Which statement best defines a convergent boundary?

• A. A boundary where two plates slide past each other.
• B. A boundary where plates move apart.
• C. A boundary where two plates collide, often forming mountains or subduction.
• D. A boundary where plates twist to form rifts.

Answer: (C)

Convergent boundaries are where tectonic plates move toward each other. When two plates collide, their crust is squeezed and thickened, which builds mountain ranges. If one plate is denser oceanic crust, it sinks beneath the other in a process called subduction, creating deep trenches and often volcanic activity on the overriding plate. This combination—plates coming together and interacting in collision or subduction—is what defines a convergent boundary.

The other descriptions correspond to different boundary types: sliding past each other describes transform boundaries, where crust neither significantly creates nor destroys; moving apart describes divergent boundaries, where new crust forms as plates separate; and the idea of twisting to form rifts isn’t the standard way to describe convergent boundaries (rifts form from extension at divergent boundaries).