The freeze/thaw cycle causes things to work their way out of the ground, so buried things you want to stay put need to go below the freeze line. https://en.wik

The freeze/thaw cycle causes things to work their way out of the ground, so buried things you want to stay put need to go below the freeze line. https://en.wikipedia.org/wiki/Frost_heaving https://en.wikipedia.org/wiki/Frost_heaving