a deep gorge (usually with the river)

gulf in mountain area

a deep opening or crack in the ground

gap, abyss

a break or opening in a wall, hedge etc

break, breach

a deep, narrow opening, usually with a stream, between hills or mountains

valley

a deep, narrow valley

gap in earth's surface

a deep ditch dug in the ground, e.g. for the draining of water

ditch, channel dug in earth