Article

Volcanoes on Trial: How Bad Are They for the Environment?

Introduction
CO₂Emissions
SO₂ Emissions
Geothermal Energy from Volcanoes
Sources and Further Reading

Introduction

A volcanic eruption is one of the most awe-inspiring sites in nature, but these phenomenal natural events are seen as a danger on a grand-scale. Volcanic eruptions can devastate whole communities, cause death and destruction and even render entire islands almost uninhabitable. They have also been blamed for global warming. But are volcanoes really all that bad? This article explores how much volcanoes contribute to climate change, and whether they can contribute significantly to clean technology.

The monumental eruption of Mount Pinatubo, Philippines on June 12, 1991. Image Credit: USGS, Dave Harlow.

CO₂Emissions

When a volcano erupts, it releases billions of tonnes of gas into the atmosphere, some of which can have a drastic impact on the global climate. Sulphur dioxide is released into the atmosphere which can lead to global cooling and carbon dioxide is also released which can lead to global warming.

Some people are under the impression that volcanoes emit more CO₂per year than human activity, and are therefore a bigger threat to global warming. However, it has been proved time and time again this that is simply not true. In fact, it has never been show that contemporary volcanic eruptions have caused any degree of global warming. It is debated that large scale volcanic activity could have caused short-term global warming in the past, and even contributed to mass extinctions such as the end of the dinosaurs, but nothing on this scale has been experienced in recorded history.

Studies show that the amount of CO₂ released by volcanoes each year is less than 1% of the CO₂emissions caused by human activities. In an average year, all volcanoes erupting on Earth will collectively emit a maximum of 0.26 billion metric tons(Gt) of CO₂. This may sound a lot, but it is dwarfed by the 35Gt currently released by humans every year-and this is ever increasing. Even some of the largest volcanic events in history, such as the eruptions of Mt. St. Helens, 1980 (0.01Gt of CO₂) and Mount Pinatubo, 1991 (0.05Gt of CO₂) would barely be felt amongst the total anthropogenic emissions.

SO₂Emissions

A slightly more viable concern is volcanoes contributing to global cooling. The sulphur dioxide emitted by a volcano is converted into a fine aerosol of sulphuric acid in the atmosphere, which reflects sunlight back into space, leading to cooler temperatures.

A famous historical example of this occurred when the craters of Laki in Iceland erupted, between 1783 and 1784. This eruption was the second largest in the last thousand years and spewed out an estimated 120 million tons of sulphur dioxide, along with around 8 million tons of hydrogen fluoride. This cloud of gas rose high into the atmosphere and spread across Europe, causing widespread devastation. Many people died as a direct result of this gas, due to the sulphur dioxide mixing with water vapour and choking people to death.

The eruption also caused wild fluctuations in the climate of Europe: In Britain, the July of 1783 was the warmest month ever recorded. However, the worst consequence of the eruption was the following winter which was the most severe in recorded history, with major crop failures and loss of livestock. As a result, a 5th of the population of Iceland was wiped out, along with many thousands across Europe.

There are similar examples dotted throughout history. The eruption of Mount Pintubo in 1991 threw so much SO₂ into the atmosphere that the Earth cooled by 1.3^oC, and the effect was felt for years afterwards.

Though unlike CO₂ the SO₂ emissions of a volcanic eruption do have a measurable effect on the climate, these affects are short-term and do not affect overall warming trends over decades or centuries, let alone millions of years.

Geothermal Energy from Volcanoes

So if volcanoes are not causing global warming, is it possible they could help us to prevent it? Recent research has shown that it may be possible to harness the immense geothermal energy produced by volcanoes and use it as a renewable fuel source, thus cutting the worlds dependence of CO₂-producing fossil fuels.

MIT has presented research that suggests that if even 2% of the heat below the Earth’s volcanoes is harnessed, it could provide enough energy for the entire United States 2500 times over. Furthermore, unlike solar and wind power, this geothermal energy is not reliant on weather conditions.

Knowing that the energy is there is one thing, but actually harnessing it in a safe and consistent way is a very different prospect. The favoured method of accessing this energy currently is EGS, or Enhanced Geothermal Systems. . This involves pumping millions of gallons of water into dormant volcanoes via wells, which is then heated by the thermal energy under the volcano. Once this water has been heated to extremely high temperatures, it is transported to the surface where the heat energy is then extracted.

One of the major issues is whether enough water can be pumped through the system to make this form of energy economically viable. Another major concern is whether the ‘hydroshearing’ used to create the wells will lead to earthquakes. This is still somewhat an unknown quantity and so the jury is still out on whether volcanoes can becomes man’s new best friend.