Undulation is a term used to describe a variety of movements, such as those created by CONVOLUTION, EARTHQUAKE, SPIRAL, RIPPLE, and wave. CONVOLUTION is an intricate pattern or movement that is often seen in nature, such as the shape of a river or the formation of clouds. An EARTHQUAKE is a sudden shaking of the ground caused by the release of energy from the Earth's crust. A SPIRAL is a curved line that winds around a central point. A RIPPLE is a small wave on the surface of a body of water. Lastly, a wave is a disturbance that travels through a medium, such as air or water. All of these terms are related to undulation, which is the overall term used to describe these types of movements.