Mantle convection is the fundamental agent driving most geology, yet many geologists 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 understanding 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.