Geobukbawi (meaning a turtle rock) is located at Namyang-ri, Seo-myeon, Ulleung-do and is named because it is shaped like a turtle. The turtle rock may be perceived differently depending where it is viewed from. The turtle rock was formed after the intrusion of phonolite (volcanic rock high content of silica) in the basaltic agglomerate formation, formed by early volcanic eruptions in Ulleung-do. Geobukbawi is supported by hard phonolite located to its right. It is a seastack, an isolated oceanic islet formed due to wind and wave erosions. A dark cooling zone, created when magma contacts with cold parent rock, is visible on the boundaries of phonolite. Geobukbawa is a famous tourist attraction in Ulleung-do as the turtle rock can be seen from the coastal road and is relatively easy to visit. Since the structure of lava flows is well-preserved, Geobukbawi is a geological attraction that has high academic and educational value.