地质学
Younger Dryas
1.What is the lecture mainly about?
- A. To illustrate similarities between two periods of climate change
- B. To examine theories about the extinction of large North American mammals
- C. To describe how scientists verify occurrences of meteor impacts on Earth
- D. To present a new explanation for the cause of the end of the last ice age
2. What is the professor’s opinion of the claim that cooling during the Younger Dryas caused a major extinction?
- A. It will probably be proven correct by future research
- B. It has been strongly contradicted by recent soil-sample analysis
- C. It seems unlikely in view of what is known about similar climate changes
- D. It is based on a misinterpretation of evidence collected in North Americans
3. Why does the professor mention a meteor that struck Earth during the time of the dinosaurs?
- A. To imply that that meteor impact also affects other large animals in North America
- B. To point out that Earth was often struck by meteors in the past
- C. To explain why scientists hypothesize that a similar impact could have caused a later extinction event
- D. To challenge a commonly accepted claim about dinosaur extinction
4. According to the professor, what is the major significance of the Younger Dryas Boundary?
- A. It provides proof of a sudden climate change.
- B. It lines the inside of a 13,000-year-old impact crater.
- C. It contains valuable information on about the composition of meteors.
- D. It marks the disappearance of large mammal species.
5.The professor mentions that a new group of researchers collected samples from a Younger Dryas Boundary site. How did those researchers explain the high concentration of magnetic particles in the samples?
- A. The Younger Dryas Boundary is especially thick at that site.
- B. The particles were carried to the site by flowing water.
- C. A meteor caused a high concentration of the particles at the site.
- D. Old roofing material had been buried at the site.
6.What opinion does the professor express when he discusses nano-diamonds?
- A. Their presence is not strong proof of a meteor impact
- B. They indicate that a geological sample has been contaminated
- C. Researchers should get a better understanding of their origin
- D. Researchers should focus on magnetic particles instead of nano-diamonds
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