Geochemistry: the science that uses the tools and principles of chemistry to explain the mechanisms behind major geological systems such as the Earth's crust and its oceans. The realm of geochemistry extends beyond the Earth, encompassing the entire Solar System and has made important contributions to the understanding of a number of processes including mantle convection, the formation of planets and the origins of granite and basalt. Geochemists study the composition, structure, processes, and other physical aspects of the Earth. They examine the distribution of chemical elements in rocks and minerals, as well as the movement of these elements into soil and water systems.