Gangdonghwaam Hermitage Columnar Joints

Columnar joints are a common phenomenon found in extrusive volcanic rock. They are vertical, column-shaped joints typically found in basaltic lava flows, formed by the contraction that occurs when lava erupting from a vent cools rapidly. Columnar joints take the form of interconnected pillars with polygonal (triangular to hexagonal) cross-sections, produced by vertically developed joint planes. The columnar joints at Gangdonghwaam Hermitage were formed by volcanic activity during the Tertiary period of the Cenozoic era. Unlike typical columnar joints, however, they have developed in a variety of forms and orientations. Whereas most columnar joints develop vertically, the joint surfaces here have developed in various directions relative to the ground surface, including horizontal, vertical and inclined, with horizontal joints running parallel to or obliquely inclined to the ground surface predominating. The cross-sections observed range in shape from quadrilateral to heptagonal, with hexagonal forms the most common, followed by pentagonal ones. The cross-section of the Gangdonghwaam columnar joints forms a flower-like pattern, and it is thought that the village's name, Hwaam (花岩, meaning "flower rock"), derives from this. The diameter of the cross-sections ranges from 10 cm to 70 cm, averaging around 30–50 cm, with the horizontal joints having larger cross-sectional diameters than the vertical ones. Previous research has shown that the diameter of columnar joints is strongly influenced by the rate of cooling: joints of wide diameter are generally understood to have formed through slow cooling, while those of small, narrow diameter formed through relatively rapid cooling. This indicates that, at Gangdonghwaam, the joints running parallel to the ground surface formed through relatively slower cooling than the vertical joints.

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Where it is

Region

Buk-gu, Ulsan

Designation

Provincial Monument · 시도기념물