volcanic sector collapse; debris avalanche
Geological term for a large-scale collapse of a volcanic edifice, often producing a debris avalanche. Used in technical and disaster-prevention contexts.
A large-scale debris avalanche was triggered by the sector collapse.
This volcano has experienced sector collapses many times in the past.
岩屑なだれ is the debris avalanche itself, while 山体崩壊 refers to the collapse event that causes it.
火山崩壊 is a broader term for volcanic collapse; 山体崩壊 specifically refers to the collapse of the volcanic edifice (the mountain body).
Compound of 山体 (さんたい, 'mountain body') and 崩壊 (ほうかい, 'collapse'). The term is used in volcanology and geology.