THESAURUS
abysm, abyss, arroyo, box canyon, breach, break, chap, chasm, check, chimney, chink, cleft, cleuch, clough, col, coulee, couloir, crack, cranny, crater, crevice, cut, cwm, deep, defile, dell, depth, dike, ditch, donga, draw, excavation, fault, fissure, flaw, flume, fracture, furrow, gap, gape, gash, gorge, groove, gulch, gulf, gully, hole, hollow, incision, joint, kloof, leak, moat, notch, nullah, opening, pass, passage, pit, ravine, rent, rift, rime, rupture, scissure, seam, shaft, slit, slot, split, trench, valley, void, wadi, well, yawning abyss
ROGET THESAURUS
Interval
N
interval, interspace, separation, break, gap, opening, hole, chasm, hiatus, caesura, interruption, interregnum, interstice, lacuna, cleft, mesh, crevice, chink, rime, creek, cranny, crack, chap, slit, fissure, scissure, rift, flaw, breach, rent, gash, cut, leak, dike, ha-ha, gorge, defile, ravine, canon,
crevasse, abyss, abysm, gulf, inlet, frith, strait, gully, pass, furrow, abra, barranca, barranco, clove, gulch, notch, yawning gulf, hiatus maxime, hiatus valde deflendus, parenthesis, void, incompleteness, period, interim (time), with an interval, far between, breachy, rimose, rimulose, at intervals, longo intervallo.