This course explores interactions between the physical Earth, its major systems (the lithosphere, hydrosphere, atmosphere, cryosphere, pedosphere and biosphere) and our human activities. Geochemical cycles are the transport and transformation of the elements between these major Earth systems as understood through application of chemical principles to earth and environmental science. Emphasis is placed on understanding controls on the abundance of key chemical constituents in the atmosphere, rivers, lakes, oceans, biosphere and major rock reservoirs.