Rock slide - Rock slide

Japanese: 岩屑すべり - がんせつすべり

...Some contain a large amount of water, while others contain little water and flow like an avalanche, entraining air like a powder flow at extremely high speeds.
[Slide]
Slope material slides upward from the sliding surface, and can be broadly classified into slump, debris slide, and rock slide from slowest to fastest, and are sometimes collectively called landslides. Relatively small-scale events that occur at the edge of cliffs are called cliff failures or landslides, relatively slow sliding that occurs on the slopes of mountains and hills is called a landslide, and rapid sliding that appears to collapse is often called a landslide.

From [Landslide]

...They differ from slow-moving landslides in that they occur suddenly, the speed of material movement is extremely fast, and the collapsed parts collapse so much that they no longer retain their original shape. Slope collapse phenomena generally referred to as landslides include debris slides, in which surface rock debris slides down the slope; rock slides, in which rocks are peeled off from the bedrock and slide down the slope; debris avalanches, in which rocks and debris collapse all at once and slide down the slope at high speed; and even the collapse of a volcanic body due to volcanic activity. Large-scale landslides often turn into debris flows or mud flows midway and flow down the valley.

*Some of the terminology that refers to "rock debris slide" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

Japanese:

…多量の水を含むものと，あまり水を含まず粉体流のように空気を巻き込み，きわめて高速でなだれ落ちるように流下するものがある。
［滑動］
　斜面物質がすべり面から上をすべり動くもので，遅いものから早いものへスランプslump，岩屑すべりdebris slide，岩石すべりrock slideに大別され，地すべりと総称されることもある。崖端に生じる比較的小規模のものを崖崩れまたは土砂崩れ，山や丘陵の斜面に生じる比較的緩慢な滑動を地すべり，急速に崩れ落ちるようにして滑動する現象を山崩れということも多い。…

【山崩れ】より

…発生が突発的で物質の移動速度がきわめて速く，崩れ落ちた部分が原形をとどめないほど崩壊する，などの点で動きの緩慢な地すべりと異なる。　一般に山崩れと総称される斜面崩壊現象には，表層の岩屑が斜面をすべり落ちる岩屑すべり，基盤岩から岩盤が剝がれてすべり落ちる岩石すべり，岩盤や岩屑が一挙に崩れて高速で斜面をすべり下る岩屑なだれ，さらには火山活動による火山体の崩壊などを含んでいる。規模の大きな山崩れでは，途中から土石流や泥流に変わって谷を流下することが多い。…

※「岩屑すべり」について言及している用語解説の一部を掲載しています。

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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