Cretaceous extinction... The evidence tells you that “overwhelming evidence suggests that the extinction was caused by a 10-km-diameter asteroid that struck Earth.” Suggest at least three lines of evidence that might have led scientists to this conclusion.
Could you please help me with this problem..? I can't find three lines of evidence...
Certainly! Here are three lines of evidence that suggest the Cretaceous extinction was caused by a 10-km-diameter asteroid impact:
1. Chicxulub Crater: One of the most compelling pieces of evidence is the discovery of the Chicxulub Crater. This large impact crater is located in the Yucatán Peninsula in Mexico and has been dated to approximately 66 million years ago, which aligns with the timing of the Cretaceous extinction. The size and age of the crater provide strong support for a catastrophic impact event.
2. Global Layer of Impact Debris: Another piece of evidence is the presence of a distinct layer of impact debris found globally within sedimentary rocks from the boundary of the Cretaceous and the Paleogene periods. This layer, known as the K-Pg boundary, contains high levels of the element iridium, which is rare on Earth's surface but abundant in asteroids. The presence of this iridium-enriched layer supports the hypothesis of an asteroid impact as the cause of the extinction.
3. Shocked Quartz and Impact Melt Rocks: Scientists have also discovered shocked quartz grains and impact melt rocks in sediments around the world at the K-Pg boundary. Shocked quartz is formed by the intense pressure and heat generated during an impact, while impact melt rocks occur when the impact energy melts and solidifies surrounding rocks. The presence of these distinctive features provides further evidence of a large-scale impact event during the Cretaceous extinction.
These lines of evidence, along with others, have led scientists to conclude that a 10-km-diameter asteroid impact played a significant role in the mass extinction event that occurred at the end of the Cretaceous period.
Sure! To find three lines of evidence supporting the conclusion that a 10-km-diameter asteroid caused the Cretaceous extinction, you can explore the scientific research and findings related to this hypothesis. Here are three lines of evidence that have supported the asteroid impact theory:
1. Global Distribution of Impact Ejecta: Scientists have discovered a widespread layer of debris called the "K-Pg boundary layer" found in rock formations around the world at the boundary between the Cretaceous and Paleogene geological periods. This layer contains a unique chemical signature and is rich in a variety of elements, including iridium, which is rare in Earth's crust but abundant in asteroids. The occurrence of this layer globally points to a massive impact event as the cause of its deposition.
2. Impact Crater: The presence of a large impact crater known as the Chicxulub crater, located off the Yucatan Peninsula in Mexico, provides further evidence. The crater, which is approximately 180 km in diameter, matches the estimated size of the impacting asteroid. It was discovered using geophysical techniques, such as gravity and magnetic anomaly surveys, as well as drilling samples from the region.
3. Fossil Record and Extinction Patterns: Studies of the fossil record indicate a major extinction event at the K-Pg boundary, with numerous species of plants and animals disappearing abruptly. Additionally, the patterns of extinction observed are consistent with the immediate environmental impact of a large asteroid impact, such as widespread fires, tsunamis, and global climate disruption due to the injection of huge amounts of dust and debris into the atmosphere.
By considering these lines of evidence collectively, scientists have found strong support for the hypothesis that a 10-km-diameter asteroid impact played a significant role in the Cretaceous extinction event.