Quote Originally Posted by AZBuck View Post
Depending on the size of the original fracture joints, the remaining (now columns of) rock can be of various sizes. These are on the large size. Also, the Giant's Causeway is formed of basalt, a fairly weather resistant rock formed at depth. The columns shown here appear to be made of poorly consolidate tephra formed near the surface, and it will erode more easily. This ease of erosion makes it more likely that some of the columns will fall, exposing the sides of the remaining columns to greater erosion, causing them to erode more rapidly, etc.
AZBuck
Great explanation. Thanks,

Mark