Columnar joints are lava columns formed by volcanic lava during cooling. They generally have four corners and a hexagonal box is round. One of Asia's largest columnar joint zones is in Tengchong, a Jeju Island in South Korea. The locals of Tengchong called this columnar joint image God Pillar. The temperature at which the volcanic magma erupts is 1200 degrees Celsius. When the magma is cooled to 800 to 900 degrees Celsius, the magma crystallizes to form columnar joints. Since the magma contains hexagonal plagioclase, olivine, amphibole, pyroxene and other minerals, it forms a hexagonal cylinder after cooling. This is also the largest, best-preserved, and shortest columnar joint found in China so far.