The years between 662 million years and 700 million years ago — just before and after glaciers left a half-mile thick rock layer — were mysterious.
There is little information about the planet's conditions just before the period of the deep freeze, which covered the planet in ice and is sometimes referred to as Snowball Earth.
Now, researchers have examined a rock feature showing what life on the planet was like — both before the freeze and after the subsequent thaw. The report in the Journal of the Geological Society of London shows how those events may have given rise to complex life forms.
