Earth

Venting volcanoes

Eruptions release bromine, a chemical that destroys ozone layer

June 22, 2012 at 8:00 am

When volcanoes erupt, they can release ash, chunks of rock and torrents of lava. Now scientists have found those eruptions also can spew massive amounts of a chemical called bromine. This gas helps destroy the ozone layer. That’s a layer of the upper atmosphere that protects life on Earth from the sun’s harmful ultraviolet rays.

The researchers made this discovery by studying rocks left over from ancient volcanic eruptions in Central America. The eruptions released enough bromine to leave the ozone layer partly damaged for several years afterward, the scientists now estimate.

“We have to be aware of this,” team member Kirstin Krüger says. She was speaking June 12 at an American Geophysical Union conference on volcanoes and the atmosphere. “Large-scale tropical eruptions have the potential to deplete ozone on a big scale.” Krüger is a meteorologist, someone who studies the atmosphere. She works at the GEOMAR Helmholtz Centre for Ocean Research in Kiel, Germany.

The affected layer of the atmosphere, high above Earth’s surface, is rich in ozone. This is a molecule made of three oxygen atoms. This ozone layer helps block part of the sun’s light, called ultraviolet radiation. Some ultraviolet radiation can cause skin cancer or other diseases in people.

Krüger’s team studied 13 volcanic eruptions in Central America. They took place over the last 70,000 years. For their analyses, the researchers collected rocks that formed during the eruptions. The rocks contained little glass bubbles.

Then the team measured bromine levels in the glass bubbles. By figuring out how much had been trapped in the rocks, the researchers could estimate how much bromine the volcano had belched out. Each eruption spewed 4,000 to 600,000 tons of bromine, the team now concludes.

Volcanoes are not the only cause of ozone layer damage. Most bromine in the atmosphere comes from chemicals used by people. For example, methyl bromide is a chemical used to control pests on farms. In addition, chemicals called chlorofluorocarbons, also contribute to ozone layer destruction. These are chemicals used in refrigerators and air conditioners. Many countries have agreed to cut their use of these ozone-harming chemicals.

The research by Krüger’s team could help scientists estimate the amount of bromine released by today’s volcanic eruptions. “If we can apply this to other volcanoes, we can really get a handle on how much bromine is coming out,” Tamsin Mather, a researcher who studies volcanoes at the University of Oxford in England, told Science News.