Almost a millennium ago, a major upheaval occurred in Earth’s atmosphere: a giant cloud of sulphur-rich particles flowed throughout the stratosphere, turning skies dark for months or even years, before ultimately falling down to Earth.
We know this event happened because researchers have drilled and analysed ice cores — samples taken from deep within ice sheets or glaciers, which have trapped sulphur aerosols produced by volcanic eruptions reaching the stratosphere and settling back on the surface.
Ice can thus preserve evidence of volcanism over incredibly long timescales, but pinpointing the precise date of an event that shows up in the layers of an ice core is still tricky business.
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