One of the main goals is to understand exactly how pressure and temperature affect minerals and their physical properties. It varies in thickness from 100-200 km thick, and is thinnest in the ocean basins. The thickest lithosphere occurs in mountainous regions such as Tibet. The crust displays a rich spectrum of compositions. The continental regions are composed of mostly granitic and generally silica-rich materials, while oceanic lithosphere has a basaltic composition.
Continents exist as stable rigid plates for billions of years.
The Asthenosphere - Below the lithosphere, materials are hotter and though they are solid they tend to flow over long periods of time. The end result is a hot zone which deforms much easier than materials above it. In terms of plate tectonic theory, this is the zone that allows the lithospheric plates to drift around because of its reduced viscosity. The asthenosphere is the top-most layer of the upper mantle, and has a similar composition. As depth increases clino-pyroxene becomes more dominant.