Scientists can’t know precisely when a volcano is about to erupt, but they can sometimes pick up telltale warning signs.

An analysis of crystals in lava from the 2022 eruption of Mauna Loa has revealed an unknown magma reservoir within the volcano, which could extend forecasts of eruptions from minutes to months

That happened two years ago with the world’s largest active volcano. About two months before Mauna Loa spewed rivers of glowing orange molten lava, geologists detected small earthquakes nearby and other signs, and they warned residents on the Big Island.