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The NASA Earth Observatory has taken some stunning high resolution images of an eruption from the Puyehue-Cordón Caulle Complex in Chile that consists of four different volcanoes. Ash plumes have reached two to four kilometers in altitude and have drifted 90 to 320 kilometers downwind affecting surrounding areas including forests, farmlands and resorts.
I was thinking the other day about the eruption of Eyjafjallajökull in Iceland, and wondering what the actual levels of ashfall in the UK had been. This was prompted in part by the 30th anniversary of the eruption of Mt St Helens, in the northwestern USA, on 18 May 1980, and my childhood memories of walking through piles of ash and scooping it into jam jars (we lived in Washington state at the time); and also by a question that we received at IHRR about the health effects, if any, of Icelandic ash. After the current eruption began on 14 April, my sons and I put pans out in the back garden to catch any Icelandic ash that fell, and they were disappointed to find only leaves and dead bugs. But there have been a few reports of ashfall at ground level, and I wondered what the concentrations had been.
I should say at this point that I am not doing any research on the health effects of the Iceland ash plume – so what follows is no more than the musings of an interested citizen. I spent some time looking around on the web, and came across the UK Air Quality Archive, which has several good summaries of ground measurements taken during different phases of the eruption:
What those data show pretty convincingly is that the increase in levels of particulate air pollution measured by ground stations (typically expressed as the concentration of particles that are less than 10 microns across – known as PM10) has been nil to minimal, even at times when the plume has been observed over the UK. Any increase – for example, that seen in Northern Ireland on 4 May – is still within the typical daily noise. Read more
The volcanic ash cloud that appeared over Europe during the middle of April, and which has made a partial return recently, brings into sharp focus the expectations that we as societies have of both experts and expert knowledge. Is it too much to ask that the meteorological authorities can’t provide real-time dynamic concentrations of ash at all altitudes relevant to aircraft? Shouldn’t the aircraft manufacturers know just how much ash will cause their engines to malfunction? Can’t the authorities responsible for regulating use of airspace, and by implication air safety, understand the trade-off, the ‘proportionate response’ that they are being asked for in trading off the risks to people and property against the economic and other consequences of closing airports? When I look at each of these questions I find myself with troubling doubts, not over whether or not the answers to them imply that it is or was safe to fly, but over, quite simply, the assumption that we make regarding the knowability of the world in which we live.
On the one hand, the ash cloud has become an emblematic reminder of just how geographically-globalised our lives have become, as we found our families stuck in faraway places and as the stock of fresh food in our supermarket shelves shifted away from airborne travel. But on the other it reminds us that the benefits of geographical-globalisation are associated with new sorts of risk, ever-present but rarely manifest, that follow from the same technologies that underpin globalisation. When risks like these make themselves felt our natural assumption is to expect that experts are there to provide the answers that we need in order to live with them. The ash cloud created a profound sense of helplessness when such expertise was found to be not forthcoming, when we discovered that experts didn’t know what the safe concentrations of ash were, that forecasters could not produce reliable sub-hourly maps of where it was safe to fly and that decision makers could not easily trade-off the economic consequences of closing air space against the risks of catastrophic engine failure. Read more