 The two main islets, called "Seodo" (, "Western Island") and "Dongdo" (, "Eastern Island") in Korean, and "Ojima" (, "Male Island") and "Mejima" (, "Female Island") in Japanese, are apart.The Western Island is the larger of the two, with a wider base and higher peak, while the Eastern Island offers more usable surface area.Altogether, there are about 90 islets and reefs, volcanic rocks formed in the Cenozoic era, more specifically 4.6 to 2.5 million years ago.