Mirovia

Mirovia (from Russian мировой, mirovoy, meaning "global") was an hypothesized paleo-ocean which may have been a global ocean that surrounded the supercontinent Rodinia in the Neoproterozoic Era, about 1 billion to 750 million years ago. The Mirovia may be essentially identical to, or the precursor of, the hypothesized Pan-African Ocean which followed the rifting of Rodinia. The Panthalassa (proto-Pacific Ocean) developed in the Neoproterozoic Era at the expense by subduction of the global Mirovia.

Geologic evidence suggests that the middle Neoproterozoic, the Cryogenian period, was an extreme ice age so intense that Mirovia may have been completely frozen to a depth of 2 kilometers. This is the Snowball Earth hypothesis.