'Clefts of the Rock' in the Bible

To go into the clefts of the rocks, and into the tops of the ragged rocks, for fear of the LORD, and for the glory of his majesty, when he ariseth to shake terribly the earth.

And they shall come, and shall rest all of them in the desolate valleys, and in the clefts of the rocks, and upon all thorn-hedges, and upon all pastures.

ye that inflame yourselves among the oaks, under every green tree; that slay the children in the valleys, under the clefts of the rocks?