Mountains and Hills

Between the Korean peninsula and Manchuria flow, in opposite directions, the two largest rivers of the region, the Amnokgang (Yalu) and Dumangang (Tumen), both originating at Mt. Baekdusan (2,744m), the highest mountain in the region. The peninsula is surrounded by the Yellow Sea, the East Sea, and the South Sea.

Mt. Seoraksan National Park

Nearly 70 percent of the Korean Peninsula is covered by mountains and hills. Low hills in the southern and the western regions give way gradually to increasingly higher mountains toward the eastern and the northern areas. On the whole, the western and southern slopes of the peninsula are wide with some plains and basins along rivers, while the eastern slope is very steep as high mountains precipitate into the East Sea.

Most of the high mountains are located along the Taebaek mountain range which runs parallel to the east coast, roughly north-to-south. West of this range are the drainage basins of the Hangang and Geumgang rivers. This range extends to the Nangnim range in North Korea, forming the geological and geomorphological backbone of the peninsula and constituting the watershed between the western and eastern slopes of the peninsula. Mt. Nangnimsan (2,014m), Mt. Geumgangsan (1,638m), Mt. Seoraksan (1,708m), and Mt. Taebaeksan (1,567m) are some of the highest peaks along these ranges. Just southwest from the Taebaeksan range is the Sobaeksan range, which culminates in the massive Mt. Jirisan (1,915m). This range was historically a great barrier between the central and southern parts of the peninsula, and also between the eastern and western regions in the south. The Nakdong river basin is thus segregated in southeastern Korea. The Gaemagowon Plateau, the so-called "Roof of Korea," located in the northwestern corner of the peninsula, has an average elevation of about 1,500 meters above sea level.

The landmass of the peninsula is rather stable geologically in spite of its proximity to Japan; it has neither active volcanoes nor strong earthquakes. There are, however, a few dead volcanoes that were formed during the Pleistocene era. Mt. Baekdusan is famous for a large caldera lake, "Cheonji," meaning heavenly tarn. Mt. Hallasan in Jejudo island, the highest mountain in South Korea, was recorded to have had minor volcanic activity in the early 11th century. It has a small crater lake, "Baengnokdam," and there are about 400 parasitic cones in its piedmont.

About two-thirds of the Korean Peninsula is composed of pre-Cambrian metamorphic and granitic rock. Although the distribution of sedimentary rock is very limited, limestone is quite abundant in some regions and a number of limestone caves can be found, some of which are tourist attractions. Among the most famous caves are Gossigul, Gosugul and Seongnyugul, all of which are adorned with stalagmites and stalactites.


Rivers and Plains

Most of major rivers flow into the Yellow Sea and a few into the South Sea, draining the western and southern slopes of the peninsula. Considering its size, Korea has a relatively large number of long rivers, six of them exceeding 400 kilometers. The discharge of rivers fluctuates very much due to the summer monsoon. In the summertime, rivers swell with heavy rainfall, flooding valley plains every once in a while. In drier seasons, the water level drops and often much of the river bed is exposed. Typhoons, which hit the southern part of the peninsula once every two or three years, also bring heavy rainfall in late summer and early autumn.

The Han-gang River

In the past, rivers were important for transportation. Historical capitals such as Pyeongyang and Buyeo are located adjacent to major rivers, as is Seoul. After the introduction of railroads and automobiles, however, the importance of rivers for transportation has decreased sharply, and rivers are now used mainly for the irrigation of rice fields and power generation. During the last two decades a number of huge dams have been constructed for flood control, electricity, and irrigation. But these dams have gradually begun to play a major role as reservoirs for piped water supply to large cities and industrial plants as a result of rapid urbanization and industrialization nationwide.

Most farming fields are narrow floodplains developed along rivers, especially in their lower reaches. These plains serve as the major rice-producing lands. Large tidal differences at the mouths of major rivers flowing into the Yellow Sea inhibited the development of deltaic plains, although rivers transport large amounts of sediment during floods. Only the Nakdonggang flowing into the South Sea has a small delta at its mouth. Erosional basins along rivers in areas of granitic rocks have also served as agricultural regions since ancient times. Many large cities such as Chuncheon, Cheongju, and Wonju are located in such basins.


Coasts

Korea has a long coastline divided into the east, west and south coasts. The east coast has small tidal differences, a third of one meter at the most, and a relatively smooth shoreline with few islands offshore. The Taebaek range runs closely along the East Sea. Where mountains protrude from the Taebaeksan range, coasts are rocky in general, but some beaches are found in places into which small streams carry sediment from the high mountains. In many instances, the beaches take the form of sand spits and bars enclosing lagoons, which are notable features of the east coast. Along the coast between Wonsan and Gangneung are located a series of lagoons, including Gyeongpo and Hwajinpo, two famous resorts. The highway connecting Gangneung and Seoul has been expanded recently, reducing the travel time between the central region and the east coast.

The Dadohae National Park at the tip of the Korean Peninsula

The shorelines of the south and west coasts are very irregular with innumerable small peninsulas and bays as well as a large number of islands. The west coast facing the Yellow Sea, which is very shallow, has large tidal ranges, which rise above 10 meters in places. Harbors have been difficult to develop while tidal flats are common coastal features especially in bays into which rivers discharge sediment during floods. Tidal flats have been reclaimed from ancient times mainly for rice fields, but since the 1970s, the reclamation grew in terms of magnitude. The Saemangeum Project, the largest such project ever undertaken, seeks to reclaim a total of 40,100 hectares of the flats through the construction of huge dikes, but it faces strong opposition from environmental groups.

The south coast shows a typical ria shoreline, a coastal zone which has been submerged. The length of coastline is nearly eight times longer than its straight-line distance, and its indentation is far greater than that of the west coast. The tidal ranges are relatively small at two to five meters, and tidal flats are not as wide as along the west coast. Although mountains face the sea, there are few beaches and sea cliffs along the mainland coast, as innumerable islands prevent the penetration of waves from offshore. Narrow straits between the mainland and islands are associated with extremely rapid tidal currents. At Uldolmok toward the western end of the south coast, the tidal current reaches up to 13 knots.