Geochemistry is 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 Some subsets of geochemistry are: Isotope geochemistry involves the determination of the relative and absolute concentrations of the elements and their isotopes in the earth and on earth's surface. Biogeochemistry is the field of study focusing on the effect of life on the chemistry of the earth. Organic geochemistry involves the study of the role of processes and compounds that are derived from living or once-living organisms.