a)Folding occurs when tectonic processes put stress on a rock, and the rock bends, instead of breaking. This can create a variety of landforms as the surfaces of the folded rocks are eroded.
b)A fault is formed in the Earth's crust as a brittle response to stress. Generally, the movement of the tectonic plates provides the stress, and rocks at the surface break in response to this. Faults have no particular length scale.
