When a volcano erupts, dust is blasted[3] high above the tropo here and may take weeks to be carried around the weather zone, so ca ot be washed out of the air by rain.

• 火山爆发时，尘埃被高高喷射入对流层以上的空间，需要几个星期才飘浮移至气象层，因而雨水无法将其从大气中冲走。