It all started as a mountain range, but eroded away after millions of years.
After millions of years of the mountain range eroding it created a flat plain.
8 oceans came and went dropping off different layers of sediment. Creating multiple different layers.
Tectonic movement forced the flat plain into a plateau.
An ancient lake spilt over the plateau filling it with water.
Energy from falling water pulled along rocks and sand, eventually created as we know as the grand canyon. The water carrying the rocks and sand slowly created the G.C. 1 foot every 1,000 years.