All biological organisms require certain nutrients to live. Plants require carbon, hydrogen, and oxygen from air and water, as well as nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, iron, manganese, copper, zinc, nickel, chloride, boron, and molybdenum from soil. Animals require a few others. Conversions and transformations of nutrients in the environment result from chemical reactions, biological activity, or both.
Over Earth’s 4.5 billion-year history, tectonic upheavals and colliding plates formed mountain ranges and carved out basins. Forces of erosion and weathering have been at work to break down these landforms. Records of these processes are imprinted on the land and define distinctive landscapes around the United States and in its national parks.
Earth processes such as volcanic eruptions, floods, landslides, and glaciers leave behind evidence of their passing in the form of layers known as deposits. By studying deposits of recent geologic events, geologists are able to better understand older deposits and identify the processes that caused them.