K-Pg Boundary

Definition

The K-Pg boundary, or Cretaceous-Paleogene boundary, marks a significant geological layer that indicates the transition from the Cretaceous period to the Paleogene period approximately 66 million years ago. This boundary is most famous for its association with one of the largest mass extinction events in Earth’s history, leading to the extinction of about 75% of all species, including the dinosaurs. It serves as a crucial point for understanding both the causes and effects of mass extinction events in Earth's history.

5 Must Know Facts For Your Next Test

1. The K-Pg boundary is characterized by a distinct layer of sediment that shows a significant change in fossil types before and after this point, indicating major ecological shifts.
2. The most widely accepted cause of the mass extinction at the K-Pg boundary is a combination of an asteroid impact and extensive volcanic activity, leading to climate changes.
3. This boundary is located in various places around the world, with notable sites in Italy, Mexico, and Denmark where it has been extensively studied.
4. The K-Pg boundary not only marks the end of dinosaurs but also led to the rise of mammals and birds as dominant life forms in the subsequent Paleogene period.
5. Research into the K-Pg boundary has provided crucial insights into how life can rapidly adapt or fail to survive under sudden environmental changes.

Review Questions

• How does the K-Pg boundary serve as a marker for understanding mass extinction events in Earth's history?
  • The K-Pg boundary serves as a critical geological marker that highlights one of Earth's most significant mass extinction events. It provides evidence of dramatic ecological changes through fossil records and sediment layers. The stark difference in species diversity before and after this boundary allows scientists to study how sudden environmental changes can lead to widespread extinctions.
• Discuss the evidence that supports the asteroid impact hypothesis related to the K-Pg boundary.
  • Evidence supporting the asteroid impact hypothesis includes the presence of a layer enriched with iridium found at the K-Pg boundary, which is rare on Earth's surface but common in asteroids. Additionally, the Chicxulub crater aligns with the timing of the extinction event, showing signs of massive energy release and subsequent environmental disruption. Together, these pieces of evidence suggest a direct link between an extraterrestrial impact and the mass extinction that occurred at this boundary.
• Evaluate the long-term ecological consequences of the K-Pg boundary event on subsequent evolutionary patterns.
  • The K-Pg boundary event had profound long-term ecological consequences that reshaped life on Earth. After this mass extinction, mammals began to diversify and occupy ecological niches previously held by dinosaurs, leading to their dominance in many environments. This shift also allowed for significant evolutionary developments, including adaptations in flight among birds and various mammalian forms. Understanding these patterns helps illustrate how catastrophic events can dramatically alter evolutionary trajectories and influence biodiversity for millions of years.

Related terms

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

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

Iridium Anomaly: A layer rich in iridium found at the K-Pg boundary, which supports the theory of an extraterrestrial impact causing the mass extinction event.