To dwell in the clifts of the valleys, in caves of the earth, and in the rocks. To dwell in the cliffs of the valleys - They were obliged to take shelter in the most dangerous, out-of-the-way, and unfrequented places. This is the meaning.
Related Commentaries of Job 30:6
Job 30:6
6 To dwell in the clifts of the valleys, in cavesc of the earth, and in the rocks.