Columnar structure

Definition of Columnar structure

(Geol.)	a structure consisting of more or less regular columns, usually six-sided, but sometimes with eight or more sides. The columns are often fractured transversely, with a cup joint, showing a concave surface above. This structure is characteristic of certain igneous rocks, as basalt, and is due to contraction in cooling.<- as at Giant's Causeway, Ireland ->
	See under Columnar.

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