Published by the American Geophysical Union as part of the Special Publications Series, Volume 6.During the decade of the 1960s, science of the solid earth underwent an astonishing and awesome upheaval. In just a few years, geoscientists constructed a new way of describing and understanding the dynamics of everchanging earth, past and present, and so found a route to explanation for how most, if not all, of the great features of the earth"s surface that have harbored and plagued and enchanted humans throughout their existence came to be. Continents, ocean basins, mountain ranges, deep sea trenches, earthquakes, and volcanoes suddenly became explicable as consequences of earth movements that, on a global scale, have a remarkably simple and readily understandable pattern. The long-sought key to the ponderous and agonizingly slow movements of earth that, over millennia, have deftly shaped our surroundings was found during that decade, or so most scientists think today, more than a quarter of a century later.