In many respects, shear zones are the deep-level equivalents to faults. They should accommodate relative displacement of the surrounding rocks just as faults do but rather than be surfaces, they consistute bands of rock that have undergone deformation. Some shear zones can be narrow - rather like faults. Others can be tens of kilometres wide - the deep-lithosphere equivalents of fault-dominated plate boundaries seen at the Earth's surface today. This site provides a brief introduction to shear zones, illustrated by outcrop scale examples from the field.