Cretaceous-Paleogene Extinction Event
The Cretaceous-Paleogene (K-Pg) extinction event (also known as the K-T extinction) was a mass extinction event that occurred approximately 66 million years ago, marking the boundary between the Cretaceous and Paleogene periods. It resulted in the disappearance of approximately 75% of plant and animal species on Earth, including all non-avian Dinosaurs.
Primary Cause
The prevailing scientific consensus identifies the chicxulub-impact as the primary trigger. A ~10 km diameter asteroid struck the Yucatán Peninsula, causing immediate shockwaves, thermal radiation, and global ejecta.
- Source Integration: See Dinosaur Extinction Event: Chicxulub Impact, Aftermath, and Earth’s Recovery for detailed breakdown of impact mechanics.
Environmental Aftermath
- Impact Winter: Soot and aerosols blocked sunlight for months to years, halting Photosynthesis.
- Ocean Acidification: Dissolved CO2 and sulfur compounds lowered ocean pH, decimating marine food webs (e.g., Plankton, Ammonites).
- Acid Rain: Vaporized carbonate rocks from the impact site created widespread acid rain, harming freshwater ecosystems.
Selective Survival & Recovery
- Survivors: Small-bodied Mammals, birds (avian dinosaurs), crocodilians, and turtles survived due to varied diets, burrowing capabilities, or semi-aquatic lifestyles buffering against temperature swings.
- Ecological Reset: The collapse of dominant herbivores and carnivores opened ecological niches.
- Cenozoic Era: Initiated the “Age of Mammals,” characterized by rapid diversification of mammalian lineages and flowering plant (Angiosperm) expansion.