1.   Some of the sea-floor sediments, muds, and oozes sitting on top of the oceanic plate also get melted.

2.   It hit where the Nazca oceanic plate slowly grinds its way beneath the western edge of South America.

3.   Studies suggest that sediments eroding from the edges of continents onto oceanic plates get carried into the mantle in small doses.

4.   Where it ends up depends on the movement of the oceanic plates, which are shifted laterally by the subterranean churning of the mantle.