There are three volcanoes in the Korean Peninsula. The biggest one is Mt. Baekdu with the last activity being recorded in 1903. The second volcano is Mt. Halla, which was created by the volcanic activities occurred about 1.8 million years ago. The last one is the Ulleung Island, which was formed from erupted magma in the East Sea.

  Mt. Baekdu, with a height of 2,744m, is the highest mountain in the Korean Peninsula. It is also called as Mt. Changbai (長白山) in China. Its slope is relatively gentle until 1,000m altitude, but becomes steep at about 1,800m above sea level. There is a caldera lake, called Cheonji (天池), which was created by collapse of the summit part of the mountain. It seems to have been large scale eruptions in A.D. 946 and 947 during the Goryeo dynasty. Many small eruptions were also occurred in A.D. 1014, 1201, 1401, 1597, 1702, and 1903.

  Mt. Halla in Jeju Island was created by volcanic activities about 1.8 million years ago and its height is about 1,950m. The general form of the mountain is aspite whose slope is rather gentle, whereas its summit area has a tholoide form. The mountain has a crater lake, called Baekrok-dam (白鹿潭), on the top of the mountain, and there are many lava caves and coastal waterfalls around the mountain. According to the Goryeosa (高麗史) or the History of Goryeo, there seemed to be volcanic eruptions in A.D. 1002 and 1007. Ulleung Island is a volcanic island, rose from the depth of 2,000m underwater to 984m above the sea level. It is considered as a kind of double volcano, where a new volcano was created on a caldera at the center of the island.