A succession of incredibly harsh ice ages waxed and waned during the Cryogenian. It is nicknamed Snowball Earth as it's been suggested that the glaciation was so severe it may even have reached the equator. Life during the Cryogenian consisted of tiny organisms - the microscopic ancestors of fungi, plants, animals and kelps all evolved during this time.
Began: 850 million years ago
Ended: 635 million years ago
During this period the following extinction level events are thought to have occurred.