When two plates converge one plate can be forced beneath the other plate. This is called a Subduction Zone . There are two reasons why plates subduct. One plate is denser than the other. Oceanic plates which are made of basalt will usually subduct when colliding with continental plates which are made of granite and not as dense.
Convection currents help drag the plate down into the mantle.
Subduction happens when oceanic plate meets continental plate, or when oceanic plate meets oceanic plate. Depending on the situation there are two types of distinct features produced on the earth When ocean meets continent When oceanic plate meets continental plate the oceanic plate subducts under the continental plate. The oceanic plate melts as it moves deeper into hotter areas of the mantle. This melted material is less dense than the surrounding mantle material and rises through the crust producing a chain of volcanic mountains. The Andes Mountains of South America are being formed this way as the Nazca Plate subducts under the South American Plate.