A deep fissure.

Roget 198: interval, interspace^†; separation etc. 44; break, gap, opening; hole etc. 260; 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 etc. 259; abra^†; barranca^†, barranco^†; clove [U.S.], gulch [U.S.], notch [U.S.]; yawning gulf; hiatus maxime [Lat.], hiatus valde deflendus [Lat.]; parenthesis etc. (interjacence) 228^†; void etc. (absence) 187; incompleteness etc. 53.    [interval of time] period etc. 108; interim (time) 106.    ... show more

Dutch: spleet, gletsjerspleet