Laki Eruption

The Laki eruption of 1783 to 1784 was one of the most destructive volcanic events in recorded history. A long fissure in southern Iceland spewed lava and enormous quantities of gas for about eight months, killing a large share of the island's livestock and causing a famine that took roughly a fifth of its human population. Its fumes and haze drifted across Europe, and the event is widely studied as a case of how a single eruption can reach far beyond its source.

Iceland sits on the Mid-Atlantic Ridge, where tectonic plates pull apart, and its volcanic systems are active and varied. Laki is not a single mountain but a line of about 130 craters along a fissure of roughly 25 kilometers, near the Grímsvötn volcanic system and the Skaftá River. In the late eighteenth century Iceland was a poor dependency of the Danish crown, its farmers living on sheep, cattle, horses and fishing, with little margin against bad years.

The eruption began in June 1783, preceded by earthquakes, and continued into early 1784. It was an effusive fissure eruption rather than a single explosive blast, producing a vast lava flow, among the largest in historic times, along with fountains of lava and ash. The greater danger was gas. Fluorine and sulfur dioxide settled on pastures and poisoned grazing animals, which suffered bone deformities and died in great numbers. Icelanders later called the ensuing hardship the Móðuharðindin, the "Mist Hardships." Estimates vary, but most historians agree that a majority of the livestock perished and that around 20 percent of the population died of hunger and disease.

The effects spread far beyond Iceland. A dry, sulfurous haze hung over much of Europe in the summer of 1783, reducing visibility and turning the sun reddish. Contemporary accounts from Britain, France and elsewhere describe respiratory problems and withered vegetation, and researchers have linked unusually high mortality in parts of England and elsewhere to air pollution from the eruption. The following winter was severe across much of Europe and North America, and Benjamin Franklin, then in France, suggested that the haze might have played a role in the cold.

The eruption's wider consequences are debated. Some historians have proposed that crop failures and hardship helped create the tensions that preceded the French Revolution in 1789, though weather, politics and finance all played parts, and the link is far from proven. Laki's clearer legacy lies in Iceland, where it prompted discussion of whether the population should be relocated, and in modern science, where it serves as a benchmark for assessing the risk of a future large Icelandic fissure eruption in a densely populated, air-traveling world.