Subduction occurs apex

where the tectonic plates collide

Explanation:

The subduction occurs at the places where the tectonic plates move toward one another and collide. The plate that is denser, less thick, and lower starts to move below the plate that is less dense, thicker, and higher. The plate that moves below the other plate gradually gets into the mantle and is melted, thus destroyed, while the other plate is lifted up near the subduction zone and mountain range forms. When it is an oceanic and continental plate in question, then there's a lot of volcanic activity present, with the volcanic island chains being a common feature above the subduction zone.

Answer: Where crust is destroyed