A Cool Early Earth? (Scientific American)
John W. Valley October 2005 Scientific American October 2005, p/ 58-65
This Scientific American article is a student-friendly version of the 2002 Valley et al paper describing 4.4 billion year old zircons and their significance. This article presents a very readable story of the discovery of the zircon grains in Western Australia, the analysis of their remarkably old ages, and the significance of the zircon geochemistry. The implication is that these mineral grains formed in a relatively cool, water-rich environment near the earth’s surface, which means that these clement conditions occurred much earlier than previously thought. This article would be especially useful for introducing students to the topics of zircons and the early earth history.