What is primarily responsible for the movement of continents over long periods of time?

The movement of continents over long periods of time is primarily attributed to the shifting of tectonic plates. The Earth's lithosphere is divided into several large and small tectonic plates that float on the semi-fluid asthenosphere beneath them. These plates constantly move, albeit very slowly, due to the convection currents caused by the heat from the Earth's interior. As a result of this movement, continents can drift apart, collide, or slide past one another, leading to various geological phenomena such as earthquakes, volcanic activity, and the formation of mountain ranges. This plate tectonics theory provides a comprehensive explanation for the historical and ongoing changes in Earth's surface, reflecting the dynamic nature of our planet.