The Tidal Forces of Gravity

The gravity of the earth mass black hole if you're one centimeter away from it would be quadrillions of times more powerful than earth's gravity. The tidal forces come from the variation of gravity across distance and basically the black hole is tugging you apart because it's pulling on different parts of you with different strengths. As you get closer to the black hole the difference in those two forces grows and so the effective force the earth trying to decapitate you also grows, eventually it overcomes your body's ability to keep your head on your shoulders.