Final answer:
Two plates rubbing against each other as they move in opposite directions result in shear stress. This occurs at transform plate boundaries, causing shear deformation, characterized by horizontal shifting of the plates.
Step-by-step explanation:
When two plates rub against each other as they move in opposite directions, the resulting stress is known as shear stress. This type of stress occurs at plate boundaries, specifically at transform boundaries, where the plates slide past each other horizontally. Shear deformation is characterized by the shifting of layers parallel to the force, with the layers moving in opposite directions, and is a common result of shear stress.
Compressive stress and tensile stress are other types of stresses that occur in different scenarios. Compressive stress happens when two opposing forces push towards each other, causing a material to compress, while tensile stress is when forces pull away from each other, stretching a material. However, in the context of plates moving in opposite directions, the correct answer to the student's question is shear stress.