Laki: A Deep Dive into the Eruption That Changed History
In the summer of 1783, the earth split open in the highlands of southern Iceland along a chain of fissures known as Laki, or Lakagigar. Over the following eight months, this rift poured out an enormous volume of lava and released vast clouds of toxic gas. The eruption killed a fifth of Iceland's population through famine, poisoned the land, and altered weather across Europe and beyond. Laki is a sobering demonstration that an eruption need not be explosive to be among the deadliest in human history.
A row of craters, not a single peak
Laki is not a conventional volcano but a fissure system: a line of more than a hundred craters stretching roughly 25 kilometres across the Icelandic highlands. The fissure is part of the larger Grimsvotn volcanic system, fed by the same forces that split Iceland along the Mid-Atlantic Ridge. When it erupted in 1783-1784, lava welled up along the entire length of the rift, building a chain of spatter and cinder cones still visible today as a haunting row of green-mantled craters.
The scale of the lava flows
The Laki eruption produced one of the largest lava flows of the last thousand years, covering an area of around 600 square kilometres with basaltic lava. The volume erupted was immense, filling river valleys and reshaping the landscape of the region. Yet it was not the lava that caused the greatest harm — it was the gas that came with it.
The poisonous haze
As the fissure erupted, it released enormous quantities of sulphur dioxide and fluorine. The sulphur reacted in the atmosphere to form a persistent acidic haze, known in Iceland as the Haze Famine, that hung over the country and drifted across Europe. Fluorine settled on grass and was taken up by grazing animals, causing a disease that killed much of Iceland's livestock — sheep, cattle, and horses died in enormous numbers.
The Haze Famine
With their animals dead and crops failing under the toxic haze, the people of Iceland faced catastrophe. An estimated quarter of the nation's livestock and roughly a fifth of its human population perished in the famine that followed. It was one of the greatest disasters in Icelandic history, and at one point there was even discussion of evacuating the surviving population from the island entirely.
A continental and global reach
The effects of Laki extended far beyond Iceland. The sulphurous haze spread across Europe during the summer of 1783, blurring the sun and damaging crops. Reports from across the continent describe a strange dry fog, oppressive heat followed by harsh cold, and unusual weather. The eruption is thought to have contributed to a severe winter and to hardship in many countries, with some historians linking the disruption to social unrest in the years that followed.
Why effusive eruptions can be so deadly
Laki overturns the common assumption that the most dangerous volcanoes are the explosive ones. Its activity was largely effusive, producing lava rather than towering ash columns, yet it released gases on a scale that proved lethal across a continent. This makes Laki a key reference point for understanding the climatic and atmospheric hazards of large basaltic fissure eruptions, a class of event that remains a serious concern for Iceland and the wider world.
A landscape of memory
Today the Lakagigar fissure lies within Vatnajokull National Park, its craters cloaked in thick moss and its lava fields slowly returning to life. It is a place of stark beauty and deep historical resonance, where visitors can walk among the vents that, two and a half centuries ago, set in motion one of the most far-reaching natural disasters of the modern era.
Explore on the map
Laki belongs to a remarkable family of Icelandic fissure systems, alongside Grimsvotn, Bardarbunga, and the recent eruptions of the Reykjanes Peninsula. Explore it on the interactive map — filter by country to see Laki among Iceland's volcanoes and to grasp how the splitting of the island can unleash eruptions of continental consequence.