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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.
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.
A long-quiet yet massive super volcano, dubbed the "Long Valley Caldera," has the potential to unleash a fiery hell across the planet, and the magma-filled mountain has a history of doing so.
The rim cliffs, measuring about 40 feet (12 m) in height, are composed of basalt and exhibit clear columnar jointing (a feature common to many basalt cliffs, including those of Devils Postpile National Monument near Yosemite National Park and Moses Coulee in the Channeled Scablands of Washington), with characteristic reddish-purple, polygonal ...
The word lava comes from Italian and is probably derived from the Latin word labes, which means a fall or slide. [2] [3] An early use of the word in connection with extrusion of magma from below the surface is found in a short account of the 1737 eruption of Vesuvius, written by Francesco Serao, who described "a flow of fiery lava" as an analogy to the flow of water and mud down the flanks of ...
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 ...