Elisa Carboni, Don Grainger, Tamsin Mather, David Pyle and Gareth Thomas
As we have seen with both the Eyjafjallajökull eruption of April-May 2010, and now the Grimsvötn eruption of May 2011, explosive eruptions of Icelandic volcanoes have the potential to disrupt air traffic across Europe. This happens when explosive volcanic eruptions, which inject large quantities of volcanic ash particles into the atmosphere, coincide with meteorological conditions where winds bring that ash across the United Kingdom and other parts of Europe.
The April-May 2010 Eyjafjallajökull eruption was unusually violent (probably because of the explosive interaction between the hot molten rock and the thick ice cap on the volcano). It also erupted a relatively sticky magma (known as andesite). As a result, it produced an unusual quantity of fine to very fine ash, which was then transported across the UK at relatively low levels in the atmosphere (less than a few kilometres altitude), with well-documented consequences for aviation. The 2011 eruption of Grimsvötn was a vigorous eruption of a fluid magma (basalt, according to analyses by scientists at the Institute of Earth Sciences, University of Iceland), which produced a smaller proportion of fine ash and injected it higher into the atmosphere than the 2010 eruption. Reports from Iceland suggest that, although the eruption was also under an ice cap, there was little ice melting near the vent during the eruption.
Background information about the latest eruption:
University of Iceland, Institute of Earth Sciences
Iceland Meteorological Office
Further images available from AOPP
Tracking the plume in real-time using satellites
Researchers at the NERC funded NCEO in Oxford are using a variety of satellite instruments to track this latest Icelandic plume in near real-time.
Photographing the plume from space
Near the volcano itself satellites can actually ‘see’ the ash in the plume. In this picture taken over Iceland the volcanic plume is visible as the rusty brown smudges. The picture itself is a false colour image from the AATSR instrument of the Grimsvötn volcanic eruption in Iceland on the 22nd of May. The image covers an area of approximately 500 x 700 km and is coloured to highlight volcanic ash clouds, which appear as a rusty-brown colour. Water clouds appear white in the image, while ice-clouds, snow and glacial ice appear pale blue. The main volcanic plume is clearly visible near the centre of the image, casting a shadow toward the northwest. Wind blown ash clouds can also be seen extending to both the North and South of the volcano itself, overlying both water and ice clouds, which suggests they are at an altitude of at least a few km. This image was collected at approximate 1:30 pm BST, 22/05/2011. The Advanced Along Track Scanning Radiometer (AATSR) is a British instrument flying on board ESA's Envisat satellite. We are working to use these ‘snapshots’ of the volcanic plume to calculate key information like plume heights.
Tracking the plume from space
As the plume dilutes it can be harder to the see the ash in the visible range of light. Instead we have been using the special way that the volcanic gas sulphur dioxide (SO2) interacts with infrared radiation to track the path of the plume.
This short animation (click to animate) shows the SO2 fractional enhancement obtained from data from the IASI instrument on ESA’s MetOp satellite. This is a flag that shows anomalously high concentrations of SO2. Often SO2 and ash are injected at the same height so that several days after the eruption tracking the SO2 means tracking the ash.
However some eruptions inject ash and SO2 at different altitudes so that they subsequently follow different trajectories and we need to do more research to understand this. SO2 is clearly visible over Scotland in the morning of 24 May 2011 (see image 2011052409_11) when flights were disrupted.
Are there health implications in terms of air quality in the UK?
Our experience from last year’s Eyjafjallajökull eruption was that even in areas of the UK where ash from the eruption was deposited on the ground, there were no unusual (environmental or health) consequences: most of the ash particles were too coarse (20 – 50 microns diameter) and at too low a concentration to have any detectable impact on air quality. In fact, in most ‘dust’ samples which were collected at the time (whether on sticky tape, or on car windscreens, or at air sampling sites), most of the dust particles were not of volcanic ash at all, but a mixture of natural mineral grains and pollen grains, both of which are usually found in airborne dust.
How regular is this sort of disruption likely to be?
Since Iceland was populated in the 9th century AD, there have been about 150 eruptions that have produced significant amounts of ash (Larsen and Eiriksson, 2008). This is about one eruption every seven years, on average. For these eruptions to disrupt European air traffic the meteorological conditions must also be such as to bring the ash plume to the southeast. For example, the relatively small ash plume from the last eruption of Iceland’s most active volcano Hekla in 2000 drifted to the northeast, and had no impact at all on UK airspace.
You can help
Since eruptions which deposit ash across the UK are relatively rarely documented, there is a good deal of scientific interest in collecting information about when and where ash was observed, or collected.If a plume is predicted to come over where you live, then click here and the British Geological Survey has some tips for collecting ash samples (and where to send them afterwards), and a link to the ash fall map and questionnaire.