Next time a volcano threatens the air lanes, then, Dr Bennett's method may provide valuable illumination of what is happening, and thus enable airliners to steer safely through what might otherwise ground them.

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Alerted by the disruption caused to all air traffic by the Iceland volcano dust explosion in April 2010 to the power of using social media to communicate with frustrated passengers, KLM started intercepting their customers' Tweets and Facebook remarks and dreaming up little surprise, individualised gifts or events - when, at least, some of them travel.

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The Eyjafjallajokull volcano in Iceland has wreaked havoc on European air travel.

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As we all know, a volcano eruption over Iceland last week and has disrupted trans-Atlantic air travel.

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After "eruptive activity" last year at the Cleveland volcano, University of Alaska Fairbanks scientist Steve McNutt noted that 90% of air freight from Asia to Europe and North America flies over Alaska airspace, and hundreds of flights fly through Anchorage's air space daily.

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The explosions which rocked the Soufriere hills volcano sent ash up to 12, 200 metres (40, 000 feet) into the air.

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Numerous helicopter companies (most based in Lihu'e) offer up-in-the-air jaunts over waterfall-striped Mt Wai'ale'ale, the island's central shield volcano and one of the wettest spots on Earth, and the sheer-hewn sea cliffs of the Na Pali coast, accessible otherwise only by ocean kayak.

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In 1958, he found the concentration at the top of the volcano to be around 315ppm (that is 315 molecules of CO2 for every one million molecules in the air).

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