Slowdown in plate tectonics may have led to ice sheets.

The article presents the discussion on slabs of old ocean crust falling in slow motion into the mantle separating tectonic plates. Topics include ship-based observations of the alternating magnetic "stripes" resulting as slabs of crust unfurling from the seafloor spreading centers; and assembling a complementary high-resolution record for the Pacific Ocean where seafloor spreading being faster and more complex.