Mountain ranges are the most conspicuous elements of the earth's architecture, and the manner in which the architectural units are arranged or disarranged has become the study of a subdivision of geology known as Tectonics. A hundred years ago James Hall attempted the first scientific synthesis of the steps in the building of the eastern North American mountains, the Appalachians. His initial hypothesis of 1857, expanded and broadened by J.D. Dana during the decade which followed, laid the foundation for our modern geosynclinal theory of mountain building. During the last century of modifications and refinements were contributed concerning the roles played by crustal compression, sub-crustal convection currents, batholiths, metamorphism, gravity sliding, and isostasy. In recent years detailed mapping, supplemented by studies of turbidity currents, paleomagentism, stable isotopes, and radio-activity have helped to unravel the history of mountain building, but today there are as many questions unanswered as there are those for which there are tentative solutions.Aspects of Appalachian orogeny was a suitable subject for the symposium of the Royal Society of Canada Annual Meeting in 1966 at Sherbrooke, Quebec—a city within the Appalachian Mountain System. This book assembles the papers of this symposium, dealing with gravity sliding, studies of sedimentation and structure in limited areas, comparisons with the Appalachians of the United States, the bearing of gravity measurements upon our understanding of mountain structure, earthquakes, and a broad, general view of the tectonic pattern of the earth of which this mountain-built belt is but a small part.Such a comprehensive volume, bringing together a variety of points of view of some of the foremost scholars in the field, indicates the vastness of the subject, the significant progress made thus far, the necessity for new and progressive methods of exploration, and above all the interdependence of all the workers in the field, no matter how seemingly unrelated their specialities are.
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