"Develop a model based on evidence of Earths interior to describe the cycling of matter by thermal convection.
[Clarification Statement: Emphasis is on both a one-dimensional model of Earth, with radial layers determined by density, and a three-dimensional model, which is controlled by mantle convection and the resulting plate tectonics. Examples of evidence include maps of Earths three-dimensional structure obtained from seismic waves, records of the rate of change of Earths magnetic field (as constraints on convection in the outer core), and identification of the composition of Earths layers from high-pressure laboratory experiments.]"