An interesting thing about the Great Unconformity in the grand Canyon: the rocks where the Colorado River now flows are masses of rock that were molten or became metamorphosed (were changed, or transmuted, in their form through great pressure and heat) and formed mountains that were then worn down into level plains; then great thicknesses of rock were lain down upon those plains over many millions of years, until they were faulted (broken) and thrust up into mountains which were, again, eroded flat into plains, on which oceans and deserts ebbed and flowed until the entire region was uplifted becoming the Colorado Plateau, with the Colorado River cutting down through the layers of rock like a knife cutting into a layer cake as the cake is lifted around the knife. Ét voilá…