Final answer:
The asthenosphere is the layer of the Earth that allows the movement of tectonic plates due to its ability to flow, driven by the process of mantle convection.
Step-by-step explanation:
The layer of the Earth that can move internally or flow to allow the plates to move around on it is known as the asthenosphere. This layer lies beneath the lithosphere, which includes the Earth's crust and the uppermost part of the mantle.
The asthenosphere is mechanically weak in comparison and behaves in a ductile manner, allowing it to flow slowly. This flow is caused by the process known as mantle convection, where heat from the Earth's interior is transferred towards the surface.
Mantle convection contributes to the movement of the tectonic plates, leading to their divergence, convergence, or transform movements that shape the Earth's surface.