Researchers analyzing high-altitude bristlecone pine growth rings in the White Mountains observed a sudden, sharp contraction in tree-ring width dating precisely to 536 CE. Historical records from the Mediterranean basin during the same decade describe several years of dimmed sunlight and summer frosts. The researchers concluded that a major volcanic eruption in 536 CE ejected massive sulfate aerosols into the stratosphere, blocking solar radiation and causing global cooling that restricted tree growth. Which of the following, if true, provides the strongest support for the researchers' conclusion?
- AModern volcanic eruptions emitting similar volumes of sulfur dioxide produce atmospheric cooling effects that typically abate within two to three years.
- Polar ice core samples retrieved from layers dated to 536 CE contain unprecedentedly high concentrations of atmospheric volcanic sulfate deposits.Cevap
- CBristlecone pines at lower elevations in the same mountain range exhibited normal growth ring expansion throughout the decade starting in 536 CE.
- DA severe regional drought affected the southwestern North American continent during the middle of the sixth century.
- EMediterranean historical records from the late sixth century report a gradual recovery of crop yields across the region.
Cevap
The correct answer is the option stating that polar ice core samples from 536 CE contain unprecedentedly high concentrations of atmospheric volcanic sulfate deposits.
The correct answer provides direct physical proof of massive atmospheric volcanic aerosols precisely in 536 CE from independent ice core data. This strongly reinforces the conclusion that a volcanic eruption was the cause of both the Mediterranean atmospheric phenomenon and the tree-ring growth contraction.
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Strengthening Causal Claims via Independent Physical Corroboration
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