Around 66 million years ago, a large asteroid struck what is now the Yucatán Peninsula, forming the Chicxulub crater and marking the boundary between the Cretaceous and the Paleogene. This event represents one of the most abrupt and severe disruptions in the history of life on Earth.
The impact released an enormous amount of energy in a matter of seconds, generating shock waves, global earthquakes, massive wildfires, and tsunamis. Vast quantities of dust, aerosols, and sulfur-rich compounds were injected into the atmosphere, severely reducing sunlight at the surface. This led to a rapid collapse of photosynthesis, triggering cascading failures across terrestrial and marine food webs.
In the months to years following the impact, Earth experienced a short but intense “impact winter.” Global temperatures dropped, plant productivity plummeted, and ecosystems dependent on stable primary production suffered catastrophic losses. Large-bodied organisms with high energy demands were particularly vulnerable under these conditions.
However, the Chicxulub impact was not the sole cause of extinction. It acted as a terminal shock to ecosystems that were already under stress from long-term climatic change, sea-level fluctuations, and ecological restructuring. The extinction pattern at the K–Pg boundary reflects both the suddenness of the impact and the reduced resilience of late Cretaceous ecosystems.
The event eliminated all non-avian dinosaurs, along with many marine reptiles, ammonites, and numerous planktonic groups. At the same time, it opened ecological space for surviving lineages, reshaping the trajectory of life in the Cenozoic.
The Chicxulub impact marks a clear geological boundary, but biologically it represents the final phase of a longer process. It was not the single story of extinction, but the decisive endpoint of a world already in transition.