Geochemistry applies chemical principles and tools to study the chemical composition of the geosphere, hydrosphere, biosphere, and atmosphere on Earth, and the exchange of matter and energy between these compartments over a wide range of timescales, from human to cosmic.<br><br>Geochemists at CU Boulder study the distribution and cycling of elements (and their stable isotopes) in water bodies, sediments, soils, minerals, and rocks, the interactions between microbes and the environment, the chemical and stable isotope fingerprints of biological processes, the co-evolution of the solid Earth, its oceans, atmosphere, biosphere, and climate, the formation of fossil fuels and ore deposits, and the conditions, timing, and rates of physical and biological processes on the Earth and other planets. Sub-disciplines of geochemistry covered by multiple research groups include biogeochemistry, organic and stable isotope geochemistry, trace and elemental geochemistry, metamorphic and igneous-rock geochemistry, and geochronology/thermochronology.