Temperature: 5–45 °C
Atmospheric oxygen: 0–12%

Proterozoic Eon – the third large eon, which covers times just before the proliferation of complex life on Earth. The most important events of this time were the transition to an oxygenated atmosphere, several global glaciations (the Snowball Earth hypothesis), and the evolution of soft-bodied, multicellular organisms.
This is a hypothetical reconstruction of a Snowball Earth during the Huronian and Cryogenian glaciations.