Imjin River Columnar Joints (Hantangang River UNESCO Global Geopark)

This is the only place in Korea where beautiful vertical columnar joints, resembling a folding screen, stretch for several kilometers northward from the confluence of the Imjin River and Hantangang River (Dogampo) upstream along the Imjin River. Lava erupted from Orisan Mountain and the 680m peak in Pyeonggang-gun, North Korea, filled the lowlands of the ancient Hantangang River, forming a wide lava plateau across the Cheorwon-Pocheon-Yeoncheon area. Meeting the Imjin River, it flowed backward upstream, creating a basalt layer. After volcanic activity ceased, the lava plateau underwent river erosion, forming geometrically shaped basalt columnar joints along the river.

Joints refer to narrow cracks (or fissures) that develop on rock surfaces; when eroded, these cracks widen and the rock splits. Columnar joints are long, pipe-shaped joints, typically best developed in basalt. Due to contraction during lava solidification, vertical joints develop in square or hexagonal patterns around a central point. When eroded, hexagonal stone columns break away, creating beautiful columnar joint cliffs. In autumn, the cliffs of the columnar joints are dyed with ivy and stone maple, appearing even redder in the sunset light, hence also called Red Cliffs.