Pylvässymmetria

Pylvässymmetria, also known as columnar symmetry, refers to a type of symmetry observed in certain geological formations, particularly in the columnar jointing of volcanic rocks. This phenomenon occurs when lava cools and contracts, forming characteristic polygonal columns, most commonly hexagonal. The formation of these columns is a result of tensile stresses that develop as the molten rock solidifies. As the lava cools, it shrinks, and cracks begin to propagate. These cracks tend to propagate in a way that minimizes the energy required, leading to the formation of relatively uniform, often hexagonal, shapes.

The regularity of these columns is a striking visual characteristic. While hexagonal columns are the most common, other polygonal shapes such as pentagonal or even square columns can also be found. The size of the columns can vary greatly, from a few centimeters to several meters in diameter. Pylvässymmetria is a direct consequence of the physics of cooling and contraction in a viscous material, demonstrating a natural tendency towards efficient crack propagation patterns. Examples of columnar jointing can be seen in many volcanic regions worldwide, such as the Giant's Causeway in Northern Ireland or the Devil's Postpile National Monument in California. This geological feature is not only aesthetically pleasing but also provides insights into the cooling processes of ancient lava flows.