INTRODUCTION xi Introduction Civilization occurs by geological consent subject to change without notice Will Durant (1885 1981) Richard de Bury, Bishop of Durham from 1333 to 1345, divided all knowledge into ‘Geologia’, earthly knowledge, and ‘Theologia’, heavenly knowledge By the beginning of the last century, however, Geology was generally understood to be restricted to the study of rocks: according to the old dictum of the Geological Survey of Great Britain ‘If you can hit it with a hammer, then it’s geology.’ Subsequently geology has been subsumed into Earth Science This includes not only the study of rocks (the lithosphere), but also the atmosphere and hydrosphere and their relationship with the biosphere Presently these relationships now form a nexus in Earth System Science The ‘Encyclopedia of Geology’ is what it says on the cover What appealed to us when first approached to edit this work by Academic Press was a request that the encyclopedia should be rock-based Readers are referred to the companion volumes, Encyclopedia of Atmospheric Sciences, Encyclopedia of the Solar System, Encyclopedia of Soils in the Environment and Encyclopedia of Ocean Sciences for knowledge on the other branches of Earth Science Nonetheless we have extended our brief to include articles on the other planets and rocky detritus of our solar system, leaving others to argue, as no doubt Bishop Richard would have done, where the boundaries of earthly and heavenly knowledge might be (His Grace would probably have charged the editors of the Encyclopedia of the Solar System with heresy.) One of the first, and most difficult, tasks of editing this encyclopedia was to decide, not only which topics merited articles, but also how these articles should be grouped to facilitate the reader This is easy for some branches of geology, but difficult for others It is relatively easy to logically arrange articles on mineralogy and palaeontology, since they are defined by their chemistry and evolutionary biology Articles that describe Earth history may be conveniently arranged in a chronological order, and articles on regional geology may be presented geographically Other topics present problems, particularly in the area of sedimentology There is, for example, a range of inter-related topics associated with deserts This area could be described geomorphologically, and in terms of the aeolian and aqueous processes of deserts, aeolian sedimentary structures, and aeolian deposits All of these aspects of deserts deserve mention, but there is no obvious logical way of arranging the discrete topics into articles To help us in this task we relied heavily on our editorial board, whose individual members had more specialized knowledge of their field than we To the Editorial Board Members, authors and anonymous referees of each article we give heartfelt thanks We were also, of course, constrained by the willingness of expert authorities to contribute articles To some degree therefore, the shape of the encylopedia owes as much to the enthusiasm of experts to write for us, as for our ‘wish list’ of articles To facilitate readers finding their way around the Encyclopedia of Geology great care has been taken in crossreferencing within and between articles, in providing ‘See Also’ lists at the end of articles, and in the index No doubt it will be easier for readers to navigate around the online version of the work, than to manipulate the several hard copy volumes As geological knowledge expands there is always more to learn and understand While preparing the ‘Encyclopedia of Geology’ we have ourselves learned a great deal about geology, both within and beyond our own specialties We invite you to read this encyclopedia and join us in the field trip of a lifetime Richard C Selley L Robin M Cocks Ian R Plimer August 2004 References to related encyclopedia published by Elsevier, Academic Press: Encyclopedia of the Solar System, 1998 Encyclopedia of Ocean Sciences, 2001 Encyclopedia of Atmospheric Sciences, 2002 Encyclopedia of Soils in the Environment, 2005