Answer:
Because both the zones have different compositions.
Step-by-step explanation:
The continental crust is composed of mainly graphite whereas the oceanic crust is made up of basalt. The oceanic plates are thinner than the continental plates. Also the oceanic plates are much denser as compared to the continental plates. Now the continental plates at the convergent boundary gained thickness as they are pushed upward. These plates or zones are of different composition an densities and so when they collide different features can be seen at the two conversion zones.