Iceland’s Holuhraun Lava Field Produces Significant Amounts of Volcanic Gases

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Gas from the Holuhraun lava field.

The Holuhraun lava field produces a visible plume of volcanic gas. Image by NASA

Volcanic eruptions can last a long time.

While most of the planet’s more notorious events are spectacular and relatively short-lived, characterised by the immense explosions associated with volcanoes such as Mount St Helen’s and, more recently, Japan’s Mount Ontake, some type of eruptions are typified by long-lasting outpourings of lava which can reach extraordinary proportions.

While Iceland’s ongoing eruption at Bárðarbunga is a mere youngster – having been going only since September (compare that with Kilauea, on Hawaii, which has been erupting for over 20 years) it has nevertheless produced some startling statistics, and is worthy of comment and examination.

Updating Bárðarbunga: Not Just Lava

It isn’t just the quantity of lava Bárðarbunga produces — latest reports indicate that the new lava field now covers an area of almost 70 square kilometres.  According to the National Geographic (quoted on the Iceland Meteorological Office website) “has buried, on average, an area the size of an NFL football field every 5.5 minutes.

It’s the gas.

Because Bárðarbunga has produced gases — particularly sulphur dioxide (SO2) — in literally eye-watering quantities.

Indeed, current information reported in the journal Nature indicates that the amount of SO2 entering the atmosphere from Bárðarbunga is around 35,000 tonnes daily — which, note National Geographic, is “more than twice the amount spewing from all of Europe’s smokestacks.

Volcanic Gas and Pollution

Observed ccurrence of sulphur dioxide, November 2014

Citizen science maps observed incidences of volcanic gases. Image by Icelandic Met Office

The amount of gas produced depends on the chemical composition of the lava which emerges. Typically, volcanoes emit varying amounts of gases which are predominantly water vapour, carbon dioxide and sulphur dioxide but other gases are also produced in smaller quantities: Iceland’s Directorate of Health lists these as including hydrogen, hydrogen sulphide, carbon monoxide, hydrogen chloride, hydrogen fluoride and helium.

These gases have different implications for the earth system (with carbon dioxide associated with atmospheric warming and sulphur dioxide with cooling); but the main concern with regard to the current eruption at Bárðarbunga is that of human health.

Sulphur dioxide, in particular, is a toxic gas: the IDH warns of: “irritation in eyes, throat and respiratory tract and people can experience difficulties in breathing in high concentrations of SO2.”

The Bárðarbunga Eruption: Gas Pollution

So what’s the current situation in Iceland? As long as large volumes of gas continue to be emitted (there are no signs at present of the eruption stopping and, as noted above, such events can continue for years) there is potential for adverse impacts on human health.

Maps such as this are valuable tool in managing the hazard caused by volcanic gas. Image by Iceland Met Office.

Maps such as this are valuable tool in managing the hazard caused by volcanic gas. Image by Iceland Met Office.

The nature of that impact is determined partly by the wind direction relative to the population. Using a combination of instrumental monitoring and citizen science (reports from members of the public about indicators of gas) the IMO has produced maps of the existing distribution and short-term (two day) forecasts for the future.

Gas Emissions: The Future

At present the eruption of Bárðarbunga doesn’t appear to be generating significant problems for Icelanders. But who knows how long it will continue? History shows that Iceland is capable of producing eruptions which are much-longer lasting than that at Bárðarbunga, and that the impact of gas emissions can be devastating.

One of the largest, and possibly the most notorious, of Iceland’s eruptions (that at Laki in 1783-4) lasted for eight months. Laki was exceptional in its volume (its lava flows covered an area of over 550 square kilometres) and in its toxicity, with an estimated 122 megatons of sulphur dioxide related into the atmosphere. This gas, and others, are thought to have accounted for thousands of deaths locally and possibly millions elsewhere as cooling caused crop failure across Europe.

Fortunately there’s no sign of the Bárðarbunga eruption reaching the scale of Laki; and modern methods of forecasting and healthcare mean that pollution is less of a problem than it has been in the past. The current eruption indicates, nevertheless, that the dangers of volcanic eruptions go far beyond the immediate area.

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