|convergent plate boundary|
A tectonic boundary where two plates are moving toward each other. If the two plates are of equal density, they usually push up against each other, forming a mountain chain. If they are of unequal density, one plate usually sinks beneath the other in a subduction zone. The western coast of South America and the Himalayan Mountains are convergent plate boundaries. Also called active margin, collision zone. See more at tectonic boundary. Compare divergent plate boundary.