Eyjafjallajökull
Eyjafjallajökull
Monday, 26 April 2010
The disruption to air travel in Europe certainly made news in the papers in Hong Kong this week, though not quite to the extent that was the case in Europe. We were told, for example, that supplies of air freighted fresh Norwegian salmon was in short supply in Hong Kong, and more bizarrely, lots of local concern was expressed for Kenya’s flower growers who were unable to ship their fresh flowers to the European markets. Fortunately, the situation did not deteriorate quite to the point where Hong Kongers had to start buying tickets on the Trans-Siberian Railway to get home from London.
Eyjafjallajökull is a relatively active volcano. The most recent major eruptions were in 920, 1612, 1782 and from 1821 to 1823. In late December 2009, many small earthquakes were recorded in the area around Eyjafjallajökull, and then in February 2010, GPS devices recorded a displacement in the local crust of 3 cm towards the south, of which movement of 1 cm occurred during a single four day period. These events were seen as evidence that magma was flowing into the magma chamber beneath the volcano, providing fuel (or rather pressure) for an imminent eruption. The main eruption began a week and a half ago, on 14th April.
While the focus of the news media this week has (understandably) been the disruption to travel and the impact on national economies, one of my key interests as a geographer was the possible impact on climate change.
When I was studying palaeoclimates and climate change as part of my geography major at university in the mid-1970s, the real concern was not global warming as it is now, but the likelihood of another ice age. The difference between the dominant fear then and contrasting fear today of global warming is probably understandable – both concerns were based on fairly simple extrapolations of (then) recent temperature trends.
Nonetheless, I remember the newspapers of the day (these were pre-internet days, remember) carrying articles about the risks and dangers of a new ice age almost every week, usually illustrated by bleak images of snow-covered wastelands in Antarctica, Iceland, or Alaska. I recall learning from my lecturer that the world had come perilously close to a new ice age following the explosive eruption of Krakatoa in Indonesia in 1883, an eruption that resulted in spectacular red sunsets for several years because of the enormous quantities of ash hurled into the atmosphere. I learned then that average temperatures around the world fell by about 1.2 degrees Celsius during the five years following Krakatoa’s eruption. It was suggested by my lecturers that if this drop had been a little more more prolonged, or if the five year drop had averaged 2 degrees Celsius rather than 1.2 degrees, a new ice age could have been triggered as the ice caps began to grow, increasing the albedo (reflectivity) of the polar areas of the earth’s surface, further cooling the surface, leading to further growth of the ice caps, and so on in a chain reaction.
The point was that a very large volcanic eruption, or a series of eruptions, could trigger a new ice age, and it was hypothesised that previous age ages had probably been caused by such eruptions during tectonically active periods. We were constantly reminded that the ‘normal’ state of the earth is an ice age – the earth has only been as warm as it is now (and was in the 1970s) for about 10% of the past quarter of a million years.
So that explains my interest in Eyjafjallajökull this week – is it likely that the eruption was large enough to reverse the recent trend of global warming? Of course, the eruption is not over yet, but present indications suggest that despite its disruptive impact on air transport, this eruption is too small to have a significant impact on global temperatures.
The concern, I guess, is that some historical eruptions in Iceland have continued for several years, causing huge losses of life and damage to property. Icelandic volcanoes can also produce large quantities of sulphur, which have caused crop failures, acid rain and toxic atmospheric conditions. None of these factors has yet emerged as significant in the current eruption of Eyjafjallajökull. However, Icelandic eruptions have also been known to trigger ‘sympathetic’ eruptions of nearby volcanoes, such as the eruption of Lakagígar in 1783 which killed a quarter of Iceland’s population, and Krafla from 1821 to 1823, during which a 90 kilometre long fissure zone emerged that is still steaming today. Indeed, the Lakigígar eruption has been linked to such diverse disasters as severe hailstorms in the United Kingdom and the freezing of the Mississippi River at New Orleans!
The net effect of volcanoes on climate change is to cause cooling rather than warming – that is, if they are large enough to have any impact at all. The equation, in extremely rough terms, is that the cooling effect of the ash produced by the volcano (the extra reflectivity of the high altitude ash cools to a greater extent than the darker colour absorbs the incoming solar radiation) is greater than the warming impact of the extra carbon dioxide produced.
This probably sounds plausible to a person who has never studied sea floor spreading, orogenesis or plate tectonics. To be fair, the earthquakes mentioned are a reasonable prediction due to isostatic readjustment, but the likelihood of a tsunami or a volcanic eruption would be very remote possibilities indeed as a consequence of melting ice, especially for a location such as Iceland that is located right upon the Mid-Atlantic Ridge. The corollary of Larry’s suggestion is that volcanic eruptions are less likely during ice ages, which is most certainly not the case.
It is fairly obvious that Larry studied journalism and not geography!
Anyway, Eyjafjallajokull now seems to have entered very different phase which is as "gentle" as the volcanoes in Hawaii. The reason that the initial ash cloud was so large was that millions of tonnes of ice that built up since last eruption in 1823 melted and collapsed into the volcano when it began erupting. When it did so, superheated steam began generating large-scale explosions that shot the ash up into the atmosphere. Fortunately, that supply of ice has now been exhausted and the explosive ash is no longer being produced.
Provided Eyjafjallajokull does not open up any new fissures beneath other nearby areas of ice, then we can assume the worst is over for the time being. However, we should not ignore the extent of local losses suffered in Iceland, which have received very little press coverage, at least here in Hong Kong. Iceland has already tried to weather a major financial crisis, and this week’s destruction of farming areas and infrastructure won’t help matters.
Paradoxically, prevailing winds kept Iceland’s major international airport at Keflavík free from Eyjafjallajokull’s ash cloud during the entire recent event. Geographical phenomena can sometimes behave perversely, can’t they!
Some galleries of Iceland (including the image of Eyjafjallajökull at the top of this blog, can be found by visiting the following links:
South-western Iceland, 2007 (48 images)
South-eastern Iceland, 2007 (30 images)
Northern Iceland, 2007 (30 images)
Iceland, all areas, 2004 (8 sub-galleries, 200 images)
Eyjafjallajökull in the summer of 2007.