Here's how it works:

1. Heat from the Earth's core: The Earth's core is extremely hot, generating immense heat. This heat is transferred to the mantle, the layer of rock beneath the Earth's crust.

2. Convection currents: The heat from the core causes the mantle to become less dense and rise. Cooler, denser mantle material sinks to take its place. This creates circular currents called convection currents.

3. Plate movement: The convection currents in the mantle drag the tectonic plates along with them. These plates are like giant rafts floating on top of the mantle, and they constantly move and interact with each other.

4. Geological activity: The movement of these plates causes various geological phenomena, including:

* Volcanism: When plates pull apart (divergent boundaries), magma rises to the surface, forming volcanoes.

* Earthquakes: When plates collide (convergent boundaries), they can cause earthquakes.

* Mountain formation: Collisions between plates can create mountain ranges.

* Seafloor spreading: Divergent boundaries at mid-ocean ridges create new seafloor.

In summary, the convection currents in the Earth's mantle are the driving force behind plate tectonics, leading to the movement of the Earth's crust and all the geological phenomena associated with it.