It is not know how and eruption starts in Katla volcano, since no historical recordings exist when last eruption took place in the year 1918. Making ideas on how an eruption in Katla volcano start mostly guesswork. Current earthquake activity is the strongest since 1977, in 1955 there was some strong earthquake activity but magnitude of those earthquakes is not known.

http://www.jonfr.com/volcano/

I doubt 'panic grips' many Icelanders. Eruptions and earthquakes are par for the course because the Mid-Atlantic Ridge runs right through it. Toby may be fearful his holiday flight to Majorca is delayed.