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.

Thomas H. Clark (1893-1996) was a professor in the Department of Geological Sciences, McGill University, Montreal.

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