Paleoclimatologist: Stalagmites from the Kavir Cave system exhibit a sharp twenty percent decrease in oxygen-18 isotope ratios approximately 4,200 years ago, a geochemical pattern commonly associated with intensified monsoonal rainfall. Because archaeological surveys show that agrarian settlements in the adjacent valley were abruptly deserted during this precise fifty-year window, catastrophic regional flooding from torrential rains must have driven the inhabitants to abandon their communities.
Statement: The argument's conclusion is significantly undermined if the oxygen-18 ratio in regional cave dripwaters is primarily determined by atmospheric moisture source trajectories rather than the volume of local precipitation.
Answer: Answer
Answer
True, because demonstrating that the isotopic shift reflects wind and moisture trajectories rather than rainfall volume removes the evidentiary basis for the claim that catastrophic flooding caused the valley's abandonment.
The author builds a causal argument attributing settlement abandonment to severe flooding, based solely on a drop in oxygen-18 isotopes that is 'commonly associated' with heavy rain. The statement identifies an alternative driver for the isotopic anomaly (shifting moisture source trajectories). If true, this alternate explanation decouples the isotope data from rainfall volume, removing the sole support for the flooding hypothesis and significantly weakening the conclusion.
Step-by-Step Solution
Key Concept
Undermining causal inferences based on proxy data by providing alternative causal mechanisms
Estimated Time:1m 30s