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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.
Columnar jointing is a distinctive type of joints that join together at triple junctions either at or about 120° angles. These joints split a rock body into long, prisms or columns. These joints split a rock body into long, prisms or columns.
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.
Columnar Joints are joints that cut the formation vertically in (typically) hexagonal columns. These tend to be a result of cooling and contraction in hypabyssal intrusions or lava flows. Desiccation cracks are joints that form in a layer of mud when it dries and shrinks. Like columnar joints, these tend to be hexagonal in shape.
Dverghamrar (also known as "Dwarf Cliffs" or "Dwarf Rocks") [2] is a geological formation in Southern Iceland, consisting of columnar jointing of volcanic rocks. The formation appears as vertical, hexagonal columns of varying heights. Situated off the Ring Road in the town of Kirkjubæjarklaustur, the cliffs are a popular destination for ...
The most disruptive in recent times was the 2010 eruption of the Eyjafjallajokull volcano, which spewed huge clouds of ash into the atmosphere and led to widespread airspace closures over Europe.
The small size of the columnar joints indicates that the erupted lava was cooled immediately and are mainly located on the dome's summit. [31] Ember Ridge Northeast, the smallest subglacial dome of Ember Ridge, comprises one lava flow that has a thickness no more than 40 m (130 ft). [ 32 ]