BBC News – The eruption that changed Iceland forever.
Why the Icelandic volcano eruption could herald more dirsuption – Times Online.
Volcanic eruptions created Iceland and in 1763 almost destroyed it. But in 1816, another volcano, half way round the world in Indonesia, caused widespread weather change, dropping temperatures in Western Europe and Eastern North America. Not much, just an average of a degree or two, but enough to cause widespread crop failures and famine. Eastern U.S. farmers moved West; German farmers immigrated; as did the Irish. Mary Shelley, housebound by the miserable Swiss weather, wrote Frankenstein.
A foot of snow fell in Quebec in July of that year. A contemporary account is available at the following website.
It was called the year that summer never came. Events in many countries are detailed in a Wikipedia article: