The K-T Extinction
66000000 BCE
Mass extinction marking the end of non-avian dinosaurs.
Historical Context
During the Late Cretaceous, dinosaurs ruled the terrestrial fauna for over 160 million years. Small mammals lived in their nocturnal shadow.
The Event
66 million years ago, a 10 km wide asteroid crashed into the present-day Yucatán Peninsula (Chicxulub). The colossal impact triggered a planetary nuclear winter, blocking photosynthesis.
Key Figures
Luis and Walter Alvarez (father and son scientists who proved the impact via the iridium anomaly in 1980).
Aftermath
Destruction of 75% of living species. The abrupt end of non-avian dinosaurs freed immense ecological niches, allowing the adaptive radiation of mammals and birds.
Legacy & Culture
Without this contingent cataclysm, human evolution would likely never have occurred. The K-T extinction serves as a reminder of the biosphere's extreme vulnerability to cosmic threats.
Historiography
Before 1980, gradualism dominated: dinosaurs were thought to have died out slowly. The Alvarez theory reintroduced the scientific acceptance of catastrophism in Earth's history.
Sources and References
Cratère de Chicxulub (Péninsule du Yucatán)
Anomalie en iridium à la limite Crétacé-Paléogène