A planar, extensional rupture surface of a larger network of polygonal fractures that delimits a set of columns, the entire system resulting from contraction of the material.
A type of joint system.
The term columnar joint is rarely used in singular as columns are delimited by a network of fractures.
A network of joints, which forms mostly hexagons and pentagons, but polygons with three to nine sides have all been observed. Statistics on 3,033 columns measured at 50 different sites on Earth has found that half of the columns are hexagonal, one third are pentagonal, and the average polygon side is 5.71 (Hetényi et al. 2012).
Columnar-jointed lavas usually exhibit elongated columns (cm to m wide, m to 10 m high), with a height-to-side length ratio in general between 10 and 100 (Hetényi et al. 2012). The width of the columns has since long been linked to the cooling...
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