Our directory of things of interest

University Directory

Sulphur breath: tracking the emissions of volcanoes

The sulphur fumes of Mount Ijen in East Java, Indonesia The sulphur fumes of Mount Ijen in East Java, Indonesia Shutterstock
12 Apr
In a new report, researchers have calculated the global emissions of sulphur dioxide caused by volcanic activity

Sulphur dioxide (SO2) is an aerosol that cools the atmosphere, can cause acid rain, and, at low altitudes, causes respiratory problems in humans. Volcanoes are natural sources of the gas and often we associate these emissions with dramatic eruptions. In reality, however, most of the gas is emitted when they are not erupting – through their everyday puffing and steaming.

‘Daily volcanic emissions are a constant input to the Earth’s atmosphere,’ says Simon Carn, lead author of a new report on global volcano emissions and associate professor at Michigan Tech in Houghton, Michigan. ‘These can impact climate in more subtle ways than a big eruption.’

Mount Erebus in AntarcticaMount Erebus in Antarctica was monitored from space for the first time (Image: Pagnanelli)

In order to get a good idea of how much SO2 is being regularly released, Carn and his team have used satellite data look at the respiration of 91 active volcanoes across the globe from 2005 to 2016.

They found that 20 to 25 million tons of SO2 are being emitted annually, considerably higher than a previous estimate of made in the 1990s of 13.4 million tons. However, Carn believes that this doesn’t mean that volcanoes are emitting more, only that measurements are becoming more accurate:

‘The satellite measurements we used cover the entire globe, and so we were able to measure emissions from many more volcanoes than any previous study.’

The global range of the satellite data also brought some surprises. Strong SO2 pulses were detected from volcanoes that had been completely off the radar to most volcanogists. ‘Many volcanoes were known to be strong emitters of gas,’ he says, ‘but a few in remote parts of countries like Indonesia and Tonga were new discoveries.’

newnewgifThe wax and wane of volcano emissions on the coast of Central America (Image: Carn et al)

While the collective SO2 has stayed the same, changes can be seen at an individual level. This is because emissions of SO2 are mainly related to the supply of fresh magma. ‘A volcano’s variable magma supply would cause its emissions to wax and wane over time,’ says Carn. ‘Meanwhile, volcanoes with a continuous supply of magma have roughly constant emissions.’ Because of the gas and magma relationship, changes in SO2 can also be used to forecast potential eruptions.

AsoMount Aso, Japan showed an increase in SO2 emissions before eruptions in 2014 and 2016 (Image: Shutterstock)

Human activity produces twice the amount of SO2 as volcano emissions, mostly by the burning of fossil fuels – particularly solid fuels such as coal. Over the past few decades, however, stricter policies and changes to industry have brought about a steady decline of human emissions of the gas. As this continues, volcano monitoring will continue to demonstrate the natural background levels of SO2.

Related items

Subscribe to Geographical!

geo line break v3

Free eBooks - Geographical Newsletter

Sign up for our weekly newsletter today and get a FREE eBook collection!

geo line break v3

University of Winchester

geo line break v3


Aberystwyth University University of Greenwich The University of Derby




Travel the Unknown


Like longer reads? Try our in-depth dossiers that provide a comprehensive view of each topic

  • Natural Capital: Putting a price on nature
    Natural capital is a way to quantify the value of the world that nature provides for us – the air, soils, water, even recreational activity. Advocat...
    The human game – tackling football’s ‘slave trade’
    Few would argue with football’s position as the world’s number one sport. But as Mark Rowe discovers, this global popularity is masking a sinister...
    Essential oil?
    Palm oil is omnipresent in global consumption. But in many circles it is considered the scourge of the natural world, for the deforestation and habita...
    When the wind blows
    With 1,200 wind turbines due to be built in the UK this year, Mark Rowe explores the continuing controversy surrounding wind power and discusses the e...
    The Money Trail
    Remittance payments are a fundamental, yet often overlooked, part of the global economy. But the impact on nations receiving the money isn’t just a ...


NEVER MISS A STORY - Follow Geographical on Social

Want to stay up to date with breaking Geographical stories? Join the thousands following us on Twitter, Facebook and Instagram and stay informed about the world.

More articles in NATURE...


Bonnethead sharks, the second smallest member of the hammerhead family,…


There’s more than enough plastic in the world. That’s why,…


The recent discovery of more than 200 million termite mounds…


The new year still remains a popular time to set…


After decades battling environmental crises that threaten to rob the…


As another new year beckons and the fight to protect…


A half century has passed since the ‘Earthrise’ photograph – widely believed to have…


Are howler monkeys being adversely affected by ingestion of pesticides containing…


Why unprepared tourists are putting themselves at risk in order…


The majestic and mighty polar bear is in danger of…


Exciting news for wildlife and photography enthusiasts alike – the…


A new system of robotic aerial vehicles is revolutionising the…


Technology used in creating safe urban environments is now being…


Brazil’s shift to the right of the political spectrum could…


Laura Cole travels to Orkney to find out why numbers…


The unprecedented frequency of winter tick epidemics have resulted in…


Ocean debris, mostly composed of plastic, reaches remote Atlantic islands…


With motion detectors becoming ever more sophisticated, and clearer, crisper…


Natural capital is a way to quantify the value of…


The reason for the unusual location of Mount St Helens…