Gumunso

Gumunso () is a swamp in Dongjeom-dong, Taebaek, Gangwon Province, South Korea which features a river that pierces through a mountain, the only one of its kind in Korea. It is also known for its geological value, as its stratigraphic continuity is well-preserved. It names the surrounding village and neighborhood ( dong).

With an area of 685,109 m², the "Ordovician Deposits and Topography of Stream Erosion of Gumunso" is a part of Gangwon Paleozoic National Geopark and is the 417th Natural Monument of South Korea. In Gumunso, the Jigunsan and Makgol Formation (with the former unconformably overlying the latter) from the Lower Paleozoic Ordovician period (~440 to 500 million years ago) can be found. The two streams Cheoramcheon (철암천) and Hwangjicheon (황지천) meet in Gumunso, and could be considered the start of the Nakdong River.

Name

The name Gumunso is a Hanja version of the name Gumuso (), where " 구무" is a Middle Korean term for "hole". A purely native-Korean name is Tturunae (, compare 뚫다). Historical documents such as the geological survey included in the ''Veritable Records of Sejong'' () and Daedongyeojido records the name as Cheoncheon (). The cave itself is called "자개문" (子開門).

Formation and history

Formation

During the Ordovician era, the Taebaek region was originally underseas, with organisms like coral depositing limestone that would form today's Gumunso. Some time after, the sea became isolated, and became extreme salty as it dried up. Because of this, rectangular imprints left by salt crystals are present on the rocks. Additionally, around Gumunso, sedimentary rocks can be found which were deposited during the Paleozoic Era, approximately 520 to 460 million years ago. Geological structures like trilobite fossils and stromatolites can be seen. Further upstream is the Jigunsan Formation, which contains abundant fossils. In 2000, calathid fossils was discovered in the Gumunso-adjacent Makgol Formation, the first to be found in the Korean peninsula.

From 30000 to 70000 years ago, Hwangjicheon used to have an extremely sharp rightward bend where today's Gumunso would be, eroding the limestone. The stream formed an Ω-shaped (or horseshoe-shaped) meander and deposited well-rounded gravel with interbedded sand. Dating shows that this sedimentary layer lasted for the aforementioned years. From 30000 to 10000 years ago, 40000 years of erosion has opened a small channel in through the limestone in Gumunso, reducing the flow to the meander. This was reflected by smaller pebbles being present in the deposits of that time. Around 30000 years ago, the hole was fully formed, and the weakened meander disappeared completely, becoming a swamp. Today, this abandoned channel consists of farmlands and is called 사군다리.

Modern

'' Sinjŭng Tongguk yŏji sŭngnam'', a 1530 geography book, notes: "The Hwangjicheon is located 110 '' ri'' west of Samcheok-bu. Its waters flow south for about 30 ''ri'', piercing through a small mountain and continuing southward—called Cheoncheon". During the Japanese colonial period, the Japanese dug a tunnel next to Gumunso in 1937, aiming to build a road to transport coal and workers. On 2000 April 28, the "Ordovician Deposits and Topography of Stream Erosion of Gumunso" was designated as the 417th Natural Monument of South Korea. In September 1998, the Taebaek city reduced the number of neighborhoods from 16 to 8, and merged Dongjeom-dong and a part of Jangseong-dong (장성동) together. The resulting dong was named Gumunso-dong.

Folklore

There is a lot of folkloric myths surrounding Gumunso. One creation myth correctly identifies 사군다리 as an abandoned channel: the story involves a large tree that has been uprooted in a flood, explaining how it crashed into the mountain and created the tunnel. Another legend involves the legendary king Yu the Great accidentally creating the tunnel with his sword while learning water control. One tells the story of the White Dragon blasting the tunnel while battling the Blue Dragon for the control over the Nakdong river. Historical prophetic work Jeonggamnok claims that going through the stone tunnel will during midnight will bring one to a paradise free from hunger.

The Dragon King is also featured in a lot of folklore.

See also

* Meander cutoff
* Geology of South Korea
:* Geology of Taebaek

References

Journal citations

*
*

External links

Video showcase

{{Coord, 37.0930, 129.0422, type:landmark_region:KR, display=title

Swamps of Asia
Natural Monuments of South Korea
Taebaek
Nakdong River