The Rock Cycle is a group of changes. Igneous rock can change into sedimentary rock or into metamorphic rock. Sedimentary rock can change into metamorphic rock or into igneous rock.
The Water Cycle Water on Earth is always changing. Its repeating changes make a cycle. As water goes through its cycle, it can be a solid (ice), a liquid (water), or a gas (water vapor).
Sometimes an oceanic crust and continental crust collide. This is one type of convergent boundary. Oceanic crust makes up oceans and the continental crust makes up land. When these two crusts collide, the oceanic crust is forced to move downwards because of its high density. Whereas, the continental crust pushes upward because it is lower in density.