Orbicular Granite in Unpyeong-ri, Sangju

Orbicular granite refers to granite, a type of igneous rock, in which an orbicular structure - a ball-like, rounded structure - has developed. The orbicular granite of Unpyeong-ri contains numerous ball-shaped masses of diorite, and is understood to have formed 230 million years ago, when magma from within the earth rose to the surface during a period of crustal movement on the Korean Peninsula. It was found as eight boulder masses on the floor of the Ungok-ri valley, about 8 km southeast of Sangju; six lie submerged in the flowing water, and only two are visible above the surface. The spherical inclusions measure 5-13 cm in diameter, with dark edges. Because their shape resembles a turtle's shell, villagers also call them geobukdol (turtle stone); rock of this kind has been found at only about 100 locations worldwide. The Orbicular Granite in Unpyeong-ri, Sangju, is geologically very rare and unusual, and as it provides important material for research into how rocks are formed, it is designated and protected as a natural monument.

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Where it is

Region

Sangju, Gyeongbuk

Designation

Natural Monument · 천연기념물