K-Pg Extinction

Definition

The K-Pg extinction, also known as the Cretaceous-Paleogene extinction event, was a major mass extinction that occurred approximately 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 sudden extinction of the non-avian dinosaurs, which profoundly reshaped Earth's biological landscape and allowed for the rise of mammals in the subsequent era.

5 Must Know Facts For Your Next Test

1. The K-Pg extinction is estimated to have wiped out about 75% of all species on Earth, including all non-avian dinosaurs, marine reptiles, and many species of plants.
2. The leading hypothesis for this extinction event is that a 10-kilometer-wide asteroid struck Earth, causing dramatic climate changes and environmental upheaval.
3. Volcanic activity in the Deccan Traps region of present-day India is also thought to have contributed to the extinction by releasing massive amounts of volcanic gases, leading to further climate disruption.
4. Following the K-Pg extinction, mammals began to diversify rapidly, filling ecological niches left vacant by extinct species and eventually leading to the emergence of modern mammalian orders.
5. This extinction event marked a significant transition in Earth’s history, as it set the stage for the Age of Mammals, which continues to this day.

Review Questions

• How did the K-Pg extinction event create opportunities for mammals to evolve and diversify?
  • The K-Pg extinction event eliminated a vast number of dominant species, particularly non-avian dinosaurs. With these large predators and competitors gone, mammals faced fewer challenges in their environment. This lack of competition allowed mammals to occupy diverse ecological niches, leading to rapid evolutionary changes and adaptations that characterized the subsequent Age of Mammals.
• Discuss the evidence supporting both asteroid impact and volcanic activity as causes for the K-Pg extinction. How do these events interrelate?
  • Evidence supporting the asteroid impact includes the Chicxulub Crater and the presence of an iridium layer in geological records. On the other hand, volcanic activity from the Deccan Traps released sulfur and carbon dioxide, contributing to climate change. Some scientists argue that these two catastrophic events occurred around the same time and may have acted synergistically, with volcanic eruptions exacerbating the environmental stresses initiated by the asteroid impact.
• Evaluate the long-term effects of the K-Pg extinction on mammalian evolution and biodiversity across subsequent geological periods.
  • The K-Pg extinction had profound long-term effects on mammalian evolution by allowing them to fill niches previously occupied by dinosaurs. This adaptive radiation led to increased diversity among mammals during the Paleogene period. Over millions of years following this event, mammals evolved into various forms, including primates, cetaceans, and large herbivores. This diversification set important evolutionary trends that shaped modern ecosystems and established mammalian dominance during subsequent epochs.

Related terms

Chicxulub Crater:

A large impact crater located on the Yucatán Peninsula in Mexico, believed to be the site of the asteroid impact that triggered the K-Pg extinction.

Iridium Layer:

A global layer of sediment rich in iridium found in rock layers from around the time of the K-Pg extinction, providing evidence for an extraterrestrial impact.

Adaptive Radiation:

The rapid evolution of diversely adapted species from a common ancestor, often occurring after mass extinctions when ecological niches become available.