Marie Edmonds is Professor of Volcanology and Petrology at Cambridge University.  She studies the cycling of volatile elements such as carbon between the atmosphere and the mantle and the role that volatiles play in melting, magma transport, and the style of  volcanic eruptions. She describes how all volcanos emit gas and how the gas can reveal a lot about the origin of the magma and also forewarn of eruptions.  Here is is monitoring gases emitted during the 2018 eruption of Kilauea on Hawaii.
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