Answer:
Oceanic Lithosphere
Explanatation
Oceanic lithosphere is more dense (compacted by immense pressure from oceans) and the continental lithosphere is less dense (lack of pressure from anything above it). When the two collide, the continental lithosphere will essentially float on top of subterranean magma while the oceanic lithosphere, being the denser of the two, will slip beneath the continental lithosphere and dive into the magma chamber.
