Overview

Plate tectonics on Earth, at present, consists of about a dozen large semi-coherent entities – called plates – of irregular shape and size that move over the surface, separated by boundaries that meet at triple junctions. There are also many broad zones of deformation.

Plate tectonics is often regarded as simply the surface, or the most important, manifestation of thermal convection in the mantle [this phrase, and phrases in the same typeface, is a Googlet; see Preface or type it into a search engine]. In this view the plates are driven by thermal and density variations in the mantle. Cooling plates and sinking slabs can also be regarded as driving themselves, and driving convection in the underlying mantle; they create chemical, thermal and density anomalies in the mantle.

Plate tectonics qualifies as a branch of complexity theory. Plate tectonics may be a far-from-equilibrium self-organized system powered by heat and gravity from the mantle and organized by dissipation in and between the plates. Mantle convection, below the plates, may not drive or organize the plates; it may be the other way around.