Songgotbong, a 430 m high peak, is called after the shape of the peak which looks like an auger or a gimlet. The lava dome (circular mound-shaped protrusion resulting from several extrusions of lava) was formed by viscous magma being erupted effusively onto the surface and then cooling around the vent. Over time, agglomerate formation and upper part of the trachytic lava dome were eroded away, forming steep slopes and the pointed peak. Peculiar geological features including horizontal and vertical joints, irregular joints, and holes are found on the trachytic lava dome. Only 4 of the 8 holes, formed at the rear of Songgotbong, are visible from Cheonbu port. A legend has it that the holes were made by the Great Jade Emperor to take sinless humans to the heaven.