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  • Writer's pictureBruce Boyce

Of Volcanoes and Revolution

Updated: May 15, 2022

The Storming of the Bastille by Jean-Pierre Houel

"The peculiar haze, or smokey fog, that prevailed for many weeks in this island, and in every part of Europe, and even beyond its limits, was a most extraordinary appearance, unlike anything known within the memory of man. …..The sun, at noon, looked as blank as a clouded moon, and shed a rust-coloured ferruginous light on the ground."

English Naturalist Gilbert White describing the summer of 1783 (1789)

Major historical events such as the French Revolution occurred because of a complicated series of circumstances that lead up to an inflection point. Often overlooked or understated is the effects of climate and other natural phenomena. Some natural disasters are significant on their own: the San Francisco Earthquake of 1906 or the eruption of Vesuvius that buried Pompeii. More often than not, the impact of natural phenomena such as earthquakes and volcanoes is much more subtle over the long term. One of the underlying causes of the French Revolution was the poverty of the French peasants from food shortages as a result of a series of famines. These famines, precipitated by changes in the weather patterns, could be traced back to an Icelandic volcanic eruption in 1783.

Nowadays we have a clear understanding of how volcanism affects weather and climate patterns: think Krakatoa, Pinatubo, Tambora. In the summer of 1783, Iceland would experience a major volcanic event that would have a profound impact on the global climate for several years. Today it is known as the Laki Fissure Eruption.

A section of the Laki fissure as it looks today.

Iceland is one of the most volcanically active places on the planet. The reason for this is two-fold. Iceland sits upon a boundary where two of Earth's tectonic plates are separating. The divergence of the plates has created what is called a rift zone that runs the entire length of the Atlantic. This rift is known as the Mid-Atlantic Ridge. Most of the rift is hidden by the ocean, but there are spots in Iceland where the rift is exposed. This doesn't mean Iceland is splitting apart, rather Iceland is gaining new territory. Magma extrudes up through the rift and then cools and solidifies building up land on either side. (Hence the ridge that runs parallel to the rift on either side.) Besides being on the rift, Iceland also sits upon what is called a "hot spot". A hot spot is a plume of magma that originates deep within the Earth's mantle. This plume supplies the rift with large quantities of molten material.

Laki is a volcanic vent located in the south-central region of Iceland. It straddles a fissure called Lakagigar ("Craters of Laki"). They are part of a larger volcanic system centered around Grimsvotn, a caldera covered by glacial ice. (Grimsvotn made news in 2011 when it last erupted.) On June 8, 1783, the fissure erupted. Generally speaking, fissure eruptions are less explosive and magma tends to flood out rather than be ejected to great heights. Many of the eruptions that occur at Kilauea, Hawaii are fissure eruptions. The Laki eruption of 1783 was unremarkable in comparison to other volcanic eruptions, but it is noted for the scale of the eruption and its impact. It happened along fifteen miles of the fissure and opened over a hundred separate craters. It started as a steam explosion as hot magma met cold groundwater, but settled into a more effusive flow of lava. (Lava is molten material above ground; magma is molten material below ground.) The eruption, though, would last over eight months until February 1784.

Map of lava flow from Laki eruption

During that time, nearly 4 cubic miles of lava and volcanic fragments called tephra were ejected from the fissure. Lava fountains reached heights between 2000 and 5000 feet. The gases, which would have the most significant impact on the global climate, were carried up to 10 miles into the atmosphere. These gases included an estimated 8 million tons of hydrogen fluoride and 120 million tons of sulfur dioxide. The pastor Jon Steingrimsson was an eyewitness to the eruption and described it this way: "From the smallest holes flames and fire erupted. Great blocks of rocks and pieces of grass were thrown high into the air and in indescribable heights, from time to time strong thunders, flashes', fountains of sand , lightening [?] and dense smoke occurred... Earth trembled incessantly. …how terrible it was to see, such signs of an angry god...[now] it was time to confess to the lord."

The effects on Iceland were devastating. More than 9,000 people died from the lava and the ash. Livestock began dying from fluorine poisoned grasses. Half the cattle population and a quarter of the sheep population was killed off. Sulfur dioxide created acid rain which prevented crops from growing. Even fish in the ocean began to die off. One-third of Iceland's population - an estimated 20,000 people - perished from the resulting famine. It would be the worst disaster in Icelandic history.

Yet Iceland would not be alone in feeling the effects of the eruption. In Europe, during the summer of 1783, contemporaries reported a persistent fog and haze. This was much like the haze produced by the wildfires over much of the Western sections of the United States. The sun appeared blood-red at dawn and dusk and night sky visibility was reduced. The haze was created by the large quantities of sulfur dioxide which gave the air the tell-tale "smelly egg" odor. Like in Iceland, this poisonous fog killed off livestock and crops. There were reports of a sticky substance appearing on plants which was called "honey dew". Plants withered overnight in the Netherlands and Germany. In Great Britain, they would call the summer of 1783 the "sand summer" because of the amount of falling ash. The fog affected people with respiratory ailments and other underlying health issues. The haze was due in part to a strong high-pressure system that settled over the continent. The high-pressure system brought extreme heat to the region on top of the dry fog. Europe would experience a higher than normal mortality rate.

Chichester Canal by J.M.W. Turner

The devastating weather patterns did not end with the summer but continued into the winter of 1783-1784. The winter was cold, with below-normal temperatures, and wet with significant amounts of snow and rain across the continent. Periods of thaw resulted in an increase in snowmelt that led to severe flooding. Flooding damaged bridges, dams, and other structures in Central Europe. Below normal temperatures were not confined to Europe. North America experienced one of its longest and coldest winters on record. New England saw the longest period of below zero temperatures, New Jersey its largest accumulation of snow, and harbors from New York City to New Orleans on the Gulf were frozen over for weeks. The eruption also disrupted the seasonal precipitation and monsoon of Southeast Asia and Africa. This led to long term drought in those regions.

Repairing the Charles Bridge, Prague 1784

The effects of the Laki eruption lingered for several years afterward. Overall global cooling continued. In New England during the winter of 1786-1787, rivers froze over in November 1786 and were not ice-free until March 1787. There was an increase in the frequency and the severity of snowstorms throughout the region. This crippled the shipping and trade as ships were ice-bound for much of the winter. Agriculture in northwest Europe suffered from a shortened growing season. France, in particular, was hit hard. From 1785 to 1789, the country felt the consequences of meteorological extremes: droughts, severe winters, hot, short summers with violent storms. All this help sink the French peasants into famine and poverty.

The French philosopher Voltaire observed that Parisians needed only two things; "comic opera and white bread". There were many factors that led to the French Revolution, but the shortage of bread in 1789 played a significant role in stoking the animosity of the lower classes towards the monarchy. It was the king's job to ensure the food supply, and after the failed harvests of the proceeding years, this was increasingly hard to do. Arthur Young, an Englishman traveling in France, saw the handwriting on the wall. He wrote: “Everything conspires to render the present period in France critical; the want of bread is terrible; accounts arrive every moment from the provinces of riots and disturbances, and calling in the military, to preserve the peace of the markets.” The storming of the Bastille on July 14, 1789, was as much about finding grain as it was about finding weapons or freeing prisoners.

Would the French Revolution have happened regardless? It is an interesting "what if" exercise. Certainly, the food shortages and poverty as a result of years of poor harvests resulted in the violent uprising of the lower classes. Had these conditions not been exacerbated by the changes in the weather patterns from the Laki eruption, it is reasonable to make the argument that the Revolution would have taken on a different character. Reforms aimed at many of the monarchy's shortcomings were already being debated or implemented. France might have been able to transition peacefully towards a constitutional monarchy such as seen in England. It is also possible that the revolt would have been delayed, been less violent, and not subsequently lead to Napoleon. Regardless, an argument can be made that the events leading up to the revolution were in some small part hinged upon the drastic changes in weather from an Icelandic volcanic eruption.


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