How ancient Scottish rocks throw ‘snowball Earth’ theory up in the air

The Garvellachs off the west coast of Scotland, where well-preserved rocks reveal climate conditions during the snowball Earth period. Photograph: Prof Thomas Gernon/University of Southampton

During the ”snowball Earth” period about 700m years ago, Earth’s climate shut down. The planet was encased in ice and insulated from seasonal variations: spring, summer, autumn and winter all stopped. Or at least that was the theory.

Recent examination of some ancient rocks from the west coast of Scotland has now overturned that thinking, suggesting there were periods during snowball Earth when the climate woke up.