Laki Volcano Erupts in Iceland

Context

In the late eighteenth century Iceland functioned as a remote Danish dependency whose economy centered on sheep and cattle herding plus coastal fishing. The island’s thin soils and short growing season left its roughly fifty thousand inhabitants highly vulnerable to any disruption in pasture or hay production. The Laki fissure formed part of the larger Grímsvötn volcanic system, which had produced earlier fissure eruptions and remained seismically active beneath the Vatnajökull ice cap.

What Happened

On 8 June 1783 a 25-kilometre chain of vents opened southwest of the Laki mountain, beginning with phreatomagmatic explosions where groundwater met rising basalt. Within days the style shifted to sustained fire-fountaining and lava effusion that poured down the Skaftá river gorge and reached the coastal lowlands four days later. Ten separate eruptive pulses followed over the next eight months, each typically starting with brief explosive activity before transitioning to Hawaiian-style fountains; neighboring Grímsvötn also erupted repeatedly between 1783 and 1785.

Aftermath

Roughly half of Iceland’s livestock perished from fluorine poisoning after grazing on contaminated grass, triggering a famine that killed an estimated one-fifth of the human population. A sulfur-dioxide aerosol cloud drifted southeast, producing a thick, choking haze that reached mainland Europe by mid-June and persisted into the autumn; contemporary accounts record respiratory distress, failed harvests, and unusually hot summer weather followed by an exceptionally severe winter.

Legacy

The Laki event remains one of the largest historic basaltic fissure eruptions and demonstrated how Icelandic volcanism can generate hemispheric climatic and agricultural crises. Its contribution to the string of poor harvests and social stress in France during the 1780s has been cited by historians as one factor among several that heightened rural discontent before the Revolution of 1789.