chasm
ˈkaz(ə)m
noun
a deep fissure in the earth’s surface.
a chasm a mile long
gorge,abyss,canyon,ravine,gully,gulf,pass,defile,couloir,crevasse,cleft,rift,rent,pit,void,crater,cavity,hole,opening,gap,fissure,crevice,hollow,chine,bunny,clough,gill,thrutch,cleuch,heugh,gulch,coulee,flume,arroyo,barranca,quebrada,nullah,khud,sloot,kloof,donga,khor