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What evidence links the Chicxulub crater to the extinction at the end of the Cretaceous Period?
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Earth impact hazard
An artist's rendering of the impact of a near-Earth object 66 million years ago in what is today the Caribbean region. Many scientists think that the collision of a large asteroid or comet nucleus with Earth triggered the mass extinction of dinosaurs and many other species near the end of the Cretaceous Period.
The link between the Chicxulub crater and the mass extinction at the end of the Cretaceous Period is supported by several lines of geological and geochemical evidence:
- Iridium Anomaly: In 1980, Walter Alvarez and his collaborators discovered a worldwide layer of clay at the Cretaceous-Paleogene (K–T) boundary containing high concentrations of iridium. Because iridium is rare on Earth's surface but abundant in meteorites, this suggested a massive extraterrestrial impact.12
- Crater Identification: Researchers identified the 180-km-wide Chicxulub crater off the Yucatán Peninsula as the site of this impact. Core samples from the region contain shocked quartz and fused rocks, which are signatures of extreme heat and pressure associated with asteroid collisions.1
- Tektites and Dating: Geological layers at the K–T boundary contain tektites—natural glass formed during impacts. These deposits, along with the crater itself, have been dated to approximately 66 million years ago, matching the timing of the mass extinction.1
- Environmental Signatures: The crater region shows a significant depletion of sulfur, suggesting that the impact vaporized sulfurous minerals, releasing massive amounts of aerosols into the atmosphere that likely caused global cooling and acid rain.13