Question

Explain one hypothesis about why dinosaurs might have become extinct.

Short answer

An asteroid impact around 66 million years ago likely caused climate changes that led to dinosaur extinction.

Step-by-step solution

Introduction to the Hypothesis

There are several hypotheses about the extinction of dinosaurs, but one of the most prominent ones is the asteroid impact hypothesis. This hypothesis suggests that a massive asteroid or comet hit the Earth around 66 million years ago, leading to the dinosaurs' extinction.

Evidence for the Asteroid Impact

Support for the asteroid impact hypothesis comes from the discovery of a layer of iridium-rich ash in the geologic boundary known as the Cretaceous-Paleogene (K-Pg) boundary. Iridium is rare on Earth's crust but abundant in asteroids, suggesting an extraterrestrial source.

Consequences of the Impact

The impact likely caused dramatic climate changes. It is believed to have released particles and gases into the atmosphere, blocking sunlight, and leading to a significant decrease in temperatures worldwide. This would disrupt photosynthesis and lead to a collapse of ecosystems.

Supporting Evidence from the Chicxulub Crater

Additional support comes from the discovery of the Chicxulub Crater in the Yucatan Peninsula, which dates back to around the same time as the K-Pg boundary. The size and age of the crater coincide with the predicted time of the dinosaurs' extinction, supporting the impact hypothesis.

Key concepts

Asteroid Impact Hypothesis

Among the various theories that attempt to explain the extinction of dinosaurs, the asteroid impact hypothesis stands as one of the most widely accepted. This hypothesis posits that a massive asteroid or comet collided with Earth approximately 66 million years ago. The impact is hypothesized to have caused catastrophic environmental changes. The aftermath would have drastically altered the planet's climate and ecology. These changes were likely severe enough to lead to the widespread extinction of not only dinosaurs but many other forms of life as well. This theory is supported by a range of geological and scientific evidence, making it a central point of discussion in paleontology and earth science.

Cretaceous-Paleogene Boundary

The Cretaceous-Paleogene (K-Pg) boundary represents a pivotal moment in Earth's geological timeline. Spanning approximately 66 million years ago, it marks the division between the Cretaceous and Paleogene periods. This boundary is significant because it coincides with one of the largest mass extinctions in Earth's history. The geological record shows a distinct layer of sediment that is present worldwide, indicating a global event. Scientists have found that the layer corresponds with the timing of the mass extinction, making it an essential piece of the puzzle in understanding the dinosaurs' demise. The K-Pg boundary layer serves as a timeline marker, offering a snapshot of the mass extinction's impact.

Chicxulub Crater

The Chicxulub Crater is a massive impact crater located on the Yucatan Peninsula in Mexico. It measures about 150 kilometers in diameter and is believed to date back approximately 66 million years. This time frame aligns with the K-Pg boundary and the extinction of the dinosaurs, presenting a strong piece of evidence for the asteroid impact hypothesis. Researchers have studied the crater extensively, uncovering data about its size and the force of the impact. This information has led to a greater understanding of how such an event could have contributed to massive climate changes and subsequent extinction events on a global scale. The Chicxulub Crater is thus a vital link in the asteroid impact narrative.

Iridium-rich Layer

The finding of an iridium-rich layer in the Earth's geologic record provides compelling evidence supporting the asteroid impact hypothesis. Iridium is an element that is typically rare in the Earth's crust but is common in asteroids and comets. This layer, found at the K-Pg boundary, suggests an extraterrestrial source of iridium. Its presence globally signifies a massive dispersal of material, likely from an impact event. Scientists have used the iridium layer to trace the scale and potential impact of such an event, offering insights into how it could have triggered the widespread extinctions observed at the boundary. Understanding this layer has been crucial in linking the asteroid impact to the extinction event of the dinosaurs.