Why do rocks float in sand?

[timothy_gammey]

was building a route, lots of big rocks on it. used the dozer to shove them into a hole that needed filling anyway. Win/win, or so I thought. I poured sand in and.... the rocks floated up to the surface of the sand.

I have seen rocks do a lot of funny things IRL, but float to the surface after being buried in sand ain't one of em.

[IndianaJones]

Yup, that's annoying one.

To be fair had only one or two cases like that.

[Disgruntled Democracy Officer]

leveling sand also uproots tree trunks because why not