• Journal of the Korean Geographical Society
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• v.41 no.4 s.115
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• pp.391-403
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• 2006

The Hanon volcano located in the southern pan of Cheju Island, Korea has a wetland in its crater being used as a farmland. Previous researchers presumed this wetland was a maar lake in the past. Based on the seismic refraction method, the wetland sediment layer was estimated between 5 to 14 m deep, which is mostly in accordance with previous researches. However, this shows only the depths at some sites, not representing the whole spatial distribution. This study is an attempt to reconstruct the volcanic lake in Hanon crater by applying the spatial statistical techniques based on the depth information from the seismic survey and known data. The procedure of reconstruction is as follows: First, the depth information from the seismic survey and known data were collected and it was interpolated by IDW and Ordinary Kriging method. Next, with the interpolation map and the present DEM the paleo DEM was constructed. Finally, using the paleo lake level on core data, the boundary of volcanic lake was extracted from the paleo DEM. The reconstructed lake resembles a half-moon in the north of the central scoria cone. It is estimated that the lake was 5 m deep on average and 13 m deep at the deepest point. Although there are slight differences according to the interpolation techniques, it is calculated that the area of the lake was between 184,000 and $190000m^2,$ and its volume approximately $869,760m^3$. Because of the continuous deposition processes after the crater formation, the reconstructed volcanic lake would not indicate an actual lake at a specific time. Nevertheless, it offers a significant clue regarding the inner morphology and evolution of the crater.

• Korean Journal of Environmental Biology
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• v.36 no.4
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• pp.439-455
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• 2018

Hanon made in the largest maar crater in Korea, is the only paddy field ecosystem in Jeju Island that has been conducting rice farming, for the past 500 years. Flora surveys were conducted eight times, 2015-2018, to understand floristic characteristics and a restoration plan of the study area. As a result, vascular plants of Hanon paddy fields were listed 225 taxa that consist of 55 families, 151 genera, 194 species, 1 subspecies, 25 varieties, and 4 forms. The taxonomic group including the most species, was Gramineae (36 taxa). The next families were Compositae (29 taxa), Cyperaceae (20), Leguminosae (13), and Polygonaceae (11). Biological type of the Hanon was $Th-R_5-D_4-t$ type. The rare plants revealed 3 taxa; Ottelia alismoides(L.) Pers., Acorus calamus L., Pseudoraphis ukishiba Ohwi. Endemic plant revealed 1 taxon; Saururus chinensis(Lour.) Baill. Forty three taxa were naturalized plants composed of 15 families, 24 genera, 41 species, and 2 varieties. The urbanization index and naturalized index were 13.3% and 16.9%, respectively. The Hanon has high plant diversity, including endemic plant and rare plants, and is the only rice paddy in Jeju Island. So, the Hanon has sufficient values in ecological and socio-cultural aspects, so it should be maintained continuously in the future.