These tree trunks were petrifi ed when a volcanic eruption covered them in ash.


WORDWISE caldera: a large volcanic crater


fumarole: a dry geyser, through which hot gases emerge


geyser: a hot spring in which water boils and shoots a column of water and steam into the air


hot spring: a pool of naturally hot water, typically heated by underground volcanic activity


mud pot: an acidic hot spring with little water that breaks rocks down into clay


petrifi ed forest: a forest of trees that have been fossilized


Over time, acid in this hot spring breaks rock down into milky clay, forming a mud pot.


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