Pre - Plate - Tectonic

Geological models of subduction zones impact thinking about many of the central problems in the structure, dynamics, chemistry, and history of the solid earth. Should those models change, the effects will reach across the earth sciences. We are currently in the midst of such a change, brought on by several causes. First, the earth science community recently began an organized, multi-disciplinary study of subduction zones by way of the National Science Foundation's "Margins initiative." This has improved the quality of our descriptions of key focus areas and should continue to do so for the next several years. Less purposefully but of equal importance, several of the debates in subduction zone research have evolved in recent years, making us revisit both recent and old observations in a new light. This book consists of descriptions of these advances, written by the some of the leading participants. I describe the origin and organization of the book in the preface; here I review the context of previous thought regarding convergent margins, with particular focus on the link between tectonics and magmatism, and point out questions raised in the following chapters.