If the Grand Canyon was formed over millions of years of river erosion. Then the top half of the canyon has been exposed to millions of years of rain erosion, correct? So rain erosion is vertical erosion because rain fall down, not sideways, correct?

So millions of years of this vertical rain erosion should have made the horizontal erosion from the river disappear, right?



So please explain how the the horizontal lines still exist all the way to the top, as well as the bottom? And are just as deep cut into the rock in the top as the bottom as if vertical erosion has been going on for a few thousand years instead of millions?

And just in case the answer is wind erosion:

Wind erosion is not the same as water erosion. It does not even look the same. So the horizontal lines are still there because it did not take millions of years to make them.

Unless someone would like to explain how the Grand Canyon is exempt from vertical rain erosion by rewriting erosion laws? Anyone?