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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.
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.
This type of jointing is typical of thick lava flows and shallow dikes and sills. [5] Columnar jointing is also known as either columnar structure, prismatic joints, or prismatic jointing. [6] Rare cases of columnar jointing have also been reported from sedimentary strata. [7]
The descending end of the oceanic plate melts and creates pressure in the mantle, causing volcanoes to form. Back-arc basins can form from extension in the overriding plate, in response to the displacement of the subducting slab at some oceanic trenches. This paradoxically results in divergence which was only incorporated in the theory of plate ...
The well-preserved columnar jointing up to 20 feet tall and 1 foot in diameter. The harsh columnar jointing is shorter in height and can have a diameter of 2 to 3 feet. Most columnar jointing is parallel but some have a curved or random orientation. [1] Deformation can also be seen in the columnar jointing that is found within this formation ...
A solidified lava pond that consists of a massive gray basalt with weakly developed columnar jointing occupies the crater of Vulcan. Radial, sinuous lava tubes 8 to 20 inches (200 to 510 mm) across and 300 feet (91 m) long are preserved on the northeast and northwest flanks of Vulcan.
The eastern and northern rim of the hole have low rim deposits of ejecta from the maar eruptions. These rest on the basalt flow where it is present or on older sediments. The ejecta at Kilbourne Hole contains dropstones launched as bombs, usually greater than 2.5 inches across [10] and a large number of xenoliths derived from the lower crust ...
It is named for jusangjeolli, the Korean term for columnar jointing. [1] The cliff was formed when the lava from the island's volcano Hallasan flowed into the sea of Jungmun. The lava formed many rocks that resemble columns of geometric shapes. It was designated as Natural Monument No. 443 [2] on January 6, 2005. [1]