fault

A fracture in the earth's crust along which rock masses have moved relative to each other — shifted, displaced, ground past. Faults range from inches long to thousands of miles. The San Andreas is a transform fault — two plates sliding laterally past each other. Normal faults pull apart; reverse faults compress. A thrust fault pushes older rock on top of younger, reversing the expected order of the geological record. The word carries its moral connotation into the landscape — the earth is at fault, broken along a line, the two sides no longer aligned.