Terrain Grand Canyon MPVC!
I like everything, except it could be a little more refined (I see pixels). Since I have never been at this level inside the Grand Canyon, I can't say it's realistic. But, it looks very much like it is realistic.
I like the colors and composition of the scene very much. I would think about increasing your AA a little to get rid of some of the sharp pixel edges, and it might also be a good idea to add some objects into the scene to help set the scale.