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
scissure
crevassed
crevasses
crevassing
bluff
boulder
cavern
cleave
escarpment
fjord
glacier
glen
hummocks
moraine
mountainside
outcrop
overhang
precipice
ridge
waterfall