Whats hot on Snowball Earth?
A paper published by Science on 2 January 2009 (Bao et al., 2009) is the latest and perhaps most significant development in Ian Fairchild’s collaborative research over the past 30 years on Precambrian ice ages and their associated carbonate rocks. The paper comes up with a new line of evidence to support a key, but counter-intuitive prediction of Snowball Earth theory: that carbon dioxide levels were high in the Earth’s atmosphere during an ancient ice age. During a Snowball event you can think of the Earth as being like a baked Alaska pudding – hot on the outside surrounding a cold middle (ice-cream in the case of the pudding). This strange situation arises if the Earth is largely covered in ice and snow in contact with an atmosphere rich in greenhouse gases in which heat is trapped. The covering of ice and snow stops rocks being weathered by carbon dioxide: weathering is the key process that uses up this gas which is continuously released into the atmosphere from volcanoes. So, durin
