Plate tectonics is the unifying theory of the solid Earth that describes the surface of our planet as being fragmented into rigid plates that move in relation to each other. Many fundamental geological processes, such as earthquakes, volcanism, and the formation of mountains, occur at the plates’ boundaries. In its initial formulation, plate tectonics was a kinematic theory that described and quantified these movements and associated deformation. Plate tectonics evolved into a dynamic theory, describing the forces driving the surface deformation and the internal dynamics of our planet. We also came to realize that plate tectonics is only one of the possible tectono-magmatic styles in which a planet can operate and that these can change over time. In the past years, the geosciences community has started to develop a theory that integrates plate tectonics and mantle convection as part of a single system. This was possible because of the ever-increasing high-quality imaging of Earth’s interior and our computational capabilities. But while the progress has been enormous, there are still many uncertainties and challenges ahead. <...>

This book is a collection of papers on an aspect of plate tectonics of which our understanding is at present limited. In the mid-1970s, prior to the recent phase of IPOD active margin drilling, few geologists would have anticipated that at the start of the 1980s so many new questions concerning the nature of tectonic and sedimentary processes in forearc regions would have come to light.

Plate tectonics, as it operates in the modern earth, represents in a fundamental sense a mechanism by which excess thermal energy from the mantle is dissipated (Sclater et ai., 1980). A substantial data base now exists concerning the operation of plate tectonics during Phanerozoic time, and evidence for similar tectonic activity during Proterozoic time appears to be steadily growing, both in quantity and quality.

Fifty years ago, Tuzo Wilson published his paper asking ‘Did the Atlantic close and then re-open?’. This led to the ‘Wilson Cycle’ concept in which the repeated opening and closing of ocean basins along old orogenic belts is a key process in the assembly and breakup of supercontinents.

Throughout the history of the study of the Earth, geologists have attempted to understand the factors and forces which shape the surface of our globe. In this book, we shall attempt to summarise the current theories of how the gross surface layer of the Earth evolves tectonically.

Forty years ago when plate tectonics was first discovered, there was a major shift in thinking in the Earth Sciences. Little was known at that time about the deep mantle because of the lack of knowledge about material properties, the absence of any seismic tomography or concepts such as mantle convection. Thus the theory of plate tectonics was built on surface observations and kinematic constraints. The theory of plate tectonics is not independent but consists of several assumptions. Examples are the origin of arc magma, MORB or OIB, and the distribution of earthquakes and the plate margin processes are all part of plate tectonics theory. <...>

All aspects of the Earth’s history and structure, including its majestic mountains, giant rift valleys, and deep ocean basins, were fashioned by mobile crustal plates.The Earth’s outer shell is made up of a dozen or o plates composed of the upper mantle, or lithosphere, and the overlying continental and oceanic crust.The plates ride on the semimolten rocks of the upper mantle and carry the continents along with them.The movement of the plates accounts for all geologic activity taking place on the planet’s surface. In this manner, plate tectonics is continously changing and rearranging the face of the Earth.

This book has grown and evolved from a course I teach at New Mexico Tech, which is taken chiefly by seniors and graduate students in the Earth Sciences. The rapid accumulation of data on plate tectonics, mantle evolution, and the origin of continents in the last decade has necessitated continued updating of the course. The book is written for an advanced undergraduate or graduate student, and it assumes a basic knowledge of geology, biology, chemistry, and physics that most students in the Earth Sciences acquire during their undergraduate education. It also may serve as a reference book for various specialists in the geological sciences who want to keep abreast of scientific advances in this field. I have attempted to synthesize and digest data from the fields of oceanography, geophysics, geology, planetology, and geochemistry, and to present this information in a systematic manner, addressing problems related to the evolution of the Earth's crust and mantle over the last 4 Gy. The role of plate tectonics in the geological past is examined in the light of geologic evidence, and examples of plate reconstructions are discussed. <...>

Planet Earth is unique in many ways from the other silicate-metal planets in the solar system. In addition to oceans and an atmosphere that contains oxygen, Earth is the only planet that exhibits plate tectonics. Plate tectonics appears to be the result of convective cooling of the mantle, although the gravitational pull of subducted slabs probably drives plate motions (Conrad and Lithgrow-Bertelloni, 2002). Plate tectonics includes sites of plate formation at ocean ridges and sites of recycling into the mantle, which today are at subduction zones. Although geodynamic models support coherent plates throughout Earth history, just when and how plates became negatively buoyant is not yet clear. This is partly due to our uncertainty about the early thermal history of the mantle. Was the mantle hotter than at present, as generally assumed, or was it the same temperature (or even lower) due to enhanced rates of convective cooling during the early Archean? This leads to the question of how we track modern-style plate tectonics back in time. <...>