Which plate boundary involves two plates moving side by side at different speeds or in opposite directions?

• A. Destructive plate boundary
• B. Transform plate boundary
• C. Conservative plate boundary
• D. Constructive plate boundary

Answer: (C)

Moving past each other along a boundary in a horizontal, shear motion is the hallmark of a conservative (transform) boundary. When two plates slide side by side, sometimes at different speeds or in opposite directions, they don’t create or destroy crust; they simply shear past one another. This is why the boundary is described as conserving crust. Earthquakes are common here as rocks stick and then snap past one another, producing slip along faults such as the San Andreas Fault. In contrast, destructive boundaries involve one plate diving beneath another and usually bring subduction and volcanism, while constructive boundaries involve plates moving apart and making new crust. So the described lateral slip best fits a conservative/transform boundary.