A Volcano Blew Up Half the Ocean Floor and Accidentally Cleaned the Sky

Listen to Volcane Ate Methane

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Volcanoes have a reliable reputation. They go up, they send things into the atmosphere, and those things (ash, sulfur dioxide, water vapor) generally make the sky worse for a while. The 2022 eruption of Hunga Tonga–Hunga Ha'apai did all of that, loudly and at considerable scale. But it also did something that wasn't on anyone's list.

It ate methane.

Not intentionally (volcanoes, to be clear, have no intentions), but the chemistry worked out that way. The eruption launched enormous quantities of salty ocean seawater into the stratosphere, an unusual feature of this particular event, given that the volcano sat on the seafloor. Up there, sunlight hit the mix of sea salt and volcanic ash and produced reactive chlorine atoms. Chlorine is not gentle with methane. It breaks it apart. The byproduct of that breakdown is formaldehyde, which under normal conditions disappears within a few hours.

Scientists watching satellite data saw a formaldehyde cloud that persisted for 10 days and traveled as far as South America. Something in that plume was continuously destroying methane the entire time.

This chemistry (salt, sunlight, chlorine, methane) had been documented before at low altitudes over the Atlantic, where Saharan dust mixes with sea spray. Finding it operating in the stratosphere, at conditions entirely different from anything it had been observed doing before, was not expected.

Methane is the climate problem on a short fuse: it traps heat about 80 times more aggressively than CO2 over 20 years, but it clears the atmosphere in roughly a decade. Reduce it fast enough and the results show up within a human lifetime. Scientists call it the climate "emergency brake." The Tonga eruption appears to have tapped that brake, briefly, without meaning to.

David, who has the stronger opinions in our household on silver linings, found this very satisfying. The volcano had no comment.

Read the full story at Earth.com, May 11, 2026

Hot Take: The atmosphere has been running chemistry experiments without a permit for four and a half billion years; the fact that we're only now catching it in the act says more about our instruments than about the atmosphere's ambitions.