Columnar jointing is a geological phenomenon where rock, typically basalt, fractures into large, column-like structures. This occurs when lava cools and contracts, creating cracks that extend downward, forming distinct vertical columns. The cooling process is often influenced by the thickness of the lava flow and the surrounding environment. These columns can vary in size and shape, often appearing hexagonal, although they can also be pentagonal or octagonal. Columnar jointing is commonly seen in locations like Giant's Causeway in Northern Ireland and Devil's Postpile in California, showcasing the unique patterns formed by natural processes.