The eruption of Laki (1783)

Laki or more correct Lakagígar (Craters of Laki) is a volcanic fissure in the south of Iceland. On 8 June 1783, a fissure with 130 craters opened with earthquakes and explosions when groundwater interacted with the rising basalt magma. The eight-month emission of sulfuric aerosols resulted in one of the most dramatic climatic and societal events in historic times[1].

The eruption produced huge amounts of basalt and tephra. Gases were climbing to altitudes of about 15 km. These gasses, including millions of tons of hydrogen fluoride and sulfur dioxide, gave rise to what has since become known as the 'Laki haze' across Europe.

For two years following the initial explosions, Europe, North America and north Africa experienced bizarre weather phenomena. Within days, the haze produced by ash and smoke from Laki turned the sun blood red across Iceland. By June 10, ash was falling in Norway that withered tree leaves and grass in Bergen on the southwestern coast. That same day, in Denmark black ash discolored the sails and decks of ships as they approached the harbor.

Meanwhile, the haze – also referred to as 'dry fog' – spread swiftly across Europe. It arrived in Prague on June 16. On the 17th, the sun turned blood red in Berlin and on June 18, the haze appeared in Lyon, France:

“The fog was cold and humid, with the wind coming from the south and one could with eye look at the sun with a telescope without a blackened lens. The fog was such as the oldest men here have not seen before…”

That same day the haze covered Padua, Italy. Clearly, it was quite different from the ordinary fog the locals were used to. They wrote that it smelled of sulfur and that it withered the grass. In England, on June 23, a clergyman in Hampshire noted that the vegetation was yellow and looked “as if scorched with frost.” All of this makes it clear that the fog carried with it sulfur dioxide from Laki’s eruption.

By the end of June, the haze covered virtually all of Europe. In St. Petersburg, people recorded the dry fog on June 26. By June 30, it had reached Moscow. In central Asia, visitors reported unseasonable frosts throughout the summer as the haze kept the sun from warming the earth.

North Africans were also taking notice of the odd “cloud.” By the end of June it arrived in Tripoli, then in Syria. By July, the haze extended into Baghdad and the Altai Mountains.

In Egypt, it was noticed that the summer of 1783 was radically different from most summers in Egypt. Every spring the Nile River flooded, leaving behind wet, fertile soil in which the Egyptians grew their crops. However, that year the inundation was not sufficient. With no flood, the crops failed, with drastic consequences for the Egyptians.

The bizarre weather patterns triggered by Laki’s explosion meant that the monsoon that year was abnormally weak. In turn, this led to a severe droughts in India and Egypt. As a result of that drought, the Nile didn’t flood.

Egypt, so distant from Iceland, suffered the largest number of deaths in the wake of Laki’s eruption. Historians estimate that the population of Egypt was reduced by one sixth in the resulting famine.

The effects of the eruption lingered across North America and Europe as well. Parish records in England show a large increase in the number of deaths in July and August of 1783, presumably from respiratory illnesses caused by the haze.

In North America, the winter following the eruption was extremely cold and very long. The harbour in Charleston, North Carolina froze so hard that men and women could skate across it. In February 1784, ice floated down the Mississippi River to New Orleans and out into the Gulf of Mexico where it lingered, not melting.

In Iceland, a disease that caused the skin and flesh to rot off the living animals as they grazed in the fields. The symptoms were those of chronic fluorosis: the grazing livestock were poisoned because they ate vegetation that had been contaminated with fluorine as a result of the volcanic fallout.

Within days, the animals most severely affected were dead. Within a few months over 60% of all livestock in Iceland died, leaving the Icelanders to face the winter of 1783-84 without a proper food supply. The ongoing eruption, the colder than usual summer and the fallout of ash and poisonous haze meant that few if any crops could be saved. As a result, between 1783 and 1786 approximately 20% of the population of Iceland died of starvation and disease. This period is known in Icelandic as moðuharðindin, the 'Mist Hardships'.

[1] Thordarson and Self: Atmospheric and environmental effects of the 1783–1784 Laki eruption: A review and reassessment in Journal of Geophysical Research - 2003