Summary: By Richard I. Gibson Here’s the podcast: Snowball earth is the controversial idea that the Earth was entirely, or almost entirely, covered with ice and snow during three or four periods during the late Proterozoic, from about 650 to 775 million years ago. While there is abundant evidence that can be interpreted to suggest the existence of a snowball earth, much of that evidence can be interpreted in other ways as well. The podcast outlines some of those lines of evidence. Below are some links for further reading. http://www.snowballearth.org http://en.wikipedia.org/wiki/Snowball_Earth http://www.amazon.com/Snowball-Earth-Maverick-Scientist-Catastrophe/dp/1400051258 http://www.sciencedaily.com/releases/2011/10/111012083450.htm Modern glacier photo by Dirk Beyer, under GNU free documentation license.
