Mudeungsan Summit Colonnade(Chunwangbong, Jiwangbong and Inwangbong Peaks)
The columnar joints in three peaks of Mudeungsan form the Mudeungsan Summit Colonnade (1,187 m). They are the highest mountain tops in Gwangju-si and adjacent areas. The summit area, including the highest, Chunwangbong, Jiwangbong and Inwangbong Peaks stand as a ridge stretching from north-northwest to south-southeast. All of them comprise colonnades of columnar jointed Cretaceous welded tuff. The size of joint faces of the columnar joints is approximately 1.5~2 m and the column ‘diameter’ (that is, the greatest dimension of a cross section of a column) is measured at about 3~4 m. The cradle-shaped valley in the northern part of Chunwangbong Peak is the result of differential erosion of micrographic granite emplaced in joints in the solid Mudeungsan Tuff.
The columnar joints of Seoseokdae Colonnade are located about 400 m to the north-northwest from Ipseokdae Colonnade at 1,050 m above sea level, about 100 m higher than Ipseokdae Colonnade. Both rocks are designated Natural Monument No. 465. The Seoseokdae Colonnade is the main Mudeungsan columnar joint area covering about 300~400 m with over 200 stone pillars, appearing like a unfolded screen, about 30 m in height and 1~2 m face width. The upper parts of columnar joints are polygonally shaped as quadrangles, pentagons and hexagons. Seoseokdae Colonnade consists of Mudeungsan Tuff and the rocks were formed about 85 million years ago during the Cretaceous Period. The columnar joints have steep faces slightly tilted toward west.
The Ipseokdae Colonnade is located about 950 m above sea level to the southwest of Mudeungsan Summit Colonnade. The place is regarded as the main set of colonnades in the Mudeungsan region with symbolic values and important geological features. With its widely known magnificent scale and beauty, the Ipseokdae Colonnade is considered as a key tourism destination at Mudeungsan. The Ipseokdae colonnades developed in a north-northwest direction in the southwestern part of Mudeungsan. Overall, there are about 40 stone pillars with 20 m in width and 20 m in height. The joint surface width is about 0.6~1.2 m and column ‘diameter’ is around 1.5 m. It consists of Mudeungsan Tuff and intruded fine-grained granite. The columnar joints of Ipseokdae Colonnade comprise intra-caldera pyroclastic deposits. On the upper side of Ipseokdae Colonnade, small-scale tilted columnar joints, about 10 m tall, called Seungchunam developed.
The columnar joints in Gwangseokdae Colonnade have the largest individual columnar joints at Mudeungsan. The columns average about 30~40 m high with faces up to seven meters wide. These large-scale columnar joints are unparalleled anywhere in the world. There are about 100 gigantic columnar joints up to about 80 m tall around the Gyubongam Hermitage. Just as the other columnar joints, the Gwangseokdae Colonnade consists of Mudeungsan Tuff. Gwangseokdae Colonnade is located about 800 m away from the Mudeungsan Summit Colonnade to the southeast. Its altitude above sea level is approximately 950 m, lower by 200 m than the Seoseokdae Colonnade and 100 m than Ipseokdae Colonnade.
The Sinseondae Colonnade has well-developed pentagonal and hexagonal columnar joints as high as 5~6 m. The face widths are generally about 1~1.5 m. Some of the Sinseondae Peak’s columnar joints have multiple joints inside which indicate the weathering mechanisms of the columnar joints. Numerous secondary joints are developed both horizontally and vertically which has led to intense weathering. Examination of the ramp of Flame Grass Plain around the Sinseondae Peak, reveals that steep bluffs and very gentle pediments intersect each other on the planation surface. These slopes are deemed to have undergone planation due to the freezing and thawing under the influence of the past periglacial climates. For these reasons, the pediments are presumed to be periglacial cryoplanation surface.
Deoksan Block Stream
The Deoksan Block Stream lies on the western slope of ridge from Jungbong to Donghwa-si at 350~700 m above sea level. The length of block stream is about 600 m and the width is up to 250 m. The blocks forming Deoksan Talus were generated when the Mudeungsan Tuff columnar joints collapsed. About 130,000㎡ of blocks are clear lyexposedmakingitthelar gest blocks treamin the Mudeungsan area. The average talus slope is relatively steep at 25°~35°. Most of the slopes are gentle and the streams have a gentle concave cross section. The shapes of the talus prisms are triangular (30%), quadrangular (51%), pentagonal (10%) or hexagonal (9%). It is thought that the Deoksan Talus formed about 50,000 years ago.
Jigong Block Stream
The Jigong Block Stream is located around the Gyubongam Hermitage in the southern slope of Mudeungsan at 700~1,100 m above sea level. The total area is 42,000 km2. The talus on the upper side is at an altitude of 1,000~1,100 m and 150 m wide. The lower side talus is located to the west of the Gyubongam Hermitage. In the upper part of the talus, columnar joints are exposed. The Jigong Block Stream was supplied from the Gwangseokdae Colonnade columnar joints. The average slope is 20°~35°. The average block size is 0.5~1 m and the maximum size is observed around 4~5 m. The blocks are predominantly 4~6-sided.
Wind Holes(air vents)
Over 23 groups of air vents (the so-called Wind Holes) were found (as of 2013) in the Bukbong Peak (Nuebong Peak) region in the north between 900~1000 m above sea level. Inside the Wind Holes, the temperature stays about 7~18℃ in winter even when the temperature outside is below zero: humidity remains high even during winter allowing green mosses to grow in the higher temperatures. The lower the temperature moves below zero, the more the warmer ‘steam’ is released. In the summer, dense cold air drains from the vents. Many more vents are reported on the Gyubong ridge but no scientific measurements have yet to be made.
Jangbuljae Cryoplanation Surface
Jangbuljae is a cryoplanation surface on Mudeungsan where steep bluffs and pediments alternate within the planation surface. Such slopes underwent planation due to freezing and thawing under the influence of former periglacial climates. Jangbuljae boasts a magnificent view with its large-scale Flame Grass meadows. The formation of Jangbuljae was dated at 50~60 ka using 36Cl from the inside of quartz particles. Jangbuljae slopes are almost flat orgently angled. Solifluction took place in periglacial conditions to move soil and rock blocks downslope. As solifluction filled in uneven surfaces, flat pediments were formed. Such a shift is because strong freezing and thawing activity generated ice within the columnar joints formed in exposed rocks above flat ancient surfaces at altitudes of 900~1,000 m. Since such movement does not take place under the present conditions, the place is regarded as a periglacial cryoplanation surface dated to the Last Glacial Maximum.
Baekma (White Horse) Ridge
The approximately 2.5 km long Baekma Ridge is located around Jangbuljae-Ahnyangsan at the altitudes of 800~900 m. It forms a slope with a south-southwest aspect. On the Baekma Ridge, the high density of rock block clusters is easily observable on aerial photographs. This ridge was formed during the last cold climate period through periglacial processes. The name, Baekma Ridge, derives from the smooth shape which looks like a horse’s back. The Flame Grasses are said to resemble a horse’s mane.
Saeinbong Peak is located at the altitude of 608 m above sea level and is a wall of Dogok Rhyolite. It looks as a continual vertical cliff if looked at from the south. On its flanks there are well-developed vertical joints. The summit area has horizontal joints and gnammas of 20 cm in diameter and 10 cm in depth. Gnammas are circular micro-topographic features like a shallow flat-floored bowl created by chemical weathering. They are sometimes referred to as solution pans. Bluffs in this area are mostly developed in rhyolite rocks and deemed to have been created by vertical joint development and continued partial collapse of bedrock.
The Uisangbong Peak (about 550 m above sea level) is late-Cretaceous micrographic granite. Two types of weathering topography occur, gnammas and tors. On its upper side, granite exposed but the mountain slope is covered with boulder layers. The gnammas at Uisangbong Peak have a maximum major axis length of 176 cm and minimum minor axis length of 8 cm. Of the gnammas observable in this area, those on Bimajok Boulder and Byeoru Boulder are most famous. The Haetalam and Byeongpung Sinseondae Rocks are tors (boulders) in the Uisangbong Peak area. They provide scenic vistas.
(It is prohibited strictly to enter the National Park Non Specific Trail to preserve the nature.)
Mudeungsan Gwnagju Granite
Mudeungsan Gwangju Granite is a well-developed Jurassic granite outcrop located behind the Chosun University. It is composed of Triassic-Jurassic amphibole-biotite granodiorite, and Jurassic quartz diorite as well as Cretaceous quartz porphyry and micrographic granite. Triassic granites include biotite granite and granodiorite. The two types are collectively called Gwangju Granite. This site has faults and slickensides demonstrating its geological history. The outcrop is easily accessible from downtown.
The Simujigi Waterfall is located under the Gyubongam Hermitage. The waterfall is named Simujigi (meaning three rainbows) as it has rainbows under sunshine after rain (Figure 25). The Simujigi Waterfall is 72 m long and divided into three sections of the upper part (35 m), mid part (15 m), and lower part (32 m). The upper parts are at a 45° angle; lower part, about 7 m, falls vertically. The bedrock is dacite tuff and has a sedimentary structure established when volcanic fragmented material was deposited. The rock has mainly plagioclase phenocrysts in a black background. The main mineral components are plagioclase, clinopyroxenes, orthopyroxene, quartz and opaque minerals. Polarizing microscope investigation shows it to be crystalline tuff.
Andesite lava in the Mudeungsan Jeungsimsa Valley is one of several lava layers created through a number of rounds of eruptions. Fresh parts of it range from dark green to dark grey; the weathered faces have brown through reddish-brown colors. The Jeungsimsa Valley Andesite consists of andesite tuff, andesite lava and other intruded rocks. Jangdong Tuff and Jeokbyeok Red Cliff Tuff beds are separated unconformably and have micrographic granite intrusions. The andesitic lava is mostly seen in the northwest part of Hwasun-eup, Hwasun-gun and around Dongbokho Lake. But the type locality is the Mudeungsan area.
Seoyu-ri Dinosaur Fossil Site
The Jangdong Tuff is in the sedimentary basin of Neungju Basin in Seoyu-ri, Hwasun-gun, Jeollanam-do. It has many late-Cretaceous dinosaur footprints. The Seoyu-ri dinosaur fossil site is a geologically important place and has six sedimentary zones where about 1,500 dinosaur footprints and 73 trackways are observable. Approximately 88% of these footprints belong to carnivorous deinonychosaurs. Small deinonychosaur footprints are especially abundant. These deinonychosaur trackways have very distinctive features and are quite long (averaging 45 m). Ornithopod and sauropod footprints were also found but in small numbers. Deinonychosaur footprints are categorized into several forms and show similar shapes to those of Megnoavipus, Ornithomimipus and Xiangxipus. To estimate the sizes of dinosaurs at Seoyu-ri, the height up to their pelvis was estimated based upon the footprint lengths. As a result, the small dinosaurs were found to be 1.0~2.0 m; and large dinosaurs, 2.0~2.6 m. Based on the Alexander (1976) formula, the average dinosaur moving speed was calculated. Small dinosaurs were found to move at the rate of 3.3~20.5 km/h; and large dinosaurs, 3.7~13.9 km/h. Therefore, small dinosaurs are estimated to walk fast or run whereas large dinosaurs walked relatively slower (Huh Min, et al, 2001; Huh Min, et al, 2003; Hwang Gu-geun, et al., 2006).
Jeokbyeok Red Cliffs
The Ieseo-myeon area in Hwasun-gun, where the 23 km long Jeokbyeok Red Cliffs are located, belongs to the Neungju Basin that was created in the Cretaceous. Geologically, the region has the clastic sedimentary rocks and igneous rocks such as Wolsan Tuff, Jangdong Tuff, Mudeungsan Tuff and andesite. Of these, the sedimentary layers of the Jeokbyeok Red Cliff is partly Jeokbyeok Red Cliff Tuff and partly Jangdong Tuff. The rock is dominated by fine-grained tuff and sandstone, tuffaceous sandstone, siltstone, shale and conglomerate layers. In general, outcrops with tuff have well-developed stratifications and beddings. The conglomerate layer there is composed of tuff, porphyry, granite gneiss and meta-sedimentary rocks (Goh Yeong-gu, et al., 1995).
Hwasun Dolmen Jangdong Tuff
The dolmen site in Hwasun-gun has as many as five quarries where the necessary cover stones were removed from tuff outcrops in the Cretaceous Jangdong Tuff beds for dolmen construction. Most other dolmens outside the quarries are comprised of rocks fallen from the Jangdong Tuff by weathering processes. The Hwasun Dolmen Site is important both geologically and historically. The Hwasun Dolmen Site is South Korean Historic Site No. 410 showing the south-type dolmens: the major tomb style in the Bronze Age. The site has a high density of large-scale dolmens which are globally significant. In addition, a polished stone dagger was discovered along with many diverse relics. For its significance, the place was inscribed as the UNESCO World Heritage in 2000 as part of the serial Gochang, Hwasun and Ganghwa Dolmen World Heritage property. Daesin-ri and Hyosan-ri in Hwasun have 319 sets and 277 sets of dolmens, respectively, to make a total of 596. Dozens of the dolmens weigh over 100 tons including the Pingmae-bawi Boulder which weighs over 200 tons, the largest dolmen in the world. The place, overall, well displays the Cretaceous tuff outcrops and shows that these outcrops were used as quarries for the dolmen material. It is deemed a highly valued geological and historic place.
Unjusa Stratified Tuff
The region around the Hwasun Unjusa Temple is composed of Jandong Tuff. These outcrops are lapilli tuff with well-developed stratifications. Given the volcanic fragmental material and bedding planes, the place was created around a crater and records volcanic eruptions and deposition in the distinct bedding planes. The temple has tuff cliff outcrops several meters high and on their faces multiple big and small Buddha statues have been placed to further enhance the mysterious atmosphere. The Unjusa Temple Buddha statues, pagodas and other stone works were created in the Goryeo Period. Without exception they are all made of tuff from the site.
Chunghyodong Clay Mineral Site
The Chunghyodong Clay Mineral Site is Historic Site No. 141 and is located on the northern ridge of Mudeungsan. The site is one of the major kiln sites with actual relics showing the transformation process and features of buncheong porcelain production in the 15th century. There area total off our kilns and potsherd sedimentary layers with clear relative order of production. The layers were discovered and investigated by the National Gwangju Museumin 1991. The place shows kiln developmental status in each period through the stratum in its 3.5 m-deep Chunghyodong Clay mineral site. Based on the clay minerals used to make white porcelain, the relationship between the past folk culture and geological features have been identified in this place.