File:Dust Cloud - Composite Map Image.jpg

English: Do also view large for clearer detail...

All aircraft over Britain and much of north western Europe were grounded on Thursday 15th April 2010 following fears that volcanic dust from an eruption under Eyjafjallajökull / Eyjafjalla glacier in Iceland could damage jet engines. There was a risk that silica dust could melt and and re-condense as a glass inside the engines, causing blockage and engine failure. Two previous related incidents involving this type of failure were KLM Flight 867 and the Jakarta British Airways Flight 9 incident. (The ICAO recorded 89 incidents involving volcanic ash and some kind of damage to aircraft between 1953 and 2008.)

The safety threat is presumably related to the density, size, composition and altitude/duration of exposure to the particles - and in anticipation that the problem could be long term, research was done to quantify the risks more accurately. Obvious conflicts arose between interested commercial parties as to the need for a zero tolerance approach to the ash. A week later most routes were re-opened, with a higher "safe" threshold set at 0.002g of ash in each cubic metre of air, (still approximately a not insubstantial 8kg / 17lb an hour for a 92" diameter fan at 550mph). The previous "zero" threshold limit was 0.000 1g of ash per cubic meter. One blogger suggested all this was "making it up as they go along".

On the 4th May 2010 there were further limited airspace closures above Scotland and Ireland.

EU Airlines are legally obliged to provide "board and lodging" for customers stranded away from home. Some large airline bosses vigorously complained that the restrictions were too strict, but none provided a shred of scientific evidence to support their case. [Update: 26th April 2011 News Article: "Air traffic controllers were right to close European airspace..."]

On 18th May 2010 the "no fly" level for ash was further relaxed from 0.002g to 0.004g for "limited flights" (about 15kg / 32lbs an hour per engine with a 92" fan). A UK CAA spokesman said the amount of time a plane can safely fly in the new ash limit will be determined by individual airlines' engine manufacturers.

This is a composite map image, combining air pressure, flight tracking, satellite cloud and dust image, topographic and geologic data. Various sources with differing map projections have been approximately aligned.

Sea level Air Pressure Isobar data (in millibars) is from the Met Office, showing a North Atlantic high pressure area bringing a brown dust stream (in contrast to the white condensed water vapour clouds) clockwise across and then down into Scandinavia, Scotland and the rest of Britain. Note that sea level pressures do not always accurately indicate wind directions at the higher altitudes, the location where heat (and the explosive "atomising" effect of steam from the melting glacier ice interacting with the lava) has lifted the volcanic dust plumes, and at which height jetliners most efficiently cruise. Generally, however, wind flows roughly parallel to isobars, away from high pressure, and - in the northern hemisphere - clockwise around high pressure areas. More typical wind patterns might have taken the dust northeastwards, to disperse less disruptively over the arctic.

Volcanic activity is unpredictable - the last big Eyjafjallajökull area eruption in 1821 lasted over a year. Iceland is located over the northern end of the Mid-Atlantic Ridge, a divergent tectonic plate boundary. The North American and Eurasian plates are slowly moving apart, with new rock being formed from lava rising beneath the earth's crust. Sometimes this liquid lava reaches the surface before solidifying. The approximate locations of plate boundaries in the vicinity of Iceland (as decribed by W. J. Kious, R.I. Tilling, M. Kiger, J. Russell, USGS) are shown in orange. Property owners - making the argument for the long term "inflation proofness" of their investments - sometimes like to say that "Land is one of the things that God stopped making more of". Not so in Iceland, although - to be fair - He probably subcontracts the production locally to the Huldufólk. Radio bandwidth is another thing that "God stopped making more of", incidentally, an issue at the heart of many an FCC squabble, but that's another story...

The satellite imagery is from the European Space Agency (ESA) Envisat Satellite.

Aircraft data is from the specialist European flight tracking website www.flightradar24.com/, (a clever mashup including maps powered by Google) taken at about 6pm BST. The suddenly overburdened flightradar24 website wittily renamed itself "We said cash, not ash!" after an Icelandic joke. Alone among western democracies, the Icelandic people were foolishly invited by their government to choose whether or not they felt like bailing out their banks. Much to everyone's surprise, they politely declined. In retaliation, UK and Dutch investors now eat frozen Pacific Cod Fish Fingers and make snide comments about Icelandic horses being ponies, really, all of which has the icelandic people quaking in their boots...

The yellow aircraft indicate live positions of planes still in flight at that time, reported by ADS-B transponders fitted onboard. The small blue crosses are major airports.

Eerily, there were no recorded flights at all in Ireland, the UK, Holland, Denmark, Norway and Sweden. France, Spain, Germany and Poland were to quickly follow suit. Typically, half a million air passengers a day would usually pass through UK airspace.

The eruptions caused severe local disruption with flooding from melting glaciers and exhausted farmers needing to protect horse and sheep livestock from grazing land contaminated with toxic ash (which has a very high fluoride content causing acidic stomach and intestinal hemorrhaging in the animals). Limitations on fresh fish exports - normally done by air freight - also damaged the fishing industry. Frozen fish - the alternative contingency to speedy export to market - commands only half the price (from the perspective of the fishermen - although, of course, supermarket consumers pay more... ).

Related links: Iceland Review_Online article and video about a local Eruption Exhibition one year on. Met Office Images ESA Observing Earth Image NASA/MODIS Rapid Response Team Images ESA Animation of Cloud Spread (Using volcanic Sulphur Dioxide - SO₂ - as a tracer) London Volcanic Ash Advisory Centre UK laser cloud base recorders (CBR) readings and 18 hour prediction animation List of global Volcanic Ash Advisory Centres Webcam: Eyjafjallajökull - Múlakot with thanks to jonfr500[at]simnet.is

(UK) NATS National Air Traffic Services