Originally posted by Jeffery W.
You're right, it is not water erosion that does it. When the rocky material breaks off and falls down (it is crumbling sandstone/shale), that sand stone gets carried by the river and wears down the rocks with the inertia it gets from the moving water. In industry, water cutters don't work from the water cutting steel, they work because there is abrasive material coming out of the tube along with the water, that's what cuts the steel, the water is just there to get it moving fast. If the area where the Grand Canyon was formed was granite, it would have never formed. Granite doesn't break apart like sandstone and shale does. I have yet to see this mentioned in any EU articles or youtube videos. What is really strange is that they never mention plasma cutters, but I would find any use of that to be suspicious, as sandstone main component I believe is silicon dioxide, which is highly electrically insulating, so using the canyon itself as a work piece would not pan out.