Convection currents are movements of fluid caused by differences in temperature and density. When a fluid, like water or air, is heated, it becomes less dense and rises. As it rises, cooler, denser fluid moves in to take its place, creating a continuous cycle. This process is essential in various natural phenomena, such as ocean currents and atmospheric circulation. In the Earth's mantle, convection currents play a crucial role in plate tectonics. The heat from the Earth's core causes the mantle to flow slowly, driving the movement of tectonic plates. This movement can lead to geological events like earthquakes and volcanic eruptions, significantly shaping the planet's surface.