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🌋 Laki, 1783: how an eruption became a famine

The lava took 42 farms — 0.8 percent of the farms in Iceland. It was the gas that emptied the country. Eight million tonnes of fluorine settled on grass that still looked exactly like grass, and more than 60 percent of Iceland's grazing ani

5
lessons
~20 min
to learn
Adults
level
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What you’ll learn

  1. A Fissure Opens Across IcelandDescribe the shape of the Laki eruption — a 27-kilometre fissure erupting in ten episodes over eight months — and why that shape mattered more than its size.Laki was a line, not a cone. The lava took 42 farms; the gas and ash it kept feeding into the jet stream reached almost everyone else.
  2. Poison Moves Through a Food SystemTrace the route from fluorine-bearing ash to a collapsed food supply, and separate what the evidence says about animals from what it says about people.Invisible fluorine on green pasture halved the milk, then killed more than 60 percent of the herds — but the human deaths were hunger and disease, not fluorosis.
  3. Europe Receives the HazeExplain how the haze reached Europe in about ten days, and judge which of 1783–84's weather extremes can and cannot be attributed to the eruption.The haze crossed to the continent in ten days. The hot July was probably ordinary blocking; the cold winter carries the eruption's fingerprint.
  4. The Winter That Did the KillingUse Iceland's parish registers to locate when people actually died, and identify what stood between the eruption and the famine.The death rate in 1783 was completely normal. The dying came in 1784 and 1785, and 1785 was the worst year of all.
  5. What Laki Teaches About DisasterSeparate a physical hazard from the conditions that turn it into a catastrophe, and identify which parts of an outcome remain open to choice.Change what people depend on, and how fast help moves, and the same eruption produces a different death toll.

Questions this course answers

What made Laki different from an eruption at a single cone?

The fissure ran about 27 km and erupted in ten episodes between June 1783 and February 1784, each starting with an explosive phase that put gas up to 9–13 km.

Why could a green, standing pasture still kill the animals grazing it?

About 8 Mt of fluorine came down on roughly 200,000 km². Grass above about 250 ppm of fluorine kills grazing livestock within days, and the contamination is not visible.

Why did the loss of livestock translate so directly into human starvation?

Milk yields halved as soon as the haze arrived, before the animals died; then more than 60 percent of the grazing stock was lost within a year. The same animals were the food, the fertiliser and the means of getting anywhere.

What does the 2019 modelling say about Europe's exceptionally hot July of 1783?

Zambri and colleagues could not reproduce the heatwave from the eruption; their model produces it from a blocking high over northern Europe that occurs with or without a volcano. The cold winter that followed is a separate case, where the eruption's fingerprint is clearer.

Fill in what the parish registers actually show.

1,227 people died in 1783 — 2.5 percent, the ordinary rate for the period. The famine deaths came in 1784 (10.9 percent) and 1785 (12.4 percent), after the eruption had ended.

Put Laki's chain of consequences into the order the evidence supports.

Each step is a loss that removes the means of surviving the next one. That is why the worst year came after the eruption had already stopped.

Grounded in trusted sources

  • Atmospheric and environmental effects of the 1783–1784 Laki eruption: A review and reassessment — Thordarson & Self, Journal of Geophysical Research 108(D1), 4011, 2003 — https://doi.org/10.1029/2001JD002042
  • ‘More poison than words can describe’: what did people die of after the 1783 Laki eruption in Iceland? — Wieners & Hálfdanarson, Natural Hazards and Earth System Sciences 24, 2971–2994, 2024 — https://nhess.copernicus.org/articles/24/2971/2024/
  • Modeling the 1783–1784 Laki Eruption in Iceland: 2. Climate Impacts — Zambri, Robock, Mills & Schmidt, Journal of Geophysical Research: Atmospheres 124, 6770–6790, 2019 — https://doi.org/10.1029/2018JD029554
  • Haze, Hunger, Hesitation: Disaster aid after the 1783 Laki eruption — Claudia E. Wieners, Journal of Volcanology and Geothermal Research 406, 107080, 2020 — https://doi.org/10.1016/j.jvolgeores.2020.107080
  • The Laki (Skaftár Fires) and Grímsvötn eruptions in 1783–1785 — Thordarson & Self, Bulletin of Volcanology 55, 233–263, 1993 — https://doi.org/10.1007/BF00624353
  • Grímsvötn (volcano number 373010), including the 27-km-long Laki fissures — Smithsonian Institution Global Volcanism Program — https://volcano.si.edu/volcano.cfm?vn=373010
  • Fires of the Earth: The Laki Eruption 1783–1784 — Jón Steingrímsson, written 1788, translated by Keneva Kunz, University of Iceland Press, 1998 — the eyewitness journal both modern studies above draw on
  • Volcanoes Can Affect Climate — United States Geological Survey, Volcano Hazards Program — https://www.usgs.gov/programs/VHP/volcanoes-can-affect-climate

Every Wunder lesson is built from real, reputable sources — never invented.

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