Abyss, Aperture, Blank, Breach, Break, Broaching, Canyon, Cavity, Chap, Check, Chimney, Chink, Clearing, Cleavage, Cleft, Clove, Col, Couloir, Crack, Cranny, Crater, Crevasse, Crevice, Cut, Deep, Defile, Dell, Depth, Dig, Diggings, Disclosure, Ditch, Donga, Draw, Excavation, Fault, Fissure, Fistula, Flaw, Fontanel, Foramen, Fracture, Furrow, Gap, Gape, Gash, Gorge, Groove, Gulf, Gully, Hiatus, Hole, Hollow, Incision, Inlet, Interval, Joint, Kloof, Lacuna, Leak, Mine, Moat, Notch, Opening, Orifice, Outlet, Overlook, Oversight, Pass, Passage, Passageway, Pit, Pore, Quarry, Ravine, Rent, Rift, Rime, Rupture, Seam, Shaft, Skip, Slit, Slot, Space, Split, Stoma, Trench, Valley, Void, Wadi, Well, Workings, Yawn