I read a question about sand. In one answer, an hourglass was mentioned.
Suppose you have enough fine, dry sand. If you create a pile of sand by letting a beam of sand fall down on the land (like in an hourglass), how high can the pile get?
Will the pile collapse under its own weight at a certain height, or can you make it as high as you want? Say the pile is placed on an infinite plane with a uniform gravity. Will it get flatter and flatter if you pour in more sand (like water flattens if you pour it onto the plane)?