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Which events may have caused the mass extinction at the Cretaceous-Paleogene boundary?

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Messinian Stage — Tertiary Period Gypsum cones, which resulted from the evaporation of the Mediterranean Sea during the Messinian Salinity Crisis, in the Sorbas basin, Spain.

The mass extinction at the Cretaceous-Paleogene (K-Pg) boundary, formerly known as the K-T boundary, is widely attributed to a combination of catastrophic and terrestrial factors.123

The Asteroid Impact Theory

The most prominent explanation is the impact of a large asteroid or comet approximately 66 million years ago. Evidence for this includes:43
* Chicxulub Crater: A massive impact crater located near the Yucatán Peninsula in Mexico.45
* Geochemical Signatures: The presence of iridium and tektites in geological deposits from that time.43
* Environmental Consequences: The impact likely triggered tsunamis, wildfires, and a global dust cloud that blocked sunlight, halting photosynthesis and collapsing food chains.415

Terrestrial Factors

Many researchers suggest that life was already struggling due to environmental flux, potentially caused by:
* Volcanism: Massive lava outpourings known as the Deccan Traps in India may have released carbon dioxide, causing a global greenhouse effect.43
* Tectonic Activity: Continental drift and the draining of continental seas led to habitat deterioration and climate cooling.13

It is likely that the extinction resulted from multiple causes, where a catastrophic impact exacerbated an already deteriorating environment.413