'Chasm' or 'abyss' should work.
cleft, pass, or wash
Cavern
coulees
ravine
Canyon or ravine.
The word is ravine.
the ravine was so deep
Ravine means narrow valley.
The ravine was so rocky that the man triped Hope this helped
Ravi.
unseen
the ravine was so deep that the man plunged in to the heavy rocks
arroyo
Take the horse down to the ravine so that he won't be conspicuous to anyone who rides by.