Flowing mountain

Japanese: 流れ山 - ながれやま

Small hills with heights of several meters to 100 meters and base diameters of several tens to several hundreds of meters are found densely at the foot of stratovolcanoes. They are formed on the surface of a steep stratovolcano when the top of the stratovolcano collapses due to a steam explosion or earthquake, causing the collapsed material to flow rapidly down the slope and accumulate at the foot of the mountain. Famous examples include Mount Bandai in 1888 and Mount St. Helens in the United States in 1980. Other examples include stratovolcanoes such as Oshima Komagatake, Mount Usu, Mount Iwaki, Mount Iwate, Mount Yatsugatake, Mount Asama, Mount Akagi, Mount Egmont and Mount Ruapehu in New Zealand, and lava domes such as Mount Mayu in Unzen and Shikaribetsu in Hokkaido.

Source: Heibonsha World Encyclopedia, 2nd Edition Information

Japanese:

おもに成層火山の裾野に密集して存在する比高数m～100m，底径数十～数百mの小丘。急峻な成層火山の頂部が水蒸気爆発，地震などを引金に大崩壊し，崩壊物質が急速に斜面を流下して山麓に堆積したときに，その表面に形成される。1888年の磐梯山，1980年のアメリカ合衆国のセント･ヘレンズ火山で生じたものが有名。ほかに渡島（おしま）駒ヶ岳，有珠山，岩木山，岩手山，八ヶ岳，浅間山，赤城山，ニュージーランドのエグモント山，ルアペフ山などの成層火山や雲仙眉山（まゆやま），北海道然別（しかりべつ）などの溶岩円頂丘に存在する。

出典　株式会社平凡社世界大百科事典第２版について　情報

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