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タイトル コスタリカの扇状地からみた沖積扇状地と巨大扇状地の比較<渋谷治美教授退職記念特集>
別タイトル
Comparison between Alluvial Fans and Megafans based on Costa Rican Fans
著者
斉藤, 享治 (SAITO, Kyoji)
埼玉大学教育学部社会科教育講座 (Faculty of Education, Saitama University)
[出版社版]
出版者 埼玉大学教育学部
日付
出版年: 2014 - 2014
作成日: 2014-03-04
更新日: 2014-12-16
上位タイトル
埼玉大学紀要. 教育学部 (Journal of Saitama University. Faculty of Education). Vol.63, No.1  (2014. ) ,p.185- 192
識別番号
ISSN
18815146
抄録 There is a discussion whether megafans are alluvial fans or not. It is difficult to define whether the formation processes of megafans are the same as those of alluvial fans or not, because the surface deposits are sometimes different from the fan deposits. However, strong relationships between drainage basin areas and fan surface areas exist in alluvial fans with the same processes. Kesel (1985a, b) stated that alluvial fans in the General Valley of Costa Rica are larger than many arid fans with comparable drainage basin areas and that the position of the Kosi megafan closely coincides with the trend line of the Costa Rican fans. The statement suggests that the megafan is a member of the alluvial fans. Hence, the relationships between drainage basin areas and fan areas, including the Costa Rican fans are examined in this study. Alluvial fans over 2 km2 in area and steeper than 0.002 in mean fan slope were collected, and the drainage basin and fan areas were measured by use of 1: 50,000 topographic maps. In Costa Rica there are 18 alluvial fans, including four fans in the General Valley. The regression line between drainage basin areas and fan areas is shown by Af = 0.59 Ad0.71, where Af and Ad mean fan area and drainage basin area respectively. The regression line in Costa Rica is similar to those in Japan, Taiwan, the Philippines and New Zealand. For the comparison between alluvial fans and megafans, the Kosi megafan, Okavango fan, and five megafans in the Gran Chaco to the east of the Andes are chosen. The positions of seven megafans are beyond regression lines of five regions, including Costa Rica. Seven points are around regression lines in the San Joaquin Valley by Bull (1964) and in the General Valley by Kesel (1985a). The fan areas by Kesel are overestimated in the General Valley. Therefore, the comparison between drainage basin areas and fan areas in the San Joaquin Valley will be required in future.
キーワード
扇状地
沖積扇状地
巨大扇状地
コスタリカ
Alluvial fan
Megafan
Fan area
Drainage basin
Costa Rica
言語
jpn
資源タイプ text
ジャンル Departmental Bulletin Paper
著者版フラグ publisher
Index
/ Public / 埼玉大学 / 教育学部
/ Public / 主題別 / 総合領域 / 地理学
/ Public / ジャンル別 / 研究紀要 / 埼玉大学 / 教育学部紀要
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