In what formation are mariana trench plates involved?

Subductio zone

Explanation:

The Mariana trench is a result of the convergent plate boundary between the Filipino plate and Pacific plate, creating a subduction zone. The Filipino plate is not a large one, but still the much larger Pacific plate is subducting below it. The reason for this is that the Pacific plate is denser, heavier, lower. At the boundary itself, the Pacific plate moves below the Filipino plate, slowly getting into the mantle layer and getting melted and destroyed. The subduction zone though makes a large gap between the two plates, a gap that is constantly under immense pressure and experiences constant geological activity. This gap is filled with the ocean water, and it is actually the deepest place on the surface of the Earth with over 11 km bellow sea level. The name of it comes from the island chain next to the subduction zone, the Mariana Islands, thus it is called Mariana trench.

answer at the divergent plate boundary in the middle of the ocean;