Snowball Earth by Gabrielle Walker, Bloomsbury, ISBN 074756051X, £16.99
WAS our blue planet once a glistening, glacially white “snowball Earth” covered – entirely covered – with snow and ice? The idea seems ridiculously improbable, judging by present-day conditions. But, as Â鶹´«Ã½ consultant Gabrielle Walker ably shows in this fascinating account, one of the great attractions of the rock record is that it provides evidence that a variety of absurd events really have taken place during our planet’s 4.55-billion-year career. There is evidence for at least one snowball Earth event, though fortunately for us such big freezes are very rare and, on present evidence, are confined to Precambrian time over 590 million…
