beach or beach-and-dune sediments piled up by the action of waves and currents on a shoreline beyond the present limit of storm waves and the reach of ordinary tides. They occur occurring singly or as one of a series of approximately parallel ridges that are roughly parallel to the shoreline. Erosional ridges Dendritic ridge In typical dissected plateau terrain, the stream drainage valleys will leave intervening ridges. These are by far the most common ridges. These ridges usually represent slightly more erosion resistant rock, but not always – they often remain because there were more joints where the valleys formed or other chance occurrences. This type of ridge is generally somewhat random in orientation, often changing direction frequently, often with knobs at intervals on the ridge top. Strike ridge A strike ridge is an asymmetric ridge created by the differential erosion of a hard, erosion-resisitent, dipping layer of rock sandwiched between layers of weaker, more easily eroded rock. A strike ridge has a distinctly gentler sloping side (dip slope), that roughly parallels the inclined layer of erosion-resisitent rock. The opposite side of a strike ridge is relatively short, steep or cliff-like slope (scarp slope) that cuts across the tilted layers of rocks. In foldbelts such as the Ridge-and-Valley Appalachians, they form series of long, parallel, straight to arcuate ridges. Stike ridges are subdivided into cuestas, flatirons, homoclinal ridges, and hogbacks. Reef A term applied by early explorers and settlers in the western United States to ridges that formed a rocky barrier to land travel, by analogy with ocean reefs as barriers to sea travel. Examples include Capitol Reef National Park and the San Rafael Reef. The usage may have originated with sailors during the Australian gold rushes to describe the gold-bearing ridges of Bendigo, Australia. Glacial ridges Moraines and eskers Glacial activity may leave ridges in the form of moraines and eskers. An arête is a thin ridge of rock that is formed by glacial erosion. Pressure ridge (ice) An ice pressure ridge is a ridge of deformed ice along the boundaries of individual ice floes when the ice floes on a lake or ocean collide and compress their edges. The average height of a sea ice pressure ridge is between 5 to 30 meters. Tectonic and Structural ridges Oceanic spreading ridge In tectonic spreading zones around the world, such as at the Mid-Atlantic Ridge, the volcanic activity forms new