Don't all those rocks wreak havoc with the plough, Carl?
I don't imagine people up there in upstate New York and the hippies in Vermont, manage to hand down ploughs from generation to generation.
Those twin tubes that are sticking up over each bottom contain very heavy springs.
There is a bunch of linkage that allows the beam to raise up and over large buried rocks and ledge.
It is called "tripping",the springs are extended when that happens and then they contract after the obstacle is passed.
This resets the plow beam to its working position without stopping forward travel.