1990): [[WHYY-TV|WHYY]].
*:Moras, Florentine. Interview: ''The Dinosaurs: Death of the Dinosaur''. 1992, (filmed 1990): [[WHYY-TV|WHYY]].
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*{{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|accessdate=2007-10-12| archiveurl = http://web.archive.org/web/20071010021337/http://www.lpl.arizona.edu/SIC/impact_cratering/Chicxulub/Discovering_crater.html| archivedate = October 10, 2007}}
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*{{cite web|author=Mason, Moya K.|url=http://www.moyak.com/papers/citation-searching.html|title=In Search of a Key Paper|year=2007|work=moyak.com|accessdate=2009-04-03}}
*{{cite web|author=Mayell, Hillary|url=http://news.nationalgeographic.com/news/2005/04/0415_050418_chicxulub.html|title= Asteroid Rained Glass Over Entire Earth, Scientists Say| work=[[National Geographic]] News |date=2005-05-15|accessdate=2007-10-01}}
*{{cite journal| author=Mullen, Leslie|date=2004-11-04|url=http://www.spacedaily.com/news/deepimpact-04r.html|title=Deep Impact – Shiva: Another K–T Impact?|journal=Astrobiology Magazine|accessdate=2007-09-29}}
*{{cite web|author=Mullen, Leslie|date=2004-10-21|url=http://www.spacedaily.com/news/deepimpact-04p.html|title=Did Multiple Impacts Pummel Earth 35 Million Years Ago?|work=spacedaily.com|accessdate=2007-09-29}}
*{{cite web|author=Perlman, David|url=http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2007/09/06/MNVFRUVCK.DTL|title=Scientists say they know where dinosaur-killing asteroid came from|work=San Francisco Chronicle|date=2007-09-06|accessdate=2007-10-03}}
*{{cite journal | author=Pope KO, Baines KH, Ocampo AC, Ivanov BA | title=Energy, volatile production, and climatic effects of the Chicxulub Cretaceous/Tertiary impact | journal=Journal of Geophysical Research | volume=102 | issue=E9 | year=1997 | pages=245–64 | pmid=11541145 | doi=10.1029/97JE01743 | bibcode=1997JGR...10221645P}}
*{{cite journal | author=Pope KO, Ocampo AC, Kinsland GL, Smith R | title=Surface expression of the Chicxulub crater | journal=[[Geology (journal)|Geology]] | volume=24 | issue=6 | year=1996 | pages=527–30 | pmid=11539331 | doi=10.1130/0091-7613(1996)024<0527:SEOTCC>2.3.CO;2|bibcode = 1996Geo....24..527P }}
*{{cite news|author=Rincon, Paul|date=2010-03-04|url=http://news.bbc.co.uk/2/hi/science/nature/8550504.stm|title=Dinosaur extinction link to crater confirmed|work=[[BBC]]|accessdate=2010-03-05}}
*{{cite web| author=Qivx Inc.|year=2003|url=http://www.qivx.com/ispt/elements/ptw_077.php| title=Periodic Table: Properties of Iridium|work=qivx.com|accessdate=2007-09-25}}
*{{cite journal | author=Rojas-Consuegra, R., M. A. Iturralde-Vinent, C. Díaz-Otero y D. García-Delgado | title=Significación paleogeográfica de la brecha basal del Límite K/T en Loma Dos Hermanas ([[Loma del Capiro]]), en Santa Clara, provincia de Villa Clara. I Convención Cubana de Ciencias de la Tierra | journal=Geociencias| volume=8 | issue=6 | year=2005 | pages=1–9 | isbn=959-7117-03-7}}
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*{{cite journal | author=Sharpton VL, Marin LE | title=The Cretaceous–Tertiary impact crater and the cosmic projectile that produced it | journal=Annals of the New York Academy of Sciences | year=1997 | volume=822 | pages=353–80 | pmid=11543120 | doi=10.1111/j.1749-6632.1997.tb48351.x|bibcode = 1997NYASA.822..353S }}
*{{cite journal | author=Stewart, S. A. | title=3D seismic reflection mapping of the Silverpit multi-ringed crater, North Sea | journal=Geological Society of America Bulletin | year=2005 | volume=117 | issue=3 | pages=354–368|doi=10.1130/B25591.1|url=http://www.gsajournals.org/perlserv/?request=get-document&doi=10.1130%2FB25591.1 | last2=Allen | first2=P.J. }}
*{{cite journal | author=Stewart S. A., Allen P. J.|title=A 20-km-diameter multi-ringed impact structure in the North Sea|journal=[[Nature (journal)|Nature]] | volume=418 | issue=6897 | year=2002 | pages=520–3 | pmid=12152076
| doi = 10.1038/nature00914}}
*{{cite web|author=Than, Ker|date=2006-11-28|url=http://www.livescience.com/animals/061128_dinosaur_extinct.html|title=Study: Single Meteorite Impact Killed Dinosaurs|work=livescience.com|accessdate=2007-09-29}}
*{{cite book|author=[[Gerrit Verschuur|Verschuur]], Gerrit L.|title=Impact!: The Threat of Comets and Asteroids|year=1996|publisher=Oxford University Press (U.S.)|isbn=0-19-511919-3}}
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{{Refend}}
==External links==
{{commons category|Chicxulub crater}}
*[http://maps.google.com/maps?q=http://bbs.keyhole.com/ubb/download.php?Number=1226046&t=k&om=1 Satellite image of the region] (from Google Maps)
*[http://bbs.keyhole.com/ubb/download.php?Number=1226046 Numerous sinkholes (Cenotes) marked around Chicxulub crater.] Opens in Google Earth
*[http://www.jpl.nasa.gov/news/features.cfm?feature=8 NASA JPL: "A 'Smoking Gun' for Dinosaur Extinction"], March 6, 2003
*[http://phobos.physics.uiowa.edu/~srs/2952_EXW/Addend9_EXW.htm Chicxulub, Crater of Doom]
*[http://www.scientificamerican.com/article.cfm?id=doubts-on-dinosaurs''Doubts On Dinosaurs'' – Scientific American.]
{{KT_boundary}}
{{Impact cratering on Earth}}
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{{Featured article}}
{{DEFAULTSORT:Chicxulub Crater}}
[[Category:Impact craters of Mexico]]
[[Category:Mérida, Yucatán]]
[[Category:Cretaceous impact craters]]
[[Category:Dinosaurs]]
[[Category:Extinction events]]
[[Category:Geological history of Earth]]
[[Category:Natural history of the Yucatán]]
[[Category:Natural history of the Caribbean]]
{{Link GA|es}}
{{Link FA|ca}}
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[[it:Cratere di Chicxulub]]
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[[lv:Čikšulubas krāteris]]
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[[zh:希克蘇魯伯隕石坑]]' |
