A ridge is best thought of as a spine traversing the top of mountains, hills, or any raised or upward-projecting landform. It is one of the most ubiquitous features of the Earth. Ridges are crossed, surveyed, cut through by roads, gained, climbed, walked, taken, and lost. Our eye measures and records their shapes: shoulder, spur, reef, rib, couch, neck, roostercomb, and hogback, to name a few. Developers use such terms as Ridgecrest, Ridgeﬁeld, Ridgemanor, and Ridgehaven to suggest a place of superior view, where in fact no ridge may exist. The Flatirons of Boulder, Colorado, are a dramatic example of a hogback ridge created by uplifting; the ridge and valley system of the Appalachian Mountains was formed by folding, and is also a superb example of ridges formed by erosion. The dominant feature of the Earth is the midocean ridge, a thirty-thousand-mile-long system of underwater fault ridges stitching the planet.