Samseonam, one of the major tourist sports of Ullueng-do, consists of 3 sea stacks: Ilseonam, Eseonam, and Samseonam. According to a legend, Emperor Jade got upset at three angels who were too fascinated by the beauty of Ulleung-do that they forgot to return to the heaven and changed them into rocks. The youngest angel of the three who was the slowest to return was cursed so that even grass would not grow on her rock. The islets composed of trachyte have well-developed joints (horizontal or vertical fractures in a rock) and tafoni (honeycomb weathering in rock). Pillar-shaped joints of Samseonam accelerated erosion of the rocks. Samseonam later became a sea-stack due to repeated processes of erosion. In the beginning, Samseonam was attached to the main island. The rockmass was separated from Ullueng-do due to differential erosion of the vertical joints. Only resistant rocks remained and became a sea-stack.