Now I know this is a mere film, but I still think this would be a fun and interesting topic

As for the eroded mountain thing, it's very, very unlikely and entire mountain eroded away that was once in the middle of a vast plain and left one point structure of a rock that does not look eroded. :B
My personal opinion is that Pride Rock was left by an enormous glacier, and part of the rocks split down the middle, as one rock lodged in the ground the other fell on top. This is subject to change.