Cretaceous-Paleogene

Definition

The Cretaceous-Paleogene (also known as the K-T or K-Pg) is the geological boundary that marks the end of the Mesozoic Era and the beginning of the Cenozoic Era. It is defined by a mass extinction event that occurred approximately 66 million years ago, which resulted in the extinction of the dinosaurs and many other species.

5 Must Know Facts For Your Next Test

1. The Cretaceous-Paleogene boundary is marked by a thin layer of clay that is enriched in the rare metal iridium, which is more common in asteroids and comets than in the Earth's crust.
2. The leading hypothesis for the cause of the Cretaceous-Paleogene mass extinction is the impact of a large asteroid or comet, which is believed to have triggered widespread environmental changes, including climate shifts, volcanic activity, and the collapse of the food chain.
3. The extinction of the dinosaurs at the Cretaceous-Paleogene boundary paved the way for the rise of mammals, which then diversified and evolved into the wide range of species we see today.
4. The Cretaceous-Paleogene mass extinction is considered one of the five major mass extinction events in Earth's history, along with the Ordovician-Silurian, Devonian, Permian-Triassic, and Triassic-Jurassic extinctions.
5. The Cretaceous-Paleogene boundary is a significant marker in the geological timescale, as it represents a major transition in the evolution of life on Earth, from the dominance of reptiles to the rise of mammals and other modern forms of life.

Review Questions

• Explain the significance of the Cretaceous-Paleogene boundary in the context of cosmic influences on the evolution of Earth.
  • The Cretaceous-Paleogene boundary is a crucial marker in the evolution of life on Earth, as it represents a mass extinction event that was likely triggered by the impact of a large asteroid or comet. This catastrophic event is believed to have caused widespread environmental changes, including climate shifts, volcanic activity, and the collapse of the food chain, which ultimately led to the extinction of the dinosaurs and many other species. The Cretaceous-Paleogene mass extinction paved the way for the rise of mammals and other modern forms of life, demonstrating the significant impact that cosmic events can have on the course of evolution on our planet.
• Describe the evidence that supports the hypothesis that the Cretaceous-Paleogene mass extinction was caused by the impact of a large extraterrestrial object.
  • The leading hypothesis for the cause of the Cretaceous-Paleogene mass extinction is the impact of a large asteroid or comet. This is supported by several lines of evidence, including the presence of a thin layer of clay enriched in the rare metal iridium at the Cretaceous-Paleogene boundary, which is more common in asteroids and comets than in the Earth's crust. Additionally, the discovery of a large impact crater, known as the Chicxulub crater, located off the coast of Mexico's Yucatan Peninsula, provides further evidence for this hypothesis. The Chicxulub crater is dated to the Cretaceous-Paleogene boundary and is believed to be the remnant of the impact that triggered the mass extinction event, leading to widespread environmental changes that ultimately led to the extinction of the dinosaurs and many other species.
• Analyze the long-term implications of the Cretaceous-Paleogene mass extinction on the evolution of life on Earth, particularly in the context of the rise of mammals and other modern forms of life.
  • The Cretaceous-Paleogene mass extinction had profound and far-reaching implications for the evolution of life on Earth. The extinction of the dinosaurs and many other species paved the way for the rise of mammals, which then diversified and evolved into the wide range of species we see today. This transition from the dominance of reptiles to the rise of mammals and other modern forms of life represents a major shift in the course of evolution on our planet. The Cretaceous-Paleogene mass extinction can be seen as a pivotal moment in the history of life, as it opened up new ecological niches and opportunities for the evolution of the mammalian lineage and other modern organisms. This event ultimately shaped the course of life on Earth, leading to the rise of the Cenozoic Era and the emergence of the diverse array of species we observe today.

Related terms

Mass Extinction: A mass extinction is a period of rapid and widespread extinction of species, often caused by dramatic environmental changes or catastrophic events.

Mesozoic Era: The Mesozoic Era, also known as the 'Age of Reptiles,' was a geological era that lasted from approximately 252 to 66 million years ago and was dominated by the rise and eventual extinction of the dinosaurs.

Cenozoic Era: The Cenozoic Era, also known as the 'Age of Mammals,' is the current geological era, which began approximately 66 million years ago and continues to the present day. It is characterized by the rise of mammals and other modern forms of life.