End-cretaceous

Definition

The end-cretaceous refers to a significant geological boundary occurring approximately 66 million years ago, marking the transition between the Cretaceous and Paleogene periods. This event is widely recognized for triggering one of the most dramatic mass extinctions in Earth's history, resulting in the extinction of nearly 75% of all species, including the non-avian dinosaurs. The end-cretaceous event is linked to various environmental changes and catastrophic occurrences that reshaped life on Earth.

5 Must Know Facts For Your Next Test

1. The end-cretaceous mass extinction is most famously associated with the extinction of the dinosaurs, but it also affected many marine and terrestrial species.
2. Evidence suggests that both an asteroid impact and extensive volcanic activity were contributing factors to the dramatic environmental shifts during this period.
3. The environmental changes during the end-cretaceous included global cooling, reduced sunlight due to dust and debris, and acid rain resulting from atmospheric changes.
4. The aftermath of the end-cretaceous event led to the rise of mammals as dominant terrestrial vertebrates, paving the way for evolutionary developments in subsequent periods.
5. This extinction event serves as a critical case study for understanding patterns of biodiversity loss and recovery in response to sudden environmental changes.

Review Questions

• What were the primary causes of the end-cretaceous mass extinction, and how did they contribute to the drastic loss of biodiversity?
  • The primary causes of the end-cretaceous mass extinction include a massive asteroid impact, evidenced by the Chicxulub Crater, and extensive volcanic eruptions known as the Deccan Traps. The impact likely caused a 'nuclear winter' effect by ejecting debris into the atmosphere, leading to global cooling and reduced sunlight. Additionally, volcanic activity released greenhouse gases and sulfur dioxide, which further altered climate and ecosystems, contributing significantly to biodiversity loss.
• Discuss the significance of the end-cretaceous boundary in understanding evolutionary patterns in Earth's history.
  • The end-cretaceous boundary is significant as it marks a turning point in evolutionary history, demonstrating how mass extinctions can radically alter ecological dynamics. Following this event, mammals began to diversify and occupy ecological niches left vacant by the extinct reptiles. This transition emphasizes how evolutionary paths can be redirected by catastrophic events, shaping future biodiversity and community structures.
• Evaluate how studying past mass extinction events like the end-cretaceous can inform our understanding of current biodiversity crises.
  • Studying past mass extinction events like the end-cretaceous provides critical insights into how species respond to rapid environmental changes. Understanding factors such as habitat destruction, climate shifts, and ecological interactions during these periods helps scientists predict potential outcomes of today's biodiversity crises. The lessons learned highlight the resilience of some species versus vulnerability in others, emphasizing the importance of conservation efforts in mitigating similar patterns in modern times.

Related terms

Chicxulub Crater: A large impact crater located on the Yucatán Peninsula in Mexico, believed to be the result of an asteroid impact that contributed to the end-cretaceous mass extinction.

Mass Extinction: A rapid and widespread decrease in biodiversity on Earth, where a substantial number of species go extinct in a relatively short period.

Deccan Traps: A large volcanic province in India formed by extensive volcanic eruptions that occurred around the time of the end-cretaceous, contributing to environmental changes.