Cretaceous–Paleogene extinction event

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Cretaceous–Paleogene extinction event (K–Pg extinction event), also known as the Cretaceous–Tertiary (K–T) extinction, marks a pivotal moment in Earth's history, approximately 66 million years ago, when a catastrophic event led to the mass extinction of roughly three-quarters of the plant and animal species on the planet, including all non-avian dinosaurs. This event delineates the boundary between the Cretaceous and Paleogene periods, part of the larger geologic timescale.

Causes

The primary cause of the K–Pg extinction event is widely attributed to a significant asteroid or comet impact, evidenced by the Chicxulub crater located in the Yucatán Peninsula, Mexico. The impact would have released an immense amount of energy, leading to fires, tsunamis, and a prolonged period of global cooling and darkness, significantly altering the Earth's climate. This theory is supported by the worldwide layer of sediment enriched with iridium—a rare element on Earth's crust but common in asteroids and comets—dating back to the time of the extinction.

Volcanic activity, specifically the massive eruptions that created the Deccan Traps in present-day India, is also considered a contributing factor. These eruptions would have released large quantities of volcanic gas, dust, and aerosols into the atmosphere, exacerbating climate change and environmental stress on a global scale.

Impact on Life

The K–Pg extinction event had a profound impact on the planet's biodiversity. The most notable victims were the non-avian dinosaurs, which had dominated terrestrial ecosystems for over 160 million years. Marine reptiles, such as mosasaurs and plesiosaurs, and flying reptiles like pterosaurs, also became extinct. In the oceans, the extinction event severely affected plankton, ammonites, many species of foraminifera, and other marine organisms, leading to cascading effects through the food chain.

However, the extinction event also paved the way for the rise of mammals and, eventually, humans. In the aftermath, mammalian species diversified and filled niches left vacant by the extinction of the dinosaurs. The Cenozoic Era, often referred to as the Age of Mammals, began following the K–Pg boundary.

Evidence

Evidence for the K–Pg extinction event is found in a distinct layer of sediment worldwide, known as the K–Pg boundary, characterized by a high concentration of iridium. Geological and fossil records also show a dramatic change in the diversity and abundance of plant and animal life across this boundary. Studies of the fossil record indicate a sudden and massive loss of species coinciding with the event.

Legacy

The K–Pg extinction event has captivated scientists and the public alike, highlighting the fragility of life on Earth and the potential for global events to radically alter the course of biological evolution. It serves as a stark reminder of the impacts of asteroid impacts and volcanic activity on Earth's biosphere.

Research into the K–Pg extinction continues to evolve, with scientists using advanced technologies and methodologies to understand the complexities of this pivotal moment in Earth's history. The event remains a key area of study in the fields of paleontology, geology, and climatology, offering insights into the dynamics of mass extinctions and their effects on the planet's biodiversity.

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