volcanic action; volcanism
Geological term referring to processes related to volcanic activity, such as eruptions, lava flows, and related phenomena.
The landscape of this region was formed by volcanic action.
火山活動 is more common in everyday contexts and news reports, while 火山作用 is a more technical geological term.
Compound of 火山 (volcano) and 作用 (action, effect). The term is a direct translation of the English 'volcanic action' and is used primarily in scientific contexts.