Cretaceous–Paleogene extinction event

A global mass extinction about 66 million years ago that eliminated non-avian dinosaurs and many other species, marking the end of the Cretaceous Period.

Chicxulub impactor: The asteroid whose impact at Chicxulub is linked to the Cretaceous–Paleogene extinction. Its collision released the energy that initiated the extinction crisis.
K–Pg boundary: The geological boundary marking the transition from the Cretaceous to the Paleogene, about 66 million years ago. The boundary layer records the abrupt global transition associated with the extinction.
Walter Alvarez: An American geologist who helped propose an asteroid impact as the cause of the K–Pg extinction. His work connected the boundary iridium anomaly to a major impact.
Volcanism hypothesis: The explanation that extensive eruptions of the Deccan Traps contributed substantially to the end-Cretaceous extinction. It emphasizes volcanic climate disruption rather than a single impact as the principal driver.
Non-avian dinosaurs: Dinosaurs other than birds, which disappeared from the fossil record at the end of the Cretaceous. Their disappearance is the event’s best-known terrestrial loss.
Chicxulub crater: A buried impact structure in Mexico’s Yucatán Peninsula, about 180 kilometers wide. Its geology preserves direct evidence of the impact associated with the extinction.
Iridium anomaly: An unusually high concentration of iridium found in sediment layers at the K–Pg boundary. The anomaly helped identify an extraterrestrial source for the boundary material.
Luis Alvarez: An American physicist who co-developed the impact explanation for the K–Pg extinction with Walter Alvarez. His expertise helped interpret the iridium layer as evidence of extraterrestrial material.
Gradualism: The view that major geological and biological changes generally accumulate through slow, continuous processes. It contrasts with evidence for a sharp extinction pulse at the boundary.
Ammonites: Marine cephalopods with coiled shells that became extinct at the end of the Cretaceous. Their extinction shows the event’s reach across marine ecosystems.

Linked from 99 pages