A volcanic eruption can darken skies and cool the planet for a year or two. New research suggests that some of the largest eruptions did something far more powerful: they pushed Earth into cold spells that lasted for centuries. Paine and an international team instead examined whether explosive volcanic eruptions may have provided the initial shock. Every known Holocene eruption with a magnitude of 7 or greater occurred close in time to a glacier advance. Ancient Eruptions Unleashed Massive Sulfur LoadsSome Holocene eruptions released extraordinary amounts.