The term for the shifting of tectonic plates is known as plate tectonics. This geological theory explains the movement of the Earth's lithosphere, which is divided into several plates that float on the semi-fluid asthenosphere beneath. The interactions between these plates can lead to various geological phenomena, such as earthquakes, volcanic activity, and the formation of mountain ranges. Understanding plate tectonics is essential for comprehending the Earth's geological history and the processes shaping its surface over time.