The Interior of the Earth

Abstract

The interior of the Earth (and, a fortiori, of the other planets) is much less known than the interior of the Sun, and also of stars light years away. The physics and chemistry of solid and liquid phases at high pressures, essential for the understanding of terrestrial planets and the core of the outer planets, are much more complex than those of nearly perfect gases (which form stars) and very little known. For the Earth, the detailed study of seismic propagation has provided, especially for the mantle, excellent measurements of its density distribution and is discussed in this chapter. The model of its interior so obtained is quite relevant for the study of its geological history, as well as for other planets. Planetary interiors are characterized by two major features: a fluid, conductive core, which generally produces a global magnetic held by the dynamo process (Ch. 6); and the interaction between the crust and the slow motion of convective eddies in the mantle. Due to this interaction, the crust undergoes continuous deformations, responsible for continental drifts, earthquakes and the uplifting of mountain chains. They are called plate tectonics and are discussed in some detail here, also in view of the fact that they can be measured directly from space.