The Kilauea volcano is wreaking havoc on Hawaii’s Big Island—so far, 12 fissures have opened over the last two weeks, and magma has devoured 35 homes and other structures in the area. But that magma also poses a secondary threat. Magma contains lots of sulfur dioxide (SO2), a colorless, foul-smelling toxic gas also produced by power plants, shipping vessels, and anything else with a combustion engine.
SO2 is typically locked inside magma when it’s far below ground. But when it begins to rise to the surface, the magma belches out its SO2. “The process is similar to what happens when a bottle of soda is opened,” Ashley Davies, a volcanologist at NASA’s Jet Propulsion Laboratory, explained in a NASA release. “There’s usually an increase in sulfur dioxide output right before lava reaches the surface, as the gas escapes from the ascending magma.”
NASA satellites detected a spike in the gas over Kilauea on May 5, two days after the first fissures began to burst open. On May 6, another NASA satellite sensor found a “sizable plume” streaming out of the fissures that opened in Leilani Estates, the residential community most affected by the Kilauea emergency so far.
Right now, Leilani Estates is spared the worst of the toxic gases, because trade winds have pushed the plume offshore, according to NASA. But “Hilo and other communities northwest of Leilani Estates could see air quality deteriorate if the trade winds weaken,” NASA’s Adam Voiland wrote.
The SO2 can “cause acid rain and air pollution downwind of a volcano,” according to the US Geological Survey. Kilauea, the most active volcano on Hawaii, is known to release “particularly high concentrations of sulfur dioxide produce volcanic smog (‘vog’) causing persistent health problems for downwind populations.” Eruptions of magma also release vast quantities of steam, which is completely harmless, as well as smaller quantities of hydrogen sulfide (“very toxic at high concentrations”) and fluorine, chlorine, and bromine (“strong, toxic acids”) according to the USGS.
People with respiratory problems are most at risk, but even otherwise healthy people can end up with pneumonia-like symptoms or difficulty breathing, according to the Washington Post:
Jennifer Griswold, an assistant professor at the University of Hawaii at Manoa, told KHON-TV in 2017 about her reaction to vog when she first moved to Hawaii.
‘It felt like I had really severe tooth pain, or like I needed a root canal, or like someone was stabbing me in the face,’ Griswold said. ‘I ended up going to a dentist who told me that my sinuses were so inflamed from the vog that they were essentially crushing the nerves of my teeth.’
Volcanoes can also release vast quantities of carbon dioxide, or CO2. Typically, the CO2 dilutes as it mixes with the surrounding air. But just like cold air sinks, so does cold CO2. As the warmer CO2 rises and gets diluted in expanses of air, cooler CO2 falls, and can accumulate in small recesses, where it can quickly build up to dangerous concentrations since there is a lesser volume of air to mix with. Breathing air that’s more than 3% made up of CO2 can cause headaches and trouble breathing, but breathing air that’s more than 15% CO2—which can happen in low areas as the CO2 sinks—is lethal. According to the USGS:
In volcanic or other areas where CO2 emissions occur, it is important to avoid small depressions and low areas that might be CO2 traps. The boundary between healthy air and lethal gas can be extremely sharp; even a single step upslope may be adequate to escape death.
And in case you were wondering, even though it can harm human health, all that CO2 released from volcanoes is still “insignificant when compared to emissions from human activity,” says the USGS. So no, volcanoes are not causing global warming. It’s still us.