Jejudo is a volcanic island which occupies 1,849 square kilometers of the Yellow Sea south of the Korean peninsula. Its genesis began 1.8 million years ago after seabed volcanic activity eventually gave birth to a towering Mt. Hallasan, divinely rising to 1,950 meters over the island. Its dominance is reflected in the local saying: “Jeju is Halla, and Halla is Jeju.”
The shield volcano, rooted 100-meter-deep on Yellow Sea continental shelf, is geolmlogically young, with parts of the Seogwipo Formation, although the island’s oldest rock, forming as recently as 400,000 years ago. A proto-Jeju Island was thus born as continual hydrovolcanic activity and volcaniclastic sedimentationspectacularly burst through Pleistocene seas over hundreds of thousands of years.
As land formed, many of the 368 satellite volcanic cones (“oreum” in the local dialect), now picturesquely dotting the island, spat out searing lava effusions which wended across and smothered virgin land from 800,000 to as recently as 5,000 years ago. By the last glacial maximum, 18,000 years ago, Jeju’s coastal regions were aflame as hydrovolcanic eruptions Continued on page T2 Continued from page T1 pockmarked the shoreline.
The fresh morphology of several tuff rings and tuff cones such as Suwolbong, Songaksan, Ilchulbong, and Udo — known as phreatomagmatic volcanoes — is a reminder of this turbulent time. Older examples include Dangsanbong, Dansan, and Yongmeori, stoically remaining above the more recent 50 to 60-meter-thick lava plateau across the southwest.
Many of these eruptions led to lava flows of such force that valleys were carved from Jeju’s basalt. Some of these low-viscosity molten rivers cooled and developed crusts, thickening and directing the lava channel below. Eventually conduits were formed through which molten lava passed, and further lava flows were directed subterraneanly by cooling surface lava, forming additional tunnels.
In this way, Jeju’s oreum gave birth to 120 lava tubes, boasting secondary carbonate mineralization and limestone-cave type speleothems, or cave mineral deposits. Geologists regard these lava tubes as exceedingly rare, if not unique, and the most famous is the Geomun Oreum Lava Tube System, formed from basaltic lava flows erupting from the 456.6-meter satellite cone in northeast Jeju.
While all of Jeju’s caves are invaluable scientifically, the Geomun Oreum system has received most recognition and is inscribed on the UNESCO World Natural Heritage list (2007), while Manjanggul Cave, Geomun’s progeny, is one of Jeju’s Global Geopark sites.
▲ Pāhoehoe Lava cooling and hardening. Photo courtesy Brocken Inaglory
In granting Geomun Oreum lava tubes World Natural Heritage status, UNESCO stated:
“The Geomun Oreum lava tube system, which is regarded as the finest such cave system in the world, has an outstanding visual impact even for those experienced with such phenomena. It displays the unique spectacle of multi-coloured carbonate decorations adorning the roofs and floors, and dark-coloured lava walls, partially covered by a mural of carbonate deposits.”
Looking a bit closer at Geomun Oreum is informative in understanding lava tube geology. As the lava flowed north-northeast to the coast, numerous lava tubes formed including Manjanggul, Gimnyeonggul, Yongcheondonggul and Dangcheomuldonggul. (“Gul” means cave in Korean.)
The basaltic lava burst forth 300,000 and 200,000 years ago, and the tube has two levels: a lower (main) level of 5,296 meters in length, and an upper (tributary) level of 2,120 meters in length. Meandering for 7,416 meters toward the coast with a breadth of 23 meters, it ranks in the top 15 longest lava tubes in the world.
Inside are many of the features found in lava tubes, including: lava stalactites and stalagmites, lava columns, lava flowstones, lava helictites, lava blisters, cave corals, benches, lava raft, lava bridges, lava shelves, grooved lava striations and ropy lava.
As the lava flowed from Geomun Oreum, it also formed a plateau above ground, and the land harbors Jeju’s remaining Gotjawal, or rocky forests rooted on a thin basalt shelf, as well as thickets, ponds and farmland. Of all the caves in this area of Jeju, only Bengdwigul was not borne of this lava flow.
The tunnels also provide rich habitat for animal life. A total of 30,000 long-winged bats (Miniopterus schreibersii fuliginosus), the largest colony yet found in Korea, occupy the lava tubes, and their accumulated excrement, “guano,” is essential to the health of the ecosystem of 38 species of fauna, including the Jeju cave-spider (Nesticella quelpartensis). At Yongcheongul, a new species of fish, Luciogobius Pallidus, has been identified, pale and Gollum-like, although lacking eyes.
While the pasty fish, unable to even see flickering shadows on the cave wall, can be forgiven for remaining in the dark, we have no such excuse. Jeju’s geological heritage is there for all with eyes to see, so read on for a comprehensive guide to Jeju’s lava tunnels and caves.
Sources: Jeju World Natural Heritage; Jeju Island Global Geopark
▲ Photo courtesy Kang Dong-cheol
Manjanggul Cave is a Global Geopark site and one of the finest lava tunnels in the world. Formed from the lava flows from Geomun Oreum, the cave includes a variety of interesting structures including 70 c.m. lava stalagmites and stalagtites, lava tube tunnels and lava stone pillars. Although 13,422 meters long, only 1 k.m. is open to tourists and whether hot or cold outside, the tunnel temperature remains at 11~21. Keep your eye out for the bat colony here, or the Stone Turtle, a basalt feature shaped like Jeju-do Island.
182, Manjanggul-gil, Gujwa-eup, Jeju-si
Hours: 9 a.m. to 5 p.m.
How much: Adult: 2,000 won / Youths(over 7 under 24): 1,000 won
Jeju Intercity Bus Terminal ▶ #700 ▶ Manjanggul entrance ▶ walk about 25mins ->Manjang Cave.[1h 30mins] (a ballpark figure from the entrance to Manjanggul is 4,000 won)
▲ Photo courtesy Jeju Special Self-Governing Province
Ssangyonggul Cave, approximately 400 meters in length, 6 meters in width, and 3 meters in height, is thought to have been created by lava that erupted from Mt. Hallasan some 2 million years ago. A designated Natural Monument it stands alongside Hwanggeumgul, Socheongul, and Manjanggul caves as representative of Jeju’s lava tunnel heritage.
The cave’s branches are said to look like the trail of two dragons (“Ssangyong”) and geologists believe it was once part of the same tunnel as nearby Hyeopjaegul Cave. A unique feature of the cave is its limestone cave features, formed from sedementary rock. The cave is located in a stratum of seashells and sand and lime covers the cave walls in eye-catching swirls and streaks.
Note: Both Ssangyonggul and Hyeopjaegul caves are in Hallim Park. See right for visitor information.
▲ Photo courtesy Eric Hevesy
Nearby Ssangyonggul, yet measuring just 200 meters in length, 10 meters in width and 5 meters in height, Hyeopjaegul Cave is also a Natural Monument. The cave is situated within Hallim Park, one of Jeju’s most popular, and earliest, tourist attractions.
Like Ssangyong, it is thought to have been created from eruptions of Mt. Hallasan some 2 million years ago. Again, we see the same rare limestone and basalt features as Ssangyonggul, while lime also picturesquely streaks the walls. Of particular note here are the stalactite columns which formed from the meeting of stalactites and stalagmites.
Hallim Park, 300, Hallim-ro, Hallim-eup, Jeju-si
Hours: 8:30 a.m. to 7:30 p.m.
Adults: 10,000 won / Middle and high school youths: 7,000 won / Children (above 36 months): 6,000 won
Jeju Intercity Bus Terminal ▶ #700 [westbound] ▶Hallim Park [1 hour]
▲ Photo courtesy Ilchulland
Some etymologists suggest that the name of Micheongul Cave means the “cave home to a thousand kinds of beauty.” Even if this is slightly hyperbolic, Micheongul is extremely important academically and culturally. The area around the cave has plenty of fresh air and water, as well as green fields and oreum. Along its 1.7 k.m. length, 365 meters is open to the public and the cave walls are said to shine in multicolors with rich minerals. You can also find a wish-granting water pool.
Micheongul Cave, 4150-30, Jungsangandong-ro, Seongsan-eup, Seogwipo-si
Hours: 8:30 a.m. to 6 p.m. (Admission until an hour before sunset.)
Adults: 9,000 won / Middle and high school youths: 6,000 won / Children above 36 months: 5,000 won
Jeju Intercity Bus Terminal ▶#502 ▶ Namseogwang Village ▶#720 ▶Samdal 1-ri ->Walk to Ilchul Land [2 hours]
Dongan Gyeonggul Cave
▲ Photo courtesy Jeju Special
Dongan Gyeong-gul is charmingly dubbed, “whale nostril cave” because of its large nostril-like shape. This cave sits at the edge of a black sand beach on Udo’s southeast corner. One must cross the beach, climb into a small cave lined with many piles of neatly stacked rocks which are used to make wishes, then climb through a narrow opening and onto some boulders, which finally lead into a mysterious cavernous otherworld. Since 1997 a music festival has been held at the cave every autumn due to its natural acoustics.
Dongan Gyeonggul Cave, Udo-myeon, Jeju-si
Hours: 24 hours
How much: Free entry
Jeju Intercity Bus Terminal ▶#710 ▶ Seongsan harbor [2 hours] ▶ Ferry to Udo [every 30 mins / takes 20 mins]
Contact: 064-783-0004(Udo myeon)
Daheeyeon Garden (see here for a guide)
▲ Photo courtesy Agne Latinyte
Daheeyeon Garden (formerly known as Gyeongdeokwon) is one of the major tea farms on Jeju Island and boasts ponds, bridges, indigenous trees and flowers. There are also two cafes — Eve Hall and Green Luce Garden — that are constructed within caves. The two cafes serve naturally fermented green tea bread, cookies, green tea latte and green tea juice in the cool underground lair of Jeju’s Gotjawal habitat.
115-1, Seongyo-ro, Jocheon-eup, Jeju-si
Hours: 9 a.m. to 7 p.m.
How much: Admission is free if you are purchasing food or beverages. For others:
Adults 5,000 won / Middle and high school students 3,000 won / under 10s free
Transport: Jeju Intercity Bus Terminal ▶ #700 ▶ Hamdeok-ri ▶#900 ▶Daheeyeon [1 hours 20 mins]
Jeju World Natural Heritage Center
▲ Photo courtesy Jeju Special
This center at Geomun Oreum was founded to commemorate Korea's first World Natural Heritage Site and provides a multimedia tour of Jeju’s geological history. In the Permanent Exhibition Hall there are models and images of Mt. Halla, the Geomun Oreum lava tube system, and Seongsan Ilchulbong tuff cone. In the 4D video room there is an engaging and informative film introducing Jeju’s natural history and culture.
Jeju World Natural Heritage Center, 569-36, Seongyo-ro, Jocheon-eup, Jeju-si
Hours: 9 a.m.-6 p.m. 365 days a year
Adults (individual 3,000 won group 2,400 won) Youths/Soldiers (individual 2,000 won group 1,600won), Children (individual 2,000 won group 1,600won) Disabled/Senior Citizens Free
Jeju Intercity Bus Terminal ▶#720 (toward Pyoseon) ▶Geomun Oreum [1 hour] ▶ walk [10 mins]
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