Two scientists discuss the cause of the Cretaceous-Paleogene (K-Pg) mass extinction 66 million years ago.
Scientist 1
The K-Pg extinction was caused by a large asteroid impact. This impact released a massive dust cloud that blocked sunlight, causing rapid global cooling and halting photosynthesis. The global iridium layer found at the K-Pg boundary is evidence of this asteroid, as asteroids are rich in iridium.
Scientist 2
The K-Pg extinction was caused by massive volcanic eruptions of the Deccan Traps. These eruptions released volcanic dust and sulfur dioxide that blocked sunlight, leading to global cooling. The iridium layer at the K-Pg boundary was deposited by volcanoes, as iridium is brought up from Earth's deep mantle during major eruptions.
Match each scientific statement with the corresponding viewpoint or hypothesis description.
- An asteroid impact was the primary trigger of the K-Pg mass extinction.Supported only by Scientist 1's impact hypothesis.
- Volcanic eruptions of the Deccan Traps were the primary trigger of the K-Pg mass extinction.Supported only by Scientist 2's volcanic hypothesis.
- The K-Pg boundary iridium layer originated from an extraterrestrial source.Attributed to an asteroid by Scientist 1.
- The K-Pg boundary iridium layer originated from Earth's interior.Attributed to Earth's mantle by Scientist 2.