The idea that the Earth has been completely frozen over by ice and snow might seem fanciful and deeply worrying, if true. Gabrielle Walker's Snowball Earth
is the remarkable story of the theory, the evidence for it, the geologists who are behind it and those against it. The bad news is that it is highly likely to be true. As Gabrielle Walker expertly explains for the general reader, there have indeed been several such runaway glacial events. Polar ice caps, continental ice sheets and sea ice grew to such an extent that they all met in the tropics and our green and pleasant planet was whited out.
The good news is that it all happened a very long time ago, the last time around 650 million years ago and is highly unlikely to happen again, even in the distant future. Snowball Earth theory has been gathering strength over the last few decades and is one of the most remarkable discoveries in Earth science at the end of the last century. You might wonder why such major Earth encompassing and catastrophic events have gone unnoticed for so long. Well, it is a complicated and interesting story and Gabrielle Walker is well qualified to tell it as she has a science doctorate and has worked as an editor for Nature and New Scientist, so she has seen this idea grow over the years. More importantly, as she acknowledges has been a Snowball Earth groupie attending conferences, field trips, lectures and campsites around the world. Consequently, she has been at the coal face, seen the critical rocks which are now scattered around the world, thanks to an ongoing process known as plate tectonics which opens and closes oceans and shuffles the continents about. Walker has talked to the scientists involved about the evidence and the problems of their interpretation, so we hear directly from the mouths of the various horses. It's a fascinating story, well told and there are notes and further reading for those that want more details and a very useful index. --Douglas Palmer
"Walker does a superb job ...Her prose, like her story, is likely to engage both scientists and general readers equally." -- Publishers Weekly, Janury 20th 2003