A geologic formation formed as hot volcanic rocks cool and contract forming polygonal columns which are usually vertical to the surrounding lava flow terrain but may be curved. Devil's Tower in Wyoming (USA) as a spectacular example of this kind of formation.

A system of fractures that splits a rock body into long prisms, or columns. It is characteristic of lava flows and shallow intrusive igneous flows.

Long joints, usually vertical, in volcanic rock that splits into columns as the rock cools and contracts.