Gravel

Gravel is a natural block. It is a block that responds to gravity.

Generation
Gravel can sometimes be found in regions near sea level, often lining the edges of bodies of water or appearing in submerged areas. It replaces the top layer of terrain without affecting the blocks underneath. Since Gravel does not update on its own, this can rarely lead to small areas of floating gravel blocks.

Behaviour
Gravel blocks will fall down when they are not supported by a block which is collidable. When it is placed or updated by a neighbouring block, it will check whether the block underneath itself is a collidable block. If the block is not collidable, the Gravel will move down as many blocks as possible until it reaches a collidable block in a single server tick.