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Columnar jointing identification and geology

A pattern of regularly spaced, polygonal typically hexagonal fractures that form in cooling lava flows and shallow intrusions as the rock contracts during solidification. The columns form perpendicular to the cooling surface and typically have five to seven sides. Column diameter is inversely related to cooling rate—faster cooling produces smaller columns. Field: volcanology. Example: The Giant's Causeway in Northern Ireland consists of approximately 40,000 basalt columns formed by the slow, uniform cooling of a Paleogene lava flow, producing remarkably regular hexagonal columns up to 12 m tall.. Related terms: Basalt, Joint, Lava flow, Contraction.

Sources, scope & corrections

These authoritative resources support category-level nomenclature, terminology, identification methods, and safety. When a specimen-specific safety warning appears, the public-health source listed here directly supports that precaution. They are not line-by-line citations for every other property on this entry, and natural specimens vary.

Editorial owner
GeoMiner
Last updated
2026-03-30T15:19:41.970235+00:00
Review status
Published; not independently peer-reviewed
  • USGS Thesaurus — U.S. Geological Survey. Controlled earth-science terminology used to describe USGS information resources.
  • Glossary of Geologic Terms — U.S. National Park Service. Geologic definitions prepared by the NPS Geologic Resources Inventory.

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Common questions

What does Columnar jointing mean in geology?
A pattern of regularly spaced, polygonal typically hexagonal fractures that form in cooling lava flows and shallow intrusions as the rock contracts during solidification. The columns form perpendicular to the cooling surface and typically have five to seven sides. Column diameter is inversely related to cooling rate—faster cooling produces smaller columns.
What is an example of Columnar jointing?
The Giant's Causeway in Northern Ireland consists of approximately 40,000 basalt columns formed by the slow, uniform cooling of a Paleogene lava flow, producing remarkably regular hexagonal columns up to 12 m tall.
Which earth-science field uses the term Columnar jointing?
Columnar jointing is used in volcanology.
Which terms are related to Columnar jointing?
Related terms in this reference are Basalt, Joint, Lava flow, Contraction.

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