Special Paper 500, The Web of Geological Sciences: Advances, Impacts, and Implications, is a wonderful assemblage of papers written to show advances in our science over the past 50 years in celebration of the 125th anniversary of the founding of the Geological Society of America. However, it is clear that a number of important sub-disciplines were not represented. Partly this resulted from the “scientific myopia” of the editor (me!), and partly it resulted from the inability of several authors to complete their promised chapters. This new Special Paper is intended to rectify, at least in part, those omissions. As conceived, it was to include several new papers, but—alas—only three were completed. However, the three are quite outstanding, and will be welcome additions to the literature.
In Chapter 1, “Earth’s dynamic surface: A perspective on the past 50 years in geomorphology,” Ellen Wohl, Paul Bierman, and David Montgomery have provided an elegant overview of profound changes in the field. In their introduction, the authors state:
This paper provides an overview of changes in the study of surface processes and landforms on Earth and other planets during the past half century. The discipline of geomorphology has undergone transformative changes during this period, partly as a result of the development of several categories of new tools that have changed the questions that geomorphologists can ask and the methods that they can use to answer those questions.
Indeed, they have done just that, providing such diverse discussions as the role of geomorphic science to society; the development of new tools, such as remote sensing methods and GPS technology; the use of isotope methods, such as cosmogenic isotopes and the application of thermochronology; the development of computational models; and the study of the geomorphology of other planets.
In Chapter 2, “The metamorphosis of metamorphic petrology,” Frank Spear, David Pattison, and John Cheney have reviewed the remarkable changes that have occurred in this complex discipline over the past 50 years. In their introductory statement they state:
The past half-century has seen an explosion in the breadth and depth of studies of metamorphic terranes and of the processes that shaped them. These developments have come from a number of different disciplines and have culminated in an unprecedented understanding of the phase equilibria of natural systems, the mechanisms and rates of metamorphic processes, the relationship between lithospheric tectonics and metamorphism, and the evolution of the Earth’s crust and lithosphere.
These distinguished authors have written a lucid account of many complex developments in their discipline. These include a historical overview; the contributions of thermodynamics; the impact of plate tectonics; and the stunning effect of the availability of high-speed computing. Additional topics include, to name only a few, the golden age of experimental studies (1960s to 1980s); the development of fO2-T equilibria; the development of geothermometry and geobarometry; activity models for metamorphic phases; and the importance of thermodynamics and heterogeneous equilibria.
In Chapter 3, “The Archean–Hadean Earth: Modern paradigms and ancient processes,” Paul Mueller and Allen Nutman take us on a lengthy, but beautifully and engagingly written, look at the longest, and most remote era in Earth’s history, the Archean. Increasingly modern theory and analytical capabilities, coupled with new knowledge from meteorites, the moon, and other planets, have led to new understandings of Earth’s earliest history.
The authors have structured their paper in six segments: introduction, in which they review the history of thought and set the broad implications; Archean tectonics and evolution of the lithosphere; evolution of the atmosphere-hydrosphere system; evolution of the oceans and the sedimentary record; origin and evolution of life; and finally, a historical account of investigations in southern West Greenland. In this last segment, Mueller and Nutman review geological, geochemical, and geochronological studies in the Isua region as a “capstone” account of the discovery of the oldest well-preserved volcano-sedimentary terrane on Earth.
M.E. (Pat) Bickford Syracuse University