"Snowball Earth" they believe is connected to the break-up of Rodinia and that it caused an emergence of animals. Even during the "Snowball Earth" scientists believe now that there was still some life forms. They saw that the seafloor springs supported microbes that thrive on chemicals rather than sunlight. So the cold-living organisms would of survived. Cyanobacteria and certain kinds of algae occupy habitats such as snow, porous rock and the surfaces of dust particles encased in floating ice.

Now that the Earth was completely covered in ice, you're probably asking well how does the Earth unfreeze? A paleomagnetologist, Joseph Kirschvink came up with the idea of a "super-massive Greenhouse Effect". Even if the Earth were covered with ice, underwater volcanoes would still poke their hot heads through the ice cover. They would let out carbon dioxide from the molten rocks below, and gradually the carbon dioxide from the volcanoes would build up because there was no way for it to leave. As the carbon dioxide built up, there became so much that is set off a gradual Greenhouse Effect that began to warm up the Earth and the ice melted. Today you wouldn't have to worry about another "Snowball Earth" because it's a long time before the continents cluster again, and the sun is gradually warming up, which means there's no way that the ice would be able to form as it did 700 million years ago.