It’s clear that Hunga involved an unusually explosive recipe that may not be easily replicated. For about a month, the eruption had progressed as expected—moderately violent, with gas and ash, but manageable. Then everything went sideways. That appears to be the result of at least two factors, Cronin says. One was the mixing of sources of magma with slightly different chemical compositions down below. As these interacted, they produced gasses, expanding the volume of the magma within the confines of the rock. Under tremendous pressure, the rocks above began to crack, allowing the cold seawater to seep in. “The seawater added the extra spice, if you like,” Cronin says.
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