Final answer:
At convergent boundaries, one plate may subduct under another plate if the subducting plate has an oceanic crust. The oceanic crust is denser and thinner compared to the continental crust. As the subducting plate moves into regions of high pressure and temperature, it eventually melts and its material is recycled into a downward-flowing convection current.
Step-by-step explanation:
At convergent boundaries, the subduction or non-subduction of plates depends on the type of crust involved. When two plates collide and one of the plates has an oceanic crust, subduction occurs. This is because oceanic crust is denser and thinner compared to continental crust. The subducting plate, which has water-rich minerals, is forced beneath the other plate into regions of high pressure and temperature. Eventually, it melts and its material is recycled into a convection current.