If you're going to ask a question, at least provide the steps or possible answers that you are provided with so that others can help you. Luckily, I know the exact question you are trying to solve.
The order the steps go in is:
The oceanic plate would subduct under the continental plate into the asthenosphere.
From the intense heat and pressure within the mantle, the crust of the oceanic plate would mix with the rock of the mantle.
Mantle convection would cause magma to rise up through divergent boundaries.