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

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.

About two months before Maunaloa spewed lava, geologists detected small earthquakes nearby and other signals. Now a study of the volcano’s lava confirms that molten rock within Earth's crust was rising upward about 70 days before the eruption in late November 2022.