The Earth is a dynamic system subject to both cyclic and direc­ tional changes over time. Energy from the Sun drives Earth's wa ter and biogeochemical cycles, which in turn, control surface processes, including climate change and sedimentation. Energy from Earth's interior drives the tectonic cycle and its surface mani­festations, including volcanic eruptions and earthquakes. Biologi­ cal evolution adds directionality to the history of the Earth, and is not reducible to simple physical forces. The geological sciences study these changes and processes as they exist now, as they will develop in the future, and as they have evolved during the 4.5 bil­lion-year history of the Earth.

The biological, chemical, and physical aspects of the Earth are all integrated into the geological sciences, which draw heavily on these other sciences, as well as mathematics and statistics. Geological sciences provide knowledge about the availability of natural resources, including groundwater and fossil fuels; assessing and reducing damage from hazards including volcanic eruptions, earthquakes, and floods; and processes affecting biological evolution, such as those that produce major extinctions. From these diverse studies geologists gain knowledge about the controls on the physical and biological environment. That knowledge allows people to deal with issues ranging from groundwater pollution to climate change.