<雲南懇話会からの寄稿>ランタン谷の雪崩堆積物と氷河変動、および災害地形について --2017年春のネパール・ヒマラヤのフィールド・ノート--

Abstract

From 27 March to 5 April 2017, I made a short excursion to Langtang village suffered from a huge avalanche that occurred on 25 April, 2015, at the time of the Gorkha earthquake and it was my Langtang trekking for the first time in 20 years. Also, I visited Kyanjin for measuring the Khimshun glacier terminus that I had once been to the area in 1975. Here, I would like to present a report of 1) the avalanche sediments of Langtang village and 2) the terminal change of Khimshun glacier, and 3) the related environmental issues on landslide disasters in Langtang valley as many hotels and restaurants are now rapidly built up under dangerous topography. Main results from this study are as follows. 1) there are two ice bodies in the avalanche sediments firstly formed on 25 April right after the Gorkha earthquake and secondly on 2 May at the time of aftershocks, and the ice bodies will be remain for at least ten more years according to the superficial melting rate. We must be very careful that another avalanche will hit the Langtang village after collapse of the hanging glacier located in the upper part of Langtan village. 2) The retreating rate of the Khimshun glacier is not so large as compared to that of the Gyajo glacier in the Khumbu region of the east Nepal showing the characteristic difference of glacier types; such as a hanging glacier of the former and a cirque one of the latter. 3) As some of hotels and restaurants are newly built near dangerous talus topography in the Langtang U-shaped valley, so we have to investigate it's security of these facilities before we stay.