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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.
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.
Flood basalt commonly displays columnar jointing, formed as the rock cooled and contracted after solidifying from the lava.The rock fractures into columns, typically with five to six sides, parallel to the direction of heat flow out of the rock.
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.
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]
As plate movement starts to carry the volcanoes away from their eruptive source, eruption rates start to die down, and water erosion grinds the volcano down. The final stages of eruption cap the seamount in alkalic flows. [55] There are about 100,000 deepwater volcanoes in the world, [56] although most are beyond the active stage of their life ...
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 ...