Noinbong, or Old Man Peak, is a 200 m high rock, formed after the volcano vent hardened. Interestingly, joints (horizontal or vertical fractures in a rock) of the rock resemble the wrinkles of an old man, which explains why it is called Old Man Peak. The peak is formed of trachyte. Thick viscous lava has contributed to the formation of a steeper wall, compared to its surroundings, with pointed rocks along with horizontal columnar-joints. As the magma (trachytic composition) ascended through the agglomerate deposits, it cooled and hardened, forming a lava-dome. Over time, agglomerate formation and upper part of the trachytic lava dome were eroded away. With only the conduit of the volcano remaining, the structure has developed into the Old Man Peak of today. Today, the trachyte dike resembles a sharp blade of a knife.