Afault is a in the earth's crust, and a fold is a of the earth's crust. crack, bending crack, tilting tilt, bending bending, tilt

Crack and Bending are the two answers. Faults are where the earth's plates have actually cracked and separated, whereas a fold is simply where the plates have bent. Faults are where earthquakes most often take place, whereas folds can lead to formations such as mountains.