Page 10 - Global Tectonics

The mechanism of plate tectonics ix
Preface

A s is well known, the study of tectonics, the branch Thus one moves from consideration of the fundamentals
of plate tectonics, which are best illustrated with refer-
of geology dealing with large-scale Earth structures
and their deformation, experienced a major break- ence to the ocean basins, to continental tectonics, culmi-
through in the 1960s with the formulation of plate nating in Precambrian tectonics, and a discussion of the

tectonics. The simultaneous confirmation of sea fl oor possible nature of the implied convection in the mantle.
spreading and continental drift, together with the recog- The book is aimed at senior undergraduate students
nition of transform faults and subduction zones, derived in the geological sciences and postgraduate students and
from the interpretation of new and improved data from other geoscientists who wish to gain an insight into the

the fields of marine geology and geophysics, and subject. We assume a basic knowledge of geology, and
earthquake seismology. By 1970 the essentials of plate that for a full description of geophysical and geochemi-
tectonics – the extent of plates, the nature of the plate cal methodology it will be necessary to refer to other
boundaries, and the geometry and kinematics of their texts. We have attempted to provide insights into the

relative and finite motions – were well documented. trends of modern research and the problems still out-
As further details emerged, it soon became apparent standing, and have supplied a comprehensive list of ref-
that plates and plate boundaries are well-defi ned in erences so that the reader can follow up any item of
oceanic areas, where the plates are young, relatively thin, particular interest. We have included a list of questions
but rigid, and structurally rather uniform, but that this is for the use of tutors in assessing the achievement of
not true for continental areas. Where plates have conti- their students in courses based on the book. These are
nental crust embedded in them they are generally thicker, mainly designed to probe the students’ integrative
older and structurally more complex than oceanic plates. powers, but we hope that in their answers students will
Moreover the continental crust itself is relatively weak make use of the references given in the text and material
and deforms more readily by fracture and even by fl ow. on relevant websites listed on the book’s website at:
Thus the nature of continental tectonics is more complex http://www.blackwellpublishing.com/kearey
than a simple application of plate tectonic theory would The initial impact of the plate tectonic concept, in the
predict and it has taken much longer to document and fields of marine geology and geophysics and seismology,

interpret. An important element in this has been the was quickly followed by the realization of its relevance
advent of Global Positioning data that have revealed to igneous and metamorphic petrology, paleontology,

details of the deformation field in complex areas. sedimentary and economic geology, and all branches of
The other major aspect of plate tectonics in which goescience. More recently its potential relevance to the
progress initially was slow is the driving mechanism Earth system as a whole has been recognized. In the past,

for plate motions. Significant progress here had to await processes associated with plate tectonics may have pro-
the development of new seismologic techniques and duced changes in seawater and atmospheric chemistry,
advances in laboratory and computer modeling of con- in sea level and ocean currents, and in the Earth’s climate.
vection in the Earth’s mantle. These ideas are briefly reviewed in an extended fi nal

Since 1990, when the first edition of Global Tectonics chapter on the implications of plate tectonics. This

appeared, there have been many developments in our extension of the relevance of plate tectonics to the
understanding of Earth structure and its formation, par- atmosphere and oceans, to the evolution of life, and pos-
ticularly in relation to continental tectonics and mantle sibly even the origin of life on Earth is particularly grat-
convection. As a consequence, approximately two-thirds ifying in that it emphasizes the way in which the
of the figures and two-thirds of the text in this third biosphere, atmosphere, hydrosphere, and solid Earth are

edition are new. The structure of the book is largely interrelated in a single, dynamic Earth system.
unchanged. The order in which data and ideas are pre-
K.A. KLEPEIS
sented is in part historical, which may be of some interest F.J. VINE
in itself, but it has the advantage of moving from simple
to more complex concepts, from the recent to the distant A companion resources website for this book is avail-
past, and from the oceanic to the continental realms. able at http://www.blackwellpublishing.com/kearey

ix