{"id":1130,"date":"2014-02-12T10:33:53","date_gmt":"2014-02-12T10:33:53","guid":{"rendered":"http:\/\/all-geo.org\/volcan01010\/?p=1130"},"modified":"2014-02-12T11:33:17","modified_gmt":"2014-02-12T11:33:17","slug":"a-history-of-ash-clouds-and-aviation","status":"publish","type":"post","link":"https:\/\/all-geo.org\/volcan01010\/2014\/02\/a-history-of-ash-clouds-and-aviation\/","title":{"rendered":"A history of ash clouds and aviation"},"content":{"rendered":"

During 2010’s Eyjafjallaj\u00f6kull eruption, as the planes stood on the tarmac, many people asked why this hadn’t happened before.\u00a0 After all, Iceland’s volcanoes have been active since long before mankind took to the skies.\u00a0 Well, there are three main reasons for this.\u00a0 These are the volcanoes, the airline industry and flight safety regulations.\u00a0 This post looks at how all three have changed since the Second World War.<\/p>\n

The volcanoes<\/h2>\n

The orange areas in the barcode-like diagram below show all the periods in which volcanoes in Iceland were erupting.\u00a0 The data came from the Global Volcanism Program<\/a>.\u00a0 It’s a fairly regular occurrence, as you can see.\u00a0 On average, as I explained in my first ever volcan01010 blog post<\/a>, there is an eruption in Iceland about every 5 years, with 3\/4 of them being explosive.\u00a0 The wind blows towards the UK about 1\/3 of the time, so you could expect a direct hit from an ash cloud about once every 20 years.<\/p>\n

The Surtsey and Krafla Fires eruptions stand out for their long duration.\u00a0 Surtsey, in particular, is interesting because the eruption produced a new island in the north Atlantic, with ash-rich explosions driven by hot magma boiling the water<\/a> of the ocean.\u00a0 It lasted three and a half years.\u00a0 What would happen if a similar eruption began now?<\/p>\n

I’ve marked the three most powerful explosive eruptions, Hekla 1947, Eyjafjallaj\u00f6kull 2010 and Gr\u00edmsv\u00f6tn 2011, with bold lines.\u00a0 These produced much more ash than the others.\u00a0 It is pure luck that there was such a long gap between them.<\/p>\n

\"Air_traffic_vs_eruptions_01\"<\/p>\n

The airline industry<\/h2>\n

\"Air_traffic_vs_eruptions_02\"<\/p>\n

The blue line shows the huge growth in the global airline industry over the past 70 years (averaging 5% per annum<\/a>).\u00a0 There were no transatlantic passenger flights at the time of Hekla 1947.\u00a0 By 2010, there were 2.5 million<\/em> passengers flying between London Heathrow and New York JFK per year<\/em>.\u00a0 The more planes that are flying around, the more chance there is that one will meet an ash cloud.\u00a0 In the two most dramatic encounters (BA Flight 9 vs<\/em> Galunggung, Indonesia and KLM Flight 867 vs<\/em> Mt Redoubt, Alaska, USA) the ash caused the jet engines to fail.\u00a0 This led to changes to flight rules described below.<\/p>\n

An important point to note is that as society becomes more dependent on air transport, any disruption is going to be increasingly expensive.<\/p>\n

Flight safety regulations<\/h2>\n

The near-miss ash cloud encounters led to the establishment of the International Airways Volcano Watch in 1987, and the process of designating regional meteorological\u00a0 agencies as Volcanic Ash Advisory Centres (VAACs<\/a>) began in 1990.\u00a0 With no proper measurements of how much ash was safe to fly through, the guidance was to ‘avoid all ash’.\u00a0 The final graph shows the period when these rules were in effect.<\/p>\n

In much of the world, where planes can just divert around dangerous areas, the guidance worked well.\u00a0 But when Eyjafjallaj\u00f6kull dispersed ash across much of NW Europe in 2010, closing the airspace of entire countries, it led to 95,000 cancelled flights and the massive global disruption that made the volcano infamous.<\/p>\n

\"Air_traffic_vs_eruptions_03\"<\/p>\n

The Eyjafjallaj\u00f6kull eruption was the most ash-rich explosive eruption in Iceland since the rules were put in place, but it wasn’t the first time that Icelandic eruptions had affected flights.\u00a0 The Hekla 2000 eruption damaged a NASA DC-8 aircraft that accidentally flew through the plume, and the Gr\u00edmsv\u00f6tn 2004 eruption caused parts of Scandinavian airspace to be closed.\u00a0 In fact, every Icelandic eruption of the 21st century has impacted aviation.<\/p>\n

During the Eyjafjallaj\u00f6kull crisis, the aviation rules were relaxed and ash contamination was divided into different concentration zones (even though we can’t reliably map the difference between them<\/a>).\u00a0 In Europe, planes can now fly where up to 4000 micrograms of ash per cubic metre of atmosphere are predicted and this got things moving again in 2010 while the eruption was ongoing (yellow region on graph).\u00a0 It is also a big reason why only 900 flights were cancelled during the 2011 Gr\u00edmsv\u00f6tn eruption, despite the fact that it erupted twice as much material in one tenth of the time<\/a>.\u00a0 With these new rules, it seems likely that only the largest eruptions could cause disruption on the the scale of Eyjafjallaj\u00f6kull.<\/p>\n

Looking to the future<\/h2>\n

The chaos caused by the Eyjafjallaj\u00f6kull eruption was unprecedented because the global airline industry ‘took off’ and became part major of society during a lucky gap between powerful explosive eruptions in Iceland.\u00a0 We can’t predict the next 70 years, but the following trends are likely:<\/p>\n