Stories by Paul F. Hoffman and Daniel P. Schrag

>PAUL F. HOFFMAN and DANIEL P. SCHRAG, both at Harvard University, bring complementary expertise to bear on the snowball earth hypothesis. Hoffman is a field geologist who has long studied ancient rocks to unravel the earth's early history. He led the series of expeditions to northwestern Namibia that turned up evidence for Neoproterozoic snowball earth events. Schrag is a geochemical oceanographer who uses the chemical and isotopic variations of coral reefs, deep-sea sediments and carbonate rocks to study climate on timescales ranging from months to millions of years. Together they were able to interpret the geologic and geochemical evidence from Namibia and to explore the implications of a snowball earth and its aftermath.<