Question

In 1864, the self-taught Scottish polymath James Croll proposed that cyclical variations in Earth’s orbital eccentricity, combined with the precession of the equinoxes, altered seasonal insolation levels sufficiently to trigger prolonged periods of hemispheric glaciation. Croll posited that ice ages occurred not when winters were coldest, but when winters coincided with aphelion during periods of maximum eccentricity, accumulating snowpack that persisted through cooler, less intense summers. Crucially, Croll’s mechanism required that glaciation alternate asynchronously between the Northern and Southern Hemispheres. While nineteenth-century uniformitarian geologists initially welcomed Croll’s hypothesis because it provided a physical timeline that seemed to confirm their belief in Earth's immense antiquity, the model soon encountered profound empirical resistance. Stratigraphic investigations of interglacial peat beds and erratic boulder drifts across Northern Europe and North America revealed multiple synchronized glacial retreats and advances, rather than the hemispheric alternation Croll’s orbital calculations dictated. Furthermore, physical geologists calculated that ocean currents, such as the Gulf Stream, would redistribute thermal energy rapidly enough to mitigate Croll's predicted insolation deficits. Consequently, by the late nineteenth century, Croll's astronomical framework was largely abandoned in favor of terrestrial explanations—such as shifts in atmospheric carbon dioxide or crustal uplift—only to be revived and mathematically refined decades later by Milutin Milankovitch.

Which of the following inferences regarding nineteenth-century geological thought is supported by the passage? Select all that apply.