Escaping Jail

Riddle: You are in a cell with a roof and walls and it has no windows. The walls are made out of hard dirt that are too hard to break through but soft enough that every time you rub it, dirt slips onto your fingers. You plan on escaping that night. A guard brings you a bucket of water and a hard, squishy loaf of bread that is too hard to eat for lunch. You suddenly think of a plan. What do you do?