Chicxulub impact

Definition

The Chicxulub impact refers to the event in which a massive asteroid or comet collided with Earth approximately 66 million years ago, creating the Chicxulub crater in present-day Mexico. This catastrophic event is widely believed to have played a crucial role in the mass extinction at the end of the Cretaceous period, leading to the demise of about 75% of Earth's species, including the non-avian dinosaurs. The impact also triggered dramatic environmental changes, reshaping life on Earth and paving the way for the rise of mammals in the ensuing Paleogene period.

5 Must Know Facts For Your Next Test

1. The Chicxulub crater is about 150 kilometers (93 miles) in diameter and was formed by an estimated 10-kilometer-wide asteroid striking Earth at high velocity.
2. Evidence of the impact can be found in geological layers worldwide, including a layer of iridium-rich clay known as the Cretaceous-Paleogene boundary.
3. The environmental effects of the impact included wildfires, tsunamis, and a 'nuclear winter' scenario that drastically altered climate conditions.
4. Many researchers believe that the aftermath of the impact created conditions that favored smaller animals and eventually allowed mammals to thrive after the extinction of dinosaurs.
5. The discovery of the Chicxulub crater in the late 20th century provided strong support for the impact hypothesis, changing our understanding of extinction events.

Review Questions

• How did the Chicxulub impact contribute to environmental changes during the late Cretaceous period?
  • The Chicxulub impact caused significant environmental upheaval by releasing enormous amounts of energy, leading to wildfires, tsunamis, and debris being ejected into the atmosphere. This debris blocked sunlight for an extended period, resulting in a dramatic drop in temperatures and disrupted photosynthesis. These changes created a harsh environment that many species could not survive, contributing to widespread extinctions.
• Discuss how evidence from geological records supports the link between the Chicxulub impact and the Cretaceous-Paleogene extinction.
  • Geological records show a distinct layer at the Cretaceous-Paleogene boundary that contains elevated levels of iridium, a metal commonly found in asteroids. Additionally, shocked quartz and microtektites found in sediment layers indicate a high-energy impact event. The presence of these markers across different locations supports the idea that a global catastrophe, likely due to the Chicxulub impact, played a significant role in causing the mass extinction.
• Evaluate how the understanding of the Chicxulub impact has changed perspectives on extinction events and their causes.
  • The recognition of the Chicxulub impact as a major factor in the Cretaceous-Paleogene extinction has shifted perspectives on how extinction events can be triggered by extraterrestrial phenomena rather than solely by gradual environmental changes. This understanding emphasizes that sudden catastrophic events can have profound effects on biodiversity and ecosystem stability. As research continues to uncover more impacts throughout Earth's history, it highlights how such events could be recurring influences on evolutionary trajectories and biodiversity patterns.

Related terms

Cretaceous-Paleogene Extinction: A major mass extinction event that occurred around 66 million years ago, marking the boundary between the Cretaceous and Paleogene periods, leading to the extinction of numerous species.

Asteroid: A small rocky body that orbits the Sun, which can cause significant damage upon impact with Earth, as seen in the Chicxulub event.

Impact Hypothesis: The theory that links the Chicxulub impact with the mass extinction event, suggesting that environmental changes caused by the impact led to widespread extinctions.