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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.
Thurston Lava Tube in Hawaii Volcanoes National Park, Hawaii. The step mark, more visible on the right wall, indicates the depth at which the lava flowed for a period of time. Rare characteristics of lava tubes are lava pillars. This is the Manjanggul lava pillar located in the Manjanggul lava tubes, on the island of Jeju-do, Korea.
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]
A new image from the James Webb Space Telescope (JWST) shows at least 17 dust rings – resembling a fingerprint – created by a rare type of star and its companion, locked in a celestial dance.
One way in particular that joints can be formed is due to fluid pressure, as well as at the crest of folds in rocks. This occurs at the peak of the fold or due to the fluid pressure because a localized tensile stress forms, eventually leading to jointing. [2] Another way in which joints form is due to the change in the weight of the overburden ...
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.