Dynamics and Structure of the Earth's Interior

The dynamics and structure of the Earth's inteIior are fundamentally a reflection and product of the thermal regime of the Earth over its entire history. The large scale radial structure, i.e. the segregation of the Earth into a metallic core and a silicate mantle, occurred early in Earth history-, perhaps as an outcome of accretion collision processes which also produced the moon. Subsequent history has been govemed by the mechanisms by which accretionaI, radiogenic and latent heat has been transferred upward for eventual loss by conduction through the Earth's crust. Heat transfer within the core and mantle is largely by thermal convection, significantly modulated by conductive boundary layers at the base and top of and perhaps within the mantle. A special form of convection, plumes spawned in and Iising from the lower mantle boundary layer, are interesting as chemical samples from the deep inteIior but probably account for less than 10% of the present-day surface heat loss. In the early history of the Earth, plumes may have been more ubiquitous and significant thermally.