A relatively small-scale (up to 250 km across) rise, sub-circular in plan view. The date a seamount is formed, and the tectonic setting they erupt into (on-ridge or off-ridge), reflect the way the lithosphere interacts with the fluid mantle beneath. For the radiometric dating of seamounts, see Hillier (2007) Geophys. J. Int. 168. McClain (2007) J. Biogeog. 34, 11 challenges the view that seamounts are oases/biodiversity hot spots.