Intriguing new evidence is emerging which suggests the dangers of climate change might go deeper than our rising seas. As if we didn’t have enough on our plate, could the vanishing polar ice caps also be about to unleash a long dormant volcanic force?
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It’s easy to get lost in the complexity of the climate change debate, but one thing, at least, is unfortunately clear: our planet is losing its cool. Whether or not you understand the finer details of a radiative forcing model, when you read that an area of ice the size of a country has melted, it hits home; with each passing year we are witnessing, with startling clarity, that the frozen expanses at our planet’s poles are undergoing a rapid and uncomfortable transformation.
But do we fully understand the dangers of an ice-free planet? The impacts of rising sea levels are clear enough, but recently there has been growing unease among Earth Scientists that the melting ice could be hiding a different kind of threat. Clues have begun to emerge in the rock record which hint that, at the end of the last ice age, as the land emerged from its long hibernation, something within the Earth itself began to stir.
Analysis of ancient lavas from Iceland have shown that around 12,000 years ago, volcanic activity there began to increase at an astonishing rate – with eruptions becoming up to fifty times more frequent [1]. And now, after similar patterns were discovered at volcanoes from Western Europe to the Americas, geologists are being forced to confront uncomfortable possibility: could climate change, while it was lifting our planet out of the ice-age, also have triggered this increase in volcanic activity?
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Until now, the response from Earth Scientists has been a unanimous “maybe” on the subject. But now new evidence has emerged, deep beneath Antarctica, which seems to strengthen the case for this unsettling theory. A new study [2], published this month in the Journal of Volcanology and Geothermal Research, not only suggests that climate change and volcanic activity might be linked, but that their relationship could go back much further than was previously thought.
The huge glaciers which smother the Antarctic continent are a treasure trove for climatologists; beneath its barren surface, layers of ice a mile thick have preserved an unmatched record of our planet’s climatic history. Yet as tough and imposing as this great southern wilderness might seem, deep down, it has a fragile heart. The climatic history of Antarctica itself is one of constant change: temperatures here have been rising and falling, and the great ice sheets growing and shrinking, for millions of years.
But there is another force at work beneath the frozen surface – one which makes this an ideal location to study the effect that ice can have on our planet’s deep interior. Antarctica may be the coldest place on Earth, but a vein of fire cuts up from below; the great lava lake of Mount Erebus is the modern-day remnant of volcanic activity which, alongside glacial forces, has shaped this enigmatic landscape over geological time.
And it was here that a team of Earth Scientists – led by Dr. Rosie Nyland of Bowling Green State University – headed for answers. In their study, Nyland and her co-workers analysed rocks from the volcanic heartland of Western Antarctica, extracted from more than a kilometer below the surface by the ambitious Antarctic Drilling Project (ANDRILL). On the shores of the Ross Sea, thick layers of marine sediment extend deep beneath the permafrost – the product of continuous glacial activity. Within the ANDRILL rock core, the researchers observed the telltale geological fingerprints of the rise and fall of ice sheets; and by accurately dating each sediment layer, it was possible for them to reconstruct how ice levels had changed over time – providing an amazing record of climate change stretching back more than twenty million years.
But something else had been preserved in the rocks. Littered throughout the sediments were layers of volcanic ash – unmistakable evidence that the area had been volcanically active while the rocks were being deposited. And the fortunate occurrence of this ash gave the team a unique opportunity: by measuring how the amount of volcanic material varied across different sediment layers, they were able to estimate how the strength of volcanic activity had changed over time. (Because larger eruptions tend to give off more ash, a particularly ashy layer indicates that volcanic activity was higher when those sediments were deposited – and the opposite true for layers with less ash).
And it was this crucial step which led to their breakthrough: when Nyland and her team compared the volcanic and glacial records, they they discovered a clear pattern – up to ten times more ash was deposited when ice cover was low than when ice was more widespread. Over a period of three million years, the strength of volcanic activity mimicked the amount of ice cover with remarkable consistency; in other words, here was clear evidence that climate change might have been the driving force for an increase in volcanic activity – not just once, but repeatedly.
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These new findings are the latest in a small but growing chain of evidence which suggests that, through the process of deglaciation, climate change could be able to trigger volcanic eruptions. If it was happening millions of years ago in Antarctica, and as recently as a few thousand years ago in Iceland, could it be that increased volcanic activity is an inevitable consequence of a warming climate?
In light of our current situation, this would certainly be a cause for concern. As we slide irreversibly into a man-made deglaciation, we are seeing the disappearance of ice which, throughout recorded history, has covered some of the world’s most volcanically active regions; the Antarctic ice sheet is among the most rapidly melting regions on Earth, and the glaciers which cap some tropical volcanoes are already vanishing completely. This raises the disturbing possibility that human actions might be about to remove a natural shield from our planet – one which has, until now, been keeping its destructive power at bay.
It should be noted, though, that this most recent study suggests that, in Antarctica at least, any increase in volcanic activity might not happen until several thousand years after deglaciation occurs. But that is not to suggest that we can afford to relax completely. With research at such an early stage, there is still significant uncertainty, and as more evidence accumulates, we could learn that other volcanoes respond to deglaciation in different ways. As an example of this, we need look no further than Iceland – our volatile northern neighbour – where the interval between deglaciation and the onset of volcanic activity seems to be alarmingly fast. If Europe can be brought to its knees by a single eruption from this island – and a particularly small one, at that – what could be in store for us if activity there increases in the future?
So while the volcanic effects of climate change might not be comparable with more immediate dangers – catastrophic flooding or soaring heatwaves, say – they should still remind us that our actions can affect the Earth in more subtle ways than immediately meet the eye. And that, while we are distracted by goings on at the surface, it helps to remember that we sit perched on a thin shell above a still-mysterious expanse below: the other 99% of our planet.
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References
1. Tuffen (2010): How will melting of ice affect volcanic hazards in the twenty-first century? Philosophical Transactions of the Royal Society; vol 368, no. 1919.
2. Nyland et al. (2013): Volcanic activity and its link to glaciation cycles: Single-grain age and geochemistry of Early to Middle Miocene volcanic glass from ANDRILL AND-2A core, Antarctica. J. Volcanol. Geotherm. Res. Vol. 250.
3. http://www.nature.com/news/greenland-defied-ancient-warming-1.12265
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