Alvarez hypothesis

The hypothesis that an asteroid impact caused the mass extinction at the Cretaceous–Paleogene boundary, including the extinction of non-avian dinosaurs.

Chicxulub impactor: The asteroid whose impact at Chicxulub, Mexico, is linked to the Cretaceous–Paleogene mass extinction. Its collision with Earth is the event at the center of the hypothesis.
Luis Alvarez: An American physicist who shared the 1968 Nobel Prize in Physics for work in particle physics. He proposed that an impact could explain the boundary iridium anomaly.
Deccan Traps: A vast volcanic province in India formed by repeated eruptions near the end of the Cretaceous. Its volcanism offers a major alternative or contributing cause of the extinction.
Non-avian dinosaurs: Dinosaurs other than birds, all of which disappeared in the Cretaceous–Paleogene extinction. Their disappearance is the best-known consequence attributed to the impact.
Chicxulub crater: A buried impact crater on Mexico’s Yucatán Peninsula, formed about 66 million years ago. Its age, size, and location identify the impact site proposed by the hypothesis.
Walter Alvarez: An American geologist whose research helped identify the Cretaceous–Paleogene boundary iridium anomaly. His field observations in Italy began the investigation behind the hypothesis.
Volcanism hypothesis: The explanation that large-scale volcanic eruptions drove environmental change and contributed to the end-Cretaceous extinction. It attributes much of the crisis to Deccan Traps eruptions rather than the impact alone.
Ammonites: Extinct marine mollusks with coiled shells that flourished for much of the Mesozoic Era. Their extinction shows the crisis extended beyond terrestrial dinosaurs.
Iridium anomaly: An unusually high concentration of iridium in rocks at the Cretaceous–Paleogene boundary. The global boundary-layer anomaly supplied the initial evidence for an extraterrestrial impact.
Frank Asaro: An American nuclear chemist who used neutron activation analysis to measure trace elements in geological samples. His measurements revealed unusually high iridium in boundary clay.

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Chicxulub impactRelated: The 1980 proposal anticipated the impact later linked to the Chicxulub structure.