At least twice in Earth’s history, nearly the entire planet was encased in a sheet of snow and ice. These dramatic “Snowball Earth” events occurred in quick succession, somewhere around 700 million years ago, and evidence suggests that the consecutive global ice ages set the stage for the subsequent explosion of complex, multicellular life on Earth. Scientists have considered multiple scenarios for what may have tipped the planet into each ice age. While no single driving process has been identified, it’s assumed that whatever triggered the temporary freeze-overs must have…
