Eruptions Can Damage Ozone Layer

Volcanic eruptions in Nicaragua during the past 70,000 years injected enough bromine and chlorine into the stratosphere to potentially damage Earth’s ozone layer, scientists reported on June 12 at the American Geophysical Union’s Chapman Conference on Volcanism & the Atmosphere, in Selfoss, Iceland. Scientists have known that such explosive eruptions can transport these gases into the stratosphere. But this work, from Kirstin Krüger at GEOMAR Helmholtz Centre for Ocean Research Kiel, in Germany, and colleagues, is the first to show that the gases were emitted in quantities sufficient to deplete the ozone layer. The scientists analyzed minerals associated with 14 ancient Nicaraguan eruptions and estimated that stratospheric bromine and chlorine concentrations after the eruptions could have been 200 to 300% greater than 2011 concentrations. On the basis of a conservative estimate that 10% of emitted gases reached the stratosphere, 120 million metric tons of chlorine and 600,000 metric tons of bromine were released into the stratosphere by an eruption 24,500 years ago at the Apoyo Caldera. Just how much damage these eruptions caused to the ozone layer still needs to be determined, as does how much damage future eruptions could cause.