Sagot :
It depends upon what kind of plate will collide. If continental to oceanic, the oceanic plate will subduct and melt to form a magma. On the other hand, the continental plate will form volcanoes, mountains etc. Trenches will also be formed. When water mixes with the magma, it makes the magma less denser thus producing volcanic activities. There's a difference when both continental plates collide and oceanic to oceanic.