The meltwater from the glacier on top of the volcano ran down into the crater, chilling the magma and then the pressure from underneath caused an explosion.

火山顶部的冰川融水流进了火山口，冷却了岩浆，随后来自底部的压力造成了爆炸。

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Types of lakes: tectonic lake, crater lake, fluvial lake, dammed lake, glacier lake, karst lake, Aeolian lake, impact crater lake and artificial lake.

湖泊分类：构造湖、火山口湖、冲积残留湖、堰塞湖、冰川湖、喀斯特湖、风成湖、陨石撞击湖和人工湖。

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The worst case scenario for distances beyond that is if the heat from the magma melts the glacier in the crater.

BBC: NEWS | Americas | Concern over rumbling US volcano

Visual observations and photographic analysis show evidence of uplift of the scale of tens of metres of part of the glacier in the crater and of the lava dome.

BBC: NEWS | Americas | Mount St Helens on highest alert