The part of the Earth's interior inferred to have convection currents that cause tectonic plates to move is the mantle.

Here's a breakdown:

* Mantle: This is the thick layer of mostly solid rock that lies between the Earth's crust and its core.

* Convection Currents: Within the mantle, there are slow-moving currents of hot, less dense material rising and cooler, denser material sinking. This process is driven by heat from the Earth's core.

* Tectonic Plate Movement: The convection currents in the mantle exert a force on the tectonic plates, which are pieces of the Earth's crust and upper mantle. This force causes the plates to move, resulting in various geological phenomena like earthquakes, volcanic eruptions, and mountain formation.

Let me know if you'd like more details on any of these concepts!