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Mantle convection is buoyancy-driven motion in a rocky planetary mantle. Heating and cooling create density differences; chemical and mineral-phase differences can also affect buoyancy. Although the mantle is mostly solid, deformation by material creep permits slow flow over geological time.

A simple model balances viscous resistance with buoyancy and transports heat by both flow and thermal conduction. Its Rayleigh number compares those effects. Temperature-dependent mantle viscosity and the strength of the lithosphere help determine whether the surface moves as plates or remains a stagnant lid. Seismic structure, surface deformation and heat flux constrain different parts of this model.

A mantle plume is a localized buoyant upwelling in a planetary mantle. Hot material can rise because thermal expansion lowers its density relative to its surroundings; compositional differences may strengthen or oppose that buoyancy. As it rises and decompresses, it can cross a rock's solidus and produce melt without requiring heat to be added during ascent.

A volcanic chain, a broad topographic swell or a seismic anomaly can motivate a plume interpretation, but they measure different consequences. Plate motion, background mantle flow, melt transport and crustal structure influence the surface expression. A plume hypothesis is tested by combining those observations rather than reading a unique source depth from a hotspot's position.

The planetary mantle is the predominantly silicate rock region beneath a rocky planet's crust. On geological timescales, solid rock can undergo material creep and support mantle convection without wholesale melting.