Earth's sea floor is created along great volcanic ridges that spread at rates of a few centimeters per year beneath every ocean basin. The volcanic and tectonic processes at these mid-ocean ridges ultimately determine the characteristics of the sea floor and the oceanic crust beneath it. These processes occur beneath several kilometers of rock and seawater, seemingly far removed from climatic variations above sea level. Thus, it is surprising that both Crowley et al. (1), on page 1237 in this issue, and Tolstoy (2) found ice age periodicity in hilly topography on the flanks of ridges submerged beneath the Southern and Pacific Oceans. |
