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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.
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.
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]
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.
Columnar jointing in basalt, Marte Vallis. Image courtesy High Resolution Imaging Science Experiment, University of Arizona. [1] Marte Vallis is a valley in the Amazonis quadrangle of Mars, located at 15 North and 176.5 West. It is 185 km long and was named for the Spanish word for "Mars". [2]
The dacite is characterized by columnar joints, 5 to 40 cm (2.0 to 15.7 in) in diameter, and exhibiting locally radiating patterns. This volcanic centre formed in a subglacial to englacial environment between 130,000 and 90,000 years ago, as shown by the existence of distinctive, radial columnar joint patterns, a glassy to fine-grained matrix ...
Tyrrhena Terra is typical of the southern Martian terrae, with heavily cratered highlands and other rugged terrain. It contains the large volcano Tyrrhena Patera, one of the oldest volcanoes on Mars. [2] Its largest crater is Herschel. Licus Vallis and the Ausonia Montes are other major features in the region. Some channels and dunes are ...