Have you ever thought how cool and weird Grand Canyon is? Yes?, About 100 millions years ago (Jurassic - Cretaceous period) it was The bottom of Pacific ocean; Then around 60 millions years ago (tertiary period) everything changed, and land masses of Grand Canyon rose and became the surface. So the question is what happened? According to the theory, (also, look at the map ) the Pacific Plate shifting towards the Eurasian plates and slowly getting under the Eurasian core. While the other end of the Pacific plate edge (in the USA and Canada) is taking up the Atlantic Plate. This is how Grand Canyon land masses were rose up and later a huge river came about…..
Look at the geological map of world tectonic plates (John Ericksson, 2002, Plate tectonics)