For decades, geologists attributed the sudden cooling event known as the Younger Dryas exclusively to the catastrophic drainage of glacial Lake Agassiz into the North Atlantic, which purportedly disrupted the ocean overturning circulation. However, recent high-resolution isotopic analyses of Greenland ice cores suggest that the onset of this cooling preceded the lake's outburst by nearly two centuries. To reconcile this chronological discrepancy, some researchers propose that an atmospheric dust surge, rather than a meltwater pulse, served as the primary initial trigger. By scattering incoming solar radiation, volcanic aerosols or impact ejecta could have initiated regional cooling prior to any major hydrodynamic disruption. Consequently, while the drainage of Lake Agassiz undoubtedly prolonged the cold spell, its role is increasingly viewed as secondary rather than initiating.
Which of the following statements correctly describe the rhetorical function of specific elements within the passage? Select all that apply.
- The phrase beginning with 'However, recent high-resolution isotopic analyses...' introduces empirical findings that challenge a traditional causal explanation.Cevap
- BThe reference to 'volcanic aerosols or impact ejecta' serves to prove conclusively that Lake Agassiz played no part in late-glacial climate changes.
- The final sentence beginning with 'Consequently, while the drainage...' functions to reevaluate the structural role of a previously emphasized factor.Cevap
- DThe opening sentence expresses the main thesis that the author defends throughout the remainder of the passage.
- EThe mention of an 'atmospheric dust surge' is presented as an established historical fact that resolves all paleoclimate debates.