A block of the Earth's crust, generally with a length much greater than its width, that has been dropped relative to the blocks on either side (see illus.). The size of a graben may vary; it may be only a few inches long or it may be hundreds of miles in length. The faults that separate a graben from the adjacent rocks are inclined from 50–70° toward the downthrown block and have displacements ranging from inches to thousands of feet. The direction of slip on these indicates that they are gravity faults. Graben are found in regions where the crust has undergone extension. They may form in the crests of anticlines or domes, or may be related to broad regional warpings.