Volcanic Steam When Lava Meets Ocean: A Hidden Health Hazard Called “Laze”
Most people think of glowing red rivers of lava or explosive ash clouds when they picture a volcanic eruption. But in coastal volcanoes like Kīlauea in Hawaiʻi or the ongoing eruptions in Iceland’s Reykjanes Peninsula, one of the most immediate public health threats isn’t the lava itself; it’s the white plume that billows up where 2,000 °F (1,100 °C) molten rock slams into cold seawater. That plume is called laze — a word formed from “lava” + “haze” — and it is far more dangerous than it looks. #### What Exactly Is Laze? When lava instantly boils seawater, two dangerous things happen: 1. Hydrochloric acid (HCl) cloud Seawater contains chloride salts. Superheated lava flashes the water into steam and reacts with those salts to produce concentrated hydrochloric acid vapor. Concentrations can reach levels similar to battery acid in the air. 2. Tiny shards of volcanic glass The explosive shattering of lava creates microscopic particl...