| Thirty years after the discovery of anomalous amounts of the element iridium exactly at the Cretaceous-Paleogene (formerly Tertiary) boundary (K-PgB), the impact-extinction hypothesis has reached adulthood and now ranks among the great geological paradigms such as plate tectonics. Incessant testing, successive new discoveries, competition of rival theories, all contributed to strengthen the theory through those 30 years. |