In geology and geomorphology, a hogback is a long narrow ridge or series of hills with a narrow crest and steep slopes of nearly equal inclination on both flanks. Typically, this term is restricted to a ridge created by the differential erosion of outcropping, steeply dipping (greater than 30° - 40°), homoclinal, typically sedimentary strata. One side, its backslope, of a hogback consists of the surface (bedding plane) of steeply dipping rock stratum, which is called a "dip slope." Its other side, its escarpment or "frontslope" or "scarp slope", is an erosion face that cuts through the dipping strata that comprises the hogback. The name for this landform refers to its resemblance in outline to the back of a hog. It was named after a hogback, Hog's Back, of the North Downs in Surrey, England. This term is also used for any ridge with a sharp summit and steep slopes of nearly equal inclination on both flanks. It is sometimes applied to drumlins and, in Maine, to both eskers and ridges known as "horsebacks".