End-Cretaceous

Definition

The End-Cretaceous refers to a significant geological period marking the boundary between the Cretaceous and Paleogene periods, approximately 66 million years ago. This era is most famously associated with one of the largest mass extinctions in Earth's history, which resulted in the loss of approximately 75% of all species, including the non-avian dinosaurs. The causes of this extinction event, primarily attributed to a combination of volcanic activity and a catastrophic asteroid impact, have had profound implications for biodiversity and the evolutionary trajectories of life on Earth.

5 Must Know Facts For Your Next Test

1. The End-Cretaceous mass extinction event is one of the 'Big Five' mass extinctions in Earth's history, drastically reshaping the planet's biodiversity.
2. The impact site of the asteroid is located in the Yucatán Peninsula, known as the Chicxulub crater, which is over 150 kilometers in diameter.
3. The aftermath of the End-Cretaceous saw mammals and birds diversify rapidly into niches left vacant by extinct reptiles, setting the stage for modern ecosystems.
4. Evidence suggests that volcanic eruptions in the Deccan Traps coincided with the mass extinction and contributed to long-term climate changes.
5. The study of fossil records from this period has provided critical insights into how ecosystems recover after mass extinction events and how life adapts to changing conditions.

Review Questions

• What were some major environmental changes that occurred during the End-Cretaceous, and how did they contribute to the mass extinction?
  • During the End-Cretaceous, significant environmental changes were triggered by both volcanic activity and an asteroid impact. The asteroid collision likely caused massive wildfires, tsunamis, and a 'nuclear winter' effect due to debris blocking sunlight. This led to a rapid drop in global temperatures and disrupted photosynthesis, which critically affected food chains and ecosystems worldwide.
• Discuss the implications of the End-Cretaceous mass extinction for future biodiversity on Earth.
  • The End-Cretaceous mass extinction had profound implications for future biodiversity as it paved the way for new groups of organisms to thrive. With the extinction of dinosaurs and many marine reptiles, mammals began to diversify and occupy ecological niches that were previously unavailable. This event set in motion evolutionary pathways leading to the emergence of modern mammals and birds, illustrating how mass extinctions can create opportunities for new life forms to evolve.
• Evaluate how the study of the End-Cretaceous helps us understand current biodiversity crises and conservation efforts.
  • Studying the End-Cretaceous provides valuable insights into how ecosystems respond to catastrophic events and recover over time. Understanding past mass extinctions allows scientists to identify patterns in biodiversity loss and resilience. This knowledge is crucial for current conservation efforts as it informs strategies for protecting endangered species and ecosystems under threat from human activities, climate change, and habitat destruction. By learning from historical events, we can develop better approaches to mitigating biodiversity crises today.

Related terms

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

Asteroid Impact: A collision of a large celestial body with Earth, believed to have contributed significantly to the environmental changes that led to the End-Cretaceous mass extinction.

Deccan Traps: A large volcanic province in India, whose extensive lava flows are thought to have released significant amounts of gases, contributing to climate changes around the time of the End-Cretaceous.