The primary things eating away at the rock are wind and gravity combined with a cycle of freezing and thawing of water that gets trapped in the rock.
(The primary things; eating away; L:at the rock) (a cycle of freezing and thawing of water; gets; trapped in the rock) (water; gets trapped; in the rock)
The primary things a cycle of freezing and thawing of water water
eating away gets gets trapped
L:at the rock
trapped in the rock
in the rock