Phil Kearey was Senior Lecturer in Applied Geophysics in the Department of Earth Sciences at Bristol University, U.K. prior to his premature death in 2003. In his research he used various types of geophysical data, but gravity and magnetic data in particular, to elucidate crustal structure in the eastern Caribbean, Canadian shield and southern England. Keith Klepeis is a Professor in the Department of Geology at the University of Vermont, U.S.A. He specializes in the areas of structural geology and continental tectonics and has worked extensively on the evolution of orogenic belts and fault systems in New Zealand, Patagonia, West Antarctica, Australia, British Columbia and southeast Alaska. Fred Vine is an Emeritus Professor in the School of Environmental Sciences at the University of East Anglia, Norwich, U.K. He was made a Fellow of the Royal Society of London and has received numerous awards for work on the interpretation of oceanic magnetic anomalies and ophiolites, fragments of oceanic crust thrust up on land, in terms of sea floor spreading.