Just as a stone makes a hole in water when it falls, it makes a hole in grass.
The rain and snow and heat it has collected make the grass close to it a couple weeks ahead and richer in nutrients than the main parts of the sod. This grass pushes up against it and away, as if the stone has landed on it, rather than being there first and calling it forth. It is a wave splashing out. The stone continues to push. Next year, it will push again. Eventually, the grass will cover it, just like the water of a lake closing over a thrown pebble, or even a raindrop. Stones slow time.