Characteristics And Volcanic Processes Of Polygenetic Volcanoes In Seobjikoji Of Jeju Island, Korea

Seopjikoji, located at the eastern tip of Jeju Island, includes Seondol Scoria Cone, spatter/scoria in cone or mound form, aa and pahoehoe lava flows, and multiple dyke complexes. The spatter or scoria cones in the southeastern part of Seopjikoji (section A, B, C) were formed by a Strombolian eruption, the first volcanic activity in the Seopjikoji area, with nine dykes penetrating the spatter/scoria during the process. Two of the dykes in section A were feeder dykes that formed spatter/scoria cones. The remaining dykes in cylindrical shape penetrated the spatter/scoria cone, forming a circular, intrusive landform reminiscent of castle ramparts. The process was accompanied by the formation of spatter/scoria cones by feeder dykes in Section B, some of which reached the surface to form a lava flow. Section C was formed as erupted lava from the eruption dykes intruded into lava in the flowing process, causing irregular mixing of the intrusive complex and the lava along the exposed area. It is inferred that the remnants of the feeder dyke that formed Seondol Scoria Cone is Seondolbawi Rock in section D, the shape and distribution of components within which indicates a Strombolian eruption. A small-scale scoria cone was formed in the northern part of Seopjikoji (section E and F) following the volcanic activity that formed Seondol Scoria Cone, with lava flow overlying the slopes of Seondol Scoria Cone. Although Seopjikoji was thought to have been formed through a single monogenetic volcanic eruption, it should be characterized as a polygenetic volcano formed through a complicated process of Strombolian eruption. This is because numerous intrusions around the central body led to the formation of spatter/scoria cones and lava flows.