When water gets inside cracks, it freezes and expands, then thaws and contracts, pushing on the joints and splitting the rock.
(water; gets; L:inside cracks) (it; freezes; T:When water gets inside cracks) (it; expands then; T:When water gets inside cracks)
water it it
gets freezes expands then
L:inside cracks
T:When water gets inside cracks
T:When water gets inside cracks