the_stranger
The ones to worry about are Katla and Laki, if one of them has a major eruption then all sorts of problems happen. A previous Laki eruption wiped out European crop production for several years in the 1780s and began the unrest that culminated in the French revolution. All previous eruptions of Eyjafjallajokull in the last millenium have preceded a Katla eruption by some years, with tremors being measured under Katla from 2010 onwards and continuing up to the present.