Mantle convection, plate tectonics and global dynamics. The fluid mechanics of astrophysics and geophysics, vol. 4

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Mantle Convection, Plate Tectonics and Global Dynamics. The Fluid Mechanics of Astrophysics and Geophysics, Vol. 4, by W.R. Peltier (Editor). Gordon and Breach Science Publishers, Montreux, Switzerland, 1989. Hardback, viii + 881 pp., ISBN: 0-677-2212, US$198.00. The series "Fluid Dynamics of Astrophysics and Geophysics" aims at summing up present "established knowledge" with the authors giving their own personal account of the entire field in reviews and articles that the editor welds into unified state-of-the-art account by adding supplementary material of his own. Peltier "opined that the subject of mantle convection had reached a plateau, which could be meaningfully surveyed", as the series editor P.H. Roberts reports. Dick Peltier is known to be an outspoken and argumentative advocate of whole mantle convection, but other models have survived to the present day, and it is fair to say that the book as a whole gives a balanced account of current thinking, although it should be mentioned that some contributions have been written several years ago. The book is divided into 11 chapters or papers that are fairly representative of the whole field. W.R. Peltier, in his introductory chapter 1 " Mantle convection and plate tectonics: the emergence of a paradigm in global geodynamics" elegantly and convincingly demonstrates the existence of mantle convection. F.H. Busse then sets the stage by surveying the "Fundamentals of thermal convection" (2), presenting the theoretical principles which he has developed to a good extent by himself. In the following chapters the emphasis shifts to what we know about the mantle from various fields of earth science. T.H. Jordan, A.L. Lerner-Lam and K.C. Creager in "Seismic imaging of boundary layers and deep mantle convection" (3) take an engaged look at the subject from the angle of seismology, presenting arguments for a "thick" continental tectosphere and "deep" penetration of the subducting slabs into the lower mantle; convection is qualitatively discussed as a boundary layer phenomenon. R. Jeanloz also gives his per-

sonal views of mantle structure and dynamics in "High pressure chemistry of the Earth's mantle and core" (4). He argues for a chemically layered mantle, favoring layered convection, at variance with Peltier's views. The paper was written in 1983, though. S. Hart and A. Zindler, too, discuss geochemical aspects in "Constraints on the nature and development of chemical heterogeneities in the mantle" (5). The data they present are still very puzzling and favour a complex chaotic picture of convection stirring the whole mantle at a large spectrum of scales. W.R. Peltier continues with a strong personal view of"Mantle viscosity" ( 6 ), being more or less uniform vertically in the mantle or with only a small increase from the upper to the lower mantle. The data (glacial isostasy, post-glacial sea level variations, freeair gravity anomalies, earth rotation, polar wander, ice age cycles), the methods or theory, and the results are lucidly presented. The following two chapters again concentrate on convection as such on the basis of largely numerical models. G.T. Jarvis and W.R. Peltier review "Convection models and geophysical observations" (7), scanning a broad field of aspects, as relations with the Rayleigh number, boundary layers, compressibility ... This paper is impartial with respect to the question of whole mantle convection or otherwise. U. Christensen extends the review of (mostly his own) models, stressing "Mantle rheology, constitution, and convection" (8), including temperature, temperature-pressure as well as stress dependancies of viscosity. Many topical geodynamic questions are touched upon, as the time dependence of convection, the role of the 670 km discontinuity, penetration of slabs, mixing, etc. Chapters 9 and 10 again emphasize observations, particularly seismic tomography, plate movements, topography, and the geoid. B.H.

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Hager and R.W. Clayton in "Constraints on the structure of mantle convection using seismic observations, flow models, and the geoid" give an account of the theory relating density inhomogeneities, inferred from tomography, to flow and geopotential anomalies. The main result, well known by now, but here beautifully reviewed, is the required viscosity increase by clearly more than an order of magnitude from the upper to the lower mantle. This contradicts Peltier's earlier results (Chapter 6) but is supported by W.R. Peltier, G.T. Jarvis, A.M. Forte, and L.P. Solheim in "The radial structure of the mantle general circulation", a study similar to that by Hager and Clayton, but additionally treating the effects of phase transitions, where they reach conclusions different from those of Christensen's (Chapter 8). Chapter 10 also convincingly argues for chaotic mantle dynamics. The concluding Chapter 11 "'Formation and early evolution of the earth" by D.J. Stevenson is a concise review of this field. To solve the convection problem the initial conditions should be known at the outset, but it turns out that our picture of early earth evolution con-

sists anyway only of still rather disjunct pieces from the solar nebula and the Hadean stage ( no rock record) to core formation and the stabilization of continents to self regulation of the later thermal evolution. Thus this chapter dealing with the beginning is a good completion of the book. As a whole, "Mantle Convection, Plate Tectonics and Global Dynamics" is impressive. There are a few weak points, as e.g. some poor figures or reproductions. There is some repetition, e.g. of the convection theory in several papers. One may also miss one or the other author. And the price ... But these are minor points in view of the substance and shear volume of the material included. The book makes a very good text for an advanced course m geodynamics and a good introduction into this field as well. It is also fascinating reading for somebody who has taken an active, though small part in the study of mantle dynamics. The book should be found, not only in libraries, but also on private book shelves: it is worth its price. W R JACOBY ( M a i n z )

Volcanic Hazards: Assessment and Monitoring, by John H. Latter (Editor). IAVCEI Proceedings in Volcanology 1, Springer-Verlag, Heidelberg, 625 pages, 1989, DM 178.00. This attractive, compact volume is a collection of 35 papers presented at a symposium on "Volcanic Hazards - Prediction and Assessment" at the International Volcanological Congress held in New Zealand in February 1986. The 625-page hardbound book, the first in a planned series of IAVCEI Proceedings volumes, includes nearly 300 high-quality illustrations (2 in color) and a detailed 27-page subject index that increases the book's utility as a reference volume. More than 80 authors contributed to the collection, which is impressive in both breadth and depth. The first third of the book ( 14 chapters) deals with volcanohazards assessment; the latter part (21 chap-

ters) is devoted to volcano monitoring. Italy, Japan, the Lesser Antilles, and Papua New Guinea are particularly well represented, while South America, Central America (except Mexico), and Hawaii (discussed only in a paper about Iceland) are conspicuously absent. A wide range of topics is covered, with particular emphasis placed on geologic, seismic, and ground-deformation studies at active or potentially active volcanoes. Several new or lesswidely-used techniques also are discussed, including computer-generated movies, satellite imagery, thermal-infrared and gravity surveys, and infrasonic recordings. The hazards-assessment section is arranged