Columnar jointing in the Alcantara Gorge, Sicily

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. Columnar jointing occurs in many types of

igneous rocks Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma or ...

and forms as the rock cools and contracts. Columnar jointing can occur in cooling

lava flows Lava is molten or partially molten rock ( magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land o ...

and ashflow tuffs ( ignimbrites), as well as in some shallow

intrusion In geology, an igneous intrusion (or intrusive body or simply intrusion) is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety of forms and com ...

s. Columnar jointing also occurs rarely in sedimentary rocks if they have been heated by nearby hot magma. The columns can vary from 3 meters to a few centimeters in diameter, and can be as much as 30 meters tall. They are typically parallel and straight, but can also be curved and vary in diameter. An array of regular, straight, and larger-diameter columns is called a colonnade; an irregular, less-straight, and smaller-diameter array is termed an entablature. The number of sides of the individual columns can vary from 3 to 8, with 6 sides being the most common.Oregon State University > Volcano World > ... > Columnar Jointing
Accessed 29 December 2013.

Places

Some famous locations in the United States where columnar jointing can be found are the Devils Tower in Wyoming, the

Devils Postpile Devils Postpile National Monument is a U.S. National Monument located near Mammoth Mountain in Eastern California. The monument protects Devils Postpile, an unusual rock formation of columnar basalt, “all closely and perfectly fitted together ...

in California and the

Columbia River The Columbia River (Upper Chinook: ' or '; Sahaptin: ''Nch’i-Wàna'' or ''Nchi wana''; Sinixt dialect'' '') is the largest river in the Pacific Northwest region of North America. The river rises in the Rocky Mountains of British Columbia, C ...

flood basalts in Oregon, Washington and Idaho. Other famous places include the Giant's Causeway in Northern Ireland and Fingal's Cave on the island of Staffa, Scotland.

Devils Tower

The Devils Tower in Wyoming in the United States is about 40 million years old and high. Geologists agree that the rock forming the Devils Tower solidified from an intrusion but it has not been established whether the magma from this intrusion ever reached the surface. Most columns are 6-sided, but 4, 5, and 7-sided ones can also be found.

Giant's Causeway

The Giant's Causeway ( Irish: ''Clochán An Aifir'') on the north Antrim coast of Northern Ireland was created by volcanic activity 60 million years ago, and consists of over 40,000 columns. According to a legend, the giant Finn McCool created the Giant's Causeway, as a

causeway A causeway is a track, road or railway on the upper point of an embankment across "a low, or wet place, or piece of water". It can be constructed of earth, masonry, wood, or concrete. One of the earliest known wooden causeways is the Sweet Tra ...

to Scotland.

Sōunkyō Gorge

Sōunkyō Gorge, a part of the town of Kamikawa, Hokkaido, Japan, features a 24-kilometer stretch of columnar jointing, which is the result of an eruption of the Daisetsuzan Volcanic Group 30,000 years ago.

Deccan Traps

The late Cretaceous

Deccan Traps The Deccan Traps is a large igneous province of west-central India (17–24°N, 73–74°E). It is one of the largest volcanic features on Earth, taking the form of a large shield volcano. It consists of numerous layers of solidified flood ...

of India constitute one of the largest volcanic provinces of Earth, and examples of columnar jointing can be found in St. Mary's Island in the state of Karnataka.

High Island Reservoir

Formed in Cretaceous, the columnar rocks are found around the reservoir and the islands nearby in Sai Kung, Hong Kong. It is special that the rocks are not mafic, but felsic tuff instead. Hexagonal volcanic tuffs at East Dam of High Island Reservoir 1

Makhtesh Ramon

The columnar jointed sandstone of the ''HaMinsara'' (Carpentry Shop) in the makhtesh (erosion

cirque A (; from the Latin word ') is an amphitheatre-like valley formed by glacial erosion. Alternative names for this landform are corrie (from Scottish Gaelic , meaning a pot or cauldron) and (; ). A cirque may also be a similarly shaped landform ...

) of

Makhtesh Ramon Makhtesh Ramon ( he, מכתש רמון; ''lit.'' Ramon Crater/Makhtesh ; ar, وادي الرمان, links=no) is a geological feature of Israel's Negev desert. Located some 85 km south of the city of Beersheba, the landform is the world' ...

Negev desert The Negev or Negeb (; he, הַנֶּגֶב, hanNegév; ar, ٱلنَّقَب, an-Naqab) is a desert and semidesert region of southern Israel. The region's largest city and administrative capital is Beersheba (pop. ), in the north. At its southe ...

, Israel. Cerro Koi 6520 11

Cerro Kõi

There are several examples of columnar jointed sandstones in the greater Asunción region of Paraguay. The best known is Cerro Kõi in

Areguá Areguá () is the capital of Central Department in Paraguay, located from the capital, Asunción. The city lies between Ypacaraí Lake to the east and hills to the west. Areguá is known for its colonial architecture and historic cobbleston ...

, but there are also several quarries in Luque.

Mars

Several exposures of columnar jointing have been discovered on the planet Mars by the High Resolution Imaging Science Experiment ( HiRISE) camera, which is carried by the Mars Reconnaissance Orbiter (MRO).

Sawn Rocks

Sawn Rocks, in Mount Kaputar National Park close to Narrabri, New South Wales, Australia, features 40 meters of columnar jointing above the creek and 30 meters below the surface.Sawn Rocks walking track, Mount Kaputar National Park
NSW National Parks and Wildlife Service. Retrieved 3 January 2019.

Basaltic Prisms of Santa María Regla

Alexander von Humboldt documented the prisms located in Huasca de Ocampo, in the Mexican state of Hidalgo.

Columnar Basalt of Tawau (Batu Bersusun)

River flows through the area of columnar basalt. One section is seen vertically high on river bank. The rest lays on river bank. Water flows from the lowest area forming waterfall and scenic view. Location is at Kampung Balung Cocos, Tawau

References

External links

*Aydin, A., and J. Zhong (nda
Columnar Joints

Stanford University, Stanford, California. {{Structural geology Igneous rocks Geomorphology Structural geology Metamorphic rocks