Laki or Lakagígar (Craters of Laki) is a volcanic fissure situated in the south of Iceland. The system erupted over an 8 month period during 1783-1784 from the Laki fissure and the adjoining Grímsvötn volcano, pouring out an estimated 14 km3 (3.4 cu mi) of basalt lava and clouds of poisonous hydrofluoric acid/ Sulphur Dioxide compounds that killed over 50% of Iceland’s livestock population, leading to famine which killed approximately 25% of the population.
The Laki eruption and its aftermath has been estimated to have killed over six million people globally, making it the deadliest volcanic eruption in historical times. The drop in temperatures, due to the sulphuric dioxide gases spewed into the northern hemisphere, caused crop failures in Europe, droughts in India, and Japan’s worst famine.
Consequences in Iceland
The consequences for Iceland—known as the Mist Hardships—were catastrophic. An estimated 20-25% of the population died in the famine and fluorine poisoning after the fissure eruptions ceased. Around 80% of sheep, 50% of cattle and 50% of horses died because of dental and skeletal fluorosis from the 8 million tons of hydrogen fluoride that were released.
The parish priest and dean of Vestur-Skaftafellssýsla, Jón Steingrímsson (1728–1791), grew famous because of his eldmessa (“fire sermon”) which he delivered on July 20, 1783. The people of the small settlement of Kirkjubæjarklaustur were worshipping while the village was endangered by a lava stream, which ceased to flow not far from town, with the townsfolk still in church.
“This past week, and the two prior to it, more poison fell from the sky than words can describe: ash, volcanic hairs, rain full of sulphur and saltpeter, all of it mixed with sand. The snouts, nostrils, and feet of livestock grazing or walking on the grass turned bright yellow and raw. All water went tepid and light blue in color and gravel slides turned gray. All the earth’s plants burned, withered and turned gray, one after another, as the fire increased and neared the settlements.”
Consequences in Europe
An estimated 120,000,000 long tons (120,000,000 t) of sulphur dioxide was emitted, about three times the total annual European industrial output in 2006, and equivalent to a 1991 Mount Pinatubo eruption every three days. This outpouring of sulphur dioxide during unusual weather conditions caused a thick haze to spread across western Europe, resulting in many thousands of deaths throughout 1783 and the winter of 1784.
The summer of 1783 was the hottest on record and a rare high pressure zone over Iceland caused the winds to blow to the south-east. The poisonous cloud drifted to Bergen in Denmark-Norway, then spread to Prague in the Kingdom of Bohemia (now in the Czech Republic) by 17 June, Berlin by 18 June, Paris by 20 June, Le Havre by 22 June, and to Great Britain by 23 June. The fog was so thick that boats stayed in port, unable to navigate, and the sun was described as “blood coloured”.
Inhaling sulphur dioxide gas causes victims to choke as their internal soft tissue swells – sulphur dioxide reacts with the moisture in lungs and produces sulphurous acid. The local death rate in Chartres was up by 5% during August and September, with over 40 dead. In Great Britain, the records show that the additional deaths were outdoor workers; the death rate in Bedfordshire, Lincolnshire and the east coast was perhaps two or three times the normal rate. It has been estimated that 23,000 British people died from the poisoning.
The weather became very hot, causing severe thunderstorms with large hailstones that were reported to have killed cattle, until the haze dissipated in the autumn. The winter of 1784 was most severe; Gilbert White at Selborne in Hampshire reported 28 days of continuous frost. The extreme winter is estimated to have caused 8,000 additional deaths in the UK. In the spring thaw, Germany and Central Europe reported severe flood damage.
The meteorological impact of Laki continued, contributing significantly to several years of extreme weather in Europe. In France a sequence of extremes included a surplus harvest in 1785 that caused poverty for rural workers, accompanied by droughts and bad winters and summers, including a violent hailstorm in 1788 that destroyed crops. These events contributed significantly to a build-up of poverty and famine that may have contributed to the French Revolution in 1789. Laki was only one factor in a decade of climatic disruption, as Grímsvötn was erupting from 1783 to 1785, and a 1998 study of El Niño patterns suggests an unusually strong El Niño effect from 1789 to 1793.