Introduction - Mantle Convection for Geologists - page 1

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Introduction
Mantle convection is the fundamental agent driving most geology, yet many geolo-
gists still have only vague ideas about what mantle convection is, how it works and
how it might inform their specialty. Because it is so fundamental, the better every
geologist understands mantle convection, the better scientist he or she is likely
to be. Of course, not everything is affected by mantle convection, but only by
being well informed will a geologist recognise when it is relevant, and what that
relevance is.
Misconceptions about mantle convection also seem still to be quite widespread.
Some aspects of mantle convection are debated. Much of that debate concerns
refinements, so the debate is quite legitimate, but some of the debate is based on
misconceptions or incomplete understanding of current theories or observations.
The latter debate is not productive. This is not to claim that alternative versions are
inconceivable, but just to note that debaters need to be informed about the theories
they wish to challenge if they are to make useful contributions.
For these reasons it seems worthwhile to offer an account of our current under-
standing of mantle convection in terms that are reasonably accessible to most
geologists. That means the account should be fairly short, and there should be little
mathematics beyond basic algebra and arithmetic. Nor should a strong grasp of
physics be assumed, and such physics as is required (notably heat conduction and
viscous fluid flow) should be explained in simple and reasonably familiar terms.
These are the constraints I have set in writing this topic.
Actually I thought I had already done this in Dynamic Earth [1]. The essential
arguments are presented there in fairly simple terms, and mathematical or detailed
sections are clearly flagged and can be skipped. However, that topic is quite long,
it is not cheap, and the appearance of equations is doubtless intimidating. Also,
Dynamic Earth is probably regarded as geophysics , and few geologists might
therefore bother to peruse it. So, it seems Dynamic Earth has not accomplished
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