전라남도 여수·순천·구례지역 안산암 주상절리의 형태

Abstract

Columnar joints are formed by volcanic activity and are formed during the cooling of high temperature materials. In Korea, columnar joints are distributed in over 68 regions. The columnar joints developed in andesitic rocks analyzed in this study are representative of columnar joints located in Mudeoungsan National Park. This study investigates the formation process of columnar joints distributed in andesitic rocks in eastern Jeollanam-do. And, this study attempts to analyze the factors affecting the formation of colmnar joints by comparison with columnar joints presented in previous studies. The columnar joints in the study area are distributed in Geumjeong-ri, Muncheok-myeon in Gurye-gun, Haeryong-myeon in Suncheon-si, as well as Gubong-san and Hyangiram in Yeosu-si. Major elemental analysis of rocks composing columnar joints showed SiO2 contents of 55.02wt%~60.90wt%. As shown in TAS, all the rocks in the study area correspond to the andesite area, and most of them are sub-alkali series. A columnar joints development in Gurye area was formed as andesite intrusion(sill) through the formation of Togeum rhyolitic tuff. The columnar joints in the Gurye area have columnar joints of pentagonal shape with an average length of polygon side 30cm and angle of between adjacent edges of 111°~120°. The columnar joints developed in the Suncheon area have a constant direction and size and are formed by volcanic activity once. The columnar joints in the Suncheon area are of hexagonal shape with an average length of polygon side 30cm and angle of between adjacent edges of 101°~110°. Columnar joints developed in the Gubong-san of Yeosu are rarely typical outcrops but are observed near the road to the summit. The columnar joints in the Gubong-san of Yeosu area are of hexagonal shape with an average length of polygon side 31~40cm and angle of between adjacent edges of 111°~130°. Columnar joints developed in the Hyangiram area of Yeosu show the formation of small columnar joints during the cooling process after the formation of large columnar joints. The columnar joints in the Hyangiram area of Yeosu have columnar joints of hexagonal shape with an average length of polygon side 31~50cm and angle of between adjacent edges of 101°~130°. When columnar joints of the study area were compared with columnar joints of Jasatgae in Jeju-do composed of basalt and dacite, and columnar joints of dacite, columnar joints were formed rather than affected by chemical composition, determining the shape.