June 8, 1783

Laki

The Skaftá Fires fissure eruption begins in Iceland

The famous eruption did not come out of Laki mountain. A 27-kilometre chain of vents eventually formed across both sides of the older ridge.

8 June 1783, on a short fissure

On 8 June 1783 a brief explosive eruption opened on a short fissure in southern Iceland, and lava began pouring into the Skaftá River gorge before the day was out.

Basaltic magma had propagated through the Grímsvötn fissure swarm. Interaction with shallow groundwater produced the explosive opening phase, after which fire-fountaining and rapid lava effusion developed.

Four days later the lava had travelled 35 kilometres to the lowlands.

Eight months, 14.7 cubic kilometres

This was the first episode of the Lakagígar or Skaftá Fires eruption, which ran to 7 February 1784 and propagated northeastward along the fissure system. The completed vent complex reached 27 km.

It produced 14.7 ± 1.0 km³ of lava and released an estimated 122 megatons of sulfur dioxide. The familiar name "Laki eruption" comes from an older mountain crossed by the vent complex, not from a single cone erupting.

What actually killed people

Modern analysis finds no evidence that lava, tephra or comparable immediate hazards directly killed anyone on the opening day. Livestock in nearby parishes began dying within roughly two weeks; the famine and peak human mortality came later.

Iceland's population fell from 49,609 at the beginning of 1783 to 40,381 at the beginning of 1786 — a decline of about 19 per cent from excess deaths and reduced births, with roughly 8,000 excess deaths estimated in 1784–1785.

Studies identify excess mortality coinciding with the haze elsewhere in Europe, including an estimated 11,500 excess English deaths in August–September 1783 and 8,200 in January–February 1784. Attribution is contested, and a 2024 review concludes that the evidence for substantial direct haze-caused mortality is weak.

Sources

Researched 24 Aug 2026 6 sources not yet audited

How this was checked

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What the sources leave uncertain

The 8 June onset of the Lakagígar fissure eruption is secure, although separate activity at Grímsvötn's central volcano may have begun in May.
The listed claim that as much as 33% of Iceland's population died is not supported by the strongest recent demographic study, which finds an almost 20% population decline and about 8,000 excess deaths in 1784–1785.
Studies identify excess mortality coincident with the haze in parts of Europe—for example, an estimated 11,500 excess English deaths in August–September 1783 and 8,200 in January–February 1784—but coincidence and attribution are contested. A 2024 review concludes that evidence for substantial direct haze-caused mortality is weak.
Regional weather and famine effects outside Iceland can generally be attributed only probabilistically, not as a simple count of people definitively killed by the eruption.