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Basalt columns seen on Porto Santo Island, Portugal. Columnar jointing of volcanic rocks exists in many places on Earth. Perhaps the most famous basalt lava flow in the world is the Giant's Causeway in Northern Ireland, in which the vertical joints form polygonal columns and give the impression of having been artificially constructed.
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 (basalt prisms), or columns. Columnar jointing occurs in many types of igneous rocks and forms as the rock cools and contracts.
The Giant's Causeway (Irish: Clochán an Aifir) [1] is an area of approximately 40,000 interlocking basalt columns, the result of an ancient volcanic fissure eruption. [3] [4] It is located in County Antrim on the north coast of Northern Ireland, about three miles (4.8 km) northeast of the town of Bushmills.
The tops of the postpile columns are accessible to visitors. The shapes of the column cross sections are seen clearly here. The name "Devils Postpile" refers to a dark cliff of columnar basalt. Radiometric dating indicates the formation was created by a lava flow at some time less than 100,000 years ago. [17]
Columnar basalt formations. Subcategories. This category has the following 4 subcategories, out of 4 total. I. Columnar basalts of Iceland (7 P) N. Columnar basalts ...
View from the depths of the cave with the island of Iona visible in the background, 2008 Basalt columns inside Fingal's Cave, 2022. Fingal's Cave is formed entirely from hexagonally jointed basalt columns within a Paleocene lava flow [2] and is similar in structure to both the Giant's Causeway in Northern Ireland and Ulva.
The Sheepeater Cliffs are a series of exposed cliffs made up of columnar basalt in Yellowstone National Park in the United States.The lava was deposited about 500,000 years ago during one of the periodic basaltic floods in Yellowstone Caldera, and later exposed by the Gardner River.
Cooling joints are columnar joints that result from the cooling of either lava from the exposed surface of a lava lake or flood basalt flow or the sides of a tabular igneous, typically basaltic, intrusion. They exhibit a pattern of joints that join together at triple junctions either at or about 120° angles.