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Take a unique 1-kilometer subterranean strollPart of Jeju’s UNESCO ‘triple crown,’ Manjang Cave has science and beauty in equal measure
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승인 2011.03.02  07:26:51
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▲ Map courtesy and Jeju Special Self-Governing Province

At the beginning of October, 2010, the Global Geoparks Network announced that Jeju Island would be made its 20th member, making it Korea’s only province to be assigned Geopark status. In the categories of geology, archaeology, biology and cultural interest, nine sites on the island were inspected and later certified. This article briefly introduces the third site: Manjang Cave— Ed.

Manjang Cave
- A lava tube formed from multiple volcanic events occurring over the last 120,000 to 300,000 years
- 7.4 kilometers-long, max. 30 meters-high and max. 23 meters-wide
- One of more than 120 lava tubes scattered throughout Jeju Island
- Discovered in 1946 by noted Jeju scientist Boo Jong Hue
- A UNESCO-mandated environmental designation: Geopark status as certified by the Global Geoparks Network (2010)
- A UNESCO World Natural Heritage site as part of Geomun Oreum lava tubes (2007)
- Korean Natural Monument No. 98 (1970)
- Of strong scientific interest, considered a “volcano museum”
- Of the three entrances, the public has access only to entrance No. 2 and can experience just 1 kilometer of the total
- In 2009, 572,854 visitors (92,307 non-Koreans)
- In 2010, 686,696 visitors (103,390 non-Koreans)

How it formed
According to the 2006 nomination document submitted during Jeju’s UNESCO World Natural Heritage site bid, the Geomun Oreum system is a series of lava tubes formed by large amounts of basaltic lava flowing from a live volcano about 300,000 years ago. The lava flowed down the slope of Mt. Halla in a north-northeast direction. Manjang was formed approximately 200,000 years ago. Worldwide, lava tubes tend to be younger than this.

The geology
Manjanggul Lava Tube was first explored by Boo Jong Hue in August of 1946, and a detailed scientific study was carried out in February 1966. In total, Manjang’s lower — and main — tube is 5,296 meters-long, and the upper level is 2,120 meters-long.

The cave boasts a wide range of geological structures including lava stalactites and stalagmites, a lava column, flowstone, cave coral, lava rafts, lava bridges, shelves, ropy lava, and grooved lava striations. These have been subject to very little degradation from human activities.

According to the government-run Web site for the Geomun Oreum Natural Heritage site, the cave is mostly closed to the public to protect “cave organisms” and structures like stalactites and stalagmites from damage. “An influx of soil, dust and harmful bacteria may change the interior environment of lava tube, and may seriously destroy the cave ecosystem,” it adds.

The public space has been open since April 1, 1967, and included a number of alterations to the cave such as wall and roof reinforcements, lighting, walkways, etc. However, the Cultural Heritage Administration says there has been minimal impact on the overall condition of the cave, making Manjang and the other Geomun Oreum lava tubes a valuable resource “for preserved lava micro-topography and speleothems [cave formations].”

There are at least 62 types of animals and insects that live in Manjang, particularly the Jeju cave-spider (Nesticella quelpartensis) and an estimated 30,000 long-winged bats (Miniopterus schreibersii fuliginosus), “forming the largest colony of bats confirmed to be living in Korea so far known.”

Scientific research
“There was quite a lot of progress,” said Dr. Woo Kyung Sik. “One geologist was given a project to trace the lava flow system to help us understand the source of Manjang Cave’s lava. And there was one gentleman who got a Ph.D degree by doing research on Manjang a few years ago.”

Dr. Woo, a professor in the Department of Geology at Kangwon National University and director of the Cave Research Institute of Korea, told The Jeju Weekly that there is still a lot of scientific work to be done in the undeveloped parts of the cave system. “Manjang Cave shows many important morphological features about the lava flows during the formation of this cave.”

However, he thinks that now that the Jeju government has its “triple crown” with the Geopark designation and is moving on to its next project, becoming one of the New7Wonders of Nature, “the Jeju government is not really into [promoting education at the site].”

A quick look at the official Jeju Geopark Web site ( seems to support Dr. Woo’s observation. As of this writing, it has not been updated since Jeju became part of the Geopark network last October.

But Dr. Ahn Ung San, a geologist who worked on the provincial Geopark campaign and who received his doctorate studying the formation of Manjang Cave, told The Weekly that the Geopark sites, World Natural Heritage sites and the Biosphere Reserve are now managed by one Jeju provincial office, the World Heritage Management Organization, which “provides links among various organizations and institutions in Jeju.”

He said that contrary to common belief, it takes a lot more than a few geologists to run a Geopark site. It is too costly for the provincial government to run them all, and Geopark sites “need various forms of manpower and groups, including people who educate ... publicize ... and encourage locals to participate.”

He also drew a distinction between the goals of the World Natural Heritage sites and Geopark sites.

“While the priority of the Geoparks is to contribute to the local economy [with tourism and education], the priority of World Heritages is to preserve and hand down these precious things to our descendants,” he wrote in an email. “Germany and China introduced Geoparks into the places registered as World Heritages and utilized them as tourist attractions ... making these sites recognized by the public easily.”

Dr. Woo said that when it comes to educating the public, there are signboards at Manjang Cave, “but the problem is that most visitors cannot understand or do not intend to read them.” He strongly recommended the guided tour system to help the public learn about and understand the science of this remarkable site.

[To test this, I spoke with the guides and followed a senior guide through the tour with a group of tourists. See the Editor’s Column on page 19 for more.]

According to Gang Oh Young, a World Heritage Management Organization volunteer with 4 years experience, the 2010 Geoparks designation isn’t well known enough domestically to have influenced the number of tourists to Manjang Cave. Other guides agreed: the consensus was that there had been no increase in numbers since the October announcement.

But back in 2007, when the Geomun Oreum lava tube system (and Manjang Cave), Seongsan Sunrise Peak, and Mt. Halla became UNESCO World Natural Heritage sites, the guides recalled a large increase in visitors both from here and abroad.

Dr. Ahn says taking only visitor numbers into account is looking at Geoparks “in a narrow sense.”

“The number of people visiting Manjang Cave has probably not increased, but people would think about Geoparks and geo-sightseeing when they visit,” he said. “For instance, Suwolbong [tuff ring], located in the west of Jeju, was only visited by a few scholars before it was certified as a Geopark. Today it has become a famous attraction that is visited by students on school trips and many other groups on field investigations.”

“Going back to the example of Manjang Cave, I believe that the non-increase of number of visitors is only a quantitative matter, while the increase of visitors who have an educational purpose is a qualitative one. It is not the quantitative increase that Jeju has pursued, but I definitely think that the qualitative improvement of Jeju tourism is being made.”

For international visitors coming to Manjang Cave, however, there remains a glaring lack of international interpretation services and signage.

“This is only a Korean Nature Heritage site, not a World Natural Heritage site,” Gang said with some bemusement regarding the lack of bilingual guides among the 42 volunteers on call at Manjang. Gang said that despite his requests to the Jeju government to add Japanese, Chinese and English speakers to the roster, two reasons were clearly preventing action.

“Firstly, foreigners visiting here do not complain, so the government doesn’t realize there is a need,” he said. When Korean visitors complained that the cave lighting was insufficient, the government put extra money into a 5-month-long upgrade that finished in September.

Secondly, he said, the Korean volunteer guides — who work twice a week — receive a 33,000 won a day stipend. This, Gang thinks, dissuades people who have multilingual skills and who could make much more doing the same job elsewhere.

(Translation by Koh Yu Kyung)
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