Final answer:
The stress force that pulls on the crust where two plates are moving apart is called tension. Tension occurs at divergent plate boundaries, such as the Mid-Atlantic Ridge or the East African Rift Zone.
Step-by-step explanation:
The stress force that pulls on the crust where two plates are moving apart is called tension. Tension occurs at divergent plate boundaries, such as the Mid-Atlantic Ridge or the East African Rift Zone. When two tectonic plates separate, the lithosphere is stretched and thinned, resulting in tensional forces.
Learn more about Plate Tectonics