How do hexagonal stone pillars form in nature?
Some cliffs are made of massive, perfectly hexagonal stone pillars formed by cooling lava.
This phenomenon, known as columnar jointing, occurs when thick lava flows cool and contract. As the rock shrinks, it cracks into geometric shapes, most commonly hexagons. A famous example is the Giant's Causeway in Northern Ireland, which contains 40,000 interlocking basalt columns.
Nerd Mode
Columnar jointing is a geological process that occurs during the cooling of thick, basaltic lava flows. As the lava cools from the outside in, it contracts and loses volume. This contraction creates internal stresses that are eventually relieved through the formation of vertical cracks. These cracks propagate downward as the cooling continues, creating the distinctive pillar-like structures.The hexagonal shape is the most common because it is the most efficient way to release the maximum amount of energy with the least amount of cracking. This geometric efficiency is similar to the patterns found in honeycombs or drying mud. While hexagons are the most frequent, columns can also have three, four, five, or even seven sides depending on the cooling rate and mineral composition.The Giant’s Causeway in County Antrim, Northern Ireland, is the world's most famous example, formed approximately 50 to 60 million years ago during the Paleogene Period. It consists of roughly 40,000 interlocking basalt columns that were created by intense volcanic activity. Another notable site is Devils Postpile National Monument in California, where columns reach heights of up to 60 feet. Geologists at institutions like the University of Liverpool have used cooling experiments to prove that the size of the columns is directly related to how fast the lava cools.
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FP-0004047 · Feb 18, 2026