Abstract

Snowball Earth provides a wonderful case history of the complex ways in which science advances. A data-driven, somewhat inductive understanding of widespread Neoproterozoic glaciation was championed by Cambridge’s Brian Harland in the 1960s and he later facilitated relevant work in Svalbard and Greenland by Hambrey and Fairchild. Then in the late 1990s, the model-driven Snowball Earth theory exploded on the scene, becoming vigorously championed by Paul Hoffman and linked to his unrivalled field experience. The theory encouraged hypothesis-testing which guided some subsequent developments. The aspects of the theory that still stand are that glaciations were necessarily prolonged (millions of years in duration) and synchronous, that a hydrological hiatus associated with a deep-frozen state is associated with an unconformity, that atmospheric PCO ¬2 became very high during glaciation and the associated glacial sediments were deposited during the final stages of the panglaciation. The events immediately following deglaciation are still hotly disputed. Neoproterozoic glaciation and associated carbonates will be illustrated with field, petrological and geochemical data, mainly from Svalbard and Scotland. The research that has resulted from the stimulus of Snowball theory is salutary in warning us that extreme climate states, inimical to human civilization, have occurred in the past, and hence that there are dangers in the use of technology, such as shielding the sun with aerosols, to fix our current climate crisis.