abysm, abyss, arroyo, box canyon, breach, break, canyon, cavity, chap, chasm, check, chimney, chine, chink, cleft, cleuch, clough, comb, coulee, couloir, crack, cranny, crevasse, crevice, cut, cwm, defile, dell, dike, ditch, donga, draw, esker, excavation, fault, fissure, flaw, flume, fracture, furrow, gap, gape, gash, gorge, groove, gulch, gulf, gully, hogback, hole, horseback, incision, joint, kame, kloof, leak, moat, notch, nullah, opening, pass, passage, ravine, rent, ridge, rift, rime, rupture, saddle, saddleback, scissure, seam, slit, slot, spine, split, trench, valley, void, wadi