In the early nineteenth century, geologists attempting to account for 'erratic' boulders—massive granite blocks deposited miles from their bedrock origins across Northern Europe—predominantly attributed their displacement to catastrophic marine deluges carrying iceberg-laden debris. This iceberg drift hypothesis aligned neatly with the prevailing diluvial framework without requiring radical revisions to historical climate models. When Louis Agassiz proposed in 1837 that vast, continuous ice sheets had once carpeted temperate latitudes, his continental glaciation theory was initially dismissed by contemporaries as a fanciful extrapolation. Opponents argued that ice, lacking fluidity, could not exert sufficient lateral displacement over thousands of miles. Agassiz countered not by introducing new empirical specimens, but by reinterpreting existing morphological signatures: he demonstrated that the linear striations etched into bedrock under erratic boulders matched the grinding dynamics observed in active Alpine glaciers, rather than the randomized scouring produced by floating icebergs. Consequently, the eventual acceptance of Agassiz’s model hinged less on discovering unobserved geological artifacts than on demonstrating that recognized physical evidence was incompatible with the hydrodynamic assumptions of the drift model.
Which of the following can be inferred from the passage regarding the geological evidence cited in the debate over erratic boulders?
- AEarly nineteenth-century geologists overwhelmingly rejected diluvial frameworks due to their fundamental incompatibility with historical climate models.
- BAgassiz introduced newly excavated granite specimens from the Alps to demonstrate the specific grinding dynamics of continental ice sheets.
- The physical features Agassiz referenced to support his hypothesis were already recognized by geologists prior to his formulation of the continental glaciation theory.Answer
- DProponents of the iceberg drift theory eventually conceded that ice sheets possessed fluid properties capable of moving boulders across continents.
- EThe debate surrounding erratic boulder displacement was settled primarily by examining the randomized scouring patterns produced by icebergs in marine environments.