Water, sulphur and carbon dioxide, which are cycled through the deep Earth, play a key role in the evolution of our planet — including in the formation of continents, the emergence of life, the concentration of mineral resources, and the distribution of volcanoes and earthquakes. Subduction zones, where tectonic plates meet and one plate sinks beneath another, are a key part of the cycle — with large volumes of water going into and coming out from the Earth, mainly through volcanic eruptions.
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