Formation of Columnar Joint
A columnar joint appears as a polyhedral pillar, such as a tetragonal, pentagonal, or hexagonal shape. Its shape depends on the rate at which the lava solidifies.
Columnar joints are often mistakenly known to be hexagonal columns only. However, you can observe that it is very diverse if you actually observe it.
Columnar joints often appear in basalt, where lava has cooled rapidly. When basalt lava cools down, shrinkage begins around the cooling nucleus. Most materials, except water, are reduced in volume when cooled to a solid. The polyhedron shape of columnar joints depends on the placement of the shrinking core.