Why are transition zones formed?

Transition zones are specific specific areas in which the continental crust changes to the oceanic one. These zones, when they disintegrate, have 2 types of disintegration: Passive and active continental margins. Transition zones are formed by systems of marginal seas, as well as volcanic island arcs, as well as deep-sea trenches. Transition zones of active outskirts play an important role in life and nature. Mineral resources such as ore are also associated with them, and there are many of them (copper, tungsten, gold, silver, tin and many others).