This group collects the Volcanic Formations subcategory's members whose own description identifies them by their columnar basalt jointing or columnar-jointed rock, the hexagonal or polygonal rock columns that form as a thick lava body cools slowly and cracks into regular vertical joints. Devils Tower, Giant's Causeway, Fingal's Cave and the sea cliffs at Tojinbo are among this group's best documented columnar formations, kept together because their defining feature is the jointing pattern itself rather than the specific volcano type that produced the original lava or intrusion.
Facts
Comparison
Defining ProcessIntersecting closely spaced fractures forming a regular array of polygonal columns as lava cools and contracts. 1 All Columnar Basalt Formations
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Sources
1. Wikipedia: Columnar jointing
WikipediaColumnar jointing, lead sectionQuote, Columnar jointing, lead section
Columnar jointing is a geological structure where sets of intersecting closely spaced fractures, referred to as joints, result in the formation of a regular array of polygonal prisms, or columns.
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