Plates vs plumes—a geological controversy by Gillian R. Foulger. Wiley-Blackwell, Chichester, 2010. No. of pages: 328. Price: UK£39-95. ISBN 978-1-4051-6148-0 (paperback).


This book presents a discussion into the origin of volcanic melting anomalies, in simple terms large basalt outpourings at the Earth's surface. It asks whether they should be ascribed to either deep mantle processes (the ‘plume’ hypothesis) or relatively-shallow lithosphere processes (the ‘plate’ hypothesis)? The book is well written and well illustrated, with copious grey-scale figures throughout, plus a selection of key figures reproduced as colour plates. It is, however, a book for which I find it hard to identify the likely purchasing audience, although each chapter in the book concludes with a short section called ‘Exercises for the student’. Thus, the book is written in academic textbook style, but overall I can't help feeling that it doesn't meet the requirements of a typical student textbook.

The mantle plume controversy has been a topic of vigorous international debate over the last decade and this book's author has been at the forefront of those challenging the validity of the established plume hypothesis, first proposed in the 1970s. Is it, however, a topic worthy of a whole textbook aimed primarily at a student audience? For a number of reasons I think perhaps not, at least in the form presented in this book. I will try to explain why. At the most basic level I would ask the question whether any academic institution devotes sufficient time to teaching and discussing the origin of melting anomalies that a 300+ page textbook on the subject is warranted. I doubt it very much. From this point of view the length of the book is overkill and probably contains too much information for the average student to assimilate usefully.

As this book is a self-defined student textbook, I think there is also a fundamental problem with the balance of the content. A textbook for teaching or learning purposes should have a balanced content, presenting facts or hypotheses, but without too many polarizing arguments (the latter should rightly take place in peer-reviewed literature). As mentioned above, however, the book's author is a leading advocate of the plate hypothesis and, therefore, most of the book is spent challenging and arguing against the plume hypothesis. I don't have an issue with the author holding their own opinion, but I think that if a book on this subject is warranted then it would have been better written by someone who ‘sits in the middle’ of the argument, rather than very strongly on one side. If, for balance, you wish to read an advocation of the plume hypothesis then you will have to search outside this book. Eventually the imbalance of the book, albeit acknowledged by the author, began to grate on me as I progressed through each chapter. There was never an unexpected punchline or conclusion; at the start of each chapter you know what the outcome is going to be by the end.

I read in another review that the book could serve as a standard Earth dynamics (my words) student text, in addition to covering the plume debate. I don't really think this is the case because the balance of the content is not correct for this. I did find, however, that I most engaged with the book and was keen to read on in the sub-sections where it does provide an introductory, unpolarized review of a subject, acting for me either as revision or new teaching. I think this reinforces the point that better balance in the content would make a better book for the general reader.

Another smaller-scale gripe I have about the balance is in the book's title. I think this skews the debate right from the front cover. One may well choose to debate the existence of mantle plumes, but very few, including those who advocate the plume hypothesis would similarly debate the existence of tectonic plates. So the book isn't really about plates vs plumes, because nearly all readers will accept that plates exist, whatever their view on plumes.

In its discussion of melting anomalies the book covers an admirably wide range of subject matter, through geodynamics, seismology, geochemistry and thermal studies. On the whole I have the impression that the bulk of the scientific content is sound, but when scrutinizing my own particular area of specialist interest, the geodynamics of rift basins and continental margins, I did feel that the treatment was in some cases less accurate than it might have been and the references cited were rather selective (towards the plate argument). So, I did wonder if the same might apply in the areas about which I know less in detail.

Given that I have said much about the deliberate leanings of the book in favour of the plate hypothesis, we should ask whether it achieves its objective of establishing this theory as the new paradigm for melting anomalies. It certainly demonstrates that the original and relatively-simple plume hypothesis of the 1970s has been seriously over-used and over-elaborated in its 30+ years of existence and we should retreat from a stance of plumes with everything as far as melting anomalies are concerned. But does it irrevocably kill off the plume hypothesis for the ‘big boys’ of the plume world such as Iceland, Hawaii and Deccan? I'm not sure it does and the main reason for this is that despite 300+ pages of text I did not really come away from the book understanding what, within the context of the plate tectonic model, is supposed to be responsible for generating these large melting anomalies. The book spends a lot of time arguing against the plume hypothesis, but is rather unclear about the alternative explanations in situations where a standard plate tectonic decompression-melting model should not generate the observed melting anomalies.

Overall, this review will seem rather critical, but that is not to say this is a bad book and if you are interested in or involved in the plume debate then it may be worth having a copy as a useful compendium on the debate. My ultimate question, though, would be whether this debate is best addressed by a single-author textbook, because I can't help thinking that a polarized discussion of this nature is best placed within the world of peer-reviewed literature, where discussion can take place, rather than in the less challenging and less challenged world of the academic textbook.