The critical zone is defined as the "heterogeneous, near surface environment in which complex interactions involving rock, soil, water, air, and living organisms regulate the natural habitat and determine the availability of life-sustaining resources". Extending from the top of the vegetation canopy through the groundwater table, the critical zone supports nearly all terrestrial life on Earth. The critical zone provides us with clean air, drinkable water, fertile soil and much more. However, human activity has changed the structure and function of the critical zone by altering its constituent parts: the atmosphere, lithosphere, hydrosphere and biosphere. Now more than ever, understanding the critical zone is crucial to human flourishing and sustainability. This course integrates core concepts of geology, hydrology, ecology and soil science to provide a foundational understanding of the critical zone and its role in addressing environmental problems. Class Notes: **Course Requisites: CHEM 151 (Recommended), OR Instructor consent. Enrollment Requirements: ENVS 210.