New geological research has confirmed the theory that Earth went through a phase of extreme cooling some 717 million years ago, with all, absolutely all the oceans covered in ice, at least seasonally, as well as the land. This extreme ice age is known technically as the Sturtian glaciation.
This mountain, now at Yukon, was once a tropical coral reef (light grey area) and shows cover by glaciar deposits (darker top).
However there is some discussion on how could life survive such extreme circumstances, more so when it's the period when the earliest animals are thought to have appeared first. It is possible that even in such extreme conditions, there would be seasonal patches of open water allowing for photosynthesis. Another possibility is that this early life was in fact adapted to hydrothermal vents in the deep ocean, not needing of solar input (extremophiles).
Was Earth once like Enceladus?
Source: Science Daily.