Evolution of the earth's mantle and core: convective cycle within the mantle and different plate tectonic environments related to magma generation

Abstract

The earth is considered to have been formed in several stages in a solar nebula by accretion of carbonaceous chondrites. The moon might have been formed toward the end of such a process by collapse of a sedimentary ring around the proto-earth or due to collision of the proto-earth with a large comet. The thermal energy related to the impact resulted in the formation of a magma ocean. The process of density stratification of Fe-Ni alloy at the core and other silicates (magnesiowustite, pervoskite, garnet, spinel, etc.) is the subject of modern experimental studies. The large difference in temperature between the core and the mantle-crust interface resulted in convection, either involving whole mantle right from the outer core or initiating two-layered convection (650 km seismic discontinuity separating the two convective cycle systems). Earthquake and volcanism in the mid oceanic ridges, oceanic plate boundaries and subduction zones are surface manifestations of energy flow through mantle convection.