Cretaceous-Paleogene extinction event

Definition

The Cretaceous-Paleogene extinction event was a major global extinction event that occurred around 66 million years ago, marking the end of the Cretaceous period and the beginning of the Paleogene period. This event is most famously associated with the mass extinction of dinosaurs, along with numerous other species, leading to significant changes in Earth's biodiversity and ecosystems.

5 Must Know Facts For Your Next Test

1. The Cretaceous-Paleogene extinction event is estimated to have led to the extinction of about 75% of all species on Earth, including all non-avian dinosaurs.
2. This event is linked to two major causes: the impact of an asteroid or comet and extensive volcanic activity in the Deccan Traps.
3. The Chicxulub impact is thought to have caused massive wildfires, tsunamis, and a 'nuclear winter' effect due to dust and debris blocking sunlight.
4. Following this extinction event, mammals began to diversify and eventually became the dominant terrestrial vertebrates in the Paleogene period.
5. The Cretaceous-Paleogene boundary is marked by a distinct layer of iridium-rich clay found in the geologic record, providing strong evidence for an extraterrestrial impact.

Review Questions

• How did the Cretaceous-Paleogene extinction event impact biodiversity on Earth?
  • The Cretaceous-Paleogene extinction event had a profound impact on biodiversity, resulting in the extinction of approximately 75% of all species. This included the complete disappearance of non-avian dinosaurs and many marine reptiles. The loss of these dominant species allowed for new groups, particularly mammals, to rise and diversify in the aftermath, fundamentally altering ecosystems and biological communities across the planet.
• Discuss the potential causes of the Cretaceous-Paleogene extinction event and how they may have interacted with one another.
  • The primary causes of the Cretaceous-Paleogene extinction event are linked to an asteroid impact at Chicxulub and extensive volcanic activity in the Deccan Traps. The asteroid impact likely triggered immediate catastrophic effects like wildfires and climate change due to debris blocking sunlight. Concurrently, volcanic eruptions could have released gases that contributed to long-term climate alterations. Together, these events created a harsh environment that could not support many species, leading to widespread extinction.
• Evaluate the significance of the Cretaceous-Paleogene extinction event in shaping modern ecosystems and biodiversity.
  • The significance of the Cretaceous-Paleogene extinction event lies in its role as a pivotal turning point in Earth's biological history. The mass extinction opened ecological niches that allowed mammals to diversify and evolve into many forms we see today. This transition set the stage for modern ecosystems and influenced evolutionary paths, demonstrating how catastrophic events can reshape biodiversity. Understanding this event helps scientists predict how current environmental changes may affect life on Earth moving forward.

Related terms

Chicxulub Crater: The impact site in Mexico's Yucatán Peninsula where a large asteroid is believed to have struck Earth, contributing to the Cretaceous-Paleogene extinction event.

Mass Extinction: A rapid and widespread decrease in the biodiversity on Earth, often characterized by the loss of a large number of species in a relatively short period of geological time.

Deccan Traps: A large volcanic province in India that released massive amounts of lava and gases, which may have contributed to environmental changes during the time of the Cretaceous-Paleogene extinction.