A new study unlocks the science behind a key ingredient — namely oxygen — in some of the world’s most violent volcanoes. The research offers a new model for understanding the oxidation state of arc magmas, the lavas that form some volcanoes, such as the one that erupted dramatically in Tonga earlier this year. The plume from Tonga’s underwater volcanic eruption on Jan. 15 rose 36 miles into the air. Ash from the volcano reached the mesosphere, Earth’s third layer of atmosphere.