Extinction of the dinosaurs

Research identified a layer of rock with high iridium concentrations dating to sixty-five million years ago, hinting at a massive asteroid impact linked to the extinction of dinosaurs. This discovery provided substantial evidence for the theory of an impact event leading to a mass extinction.
 Walter Alvarez United States 1979 Extinction of the dinosaurs

Research identified a layer of rock with high iridium concentrations dating to sixty-five million years ago, hinting at a massive asteroid impact linked to the extinction of dinosaurs. This discovery provided substantial evidence for the theory of an impact event leading to a mass extinction.