|A Spectacular Geological Museum|
Jeju Island was created by the volcanic activities that went through four stages between 1.2 million and 250,000 years ago. With diverse and unique volcanic features and beautiful landscape stretching in every direction, the entire island is a virtual volcano museum.
Formed in the Quaternary Period of the Cenozoic Era, which is a relatively recent geological past, the initial volcanic landforms of Jeju Island have been well preserved, providing precious information about global volcanism.
|Some of the best examples of Jeju Island’s volcanic landforms are Mt. Halla, its 368 parasitic cones, and the lava tubes formed by explosive eruptions of basaltic lava. Specifically, the mountain has the world’s largest number of parasitic cones (called oreum in the Jeju dialect) to be derived from a single volcano. These sites are highly regarded not only for their superb scenic beauty but also for their research value as examples representing the earth’s geological history.|
| The UNESCO World Heritage Committee selects a World Natural Heritage in view of the site’s natural beauty, properties as a habitat for endangered species and its geological features that shed light on the history of the earth. In other words, the site’s outstanding scenic beauty is not the sole condition for an inscription on the World Heritage List, but its exceptional geological and ecological values are also assessed as important prerequisites. As such, more weight is placed on the site’s objective qualities, including its contributions to scientific research, rather than on aesthetic considerations, which can be inherently subjective. |
In 2007, UNESCO listed Jeju Volcanic Island and Lava Tubes as a World Natural Heritage in recognition of its landscape of surpassing natural beauty, unique volcanic landforms and ecology. Juju Volcanic Island and Lava Tubes, comprised of three sites - Mt. Halla Natural Reserve, the Geomunoreum Lava Tube System and Seongsan Sunrise Peak- is the first natural site in Korea to be placed on UNESCO’s World Heritage List.
|Jeju Island has an oval shape and is 70 kilometers from east to west and 30 kilometers from north to south. It is 1,847.2 square kilometers in area, about three times as large as Seoul, the capital city of Korea. At the center of the island is Mt. Halla, a volcano rising 1,950 meters above sea level, and the mountain’s gentle slopes descend from its peak all the way down into the sea, making the island look like one big mountain. The area covering 151.35 square kilometers around the mountain (about 8.3 percent of the entire island) has been designated as a natural reserve. |
| The overall shape of Mt. Halla is simple, but it features the diverse topography and geology of a volcanic mountain, including a lake-filled crater at the summit, a cluster of rocky cliffs to the southwest of the summit composed of rock pillars with bizarre shapes (columnar joints formed by cooling of lava), and 40 or more parasitic cones. The mountain has a wide range of climate conditions and distinct vegetation distributions along altitudinal gradient, displaying magnificent landscapes varying by season and location.|
|Baengnokdam (White Deer Lake), an oval-shaped crater lake at the summit of Mt. Halla, has an east-west diameter of 700 meters and north-south diameter of 500 meters. It is 111 meters deep and 1,720 meters in circumference. On the whole, Mt. Halla is an aspite-type shield volcano (a volcano with gradual slopes formed from fluid lava flows traveling across a broad area of land), but its|
|steep summit has the characteristics of a lava dome (a mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano). Mt. Halla is unique in that it is a shield volcano which erupted on a continental tectonic plate. Shield volcanoes are not common all over the world, taking up less than 10 percent of the world’s volcanoes. Furthermore, most other shield volcanoes occur in oceanic plates.|
|The mountain is a habitat for a wide variety of plants from its base up to the top. It has the distinct vertical distribution of flora along its slopes from subtropical to temperate and polar plants. Its flora encompasses various species growing in a wide range of climate zones from the northern limits of the subtropical zone to the southern limit of the polar zone.|
Mt. Halla is a habitat for more than 1,800 plant species, almost half of over 4,000 species growing in Korea; it is in itself a virtual ecological park and botanical garden. Especially noteworthy are a variety of arctic-alpine plants including many endemic species and the forest of Korean fir (Abies koreana) on the slopes near the summit.
|The arctic-alpine plants inhabiting Mt. Halla include 33 species endemic to Jeju Island, one genus endemic to Korea, 56 species for which Jeju is their southern range limit, and three species for which the island is their northern range limit. These plants are valuable plant genetic resources of excellent research value.|
Jeju Island has over 90 percent of its land covered with basalt, a dark-colored rock of volcanic origin. Parasitic cones, distributed all over the island from Mt. Halla to the coastal areas, contribute to the volcanic landscapes unique to this island.
Jeju has a total of 368 parasitic cones created as a result of repeated volcanic activities that occurred more than 100 times between 1.2 million and 250,000 years ago in the vicinity of Mt. Halla. Considering the size of the island, it is the highest concentration of parasitic cones in the world.
Parasitic cones have created numerous scenic spots all over the island, which are praised for their majestic beauty, including Baengnokdam at the peak of Mt. Halla, Seongsan Sunrise Peak (Ilchulbong), Suwol Peak, Mt. Songak, Mt. Sanbang and Sangumburi Crater.
While Mt. Halla and its 368 parasitic cones are volcanic landforms viewable above ground, lava tubes are the result of volcanic activities manifested below the ground.
One of the numerous parasitic cones distributed all over Jeju Island, Geomunoreum (465 meters above sea level) is located to the northeast of the island. The volcano erupted repeatedly between 300,000 and 100,000 years ago, and lava flows from these eruptions traveled down its northeastern slopes to the coastline, creating over 20 caves along their course. Collectively called the Geomunoreum Lava Tube System, this site retains traces that show how these massive lava tubes were formed and evolved into their current state. The lava tube system consists of 20 or more lava tubes of various lengths, structures and components. Among them, the Geomunoreum volcano and five lava tubes of exceptional qualities - Manjang Cave, Gimnyeong Cave, Bengdui Cave, Dangcheomul Cave and Yongcheon Cave - have been included in the UNESCO World Heritage List.
Manjang Cave runs 7,416 meters without stopping, and Gimnyeong Cave has long been called the Snake Cave for its meandering passage. About 80-100 meters apart from each other, the two lava tubes are presumed to have been created by one long lava stream, and been blocked in the middle by hardened lava, which separated it into two tubes. Bengdui Cave, a habitat for endemic species of spotty belly greenlings and spiders, is noted for its complicated, labyrinthine structure. While Dangcheomul Cave and Yongcheon Cave are indeed lava tubes, they feature a wide array of speleothems, or limestone cave formations, creating beautiful, otherworldly landscapes. The two lava tubes are quite different in size, the former being very small and the latter gigantic, but both offer spectacular views with a variety of speleothems generally found in limestone caves, such as soda straw, stalactite, stalagmite, column, cave coral, cave pearl, cave flower, curtain (bacon sheet), flowstone, rimstone, etc. In terms of size, shape, distribution and concentration, the speleothems in the two lava tubes are extremely rare examples unequaled by any other lava tubes in the world. It is presumed that these beautiful cave features were formed by rainwater mixed with carbonate sand on the ground, which infiltrated the caves and deposited calcium carbonate which was dissolved in the water.
The Geomunoreum Lava Tube System starts from the Geomunoreum volcano and advances toward the coast until it ends at Dangcheomul Cave. The main tube system branches out into three tributary tube systems: the first system, the largest in scale, runs 14.6 kilometers from the volcano; the second, parallel to the first tributary, is 13.2 kilometers long; and the third reaches out 8.2 kilometers to the northwest of the volcano. Combined end-on-end, the three tributary systems would be about 36 kilometers long.
|Parasitic cones distributed all over Jeju Island are diverse in shape. Most of them are cinder cones, formed by an eruption from the ground. The volcanic products spewed out from a volcano, fell to the ground and accumulated in the form of rock fragments with numerous dark or reddish holes, called cinders or scoria.|
Some other cones are composed of tuff, a type of rock consisting of consolidated volcanic ash formed by magma-water eruptions, which occur when molten magma comes into contact with sea water or ground water. Parasitic cones composed of tuff have two types: Firstly, tuff cones have elevated crater floors and steep sides, and secondly, tuff rings look like low hills with gentle slopes since they have a relatively small amount of tuff accumulated around a large crater.
|Seongsan Sunrise Peak (179 meters above sea level), protruding from the coastline of Jeju Island at its eastern tip, is a typical hydromagmatic volcano created between 120,000 and 50,000 years ago by an underwater eruption from a shallow seabed. As the name Ilchulbong (Sunrise Peak) implies, sunrise viewed from here is a truly magnificent sight.|
The crater, 570 meters in diameter and 90 meters deep, has steep slopes. The tuff cone has an impressive appearance reminiscent of a castle or a colossal crown, and its bowl-shaped crater has preserved its original form intact. The crater’s three sides except for the northwestern portion have been eroded by waves and reveal the inner layers of the volcano, serving as an important resource for geological studies on ancient volcanic activities.
Seongsan Sunrise Peak was originally an island, but the repeated deposit of sand and sediments has created a 500-meter-wide sand bar that runs for a 1.5-kilometer stretch to connect the peak to the main land of Jeju Island.
|Apart from the sites mentioned above, the volcanic land forms of Jeju Island include Mt. Songak, a monogenetic double volcano consisting of an outer tuff ring and an inner cinder cone, which shows how marine eruptions transform into land eruptions. Additionally, Mt. Sanbang is an example of a lava dome, built by viscous lava that piled up around the vent forming the mountain-like dome.|
Jeju Island is the only place in the world that displays such a wide variety of volcanic landforms in such a small area of land, serving as a virtual volcano museum.
In Jeju Island, various types of volcanic landforms, a wide range of climate conditions and the resulting ecology, and the island’s indigenous culture are unfolded in a relatively small and confined space in unique and beautiful harmony. This harmony, the result of a new order created from a concoction of natural, ecological and cultural features, is what makes Jeju Island so special. Specifically, the island’s natural environments are of great importance as scientific, cultural, industrial, and tourism resources, and its numerous parasitic cones and lava tubes have immense research value for studies on global volcanic activities.
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