Surface erosion stripped away the younger rock layers while, over time, water seeped into the long, straight cracks.
(Surface erosion; stripped away; the younger rock layers; T:while, over time, water seeped into the long, straight cracks) (water; seeped; into the long, straight cracks; T:over time)
Surface erosion water
stripped away seeped
the younger rock layers T:while, over time, water seeped into the long, straight cracks
into the long, straight cracks T:over time