On This Day: the Laki eruption begins, 1783

On 8 June 1783 a fissure eruption began across the flanks of the Laki volcanic mountain ridge in south-eastern Iceland. The Laki (or Lakagígar) eruption lasted until 8 February 1784: approximately 27 km of fissures ultimately opened, and 14.7 cubic kilometres of lava were erupted. This was a huge volume of material, but the lava did not itself directly cause any deaths. Much more deadly were the gas emissions (PDF) produced by the eruption. The Laki eruption released vast quantities of gas into the atmosphere: the majority was water vapour, but an estimated 10% is thought to have been composed of carbon dioxide, sulphur dioxide, hydrogen chloride and fluorine. A dry fog hung over Iceland, the North Atlantic and parts of adjacent land masses for weeks. The 50 million tonnes of sulphur dioxide combined with atmospheric water vapour to form sulphuric acid aerosols, and the resulting acid rain poisoned the soil and destroyed the grazing upon which Iceland’s livestock depended. Animals died in their tens of thousands, and the people followed: by the end of 1785 over 10,000 people had died, perhaps one-fifth of Iceland’s population, 9 out of 10 from famine. Nor were the effects limited to Iceland: the acidic haze erupted from Laki spread to Britain, Ireland and continental Europe, bringing fogs, acid rain, violently disturbed weather patterns and unseasonable temperatures, leading to damaged vegetation, failed harvests, hunger and poverty (in these circumstances, the French Revolution was inevitable). Beyond Europe, populations as far afield as North America, Egypt and Japan may have suffered the meteorological and economic consequences of the seven-month Laki eruption.

UPDATE. More on Laki 1783 from the fascinating History of Geology blog: 8 June 1783: the Laki eruptions.