Geodynamics is a branch of physics that studies how the forces and processes that occur deep inside the planet change and shape the earth over time.
Throughout geologic history, the earth has constantly changed, and it continues to do so. Geodynamics seeks to explain how and why. It studies the interactions between the planet's layers, including the liquid-metal core, the hot mantle surrounding it, and the crust, or outermost layer. Geodynamics helps explain how tectonic plates collide to form mountains and pull apart to create oceans. It deals with the forces that cause volcanic activity, earthquakes, and the magnetic field that provides a protective shield around the planet.