Japan Geoscience Union Meeting 2018

Presentation information

[JJ] Oral

M (Multidisciplinary and Interdisciplinary) » M-GI General Geosciences, Information Geosciences & Simulations

[M-GI25] Environmental changes in mountainous area

Tue. May 22, 2018 9:00 AM - 10:30 AM A08 (Tokyo Bay Makuhari Hall)

convener:Keisuke Suzuki(Department of Environmental Sciences, Faculty of Science, Shinshu University), Yoshihiko Kariya(Department of Environmental Geography, Senshu University), Chiyuki Narama(新潟大学理学部理学科, 共同), Akihiko SASAKI(Department of Geography and Environmental Studies, Kokushikan University), Chairperson:Kariya Yoshihiko(専修大学)

9:30 AM - 9:45 AM

[MGI25-03] Formation and development of wetlands in response to development of large-scale landslides in the Ou Mountains

*Natsuki Sasaki1, Toshihiko Sugai1 (1.Graduate School of Frontier Science, The University of Tokyo)

Keywords:landslide, geomorphic development, wetland, Ou Mountains

Quaternary volcanoes in the Ou Mountains are being denudated by landslides while leaving gentle volcanic surfaces widely. Many wetlands formed on the original volcanic surfaces with heavy snow and the landslide areas create their rich ecosystems (Sasaki and Sugai, 2016). Large-scale landslides with huge mass markedly contribute to the formation of mountain wetlands. This study aims to reconstruct the development of wetlands in large-scale landslides in the Sengan and Funagata volcanic areas with sediment analysis, and to interpret that landslide activities and their subsequent geomorphic changes formed and developed wetlands. In this study, we use “wetland” for natural lakes and peatlands.

Oyachi wetland in the Komonomori landslide in the Sengan volcanic area, appeared as a large lake about 5,500 years ago and developed into a peatland about 3300 years ago. These could be caused by geomorphic changes. The south Chausu-dake landslide with intensively dissected landslide masses has a lake in their upper part. The lake could have survived for more than several thousand years, longer than the lifetime of Oyachi wetland. In the Sugenuma landslide in the Funagata volcanic area, the initial slide of about 40,000 years ago, the re-activation after 10,000 years ago (Yagi, 1990) and the subsequent geomorphic changes formed wetlands one after another.

The period of landslide activity was estimated to be 10–100 thousand years (Yokoyama, 2004), and disappearance time of landslide was also estimated to be about one million years (Yanagida and Hasegawa, 1993). While wetlands formed by initial landsliding remain as lakes or peatlands for over thousands of years, landslide reactivities and other geomorphic changes added new wetlands. This situation could potentially continue for almost one million years, which is longer than the glacial-interglacial cycle. Wetlands exist successively in the large-scale landslides to preserve rich ecosystems for a long period.


Sasaki, N. and Sugai, T. (2016) Distribution of Wetlands and Environment of Formation in Hachimantai Volcanic Group, NE Japan. Proceedings of annual meeting of the Association of Japanese Geographers, 89, 233.

Yagi, R. (1990) The large landslides since the Last Glacial Age in and around Mt. Funagata and Izumigatake volcanoes, northeastern Japan. Annals of The Tohoku Geographycal Asocciation, 42, 131–151.

Yanagida, M. and Hasegawa, S. (2000) Formative age of landslide topography: How long landslide topography exist?. Abstracts of the annual meeting of the Japan Landslide Society, 39, 591–594.

Yokoyama, S. (2004) Evolutionary series and evolutionary stage. Committee of geographycal and geological terminology on landslide the Japan Landslide Society (ed). Landslide: Topographical and geological recognition and terminology: 46–52, the Japan Landslide Society.