著者

大山 正雄

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.120, no.6, pp.1013-1025, 2011-12-25 (Released:2012-03-05)

参考文献数

22

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Iceland is the northernmost country of the world. It is a volcanic island located immediately south of the Arctic Circle. Currently, about 11% of the island is covered with glacial ice. The Mid-Atlantic Ridge, which forms the spreading boundary between the Eurasian and the North American tectonic plates, passes through the middle of the island. It may be said that the natural phenomena in Iceland are formed by three elements: volcanoes, glaciers, and the plate boundary. We visited this geographically fascinating land in August 16-27, 2010. The volcanos and thermal springs are very active along the plate boundary. Most of the lavas are basalts. The thermal water is generally alkaline. The main rivers are braided meltwater rivers flowing from glacial areas. Because the meltwater rivers contain suspended sediments in abundance, the water is gray. A subglacial eruption caused a colossal flood and formed a vast outwash plain. Thermal water is used by geothermal power plants as well as heating systems because even the summers are cold. During this trip, we also observed fractures of the plate boundary, known as “gja” in Iceland.