Korea Tour : Jeju Volcanic Island and Lava Tubes (3)
Geomunoreum Lava Tube System: An Unimaginable Mystery
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.
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