Pillow lava is created when lava meets cold water and cools down rapidly, with its surface becoming solidified in the shape of a circular pillow. The basalt lava, which erupted from Orisan Mountain in Pyonggang, North Korea during the mid-Cenozoic period, flowed southwest along the Hantangang River valley and met the cold water of Yeongpyeongcheon Stream here. As the surface of the lava that came contact with the river cooled rapidly, pillow lava was formed.

It is generally known to be created when lava erupts in the deep sea, but the Auraji Pillow Lava here comes from a very rare source as it is found on a riverside in an inland area that has no connection to the sea.